After the Stardust space probe was launched, ten years ago next month, it photographed comets beyond the orbit of Mars and collected particles blasting off one of them, Wild 2 (pronounced Vilt 2). Three years ago, on a return loop to Earth, it sent a capsule carrying comet dust down to eager scientists.
Now it has swung around Earth again, prompting three Utahns to produce astonishing views.
But first, the backstory.
When Stardust made its 2006 approach, scores of spectators drove to the World War II-era Wendover Air Station, near the Nevada border, hoping to catch a glimpse of the returning capsule. Suddenly, about 3 a.m. on Jan. 15, high in the west, it came streaking through the atmosphere at 28,600 mph, the fastest spaceship ever to reenter. Friction heated it, turning it into a blazing meteor far brighter than any star or planet. The watchers gasped, cheered and yelled as the yellow-orange dot crossed the dark sky, trailing a purple tail of ionized gas.
For half a minute the light grew more brilliant, passing above ancient air base structures and the Orion constellation, then gliding almost directly overhead. Dimming as it slowed, it entered a light cloud bank and disappeared. Unseen by the spectators, a parachute began lowering it to a safe landing in the Utah Test and Training Range. Two and a half minutes later a loud sonic boom hit.
Scientists around the world have studying the samples. Among their conclusions, wrote Dr. Don Brownlee of the University of Washington at Seattle, the principal scientific investigator, is that some components of the comet did not form in the most distant reaches of the solar system, as had been expected. Instead, temperatures were above 1,300 degrees C. when they coalesced. Yet other icy particles formed only 30 degrees C. above absolute zero (the coldest possible temperature).
“Because the rocky materials in comet Wild 2 formed at such high temperatures, we believe that they formed in the hot inner regions of the young solar system and were then transported all the way to beyond the orbit of Neptune,” Brownlee noted in a NASA press release of July 2007.
The capsule had landed but the bus, or mother ship, continued orbiting the sun, fully functional. Later, scientists sent it on another voyage, to rendezvous with and photograph Comet Temple 1.
A probe called Deep Impact had swept past Temple 1 in July 2005 and slammed it with an “impactor” craft that weighed 820 pounds.
“It worked too well, because the impactor hit the comet and threw up so much stuff that the mother ship was not able to see through the dust and debris,” said Patrick Wiggins, NASA solar system ambassador to Utah. As it sped past, Deep Impact’s cameras couldn’t see into the hole the impactor made to examine the comet’s interior structure.
So NASA scientists decided to take another look at Temple 1, using the Stardusts cameras. The encounter will happen in February 2011.
The Stardust mother ship was scheduled to swing past Earth last week, the encounter giving it a gravity assist boost and shaping its course toward Temple 1. It was to approach to within 5,600 miles of the planet.
On Tuesday, Kurt Fisher, a Salt Lake City resident and a member of the Salt Lake Astronomical Society, alerted the Utah Astronomy email discussion list about the approach:
“NASA’s Stardust spacecraft (will) streak by the Earth tonight in a gravity assist pass at between 420,000-300,000 km.,” he wrote. “I have low reliability report it may be mag 10. Ephemeris below. — I’m not planning on chasing this one myself, but here are the numbers.”
Fisher relayed sets of coordinates and times that had been calculated by the Jet Propulsion Laboratory. With luck, someone might get a look at the passing mother ship close to 9:30 p.m. But the craft is only five and a half feet long. While at its closest approach it would be 5,600 miles away, when visible over Utah it would be more than 21,700 miles out.
“I’ve got to look this over,” Wiggins said, recalling his thoughts when he studied the figures. He realized the spacecraft would be well placed in the night sky. Sunlight glinting from it could allow it to show up against the blackness.
Never one to pass up a space challenge, he prepared a large telescope in his home observatory near Salt Lake City. Aiming at the predicted location, he focused his astronomical camera through the telescope.
“My goodness, there it was,” he said. The spacecraft was passing Earth. The first few pictures were not well centered and he had to shift his telescope. Finally it was aimed where Stardust would pass.
Then, he said, he “just started taking pictures.” Wiggins made 72 ten-second exposures, spaced 52 seconds apart.
Soon he posted his images on his web site.
Howard Jackman of West Jordan downloaded them and assembled views into a single image showing the spacecraft’s path through the heavens. The Internet site Spaceweather.com put it on-line.
Fisher put the photos together to form a time-lapse movie. NASA and JPL posted it on the Stardust program site dedicated to the flight to Comet Temple 1.
Thanks to Wiggins, Fisher, Jackman, JPL, NASA and Spaceweather, people everywhere are able to examine extraordinary views of a tiny craft cruising past the starry vastness, briefly visiting Earth once again after traveling billions of miles in deep space.