The Infrared Astronomical Satellite (IRAS) was the first space-based telescope to attempt
a complete survey of the sky at infrared wavelengths.
IRAS detected some 350,000 sources in the mid-infrared (5-40 microns) and far-infrared
(40-100 microns), increasing the number of known astronomical objects by about 70%.
Among IRAS's discoveries were the first known disk of dust around a star (Vega), six new
comets, and a population of "ultraluminous infrared galaxies" that are much brighter at
infrared than optical wavelengths.
A joint project of the US, UK, and the Netherlands, IRAS was launched in 1983 and operated
for 11 months.
Kuiper Airborne Observatory
From 1971 to 1995, NASA's Kuiper Airborne Observatory (KAO) was the world's only airborne
telescope devoted exclusively to astronomical research. It observed in the infrared range
from 1 to 500 microns.
KAO made the first sighting of rings around Uranus and identified an atmosphere on Pluto.
A converted C-141 military cargo plane, it carried a telescope with a 36-inch mirror to an
altitude of 45,000 feet, greatly reducing the problem of interference from moisture in
IRAS's successor was the European Space Agency's Infrared Space Observatory (ISO),
which operated from November 1995 to May 1998. ISO observed in the range from
2.5 to 240 microns with greater sensitivity and resolution than its predecessor,
and made the startling discovery that water vapor is a common and important part
of the interstellar medium.
The satellite found water in the vicinity of stars both at the beginning and end
of their lives, in sources close to the center of the galaxy, and in the atmospheres
of planets in our Solar System.
ISO also discovered that most ultraluminous galaxies appear to be powered by
starbursts rather than by black holes.
Launched into low Earth orbit in December 1998, the Submillimeter Wave Astronomy
Satellite (SWAS) was a two-year NASA mission to enhance understanding of star
formation by studying the composition of interstellar clouds and the means by
which they collapse.
SWAS provided the most precise measurements of water vapor in interstellar clouds
and established the tightest limits on the maximum amount of molecular oxygen that
might be in these clouds.
Herschel will cover 1000 times more frequency "real estate" than SWAS, which observed
spectral lines at five specific submillimeter wavelengths: those of water, isotopic
water, molecular oxygen, neutral carbon, and isotopic carbon monoxide.
Hubble Space Telescope's NICMOS instrument
While the Hubble Space Telescope observes
primarily at optical wavelengths, the Near-Infrared Camera and Multi-Object Spectrometer
(NICMOS) extended the telescope's reach into the infrared when the instrument was added
NICMOS became inactive after two years when the nitrogen ice that cooled the system was depleted.
However, it was returned to service in March 2002, when space shuttle astronauts installed a new
cryogenic cooling system, extending NICMOS' operational life.
Launched in February 2001 with a two-year life expectancy, the Swedish Space
Corporation's Odin satellite has a dual purpose: to study star formation and
the early solar system, and to study Earth's atmosphere, where it will research
the mechanisms behind the depletion of the ozone layer and the effects of global
warming. Odin observes at 486-580 GHz and at 119 GHz.
Following up on the work of the
Cosmic Background Explorer (COBE)
satellite in 1992, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) is designed
to map the cosmic microwave background (CMB), the pervasive radiation from the
very early Universe.
COBE found that the CMB is amazingly uniform in all directions of the sky, yet
discovered subtle patterns that indicate that the Universe's structure, which
resembles "bubbles" of galaxies, developed early in its formation. WMAP is mapping
the CMB with much greater resolution, sensitivity, and accuracy than COBE, enabling
it to paint a much more detailed picture of the Universe.
WMAP was launched in June 2001, and reached the L2 point on October 1 of that year.
It will observe for two years, making a complete survey of the sky every six months.
Spitzer Space Telescope
Launched in August 2003, the Spitzer Space Telescope (formerly known as SIRTF)
is the infrared component of NASA's Great Observatories Program. It consists of
a 0.85 meter telescope with three cryogenically-cooled instruments that will perform
imaging and spectroscopy in the range of 3 to 180 microns. It is expected to be
operational for at least 2.5 years.
The Spitzer Space Telescope will search for brown dwarfs and super-planets, and
study ultraluminous infrared galaxies, AGNs, debris disks around nearby stars, and
the early Universe.
Astro-F (formerly IRIS, the Infrared Imaging Surveyor) is the second infrared
astronomy satellite of Japan's Institute of Space and Astronautical Science (ISAS),
which has now been integrated into the Japan Aerospace Exploration Agency (JAXA).
It builds on the work of Japan's Infrared Telescope in Space (IRTS), which operated
for one month in 1995 as part of the multi-purpose Space Flyer Unit satellite.
Currently under development, Astro-F employs a 69 cm telescope cooled to 6 K,
which will observe the infrared spectrum from about 2 to 200 microns. Its mission is
to investigate the formation and evolution of the galaxies, stars, and planets.
Scheduled to begin flying in 2004, the Stratospheric Observatory for Infrared Astronomy
(SOFIA) is the successor to the Kuiper Airborne Observatory. Like Kuiper, SOFIA represents
a compromise between space-based and ground-based observatories, offering greater
accessibility (though less observing time) than a satellite, and less interference
from the atmosphere (though more restrictions of size and weight) than a ground-based
This joint project of NASA and the German Aerospace Center uses a Boeing 747SP aircraft,
modified to accommodate a 2.5 meter reflecting telescope. SOFIA will be the world's
largest and most powerful airborne observatory, expected to operate three or four nights
a week for at least 20 years. It will be used to develop new observational instruments
and techniques, and to educate young scientists and teachers in infrared astronomy.
SOFIA will provide access to the entire mid-to-far infrared range of wavelengths, from 5
to 300 microns, part of which is inaccessible from the ground because of atmospheric moisture.
The European Space Agency's Planck spacecraft extends the work of COBE and MAP
in studying the structure of the cosmic microwave background as an indicator of the large-scale structure and history of the Universe.
Planck launched in early 2009, sharing a rocket with the Herschel Space
Observatory. Its baseline mission called for two complete scans of the sky during
15 months of observations but it has completed five full scans of the sky. It
continues on an extended mission, with LFI observations only, through early to mid 2013.
NASA's Next Generation Space Telescope (NGST) has now been named the James Webb Space
Telescope and the diameter is now set at 6 m with a launch date of 2013. It is expected
to be operational for 5 to 10 years.
JWST will explore the cosmology and structure of the Universe, the origin and evolution
of galaxies, the history of the Milky Way and its neighbors, the birth and formation of
stars, and the origins and evolution of planetary systems. Its mirror is expected to be
from six to eight meters, and will be able to collect light from the earliest galaxies.
Its cameras and spectrographs will be sensitive to the visible-to-mid-infrared range
between 0.6 and 10+ microns.
JWST will have better image resolution than Herschel and a "darker sky," since it will
not pick up far-infrared and submillimeter radiation from dust. But where Herschel will
be able to see through most dust clouds, JWST will have to look for views of distant
galaxies not blocked by dust.