NASA Deciding Whether to Close a Window Into Space

A new Hubble image -- among the largest ever produced with the Earth-orbiting observatory -- gives the most detailed view so far of the entire Crab Nebula. Such images are hailed as indicative of Hubble's scientific value. (Jeff Hester -- Arizona State University Via Nasa And European Space Ageny)

As a result, the crew of a Hubble-bound shuttle has only about three weeks' time to repair any damage to the spaceship. That would hardly leave time for the final contingency, preparing and launching a second shuttle for a rescue mission.

"We've had three successful shuttle missions since Columbia, and we've learned a lot about inspecting and repairing the vehicle," NASA spokesman Allard Beutel said. "So we have a lot more capability and flexibility, but clearly some safety issues remain."

Griffin met with his top lieutenants Friday for a final discussion of whether the mission can be done safely and without too much disruption to the space station assembly schedule.

Reflecting Griffin's hope to make room for the mission, a Hubble launch has been penciled in for spring 2008, though officials say the date is a place-holder rather than a sign that a positive decision has been made.

The Hubble, which has been repaired and upgraded four times by astronauts since it was launched in 1990, has had a remarkable record of scientific breakthroughs.

Because it orbits 380 miles above Earth, away from the haze of the atmosphere, it can identify and photograph distant galaxies and matter never before examined. Astronomers have used Hubble images to fix the age of the universe at 13.7 billion years, to discover massive black holes at the center of many galaxies, and to explore a mysterious force called dark energy, which, by acting against the forces of gravity, is causing the universe to expand. Livio of the Space Telescope Science Institute said dark energy is probably the most significant issue in physics today, and losing Hubble would freeze promising research into its nature for as much as a decade.

But some believe Hubble's greatest accomplishment lies in a less rarified realm -- that it has greatly popularized astronomy with its stunning and awe-inspiring images of the universe.

Each of the four earlier Hubble repair missions included some upgrading of instruments, and a possible fifth mission would similarly increase its capacities. Two powerful -- and very expensive -- instruments have been manufactured specifically for the Hubble. They would greatly increase the telescope's ability to look deep into space and to study the chemical composition of the far-distant gas between galaxies.

Livio said the unprecedented power of the new Wide Field Camera 3 would, for instance, enable astronomers to learn about even earlier phases of the universe's formation by making observations in the infrared and ultraviolet wavelengths. The new Cosmic Origins Spectrograph will examine the subatomic baryon particles that inhabit the space between galaxies. The instruments cost $200 million and may have no other use if they cannot be delivered to the Hubble, Livio said.

If Hubble is not repaired, NASA estimates that it will probably keep working into 2008 or 2009. The James Webb Space Telescope, a replacement of sorts but with different capabilities, is scheduled to be launched in 2013.

NASA officials say the Hubble repair decision will be made on the basis of safety, engineering and scheduling concerns, but it will also say a lot about NASA's priorities. The speed-up in assembly of the space station is both because it is well behind schedule, and because NASA is eager to get out of the space shuttle business so it can focus on President Bush's initiative to return to the moon by 2020 and then explore Mars.

The costs of both the shuttle program and the new manned exploration mission are great, and NASA has said the basic science budget will grow more slowly or be cut as a result. Because the telescope is one of the gems of the NASA science directorate, some see the fate of Hubble as indicative of where the agency is headed.

"This is a terribly important decision, and it has so many political and scientific overtones," said J. Craig Wheeler, astronomy professor at the University of Texas at Austin and president of the American Astronomical Society.

"It's very important for those who want to continue working with Hubble, important for those who want to do other space science, and it's important as an indication of that evolving balance between space science and human space exploration," he said. "And it shows that NASA has an enormous number of big issues on its plate right now."