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Space


Commercial Communications Satellites

  • 1Worldspace
  • Astro Digital
  • Bigelow Aerospace
  • BlackSky Global
  • DirecTV
  • Echostar
  • Globalstar
  • Hughes
  • Intelsat, Ltd.
  • Iridium
  • Millennium Space
  • ORBCOMM
  • PanAmSat
  • Planet Labs, Inc.
  • SES
  • SES World Skies
  • Sirius XM Holdings
  • Spire Global Inc.
  • ViaSat, Inc.
  • XM Satellite Radio


  • DEFUNCT SYSTEMS
  • GE Americom
  • Alascom
  • AT&T
  • COMSAT
  • GTE


  • Non-GSO



    VAPORWARE
    1996 - Mega LEO
  • Sativod
  • Teledesic
  • 1996 - Big LEO
  • AMSC
  • Constellation
  • Ellipso
  • Globalstar
  • ICO
  • Iridium
  • Odyssey
  • 1996 - Little LEO
  • E-Sat
  • FAISAT
  • GE Americom
  • GEMNET
  • Starsys
  • Leo One USA
  • Orbcomm
  • Vitasat


  • Satellite communications is the only truly commercial space technology- -generating billions of dollars annually in sales of products and services. In fall of 1945 an RAF electronics officer and member of the British Interplanetary Society, Arthur C. Clarke, wrote a short article in Wireless World that described the use of manned satellites in 24-hour orbits high above the world's land masses to distribute television programs. Arthur C. Clarke's 1945 vision was of a system of three "manned" satellites located over the major land masses of the earth and providing direct-broadcase television. His article had little immediate effect in spite of Clarke's repeating the story in his 1951/52 The Exploration of Space.

    Perhaps the first person to carefully evaluate the various technical options in satellite communications and evaluate the financial prospects was John R. Pierce of AT&T's Bell Telephone Laboratories who, in a 1954 speech and 1955 article, elaborated the utility of a communications "mirror" in space, a medium-orbit "repeater" and a 24-hour-orbit "repeater." In comparing the communications capacity of a satellite, which he estimated at 1,000 simultaneous telephone calls, and the communications capacity of the first trans-atlantic telephone cable (TAT-1), which could carry 36 simultaneous telephone calls at a cost of 30-50 million dollars, Pierce wondered if a satellite would be worth a billion dollars.

    Because of Congressional fears of "duplication," NASA confined itself to experiments with "mirrors" or "passive" communications satellites (ECHO), while the Department of Defense was responsible for "repeater" or "active" satellites which amplify the received signal at the satellite--providing much higher quality communications. In 1960 AT&T filed with the Federal Communications Commission (FCC) for permission to launch an experimental communications satellite with a view to rapidly implementing an operational system.

    By the middle of 1961, NASA had awarded a competitive contract to RCA to build a medium-orbit (4,000 miles high) active communication satellite (RELAY); AT&T was building its own medium-orbit satellite (TELSTAR) which NASA would launch on a cost-reimbursable basis; and NASA had awarded a sole- source contract to Hughes Aircraft Company to build a 24-hour (20,000 mile high) satellite (SYNCOM). The military program, ADVENT, was cancelled a year later due to complexity of the spacecraft, delay in launcher availability, and cost over-runs.

    By 1964, two TELSTARs, two RELAYs, and two SYNCOMs had operated successfully in space. This timing was fortunate because the Communications Satellite Corporation (COMSAT), formed as a result of the Communications Satellite Act of 1962, was in the process of contracting for their first satellite. COMSAT's initial capitalization of 200 million dollars was considered sufficient to build a system of dozens of medium-orbit satellites. For a variety of reasons, including costs, COMSAT ultimately chose to reject the joint AT&T/RCA offer of a medium-orbit satellite incorporating the best of TELSTAR and RELAY. They chose the 24-hour-orbit (geosynchronous) satellite offered by Hughes Aircraft Company for their first two systems and a TRW geosynchronous satellite for their third system. On April 6, 1965 COMSAT's first satellite, EARLY BIRD, was launched from Cape Canaveral. Global satellite communications had begun.

    In the mid-1970s several satellites were built using three-axis stabilization. They were more complex than the spinners, but they provided more despun surface to mount antennas and they made it possible to deploy very large solar arrays. The greater the mass and power, the greater the advantage of three-axis stabilization appears to be. Perhaps the surest indication of the success of this form of stabilization was the switch of Hughes, closely identified with spinning satellites, to this form of stabilization in the early 1990s. The latest products from the manufacturers of SYNCOM look quite similar to the discredited ADVENT design of the late 1950s.

    Much of the technology for communications satellites existed in 1960, but would be improved with time. The basic communications component of the satellite was thr traveling-wave-tube (TWT). These had been invented in England by Rudoph Kompfner, but they had been perfected at Bell Labs by Kompfner and J. R. Pierce. All three early satellites used TWTs built by a Bell Labs alumnus. These early tubes had power outputs as low as 1 watt. Higher- power (50-300 watts) TWTs are available today for standard satellite services and for direct-broadcast applications.

    An even more important improvement was the use of high-gain antennas. Focusing the energy from a 1-watt transmitter on the surface of the earth is equivalent to having a 100-watt transmitter radiating in all directions. Focusing this energy on the Eastern U.S. is like having a 1000-watt transmitter radiating in all directions. The principal effect of this increase in actual and effective power is that earth stations are no longer 100-foot dish reflectors with cryogenically-cooled maser amplifiers costing as much as $10 million (1960 dollars) to build. Antennas for normal satellite services are typically 15-foot dish reflectors costing $30,000 (1990 dollars). Direct-broadcast antennas will be only a foot in diameter and cost a few hundred dollars.

    Cellular telephony has brought us a new technological "system"-- the personal communications system (PCS). In the fully developed PCS, the individual would carry his telephone with him. This telephone could be used for voice or data and would be usable anywhere. Several companies have committed themselves to providing a version of this system using satellites in low earth orbits (LEO). These orbits are significantly lower than the TELSTAR/RELAY orbits of the early 1960s. The early "low-orbit" satellites were in elliptical orbits that took them through the lower van Allen radiation belt. The new systems were in orbits at about 500 miles, below the belt. The most ambitious of these LEO systems is Iridium, sponsored by Motorola.

    By the mid-1990s, three categories of systems were proposed. Little LEOs were intended to provide mobile data messaging and position determination services on a global level, while Big LEOs will add mobile voice and fax capabilities; Mega LEOs will provide wireless video, voice, and broadband, high-speed data services to small satellite dishes.

    Spectrum availability and "market timing" concerns (relative to alternative services) have emerged as critical issues facing the proposers of Little LEO systems (particularly in view of the WRC-95 decision not to allocate additional worldwide spectrum to such services). For several reasons, all of these factors remain important considerations in assessing Mega LEO providers, though 400 MHz of spectrum was allocated to such services at WRC-95 (alleviating some spectrum concerns for the time being).



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    Page last modified: 03-04-2018 18:16:42 ZULU