NASA’s Stardust spacecraft is en route to Earth, a time capsule carrying the fundamental building blocks of our solar system when it formed billions of years ago. Next month, the spacecraft is to eject to Earth a capsule filled with particles of interstellar and comet dust.
The spacecraft has soared through space for some seven years, chalking up billions of travel miles. During the probe’s collection route, Stardust caught particles cast off comet Wild 2 in 2004.
Those particles are now safely tucked inside Stardust’s sample return capsule, headed for an early morning January 15 landing within U.S. Air Force Utah Test and Training Range (UTTR) at the U.S. Army Dugway Proving Ground southwest of Salt Lake City.
The $212 million Stardust mission was launched on February 7, 1999 by a Delta 2 rocket from Cape Canaveral Air Station, Florida, part of NASA’s Discovery Program of econo-class, highly focused science investigations. The spacecraft was built by Lockheed Martin Space Systems of Denver and is managed by NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
"We are approaching the end of a quite fantastic voyage," said Don Brownlee, Principal Investigator for Stardust at the University of Washington, Seattle.
The ancient comet and interstellar dust particles now on Stardust are to be studied for decades into the future, Brownlee said. They will undergo a battery of tests with an array of analytical tools, he told reporters today during a NASA press briefing on the mission from the space agency’s headquarters in Washington, D.C.
"Stardust has traveled half way to Jupiter to encounter a comet, grab a piece of it, and bring it back to the Earth," Brownlee said. Stardust is akin to a library in transit to Earth that has scarfed up the building blocks of the solar system that have been preserved at low temperatures for 4.5 billion years "and they are landing in the desert in just a couple of weeks," he added.
"It’s a distance record for an Earth returning spacecraft ... and it’s a first that we can all be proud of," noted Andy Dantzler, Director of the Solar System Division at NASA Headquarters in Washington, D.C.
Measuring less than 3-feet across, Stardust’s heat-thwarting reentry capsule will barrel through the atmosphere faster than any human-made spacecraft has ever come in before, said Tom Duxbury, Project Manager for Stardust at JPL.
Skyrocketing across the Western U.S. and shooting over Nevada toward its Utah landing, the canister will light up the night sky for a brief period. The fireball should be visible from San Francisco perhaps up to and beyond Portland, Duxbury said.
Entry velocity of the 101-pound (46-kilogram) capsule when it penetrates the atmosphere is about 28,000 miles per hour (12.8 kilometers per second), Ed Hirst, Mission System Manager at JPL, told SPACE.com. The capsule then deploys a drogue chute, followed by main parachute deployment.
The capsule should touch down January 15 at 3:12 a.m. Mountain Standard Time.
Following touchdown, the capsule will be recovered by air and ground teams. It will then be transported to a staging area at UTTR for retrieval of the sample canister held deep inside the return capsule. Once removed, the specimen-carrying canister is transported to the planetary materials curatorial facility at Johnson Space Center in Houston, Texas for examination.
Stardust is the first NASA mission to return "solid" samples from space since Apollo 17 returned to Earth in 1972. Apollo 17 moonwalkers brought back some 244 pounds (111 kilograms) of rock and soil samples. Specimens onboard Stardust will be ultra-tiny in contrast, but are the first bits of material returned from beyond the Earth-Moon orbit.
The Stardust craft snared particles blown off comet Wild 2 in 2004. To accomplish the collection task, the spacecraft made use of aerogel, a silica-based solid with a porous, sponge-like structure in which 99 percent of the volume is empty space. One thousand times less dense than glass, the wispy aerogel is often dubbed "blue smoke."
The aerogel is contained in a collection device deployed by Stardust that Brownlee likened to a large ice cube tray. Scientists are anxious to dig into the aerogel, he said, "trying to reveal the secrets of our origin."
During the encounter with Comet Wild 2, the sample tray with the aerogel cells was exposed to catch the particles spewing from the comet. The tray was then retracted into the canister for its long journey back to Earth.
When a particle hit the aerogel, it lodged itself in the material, forming a carrot-shaped track up to 200 times its own length as it slowed down and came to a stop. Once scientists start inspecting the aerogel, they will use these tracks to find the tiny prized particles that have been snagged in space.
While Stardust promises exciting science return, there’s also a bit of added tension due to the crash of the NASA Genesis return capsule on September 8, 2004.
Due to a parachute system failure, the returning Genesis capsule smashed into Utah desert at high speed. The impact busted up and contaminated delicate capture plates holding atoms of solar wind — leaving scientists the painstaking duty of rescuing science data from that mission.
Lockheed Martin Space Systems of Denver, Colorado designed and built both the Genesis and Stardust spacecraft.
A Mishap Investigation Board looking into the Genesis crash identified a probable direct cause of the failure of Genesis’ parachutes to open. They reported that the problem likely centered on a design error that involved the incorrect orientation of gravity-switch devices. The g-switches were onboard to sense the braking caused by the Genesis capsule’s high-speed entry into the atmosphere, and to then initiate a timing sequence that would have lead to deployment of the hardware’s drogue parachute and parafoil.
Similar devices are onboard Stardust.
JPL’s Hirst reported that there were lessons learned from the Genesis crash landing. Blueprints and pre-launch photos of Stardust hardware have been thoroughly gone over. Extra ground tests have also been done, he said.
After a very rigorous three to four month process, Hirst said that Stardust’s gravity switches are in the correct orientation and will indeed trigger.
Still, residual risk remains, Hirst said. "This is the fastest return capsule that has ever been brought back to Earth. So bringing it home for the first time is the only way to test a system like this. You do testing on the ground to the extent you can."
JPL’s Duxbury added that in the event of no parachute deployment, or the capsule hits harder than planned, the container is "extremely rugged." With the sample-carrying aerogel held within a very rigid and strong aluminum grid, he was confident that "we can very well finish the rest of our science opportunities."
An extra-added attraction of Stardust’s mission is use of the main part of the spacecraft, sans the sample return capsule. Called the spacecraft bus, this hardware will continue outward into space, orbiting the Sun.
NASA’s Dantzler told SPACE.com that future use of the hardware is possible. Early next year, the next announcement of opportunity for Discovery-class missions will be issued. A request for proposals to use the Stardust spacecraft bus is to be included within that document, he said.
The ultimate fate of the Stardust bus is that it will likely be ejected from the solar system, Brownlee observed. "We have a crew onboard," he said, calling attention to the names of over a million people etched on a tiny silicon chip that is attached to the hardware.
"I’m intrigued by the thought those names on that spacecraft will far outlive the Earth," Brownlee said. "That spacecraft and those names will still be floating around the galaxy somewhere" after the Sun becomes a red giant and scorches our Earth, he concluded.
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