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Failed W3B Satellite To Remain in Orbit for Decades
PARIS — The Eutelsat W3B satellite declared a total loss less than 24 hours after its Oct. 28 launch because of a leak in its propulsion system will spend the next 20-30 years in its parking orbit following ground teams’ inability to guide it into a controlled atmospheric re-entry, satellite manufacturer Thales Alenia Space said Nov. 5.
The company said that it has rendered the satellite inert to the extent possible — emptying its helium pressurization tank and whatever fuel remains in liquid state and can be discharged, as well as draining its batteries — to minimize the likelihood that W3B explodes on contact with any orbital debris it may encounter in its elliptical orbit.
The satellite, which weighed 5,370 kilograms at launch, developed a large leak in a line delivering oxidizer to the propellant tank at some point between lifting off aboard an Ariane 5 ECA rocket from Europe’s Guiana Space Center in French Guiana, and when it was released into orbit.
Japan’s BSat-3b telecommunications satellite, which was a co-passenger on the launch, is healthy in orbit and showing no sign that anything was amiss either during the launch or during the satellites’ separation, BSat-3b manufacturer Lockheed Martin Space Systems of Newtown, Pa., announced Nov. 4.
The Arianespace launch consortium of Evry, France, said its analysis of telemetry data from the launch likewise has turned up no evidence of out-of-boundary vibrations during the rocket’s climb through the atmosphere, or any issues during the satellites’ release into their parking orbits.
An Arianespace official said the company, conscious of the questions that its customers may have, has sent written assurances to the owners of satellites on upcoming Ariane 5 launches stating that Arianespace sees no reason to delay the next launch, scheduled for Nov. 25. That launch will carry the Intelsat 17 satellite for Washington- and Luxembourg-based Intelsat, and the Hylas-1 satellite for Avanti Communications of London.
The Thales Alenia Space statement said a board of inquiry has been established to investigate what happened with W3B. The board includes the satellite’s owner, Paris-based Eutelsat, prime contractor Thales Alenia Space, and propulsion system provider Astrium Satellites. Arianespace also is taking part in the inquiry as an observer, mainly to provide telemetry from the launch.
The inquiry is expected to last one month, but may be extended. A preliminary report is expected in mid-November.
In the 24 hours following the launch, Thales Alenia Space and Eutelsat concluded that W3B did not have enough usable propellant to be guided into a graveyard orbit, generally defined as 200-300 kilometers higher than the satellite’s intended operating position 36,000 kilometers above the equator.
The Ariane 5 ECA rocket had dropped off W3B in the specified transfer orbit, with a perigee of 249.2 kilometers and an apogee of 35,907 kilometers. With an orbit-raising maneuver excluded, the manufacturer began designing a series of steps to guide the satellite into the atmosphere, preferably over the southern Pacific Ocean.
But by Nov. 3 the ground controllers concluded that de-orbiting the satellite would not be possible in light of a propulsion situation even more desperate than previously thought. The fuel had begun to freeze, and while the usual partial deployment of the solar arrays provided battery power, the satellite could not be moved.
After performing the propellant purge and other passivation efforts to reduce debris risk, Thales Alenia Space and Eutelsat informed the North American Aerospace Defense Command that W3B should be considered an inert object.
Thales Alenia Space estimated that the satellite’s elliptical orbit, which was not substantially changed in the abortive attempt to achieve ignition, will keep W3B in space for between 20 and 30 years before the natural forces of gravity and the Earth’s residual atmosphere pull it down. While there are not many satellites that have been stranded in this position, there are numerous rocket upper stages that are left there after launch.
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