‘Zombie’ craft may still interfere
September 23, 2010
Intelsat’s Galaxy 15 communications satellite, dubbed the “zombie satellite,” lost contact with its controllers in April but is stuck “on” and continues to transmit signals as its operators on Earth work to avoid potential interference with other nearby spacecraft. Galaxy 15 passed Anik F2 without harm on Sept 9, which suggests that Intelsat’s engineers have become extremely efficient at performing a sort of celestial ballet as they avoid potentially catastrophic situations.
Intelsat engineers had estimated – or hoped – that the satellite would lose power and shut itself off in late August, but that has not happened. “It has not powered down yet, and it continues to drift — but we still know where it’s going, and it’s still following a predictable path,” Intelsat spokesman Nick Mitsis said. Galaxy 15 was launched to 133 deg West back in October 2005, and control was lost in April 2010 with the blame centred on a damaging and powerful solar flare which happened at the same time.
Since then the satellite has drifted at a very steady rate of some 0.16 degrees East per day, and over the past few months has drifted alongside Galaxy 13, Galaxy 14 and an EchoStar and DirecTV craft. Some satellites within its path cause no transmission problem because they are using either different frequencies or have their beams focused on a region outside the continental USA. For example, it is now in the vicinity of SatMex 5, but while engineers will be monitoring the situation extremely closely there will be little or no risk of interference. Sirius/XM’s XM4 is the next in line, then SatMex 6.
The next few weeks or so will therefore see Galaxy 15 pass Anik F2, the two EchoStar craft at 110 deg West, and DirecTV 5. Two more Aniks (F1 and F1R) will need to be avoided at 107.3 degrees, but they are many weeks away in terms of Galaxy 15’s possible route.
Intelsat officials stress there is no risk of it physically colliding with other spacecraft, so their team’s main focus is preventing Galaxy 15’s signals from interfering with neighboring satellites. The 4,171-pound satellite has resisted many attempts to shut it down, leaving the defunct satellite stuck drifting in space and still “talking.”
Intelsat’s engineers – and those looking after the other fleets – have their satellites on a very close watch and insist that while the whole episode is regrettable there is absolutely no prospect of an in-orbit collision. Diane vanBeber, Intelsat’s VP/Investor Relations, compared the situation to two mirrors reflecting the same image as one passes the other. “If you’re looking at a mirror, it’s sending its image back to you,” she said. “But if another mirror came around the top of that mirror and was passing by, that would also reflect the image you were sending back as well. When you have two different signals coming down, that creates the interference,” she said.
Ultimately, it is expected that the Intelsat platform will lose the ability to point its solar panels at the Sun and experience total power failure. This could take some months, and as far as Intelsat is concerned cannot happen soon enough. When this ‘failure’ happens the Intelsat engineers will then have a fresh chance to ‘re-boot’ the satellite and possibly recover their valuable asset.