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The Hubble Space Telescope repair mission, STS-125 seemingly gets bad news after more bad news. The mission was already delayed due Hurricane Ike in 2008, and again when a data handling processor on the spacecraft failed. Now, the mission may be too risky for both spacecraft and astronauts following the collision of the Iridium satellite and a defunct Russian communications spacecraft last week. There may be too much debris floating around close to Hubble’s orbit, breaching the safety limits NASA has in place. Without a servicing mission by a space shuttle crew, currently targeted for launch in May, the telescope is not expected to last more than another year or two.
Astronauts on spacewalks are even more at risk than the shuttle or even Hubble, and there are five spacewalks planned during the Hubble servicing flight to replace the telescope’s batteries, install new science instruments (including a new camera) and re-apply radiation shielding.
Hubble orbits higher than the International Space Station, closer to the cloud of debris from the collision. Even before the collision, the probabilities of a debris strike for the Hubble mission were already close to NASA’s safety limit. NASA pegged the chance of a catastrophic impact to a shuttle in Hubble’s orbit at 1 in 185, just below its limit of 1 in 200.
Other debris in that orbit includes pieces of a satellite that China blew up in 2007 as part of a missile test, adding hundreds of pieces of potentially hazardous debris.
Mark Matney, an orbital-debris specialist at the Johnson Space Center in Houston, told Nature magazine that even before last week’s crash the risk of a debris impact for the shuttle already “uncomfortably close to unacceptable levels. This is only going to add on to that.”
A decision about whether to proceed with the Hubble repair mission could be made in the next week or two, Nature reports.
Sources: Discovery News, Nature