Engineers work to stall Hubble's death

Good news
With the stretch out of Hubble servicing via shuttle astronauts, the vigor of the telescope’s batteries and gyros are central to extending the observatory’s life.

Going to the two-gyro science mode is great news, said James Crocker, vice president of civil space programs at Lockheed Martin Space Systems Company near Denver, Colorado. The firm is part of an on-going industry and government partnership to keep Hubble alive and well.

“The team is used to doing miracles,” Crocker told SPACE.com. The placing of one gyro into storage and saving it was a well-researched and tested plan. As for the gyro, he added: “When it’s running, it is wearing. When it is off, it’s not.”

Moreover, Hubble batteries are also a source of good news. “They are not degrading as fast as we had feared,” Crocker said. Also, past experience with batteries in space suggest that they tend to degrade gracefully, he said, perhaps allowing use of select Hubble instruments instead of all of them at some point.

Working in the cathedral
The Hubble operating and servicing team has been a steady-state activity since the observatory was shuttle-deployed in 1990.

“People are constantly pulling rabbits out of the hat. Hubble is like working in the cathedral. There’s a very dedicated group of people who just aren’t going to let Hubble go quietly in the night,” Crocker said.

Crocker said that NASA chief, Michael Griffin, has the Hubble team marching toward a shuttle servicing mission — given a couple of good shuttle flights. “From an execution point of view, we’re continuing to hold the option open,” he said, “and we’re doing all the steps that we need to do to be ready to go.”

Given Hubble’s batteries and the gyro fixes, “I think we’ve got a nice window” for shuttle servicing, Crocker added, probably no sooner than December 2007 - with a goal of perhaps pulling it in a few months earlier if necessary.

“Everything is being done to get shuttle back into a position where it can service the space station and Hubble,” Crocker explained.

Partial termination
Meanwhile, work on a Hubble deorbit module has been cancelled, Burch said, a task that was underway at Lockheed Martin.

A “Dear Lockheed letter” advising of the stop work on the deorbit module was dated Sept. 2, Burch said. However, that communiqué also called for “partial termination” of some related work by the company.

The contract was not totally cancelled, Burch noted. Lockheed Martin expertise is being requested for both sensor technology ideas and an attachment fixture to be outfitted to Hubble. This fixture could be secured to the telescope by either astronauts or by a robotic mission, he said.

“We thought it smart to do something while we’re up there to make it a lot easier to rendezvous with and grapple Hubble for deorbiting,” Burch said. That might be accomplished by either the Crew Exploration Vehicle meant to replace the shuttle, or by robotic means, he noted.

Furthermore, quite a bit of work had been done by Lockheed Martin on the Hubble deorbit module. The company has been informed that all propulsion hardware that is 75 percent complete or greater should be wrapped up and turned over to the Lunar Reconnaissance Orbiter (LRO) project.

“Scrapping hardware that is three-quarters complete is, I think, sinful,” Burch said. So the plan is to use deorbit module-related valves, thrusters, and other items for the Goddard Space Flight Center-managed LRO project, he said, with the LRO office reimbursing the Hubble project for that hardware.

“Instead of [LRO] building from scratch and having all of our stuff wind up in a scrap pile, we thought that this made some sense,” Burch said.

Eventual destiny
At some point in the future, Hubble will meet its ultimate fate — taking a destructive dive into the Earth’s atmosphere by natural forces or under controlled ditching.

The telescope is not likely to fall back to Earth on its own prior to 2020, according to Nicholas Johnson, NASA Orbital Debris Program Manager and Chief Scientist for Orbital Debris at the NASA Johnson Space Center in Houston, Texas.

The telescope’s reentry could happen a few years earlier, but that depends on the Sun’s activity in future years, Johnson said. Increased output from the Sun expands the Earth’s atmosphere. That creates added drag on Hubble and will hasten its fall from orbit.

Johnson said if another servicing mission is carried out, Hubble would likely be given a small boost in altitude before the shuttle departs the scene. This would further delay a natural reentry of the telescope, he explained.

Burch of Goddard Space Flight Center said that a very conservative estimate of Hubble’s reentry is 2021. Other models predict a historically low solar cycle, putting an on-its-own tumble of the telescope to Earth in 2025, he said, and perhaps out to 2030.

“I think two more decades of flight is a real possibility for Hubble,” Burch advised. “The biggest unknown is how long Hubble is going to live…to continue to produce useful science.

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