Washington

All US spacecraft missions scheduled for launch this year are undergoing a sweeping review following a spate of high-profile failures that culminated in the loss of two Mars spacecraft last autumn.

Under the reviews, which have been ordered by Dan Goldin, administrator of the US space agency NASA, teams of NASA-appointed engineers are scrutinizing each project. Two launches have already been postponed, and others may be delayed.

After investigations into the Mars accidents had revealed a series of embarrassing mistakes and management lapses, Goldin directed the heads of his agency's field centres last month to take extra measures to ensure that missions in the pipeline don't have similar problems.

The Jet Propulsion Laboratory in California had already initiated a review of its Mars programme, while the Goddard Space Flight Center in Maryland responded by ordering independent ‘Red Team’ reviews of each project under its purview.

Delayed exposure: IMAGE is having to wait to study Earth's response to solar magnetic activity. Credit: SPACE NEWS

At least a dozen Earth and space science missions scheduled for launch in 2000 will undergo the review. These include IMAGE, Earth Observing-1, Cluster 2, the High Energy Solar Spectroscopic Imager (HESSI), TIMED, the Microwave Anisotropy Probe and Aqua, the second satellite in the Earth Observing System.

Mission scientists — many of whom are at universities rather than NASA centres — have mixed reactions to the NASA edict. Most say the additional checks can in principle help root out problems. But many worry that adding a major review so close to launch only disrupts projects with very tight schedules and cost margins.

HESSI, for example, is due to launch in July to observe solar flares at high-energy wavelengths. Run by the University of California at Berkeley, the $72 million Small Explorer mission is a shoestring operation by NASA standards, and has taken just two years to build.

Peter Harvey, the HESSI project manager at Berkeley, estimates that the project has already undergone 20 reviews. “To now have yet another review is killing us,” he says, not because of the one or two days taken up by the Goddard team's visit, but because of the two previous weeks his staff will need to prepare for the review.

Just when project engineers should be focused on the launch, he says, they will be presenting graphs instead. “Our attention is turned away from the spacecraft.”

A key assumption behind the ‘better, faster, cheaper‘ approach adopted by NASA is that it dispenses with much of the red tape and bureaucratic requirements of past spacecraft missions, which were a major factor in driving up costs. NASA reviews were to be kept to a minimum. The low-cost missions were also understood to assume a certain risk of failure by not taking the time and money to build in redundant systems.

Some scientists facing Red Team reviews worry that NASA might change its rules in mid-stream following the recent mission failures. The Massachusetts Institute of Technology's $20 million HETE-2 satellite, for example, was to have been launched in late January from Kwajalein Atoll in the Pacific Ocean. It had already been mated to its Pegasus rocket and was preparing to ship out from California when NASA called off the countdown (see Nature 403, 232; 2000).

Mission rules required that only one tracking station be guaranteed operational for launch. But the space agency decided it wanted two as a precaution. Although there had been no sign of trouble with the spacecraft, it was returned to the east coast for testing, and the launch has slipped to May.

NASA has delayed other launches for relatively minor reasons. IMAGE, which will study the Earth's magnetosphere, is managed by the Southwest Research Institute as the agency's first Midsize Explorer mission. It was to have been launched on 15 February. But after review teams questioned certain technical aspects of the project, the launch slipped to early March.

James Burch, the IMAGE principal investigator at Southwest, expects his spacecraft will ultimately be passed as fit. But he points out that NASA had long ago accepted the inherent risk of fast, cheap missions. “If somebody's going to say we don't want to take the risk of not having significant redundancy in the system, then that puts all these spacecraft in the museum,” he says.

Although Burch, Harvey and other project heads say they understand Goldin's concern, they question how much review is enough, and whether the Red Team exercises are productive.

When a spacecraft loses its place in the queue, it can take months to get back to the launch pad. Burch estimates that keeping IMAGE on the ground past its scheduled launch date costs around $60,000 a day. But, he says, “if NASA is going to pay to slip things to make themselves satisfied that the risk is low enough to go ahead, then that's their prerogative”.