StarDust’s Firey Farewell

NASA’s Stardust spacecraft has now sent its last transmission to Earth. Image credit: NASA/JPL-Caltech

At 33 minutes after 4 p.m. PDT on March 24, NASA’s Stardust spacecraft finished its last transmission to Earth. The transmission came on the heels of the venerable spacecraft’s final rocket burn, which was designed to provide insight into how much fuel remained aboard after its encounter with comet Tempel 1 in February.

"Stardust has been teaching us about our solar system since it was launched in 1999," said Stardust-NExT project manager Tim Larson from NASA’s Jet Propulsion Laboratory in Pasadena, Calif. "It makes sense that its very last moments would be providing us with data we can use to plan deep space mission operations in the future."

Stardust’s original mission was to collect samples of a comet and return them to Earth. Above, comet particle tracks can be seen in samples of aerogel from Stardust. Credit: Stardust, JPL, NASA

Stardust has provided astrobiologists with a better understanding of the composition of comets. Stardust’s scientific successes are now helping researchers determine whether or not comets played an important role in the origins of life by delivering materials that were essential to the first living cells on Earth.

The burn to depletion maneuver was designed to fire Stardust’s rockets until insufficient fuel remains to continue, all the while downlinking data on the burn to Earth some 312 million kilometers (194 million miles) away. Mission personnel will compare the amount of fuel consumed in the burn with the amount they anticipated would be burned based on their fuel consumption models.

Fuel consumption models are necessary because no one has invented a reliable fuel gauge for spacecraft when in the weightless environment of space flight. Until that day arrives, mission planners can approximate fuel usage by looking at the history of the vehicle’s flight and how many times and for how long its rocket motors have fired.

Stardust-NExT photographed jets of gas and particles streaming from Comet Tempel 1 during Feb 14, 2011 flyby. The raw image was taken 15 seconds before closest approach at a distance of 244 kilometers, and has been extensively enhanced by outside analysts to visibly show the jets. Annotations show the location of the jets and the crater created by a projectile hurled by NASA’s prior Deep Impact mission in 2005. Credit: NASA/JPL-Caltech/University of Maryland/Post process and annotations by Marco Di Lorenzo/Kenneth Kremer

Mission personnel watched the final data from the burn come down at JPL’s Space Flight Operations Facility and at the Stardust-NExT mission support center at Lockheed Martin Space Systems in Denver.

"Stardust motors burned for 146 seconds," said Allan Cheuvront, Lockheed Martin Space Systems Company program manager for Stardust-NExT. "We’ll crunch the numbers and see how close the reality matches up with our projections. That will be a great data set to have in our back pocket when we plan for future missions."

The Stardust team performed the final burn to depletion because NASA’s most senior comet hunter is a spacecraft literally running on fumes. Launched on Feb. 7, 1999, Stardust had completed its prime mission back in January 2006. By that time, Stardust had already flown past an asteroid (Annefrank), flown halfway out to Jupiter to collect particle samples from the coma of a comet, Wild 2, and returned to fly by Earth to drop off a sample return capsule eagerly awaited by comet scientists. NASA then re-tasked the spacecraft to perform a bonus mission to fly past comet Tempel 1 to collect images and other scientific data. Stardust has traveled about 21 million kilometers (13 million miles) in its journey about the sun in the few weeks since the Valentine’s day comet Tempel 1 flyby, making the grand total from launch to its final rocket burn about 5.69 billion kilometers (3.54 billion miles).

With all that mileage logged, the Stardust team knew the end was near. Now, with its fuel tank empty and its final messages transmitted, history’s most traveled comet hunter will move from NASA’s active mission roster to retired.

"This kind of feels like the end of one of those old Western movies where you watch the hero ride his horse towards the distant setting Sun – and then the credits begin to roll," said Larson. "Only there’s no setting Sun in space."