Hopkins scientists work to find NASA spacecraft

Comet-bound Contour went missing after engine was set to give it a boost

August 16, 2002|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

NASA's Contour spacecraft has gone missing only six weeks into a planned four-year, $159 million mission to fly past two comets.

Controllers at the Johns Hopkins University's Applied Physics Laboratory near Laurel said yesterday that they lost contact with the one-ton spacecraft early yesterday, shortly after it was scheduled to fire its solid rocket engine and zip away from Earth toward its first rendezvous with a comet in 2003.

They immediately issued an all-points bulletin, asking the National Aeronautics and Space Administration's powerful Deep Space Network antennas to begin searching the skies and listening for Contour's radio signals. Communications experts worked to command the probe to call home.

But by late in the day, there was only silence.

Laboratory spokesman Mike Buckley said yesterday that it is possible the Maryland-built spacecraft's engine misfired or blew up. If so, the mission is likely doomed.

But it was too soon to lose hope, he said. "They're spending more time over there working than worrying. The mood is pretty good still. They're busy. They haven't covered the whole sky yet."

Many of the same laboratory scientists and engineers went through a similar emergency in December 1998, when a liquid-fuel engine on the Hopkins-built NEAR spacecraft misfired en route to the asteroid Eros.

Radio contact with NEAR was lost for several hours. When it was re-established, controllers managed to reprogram the spacecraft and salvage the mission, even though NEAR had lost 70 percent of its fuel.

Contour's mission

Comets are believed to hold the best-preserved evidence of the materials and conditions that combined to form the solar system 4.5 billion years ago. Scientists at the Hopkins lab, Cornell University and 11 other institutions designed Contour (for Comet Nucleus Tour) to gather data at close range to learn more about the composition and structure of comets.

Contour was launched into orbit on July 3. Plans called for its solid-fuel rocket engine to fire at 4:49 a.m. yesterday about 140 miles over the Indian Ocean. The 50-second boost was intended to accelerate the spacecraft to 28,000 mph and send it on a track that would carry it to within 62 miles of the comet Encke in November 2003. That boost was the solid-fuel engine's only role in the mission.

The rocket was programmed to ignite automatically. Laboratory controllers expected to get their first telemetry from the spacecraft at 5:35 a.m., Buckley said, telling them whether the rocket had fired as planned and whether the mission was on course.

If the rocket didn't fire and Contour was still in Earth orbit, "we expected to hear that, too," Buckley said. Instead, "there was no signal from Contour."

The rocket motor was a Thiokol Star 30, a 22-year-old design often used to boost communications spacecraft into geo-synchronous orbits. It has been flown in more than 80 missions with just one reported failure.

Contour was designed to be as foolproof as possible. Its solar panels and antennas did not have to be unfolded or deployed in orbit, avoiding mechanical glitches that have hobbled previous missions. They were also designed to provide power and communication links no matter how the spacecraft was positioned relative to the sun or Earth.

Speculation

"We're trying to send commands to the spacecraft to switch between its two transmitters and use different on-board antennas, in case they turned off for some reason," said mission manager Robert Farquhar. "But we really won't know what happened until we contact it."

Using the Deep Space Network antennas in Australia, California and Spain, controllers were aiming their commands toward various parts of the sky where Contour should be, or might be under a variety of scenarios, "to see what, if anything, comes back," Buckley said.

An explosion of the rocket "would be a possibility," Buckley said. It is also possible that the rocket firing went as planned, he said, but that it somehow silenced Contour's radio transmitter.

If the spacecraft is intact and on course toward Encke, the mission might be saved. If the rocket fired, Buckley said, "it's gone" because it can only be used once.

Controllers could still try to use Contour's liquid-fuel hydrazine thrusters. But if the spacecraft is badly off-course, the thrusters may not be enough to salvage a useful mission.

For now, the search is continuing. "We're cautiously optimistic that we will find the spacecraft," Farquhar said.

Baltimore Sun Articles
|
|
|
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.