Spitzer Space Telescope

The Spitzer Space Telescope is a space-based infrared telescope studying objects ranging from our Solar System to the distant reaches of the Universe. Spitzer formerly called SIRTF (Space Infrared Telescope Facility) was the fourth and final element in NASA’s Great Observatories Program.  It was launched by a Delta rocket from Cape Canaveral, Florida on 25 August 2003 and is still currently in operation.

Mission

The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory. Science operations are conducted at the Spitzer Science Center at Caltech. Spitzer’s infrared spectrograph was built by Cornell University, Ithaca, New York. Its development was led by Dr. Jim Houck of Cornell.

During its mission, Spitzer 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.

An important feature of the Spitzer mission is the adoption of a solar orbit. To reach this orbit, the spacecraft was launched on a Delta 7920 launch vehicle with slightly greater than terrestrial escape velocity. The resulting orbit has Spitzer trailing the Earth in its orbit around the Sun. It permits uninterrupted viewing of a large portion of the sky without the need for Earth-avoidance manoeuvres. In addition, the absence of heat input from the Earth provides a stable thermal environment and allows the exterior of the telescope to reach a low temperature via radiative cooling.

Spitzer’s highly sensitive instruments 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 centres 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.

About spacecraft

The Spitzer Space Telescope features many innovations never before used on a space mission. The Observatory is comprised of two major components: the Cryogenic Telescope Assembly (which contains the telescope and Spitzer’s three main instruments) and the spacecraft. Because the telescope must be cooled to only a few degrees above absolute zero to function properly and the spacecraft needs to operate near room temperature, sometimes these two major components are referred to as the “cold” and “warm” portions of the Observatory.

Spacecraft

The spacecraft consists of an octagonal bus structure in which the avionics and the science instrument’s warm electronics are housed and a solar panel that provides electrical power to the vehicle and serves to shade the cryo-telescope assembly from direct exposure to the sun. The spacecraft provides electrical power to the science instruments, orients and stabilizes the boresight of the telescope, collects and compressed data from the science instruments for later transmission to the ground, executes stored commands to direct science instrument activities, and communicates with the ground system. All communications with Spitzer is conducted through NASA’s Deep Space Network.

The telescope is surrounded by an outer shell that radiates heat to cold space in the anti-Sun direction and is shielded from the Sun by the solar panel assembly. Intermediate shields intercept heat from the solar panel and the spacecraft bus. The outer shell and inner, middle, and outer shields are vapour cooled, i.e., the cold helium vapour from the helium tank is used to carry away the heat from these structures. 

Telescope

The Spitzer telescope is a lightweight reflector of Ritchey-Chrétien design. It weighs less than 50 kg and is designed to operate at an extremely low temperature. The telescope has an 85 cm diameter aperture. All of its parts, except for the mirror supports, are made of light-weight beryllium. Beryllium is a very strong material which works well in the construction of infrared space telescopes because it has a low heat capacity at very low temperatures. The telescope is attached to the top of the vapour-cooled cryostat vacuum shell, which keeps the science instruments very cold.

Info and Facts

Launch Date: 25 August 2003
Launch Vehicle/Site: Delta 7920H ELV / Cape Canaveral, Florida
Estimated Lifetime: 2.5 years (minimum); 5+ years (goal)
Orbit: Earth-trailing, Heliocentric
Wavelength Coverage: 3 – 180 microns
Telescope: 85 cm diameter (33.5 Inches), f/12 lightweight Beryllium, cooled to less 5.5 K
Diffraction Limit: 6.5 microns
Science Capabilities: Imaging / Photometry: 3-180 microns; Spectroscopy: 5-40 microns; Spectrophotometry: 50-100 microns
Planetary Tracking: 1 arcsec / sec
Cryogen / Volume: Liquid Helium / 360 liters (95 Gallons)
Launch Mass: 950 kg (2094 lb) Observatory: 851.5 kg, Cover: 6.0 kg, Helium: 50.4 kg, Nitrogen Propellant: 15.6 kg

Who was Lyman Spitzer?

Highlights

February 2007:
NASA’s Spitzer Space Telescope has captured for the first time enough light from planets outside our solar system, known as exoplanets, to identify molecules in their atmospheres. The landmark achievement is a significant step toward being able to detect possible life on rocky exoplanets and comes years before astronomers had anticipated.

Spitzer, obtained the detailed data, called spectra, for two different gas exoplanets. Called HD 209458b and HD 189733b, these so-called “hot Jupiters” are, like Jupiter, made of gas, but orbit much closer to their suns.

Spitzer Telescope is able to make observations that are more sensitive than any previous mission. While the Spitzer cryogenic lifetime requirement is 2.5 years of normal operations, which was passed on April 26, 2006, current estimates indicate an expected cryogenic lifetime of about 5 1/2 years.

Did you know?

* Spitzer is the only one of the Great Observatories not launched by the Space Shuttle. It was originally intended to, but after the Challenger disaster, the Centaur LH2/LOX upper stage that would have been required to push it into its intended orbit was banned from Shuttle use. The satellite underwent a series of redesigns during the 1990s, primarily due to budget considerations. This resulted in a much smaller, although still fully capable, mission which could use the smaller Delta launch vehicle.

* Spitzer is the final mission in NASA’s Great Observatories Program – a family of four orbiting observatories, each observing the Universe in a different kind of light (visible, gamma rays, X-rays, and infrared). Other missions in this program include the Hubble Space Telescope (HST), Compton Gamma-Ray Observatory (CGRO), and the Chandra X-Ray Observatory (CXO). Spitzer is also a part of NASA’s Astronomical Search for Origins Program, designed to provide information which will help us understand our cosmic roots, and how galaxies, stars and planets develop and form.

Related Books: 

Planet Quest: The Epic Discovery of Alien Solar Systems by Ken Croswell
From Amazon.com

Distant Wanderers: The Search for Planets Beyond the Solar System by Bruce Dorminey
From Amazon.com

Spitzer Space Telescope Links:

Spitzer Space Telescope: Official site of California Institute of Technology
NASA –  Spitzer Telescope:
SST (Spitzer Space Telescope): from Ballaerospace.com

Reference:

Picture Source of Spitzer: 25/5/2007
http://www.spitzer.caltech.edu/Media/041018telecon/sst.shtml