Start Date

4-1968 8:00 AM

Description

Syncom 3, launched in August 1964, was the first satellite to be maneuvered to a nearstationary orbit. It is presently functioning as an essential communication link between Hawaii and the Far East, As long as the satellite remains within mutual visibility of these areas, this link will continue to exist. Ironically, the by-product of an unwanted process, namely, gas resulting from decomposition of the propellant (hydrogen peroxide) which was originally intended to provide orbital control, is now being used to maintain this link. If the satellite orbit were not controllable, Syncorn 3 would drift out of the mutual visibility longitude band as a result of forces exerted by the earth's triaxiality, The unstable equilibrium longitude in the Pacific, computed to be at 162.4 °E, lies within this band. Near this point, the control velocity requirements are small, so that minimal control capability, such as is available from the gas, could extend Syncom 3's orbital life for as much as 10 years. This is unlikely, however, because of the degraded condition of the batteries which are essential for operation of the control jets. The satellite on its present drift trajectory should remain visible from Hawaii until early 1969.

Longitudinal control of Syncom 3 in the vicinity of the Pacific equilibrium longitude has now been accomplished with gas for approximately 1.5 years. The specific impulse observed is approximately 57.1 seconds. The mass flow rates observed have resulted in velocity increments of about 0.005 fps per pulse, Such high resolution is required to maintain the satellite position close to but west of the equilibrium longitude. This constraint is based on the increased, visibility time for westerly drift in case of complete loss or depletion of control capability. Since the batteries are weak and gas leaks are to be expected in a system not originally designed for use of gas, such a constraint is reasonable.

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Apr 1st, 8:00 AM

Extending Syncom 3's Orbital Life Over the Pacific

Syncom 3, launched in August 1964, was the first satellite to be maneuvered to a nearstationary orbit. It is presently functioning as an essential communication link between Hawaii and the Far East, As long as the satellite remains within mutual visibility of these areas, this link will continue to exist. Ironically, the by-product of an unwanted process, namely, gas resulting from decomposition of the propellant (hydrogen peroxide) which was originally intended to provide orbital control, is now being used to maintain this link. If the satellite orbit were not controllable, Syncorn 3 would drift out of the mutual visibility longitude band as a result of forces exerted by the earth's triaxiality, The unstable equilibrium longitude in the Pacific, computed to be at 162.4 °E, lies within this band. Near this point, the control velocity requirements are small, so that minimal control capability, such as is available from the gas, could extend Syncom 3's orbital life for as much as 10 years. This is unlikely, however, because of the degraded condition of the batteries which are essential for operation of the control jets. The satellite on its present drift trajectory should remain visible from Hawaii until early 1969.

Longitudinal control of Syncom 3 in the vicinity of the Pacific equilibrium longitude has now been accomplished with gas for approximately 1.5 years. The specific impulse observed is approximately 57.1 seconds. The mass flow rates observed have resulted in velocity increments of about 0.005 fps per pulse, Such high resolution is required to maintain the satellite position close to but west of the equilibrium longitude. This constraint is based on the increased, visibility time for westerly drift in case of complete loss or depletion of control capability. Since the batteries are weak and gas leaks are to be expected in a system not originally designed for use of gas, such a constraint is reasonable.

 

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