By Irene Klotz
Kennedy Space Center, Florida
Despite massive budget shortfalls and a looming retirement date, the US space agency (Nasa) will not abandon its shuttle programme and will keep its promise to finish building the International Space Station.
Nasa says funds will be diverted from science programmes
To back up its pledge, the US has unveiled a spending plan that slightly increases the 2007 budget for Nasa, even though most other non-military programmes are being cut.
The collective sigh of relief by Europe and Nasa's other partners in the space station programme, however, is being drowned out by the wails of scientists.
To help pay for 16 shuttle missions to the space station, Nasa plans to divert about $2bn (£1.1bn) from its science programmes and another $1.5bn (£0.9bn) from its new lunar venture between now and 2010.
"I wish we hadn't had to do it," Nasa administrator Michael Griffin said at a press conference to discuss the agency's $16.8bn (£9.6bn) spending plan.
"I didn't want to, but that's what we needed to do."
Reaction from the science community was swift and sharp.
Wesley Huntress, a former Nasa associate administrator who now heads the California-based Planetary Society, said the agency was "essentially transferring funds from a popular and highly productive programme into one scheduled for termination".
Nasa does not plan to scale back on-going science programmes, such as its highly successful Mars exploration rovers, the collaborative Cassini mission at Saturn and the orbital observatories Hubble, Chandra and Spitzer.
Science spending capped
New projects will bear the brunt of the cuts.
Targeted programmes include the Terrestrial Planet Finder, which aims to locate Earth-like worlds around other stars, and a mission to Jupiter's icy moon Europa, which may harbour a liquid ocean beneath its crust.
Under the new plan, spending on science will be capped at 1.8% for the year that begins 1 October, and increase 1% per year through 2010.
"We, of course, would like to be able to grow science for the next few years at a higher level; but we are in a very difficult posture right now in the space agency," Dr Griffin said.
One final servicing mission to the Hubble Space Telescope is planned
"Nasa simply cannot afford to do everything that our many constituencies would like us to do. We must set priorities and we must adjust our spending to match those priorities."
Nasa is under orders from President George W Bush to shut down the shuttle programme by 1 October, 2010, no matter what shape the half-built space station is in.
The agency plans to take steps as soon as this year to begin transitioning from the shuttle to a newly proposed pair of launch vehicles to carry people and cargo to the Moon.
The so-called Crew Launch Vehicle also will be used for space station transport after the space shuttles are decommissioned.
Nasa never dreamed completing the space station would take so long, but shuttle flights have been largely on hold since the 2003 Columbia disaster.
The agency flew one test flight last year, but problems similar to that which caused Columbia's demise resurfaced, prompting another round of repairs.
Nasa now hopes to fly the shuttle again in May.
The agency's proposed budget allots $6.2bn (£3.5bn) for the space shuttle and space station programmes; $5.3bn (£3.0bn) for space science; and $4.0bn (£2.3bn) for development of the Crew Launch Vehicle and other systems needed for the new exploration initiative.
Although Bush called for a return to the Moon as a stepping-stone toward Mars and other Solar System bodies, Nasa's budget includes funds for just one lunar flight, at a total projected cost of more than $100bn (£60bn).
Discovery flew a test mission last year
In addition to the 16 space station missions, Nasa is also reserving funds for one last servicing mission to the Hubble Space Telescope, provided the shuttle proves safe enough to make the journey.
Missions to the Hubble observatory will not be able to reach the space station for shelter in case of an emergency.
Nasa implemented a safe-haven option for shuttle crews following the loss of Columbia and its crew. The shuttle's heat shield had been damaged during the launch and the ship was destroyed as it returned through the atmosphere for landing 16 days later.
Nasa now wants its shuttle crews to have the option of staying aboard the station until a rescue mission could be launched.
Managers are considering waiving that option for a Hubble servicing mission if attempts to fix problems with the shuttle fuel tank, which shed debris to damage Columbia, as well as developing in-orbit heatshield repair techniques are successful.