IN DEPTH: The Cost of Saving Hubble

Nov. 1, 2006 — Nowhere will the challenge, risks and rewards of flying space shuttles be more apparent than when NASA undertakes a final servicing call to the Hubble Space Telescope.

After years of debate and technical reviews, NASA administrator Mike Griffin announced on Tuesday the benefits of extending the life of the world's premier space observatory are worth the time, trouble and about $900 million in costs to the U.S. space agency.

Without upgrades by a shuttle crew, Hubble likely would last only another two or three years.

Hubble's good fortune rests squarely upon NASA's commitment to finish building the International Space Station. Completing the station was the sole reason why the shuttle fleet was returned to flight following the 2003 Columbia disaster.

With the shuttles’ days numbered and no other vehicles existing or planned that can haul the station’s components to orbit, NASA is taking a risk by adding any extra missions to the fleet’s manifest.

"Flying the shuttle carries with it more risk than we would like, more risk than we once thought we had," Griffin said. "It can be flown safely if we are very careful."

What goes unsaid, is another shuttle accident or serious problem would likely end NASA's efforts to finish the $100-billion station, which is a joint project of the United States, Russia, Europe, Japan and Canada.

NASA replaced shuttle Challenger, which was lost in a 1986 launch accident, with a new shuttle, Endeavour. Columbia's demise, however, spurred the United States to set a 2010 retirement date for the remaining ships and redirect human spaceflight programs toward lunar and eventual Mars expeditions.

Griffin acknowledged the station's completion supercedes plans to extend Hubble's life, but said there should be ample time before the final shuttle flight in 2010 to handle both jobs.

The Hubble mission is targeted for May 2008. By that time, NASA, which so far has completed one of 15 missions essential for station construction, should have completed seven more station missions.

NASA planning documents show that they will have delivered and installed Europe’s Columbus laboratory module and finished two of three missions earmarked for Japan's Kibo complex.

Also in 2008, shuttle Atlantis is slated to become the first of the three remaining shuttles to be removed from service.

Servicing Hubble will temporarily tie up not just one shuttle, but a second ready to fly an emergency rescue mission.

After the Columbia accident, NASA set up the station to serve as an orbital safe haven in case a shuttle should become too damaged to safely return home. Shuttles flying to Hubble's orbit, however, cannot reach the station.

Instead, the shuttle used for Hubble's mission, which likely would be Discovery, will carry enough fuel and supplies to remain in orbit for up to 25 days if needed, giving NASA enough time to mount a rescue mission.

A second space shuttle will be at the launch pad at the time the Hubble mission is launched, Griffin said.

This decision will complicate plans to turn over one of the shuttle's two launch pads for modifications needed to support the shuttle replacement vehicle. The first test flight for the rocket being designed to carry the Crew Exploration Vehicle (CEV), is slated for April 2009.

Despite such complications, Griffin’s decision suggests the mission will be worth the extra work. And crewmembers tapped to make the final house call to Hubble say the mission is also worth the extra risk of embarking on a mission without the safe haven of a nearby space station. 

"I feel like a mission to Hubble is worth risking my life for. It's something that's really important for our country and I firmly believe the next mission to Hubble will be much safer than the missions we've flown before," said astronaut John Grunsfeld, one of three veterans of NASA's last Hubble servicing flight in 2002 who were named to the new crew.

During the planned 11-day flight, astronauts will make up to five spacewalks to install two new science instruments, repair a third instrument, replace spent batteries and swap out gyroscopes used to point Hubble at targets for observations.

Rather than attach a propulsion module needed to safely steer Hubble from orbit once its mission is over, the crew will attach a multi-use docking system so that a CEV or another rocket can make that delivery at some point in the future. Originally, Hubble was designed to be grappled and serviced only by the shuttle.

NASA eventually will want to assure that Hubble re-enters the atmosphere over water to avoid crashing down in populated areas. This will take a rocket, but with Hubble's orbit expected to remain stable until at least 2020, Griffin said there was no need for a Hubble rocket now.

In fact, Ed Weiler, head of NASA's Goddard Space Flight Center in Greenbelt, Md., which oversees Hubble, foresees a long life ahead for the telescope. He said it likely won’t need a rocket for de-orbit until 2020 or 2025.

By then, there should be other vehicles that can help the famous telescope retire.

"If the CEV (Crew Exploration Vehicle) can go to the moon, it can probably take up a solid rocket motor to Hubble," he said.