Communications

Description

Ground Command Interface Logic

S-Band Phase Modulation

S-Band Forward Link

S-Band PM System Interface and Data Flow

S-Band Return Link

Department of Defense Links

S-Band PM Power Modes

S-BAND PM MODE Rotary Switch on Panel A1L

S-Band PM Antennas

S-Band PM Antenna Locations

S-Band PM Antenna Locations Diagram

S-Band PM System Switches on Panel C3

OPS 201 ANTENNA Display

COMM/RCDR (DISP 76) Display

Preamplifiers

S-Band PM ANT SW ELEC, PRE AMPL, PWR AMPL, and XPNDER Switches on Panel A1L

Power Amplifiers

Transponders

DCAMPS/SIG STR Meter and Rotary Switch on Panel F9

SIGNAL STRENGTH Indicator and Switch on Panel A1U

Network Signal Processors

Communications Security

NSP ENCRYPTION Switch Modes

S-Band FM Switches on Panel A1R

S-Band Frequency Modulation

S-Band FM Antennas

S-Band FM Antenna Locations

S-Band FM System Block Diagram

Ku-Band Communications System

Ku-Band System

Ku-Band Antenna Non-Coverage Zones

KU-BAND Controls on Panel A1L

Ku-Band Deployed Assembly

Ku-Band Deployed Assembly Diagram

KU-BAND Circuit Breakers on Panel R15

Ku-Band Antenna Deployment and Stowage

KU ANTENNA Switches and Talkback on Panel R13L

PYRO JETT KU Circuit Breakers on Panel ML86B

KU ANT Switches on Panel A14

Ku-Band Antenna Jettison Separation

Ku-Band Rendezvous Radar

Payload Communication System

S-Band PAYLOAD Switches on Panel A1L

PCMMU/PL COMM Display (SPEC 62)

Payload Interrogator

Payload Signal Processor

Communication Interface Unit

Payload Data Interleaver

COMMUNICATION INTERFACE UNIT Controls on Panel L11

Ultrahigh Frequency System

UHF Subsystem Functional Block Diagram

UHF System Controls on Panel 06

UHF Controls on Panel A1R

Audio Distribution System

Audio Loops and System Interface

Audio Central Control Unit

AUDIO CENTER Selection Switch on Panel C3

Commander's Audio Terminal Unit of Panel 05

Audio Terminal Unit on Panel AW18D

Audio Terminal Units

Pilot's Audio Terminal Unit on Panel O9

Audio Terminal Unit on Panel R10

Audio Terminal Unit on Panel L9

Audio Terminal Unit on Panel A13 (OV-102)

MS AUDIO CONTROL Switch on Panel R11L

Speaker Unit on Panels A2 and M02J

Speaker Units

Audio Center Panel

AUDIO CENTER Controls on Panel A1R

Loose Communications Equipment

Launch and Entry Helmets

Headset Interface Unit

Headset Interface Unit Image

Crewman Communications Umbilical on Panel L5

Cables

Multiple Headset Adapter

Wireless Communications Units

Very Lightweight Headset

Very Lightweight Headset Image

Handheld Microphone

Instrumentation

Simplified Instrumentation Data Flow

Operational Instrumentation System Overview

OI System

Dedicated Signal Conditioners

Multiplexer/Demultiplexers (MDMs)

Pulse Code Modulation Master Unit (PCMMU)

OI PCMMU Controls on Panel C3

Master Timing Unit

Recorder Controls on Panel A1R

Operations Recorders

Payload Recorder

Thermal Impulse Printer System

Communications System Summary

Comm S-Band PM Table

S-Band System 1 Power

Panel A1L

Panel A1R

Panel A1U

Panel A2

Panel A13

Panel A13 (OV102 Only)

Panel M029J

Panel 05

OPS 201 ANTENNA Display

COMM/RCDR (DISP 76) Display

PCMMU/PL COMM Display (SPEC 62)

Communications System Rules of Thumb

 

Description

The orbiter communication system transfers the following types of information:

This information is transferred through hardline and radio frequency (RF) links. Hardline refers to wires that connect communicating devices, and RF refers to radio signals. RF communication takes place directly with the ground or through a tracking and data relay satellite (TDRS).

Direct communication for NASA missions takes place through space flight tracking and data network (STDN) ground stations. For military missions, Air Force Satellite Control Facility (AFSCF) remote tracking station sites, also known as space-ground link system (SGLS) ground stations, are used. Direct signals from the ground to the orbiter are referred to as uplinks (UL), and signals from the orbiter to the ground are called downlinks (DL).

TDRS communication takes place through the White Sands Ground Terminal (WSGT). These indirect signals from the TDRS to the orbiter are referred to as forward links (FL), and the signal from the orbiter to the TDRS is called the return link (RL). Communication with a detached payload from the orbiter is also referred to as forward link, and return link is the signal from the payload to the orbiter.

The orbiter communication system is divided into several smaller systems: S-band phase modulation (PM), S-band frequency modulation (FM), Ku-band, ultrahigh frequency (UHF), payload communications, audio, and closed-circuit television. (CCTV is discussed separately in Section 2.3.) The S-band FM, S-band PM, Ku-band, and UHF systems are used to transfer information between the orbiter and the ground. The payload communication system is used to transfer information between the orbiter and its payloads either through hardline or RF links. The audio systems transfer voice communications throughout the orbiter, and the closed-circuit television system is used for visually monitoring and recording activities. The ground command interface logic (GCIL), also referred to as the ground command interface logic controller, controls selected functions of the S-band PM, S-band FM, Ku-band, payload communication, and CCTV systems. Commands are sent to the orbiter from the ground through S-band system uplink or Kuband system forward link. All commands, whether sent on S-band or Ku-band, are routed to the onboard GPC through the network signal processor (NSP) and associated FF MDM. The GCIL takes commands for these systems from the GPC via the PF MDMs, for ground commands or from the appropriate panel for crew control.

With the exception of audio and UHF, each of the communications systems has an associated CONTROL switch with the positions PANEL and CMD. When the switch is set to PANEL, the system can be accessed by the crew using panel switches. When the switch is set to CMD, control is by ground command via GCIL. The locations and operations of these switches are provided in the individual communications systems discussions that follow.

Ground Command Interface Logic

Ground Command Interface Logic 

 

NOTE

Because of the large number of distinct elements of the Communications system, a separate Operations subsection is not included. That information is provided within the separate element discussions.

S-Band Phase Modulation

The S-band PM system provides two-way communication between the orbiter and the ground, either directly or through a relay satellite. It provides communication channels for five functions:

A characteristic of RF signals in the S-band range is that "line-of-sight" must exist between transmitting and receiving antennas to permit communications. With the availability of the east and west TDRS, potential total S-band PM support time using direct and relay links will be as much as 80 percent of mission time. (For some missions, vehicle attitude constraints imposed by experiment requirements may cause the loss of portions of that potential support time because the required orbiter attitudes may at times be incompatible with orbiter S-band PM quad antenna patterns.)

A fully operational TDRS system provides east and west satellites that are both supported by the WSGT facility. The east and west satellites are approximately 130° apart in geosynchronous orbits. In the S-band mode, the TDRS single access antenna is gimballed but does not automatically track the orbiter. It is sequentially commanded by the ground to follow the orbiter position. There is a zone of exclusion (ZOE) where the orbiter, operating at normal altitudes, will not be in line-of-sight with either satellite. The ZOE is geographically over the Indian Ocean region.

S-Band Forward Link

The S-band forward link operates through the STDN or TDRS. It is phase modulated on a center carrier frequency of either 2,106.4 MHz (primary) or 2,041.9 MHz (secondary) for NASA. The two frequencies would prevent interference if two users were in operation at the same time and place, since one user could select the high frequency, and the other could select the low frequency.

S-Band PM System Interface and Data Flow

S-Band PM System Interfaces and Data Flow

 

The forward link originates from Mission Control through the NASA STDN ground stations used for launch, lift-off, ascent, or landing, or through the WSGT via the TDRS system to the orbiter. The high data rate is 72 kilobits per second, consisting of two air-to-ground voice channels at 32 kbps each and one command channel at 8 kbps, two-way Doppler, and two-way tone ranging. The low data rate is 32 kbps, consisting of one air-to-ground voice channel at 24 kbps and one command channel of 8 kbps, two-way Doppler, and two-way ranging. The two-way ranging does not operate through the TDRS.

S-Band Return Link

The S-band return link operates through the STDN or TDRS. It is phase modulated on a center carrier frequency of 2,287.5 MHz (primary) or 2,217.5 MHz (secondary) for NASA. The two frequencies prevent interference if two users are in operation at the same time and place.

The S-band PM return link can originate from one of two S-band PM transponders aboard the orbiter, each of which can use one frequency, but not both at the same time. The link transmits the data through the NASA STDN ground stations used for launch, lift-off, ascent, or landing, or through the TDRS and TDRS system via the WSGT to Mission Control.

The high data rate of 192 kbps consists of two air-to-ground voice channels at 32 kbps each and one telemetry link of 128 kbps, two-way Doppler, and two-way ranging. The two-way Doppler and two-way ranging are operative only when in view of the NASA STDN ground stations at launch, lift-off, ascent, or landing. The two-way ranging does not operate with the TDRS.

The S-band return link low data rate of 96 kbps consists of one air-to-ground voice channel at 32 kbps and one telemetry link at 64 kbps, two-way Doppler, and two-way ranging. As noted, the two-way Doppler and two-way ranging are used in the same manner as in the high-data rate mode.

Department of Defense Links

The Department of Defense S-band forward link is phase modulated on a center carrier frequency of either 1,831.8 MHz (primary) or 1,775.5 MHz (secondary) from the Air Force Satellite Control Facility (AFSCF) through its own ground stations (SGLS ground stations). It does not operate through the TDRS because the S-band power amplifiers are not powered in the SGLS mode.

The Department of Defense S-band return link is phase modulated on a center carrier frequency of 2,287.5 MHz (primary) or 2,217.5 MHz (secondary) through the SGLS mode to the AFSCF ground stations, and also does not operate through the TDRS. The two S-band return link frequencies also would prevent interference if two users were in operation at the same time.

S-Band PM Power Modes

S-band PM power modes are selected using the S-BAND PM MODE rotary switch on panel A1L. Selectable modes are SGLS, STDN LO and HI, and TDRS DATA and RNG (TDRS RNG is not used). In high power modes (TDRS and STDN HI) incoming (received) signals from a quad-selected antenna are directed through a preamplifier before reaching the transponder. Outgoing (transmit) signals are routed through a power amplifier and the preamplifier assembly diplexer after leaving the transponder en route to an antenna. In low power modes (STDN LO and SGLS), incoming signals flow from the antenna directly to the transponder, and outgoing signals go directly from the transponder to the selected antenna without amplification.

Four quadrant S-band PM antennas covered with a reusable thermal protection system are located approximately 90° apart on the forward fuselage outer skin of the orbiter. On the flight deck viewed through the forward windows, the quadrant antennas are to the upper right, lower right, lower left, and upper left. These antennas are the radiating elements for transmitting the S-band PM return link and for receiving the S-band PM forward link. Each quad antenna is a dual-beam unit that can "look" forward or aft for both transmission and reception without any physical movement, effectively creating eight antennas for the S-band PM system. These antenna are controlled by the antenna switch electronics via GCIL. Crew switch for S-band PM ANT SW ELEC is on A1L.

S-BAND PM MODE Rotary Switch on Panel A1L

S-BAND PM MODE Rotary Switch

 

S-Band PM Antennas

The antenna is selected automatically under GPC control, by real-time command from the ground, or manually by the flight crew using the S-BAND PM ANTENNA rotary switch on panel C3. When the switch is set to GPC, antenna selection is automatic, and the antenna switching commands are sent to the switch assembly through the payload multiplexers/demultiplexers (PF MDMs). Other positions selectable by the switch are LL FWD (lower left forward), LL AFT (lower left aft), UL FWD (upper left forward), UL AFT (upper left aft), UR FWD (upper right forward), UR AFT (upper right aft), LR FWD (lower right forward), and LR AFT (lower right aft). Antenna selection is based on the computed line of sight to the NASA STDN ground station, the AFSCF ground station, or the TDRS in view, depending on the orbiter communication mode. The current antenna selection is shown on the OPS 201.

S-Band PM Antenna Locations Diagram

 

S-Band PM Antenna Locations 

 

S-Band PM Antenna Locations

ANTENNA display. Also on the display are related items such as the S-band ground station in view, TDRS in line of sight, and whether GPC antenna selection is enabled or inhibited. Also displayed is the antenna electronics unit performing antenna selections.

GPC control can be inhibited to permit ground control to select an antenna other than the one currently selected by the GPC. The ground sends a command load to inhibit GPC control and a real-time command (RTC) to select the desired antenna. GPC control is restored by sending a load to enable the GPC mode. The crew can perform the same functions by selecting the ANTENNA display, executing Item 18 (GPC INH), and then selecting the desired antenna by RTC via keyboard. Using GPC OVRD (item 19), the crew can force the S-band antenna management software to the S-band PM upper right quadrant Top S-band PM upper left quadrant Upper left antenna looking forward Bottom Lower right antenna looking aft S-band PM lower left quadrant 128.cvs S Band PM lower right quadrant TDRS mode. An asterisk will be displayed by item 19 while GPC override is in effect. To restore GPC control, item 17 (GPC ENA) is executed.

S-Band PM System Switches on Panel C3

S-BAND PM System Switches on Panel C3

 

Other S-band PM fields on the ANTENNA  display allow prime selection of a TDRS west or east, items 13 and 14, respectively. These items select the chosen TDRS as prime; if this TDRS is not in view, it selects the other TDRS. If both are in view, the prime is selected. No change is made to TDRS selection if neither is in view. Similar logic holds true for Ku-band system, items 10 and 11.

OPS 201 ANTENNA Display

OPS 201 ANTENNA Display 

 

COMM/RCDR (DISP 76) Display

COMM/RCDR (DISP 76) Display

COMM/RCDR (DISP 76) Display

Preamplifiers

The dual S-band preamplifier is used in the TDRS and STDN HI modes for amplification. In TDRS mode, the preamplifier is required fulltime for the forward link radio frequency because of the much greater distance and, consequently, lower strength signal from the TDRS to the orbiter (minimum of about 22,300 miles) than from the STDN to the orbiter (typically, slant ranges are in the low hundreds of miles). The preamplifier is not used in the SGLS or STDN LO modes. One of the two units is used at a time, and the output of either unit can be cross-strapped to feed either transponder. The preamplifier provides an RF gain of about 25 decibels.

S-Band PM ANT SW ELEC, PRE AMPL, PWR AMPL, and XPNDER Switches on Panel A1L

S-BAND PM ANT SW ELEC, PRE AMPL,PWR AMPL, and XPNDR Switches on PanelA1L 

S-Band PM ANT SW ELEC, PRE AMPL, PWR AMPL, and XPNDER Switches on Panel A1L

The PRE AMPL control switches are on panel A1L; this function is generally under ground control. If the S-BAND PM CONTROL switch on panel C3 is set to PANEL, preamp 1 or 2 is selected, depending on the position of the SBAND PM PRE AMPL switch on panel A1L. The COMM/RCDR display (DISP 76) under SM OPS 201 shows preamp status and frequency configuration (PREAMP and FREQ).

Power Amplifiers

The S-band power amplifiers provide selectable amplification of transponder RF output for STDN HI and TDRS operational modes. The nominal power gain is about 17 decibels. There are two power amplifiers; one is used at a time, and the input of either can be cross-strapped with the output of either transponder. The output of the power amplifiers can also be routed through either frequency diplexer in the preamp assembly.

The power amplifiers use a traveling wave tube, which has a filament that must be warmed up before high voltage is applied to the tube. A 140-second timer provides the delay when the OPERATE mode is selected from a cold start. With the system in STANDBY, the filament is kept heated, ready for "instant on" operation.

The PWR AMPL STANDBY and OPERATE switches are on panel A1L; these functions are generally under ground control. If the S-BAND PM CONTROL switch on panel C3 is set to PANEL, the switches on panel A1L establish power amplifier configuration.

NOTE

Both the PWR AMPL STANDBY and OPERATE switches should be in the same position to avoid a reset of the 140-second timer when the standby system is selected.

The COMM/RCDR display, DISP 76, also shows power amplifier status (PWR AMPL OPER, STBY, and PWR OUT and TEMP).

Transponders

Two identical S-band PM transponders function as multipurpose, multimode transmitter/receivers. The transponder can simultaneously transmit and receive, transmit only, or receive only. Only one transponder operates at one time; the other is a redundant backup. The selected transponder transfers the forward link commands and voice to the network signal processor and receives the return link telemetry and voice from the network signal processor.

The transponders may be cross-strapped. Transponder 1 or 2 may be used with network signal processor 1 or 2. The radio frequency sections of either transponder can be used with either preamplifier and power amplifier 1 or 2. The selected transponders also provide a coherent turnaround of the PM forward link and PM return two-way Doppler and two-way tone ranging signals. The two-way Doppler and two-way ranging signals are operative when the orbiter is in view of the NASA STDN ground stations at launch, lift-off, ascent, or landing, or when it is in view of SGLS mode ground stations. The two-way Doppler operates through the TDRS, but the two-way ranging does not.

Two-way Doppler is used by ground stations to track the orbiter. The S-band PM forward and return links are directly proportional to the forward link frequency (two-way Doppler). The S-band transponder provides a coherent turnaround of the forward link carrier frequency necessary for the two-way Doppler data. The transponder operates only when in view of the NASA STDN ground stations during launch, lift-off, ascent, or landing, or in view of SGLS mode ground stations. By measuring the forward link and using return link frequencies expected from the orbiter, the ground tracking station can measure the double Doppler shift that takes place and can calculate the radial velocity (range rate) of the orbiter with respect to the ground station. Because these links are PM, the S-band carrier center frequency is not affected by the modulating wave. It would be impossible to obtain valid Doppler data of the S-band carrier center frequency if it were affected by the modulating technique.

The S-band transponder also provides a subcarrier for two-way tone ranging. The transponder is used to determine slant range from a known point to the orbiter and operates only when in view of the NASA STDN ground stations during launch, lift-off, ascent, or landing, or in view of SGLS mode ground stations. This capability does not operate through the TDRS. The ground station forward links ranging tones at 1.7 MHz and computes vehicle slant range from the time delay in receiving the return link 1.7-MHz tones to determine the orbiter's range. The orbiter's azimuth is determined from the ground station antenna angles.

A C-band skin-tracking mode also is provided from the ground station to track the orbiter and, again, is used only in view of the NASA STDN ground station associated with launch, lift-off, ascent or landing, or in view of SGLS mode ground stations. This capability does not operate through the TDRS. The S-BAND PM XPNDR switch is located on panel A1L; this function is generally handled by ground command via the GCIL. If the S-BAND PM CONTROL switch on panel C3 is set to PANEL, the XPNDR selection is made from panel A1L.

The COMM/RCDR display, DISP 76 in OPS 201, gives transponder status (XPND and MODE). The OPS 201 ANTENNA display also shows the mode for active transponders. Received S-band PM RF signal strength is shown on the DC AMPS/SIG STR meter on panel F9 when the rotary switch below the meter is set to SIGNAL STRENGTH, and on the SIGNAL STRENGTH indicator on panel A1U when the switch to the left of the indicator is set to S-BAND PM. Signal strength is also shown on the OPS 201 ANTENNA DISPLAY (SIG STR); however, during launch and landing, the display is not available.

NOTE

The panels F9 and A1U signal strength indications come from the transponder receiver, whereas OPS 201 ANTENNA display signal strength comes from OI MDM OF3 data.

DCAMPS/SIG STR Meter and Rotary Switch on Panel F9

DCAMPS/SIG STR Meter and Rotary Switch

 

SIGNAL STRENGTH Indicator and Switch on Panel A1U

 

SIGNAL STRENGTH Indicator and Switch

Network Signal Processors

The two onboard network signal processors (NSPs) receive commands (forward link) and transmit telemetry data (return link) to the selected S-band transponder. Only one signal processor operates at a time; the other provides a redundant backup. The selected processor receives one or two analog voice channels from the onboard audio central control unit, depending on whether one (in the low-data-rate mode) or both (in the high-data-rate mode) of the air-to-ground channels are being used. Both voice channels are down-linked only if the NSP is high data rate on both forward and return links. It converts them to digital voice signals, time-division-multiplexes them with the telemetry from the pulse code modulation master unit, and sends the composite signal to the S-band PM transponder for transmission on the return link. On the forward S-band PM link, the NSP does just the reverse. It receives the  composite signal from the S-band transponder and outputs it as either one or two analog voice signals to the audio central control unit. The composite signal from the S-band transponder and outputs it as either one or two analog voice signals to the audio central control unit. The composite forward link also has ground commands that the NSP decodes and sends through the FF MDMs (nominally NSP 1 to FF 1 and NSP 2 to FF 3) to the onboard computers, which route the commands to the intended onboard systems. The NSP data routing/processing modes are controlled by the NETWORK SIG PROC switches on panel A1L.

NOTE

The NSP can also route return link (telemetry and voice) and receive forward link (commands and voice) via the Kuband system.

Communications Security

Communications security (COMSEC) equipment provides the capability for encryption/decryption of operational data aboard the orbiter. The COMSEC equipment works with the NSPs to provide selectable transmit, receive, and record combinations under NSP mode control.

The NSP routes data of the indicated type through the COMSEC encryptor or decryptor as appropriate if "ENC" and gets the data back from the COMSEC line-replaceable unit encrypted/decrypted; if "CLR", the indicated data are handled directly by the NSP, and the COMSEC is bypassed.

The three ENCRYPTION switches on panel A1L provide power and routing control for encrypted data through the NSP.

NSP ENCRYPTION Switch Modes

NSP ENCRYPTION Switch MODES

S-Band FM Switches on Panel A1R

S-BAND FM Switches on Panel A1R 

 

S-Band Frequency Modulation

The S-band FM system cannot receive information; it is used to downlink data from up to seven different sources, one at a time, directly to the ground when there is a line of sight between the orbiter and STDN or Air Force ground stations. The S-band FM return link can originate from two S-band transmitters aboard the orbiter. Both transmitters are tuned to 2,250 MHz. The S-band FM return link can be transmitted simultaneously with the S-band PM return link to the STDN ground station or Mission Control or to the Air Force ground station. The S-band FM return link does not operate through the TDRS system.

Controls for the S-band FM system are on panel A1R. Status and configuration control of the S-band FM system electronic elements can be selected either by panel switches or GCIL, depending on whether the CONTROL switch is set to COMMAND or PANEL. Set to PANEL, the switches allow rotary switch selection of the DATA SOURCE, and FM Power 1, Off, or 2.

The FM signal processor is commanded to select one of seven sources for output to the S-band FM transmitter, which transmits it to the S-band FM return link through the STDN ground station used for launch, lift-off, ascent, or landing, or the DOD AFSCF ground station. Depending on the setting of the DATA SOURCE switch, the S-band FM return link transfers:

Only one of the two FM signal processors is used at a time. FM signal processor 1 interfaces with FM transmitter 1, and FM signal processor 2 interfaces with FM transmitter 2. The transmitters and processors cannot be cross-strapped.

S-Band FM Antennas

Two hemispherical S-band FM antennas covered with a reusable thermal protection system are located on the forward fuselage outer skin of the orbiter approximately 180° apart. On the flight deck, the hemispherical antennas are above the head (upper) and below the feet (lower) and radiate the S-band FM return link.

The S-band antenna switch assembly provides the signal switching among the two S-band FM transmitters and either of the two hemispherical antennas. The proper antenna is selected automatically by onboard or real-time command from the ground, computer control, or manual flight crew selection using the S-BAND FM XMTR UPPER, RCVR LOWER switch on panel A1R. In the GPC mode, the onboard SM computer selects the proper hemispherical antenna to be used whenever an S-band FM transmitter is active. The antenna selection is based on the computed line of sight to the NASA STDN ground station used for launch, lift-off, ascent, or landing, or the AFSCF ground stations.

The basic difference between the quadrant and hemispherical antennas is that the hemispherical antennas have a larger beamwidth, whereas the quadrant antennas have a higher antenna gain. The hemispherical antennas are so named because there are two of them, one on the top of the orbiter and one on the bottom.

The hemi antenna switch has a port that can route RF television from the astronaut's extravehicular mobility unit (EMU) to the orbiter's closed-circuit television system. An extravehicular mobility TV unit can transmit television on one hemi antenna/antenna switch path to the orbiter while the S-band FM system is routing FM downlink telemetry to ground on the other hemi antenna/antenna switch path. This requires an EMU TV receiver that is manifested for specific flights.

S-Band FM Antenna Locations

S-Band FM Antenna Locations

S-Band FM System Block Diagram

S-Band FM System Block Diagram

 

Ku-Band Communications System

Ku-Band Communications System

 

Ku-Band System

The Ku-band system operates between 15,250 MHz and 17,250 MHz. The Ku-band carrier frequencies are 13,755 GHz from the TDRS to the orbiter and 15,003 GHz from the orbiter to the TDRS. The Ku-band antenna is located in the payload bay. After the payload bay doors are opened, the Ku-band antenna is deployed. Once the antenna is deployed, the system can be used to transmit information to and receive information from the ground through the TDRS. The Ku-band antenna can also be used as a radar system for target tracking objects in space, but it cannot be used simultaneously for Ku-band communications and radar operations.

When the Ku-band antenna is deployed and activated in the communications mode, the NSP directs the return link data stream to both the Ku-band signal processor and the S-band transponder. The forward link is only accepted by the NSP from the Ku-band signal processor or the S-band transponder. This depends on whether S-band or Ku-band has been selected through GCIL, by the ground, or by the NSP UPLINK DATA switch on panel A1L. For Ku-band, the return link data stream from the network signal processor is directed through the Ku-band signal processor and antenna to the TDRS in view, via the TDRS and DOMSAT systems, to Mission Control. The process is reversed for the Ku-band forward link. If the Ku-band forward link is lost, and the ground has enabled the fail-safe, the system reverts to S-band PM uplink mode. It is possible to run the downlink through the Ku-band and the forward link through the S-band, and vice versa.

The Ku-band system return link consists of channel 1, modes 1 and 2, plus one channel 2, modes 1 and 2, and one channel 3. Channel 1, modes 1 and 2, consists of 192 kbps of operational data (128 kbps of operational data telemetry and payload interleaver plus two air-to-ground voice links at 32 kbps each) plus one of the following selections from channel 2, modes 1 and 2: (1) payload digital data from 16 kbps to 2 Mbps, (2) payload digital data from 16 kbps to 2 Mbps, (3) operations recorder playback from 60 kbps to 1,024 kbps, or (4) payload recorder playback from 25.5 kbps to 1,024 kbps. It also includes one of the following from channel 3: mode 1 attached payload digital data (real-time or playback) from 2 Mbps to 50 Mbps, mode 2 television (color or black and white) composite video, or mode 2 real-time attached payload digital data or payload analog data.

Ku-Band Antenna Non-Coverage Zones

Ku-Band Antenna Non-Coverage Zones 

Ku-Band Deployed Assembly Location

Ku-Band Deployed Assembly Location

 

KU-BAND Controls on Panel A1L

 

KU-BAND Controls on Panel A1L 

The Ku-band system forward link consists of a mode 1 and 2 through the TDRS in view. Mode 1 consists of 72-kbps data (two air-to-ground voice streams at 32 kbps each and 8 kbps of command), 128-kbps thermal impulse printer system (TIPS), and 16-kbps synchronization. Mode 2 consists of 72-kbps operational data (two air-to-ground voice streams at 32 kbps each and 8 kbps of command).

The Ku-band system can handle greater quantities of data than the S-band systems. It transmits three channels of data, one of which is the same interleaved voice and telemetry processed by the S-band PM system. Two of the seven possible sources of information sent on the other two channels are: payload analog, payload digital, payload interleaver bent-pipe, payload recorder, operations recorders, television, and Spacelab (if flown). Data sources are selectable by two KU SIG PROC rotary switches on panel A1U, one for HIGH DATA RATE and one for LOW DATA RATE.

The three channels of data are sent to the Ku-band signal processor to be interleaved. This signal then goes to the onboard deployed electronics assembly, which contains the transmitter, to be transmitted to the TDRS through the Ku-band antenna. Three modes can be selected by the MODE switch on panel A1U. In the COMM (communications) mode, incoming signals go through an internal electronics assembly (EA1) to the Ku-band signal processor, which processes and routes Ku-band data. Voice and commands are sent to the network signal processor.

A separate output from the Ku-band signal processor is directed to the TIPS or the payload system if the Ku-band uplink is in the high data rate mode. In the RDR COOP and RDR PASSIVE modes, incoming signals are routed from the deployed electronics assembly to EA2, the radar signal processor. The signal is processed to provide target angle, angle rate, range, and range rateinformation. This status information is then routed to EA1 to be used for target tracking.

Ku-Band Deployed Assembly

The Ku-band deployed assembly provides the interface with the TDRS when there is a line of sight between the orbiter and TDRS. The assembly is mounted on the starboard sill longer on in the payload bay. The deployed assembly consists of a two-axis, gimbal mounted, high-gain antenna, an integral gyro assembly, and a radio frequency electronics box.

The gimbal motors position the Ku-band antenna, and rate sensors determine how fast the antenna is moving. The Ku-band deployed antenna assembly is 7 feet long and 1 foot wide when stowed in the payload bay. The graphite epoxy parabolic antenna dish is 3 feet in diameter. The deployed antenna assembly weighs 180 pounds. The weight of the entire system is 304 pounds.

Ku-Band Deployed Assembly

Ku-Band Deployed Assembly

KU-BAND Circuit Breakers on Panel R15

KU-BAND Circuit Breakers on Panel R15

The antenna dish is edge-mounted on a two-axis gimbal. The alpha gimbal provides a 360-degree roll movement around the pole or axis of the gimbal. The beta gimbal provides a 162-degree pitch movement around its axis. The alpha gimbal has a stop at the lower part of its movement to prevent wraparound of the beta gimbal control cable. Since the beta gimbal has only a 162-degree movement, there is a 4-degree non-coverage zone outboard around the pole and a 32-degree non-coverage zone toward the payload bay.

The antenna can be steered in several selectable modes under manual control by the flight crew using panel A1U or automatically by the SM software. The KU BAND CONTROL switch on panel A1U selects COMMAND (control by GCIL or keyboard commands) or PANEL (crew control by panel switches and selectors). With the switch in PANEL, the antenna steering mode can be selected using the rotary switch on the left side of the panel. The switch positions are GPC (GPC pointing and auto track), GPC DESIG (GPC pointing only), AUTO TRACK (manual pointing and auto track), and MAN SLEW (manual pointing only).

At times, the Ku-band system, in view of a TDRS, is interrupted because the orbiter blocks the Ku-band antenna's view to the TDRS or because orbiter attitude requirements or payloads' radiation sensitivities prohibit its use.

In addition, the Ku-band antenna beta cabling may periodically require positioning to ensure that it does not become twisted in a way that could cause the antenna to bind. When the Ku transmitter is enabled and outputting an RF carrier and when it is inhibited, the ground can control via ground uplink command to the SM GPC and Ku system. This control is called Ku antenna "masking." These masking modes are used to provide protection from Ku radiation for payloads and for crewmembers during EVAs and certain payload operations. The types of masking, commandable from the ground, include: 1) inhibiting the Ku transmitter when a specified beta gimbal angle is exceeded (beta MASK) or when both a specified beta gimbal angle and the orbiter hardware obscuration zone are exceeded (beta +MASK), 2) specifying an EVA protection zone, where the transmitter is disabled, within certain elevation and azimuth angle pointing of the antenna relative to a coordinate system, based on the orbiter's X, Y, and Z axes. New Ku software also modes the Ku system to standby mode, if the antenna remains near the beta stops for a certain period of time, to prevent excessive antenna gimballing and cable binding.

None of these masking modes is readily evident to the crew unless they monitor RF out power on SM GPC SPEC 76. Only the orbiter hardware obscuration zone is shown on the SM ANTENNA SPEC (see ANTENNA display on page 2.4-6).

Ku-Band Antenna Deployment and Stowage

When the shutle reaches orbit, before the Kuband antenna is deployed, the KU ANT HTR circuit breaker on panel R15 is closed to energize thermostatically controlled heaters for the deployed electronics assembly, gimbals, and antenna assembly. During Ku-band activation, the KU ELEC and KU SIG PROC circuit breakers on panel R15 are closed. (There is also a CABLE HTR circuit breaker on panel R15. The Ku-band system was originally designed to have a cable heater, but it was never installed. Therefore, this circuit breaker is always left open.) These circuit breakers provide electrical power to the Ku-band electronic elements, electronics assemblies 1 and 2, the signal processor assembly, and Ku-band portions of panels A1U and A2. Actual deployment involves the KU ANTENNA controls and associated talkback on panel R13L. The antenna is locked in the stowed position to clear the adjacent payload bay doors and radiators when they are closed or moving.

Twenty-three seconds are normally required to deploy or stow the assembly. In the deployed position, the assembly forms a 67-degree angle with the orbiter X axis. Activating the Kuelectronics and taking the KU BAND POWER switch on panel A1U to ON frees the antenna gimbals by removing the gimbal locking pins. The beginning of stow operations contains approximately 30 seconds of gimbal lock sequencing before assembly stow begins.

The Ku-band antenna must be stowed before the orbiter payload bay doors are closed in preparation for entry. This is done by setting the KU ANTENNA three-position switch on panel R13L to the STOW position. If the assembly does not respond to normal stow operations, the KU ANTENNA DIRECT STOW switch on panel R13L is used. Setting this switch to ON bypasses the normal stow control sequences and causes the assembly to be driven inside the payload bay. The KU ANTENNA DIRECT STOW switch procedure is only used if locking of the alpha and beta antenna gimbals is successful in their stow position, because entry with antenna gimbals unlocked may cause unacceptable damage. DIRECT STOW merely positions the entire deployed assembly inside the payload bay and does not affect gimbal locking.

If neither the normal stow nor the DIRECT STOW can position the assembly inside the payload bay, the assembly can be jettisoned. To jettison the deployed assembly, the crew closes the MN A and MN C PYRO JETT SYS A and SYS B KU ANT circuit breakers on panel ML86B to provide redundant jettison power. The crew then activates the PYRO KU ANT ARM and JETT switches on panel A14, which causes a guillotine to cut the cables to the deployed assembly and releases a clamp holding it to the pivot assembly. The separation point is between the assembly and deployment mechanism about 20 inches above the sill longer on. No ejective force is imparted; the assembly is merely cut loose, and the orbiter maneuvers away from it. The jettison operation takes approximately 4 seconds.

KU ANTENNA Switches and Talkback on Panel R13L

KU ANTENNA Switches and Talkback on Panel R13L

PYRO JETT KU Circuit Breakers on Panel ML86B

PYRO JETT KU Circuit Breakers on Panel ML86B

KU ANT Switches on Panel A14

KU ANT Switches on Panel A14

Ku-Band Antenna Jettison Seperation

Ku-Band Antenna Jettison Separation

Ku-Band Rendezvous Radar

The orbiter Ku-band system includes a rendezvous radar that skin-tracks satellites or payloads in orbit. For large payloads that must be carried into orbit one section at a time, the orbiter will rendezvous with the payload segment currently in orbit to add on the next section. The gimballing of the Ku-band antenna permits it to conduct a radar search for space hardware. The Ku-band system is first given the general location of the hardware by the orbiter computer; then the antenna makes a spiral scan of the area to pinpoint the target (in GPC mode).

Radar may also be used to search for space hardware using a wide spiral scan of up to 60°. Objects may be detected by reflecting the radar beam off the surface of the target (RDR PASSIVE MODE) or by using the radar to trigger a transponder beacon on the target (RDR COOP MODE). These modes are selectable using the KU BAND MODE switch on panel A1U. To date, only RDR PASSIVE MODE has been used.

During a rendezvous operation, the radar system is used as a sensor that provides target angle, angle rate, and range rate information for updating the rendezvous navigation data in the GNC computer. The operation is similar to using the crew optical alignment sight or star trackers, except that the radar provides range data in addition to angle data. Angle tracking maintains appropriate antenna pointing to keep the target within the antenna beam. Range tracking is accomplished by electronically measuring the time between a transmitted pulse and a return pulse from the target. The return pulse may be reflected from a passive (skin-tracked) target or cooperative target transmitter that is triggered by the radar-initiated pulse. The latter provides a longer range capability.

Angle tracking can be accomplished in two ways: computer or manual designations or automatic (auto) servo. During manual or computer-designated tracking, the antenna beam angle is positioned by services external to the Ku-band system. Computer tracking (used in GPC and GPC DESIG modes) provides designated angle data based on combined target and orbiter state vector information. Manual tracking (used in MAN SLEW and AUTO TRACK modes) applies manually initiated rates to the antenna control system from switches at the orbiter aft flight deck station (A1U).

Automatic angle tracking applies error rates to the antenna control system from a receiving station that measures the target position relative to the antenna beam center. This closed-loop servo-system, internal to the Ku-band system, ignores external computer or manual designations. It is the only angle tracking mode that provides angle data for updating navigation data.

Range tracking is always automatic, although computer-designated ranges are applied to the Ku-band system until automatic tracking is achieved. In the automatic tracking mode, the Ku-band system provides actual antenna angle, angle rate, range, and range rate data through an MDM for rendezvous and proximity operations. Data routed to the indicators on panel A2 represent hard-wired azimuth, elevation, range, and range rate information, which is not processed by the GPCs.

Before any radar mode is used, the orbiter is normally maneuvered to an attitude with the minus Z axis pointing at the target location. In all modes, therefore, the radar antenna is normally maneuvered around the minus Z axis.

The Ku-band system provides for antenna steering modes, each with a different combination of capabilities for acquiring and tracking a target: GPC, GPC DESIG, AUTO TRACK, and MAN SLEW. All are mutually exclusive and crew selectable using the rotary switch on panel A1U.

The GPC mode is fully automatic in all phases of target acquisition. Two GPC CRT commands are required before this mode can be initiated (GNC SPEC 33, REL NAV DISP). One CRT command enables target position data to be routed from the GNC to the SM antenna management program through the intercomputer data bus (GNC SPEC 33, REL NAV DISP, item 1). The antenna management program converts the target position to antenna pointing angles and estimated orbiter-to-target range data. Another CRT command enables the antenna management program to send designated antenna pointing and range data to the Ku-band system through the payload 1 data bus and the payload forward 1 MDM (GNC SPEC 33, item 2).

When the GPC mode is selected, the antenna points to the commanded angles and adjusts the ranging system to the specified range. If a receive signal is detected, the automatic closedloop system tracks the target in angles and range and provides data for the SM and GNC computers and panel displays. If the target is not detected, the antenna is automatically commanded to search  around the designated point. The antenna is inertially stabilized during the search operation.

The GPC DESIG mode provides the same designated pointing as the GPC mode without angle search or angle-tracking capabilities. No closed-loop angle tracking is provided. The designated angles are updated every 2 seconds. Range search and tracking are automatic. The antenna may be either inertially or body stabilized.

The AUTO TRACK mode begins with manual antenna control, including a manually initiated search and inertial stabilization during the target acquisition phase. Once the target is detected, automatic angle and range tracking is initiated and manual control is inhibited until auto tracking is broken.

The MAN SLEW mode allows manual control of antenna movement with maximum automatic range search. Once the target is detected, an automatic range track is initiated, but angles are still under manual control. No angle search isavailable in this mode.

The SEARCH mode, selected by a switch on panel A1U, involves a programmed antenna movement that causes the radar beam to describe a spiral pattern starting at the designated angles. The beam angle spirals out to a maximum of 30° from the designated angle. In the GPC steering mode, the variation of the maximum angle of search from the designated point is inversely proportional to designated range. The smallest search spirals outward to a maximum of 6.2° from the designated point for ranges from 145 to 300 nautical miles (n. mi). At minimum ranges (0 to 8 n. mi.), the spiral search is the maximum 30° from the designated point. If the antenna drive system detects but overshoots the target during a spiral search, a miniscan program is automatically initiated near the point of detection. The miniscan searches to a maximum of 9° from the starting point in 1 minute. In the auto track steering mode, only the manually initiated main 30-degree scan is available. In addition to angle search, the Ku-band system provides a range search. The process includes electronically varying the timing within the range system until it coincides with the time interval between the transmitted and received radar pulses. Once the intervals coincide, radar tracking is established, and the range data output represents the range between the target and the orbiter. The crew can read the range and range rate values as panel and CRT parameters.

The crew is provided with two controls associated with range. Transmitter power output is automatically varied in proportion to range when a target is being tracked to keep the return signal relatively constant, regardless of range. If, however, the track is lost, and the range system begins to search, the transmitter may transmit maximum power during the search. The crew can limit the maximum transmitter power by using an aft station panel control. The other control is a CRT command that limits the range search in GPC steering mode to 2,400 feet. The Ku-band system has body and inertial antenna stabilization modes. When the body is stabilized, the antenna beam remains in a fixed relationship to the orbiter X, Y, and Z axes during orbiter attitude changes. When the system is inertially stabilized, the antenna beam remains aligned to a point in inertial space, regardless of the orbiter attitude changes. Both of these modes are effective only when the radar angle-tracking system is not tracking a target. In the target angle-tracking mode, the system aligns the antenna beam to the target, and antenna movement is independent of orbiter attitude changes.

Each antenna steering mode, except the designate mode, has a specific stabilization mode. The designate mode selects either body or inertial stabilization on the basis of a realtime GPC command (not available to the crew). Since the designate mode provides range tracking only, inertial stabilization is effective during target tracking.

The COMM/RCDR display, DISP 76, provides the status of Ku-band temperatures (PA, GMBL, GYRO), power out (in watts), frame sync, and mode (COMM or RDR), to flight crews.

Payload Communication System

The payload communication system is used to transfer information between the orbiter and its payload or payloads. It supports hardline and radio frequency communications with a variety of payloads. The system is used to activate, check out, and deactivate attached and detached payloads.

Communication with an attached payload takes place through the payload patch panel at the crew compartment flight deck aft station, which is connected to payloads in the payload bay. All command and telemetry signals that meet the payload communication system specifications can be processed onboard. Incompatible signals can be sent to the ground through Ku-band or directly to payload ground stations. This method of transmission, referred to as bent-pipe telemetry, means that no onboard signal processing occurs before the telemetry is sent to the Ku-band system. Payload telemetry can go directly to the S-band FM or Ku-band systems for transmission to the ground, payload analog, or payload digital, to the payload recorder for later transmission, or to the payload data interleaver to be interleaved with other payload data. The system also processes commands and provides payload telemetry to the pulse code modulation master unit (PCMMU), where the data can be accessed for display on various payload-related controls and displays.

S-Band PAYLOAD Switches on Panel A1L

S-BAND PAYLOAD Switches on Panel A1L

 

The S-band payload antenna is located on the top of the outer skin of the orbiter's forward fuselage, just aft of the S-band FM upper hemispherical antenna. The payload antenna is covered with reusable thermal protection system. This antenna is used as the radiating element for S-band transmission and reception to and from the orbiter to detached payloads through the forward and return links.

Communication problems involving antenna position relative to payload position are not evident while the payload is within a half mile of the orbiter, along the minus Z axis. However, to maintain good communication with the orbiter from distances of several miles, the payload must be within an 80-degree beamwidth (with reference to the minus Z axis) of the orbiter's payload interrogator antenna. The boundary of the 80-degree beamwidth is the 3-decibel point (or half-power point), which must be considered during communication with deployed payloads. This constraint is normally satisfied by the payload deployment and retrieval process.

The basic elements in the payload communication system are the payload interrogator (PI), payload signal processor (PSP), communication interface unit (CIU), payload data interleaver (PDI), pulse code modulation master unit (PCMMU), and payload recorder (PL RCDR). These elements are in the forward avionics bays. Commands to the payload communication system are routed through the GCILC from the payload MDMs 1 and 2, although these MDMs are also used for orbiter commanding. Status and control of payload communication systems can also be accessed by the PCMMU/PL COMM display (SPEC 62).

PCMMU/PL COMM Display (SPEC 62)

PCMMU/PL COMM Display (SPEC 62)

Payload Interrogator

Detached payloads communicate with the orbiter on an RF signal through the payload antenna by the payload interrogator. The payload interrogator is a transmitter/receiver/transponder unit that provides full duplex RF communications between the orbiter and a detached payload. It transmits commands to and receives telemetry from NASA- or DOD compatible payloads through the payload antenna. Payload interrogator controls are located on panel A1L.

The main carrier frequency of the detached payload telemetry is demodulated by the payload interrogator. The telemetry is routed directly to the Ku-band system for transmission to the ground (bent-pipe telemetry) and to the payload signal processor. The payload signal processor demodulates the telemetry from the subcarrier and sends it to the payload data interleaver to be interleaved with other payload data. Hardline payload commands are routed through the payload signal processor and then output through the payload patch panel directly to an attached payload. Detached RF commands are routed through the payload signal processor and then through the payload interrogator for transmission to the payload through the payload antenna.

The payload interrogator receiver automatically sweeps to acquire and track an unmodulated or modulated RF signal. Payload interrogator telemetry is available through an operational instrumentation MDM to verify signal strength and frequency lock. If payload frequencies are near the orbiter S-band frequencies, care must be taken to prevent interference.

When the payload outputs a data rate that is not compatible with the payload signal processor or communication interface unit, payload telemetry is throughput to the PDI without processing.

Payload Signal Processor

The payload signal processor is the RF and hardline command interface between the ground or flight crew and the payload. It is also a detached payload telemetry interface to the payload data interleaver. The payload signal processor is controlled by the switches on panel A1L. The payload signal processor output is commanded or selected by the PSP CMD OUTPUT switch.

The PI and PSP are commanded through GCILC/MCC or selected by the crew (AIL) using the two power switches.

Communication Interface Unit

The communication interface unit sometimes replaces the payload signal processor. The payload signal processor may be retained to act as a backup. The communication interface unit is commonly used with the inertial upper stage, although it may be used with other payloads compatible with SGLS. The communication interface unit interfaces indirectly with the payload data interleaver through the patch panel because the communication interface unit is treated as an attached payload accessed through a patch panel input of the payload data interleaver. The payload signal processor is hard-wired directly to the payload data interleaver. This provides a command and telemetry path between the orbiter guidance, navigation, and control, GPC, and an SGLS compatible payload or between the flight crew and an SGLS-compatible payload. The communication interface unit passes commands and telemetry to either attached or detached payloads. COMMUNICATION INTERFACE UNIT controls are on panel L11.

Payload Data Interleaver

In the NASA mission configuration, the payload patch panel interfaces attached payloads to the PDI. The PSP acts as the interface for detached payloads. Attached payloads are wired to specific input channels of the PDI via the payload patch panel during prelaunch activities. When the PDI is reconfigured by the flight crew, programming procedures include assigning inputs in the PDI to one of four decommutators. The PDI allows the payload communication system to interface with the rest of the orbiter communication system and computers. It receives up to six different inputs from attached or detached payloads and one ground support equipment input. For missions using the payload signal processor, a maximum of five attached payloads can be accommodated on inputs 1 through 5. Input 6 is reserved for detached payload telemetry using the RF link through the payload signal processor. For missions using the communication interface unit, all data, attached or detached, are routed through input 5. The PDI has four decommutators that can process up to four payload data streams. The PDI ships the payload telemetry to the PCMMU, where it can be accessed by the SM GPC for display, and combined with orbiter telemetry for transmission to the ground. The PL DATA INTLVR POWER switch is on panel A1L.

COMMUNICATION INTERFACE UNIT Controls on Panel L11

COMMUNICATION INTERFACE UNIT Controls on Panel L11 

 

 

Ultrahigh Frequency System

The UHF system is used as a backup for the Sband PM and Ku-band voice communications, and is primary during EVA operations. For communications with MCC through the STDN or SGLS ground stations, the UHF system operates in a simplex mode, which means that the orbiter flight crew can transmit or receive, but cannot do both simultaneously. The UHF system may also be used for air traffic control and two-way voice with chase aircraft during landing operations.

The UHF transceiver takes the voice signal from the audio central control unit and routes it through the external UHF antenna on the bottom of the orbiter forward fuselage for transmission to the ground station. The incoming UHF signal goes through the external antenna to the UHF transceiver, which demodulates it and routes it as an audio signal it to the audio central control unit for distribution in the orbiter.

Part of the UHF configuration is controlled through three two-position toggle switches on panel O6 labeled XMIT FREQ, SPLX PWR AMPL, and SQUELCH. The XMIT FREQ switch selects one of the two UHF frequencies, 296.8 MHz primary or 259.7 MHz secondary, for external transmission. The SPLX PWR AMPL switch enables or inhibits the UHF power amplifier circuit. When the switch is positioned to ON, the UHF system transmits 10 watts of power through the antenna. When the switch is positioned to OFF, the power transmission is reduced to 0.25 watts by bypassing the power amplifier circuit. (An airlock antenna is used by EVA astronauts in extravehicular mobility units to check out their transceivers before exiting the airlock.) The SQUELCH switch permits ON or OFF selection of UHF squelch.

UHF Subsystem Functional Block Diagram

UHF Subsystem Functional Block Diagram

 

UHF System Controls on Panel 06

UHF System Controls on Panel 06

 

A five-position UHF MODE rotary switch on panel O6 activates power to the UHF transceiver and is used to select any of the following modes of UHF transmission. When the rotary switch is positioned to EVA, EVA transmissions are made on one frequency selected by the XMIT FREQ switch. The return signal is received on two other frequencies. The OFF position removes all electrical power. When the rotary switch is positioned to SPLX, transmission and reception are both on the frequency selected by the XMIT FREQ switch. Positioned to SPLX + G RCV, transmission and reception are the same as in simplex except that reception of the UHF guard (emergency) frequency (243.0 MHz) also is possible. In the G T/R position, transmission and reception are both on the UHF guard (emergency) frequency.

Three two-position UHF toggle switches located on the bottom of the AUDIO CENTER portion of panel A1R control routing of audio from the audio central control unit to the UHF transceiver. The switches are labeled T/R for transmit/receive, OFF for blocking UHF audio to and from the UHF transceiver, A/G for the air-to-ground channels, and A/A for the air-to-air channel.

UHF Controls on Panel A1R

UHF Controls on Panel A1R

 

For normal EVA operations, the orbiter transmits 296.8 MHz and receives 259.7 and 279.0 MHz. The EVA astronauts are transmitting voice and biomedical/suit data on their respective frequencies. The biomedical/suit data is routed through the OI system once it is removed from the UHF carrier. The astronaut configured for mode A transmits on 259.7 MHz. The astronaut configured for mode B transmits on 279.0 MHz. Each of the two EVA astronauts receives the other on the respective transmitted frequencies. Every 2 minutes, biomedical data are replaced with suit telemetry data for 15 seconds. EVA conversations are routed to Mission Control via the S-band PM or Ku-band system on A/G 1 or A/G 2, depending on the configuration of the UHF A/G 1 and A/G 2 switches on panel A1R. As a backup procedure only when the orbiter is over a UHF ground station, the EVA astronauts, orbiter, and ground can switch to the 259.7-MHz UHF, simplex. The UHF system may be used after entry during the approach and landing phase of the mission. UHF air-to-ground voice communications may take place between the orbiter, the landing site control tower, and chase planes (if used).

Audio Distribution System

The audio distribution system gathers audio signals from multiple sources and routes them throughout the orbiter. It provides the means by which crew members communicate with each other and with external locations, such as seconds. EVA conversations are routed to Mission Control via the S-band PM or Ku-band system on A/G 1 or A/G 2, depending on the configuration of the UHF A/G 1 and A/G 2 switches on panel A1R. As a backup procedure only when the orbiter is over a UHF ground station, the EVA astronauts, orbiter, and ground can switch to the 259.7-MHz UHF, simplex.

Audio Loops and System Interface

Audio Loops and System Interface

 

Mission Control, through the S-band PM, Kuband, and UHF systems. It also interfaces with the caution and warning system for reception of C/W (tone) signals and with the three tactical air navigation (TACAN) sets for monitoring the TACAN audio identification codes. The external communications are facilitated by routing AG1/2 through the network signal processor. The audio distribution system outputs audio for one or both of the A/G loops to the network signal processor where it is digitized and sent to the S-band PM and Kuband systems for downlink to MCC. Uplink digitized A/G audio is routed through the S-band PM or Ku-band systems and the network signal processor where it is converted to analog for use in the audio distribution system. This system also provides connections to the UHF transceiver via the AA loop for external communications with MCC through ground base sites which support UHF. As previously stated, UHF is also used as prime voice communications with EVA crewmembers. Normally in the EVA mode, the AG1 loop is routed to and from the audio distribution system. The audio distribution system routes audio signals to an onboard Spacelab module, docking ring, operations recorder, payload bay stations, and the video distribution system under control of switches on panel A1R.

The major elements of the audio distribution system include:

1. Audio central control unit (ACCU) -acts as central "switchboard" to gather and route audio signals throughout the orbiter; internally redundant linere placeable unit.

2. Audio terminal unit (ATU) - control panels at crew stations that permit crewmembers to select audio talk/listen buses and to control external/internal communication keying modes and listen volume levels.

3. Speaker unit (SU) - two speaker units are provided with the orbiter communications system. One is mounted on the flight deck aft A2 panel. A second speaker unit is mounted on the middeck ceiling panel MO29J. Both are connected to and subject to an associated ATU configuration.

4. Audio center panel - control center for extending audio buses to docking ring, Spacelab, payload bay outlets, video distribution system, and the UHF system, and for selecting up to two voice signals for recording on the operations recorder.

5. Loose communications equipment - miscellaneous small, stowable items such as the headset interface unit (HIU), headset/helmet cables, wireless crew communications unit (WCCU), and handheld or wireless handheld mic.

6. Crew communications umbilical (CCU) jack - individual panel mounted jacks at crew stations where mating headset plugs give the crew access to audio buses. At each CCU location is an associated ON/OFF switch to control power to the headset interface unit or wireless communications unit utilizing that jack.

The eight loops in the audio system are (1) airto-ground 1, (2) air-to-ground 2, (3) air-to-air, (4) intercom A, (5) intercom B, (6) paging, (7) C/W, and (8) TACAN. A/G 1 and A/G 2 are used to communicate with the ground through the S-band PM and Ku-band systems and UHF during EVA operations. (In the NSP low-datarate mode or while used with other loose communications gear such as the thermal impulse printer system, A/G 2 is not available for voice communications.) A/A is used, by convention, to communicate with the ground and with EVA astronauts through the UHF system. Intercoms A and B are used to communicate from station to station within the orbiter and Spacelab. The paging loop allows one crewmember to send voice transmissions to all active stations. The C/W loop sounds different tones for different malfunctions or emergencies. The TACAN loop, accessible only at the commander's and pilot's stations, is used to identify TACAN ground stations for navigation.

Audio Central Control Unit

The ACCU, the heart of the audio system, is located in the crew compartment middeck forward avionics bay. (There are two redundant ACCUs, but only one is used at any given time.) The unit identifies, switches, and distributes analog audio signals among the various audio distribution system components. Both digital and audio signals are received and processed by the ACCU. The digital signals are used to control the internal configuration of the ACCU per the switch positions on the ATUs and other devices. The audio signals are keyed and routed in response to this internal configuration. Other devices include the audio center panel and the NSP. It is through these devices that audio is routed to the ultrahigh frequency, S-band PM, and Ku-band transmitters and receivers for communications external to the orbiter.

The AUDIO CENTER selection switch is on panel C3. Setting the switch to 1 applies primary power to the control center unit from the ESS 2CA AUD CTR 1 circuit breaker on panel R14. Selecting 2 applies power to the secondary unit electronics from MN C AUD CTR 2 circuit breaker on panel R14. OFF removes all power from the ACCU.

NOTE

With the AUDIO CENTER selection switch OFF, all normal audio functions will be inoperative. However, the commander and pilot can communicate via headset if one of their ATU CONTROL switches is set to the alternate position. This is also true for any two stations that share ATUs through the audio control switch position (i.e., mission specialist and payload specialist, airlock CCU 1 and 2, and middeck ATU).

The ACCU circuitry activates signals from the launch umbilical connection intercom A and B channels. Any crew station ATU can then be configured to transmit and receive intercom signals from the ground through the umbilical. (Only intercom signals are processed through the umbilical.)

AUDIO CENTER Selection Switch on Panel C3

AUDIO CENTER Selection Switch on Panel C3

 

Commander's Audio Terminal Unit of Panel 05

Commander’s Audio Terminal Unit of Panel 05

Audio Terminal Unit on Panel AW18D

Audio Terminal Unit on Panel AW18D

 

Audio Terminal Units

Up to eight ATUs are used in the crew compartment to select access at each station and to control the volume of various audio signals. Audio terminal unit panels are located at the following crew stations: commander, panel O5 (LEFT AUDIO); pilot, panel O9 (RIGHT AUDIO); mission station, panel R10 (MISSION STATION AUDIO); payload station, panel L9 (PAYLOAD STATION AUDIO); middeck, panel M042F (MID DECK SPEAKER AUDIO); and airlock, panel AW18D (AIRLOCK AUDIO). These panels control signals to headsets or communication carrier assemblies through the communications umbilical. Orbiter OV-102 has two additional ATUs. One is in the flight deck (OS AUDIO), mounted on panel A13 for use with the flight deck speaker unit. (On all other orbiters, the MISSION STATION AUDIO audio terminal unit is used with the flight deck speaker unit.) The second ATU, in the middeck, is AIRLOCK 1 BACKUP, which is mounted at the MO58F position and acts only as a backup for the airlock CCU1 headset CONTROL function. (The AIRLOCK AUDIO CCU 2 headset connection uses the MIDDECK SPEAKER AUDIO audio terminal unit as a control function backup.)

Each ATU has a three-position power switch to control all signals to or from the ATU. The switch positions are AUD/TONE, AUD, and OFF. In the AUD/TONE position, all available functions of the ATU are armed, and transmission and receptions may be made through the ATU, depending on the position of other switches on the ATU. C/W tone signals are sent to the ACCU to allow C/W audio to reach the ATU, the CCU, and the speaker unit. The AUD position has the same functions as AUD/TONE except that C/W signals are blocked from the ATU. The OFF position shuts off power to the ATU power supply, for the ATU amplifiers. Klaxon (cabin air pressure) and siren (fire) C/W signals go directly to a speaker unit, even with the speaker power off. Each ATU has a two-position, spring-loaded-off PAGE switch that must be held in the PAGE position to activate the circuit. When activated, the circuit enables the ATU to transmit to all other ATUs, the EVA transceiver, and the attached payload circuit (e.g., Spacelab). Any number of stations may use the paging circuit simultaneously, and the circuit may be used regardless of the position of the other channel control switches.

On all ATUs, the two air-to-ground channels, the air-to-air channel, and intercom channels A and B have individual three-position control switches for selecting access to particular channels for transmission or reception. The switch positions are T/R, RCV, and OFF. The T/R position permits transmission or reception over the selected channel. The RCV position deactivates transmission capability on the selected channel and permits only reception of signals. The OFF position deactivates transmission and reception on the selected channel. These control switches do not turn on any transmitter or receiver but allow access to a transmitter or receiver.

Pilot's Audio Terminal Unit on Panel O9

Pilot’s Audio Terminal Unit on Panel O9

Audio Terminal Unit on Panel R10

Audio Terminal Unit on Panel R10

Audio Terminal Unit on Panel L9

Audio Terminal Unit on Panel L9

 

Audio Terminal Unit on Panel A13 (OV-102)

Audio Terminal Unit on Panel A13 (OV-102)

MS AUDIO CONTROL Switch on Panel R11L

MS AUDIO CONTROL Switch on Panel R11L

 

Each channel control switch has a thumbwheel VOLUME control to adjust signal intensity on the related channel. The thumbwheels cover a range of approximately 27 decibels in 3-decibel increments.

The XMIT/ICOM MODE rotary switch controls four combinations of external and intercom transmissions. In the PTT/HOT mode, transmission through A/G 1, A/G 2, and A/A requires manual keying of the headset interface unit, microphone, or WCCS leg unit XMIT PTT button; intercom A and B will be hot mike. In the PTT/VOX mode, A/G 1, A/G 2, and A/A require PTT of the XMIT button, while intercom A and B are voice keyed. In the PTT/PTT mode, all voice channels are voice keyed. In the VOX/VOX mode, all voice channels are voice keyed.

The VOX SENS rotary potentiometer on the ATUs regulates the volume of the signal required for voice keying. The MAX setting requires a lower decibel level to key the circuit than the MIN setting.

Volume control of all incoming signals to speakers is adjusted by the MASTER SPEAKER VOLUME controls on panels A13 and MO42F. The MASTER VOLUME 1 and 2 potentiometers on panel AW18D control volume to the respective CCU outlets in the airlock. Four ATUs (on panels O5, O9, AW18D, and R10) allow a crewmember at a malfunctioning ATU to switch the CCU jack to an alternate ATU. The left may be switched to the right (commander's to pilot's ATU), or right ATU control may be switched to the left (pilot's to commander's ATU). The commander's and pilot's CONTROL knobs are located on panels O5 and O9. Mission specialist ATU may be switched to the payload specialist's ATU using the MS AUDIO CONTROL switch on panel R11L. Airlock ATU control may be switched to the middeck and payload specialist's ATUs using the CONTROL rotary switch on panel AW18D. Orbiter OV-102 uses the AIRLOCK 1 BACKUP ATU for airlock CCU 1 alternate control.

When the CONTROL switch is in the NORM position, control of the ATU is from the panel to which the knob belongs. The other position of the knob indicates the ATU to which control can be transferred. The CONTROL knob changes all ATU functions to the alternative ATU except the master volume control. This redundancy protection is used in the event of a failure or malfunction of any of the four audio terminal units that have a CONTROL knob.

Speaker Unit on Panels A2 and M02J

Speaker Unit on Panels A2 and M02J

 

NOTE

If an ATU loses power, switching to the other CONTROL position will restore listen capability but not talk capability.

Speaker Units

An SU is located on panels A2 and MO29J. They are controlled by the ATU on panels R10, A13, and MO42F in orbiters OV-103, -104, and -105. They are controlled by the ATU on panels A13 and MO42F in orbiter OV-102 . In addition to the features of the other ATUs, the speaker unit ATU has a three-position SPKR PWR switch. Only the OFF and SPKR positions are used. In the OFF position, no signals go through the ATU. In the SPKR position, audio selected on the associated ATU, including C/W tones, are enabled. The SPKR/MIC position is not used. The top speaker is used for audio and the bottom is dedicated to the klaxon/siren. The KEY light illuminates when a microphone on the associated ATU is keyed (PTT, VOX, etc.)

Audio Center Panel

The AUDIO CENTER controls on panel A1R have four functions: UHF control, voice interface capability with external vehicles, the payload bay comm outlets, and operations recorder selection. All switches on the panel send digital impulses to the ACCU, enabling the selected functions to communicate with Spacelab, the payload bay, and operations recorders. Sets of toggle switches labeled  DOCKING RING, SPACE LAB, and PL BAY OUTLETS electrically connect the particular function to the audio distribution system. The DOCKING RING and SPACE LAB subpanels have seven switches to enable the following functions: A/A, A/G 1, A/G 2, ICOM A, ICOM B, PAGE, and TONE (C/W). The UHF switches control A/G 1, A/G 2, and A/A channels to the UHF transceiver. The PL BAY OUTLETS subpanel has two ON/OFF switches, one for intercom A and one for B. The PL BAY OUTLETS switches also route ICOM A and B to the CCTV system for interleaving with the video signals.

AUDIO CENTER Controls on Panel A1R

AUDIO CENTER Controls on Panel A1R

 

Two rotary knobs labeled VOICE RECORD SELECT control various audio signals to be sent to the operational recorders through the NSP.  A/G 1, A/G 2, A/A, and ICOM A or B audio can be sent to either recorder. Any two signals may be recorded at the same time, one on channel 1 and the other on channel 2. Either channel may be turned off. A recorder input (RCDR INPUT) parameter on orbiter display S76 indicates whether the recorder is recording data (DATA) only or data plus the voice selected on the AUDIO CENTER panel (D/VO).

Loose Communications Equipment

Launch and Entry Helmets

During launch and entry, each flight crewmember wears a launch and entry helmet to lessen the severe noise levels encountered at launch and to allow intelligible air-to-ground communications. A communications carrier assembly headset containing microphones and earphones fits over the crewmember's head, and a connector and cable interface with the headset interface unit, connected through communications cables to respective audio terminal units. The microphones can be positioned to suit the individual crewmember. For emergency egress, a pull-away connection is used between the communications carrier assembly and headset interface unit, in addition to the standard communications carrier assembly/headset interface unit twist-on connector.

The helmets have redundant noise-canceling microphones and electrically isolated earphones. When air is inhaled, the demand breathing regulator shuts off the microphones to avoid transmitting breathing sounds.

NOTE

An improper face seal will cause enough oxygen flow to cut off microphones.

Headset Interface Unit

The headset interface unit has separate push-to-talk (PTT) buttons for transmit and intercom modes and a volume control that determines the level of sound heard through the earphone (microphone sound level is determined by automatic gain control circuitry within the audio terminal unit). (Push-to-talk means that a pushbutton must be depressed to allow a crewmember to talk through the system.) The XMIT pushbutton allows access to intercom and external circuits, while the ICOM pushbutton is for intercom only. The volume control knob acts in series with the loop volume controls on the associated audio terminal unit. In addition, the commander and pilot have PTT switches on their rotational hand controllers for transmit (XMIT) keying.

The headset interface unit provides volume control and PTT capabilities to the communications carrier assembly used for EVA, and to the communications carrier assembly. The headset interface unit has a clip that attaches to the crew's flight suits.

Headset Interface Unit Image

Headset Interface Unit

 

Crewman Communications Umbilical on Panel L5

Crewman Communications Umbilical

 

Cables

The communication cables vary in configuration depending on seat location. Each seat has two 4-foot communication cables or a 14-foot length, as required. One 4-foot cable is flown as a spare. The cables connect to crewman communications umbilical (CCU) outlets at various locations in the crew compartment. Each CCU has a specific audio terminal unit that controls communication loop configurations. The CCU associated with the ATU on panel O5 is located on panel L5 (LEFT COMM); for O9 on R6 (RIGHT COMM); for R10 on A11 (MS COMM), for L9 on A15 (PS COMM), and for MO42F on MO39M (MID DECK COMM); two others for the airlock ATU are located on panel  AW82D (CCU 1 and CCU 2).

Each CCU outlet has a power switch that controls the associated microphone power. Leaving CCU power off confines an individual to a listen-only mode, independent of audio terminal unit configuration.

Multiple Headset Adapter

A multiple headset adapter may be plugged into the CCU outlets. The three CCU outlets on the adapter allow up to three crewmembers to share one CCU outlet. When any one person connected to a multiple headset adapter keys (in PTT mode) or activates the voice-operated transmitter, all three individuals' microphones will be keyed, and individuals sharing the multiple headset adapter will hear each other talking on the side tone.

Wireless Communications Units

On orbit, the crew may use wireless communication units in place of communication cables. A wireless unit consists of one wall unit (audio interface unit) and two leg units (crew remote units) worn by crewmembers during orbital operations. The wall unit connects to a CCU outlet and remains attached to the crew compartment wall. Each wall unit transmits on a unique pair of UHF frequencies. Leg units may be configured to work with any wall unit. A leg unit may be converted into a wireless handheld microphone by attaching a noise cancelling mic at the headset connector. Each wall unit is identified by a letter enclosed in a box. Each unit is stowed with its cabling attached. The wall unit has a 23-inch cable to interface with the CCU outlet, and the leg unit has a 22-inch cable attached to a lightweight headset.

NOTE

If the two leg units are set to use the same frequency, one of the units' transmit signals will be muted.

When the wireless unit is unstowed, part of the assembly necessary is to insert and tighten the flexible antenna in the bottom of each wall and leg unit. The wall unit receives power from the CCU outlet. All other switches are set as required; typically, the individual communication loops are used. The leg unit is attached to the crewmember's leg with a wraparound elastic strap. The rotary ON/OFF/VOLUME knob (unlabeled) is turned clockwise past the ON/OFF detent, and the volume is set as desired. Each leg unit is powered by a replaceable lithium battery pack. A weak battery is identified by a continuous beeping sound when the leg unit is powered on. A single battery pack provides about 35 hours of service. Sliding a new battery pack into the unit causes both the electrical connector and mechanical connector to latch.

Very Lightweight Headset

The very lightweight headset is the interface between the leg unit and crewmember. A single-strand wire headband holds the earphone against the ear and supports a thin boom holding a noise-cancelling microphone near the mouth. A cable and connector are attached to the crewmember's leg unit. The lightweight headset cable and connector also can interface with the headset interface unit.

Very Lightweight Headset

Very Lightweight Headset

Handheld Microphone

The handheld microphone is a noise-canceling microphone that connects directly to any CCU outlet. The microphone is used primarily with the SUs located at panels A2 and MO29J. To avoid feedback when using the speakers, one ATU and its corresponding CCU outlet on the aft flight deck and one ATU and associated CCU on the middeck are equipped with a speaker muting capability. On OV103, OV104, and subsequent vehicles, muting is controlled through ATUs at panels R10 and MO42F. On OV102, the muting ATUs are located at panels A13 and MO42F. Two PTT pushbuttons are provided for XMIT and ICOM audio modes. When used to record audio on the videotape recorder, either can be used. The pushbuttons should face the operator to ensure that the noise-canceling feature of the microphone remains functional. The handheld microphone is equipped with a 7-foot cable that can connect at any CCU or to other cables. The microphone/SU configuration is used for on orbit communication configurations.

Instrumentation

Orbiter operational instrumentation (OI) collects, processes, and routes information from transducers and sensors throughout the orbiter and its payloads. More than 3,000 data parameters are monitored.

Simplified Instrumentation Data Flow

Simplified Instrumentation Data Flow

 

Operational Instrumentation System Overview

 

Operational instrumentation System Overview

 

OI System

OI System

The instrumentation system consists of transducers, 14 dedicated signal conditioners (additional dedicated signal conditioners (DSCs) for extended duration orbiter (EDO) missions), 7 MDMs, 2 PCMMUs, 2 operational recorders, 1 payload recorder, master timing equipment, and onboard checkout equipment.

The OI system senses, acquires, conditions, digitizes, formats, and distributes data for display, telemetry, recording, and checkout. It provides for pulse code modulation recording, voice recording, and master timing for onboard systems.

Instrumentation equipment, except sensors and selected dedicated signal conditioners, is located in the forward and aft avionics bays. Sensors and DSCs are located throughout the orbiter in areas selected on the basis of accessibility, minimum harness requirements, and functional requirements. Abbreviations used to designate the locations of equipment are as follows: OA refers to operational aft, OF to operational forward, OL to operational left, OR to operational right, and OM to operational mid.

Dedicated Signal Conditioners

Dedicated signal conditioners acquire and convert various sensor data from thousands of orbiter sensors into a 0-5 V dc pulse acceptable to MDMs. Sensors requiring DSCs include frequency,  temperature, rate, voltage, current, and analog parameters.

There are 14 orbiter DSCs, 4 in forward avionic locations (OFs), 3 in the aft avionic bays (OAs), 3 under the payload bay (MID) (OMs), and 4 in the right and left tail sections (ORs and OLs). There can be up to four additional DSCs flown with the EDO.

Multiplexer/Demultiplexers (MDMs)

MDMs can operate in two ways. As multiplexers, they take data from several sources, convert the data to serial digital signals (a digitized representation of the applied voltage), and interleave the data into a single data stream. As demultiplexers, the MDMs take interleaved serial digital information, separate and convert it to analog, discrete, or serial digital, and send each separate signal to its appropriate destination. The OI MDMs act only as multiplexers. Upon request from the pulse code modulation master unit (PCMMU), the MDMs send these interleaved streams to the PCMMU through the OI data buses. When the MDM is addressed by the PCMMU, the MDM selects, digitizes, and sends the requested data to the PCMMU in serial digital form. The PCMMU/OI MDM interface is based on demand and response; that is, the OI MDMs do not send data to the PCMMU until the PCMMU makes the request. There are seven OI MDMs, four OFs, and three OAs for forward and aft multiplexing of DSC and direct data signals.

Pulse Code Modulation Master Unit (PCMMU)

The PCMMU receives data from the OI MDMs, downlist data from the GPCs under control of flight software, and payload telemetry from the payload data interleaver and Spacelab. It then interleaves the data, formats data according to programmed instructions stored within the PCMMU (the telemetry format load, or TFL), and sends the interleaved data to the network signal processor to be combined with the analog air-to-ground voice data from the audio central control unit for transmission through the S-band PM downlink and Ku-band system return link, channel one. Telemetry from the PCMMU is also sent through the network signal processor to the operational recorders for storage and subsequent downlink on the S-band FM or Ku-band system. OI and payload data collected by the PCMMU are available to the GPCs for display and monitoring purposes upon request. All data received by the PCMMU are stored in memory and periodically updated.

The PCMMU has two formatter memories: programmable read only (PROM) and random access (RAM). The read-only memory is hard coded; the RAM is reprogrammed several times during flight. The PCMMU uses the formatters to load data from the computers and OI MDMs into PCM telemetry data streams for down linking

NOTE

When the PCMMU is powered off (as when switching to the alternate unit), the TFL changes to the fixed format loaded in the PROM.

One of the two redundant PCMMUs and network signal processors operates at a time. The one used is controlled by the crew through the flight deck display and control panel. The primary port of each MDM operates with PCMMU 1 and the secondary port operates with PCMMU 2.

OI PCMMU Controls on Panel C3

OI PCMMU Controls on Panel C3

The PCMMUs receive a synchronization clock signal from the master timing unit. If this signal is not present, the PCMMU provides its own timing and continues to send synchronization signals to the payload data interleaver and network signal processor. The OI PCMMU controls are located on panel C3.

Master Timing Unit

The master timing unit is a stable crystal controlled timing source. It provides synchronization for instrumentation, payloads, and other systems. The master timing unit is described in more detail in Section 2.6.

Recorder Controls on Panel A1R

Recorder Controls on Panel A1R

 

Operations Recorders

Two recorders are used for serial recording and dumping of digital voice and pulse code modulation (PCM) data from the OI systems. The recorders normally are controlled by ground command, but they can be commanded by the flight crew through the flight deck display and control panel keyboard or through the OPS RECORDERS switches on panel A1R or commanded via uplink. The input to the recorders is from the network signal processor, in main engine data at 60 kbps.

The operations recorders can be commanded to dump recorded data from one recorder while continuing to record real-time data on the other. The dump data are sent to the FM signal processor for transmission to the ground station through the S-band FM transmitter on the S-band FM return link or to the Ku-band signal processor. When the ground has verified that the received data are valid, the operations recorders can use that track on the tape to record new data. If ground is controlling recorders, the crew cannot, unless ground sets a "crew reset" command or its equivalent from SPEC 1.

Recorder speeds of 7.5, 15, 24, and 120 inches per second are provided by hardwire program plug direct command. The tape recorders contain a minimum of 2,400 feet of 0.5-inch by 1-mil magnetic tape.

Recorder functions can be summarized as follows:

– Accept three parallel channels of engine data at 60 kbps during ascent.

Accept 192 kbps of interleaved PCM data and voice that serially sequences from track 4 to track 14 (high data rate), 128 kbps data only (high data rate), or 96 kbps data and voice (low data rate).

Accept real-time data from network signal processor. Recording time is 32 minutes for parallel record and 5.8 hours for serial record on tracks 4 through 14 at a tape speed of 15 inches per second.

Accept 192 kbps of interleaved PCM voice and data that serially sequences from track 1 to track 14 (high data rate), 128 kbps data only (high data rate), or 96 kbps data and voice (low data rate).

– Accept real-time data from network signal processor. Recording time is 7.5 hours at a tape speed of 15 inches per second for serial record on 14 tracks.

– Play back in-flight engine interface unit data and network signal processor digital data through S-band FM transponder or Ku-band transmitter.

– Play back in-flight anomaly PCM data for maintenance recording.

– Play back data serially to ground support equipment to T-0 ground support equipment umbilical.

– Play back digital data through S-band FM transponder or Ku-band transmitter in flight.

Play back anomaly PCM data in flight for maintenance recording.

Play back preflight and post flight data serially to GSE T-0 umbilical.

Payload Recorder

The payload recorder records and dumps payload analog and digital data through the S-band FM or Ku-band transmitter. The recorder can record one of three serial inputs or a maximum of 14 parallel digital or analog inputs or combinations of analog and digital data (up to 14 inputs) from the payload patch panel. In flight, all data dumps are serial; capability for parallel dumps does not exist. There are 14 selectable tape speeds; however, only four speeds, selectable by a program plug, are available per flight. Total recording time ranges from 56 minutes to 18 hours 40 minutes depending on tape speed.

The recorder normally is controlled by ground command, but can be commanded by the flight crew using the PAYLOAD RECORDER switches on panel A1R.

Thermal Impulse Printer System

The thermal impulse printer system (TIPS) is a high speed gray shade recorder employing a fixed thermal head to produce hard copies of line scan or raster scan information. It replaces the teleprinter and text and graphics systems previously flown on the shuttle. The TIPS thermal head reproduces images by bombarding thermal paper with heat pulses. The more pulses directed at one spot, the darker it becomes. One TIPS is flown in a middeck locker and can also be used as a printer for the PGSC computer. Electrical power is provided from an ac outlet on panel ML85E (MUP). TIPS can receive text data over S-band PM or Ku-band (voice channel) via STDN or TDRS. TIPS can also receive text and graphics data through Ku-band mode one (128kbps) via TDRS. The voice channel input for TIPS is accomplished through the PS COMM outlet on panel A15 nominally via A/G 2. The voice channel data transfer rate of 600 baud requires up to 90 seconds per 11 inch page depending on the number of lines. The Ku-band mode 1 input is received through the Ku-band Data Uplink Port behind the old TAGS small compartment door. When the Ku-band voice channel is used, it takes approximately 44 seconds to print 11 inches of text or dithered (laser printer style) graphics at 200 dots per inch (dpi) resolution. True gray scale graphics data will require about 4 minutes and 9 seconds per 11 inch page at 200 dpi.

To minimize crew workload, the TIPS power, communications, and Ku-band cables are routed and secured pre-launch. The procedures for connecting the three cables, reconfiguring the panel L9 ATU, and activating the TIPS are in the Orbit Ops Checklist. An illuminated green POWER pushbutton and ON LINE and READY lights indicate the TIPS is ready to print. TIPS must be ready to print when an uplink is transmitted since the MCC has no ground command over TIPS. If TIPS is not ready to print when an uplink is initiated or if it runs out of paper prior to the end of a transmission, the data will have to be retransmitted when TIPS is back on-line. The unit does not have the capability to store data for printing at a later time. Three additional 165 foot rolls of thermal paper are stowed for change out on orbit. The crew should replace the roll when the red warning strip appears along the edge of the paper.

Thermal Impulse

 

Thermal Impulse Printer System

 

 

Communications System Summary

 Specific communications system CRTs are OPS 201 ANTENNA, COMM/RCDR (DISP 76), and PC MMU/PL COMM (SPEC 62).

Comm S-Band PM Table

Comm S-Band PM Table

 

S-Band System 1 Power

S-Band System 1 Power

 

Panel A1L

Panel A1L

Panel A1R

Panel A1R

Panel A1U

Panel A1U

Panel A2

Panel A2

Panel A13

Panel A13

Panel A13 (OV102 Only)

Panel A13 (OV102 only)

Panel A13 (OV102 Only)

Panel M029J

Panel M029J

Panel M029J

Panel 05

Panel O5

OPS 201 ANTENNA Display

OPS 201 ANTENNA Display

COMM/RCDR (DISP 76) Display

COMM/RCDR (DISP 76) Display

PCMMU/PL COMM Display (SPEC 62)

PCMMU/PL COMM Display (SPEC 62)

 

Communications System Rules of Thumb