Tim Furniss/LONDON
ASIASAT HAS DELAYED the launch of its Asiasat 2 on a Chinese Long March booster, originally scheduled for this month, until at least the middle of the year while the September 1994 failure of a similar Martin Marietta Astro Space-built satellite, the Telstar 402, is investigated fully.
The Asiasat 2 and AT&T's Telstar, which was lost after a successful Ariane V67 launch into geostationary transfer orbit (GTO), are Satcom 7000-series spacecraft, with identical liquid-apogee engines - an integral part of the spacecraft-propulsion system.
The Hong Kong-based operator has decided to wait until the Martin Marietta investigation is completed, in case hardware changes to the satellite are required. So far, the investigation has "...eliminated more than 600 of the 800 or so possible failure scenarios", says Martin Marietta Astro Space.
"Attention is focusing on the pyro-valves in the propulsion system. It appears the apogee engine was not involved in the failure," says Martin Marietta, adding that the spacecraft "...did not disintegrate and ground-based sensors have determined that it is in an elliptical orbit".
Unofficial reports suggest that the satellite had disintegrated, as loss of contact coincided with the tank pressurisation. Fragments from a satellite break-up in GEO would be difficult to track.
The one large object from the V67 flight being tracked in GTO appears to be the Ariane third stage, which is normally left in this orbit after the launch phase.
Radar cross-section data indicate that the object measures 16.93m2, which compares with the 15.84m2 of a previously identified Ariane third stage.
A typical large satellite of the size of a Telstar 4 measures about 9m2 on a radar cross-section reading. Despite the evidence, Martin Marietta claims that the object in GTO is the Telstar 4 and not the Ariane stage.
Source: Flight International
