Intelsat VI

INTELSAT VI Satellite

The Intelsat VI series of satellites were the 8th generation of geostationary communications satellites for the INTELSAT Corporation. Designed and built by Hughes Aircraft Company (HAC) in 1983-1991, there were five VI-series satellites built 601, 602, 603, 604, and 605.

Design

The Intelsat VI satellites were an extrapolation of Hughes's U.S. Government widebody spacecraft design and features of the Hughes 376 series commercial satellites. This satellite design combined the deploy-able solar array ring of the HS376 extended power spinning satellite, with the wide body deisgn . designed with two C-band hemispherical coverage areas, three or four Ku-band zone coverage areas, and two Ku-band spot coverages.

The Intelsat VI series used a liquid bi-propellant propulsion system. Nickel-hydrogen pressure vessel batteries supplied power during eclipse operation. 50 amplifiers,

The solar array was sized to provide about 2600 Watts of power at the beginning of the satellites lifetime.

Antennas

The C-band coverages were designed to be identical for all satellites. This provided simplicity of design for the five satellites in the series, since all the antenna components could be made identical for each of the five satellites. It also allows for any of the VI series satellites to replace another satellite in case of an on-orbit failure.

A 2.0 m antenna was used for receiving signals transmitted up from the earth. The

The Ku-band zone coverages were optimized for the intended mission/orbital location of each specific satellite. The spot coverages were selectable

to carry 33,000 telephone circuits, the equivalent of 33,000 two way telephone calls, as well as four television channels

Propulsion

The liquid bi-propellant propulsion subsystem provided . The system used nitrogen tetra-oxide and mono-methyl hydrazine. Four radial thrusters (rated at 22 newtons) are used for east-west station keeping, and spin-up/spin-down control. Two 22N axial mounted thrusters provide north-south station keeping and attitude control. Two 490N

Design

The Intelsat VI satellite was designed as a spinning satellite as had many previous satellite designs. The main body of the spacecraft was spun at xx revolutions per minute (rpm) to impart gyroscopic stability to the satellite. A section of the spacecraft supporting the communcations payload and antenna was de-spun to allow the antenna to point at the desired location on the earth.

The Intelsat VI series combined two design features of previous HAC satellites, larger solar array and wide body design. The HS376 extended power spinner satellite had a extra concentric cylindrical solar array which deployed after launch to increase the power generating capability of the satellite, and allow for a larger communications payload. The U.S Government's Widebody Spacecraft was a larger diameter satellite designed to be launched by the Space Transportation System (STS, US Space Shuttle).

This resulted in a spacecraft that was 3.6 meters in diameter and approximately 6.4m tall as configured for launch on an Ariane 4 rocket. When the spacecraft had arrived at its assigned orbital location, the concentric solar array would be extended (deployed), along with deployment of the communications antenna. The spacecraft would then be 11.7m tall.

Intelsat 603

Intelsat 603 was launched by a Titan III on the 14th of March 1990. After the satellite had separated from the Titan launch vehicle the apogee kick motor (APM) was designed to start upon ground command. The APM failed to start and Intelsat 603 was stranded in an elliptical orbit with a low earth perigee that would eventually degrade the satellite orbit and result in the satellite falling into the upper atmosphere of the earth and burning up. Intelsat arranged for a rescue of 603 by the [Space Shuttle| US Space Shuttle]]. STS-xx was launched on xx, xx 1991 and two astronauts successfully captured the satellite by hand after several attempts. After being secured in the Shuttle cargo bay, a new APM was installed. Intelsat 602 was released from the shuttle on xx, xx 1992 and the APM was successfully ignited and 602 was placed into the proper geostationary orbit.