NASA chief to reveal decision on Hubble mission Tuesday
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: October 27, 2006
Editor's note...Portions of this story first ran last December.
Griffin will announce a decision on whether to reinstate a Hubble servicing mission during a news conference Tuesday at the Goddard Space Flight Center in Greenbelt, Md. If he approves the flight, another briefing will be held at the Johnson Space Center in Houston to introduce the astronauts who will fly the mission.
O'Keefe's much-criticized January 2004 decision to call off Servicing Mission 4 (SM-4) was based in large part on recognition that a Hubble repair crew could not seek "safe haven" aboard the international space station in case of major problems with the shuttle that might prevent a safe re-entry. The two spacecraft circle the globe in very different orbits and shuttles cannot carry enough fuel to move from one to the other.
But Griffin has made no secret of his desire to reverse O'Keefe's decision.
"For any given single mission, I would say that the Hubble servicing represents the highest priority utilization of a single shuttle mission that I can conceive," Griffin said in an interview late last year. "Because servicing the Hubble is something only the shuttle can do, it's only one flight and is, therefore, I think a very high agency priority if we can do it technically."
Without a servicing mission to replace Hubble's aging batteries and stabilizing gyroscopes, one of the most scientifically significant satellites ever launched will die in the next few years. Given that two new instruments are already built that will extend Hubble's scientific reach, supporters are urging Griffin to reinstate the mission.
They argue the success of three post-Columbia missions proves NASA has dramatically lowered the risk of external tank foam insulation problems like those blamed for Columbia's demise.
Carrying the same heat shield inspection boom and sensors that station flights carry, Discovery's crew will be able to inspect all critical areas on the shuttle before rendezvousing with Hubble and again, after Hubble is released. If impact damage is found, the crew will have improved repair materials and techniques at their disposal.
But flying in Hubble's orbit, the servicing crew would be exposed to a greater chance of micrometeoroid impacts. During a shuttle flight in September, a small object hit a payload bay door radiator and while it didn't cause any problems for the mission, it illustrated the threat posed by space debris.
That threat, while higher for a Hubble mission, is offset somewhat by reduced risk in other areas. But what if non-repairable damage is discovered? One of the options Griffin will consider is whether to process a second shuttle in parallel to serve as a "launch-on-need" rescue ship that would eliminate concern about the lack of safe haven aboard the station.
To provide enough time for a rescue mission to be launched, the Hubble crew would take off with additional supplies of lithium hydroxide, a chemical used to scrub carbon dioxide form the shuttle's air supply. Those additional supplies would permit a Hubble crew to remain in orbit aboard a damaged ship for 25 days or more.
If two shuttle pads are available, planners believe a rescue flight could be launched with a week of the Hubble launch. If only one pad is available - and NASA currently plans to turn pad 39B over to the Constellation moon-Mars program next year - the best-case turnaround time is about 15 days.
In one scenario, sources say, the rescue shuttle would be moved to the launch pad, loaded with internal rocket fuel and then moved back to the Vehicle Assembly Building to make way for the Hubble launch. If a problem developed in orbit, the rescue shuttle then could be moved back out to the pad and quickly launched.
But any launch-on-need capability would effectively take two space shuttles out of the space station assembly flow, delaying downstream flights from one to several months.
In addition, manpower and hardware processing issues at the Kennedy Space Center make the current April 2008 target date unlikely, engineers say. A more realistic target is the summer of 2008.
In any case, Griffin must balance the threat of delays, additional costs and increased risk with the high value of servicing a telescope that is arguably the most significant scientific satellite ever launched.
When Columbia blasted off on Jan. 16, 2003, Servicing Mission 4 was scheduled for takeoff in early 2005. The major objectives of the flight were to install two new scientific instruments, to replace the observatory's batteries and to install a fresh set of gyroscopes.
O'Keefe's cancellation of SM-4 in January 2004 touched off a storm on protest, prompting NASA to look into the feasibility of an robotic servicing mission.
The goals of the unmanned mission included the attachment of a propulsion module that could drive Hubble to a safe, targeted re-entry at the end of its useful life. But such a robotic flight ultimately was deemed too technically risky and too expensive.
With relatively minor exceptions, the goals of the currently envisioned shuttle mission are virtually unchanged from the flight O'Keefe cancelled: