Right now, Andrew Santo and his colleagues at The Johns Hopkins University's Applied Physics Laboratory (APL) are basking in the glow of success. Last Monday their creation, the NEAR Shoemaker spacecraft, made history's first landing on an asteroid, bringing a spectacular finale to a year of scientific discovery. But seven years ago, you wouldn't have wanted Santo's job.

That's when NASA handed APL a Space Age mission impossible: Design, build and test the first spacecraft to orbit an asteroid, do it for a fraction of what most deep-space missions cost, and do it in just 24 months. The mission, called NEAR, was to open a new chapter in deep-space exploration by becoming the first in NASA's so-called Discovery missions, whose mandate included development times of less than 3 years.

Santo, who served as spacecraft systems engineer on the NEAR project, says the assignment wasn't greeted with unanimous optimism at APL. "At the time we started," he recalled, "I bet about half the team was doubtful we could make it."

But Santo knew they had no choice. The only possible launch dates to the target the Asteroid 433 Eros were a mere 12 days in February 1996 (and to add to the pressure, the launch window on each of those days was only one minute long). After that, Eros would no longer be positioned for a spacecraft to go there easily from Earth.

Instead of being an impossible burden, however, Santo said the unforgiving schedule was actually an advantage. "That really helped us," he said. "That very narrow launch window helped us focus the team."

The overriding importance of the schedule pushed Santo and his teammates to adopt an approach that was highly unorthodox in the high-tech world of aerospace. Instead of requiring specially built components, the NEAR team chose hardware already available and ready to use without modifications. "I'd say 70 percent of the spacecraft components were off-the-shelf," Santo said. That kept costs down, helping the project stay within its budget of $113 million. Just as important, it saved time.

That doesn't mean everything went smoothly. A star tracking device procured by the team turned out to have a faulty cooling system, decreasing its accuracy. And engineers studying the craft's solar panels realized that if the spacecraft was rotated into and out of the harsh sunlight of space, the panels would expand and contract so much they could start to come apart. And there were other snags, but the NEAR team couldn't always afford to have them fixed. "Other people might have been forced to tell the vendor, 'Take this box apart and fix your problem,'" Santo said. "Our concern was, if we told the vendor to fix it, we would have missed our schedule."

In the end, Santo and his teammates managed to find ways to work around the problems. For the solar panels, for example, the solution was to avoid drastic changes in temperature by keeping the panels pointed at the Sun throughout the trip to Eros. That could have been a problem for communications, since the craft would have to be aimed directly at Earth for the high-gain antenna to work. But tests showed that the spacecraft's communications system would perform better than expected, and the engineers realized they could use the craft's low-gain antenna during the outward-bound cruise.

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And it wasn't long before the mood among the NEAR team changed from skepticism to optimism. "People had the feeling, 'Hey, we can really do this,'" Santo recalled. "And once that feeling started to go through the team, we had unbelievable team morale. People would work all hours of the night and day -- not because they wanted to impress their boss, but because they didn't want to let down the other guys on the team."

NEAR was finished in time for its planned launch on February 17, 1996, and the nearly three-year-long trip to Eros began. Along the way, the team refined the spacecraft's onboard computer programs, working by remote control to fix software bugs. "What surprised me was the lack of problems that we had," Santo said. Except for a power problem that disabled one of the craft's scientific instruments, an infrared spectrometer, "the spacecraft had no problems."

That is, until it reached its destination in December 1998. Instead of going into orbit around the asteroid, NEAR mysteriously aborted its planned maneuver and began firing thrusters wildly, spewing precious fuel into space. "Even today we don't know what happened," Santo said.

For days, trackers on Earth had no contact with the spacecraft, prompting chilling memories of another failed mission, Mars Observer, which was lost just before it was to orbit Mars in 1993.

"That was the first thing that went through our minds," said APL's Thomas Coughlin, NEAR project manager. And at the Deep Space Network (DSN), the collection of tracking stations used to maintain contact with NASA's solar system missions, there were dire predictions. "The guys at the DSN were saying, 'You're going to find this thing in a million pieces.'"

But the dire predictions didn't come true. The craft's onboard safety system kicked in and reestablished radio contact with home. "It found us, we didn't find it," said Coughlin. By early January 1999, NEAR was on course for a second rendezvous with Eros on Valentine's Day, 2000.

But what about the spent fuel? Would there be enough left to continue the mission? The answer to that had been decided before NEAR left Earth. Luckily, the NEAR team brought their creation in 11 pounds (5 kilograms) under its assigned weight limit, allowing the craft to carry 5 extra kilograms of fuel. That extra amount proved to be enough for the entire year of operations at Eros. Said Santo, "That extra 5 kilograms of fuel that we loaded probably saved the mission. It shows you that this is a tight business. You can do 99 things right, but if you do the 100^th thing wrong, it can kill you."

Renamed in memory of the late planetary scientist, Gene Shoemaker, NEAR Shoemaker orbited Eros for a full year, giving scientists a bounty of data that included more than 100,000 close-up images. And then, last Monday, came the bonus. "I think the team thought, we've been there long enough, let's try something new," Santo said. "Let's have some fun. Let's see if we can land this thing." Many on the project were skeptical that NEAR would survive its landing attempt. But as Coughlin said, "We'd thought it thorough, and knew everything had to go right. And it did go right."

NEAR Shoemaker's achievement has given NASA a badly needed success, in the wake of two failed Mars missions in 1999. "I think it truly has raised the bar a little bit on the new paradigm of how to do these 'Faster, Better, Cheaper' missions," Coughlin said. "It's a perfect example of something that did work."

At the Applied Physics Lab, meanwhile, the experience gained from the NEAR mission will be used for other deep-space missions, including the planned Comet Nucleus Tour and a Mercury orbiter called MESSENGER. Said Santo, "We're looking forward to the next level of challenges."