For scientists involved in a space shuttle mission, the last few days before launch are always filled with anticipation. But there has also been anxiety for Michael Kobrick of NASA's Jet Propulsion Laboratory (JPL), a project scientist for the upcoming Shuttle Radar Topography Mission.
Just last week, NASA headquarters informed Kobrick and his team that the STS 99 astronauts may only have nine days for data gathering, instead of the 10 originally planned.
For Kobrick, that means having to face some disappointed scientists who are anxiously waiting for what has been billed as the most detailed continuous topographic map of Earth ever created.
Kobrick is lobbying NASA to reinstate the mission to its full duration, and he said he would continue to push his cause throughout the flight.
"I'm not going to give up until [the astronauts] land," said Kobrick.
According to spokesman Dwayne Brown at NASA headquarters, the agency's plan is to leave open the option of an extension, and the final decision will be made during the mission.
The reason for the change, NASA has said, involves the 197-foot (60-meter) mast that will be extended from the shuttle's payload bay several hours after launch. The mast contains a secondary antenna that, in combination with a much larger antenna in the bay, is designed to help gather detailed data on the Earth's topography.
Originally, the flight plan called for the astronauts to stow the antenna by activating a set of retraction motors during the mission's 11th day, about 18 hours before landing. The mission plan now calls for the mast to be stowed during the 10th flight day, about 24 hours earlier than first planned. This would result in a 10 percent loss of planned topographic coverage, Kobrick said.
Mission planners have told Kobrick they may decide to waive the flight rules and add the 10th day of data-gathering, if everything is going well.
However, the agency's chief concern is that a mechanical problem could prevent the mast from retracting.
In that case, the astronauts would have to perform a spacewalk to stow the balky mast before the shuttle could return to Earth. (Detaching the mast and leaving it in space, NASA has said, is not a desirable option.)
The flight's final day is reserved in case the shuttle's landing is postponed due to bad weather. For that reason, Kobrick said, headquarters wants to end the scientific portion of the mission early in order to leave enough time for a contingency spacewalk.
Kobrick said NASA told him that the only loophole is if a way can be found to conserve enough of the shuttle's resources to extend the total mission duration to 13 days. However, he said he had been told by some shuttle experts that this is essentially impossible, given the amount of power the radar experiment will consume.
According to Kobrick, NASA's worries about the hardware on the radar mission center on the mast's two retraction motors and the three latches designed to secure the retracted mast in its stowage container.
Kobrick said he and his colleagues have stressed to NASA that failure is unlikely, due to the redundancy of the components involved: Either of the retraction motors and two of the three latches could do the job, he noted.
The change in plans by NASA headquarters does not result from any late-breaking information about the hardware, Kobrick said. "There's nothing we know now that we didn't know two years ago," he said.
Instead, Kobrick speculated that the failures of three JPL Mars projects -- the Mars Climate Orbiter, the Mars Polar Lander and the twin Deep Space 2 microprobes -- have made NASA skittish about possible failures in another JPL effort -- even if it is only for the sake of appearances.
"I think there's just a heightened sensitivity about having a success," he said. "I think had we not had the unfortunate occurrences in three of our last Mars missions, we probably wouldn't be facing this now."
It is possible, Kobrick said, that if no problems with the mast turn up during the first eight days off the mission, the 10th day of data gathering may be approved. That would also depend on predicted weather conditions for landing at the primary shuttle runway at Cape Canaveral, as well as at California's Edwards Air Force Base -- the backup landing site.
"If we get to day eight," Kobrick said, "and the weather's good at both places, and everything's working fine, I can easily imagine [Mission Commander Kevin] Kregel calling down and saying, 'Let's go for the extra day.' I'm hoping he does that."
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