1800: Sir William Herschel discovers
infrared radiation. He
detects infrared light by measuring the temperatures in the colors of the solar
spectrum created by passing sunlight through a prism. The area just beyond
the visible red, in a region where there was no visible light, registered
the highest temperature. This discovery shows for the first time that there
are forms of light which we cannot see with our eyes.
Infrared radiation is detected from the moon by Charles Piazzi
Smyth from the peak of Guajara on Tenerife.
He uses a thermocouple (a device which converts heat into electric
current) to detect infrared light from the full moon.
Piazzi also tests observations
at different altitudes and shows that better observations are obtained
at higher altitudes. This is the first indication that our atmosphere
absorbs some of the infrared radiation from space.
The 4th Earl of Rosse detects infrared radiation from the moon during several
of its phases. He uses his infrared measurements to estimate that the Moon
has a surface temperature of about 500 degrees Fahrenheit.
(We now know that it is about 540 degrees Fahrenheit.)
This is a 1997 image of the eclipsed moon in the infrared.
The bolometer is developed by Samuel Pierpoint Langley. This instrument
is an electrical detector of radiant heat which can detect a broader range
of infrared wavelengths (far past the region of Herschel's discovery).
Langley's bolometer is sensitive to differences in temperature of one
hundred-thousandth of a degree Celsius (0.00001 C). The new bolometer is
used to study the intensity of infrared radiation from the Sun.
Infrared radiation is detected from Jupiter and Saturn and from some
bright stars, such as Vega and Arcturus.
In 1915, William Coblentz at the US National Bureau of Standards develops
thermopile detectors which he uses to measure
the infrared radiation from 110 stars. He also studies planets and nebulae
in infrared light.
William Coblentz would become the founder of modern infrared spectroscopy.
The first systematic infrared observations of celestial objects are
made by Seth B. Nicholson, Edison Pettit and other American astronomers.
They use a vacuum thermocouple to measure the infrared radiation from the
Moon, planets, sunspots, and stars. Their infrared studies allow them
to make some of the first measurements of the diameters of giant stars.
Infrared studies of the Moon reveal that its surface
is covered with a fine powder (more than 20 years before the moon landings).
Astronomers begin to use Lead-sulphide (PbS) detectors to study infrared
radiation. When infrared radiation in this range falls on a PbS cell it
changes the resistance of the cell. This change in resistance can
be measured and is related to the amount of infrared radiation
which falls upon the cell. To increase the sensitivity of the PbS
cell it is cooled to a temperature of 77 degrees Kelvin by
placing it in a flask filled with liquid nitrogen. The development of
PbS detectors allows astronomers to study the infrared radiation from space
out to a wavelength of about 3 microns (a micron is one millionth of a meter).
Harold Johnson builds the first near-infrared photometers covering the
R, I, J, K and L bands. This extends infrared research out
to a wavelength of 4 microns.
Johnson and his team measure thousands of stars in these new near
infrared bands, providing useful information on the radiation from cool stars.
Johnson defines the first infrared magnitude system.
The germanium bolometer is developed by Frank Low.
This instrument is hundreds of
times more sensitive than previous detectors and capable of
detecting far-infrared radiation.
When infrared radiation hits
the germanium, it warms the metal and changes its conductivity.
The change in conductivity can be measured and is
related to the amount of infrared radiation entering
the container. The germanium bolometer works best at an
extremely low temperature (much lower than liquid nitrogen). It
is placed in a metal container (Dewar) filled with liquid helium
which cools the bolometer to 4 degrees Kelvin (only a few degrees above
Balloons carry infrared telescopes up to altitudes as
high as 25 miles. In 1963, a germanium bolometer is attached to a balloon to
make infrared observations of Mars. Beginning in 1966, the Goddard Institute of
Space Sciences uses balloons to survey the sky at 100 microns. Their program
leads to the discovery of about 120 bright infrared sources near the plane of
our Milky Way Galaxy.
1967: Cooled infrared telescopes are placed on rockets which can observe the sky for several minutes before re-entry. The first infrared all-sky map results from a series of rocket flights by the Air Force Cambridge Research Laboratory. This project, called Hi Star, surveys the cosmos at wavelengths of 4, 10 and 20 microns. Although the total observation time accumulated by these flights is only about 30 minutes, they successfully detect 2363 reliable infrared sources which are published in the AFGRL Infrared Sky Survey. The Hi Star project continues until 1975.
1967: Mauna Kea Observatories is founded - soon to become a leading site for ground based infrared astronomy. New observatories, specializing in infrared astronomy, become possible in the 1960's due to advances in infrared detectors. At an elevation of 13,796 ft., the Mauna Kea Observatories are located above much of the infrared absorbing water vapor in the atmosphere.
Robert Leighton and Gerry Neugebauer make the first infrared survey of the sky
from the Mount Wilson Observatory by detecting infrared radiation in the
2.2 micron region.
This survey covers approximately 75 percent of the sky and finds about
20,000 infrared sources, which include star-forming regions, galaxies, our
galactic center and numerous stars. The brightest
5,500 of these sources make up the first catalog of infrared stars.
Mount Lemmon Infrared Observatory established in the Catalina Mountains of Arizona.
This observatory would become a leading site for infrared astronomy.
Early 1970's: Most galaxies are found to emit strongly in the infrared, including our own galaxy - the Milky Way. Quasars and other active galaxies are also found to be strong infrared emitters. This infrared image of the Andromeda galaxy was taken several years later (in 1983) by the IRAS satellite.
The Kuiper Airborne Observatory (KAO) begins research operations. The KAO is a
C-141A jet transport aircraft which carries an infrared telescope up to
altitudes of 41,000 feet - which is above 99 percent of the Earth's infrared-
absorbing water vapor.
The KAO, which would be used to gather infrared
data for the next 20 years, was used to discover the
rings of Uranus in 1977 and the presence of water in the atmospheres of
Jupiter and Saturn.
Mid-1970's: A far-infrared balloon borne spectrometer is used for three flights in the mid-1970 to test the Big Bang theory. To increase its sensitivity, the instrument is cooled to one degree above absolute zero by immersing it in a cryostat cooled with superfluid helium. This is the first time that such a low temperature is used for infrared observations. The observations provide the most widely accepted support for the Big Bang theory until the launch of the COBE satellite in 1989.
1980's: The development of infrared array detectors causes another giant leap in observational capability. A detector array is essentially a combination of several single detectors. This development greatly increases the efficiency of infrared observations and leads to the development of infrared cameras which can produce images much more quickly compared to using a single element detector. Infrared detector technology continues to advance at a rapid rate.
IRAS (Infrared Astronomical Satellite) is launched. For ten months IRAS
scans more than 96 percent of the sky four times, providing the
first high sensitivity all-sky map at wavelengths of 12, 25, 60 and 100 microns.
IRAS doubles the number of cataloged astronomical sources by
detecting about 500,000 infrared sources. IRAS discoveries included a disk of
dust grains around the star Vega, six new comets, and very strong infrared
emission from interacting galaxies,
as well as wisps of warm dust called infrared
cirrus which could be found in almost every direction of space. IRAS also
reveals for the first time the central core of our galaxy, the Milky Way.
1985: During July and August of 1985, an infrared telescope is flown onboard the Space Shuttle's Spacelab 2 to complement observations made by the IRAS mission. This mission produces a high quality map of about 60% of the plane of our Galaxy.
NASA launches the Cosmic Background Explorer (COBE) in November 1989,
to study both infrared
and microwave characteristics of the cosmic background radiation (the remains of
the extreme heat that was created by the Big Bang). Over the next four years,
COBE maps the brightness of the entire sky at several infrared wavelengths
and discovers that the cosmic background radiation is not entirely smooth,
showing extremely small variations in temperature. These variations may have led
to the formation of galaxies.
1990's The development of Adaptive Optics removes the blurring of ground-based astronomical images. This distortion of the light from space is caused by turbulence in Earth's atmosphere. Basically, adaptive optics takes a sample of light and calculates how much it has been distorted by the atmosphere. Deformable mirrors are then used to correct for this distortion and straighten the light. Adaptive optics works best at longer wavelength, producing excellent results for infrared telescopes. This system greatly improves the resolution of images taken by ground-based infrared observatories.
1993: The South Pole Infrared Explorer (SPIREX) begins operations taking advantage of the much lower thermal background at the very cold South Pole to gain better sensitivity. Another advantage is a very dark night sky, especially during the long, dark polar winter.
1995: The Infrared Telescope in Space (IRTS), launched in March 1995, is Japan's first infrared satellite mission. During its 28 day mission, IRTS surveys about 7% of the sky with four instruments. This data adds to our knowledge of cosmology, interstellar matter, late type stars and interplanetary dust.
The European Space Agency launches the Infrared Space
Observatory (ISO) in November 1995. ISO observes a very wide range of infrared
wavelengths between 2.5 and 240 microns (much wider than that covered by IRAS).
ISO is also thousands of times
more sensitive than IRAS and views infrared sources with much
better resolution due to advances in infrared technology.
ISO will collect data for about 2.5 years (3 times
longer than IRAS) before its cooling liquid helium runs out in early 1998.
This data leads to numerous new discoveries.
1996: DENIS - DEep Near Infrared Survey of the Southern Sky - begins operation. This ground based survey will survey the entire southern sky at 0.8, 1.25 and 2.12 microns using a 1 meter telescope at La Silla, Chile. The survey will continue until 2001.
The Midcourse Space Experiment (MSX) is launched in April 1996
and will last until its liquid helium coolant runs out in Feb 1997. During
its 10 months of operation, MSX gathers a vast amount of data at
4.2 - 26 microns. MSX studies the infrared emission from the gas
and dust which permeates the universe. It has 30 times the spatial
resolution of IRAS and surveys areas of the sky which were not covered
by the IRAS mission.
1997: 2MASS (Two Micron All-Sky Survey) begins operations. This highly uniform digital imaging survey of the entire sky uses two ground based telescopes to gather data at 1.25, 1.65 and 2.17 microns. Key science goals include probing the large-scale structure of the Milky Way and the Local Universe, performing an accurate census of stars in the solar neighborhood, and discovering brown dwarfs and active galactic nuclei. The survey continues until 2001, providing valuable data archives and spectacular infrared images.
1997: NICMOS (Near Infra-Red Camera and Multi-Object Spectrometer) is attached to the Hubble Space Telescope in February 1997. This infrared instrument, consisting of three cameras and three spectrometers, provides spectra and high resolution images in the near-infrared.
2001: The Keck Interferometer began operations in 2001. The Keck Interferometer is part of NASA's overall effort to find planets and ultimately life beyond our solar system. It will combine the light from the twin Keck telescopes to measure the emission from dust orbiting nearby stars, directly detect the hottest gas giant planets, image disks around young stars and other objects of astrophysical interest, and survey hundreds of stars for the presence of planets the size of Uranus or larger.
SIRTF (the Space Infrared Telescope Facility) is scheduled for launch in
April 2003. SIRTF will be NASA's next "great observatory" in space.
SIRTF will be much more sensitive than prior infrared missions and will
study the universe at a wide range of infrared wavelengths.
SIRTF will concentrate on the study of brown dwarfs, super planets,
protoplanetary and planetary debris disks, ultraluminous galaxies, active
galaxies, and deep surveys of the early universe.
SOFIA (Stratospheric Observatory For Infrared Astronomy) is scheduled
to begin operations in 2004.
SOFIA, a joint project between NASA and the German Space Agency, will
incorporate a 2.5 meter optical/infrared/sub-millimeter telescope mounted in a Boeing 747.
Designed as a replacement for the successful Kuiper Airborne Observatory,
SOFIA will be the largest airborne telescope in the world.
2004: IRIS (Infrared Imaging Surveyor) is planned for launch. IRIS is an infrared space mission planned by the Japanese space agency ISAS. It will have a near and mid-infrared camera and a far-infrared scanner. IRIS will be used to study the formation and evolution of galaxies, star formation, interstellar matter and extra-solar systems at wavelengths of 2-25 microns and 50-200 microns.
2007: The Herschel Space Observatory, planned for launch in 2007, is a European Space Agency infrared-submillimeter mission. Herschel will perform spectroscopy and photometry over a wide range of infrared wavelengths and will be used to study galaxy formation, interstellar matter, star formation and the atmospheres of comets and planets.
2007: Planck Surveyor, planned for launch in 2007, is a proposed European Space Agency far infrared-submillimeter mission. Planck will image the anisotropies of the Cosmic Background Radiation over the entire sky with exceptional resolution and sensitivity, and will provide a uniform submillimeter map of the sky.
2010: The James Webb Space Telescope, planned for launch in about 2009, is a visible/infrared space mission which will have extremely good sensitivity and resolution, giving us the best views yet of the sky in the near-mid infrared. NGST will be used to study the early universe and the formation of galaxies, stars and planets.
2012: TPF (Terrestrial Planet Finder), scheduled for launch in about 2011, is envisioned as a long baseline interferometer space mission. TPF will concentrate on detecting terrestrial planets (small and rocky planets - like Mercury, Venus, Earth and Mars) orbiting nearby stars. By studying near infrared spectral lines, astronomers will also detect several molecules which may provide indications of whether the planets can sustain life.
Darwin (space infrared interferometer project) is a candidate for the European
Space Agency's infrared interferometer space mission.
The primary goal of Darwin is to search for Earth-like planets around nearby
stars, and to search for signs of life on these planets by studying infrared
spectral lines in their atmospheres.
Darwin would also be used as a general infrared astronomy observatory.
The Darwin project would consist of about 6 individual telescopes combined
as an interferometer about 100 meters across and would orbit between Mars
and Jupiter, beyond the zodiacal dust which radiates infrared light at
the wavelengths which will be used to search for planets.