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14-Dec-09 | Delta flight 347 – WISE

Today marked the start of a new era in astronomy as NASA’s Wide-field Infrared Survey Explorer (WISE) spacecraft took flight and was successfully placed into its polar orbit by the venerable Delta II launch vehicle.

At 06:09:33 Pacific Standard Time (14:09:33 UTC), Space Launch Complex 2-West at Vandenberg Air Force Base lit up with the fire and thunder of WISE’s Delta 7320-10C Med-Lite vehicle. With only two stages and three strap-on booster motors, the 7320 has the least total impulse of any of the Delta II vehicles; nevertheless it had plenty of oomph for WISE, a lightweight craft that weighed less than three-quarters of a ton—1,457 pounds—at liftoff.

This marked the 92nd consecutive success for Delta II, an exemplary record dating back over a dozen years. In addition, the United Launch Alliance has now tallied 37 consecutive successes—one hundred percent—in its 36 months of existence. (Delta II accounts for 21 of them.)

The Wide-field Infrared Survey Explorer will survey the entire celestial sphere at least once during its nine-month mission. It is a follow-on to IRAS and COBE, two infrared surveyors that each launched aboard Delta vehicles—Delta 166 (25-Jan-83) and Delta 189 (18-Nov-89), respectively. The sensor package aboard WISE has a sensitivity at least a thousand times greater than those of its predecessors, made possible by a cryostatic system that uses solid hydrogen to keep cool. The hydrogen, weighing 35 pounds at liftoff, will gradually heat and boil away into the near-vacuum of space; hence the short mission duration.

WISE is part of NASA’s Explorer program, a series of scientific spacecraft that is older than the agency itself. More than three dozen Explorer missions have been lofted by Delta rockets, several of them still active—among them XTE, ACE, WMAP, and Swift. However with the Delta II production line shut down, and only five launch vehicles left unassigned, it is very possible that today’s launch will be the last teaming of Explorer and Delta.

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