During the past few decades, infrared astronomy has become a major field of
science due to rapid advances in infrared detector technology. Many of
these advances arose from U.S Department of Defense research into infrared
array technology in the 1980's.
Infrared radiation, having longer wavelengths and lower energy than visible
light, does not have enough energy to interact with the photographic plates
which are often used in visible light astronomy. Instead, infrared astronomers
rely on electronic devices, to detect radiation.
Infrared detectors use infrared-sensitive materials, made from alloys of
exotic metallic substances, such as indium, antimony, silicon, mercury, cadmium,
germanium, and tellurium.
When infrared radiation falls on an infrared detector,
the electrical resistance of the detector changes.
This change in resistance is then measured and is related to the amount of
infrared radiation falling on the detector.
Since infrared detectors are extremely sensitive to heat, they must be kept
in an environment which is as cold as possible. This is done through the
use of cryogens such as liquid helium or nitrogen.
The development of infrared detector arrays in the 1980's, caused a giant leap
in the sensitivity of infrared observations.
Basically, a detector array is a combination of several individual detectors
arranged in a lattice-like array. The individual detectors in an array
are often called pixels - short for picture elements.
These pixel arrays convert energy from infrared radiation
into electrical signals, which are then converted into "bits" of digital data.
In 1983 the IRAS
mission used an array of
62 detectors. Astronomers now commonly use 256 x 256 arrays (thats 65,536
Infrared detector technology continues to advance at a rapid rate.
As a result, infrared astronomy has developed
more rapidly than any other field of astronomy and continues to bring us
exciting new views of the universe.
Detector array for the Spitzer Space Telescope's
The heart of the Spitzer Space Telescope's
instruments are its detectors. Spitzer will carry the best
infrared astronomical detectors to date.
Multiband Imaging Photometer for Spitzer (MIPS), which will observe in the
far-infrared, will detect objects 100 times fainter
than have ever been seen before. One of the MIPS cameras, which will operate at
70 microns (a micron is one millionth of a meter),
contains 1,024 detectors and is 100 times larger than previous arrays
operating in space. Each detector has about 30 times the
sensitivity of past detector arrays at this
Another MIPS camera, which is operated at 160 microns, has 10 times as many
detectors, with 10 times the sensitivity, as any previous array operated in space
at this wavelength.
Infrared Array Camera (IRAC) will produce
near-infrared images using four 256 x 256 pixel detector arrays!
Infrared Spectrograph (IRS)
will perform spectroscopy in the mid-infrared using
128 x 128 detector arrays.