Sept 25 1975
From The Space Library
A NASA Atlas-Centaur vehicle launched INTELSAT-IVA F-1 at 8:17 pm EDT from Eastern Test Range into the planned synchronous transfer orbit. The communications satellite had been launched for the Communications Satellite Corp. under a cost-reimbursable contract. At 11:18 pm EDT 26 Sept., ComSatCorp fired the apogee kick motor to put the satellite in a geosynchronous orbit with a 35 821km apogee, 35 294-km perigee, 23-hr 44-min period, and 0.1° inclination.
NASA objectives for the mission were to review design, performance, and flight readiness for the Federal Communications Commission and to assure compatibility of the INTELSAT spacecraft with NASA launch vehicles and launch environmental conditions, and to launch INTELSAT-IVA F-1 into a transfer orbit that would enable the spacecraft apogee boost motor to inject the spacecraft into a synchronous orbit. Objectives were completed and the mission adjudged successful 29 Jan. 1976.
ComSatCorp objectives were to fire the apogee boost motor, position the satellite into the planned geostationary orbit, and operate and manage the system for the International Telecommunications Satellite Organization (INTELSAT).
INTELSAT IVA F-1, built by Hughes Aircraft Co., was 698.5 em high and 238.2 cm in diameter, with a liftoff weight of 1515 kg and orbital weight of 825.5 kg. The spin-stabilized satellite consisted of two main elements: A rotating section contained the power subsystem, a cylindrical solar array and two nickel-cadmium batteries; the anhydrous hydrazine-powered positioning and orientation system; the solid-fueled apogee motor; and the despun-control system. The despun earth-oriented platform section contained the communications repeater, antennas, and associated elements of the telemetry and command subsystems. All spacecraft antennas were supported by a single tubular mast.
For 24 hr after apogee-motor firing, INTELSAT IVA F-1 drifted eastward at a rate of 10° per day; then a velocity-correction maneuver slowed the spacecraft drift to 2.9° east per day. While the spacecraft was drifting, the Hawaii earth station checked out the spacecraft systems. Its final operating location, over the Atlantic Ocean at 335° east longitude, would be reached by mid-December. As primary Atlantic satellite in INTELSAT's global commercial communications satellite system, it would serve more than 40 earth stations, offering users 6250 two-way voice circuits and two TV channels.
INTELSAT IVA F-1 was the first in the INTELSAT IVA series; its communications capacity was two-thirds greater than satellites in the INTELSAT IV series, seven of which were still operating. The INTELSAT system began with the launch of INTELSAT I F-1 (Early Bird 1) on 6 April 1965; since then NASA had launched 16 successful comsats for ComSatCorp in the INTELSAT 11, III, and IV series.
Although INTELSAT IVA satellites had been designed primarily for use over the Atlantic with its heavy communications traffic, INTELSAT planned to launch as many as five additional IVAs, some to provide service for the Pacific and Indian Ocean regions. INTELSAT IVAs had a design lifetime of 7 yr and a capacity sufficient to meet international communications requirements through 1979, when the system would be augmented with the even larger capacity INTELSAT V comsats.
INTELSAT, created in August 1964 by adoption of the Interim Agreements for the Establishment of a Global Commercial Comsat System, now comprised 91 member nations; a 24-member board of governors exercised overall responsibility for design, development, construction, establishment, operation, and maintenance of the INTELSAT space segment. ComSatCorp, a privately owned carrier company operating under a U.S. congressional mandate, had provided technical and operational management services to INTELSAT and the global system under a cost-plus-fixed-fee management services contract.
NASA had been responsible for procuring the Atlas-Centaur launch vehicle, conducting preflight testing, and launching the spacecraft from the Eastern Test Range into a synchronous transfer orbit. ComSatCorp engineers in the INTELSAT Spacecraft Technical Control Center in Washington, D.C., then assumed responsibility for the mission.
Overall management for the NASA portion of the mission was under the direction of the Office of Applications. Lewis Research Center was responsible for Atlas-Centaur development and operation. Kennedy Space Center was responsible for vehicle checkout and for launch. (NASA MORs E-491-633-75-01, 25 Sept 75, 30 Jan 76; NASA Release 75-231; INTELSAT Releases, 21 Sept 75, 1 Sept 75; Singer, Today, 26 Sept 75; NASA PIO, interview, 26 Sept 75; GSFC Wkly SSR, 25 Sept-1 Sept 75)
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