Dnepr rocket lifts off with satellites for France, Sweden
BY STEPHEN CLARK
Posted: June 15, 2010
Updated @ 12:30 p.m. EDT
A Soviet-era ballistic missile blasted off from southern Russia on Tuesday with a French spacecraft to observe the sun and a Swedish experiment to demonstrate orbital formation flying with two satellites.
The three-stage booster was expected to haul the two payloads into sun-synchronous orbit about 450 miles high and deploy the satellites within 16 minutes of liftoff.
A tracking station in Oman confirmed the rocket released the Picard and Prisma payloads as planned.
Controllers established communications with the Prisma spacecraft at 1614 GMT (12:14 p.m. EDT) as it passed over a Swedish ground station. Prisma officials say their satellites are performing flawlessly, and the solar panels have been unfurled.
The launch was the 15th flight of the Dnepr rocket, a converted Ukrainian SS-18 rocket built for the Soviet Union's military missile forces. Fourteen Dnepr missions have been successful.
Picard is commencing a two-year mission to watch the sun with three instruments. Scientists hope the satellite will provide insights into the sun's variability and its link to Earth.
The 315-pound spacecraft is based on a microsatellite platform developed by CNES, the French space agency.
CNES is also managing the Picard mission with the help of Belgium, Switzerland and French research institutions. The cost of the mission is 70 million euros, or approximately $85 million at current exchange rates.
The mission is named for Jean Picard, the French astronomer who first accurately measured the sun's diameter in the 17th century.
Picard's 4.3-inch imaging telescope, called SODISM, will obtain ultra-precise measurements of the sun's diameter, shape and rotation. The telescope will also probe deep into the sun's interior to seek the source of variations in the solar irradiance, or changes in the radiant energy produced by the sun.
Two more instruments, named SOVAP and PREMOS, will measure the total solar irradiance and energy fluctuations in ultraviolet, visible and infrared light.
French scientists say Picard will complement observations by NASA's Solar Dynamics Observatory, a satellite launched in February that is now studying the sun with a high-resolution telescope, a seismic imager and an ultraviolet radiation monitor.
SDO and Picard use different methods in their observations, providing a check on each mission's results.
Picard's launch comes just as solar activity is increasing after an extended phase of relative tranquility on the sun, a period known as solar minimum. The fortunate timing means Picard will observe the sun as more solar storms develop and send plumes of radiation toward Earth.
The Dnepr rocket also launched the Prisma mission into space Tuesday.
Consisting of two satellites, Prisma will attempt a daring demonstration of new technologies for automated formation-flying and rendezvous of spacecraft in orbit.
Autonomous formation flying and rendezvous applications include orbital maintenance, automatic docking and scientific missions tying together multiple satellites to form a massive telescope to study distant stars.
"This choice of formation-flying was made because it was an an area nobody [has tried before], at least not with the precision that's going to be shown with the Prisma satellites," said Christer Nilsson, Prisma program manager at the Swedish space agency.
Prisma's Mango and Tango spacecraft, bolted together for the launch, will separate Aug. 3 to begin their trials.
Zooming through space at 17,000 mph, the satellites will test autonomous rendezvous technology from Sweden, a GPS system from Germany, a radio frequency instrument from France, and a vison-based navigation sensor from Denmark.
Playing the role of the active satellite, Mango will repeatedly approach and back away from Tango for up to ten months, demonstrating each of the technologies one-by-one.
Mango is a 331-pound cube-shaped craft about the size of a kitchen stove. It will try to stay in lockstep with the smaller 88-pound Tango satellite, which has roughly the dimensions of an average microwave.
Engineers plan to cap the mission with a rendezvous attempt to place the satellites just a meter, or about three feet, apart some time this fall using the optical sensor from Denmark.
The larger Prisma satellite also features two experimental thrusters burning green propellant based on ammonium dinitramide. The non-toxic fuel is more environmentally-friendly and efficient than hydrazine propellant used on most satellites.
Swedish Space Corp. built the satellites for the Swedish National Space Board. The mission cost Sweden about $50 million, but that figure doesn't include contributions from European partners.
Our earlier feature story on the Prisma mission includes more details on the technologies it will test in space.
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