The Stardust Mission
Written: July 1999
The Stardust spacecraft will fly close to a comet and, for the first time ever, bring cometary material back to Earth for analysis by scientists. Launched on February 9, 1999, Stardust will be the first U.S. mission dedicated solely to cometary research and the first mission to ever return a sample of extraterrestrial material from outside the orbit of the Moon. Its primary goal is to collect comet dust and volatile samples during a planned close encounter with comet Wild 2 in January of 2004. Additionally, the Stardust spacecraft will bring back samples of interstellar dust including the recently discovered dust streaming into the solar system from the direction of Sagittarius.
These materials consist of ancient pre-solar interstellar grains and nebular condensates including remnants left over from the formation of the solar system. Their analysis is expected to yield important insights into the evolution of the sun and planets and possibly into the origin of life itself.
The Stardust Spacecraft
Stardust is currently in the middle of its 5 year journey to a rendezvous with the Comet Wild 2 in January of 2004. Why does it take so long to get there? One way to keep the expense of this mission down was to use a "gravity assist" trajectory. Basically, if an object makes a very close flyby of a planet, the planet's gravity will actually slingshot that object to a much higher velocity. Therefore, instead of having to rely on the launcher to get the spacecraft up to speed, the slingshot effect will do the job instead. Thus, a much smaller (and less expensive) rocket is needed to launch the spacecraft. Stardust had to completely orbit the Sun and re-encounter Earth for its gravity assist (on January 15, 2001)! It now has to complete 2 more orbits of the Sun to complete it's mission.
The picture on the right is the Stardust Spacecraft. The large flat panels are the solar panels, which Stardust uses to generate its power. The gray blocks on the solar panels (right side in picture) are armored shields, which will be used to protect the spacecraft from damage during it's encounter with the comet. The object extending out of the top of the spacecraft, which resembles a tennis racket, is the Particle Catcher. The Particle Catcher will collect samples from the comet using a revolutionary new substance called Aerogel. After collecting the samples they will be inserted into the Sample Return Capsule which is the bright silver, cone-shaped object on the left hand side of the spacecraft. This return capsule is the section of the spacecraft that will land in Utah.
Aerogel - "Blue Smoke"
Particle captured in Aerogel.
Catching comet dust is no easy feat. When the spacecraft flies past the comet, the impact velocity of the particles will be up to 6 times the speed of a bullet fired from a rifle. Although the captured particles will each be smaller than a grain of sand, high-speed capture could alter their shape and chemical composition - or vaporize them entirely.
To collect the particles without damaging them, Stardust will use an extraordinary substance called Aerogel - a silicon-based solid with a porous, sponge-like structure in which 99 percent of the volume is empty space. Aerogel is 1,000 times less dense than glass, another silicon-based solid. When a particle hits the Aerogel, it will bury itself in the material, creating a carrot-shaped track up to 200 times its own length, as it gently slows down and comes to a stop. Since aerogel is mostly transparent - sometimes called blue smoke - scientists will use these tracks to find the tiny particles.
The Sample Return Capsule (SRC)
The SRC stores the samples of comet dust and interstellar dust in the sample canister. Stardust will release the The SRC just prior to its final Earth encounter. Stardust will set up the proper flight trajectory and entry angle, and impart a stabilizing spin to the capsule upon release. The capsule will enter the Earth's atmosphere at a whopping 28,600 miles per hour!
After entry the SRC will continue to free-fall until approximately 10,000 feet, at which point the main parachute deployment sequence will initiate. The planned landing site is the Utah Test and Training Range (UTTR), southwest of Salt Lake City.
The reentry to landing accuracy has been analyzed and found to be sufficient to achieve a landing footprint of 18 x 52 miles - well within the Utah Test and Training Range. A reinforced ring-slot descent chute will be deployed with the aid of a pilot chute. The descending capsule will have a UHF beacon and the parachute will be tracked by ground radar.
Following touchdown, the SRC will be recovered by helicopter or ground vehicles and transported to a staging area at UTTR for retrieval of the sample canister. The canister will then be transported to the planetary materials curatorial facility at Johnson Space Center.
UPDATE: January 2, 2004 - NASA Spacecraft Makes Great Catch
Team Stardust, NASA's first dedicated sample return mission to a comet, passed a huge milestone today by successfully navigating through the particle and gas-laden coma around comet Wild 2 (pronounced "Vilt-2"). During the hazardous traverse, the spacecraft flew within about 230 kilometers (143 miles) of the comet, catching samples of comet particles and scoring detailed pictures of Wild 2's pockmarked surface.
Closest approach was at about 19:22 Universal Time (11:22 a.m. Pacific Standard Time). The spacecraft's radio signal was received on Earth 21 minutes and 40 seconds later, at 11:44 a.m. PST.
"Things couldn't have worked better in a fairy tale," said Tom Duxbury, Stardust project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"These images are better than we had hoped for in our wildest dreams," said Ray Newburn of JPL, a co-investigator for Stardust. "They will help us better understand the mechanisms that drive conditions on comets."
"These are the best pictures ever taken of a comet," said Principal Investigator Dr. Don Brownlee of the University of Washington, Seattle. "Although Stardust was designed to be a comet sample return mission, the fantastic details shown in these images greatly exceed our expectations."
The collected particles, stowed in a sample return capsule onboard Stardust, will be returned to Earth for in-depth analysis. That dramatic event will occur on January 15, 2006, when the capsule makes a soft landing at the U.S. Air Force Utah Test and Training Range. The microscopic particle samples of comet and interstellar dust collected by Stardust will be taken to the planetary material curatorial facility at NASA's Johnson Space Center, Houston, Texas, for analysis.
Stardust has traveled about 3.22 billion kilometers (2 billion miles) since its launch on February 7, 1999. As it closed the final gap with its cometary quarry, it endured a bombardment of particles surrounding the nucleus of comet Wild 2. To protect Stardust against the blast of expected cometary particles and rocks, the spacecraft rotated so it was flying in the shadow of its "Whipple Shields." The shields are named for American astronomer Dr. Fred L. Whipple, who, in the 1950s, came up with the idea of shielding spacecraft from high-speed collisions with the bits and pieces ejected from comets. The system includes two bumpers at the front of the spacecraft -- which protect Stardust's solar panels -- and another shield protecting the main spacecraft body. Each shield is built around composite panels designed to disperse particles as they impact, augmented by blankets of a ceramic cloth called Nextel that further dissipate and spread particle debris.
This image shows the comet Wild 2, which NASA's Stardust spacecraft flew by on Jan. 2, 2004. This image is the closest short exposure of the comet, taken at an11.4-degree phase angle, the angle between the camera, comet and the Sun.
This image was taken during the close approach phase of Stardust's Jan 2, 2004 flyby of comet Wild 2. It is a distant side view of the roughly spherical comet nucleus. One hemisphere is in sunlight and the other is in shadow analogous to a view of the quarter moon. Several large depressed regions can be seen. Comet Wild 2 is about five kilometers (3.1 miles) in diameter.
"Everything occurred pretty much to the minute," said Duxbury. "And with our cometary encounter complete, we invite everybody to tune in about one million, 71 thousand minutes from now when Stardust returns to Earth, bringing with it the first comet samples in the history of space exploration."
Scientists believe in-depth terrestrial analysis of the samples will reveal much about comets and the earliest history of the solar system. Chemical and physical information locked within the cometary particles could be the record of the formation of the planets and the materials from which they were made.
UPDATE: January 15, 2006 - NASA's Comet Tale Draws to a Successful Close
NASA's Stardust sample return mission returned safely to Earth when the capsule carrying cometary and interstellar particles successfully touched down at 2:10 a.m. Pacific time (3:10 a.m. Mountain time) in the desert salt flats of the U.S. Air Force Utah Test and Training Range.
"Ten years of planning and seven years of flight operations were realized early this morning when we successfully picked up our return capsule off of the desert floor in Utah," said Tom Duxbury, Stardust project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The Stardust project has delivered to the international science community material that has been unaltered since the formation of our solar system."
Stardust released its sample return capsule at 9:57 p.m. Pacific time (10:57 p.m. Mountain time) last night. The capsule entered the atmosphere four hours later at 1:57 a.m. Pacific time (2:57 a.m. Mountain time). The drogue and main parachutes deployed at 2:00 and 2:05 a.m. Pacific time, respectively (3:00 and 3:05 a.m. Mountain time).
"I have been waiting for this day since the early 1980s when Deputy Principal Investigator Dr. Peter Tsou of JPL and I designed a mission to collect comet dust," said Dr. Don Brownlee, Stardust principal investigator from the University of Washington, Seattle. "To see the capsule safely back on its home planet is a thrilling accomplishment."
The sample return capsule's science canister and its cargo of comet and interstellar dust particles will be stowed inside a special aluminum carrying case to await transfer to the Johnson Space Center, Houston, where it will be opened. NASA's Stardust mission traveled 2.88 billion miles during its seven-year round-trip odyssey. Scientists believe these precious samples will help provide answers to fundamental questions about comets and the origins of the solar system.
UPDATE: January 18, 2006 - Stardust Scientists Ecstatic about Samples
Scientists have confirmed that samples from a comet and interstellar dust have been returned to Earth by the Stardust spacecraft.
The scientist team opened the Stardust sample return capsule on Tuesday in a special facility at NASA's Johnson Space Center (JSC), Houston.
"The collection of cometary particles has exceeded our expectations," said Dr. Donald Brownlee, Stardust principal investigator from the University of Washington, Seattle. "We were absolutely thrilled to see thousands of impacts on the aerogel."
Inside the capsule, a tennis racket-like sample tray holds the particles captured in a gel as the spacecraft flew within 149 miles of comet Wild 2 in January 2004. An opposite side of the tray holds interstellar dust particles caught streaming through the solar system by Stardust during its seven-year journey. The team is analyzing the particle capture cells and removing individual grains of comet and interstellar dust. They will be sent to select investigators worldwide.
Closeup view of a cometary impact (upper right) into aerogel was inspected by scientists at a laboratory at the Johnson Space Center hours after the Stardust Sample Return Canister was delivered to the Johnson Space Center from the spacecraft's landing site in Utah. Image credit: NASA