NASA chief Michael Griffin was expected to announce yesterday whether there will be a final space shuttle mission to keep the aging Hubble Space Telescope in orbit an additional five years.
Griffin was expected to announce his decision at 1500 GMT, after meeting on Friday with top NASA officials to discuss the issue, his spokesman Dean Acosta said in a statement.
The scientific community virtually unanimously backs a shuttle mission to extend the life of the Hubble, launched into orbit 16 years ago to help astrophysicists peer deep into the universe from outside the Earth's atmosphere.
Without refurbishment, the telescope will shut down in 2008 or 2009.
An engineer and physicist, Griffin in the past has spoken in favor of a refurbishing mission for the Hubble, as long as it does not put the space shuttle crew in jeopardy.
"If we can do it safely, we want to do it," Griffin has repeatedly ssaid in the past few months.
The NASA chief worked on the Hubble program early in his career and recently described the orbiting telescope as "one of the great scientific instruments of all time."
Since rocketing into orbit 575km above the Earth in 1990, the Hubble has provided scientists with countless pictures of the deep universe, taken free of the distortions from the Earth's atmosphere that ground-based telescopes suffer.
The Hubble helped scientists better gauge the age and origins of the universe, to observe distant supernovas, and identify and study bodies in and outside the solar system.
In the 2004 Hubble Ultra Deep Field, it pictured the most distant parts of the universe ever observed by visible light, "the deepest portrait of the visible universe ever achieved by humankind," the Space Telescope Science Institute said.
A new mission to the Hubble would replace the telescope's six stabilizing gyroscopes and its batteries to extend its life.
Astronauts would also repair an infrared spectrometer that has been on the blink since 2004 and install two new instruments, including the Wide Field Camera 3 that would enhance images of dark matter and of the first galaxies that were formed after the Big Bang, the standard model of the creation of the universe.
NASA had scheduled a refurbishing mission for Hubble in 2003, but scrapped it after the Columbia shuttle disintegrated while returning to Earth, exposing serious safety questions surrounding the NASA space program, especially with the shuttle's heat shield.
When Griffin took over NASA early last year, he announced his intention to review the cancelation of the Hubble mission.
Yet, although two of its last three missions were deemed successful, NASA has still not put safety concerns for the shuttles to rest. One of the problems with a Hubble mission is that should another heat shield problem arise in orbit, the shuttle crew would not be able to seek refuge aboard the orbiting International Space Station (ISS).
In addition, NASA has a tight calendar of another 15 missions to finish building the ISS before retiring the entire shuttle program in 2010, or four missions per year.
A Hubble mission would likely be programmed for early 2008 and would require a second space shuttle to remain at the ready for any rescue mission should the crew in orbit get into trouble.