A Solar Flare Stuns Stardust
Stardust -- a NASA mission to return samples from comet P/Wild 2 -- was only 1.4 AU (130 million miles) from the Sun on Nov. 8th when a powerful solar flare erupted. Engineers from the Stardust team were a little worried, since they had heard the resulting radiation storm was the fourth largest since 1976. A cloud of high-energy particles was heading for Earth and for Stardust.
Right: These Solar and Heliospheric Observatory coronagraph images, captured Nov 8-9, 2000, suddenly became cloudy when high-energy particles from the Sun peppered the spacecraft's CCD camera following a powerful solar flare. Star cameras on Stardust were similarly fogged, sending that spacecraft into standby mode.
Their fears came to pass the next day when a stream of high-energy protons hit the spacecraft. Stardust's two star cameras, which it uses to control the spacecraft's orientation, were peppered with radiation. Protons from the solar wind electrified pixels in the star cameras, producing dots that the camera interpreted as stars. The 12 brightest dots, the ones the spacecraft relied on to point its way, were electrified pixels, which showed up as false stars. Hundreds of these star-like specks inundated the star camera's field of view, which meant it could not recognize its attitude in space.
Above: (Left) A normal Stardust star camera image, captured after the radiation storm had subsided. (Right) A "snowy" image captured during the storm. The many speckles are caused by high energy particles striking the spacecraft's camera elements. [more information]
The spacecraft did the safest thing it could - it went into standby mode, turning its solar panels toward the Sun and waiting for communication from Earth. While it was waiting, the spacecraft tried again to determine its attitude using two different sets of cameras. But the images repeatedly produced hundreds of bogus stars.
The flight team didn't hear from Stardust when they tried to communicate with it the morning after the solar flare. They deduced that the flare had caused Stardust to go into standby mode, and they knew that meant the spacecraft would send a signal within 24 hours.
Finally, on Monday Nov. 13, the Stardust flight team commanded the spacecraft to leave safe mode. The star camera started working again, controlling the orientation of the spacecraft perfectly. The engineers retrieved more data from Stardust to ensure the entire spacecraft had not been affected by the solar flare.
An image taken days after the radiation storm subsided shows that the camera had completely recovered from the proton hits. All the bright objects in the picture can be identified as stars, Jupiter or Saturn.
Stardust was launched on Feb. 7, 1999 from Cape Canaveral, FL. The spacecraft is headed for an encounter with Comet P/Wild 2 in 2004. Stardust's mission is to collect samples of dust flying off the comet nucleus, and to collect interstellar particles flowing through our solar system. Stardust will fly back toward Earth in 2006 to drop off the samples in a parachute-equipped return capsule. Stardust, part of NASA's Discovery Program of low-cost, highly focused science missions, is managed by JPL for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology. For more information on the Stardust mission and images from the recent encounter, go to http://stardust.jpl.nasa.gov.
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STARDUST Spacecraft is "Temporarily Blinded" by Solar Flare -- from JPL
Comet Wild-2 -- find out more about the Stardust comet.
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