Sirtf

The SIRTF (Space Infrared Telescope Facility) was planned as a 1 meter class, cryogenically cooled space telescope to be operated as an observatory for infrared astronomy.

The main objectives of the mission were: 1) physical studies of the planetary system; 2) detailed study of cold circumstellar dust clouds; 3) a search for the enigmatic brown dwarfs; 4) extension of IRAS studies of forming stars to lower temperatures and luminosities; 5) identification and study of powerful infrared galaxies; and, 6) infrared measurements of all presently catalogued quasars.

The spacecraft was conceived as a long duration facility serviceable by the Shuttle or at a manned space station. Unlike IRAS (Infrared Astronomical Satellite), which swept rapidly across the sky, SIRTF was to be a true observatory, carrying a variety of focal plane instruments. The instruments selected included: 1) a wide field and high resolution camera covering the 2 to 30 micron region with large monolithic detector arrays; 2) an imaging photometer, with small arrays of high sensitivity detectors covering the spectral range from 3 to 700 microns; 3) a spectrometer operating out to 200 microns with resolving power from 50 to >1000. The instrument sensitivity was expected to be increased by a factor of 100 to 1000 over that of IRAS, and the spatial resolution was to be at least a factor of 10 times finer than IRAS.

The Space Infrared Telescope Facility (SIRTF), last of NASA's Great Observatories, was built by Lockheed Martin/Sunnyvale with the Cryogenic Telescope Assembly (CTA) built by Ball; management was by JPL with science operations at the SIRTF Science Center in Pasadena. SIRTF followed on the US/UK/Netherlands IRAS sky survey satellite (1983) and ESA's ISO observatory (1995-98). The US Defense Dept.'s MSX (1996-1997) was another notable IR mission which made a galactic plane survey. The other Great Observatories were the Hubble Space Telescope, the Compton Gamma Ray Observatory, and the Chandra X-ray Observatory.

SIRTF was placed in a solar orbit. The so-called 'Earth-trailing orbit' had the advantage that the infrared-bright Earth was very far away, and didn't block out large interesting pieces of the sky SIRTF might want to look at or interfere with the cryogenic cooling of the telescope.

SIRTF had a 0.85-meter infrared telescope, with a liquid-helium cooled focal plane carrying the three main instruments, IRAC, IRS and MIPS. IRAC (built by Giovanni Fazio's team at the Harvard-Smithsonian) was a near infrared camera imaging in the 3 to 8 micron range. IRS was a spectrograph covering the mid infrared 5 to 40 micron range. The MIPS far infrared Multiband Imaging Photometer covered the 12 to 160 micron range. The spacecraft was 4.45m high and 2.11m in diameter. It had solar arrays which were mounted along one side of the telescope and acted as a sunshield. The telescope observed anywhere on a strip of sky roughly perpendicular to the line joining SIRTF to the Sun, with about 35 percent of the sky visible to SIRTF at any one time. The spacecraft had a dry mass of 851 kg; at launch it carried 50 kg of helium cryogen, 16 kg of nitrogen for attitude control, and a 6 kg telescope cover which was ejected in solar orbit, for a total mass of 923 kg.

Associated Launch Vehicle: Delta 7000H.

• 2003 August 25 - SIRTF - Launch Site: Cape Canaveral. Launch Vehicle: Delta. Mass: 923 kg (2,034 lb).

  Originally to have launched January 9, 2003. Delayed six times. The Space Infrared Telescope Facility (SIRTF) was the last of NASA's 'Great Observatories'. It had a 0.85-meter infrared telescope, with a liquid-helium cooled focal plane carrying the three main instruments. SIRTF was launched by the second Delta II Heavy. The second stage entered a 166 x 167 km x 31.5 deg Earth parking orbit, and after about 33 minutes of coast, passing south of Madagascar, restarted at 0613 UTC to enter a hyperbolic orbit with a perigee of 170 km, an eccentricity of 1.0061, and a velocity of 11.05 km/s. This placed it in a solar orbit of 0.996 x 1.019 AU x 1.14 deg with a year about 4 days longer than Earth's.