The apparent loss of an entire generation of U.S. Mars missions has triggered a total reassessment of NASA's approach to interplanetary exploration, officials said today.

"The whole program is on the table for restructuring," space agency administrator Daniel S. Goldin said in an interview early today, adding that "there's a chance we may miss" or at least drastically change the next mission in the pipeline, slated for launch in 2001.

Missing and presumed dead are the entire $360 million suite of robots, including the Mars Polar Lander, that were to have constituted the second wave of planned long-term research on the Red Planet.

A number of experts in and out of NASA said the failures confirm fears that the program has pushed the space agency's "faster, better, cheaper" approach too far, cutting costs--and therefore staffing levels--too close to the bone. Some suggest the changes were pushed through too fast for institutions involved to adapt adequately.

Where the Jet Propulsion Laboratory (JPL), which manages missions for NASA, once handled one or two huge programs that went on for a decade or more, it now spreads its staff across 10 or 20 much smaller programs that must be dispatched in relatively quick succession, and on a relative shoestring. The approach was designed to minimize the risk of any individual mission. But experts say many experienced "old hands" may be either retired or too dispersed to provide the needed mentoring of younger personnel.

"I can assure you that these . . . failures have given us a wake-up call and we are going to respond to it," said NASA chief scientist Edward Weiler. He called the failures "a crushing blow" and added that he has "no confidence" the team will launch another lander in 2001, as scheduled, even though the hardware is largely built.

Rep. Dana Rohrabacher (R-Calif.), a member of a key congressional committee, said the House will hold hearings on the failures in February. "I am giving them [the Mars team] the benefit of the doubt" that they did their jobs and simply ran into bad odds in a risky undertaking, he said.

"In a way, this proves the importance of smaller missions. . . . Part of Dan Goldin's whole concept is that if you have a lot of small missions, you can afford to fail, and you learn from your failures," he said. Goldin's approach replaced the agency's previous tendency to spend years building just one or two huge "Battlestar Galactica" missions at a time, spending up to a billion dollars and pushing the stakes of failure into the stratosphere.

If the loss of the lander turns out to have been avoidable human error, however, Rohrabacher said there will be "severe repercussions--for Dan Goldin and for NASA." Among other things, he said, Goldin will lose some of his extraordinary credibility with Congress.

Investigators determined that human error was responsible for the September loss of the Polar Lander's sister ship, the Mars Climate Orbiter. A contractor forgot to convert English units to metric, and that mistake was compounded, the investigators said, by poor communications, two few people working on certain tasks and getting overstressed, and uncertain leadership. Problems that should have attracted notice were allowed to slide.

The same investigators, scrutinizing the Polar Lander program to catch any similar lapses before the landing date, noticed one possible technical problem, which the team acted to correct.

Several officials and scientists suggested that past successes of the interplanetary program based at JPL have lulled the public into a false impression of the complex and risky business of landing on alien worlds.

"Look at the history of landers on Mars," said Howard McCurdy of American University. "Of 12 attempts, three [the U.S. Vikings and Pathfinder] have made it. The Soviets lost all six of theirs. . . . Mars really eats spacecraft."

McCurdy, who has just completed a book on the "faster, better, cheaper" approach, said it has produced 16 missions of all kinds, not just to Mars, since 1992. Five have failed and one was canceled before launch because of cost overruns. Ten are still flying. "That's a 63 percent success rate, probably not what they had in mind."

The change from big and slow to fast and cheap has involved an uncomfortable sea change for JPL, according to people who work here. "We're changing paradigms again," said Norm Haynes, a veteran of the Viking program of the 1970s and today director of JPL's systems management. "Not only the 'what' but the 'how' is different. Unfortunately, we don't have that quite right yet."

"These programs were underfunded, and they were understaffed," said John Pike of the Federation of American Scientists, saying he blames congressional budget cutters and Goldin for allowing the screws to be tightened too far. "I think most of the blame is in Washington, not Pasadena."

Exhibit A, Pike added, was the case of the lost Mars Orbiter and the findings of understaffing, sloppy systems checking, managers missing key meetings and the like. He compared it to taking a 15-gallon trip "with 10 gallons of gas in the tank."

John Logsdon, a space policy historian at George Washington University, added the "insatiable space station" and the White House Office of Management and Budget to the list of potential culprits guilty of squeezing space sciences possibly too hard. "This may show that what we need is 'better and faster--but not quite as cheap.' "

Logsdon and others said there is no question of returning to the old Battlestar days, but suggested a slight retreat from the current level of risk and money constraint might be warranted.

The experts noted also that the historic Viking missions and other interplanetary spectaculars cost 10 or 20 times the typical cost of today's slimmed-down projects. And the mission that just vanished, they said, was about half the cost of the celebrated Pathfinder that landed on Mars in 1997.

The Polar Lander and two companion probes fell silent as they approached a fiery plunge into the Martian atmosphere shortly before a scheduled touchdown at the south pole at 3:01 p.m. (EST) Friday. After four increasingly difficult days, the Mars Polar Lander flight team remained unable to contact the lander or the probes.

All the recovery strategies were based on the premise that the lander reached the surface intact, experiencing some minor problem that could be corrected. Now the flight team acknowledges the craft might have suffered something more catastrophic. But because of the lack of telemetry during the crucial entry and descent phase--an economy measure--officials acknowledged they likely will never find out what went wrong.

Adding a device that would have provided simple tones that reveal minimal information about the spacecraft's status would have cost $5 million, engineers said.

The possible failure scenarios now are virtually endless, engineers lament. They range from a failure of the cruise stage to separate as the craft entered the atmosphere to malfunction of the parachute, retro-rockets or surface-sensing radar on the way down, to some quirk of "fate," as Weiler put it, that brought the spider-legged craft down on a rock, crevice or other deadly trap.

About the only thing engineers think they know about the latest loss is that it was not the result of a navigation mistake like the one that led to the loss of the Climate Orbiter.

Special panels will soon be formed to review not only the specific causes of the failures but also to rethink the entire strategy for interplanetary exploration, Goldin said. Although he defended his low-budget approach as the only current alternative and dismissed those who always argue that more money is the first solution, he echoed a number of outside experts in assessing the concerns. He said the review panels will consider, among other things: deficiencies in staff training; the need for better communications and other "infrastructure" at Mars; the need for smarter spacecraft; and NASA's relationship with contractors such as JPL.

A Long Shot to Mars

Four of the 12 missions to Mars by the United States over the past four decades have been failures.*

*not including Polar Lander

Failures Successes

1 1960s 3

1 1970s 3

no missions 1980s no missions

2 1990s 2

Future Voyages

NASA may retool its missions and reschedule its launches to Mars.

Launch Mission

March Mars Surveyor 2001 Orbiter

2001 Orbit planet for three years, study surface materials and radiation.

April Mars Surveyor 2001 Lander

2001 Lander, rover study soil, atmospheric chemistry and surface radiation.

May Mars Surveyor 2003

2001 Lander, rover collect samples and launch them into orbit for retrieval in 2005.

June Mars Express

2003 European Space Agency orbiter will conduct series of experiments, lander may search for water, signs of life.

July Mars Surveyor 2005 Orbiter, Lander

2005 Collect samples and launch them into orbit. French orbiter will retrieve 2003 and 2005 samples and return them to Earth by 2008.

Distance to Earth: 157 million miles

Transmission time: 14 minutes

Travel time: 11 months

SOURCE: NASA

CAPTION: At JPL, flight operations chief Sam Thurman, left, and project manager Richard Cook wait in vain for word of contact with the Mars Polar Lander.

CAPTION: Project manager Richard Cook and microprobes manager Sarah Gavit indicate little hope is left.