| Radar and Communications transmitted EIRP |
54 dBw |
|---|---|
| Maximum Data Rate | 50 Mbps |
| Radar Detection Range Passive Active |
14 mi. (22.2 km) 345 mi. (555.6 km) |
| Weight | 304 lb (138 kg) |
| Power Consumption
Radar Communications |
426 W5 35 W |
| Frequency (Ku Band) | 13.8 and 15.0 GHz |
A single electronics package for the Space Shuttle's Integrated Radar and Communications System saves weight, space, and cost while performing dual functions. It pinpoints objects in space as far away as 345 miles without help from Earth. And it enables crews to talk to Earth or transmit TV-like pictures, high speed data streams, or payload telemetry.
Hughes Aircraft Company's Space and Communications Group, which today is Boeing Satellite Development Center, built the IRCSs for Rockwell International Corporation, prime contractor to the National Aeronautics and Space Administration for the Space Shuttle.
In October 2000, The Boeing Company acquired three units within Hughes Electronics Corporation: Hughes Space and Communications Company, Hughes Electron Dynamics, and Spectrolab, Inc., in addition to Hughes Electronics' interest in HRL, the company's primary research laboratory. The four are now part of Boeing's newest subsidiary, Boeing Satellite Development Center.
Each shuttle is equipped with an IRCS, nicknamed the "Ku band radar" after the operating frequency. The Ku band radar was first tested in June 1983 on the shuttle's seventh mission. The system has played a critical role in several missions in which satellites were recovered in space and either repaired in orbit or returned to Earth.
The radar enables the shuttle crew, independent of assistance from the ground, to locate and rendezvous with satellites or other objects in low orbit in order to repair, maintain, or recover them. Voice, TV, and data links between the shuttle and a ground control center at White Sands, N.M., are maintained by the IRCS via a Tracking and Data Relay Satellite (TDRS) in geosynchronous orbit. Communications frequencies are in Ku band at 13.8 and 15.0 GHz.
For communications, a computer in the shuttle points the IRCS antenna in the general direction of the appropriate TDRS satellite. The antenna makes an 8° spiral scan, seeking to pinpoint the target. If the satellite is not detected in that scan, the search automatically expands to 20°. The scan process requires about 3 minutes.
The IRCS communications system has data rate capacity for 216 kbps in the uplink and 50 Mbps in the downlink mode.The subsystem has two digitized voice channels as well as capability of orbiter and payload telemetry and a choice of closed circuit TV or high speed data. The shuttle has a separate communications capability at S band, enabling crews to communicate with Earth when the radar is in use.
Radar search for space hardware uses a scan of up to 30°. Detection range in the passive mode, in which the radar beam bounces off the target, is 14 miles (22.2 km). In the active mode, in which the signal is enhanced by a transponder aboard the target, the range is 345 miles (555.6 km). The radar's custom-design computer extracts range and angle data from the received signal to locate and track the target.
| SOURCE | TYPE | RATE | PM | FM |
|---|---|---|---|---|
| Payload, High Data Rate | Analog | 4.5 MHz | X | |
| Payload, High Data Rate | Digital | 4 Mbps | X | |
| Payload, Low Data Rate | Digital | 2 Mbps | X | X |
| Payload Interrogator 1 | Digital | 1 Mbps | X | X |
| Payload Interrogator 2 | Digital | 1 Mbps | X | X |
| Payload, Recorder | Digital | 1 Mbps | X | X |
| Ops Data, Network Signal Processor 1 | Digital | 192 kbps | X | X |
| Ops Data, Network Signal Processor 2 | Digital | 192 kbps | X | X |
| Ops Recorder | Digital | 2 Mbps | X | X |
| Television | Analog | 4.5 MHz | X | |
| Payload, High Data Rate Max. | Digital | 2 to 50 Mbps | X |
| Search and Acquisition Volume | +/- 30°, 30.5 m to 22.2 km (100 ft to 12 n. mi.) |
|---|---|
| track Limits | Orbiter obscuration, 30.5 m to 22.2 km (100 ft to 12 n. mi.) |
| Range Accuracy (38) | 24.4 m (80 ft) or 1% |
| Velocity Accuracy (38) | 0.3 m/sec (1 fps) |
| Angle Accuracy (38) | 8 mr |
| Angle Rate Accuracy (38) | 0.05°/sec |
| Search and Acquisition Volume | +/- 10° about designated point |
|---|---|
| tracking Limits | Orbiter obscuration |
| Forward Link Data Rate Spread Spectrum Code Rate Signal Power Density from TDRS Acquisition Track |
216 kbps 3.0 megachips/sec 2.5 x 10-13 W/m2 0.8 x 10-13 W/m2 |
| Gain/Noise Temperature | 6.0 dB/°K |
| Return Link Data Rate Signal Power Density at TDRS |
50 Mbps 3 x 10-12 W/m2 |