Advanced Communications Technology Satellite (ACTS)
The Advanced Communications Technology Satellite (ACTS) 1,2,3,4 was a NASA technology-demonstration spacecraft launched in September 1993 to validate advanced satellite communications concepts. ACTS was the first satellite to demonstrate an all-digital, onboard-processed, gigabit-class communications architecture operating in the Ka-band, with uplinks at 30 GHz and downlinks at 20 GHz. The spacecraft was launched aboard Space Shuttle Discovery and subsequently transferred to geostationary orbit.
ACTS had a launch mass of approximately 1,475 kg and employed deployable solar arrays spanning about 14.3 m, providing roughly 1.4 kW of electrical power. Its communications payload used a 2-m receive antenna and a 3-m transmit antenna and included beacon transmitters at 20.2 GHz and 27.5 GHz for propagation and atmospheric-effects experiments.
ACTS introduced several pioneering technologies, including onboard digital switching and a multibeam antenna system capable of forming reconfigurable high-power spot beams approximately 240 km in diameter, with up to three beams active simultaneously. Although designed for an operational life of 24–48 months, ACTS supported experimental operations for approximately 127 months. A total of 53 ground terminals were deployed, supporting experiments conducted by more than 100 users. Formal experiments concluded on 31 May 2000, with limited operations continuing until spacecraft deactivation on 28 April 2004.
ACTS was stationed in geostationary orbit at approximately 100° W longitude. Following the completion of its experimental mission, the spacecraft was maneuvered to a graveyard (disposal) orbit several hundred kilometers above the geostationary belt. The satellite is no longer operational and remains in an inert disposal orbit.
Notes
- Gilbert, H. A., and Miller, D. E., “The Advanced Communications Technology Satellite (ACTS): An Overview of the System and Experiments,” Proceedings of the IEEE, vol. 85, no. 6, Jun. 1997, pp. 946–960. back
- NASA Lewis Research Center, Advanced Communications Technology Satellite (ACTS) Experiments Results, NASA Reference Publication 1351, Cleveland, OH: NASA Lewis Research Center, 1995. back
- Miller, M. J., “Onboard Processing and Switching for the ACTS Satellite,” IEEE Communications Magazine, vol. 32, no. 7, Jul. 1994, pp. 20–29. back
- Rappaport, T. S., et al., “Wideband Millimeter-Wave Propagation Measurements and Models Using ACTS,” IEEE Transactions on Antennas and Propagation, vol. 40, no. 12, Dec. 1992, pp. 1399–1410. back