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25-Aug-03 | Delta flight 300 – SIRTF

A new era for astronomy has begun!

In the early morning hours of 25 August, NASA’s Space Infrared Telescope Facility (SIRTF) was successfully placed into orbit by a two-stage Delta 7920H. Delta flight 300 — the 109th for Delta II and the second in a row for the new Delta II-Heavy configuration — leapt off Pad 17B at an official range time of 05:35:39.231 UTC. The 50-minute ride into space was quite uneventful, with the exception of telemetry issues that led to a nail-biting conclusion. Data reception dropped out prior to spacecraft separation, and the Canberra tracking station in Australia was unable to lock on to SIRTF’s signal at the expected time. For several minutes, the deployment could only be inferred from the Delta second stage’s evasive burn, which used the proper amount of fuel to make the correct movement away from the spacecraft, meaning that the 865-kilogram telescope was no longer attached. Mission controllers soon breathed a collective sigh of relief as SIRTF announced itself to be in an excellent state of health and in its proper orbit and orientation. Delta II thus continues an astounding streak of successes that now stands at 54 flights in a row.

SIRTF is the last of the Great Observatories, a highly successful group that includes the Compton Gamma Ray Observatory, the Chandra X-Ray Observatory, and the venerable Hubble Space Telescope. It will map the sky in the infrared spectrum with resolution and sensitivity far surpassing its predecessors, IRAS (Delta 166) and COBE (Delta 189). SIRTF was first announced over two decades ago and suffered delays too numerous to mention during its development, leading many to joke that its acronym stood for “Someday It’s Ready To Fly.” The $1.2 billion telescope — perhaps the most expensive payload ever to fly on Delta — uses an innovative approach to cooling its instruments that substantially reduced the system’s overall weight and allowed it to be launched aboard the relatively economical medium-class vehicle. Over the next three months, the instruments will be cooled to a few degrees above absolute zero and calibrated. The first images are expected to be released around December, at which time NASA will announce the winner of the SIRTF Naming Contest.

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