- Spacecraft G/T and EIRP can be found
here (PDF, 170K).
- Type: 3-axis stabilized experimental communications
- Application: Testbed of new technology applications
available to U.S. users.
- Launch Vehicle: Space Transportation System (STS)/
Transfer Orbit Stage (TOS).
- Orbit Position: Geosynchronous, equatorial, 105.2
- Design Life: 4 Years.
- Frequency: 3 Ka-band channels, 30 GHz uplink, 20
- Bandwidth: 900 MHz each channel, 2.7 GHz total.
- RF Power: 46 Watts/Channel.
- Redundancy: 1 standby channel (4 for 3 redundancy).
- Coverage: Two contiguous sectors in north-eastern
U.S. plus sixteen isolated spot beams covering selected
U.S. locations. Also full visible earth coverage via mechanically-steerable
- Receive Antenna: 2.2-m dish and 1-m steerable.
- Transmit Antenna: 3.3-m dish and 1-m steerable.
- EIRP: Isolated spot beams: 65 dBW; contiguous
sectors: 60-65 dBW; steerable beam: 57 dBW.
- Receiver Noise Figure: 3.4 dB High Electron Mobility
- On-Board Switching: High speed programmable 3
x 3 switch matrix to provide three input and three output
channels with 900 MHz bandwidth. Baseband processor provides
demodulation, storage and remodulation of Low Burst Rate
(LBR) data using two 110 Mbps TDMA/DAMA data streams assignable
in increments of 64 kbits.
- Fade Beacons: Stable signals radiated from satellite
in the uplink (30 GHz) and downlink (20 GHz) frequency bands
to permit link fade measurements.
Electrical Power Distribution
- Solar Array Output: 1418 watts (4 years).
- Battery System: 2 nickel-cadmium (NiCd) batteries
of 19 Amp-hours (AH) each. No payload operations during
- Power Bus: 35.5 (+/- 0.5) volts with full array illumination.
Propulsion and Orbit Control
- Design: Blowdown hydrazine system with redundant
thrusters and four tanks.
- Propellant: 580 lbs. (at launch).
- Thrusters: 16 (0.2,0.5, and 1.0 lbf).
- Stationkeeping: No longer maintained. (+/- 0.05
degrees when it was maintained).
Structure and Thermal
- Structure: Length: 80", width: 84", depth:
- Solar Array: With yoke, 46.9' tip-to-tip
- Antenna Assembly: Height 116" above antenna
panel; width: 29.9' deployed.
- Thermal Control: Passive temperature control:
blankets and Optical Solar Reflectors (OSR); active temperature
control: solid state controllers and heaters.
- Transfer Orbit Control: Autonomous nutation control
during spin; initial pointing provided by Transfer Orbit
Stage (TOS) booster.
- On-Orbit Control: 3-axis stabilized via earth
and sun sensor and momentum wheel. Autotrack reference used
during payload communications usage periods.
- Pointing Accuracy: 0.025 degree pitch and roll,
0.15 degree yaw using autotrack; 0.1 degree pitch and roll,
0.25 degree yaw using earth sensor.
- Offset Pointing Control: +/-6 degree pitch; +/-2
Command, Ranging and Telemetry
- Command Frequency: Ka-band primary; C-band backup
and during transfer orbit.
- Command Rate: 100 pps FSK for bus functions; 5000
pps SGLS for payload.
- Command Capacity: 379 low rate discretes; 3 serial
low rate data streams; 256 high rate discretes; 3 serial
high rate data streams.
- Telemetry Frequency: Ka-band; C-band backup and
during transfer orbit.
- Telemetry Format: 8 nits/word; 256 words/minor
frame; 25 minor frames/major frame; 1024 bps.
- Telemetry Capacity: 312 bilevel words; 364 analog
words; 6 serial words; dwell capability on any analog, bilevel
or serial word.
- Tracking Frequency: Ka-band; C-band backup and
during transfer orbit.
- Tracking Tones: 4 from 35.4 Hz to 27.777 kHz.