Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2003 September 5 
Posted on 09/05/2003 4:57:23 AM PDT by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2003 September 5
Explanation: Streaking skyward, a Boeing Delta 2-Heavy rocket carries NASA's Space InfraRed Telescope Facility (SIRTF) aloft during the early morning hours of August 25th. The dramatic scene was recorded in a time exposure from the pier in Jetty Park at the northern end of Cocoa Beach, Florida, about 2.5 miles from the Cape Canaveral launch site. SIRTF (sounds like "sir tiff") will explore the distant Universe in infrared light as the fourth and final satellite observatory in NASA's Great Observatories Program. The three other large astrophysics satellites were designed for higher energies in the electromagnetic spectrum, with the Hubble Space Telescope operating near visible wavelengths, the Compton Gamma Ray Observatory instruments sensitive to gamma rays, and the Chandra Observatory detecting cosmic x-rays. SIRTF has been launched into an Earth-trailing solar orbit to reduce its exposure to infrared radiation from our fair planet. Cooled by an on board supply of liquid helium, SIRTF's infrared detectors will operate at near absolute zero temperatures. Presently, SIRTF's systems are undergoing a 90-day check out.
SIRTF - the Space Infrared Telescope Facility - was launched into space by a Delta rocket from Cape Canaveral, Florida on 25 August 2003. During its 2.5-year mission, SIRTF will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space between wavelengths of 3 and 180 microns (1 micron is one-millionth of a meter). Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground.
Consisting of a 0.85-meter telescope and three cryogenically-cooled science instruments, SIRTF will be the largest infrared telescope ever launched into space. Its highly sensitive instruments will give us a unique view of the Universe and allow us to peer into regions of space which are hidden from optical telescopes. Many areas of space are filled with vast, dense clouds of gas and dust which block our view. Infrared light, however can penetrate these clouds, allowing us to peer into regions of star formation, the centers of galaxies, and into newly forming planetary systems. Infrared also brings us information about the cooler objects in space, such as smaller stars which are too dim to be detected by their visible light, extrasolar planets, and giant molecular clouds. Also, many molecules in space, including organic molecules, have their unique signatures in the infrared.
Because infrared is primarily heat radiation, the telescope must be cooled to near absolute zero (-459 degrees Fahrenheit or -273 degrees Celsius) so that it can observe infrared signals from space without interference from the telescope's own heat. Also, the telescope must be protected from the heat of the Sun and the infrared radiation put out by the Earth. To do this, SIRTF will carry a solar shield and will be launched into an Earth-trailing solar orbit. This unique orbit will carry SIRTF far enough away from the Earth to allow the telescope to cool rapidy without having to carry large amounts of cryogen (coolant). This innovative approach has significantly reduced the cost of the mission.
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