SPACE.com compiled a list of the major observatories currently up doing space-based astronomy. The list excludes rovers, orbiters and planetary probes not doing traditional telescope observations.
Key for entries below: Telescope Name / Agency / Year Launched / Wavelengths / Primary Targets
Hubble Space Telescope / NASA, ESA / 1990 / Visible, UV, Near-IR / Deep Space Objects
The granddaddy of space telescopes, Hubble has been observing from Earth orbit for more than 19 years. Hubble, the first of NASA's Great Observatories, has revolutionized astronomy, providing stunning images of countless cosmic objects and giving astronomers their most distant views of the universe with the Hubble Deep Field and Ultra Deep Field. Hubble has shed light on the scale of the universe, the life cycle of stars, black holes, and the formation of the first galaxies. Currently receiving its fifth and final makeover, Hubble is expected to last at least another five years, hopefully overlapping with its successor, the James Webb Space Telescope.
Chandra X-ray Observatory / NASA / 1999 / X-ray / Various
The third of NASA's four Great Observatories, Chandra is the world's most powerful X-ray telescope. Chandra, named for Indian-American physicist Subrahmanyan Chandrasekhar, examines the X-rays emitted by some of the universe's strangest objects, including quasars, immense clouds of gas and dust and particles sucked into black holes. X-rays are produced when matter is heated to millions of degrees. Chandra has teamed up several times with other telescopes, including Hubble, to take composite images of galaxies and other denizens of the cosmos. It has found previously hidden black holes, provided observations of the Milky Way's own supermassive black hole, Sagittarius A*, and even taken the first X-ray images of Mars.
Spitzer Space Telescope / NASA / 2003 / IR / Distant and Nearby Objects
Spitzer was the last of the Great Observatories to be launched and gathers the infrared radiation emanating from cosmic objects, including faraway galaxies, black holes and even comets in our own solar system. (Infrared radiation is hard to observe from the ground because it is largely absorbed by the Earth's atmosphere.) Spitzer was the first telescope to see light from an exoplanet, which it was not originally designed to see; it took the temperatures of so-called "hot Jupiters" and found that not all of them are really hot. Spitzer is about to use the last of the liquid helium coolant that has kept its instruments chilled for the past 5.5 years. Spitzer's instruments will be able to keep going for another two years, meanwhile, the European Space Agency's Herschel telescope is designed to pick up where Spitzer left off.
Herschel Space Observatory / ESA & NASA / 2009 / Far-IR / Various
Herschel was lobbed into space on May 14, along with the Planck telescope. Herschel will be the largest, most powerful infrared telescope, looking at the far-infrared to sub-millimeter wavelengths of light generated by some of the coldest objects in space. Herschel is designed to look for water, both in nearby comets and faraway dust clouds, and will also peer into the womb of star formation. Astronomers expect to catch a glimpse of baby stars in the act of forming ? something they have never before been able to see. Like its predecessor Spitzer, Herschel will also take a peek at a few exoplanets.
Planck Observatory / ESA / 2009 / Microwave / Cosmic Microwave Background
Herschel's launch partner, the Planck Observatory, will be concentrating on the microwave light of the universe. Planck will be looking at the remnants of the first light to shine freely in the universe, the Cosmic Microwave Background (CMB). Planck will follow in the footsteps of NASA's Cosmic Background Explorer (COBE) and WMAP, mapping the CMB and providing the most detailed measurements of the temperature variations in the remnant light. Planck will also probe the mysteries of dark matter and dark energy and map the magnetic field of the Milky Way in 3-D.
Kepler Mission / NASA / 2009 / Visible / Extrasolar planets
Also new to the space scene is Kepler, NASA's new planet-hunting telescope that will specifically be searching for other Earth-like planets in the galaxy. Kepler will be looking for characteristic variations in the light from a pre-selected target group of 100,000 stars. Dips in the light from the stars can indicate a planet passing in front of the star (from Earth's perspective). Astronomers are hoping that Kepler fill find planets in the stars' habitable zones, where temperatures are just right for liquid water to exist. After getting settled into its new orbital home, Kepler officially began its search in May. First light from the telescope came on April 16.
Fermi Gamma-ray Space Telescope / NASA / 2008 / Gamma-ray / Various
Fermi (formerly GLAST) joined the ranks of the space telescopes last summer, and has already given astronomers their best-ever view of the most extreme energy in the cosmos: gamma rays. Gamma rays can reveal some of the most energetic and mysterious events in the universe, including dark matter, black holes and spinning pulsars. Not longer after arriving in orbit, it took an all-sky map that shows gamma rays from numerous sources, including our own sun. The Fermi team used the map to crate a "top 5" list of gamma ray sources. Fermi has also detected the highest energy gamma ray burst yet.
Swift Gamma Ray Burst Explorer / NASA / 2004 / Gamma ray, X-ray, UV, Visible / Various
Like Fermi, Swift also scans the sky for gamma rays, specifically looking for gamma-ray bursts (GRBs), the most powerful explosions in the universe. GRBs flash for just a few seconds before sliding into an afterglow of X-ray, ultraviolet and visible light. Swift can detect a GRB and within a minute point itself at the event for quick observations, with its instruments following along as the burst's light moves through the spectrum. In 2007, Swift spotted a GRB with the longest lived afterglow yet recorded, more than 125 days. Swift has also recorded the most distant cosmic explosion ever seen, a gamma-ray burst from a star that died when the universe was only 630 million years old, or less than 5 percent of its present age.
INTEGRAL / ESA / 2002 / Gamma ray, X-ray, Visible / Various
ESA's International Gamma-Ray Astrophysics Laboratory was the first space observatory that can simultaneously observe objects in gamma rays, X-rays and visible light. INTEGRAL, like Fermi and Swift, is tasked with looking for gamma-ray bursts, but it also keeps an eye out for supernova explosions and peers into regions in the universe thought to contain black holes. Astronomers hope that Integral's observations will help them learn more about how elements are formed when a star dies and could help us better understand the massive black hole lurking in the center of our own galaxy.
XMM-Newton / ESA / 1999 / X-ray / Various
Moving to shorter wavelengths in the electromagnetic spectrum, we have the X-ray Multi-Mirror Mission ? Newton, named in honor of Sir Isaac Newton. XMM-Newton's instruments allow it to make long, uninterrupted observations; it can detect more X-ray sources than any previous satellite. XMM-Newton has found detected galaxies billions of light years away from Earth, observed magnetars (a strange type of neutron star) and star-forming regions, and investigated what happens in and around black holes.
GALEX / NASA / 2003 / UV / Galaxies
The main mission of NASA's Galaxy Evolution Explorer is to help better understand the formation of galaxies. It studies the shape, brightness, size and distance of galaxies beyond the universe. Since its launch, GALEX has imaged more than a half-billion objects across two-thirds of the sky. The telescope's first observation, of the sky in the constellation Hercules, was dedicated to the crew of the Space Shuttle Columbia. GALEX has detected star formation in unexpected regions of the universe and spotting Mira, a fast-moving older star called a red giant.
COROT / CNES & ESA / 2006 / Visible / Extrasolar planets
Now we're back down to the spectrum to the wavelengths we humans can see. The Convection Rotation and planetary Transits mission has two objectives: to search for extrasolar planets that orbit close to their sun and to conduct stellar seismology. COROT spotted its first exoplanet in 2007. Earlier this year, COROT scientists made a controversial claim that the telescope had discovered the smallest known exoplanet. In 2008, it found an object that scientists think could either be a brown dwarf (a failed star) or a planet.
Solar & Heliospheric Observatory / NASA & ESA / 1995 / Optical-UV, Magnetic / Sun and Solar Wind
While other telescopes are busy looking at distant stars, SOHO is focused on our own. SOHO was designed to study the structure and dynamics of the interior of the sun, as well as the solar wind, the stream of charged particles ejected from the sun's upper atmosphere. Understanding these solar phenomena is key to making better predictions of space weather, such as solar flares, which can affect electrical grids and communication networks here on Earth. To date, SOHO has taken the first images of the sun's convection zone, shown the structure of sunspots below the sun's surface, and discovered new phenomena, such as solar tornadoes. SOHO has also spotted 1,500 new comets.
STEREO / NASA / 2006 / Visible, UV, Radio / Sun and Coronal Mass Ejections
Another solar observer, the STEREO (Solar Terrestrial Relations Observatory) mission is actually two separate spacecraft that after launch moved apart so that one trails Earth and the other leads it. These positions allow for stereoscopic imaging of the Sun and solar phenomena. STEREO has taken 3-D images of solar storms known as Coronal Mass Ejections (CMEs). These powerful solar eruptions are a major source of the magnetic disruptions on Earth, interrupting satellite operations, communications and power systems.
There are of course other missions being pursued by NASA, ESA and other space agencies; some are already up and space, while others are just in the planning phases.
One of the big missions scientists are anticipating is the James Webb Space Telescope, which will be the successor of Hubble. In fact, "it is designed specifically to build on Hubble's legacy," said Jon Morse, NASA's Astrophysics Division director.
It will search for light from the first stars and galaxies which formed in the universe after the Big Bang to better understand how stars and star systems form. The project has met some delays and cost overruns, and the telescope is currently slated to launch in 2013.
"That will be a decade of frontier astronomy with JWST," Morse said.
But JWST isn't the only telescope in the works, and Morse expects this golden age to continue for some time.
"There will continuously be interesting things to do with missions of all sizes, so I look forward to an exciting portfolio well into the coming decades," Morse said.