Encyclopedia Astronautica
ACTS



acts.jpg
ACTS
American communications technology satellite. One launch, 1993.09.12. NASA experimental communications; Advanced Communications Technology Satellite.

ACTS was developed as an experimental on-orbit, advanced communications satellite test bed, bringing together industry, government, and academia to conduct a wide range of technology, propagation, and user application investigations. NASA Glenn Research Center awarded in August 1984 the ACTS contract to an industry team consisting of: Lockheed Martin, East Windsor, NJ for system integration and the spacecraft bus; TRW, Redondo Beach, CA for the spacecraft communications payload; COMSAT Laboratories, Clarksburg, MD for the network control and master ground station; Motorola, Chandler, AZ for the baseband processor; and Electromagnetic Sciences, Norcross, GA for the spot-beam forming networks.

The contract was awarded to RCA Astro Space of East Windsor, NJ, which was subsequently acquired by General Electric, and then by Martin Marietta (itself acquired by Lockheed Aircraft Corporation in 1995 to become Lockheed Martin). In 1988, as a result of a congressionally mandated program funding cap, Lockheed Martin assumed responsibility for completing the development of the communications payload. Subsequently, Lockheed Martin (then General Electric Astro Space) subcontracted with Composite Optics, Inc. San Diego, CA for the manufacture of the antenna reflectors and part of the bus structure.

ACTS was launched as the primary payload aboard the Space Shuttle Discovery (OV-103) from the Kennedy Space Center, Pad 39B, as part of the STS-51 mission on September 12, 1993. At launch and for insertion into its geosynchronous orbit, ACTS was mated to the transfer orbit stage component (TOS) for a total weight of 6108 lbs.

On separation from the shuttle orbiter, the TOS was ignited to inject ACTS into geotransfer orbit. The TOS then separated from ACTS. At approximately 50.5 hours into the mission, the apogee kick motor injected ACTS into drift orbit. After seven days, ACTS, guided by the firing of spacecraft thrusters, moved into its operations orbit and transitioned to a stabilized spacecraft configuration. Before the payload was actuated, the solar arrays were deployed, earth-sun attitude control was established, and the main communication antennas were deployed.

ACTS was stationed at its designated geosynchronous orbit location at 100 degrees west longitude. In July 1998 the spacecraft's north/south station keeping was stopped to extend operations in an inclined orbit. In August 2000, the satellite was moved to 105.2 W longitude to be permanently located.

The weight of ACTS at the beginning of its on-orbit life was 3250 lbs. At full deployment, it measured 47.1 feet from tips to tip of its solar arrays and 29.9 feet across from its main receiving and transmitting antenna reflectors.

Experimental studies began twelve weeks after ACTS was deployed. The communications payload continued to operate flawlessly 24 hours per day, seven days per week, year round. The only periods of "down time" occurred during parts of the spring and fall equinox periods when the ACTS' solar panels were eclipsed. Experimentation supported by ACTS continued until June 2000. In May 2001, the Ohio Consortium for Advanced Communications Technology began using ACTS for educational research.

Specification

  • Type: 3-axis stabilized experimental communications technology satellite.
  • 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 degrees west.
  • Design Life: 4 Years.

Communications Payload

  • Frequency: 3 Ka-band channels, 30 GHz uplink, 20 GHz downlink.
  • 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 spot beam.
  • 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 Transistor (HEMT).
  • 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 provided 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 eclipse.
  • 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).
  • Station keeping: No longer maintained. (+/- 0.05 degrees when it was maintained).

Structure and Thermal

  • Structure: Length: 80", width: 84", depth: 75".
  • 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.

    Attitude Control

      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 degree roll.

    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 bi-level words; 364 analog words; 6 serial words; dwell capability on any analog, bi-level 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.

    Gross mass: 2,767 kg (6,100 lb).
    First Launch: 1993.09.12.
    Number: 1 .

    More... - Chronology...


    Associated Countries
    See also
    • Shuttle The manned reusable space system which was designed to slash the cost of space transport and replace all expendable launch vehicles. It did neither, but did keep NASA in the manned space flight business for 30 years. More...

    Associated Launch Vehicles
    • Shuttle American winged orbital launch vehicle. The manned reusable space system which was designed to slash the cost of space transport and replace all expendable launch vehicles. It did neither, but did keep NASA in the manned space flight business for 30 years. Redesign of the shuttle with reliability in mind after the Challenger disaster reduced maximum payload to low earth orbit from 27,850 kg to 24,400 kg. More...

    Associated Manufacturers and Agencies
    • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...

    Bibliography
    • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
    • JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: here.
    • McDowell, Jonathan, Launch Log, October 1998. Web Address when accessed: here.
    • NASA Report, The Advanced Communications Technology Satellite (ACTS): A Switchboard in the Sky, Web Address when accessed: here.
    • NASA Report, ACTS Mobile SATCOM Experiments, Web Address when accessed: here.
    • NASA Report, ACTS Ka-Band Earth Stations: Technology, Performance, and Lessons Learned, Web Address when accessed: here.
    • NASA Report, ACTS: Technology Description and Results, Web Address when accessed: here.
    • NASA Report, A Quantitative Review of ACTS Experiments Operations, Web Address when accessed: here.
    • NASA Report, ACTS systems overview, Web Address when accessed: here.

    Associated Launch Sites
    • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
    • Cape Canaveral LC39B Shuttle, Saturn V, Saturn I launch complex. LC39A and LC39B, part of the Kennedy Space Center, were built on Merritt Island (north/northwest of the Cape) to support the Saturn V/Apollo lunar landing program in 1963-1966. The sites were modified in the last half of the 1970s to support the manned Space Shuttle program. More...

    ACTS Chronology


    1993 September 12 - . 11:45 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC39B. LV Family: Shuttle. Launch Vehicle: Shuttle. LV Configuration: Space Shuttle STS-51.
    • ACTS - . Payload: Discovery F17 / ACTS [TOS-21H] / Orfeus-SPAS 01. Mass: 2,767 kg (6,100 lb). Nation: USA. Agency: NASA Cleveland. Class: Communications. Type: Civilian communications satellite. Spacecraft: ACTS. USAF Sat Cat: 22796 . COSPAR: 1993-058B. Apogee: 35,806 km (22,248 mi). Perigee: 35,767 km (22,224 mi). Inclination: 3.2000 deg. Period: 1,436.10 min. NASA experimental communications; Advanced Communications Technology Satellite; deployed from STS-51 9/12/93; 100 deg W. Positioned in geosynchronous orbit at 100 deg W in 1993-1999 105 deg W in 2000. As of 5 September 2001 located at 105.36 deg W drifting at 0.007 deg W per day. As of 2007 Mar 10 located at 105.14W drifting at 0.004W degrees per day.

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