Space Telescopes Across the Spectrum, From the Ultraviolet in 1978 to Exoplanet Transits in 2019

Launched in 1978 into geosynchronous orbit, it was the first space observatory designed mainly to take ultraviolet spectra. Visiting astronomers controlled its observations directly from ground stations, and it kept working for over eighteen years against a planned three.

The first space telescope to survey the entire night sky at infrared wavelengths, measuring at 12, 25, 60 and 100 micrometers. Its 73 kilograms of superfluid helium cooled the telescope to 2 K, and the survey ended in about ten months when that coolant ran out.

Not tied to one band of light, this European satellite measured where stars are. Launched in August 1989, it failed to reach its planned geostationary orbit and instead worked from an elongated orbit through the Van Allen belts, turning slowly to measure angles between widely separated stars and record their brightness.

A German-led X-ray satellite put into a 580 kilometer orbit at 53 degrees inclination in 1990. A four-fold nested Wolter I telescope focused X-rays that would pass straight through an ordinary mirror, and it made the first X-ray all-sky survey with an imaging telescope.

Launched on 7 June 1992 with instruments covering wavelengths of 7 to 76 nanometers, a slice of the spectrum that Earth's atmosphere absorbs. It catalogued hundreds of extreme-ultraviolet sources, mostly hot white dwarfs and active stellar coronae, before its mission ended in 2001.

Named after the physicist Bruno Rossi, this NASA satellite observed how X-ray sources vary in time. From a 409 kilometer orbit at 28.5 degrees inclination, its Proportional Counter Array combined five counters for fast timing of black holes, neutron stars, X-ray pulsars and X-ray bursts, until it was decommissioned in 2012.

Operating from 2001 to 2010, this NASA spacecraft sat at the second Sun-Earth Lagrange point, about 1,500,000 kilometers from Earth, which thermally stabilized it. Its differential radiometers compared two beams to map temperature differences in the cosmic microwave background, the work behind a universe age of roughly 13.8 billion years.

The European Space Agency launched this International Gamma-Ray Astrophysics Laboratory in 2002 to observe gamma rays up to 8 MeV. In the MeV range it was the most sensitive gamma-ray observatory in space, and it watched the same targets in X-rays and visible light at the same time.

Japan's infrared all-sky surveyor, launched on 21 February 2006 on an M-V rocket from the Uchinoura Space Center. Its 68.5 centimeter telescope, cooled to 6 K, mapped the sky in six infrared bands from 9 to 180 microns from a sun-synchronous polar orbit at 700 kilometers.

Active from 2009 to 2013, it was the largest infrared telescope ever launched until the James Webb Space Telescope in 2021, with a 3.5 meter mirror working in the far-infrared and submillimeter. The mission ended in 2013 when its liquid helium coolant was exhausted.

A NASA infrared survey telescope launched in December 2009 as Explorer 92. After its coolant was used up it was reactivated in 2013 as NEOWISE, a survey of asteroids and comets, so one spacecraft served two missions.

Launched on 13 June 2012 after a delay from 21 March caused by software issues with the launch vehicle. It uses a conical approximation to a Wolter telescope and a long deployable mast between mirrors and detectors to focus high-energy X-rays, and it studies black holes, supernova remnants and the high-energy Sun.

India's first dedicated multi-wavelength space telescope, launched in 2015 into a near-Earth equatorial orbit. Its six instruments, including an Ultra Violet Imaging Telescope and a Soft X-ray imaging Telescope, observe the same sources at the same time.

Launched on 18 April 2018 into a high Earth orbit with a period half that of the Moon. It watches for the repeated small dips in a star's brightness that reveal an orbiting planet, scanning broad swaths of nearby bright stars to find targets for follow-up.

Launched on 18 December 2019 into a sun-synchronous dusk-dawn orbit 700 kilometers above Earth. A 300 millimeter telescope with a single CCD measures the sizes of already-known exoplanets as they transit bright nearby stars, the last stop on a path from whole-sky surveys to single-planet measurements.