Telescopes in Space
Just over 50 years ago, NASA launched the first telescope in space. A set of telescopes, actually, placed aboard the Orbiting Astronomical Observatory (OAO-2). These first space telescopes opened up a whole new way to research the universe.
Ground-based telescopes operate under the protective yet challenging cloak of Earth’s atmosphere, which blocks certain wavelengths of light from observation and distorts views with turbulence. By orbiting above the Earth’s surface, space observatories have surmounted these limitations and given astronomers a truer vision of the Universe and its inspiring sights.
When telescopes move beyond the limits of our atmosphere, research possibilities explode because the full electromagnetic spectrum is suddenly open for observation. There are seven types of energy wavelengths that make up this spectrum: radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray. While all visible light and most radio waves pass through the atmosphere, X-ray and gamma ray wavelengths are completely shut out. Narrow segments of the three remaining categories — microwave, infrared and ultraviolet — can reach Earth-based observatories, but observations in these bands are more successful when done from space.
More than 100 orbiting telescopes have been launched since the OAO-2. Although the Hubble Space Telescope arguably made the biggest splash, it is only one member of an ever-evolving astronomical army that is advancing humanity’s understanding of the universe.
Hubble Space Telescope
Wavelength Type: Visible and ultraviolet
Agency: NASA & ESA
Launch Date: April 25, 1990
Launch Site: Space Shuttle Discovery
On April 25, 1990, a whole new era of cosmic observation began with the deployment of the Hubble Space Telescope (HST) from the cargo bay of the Space Shuttle Discovery. The HST was built through a cooperative effort of the National Aeronautics and Space Agency (NASA) and the European Space Agency (ESA) and operated by the Space Telescope Science Institute (STScI).
Hubble, the first of the four space telescopes in NASA’s Great Observatories program, made its first observation on May 20, 1990. The subject was the open cluster NGC 3532 in the constellation of Carina, but operators discovered that the reflecting telescope’s 2.4-meter primary mirror had a spherical aberration that was affecting image clarity. On December 2, 1993, the first servicing mission was launched, and through a series of complex repairs by a team of astronauts the flaw was corrected and the stunning images that Hubble is known for today began to populate.
In nearly twenty-nine years of operation, Hubble has traveled more than 3 billion miles and made more than a million observations. In addition to providing beautiful views of the cosmos, the Hubble Telescope has dramatically refined estimates of the age of the Universe, revealed the farthest galaxies ever seen, and collected scores of data on topics like exoplanets, quasars, black holes, dark energy, and dark matter.
As of February 2019, Hubble is still going strong, but regardless of the length of time the Hubble Space Telescope ultimately survives, it will go down in history as an amazing instrument that has expanded humanity’s knowledge of the solar system, the Milky Way galaxy, and the Universe itself.
AGILE (Astro-rivelatore Gamma a Immagini LEggero)
Wavelength Type: Gamma ray and x-ray
Agency: Agenzia Spaziale Italiana
Launch Date: April 23, 2007
Launch Site: Sriharikota Base in India
For a relatively small space observatory, AGILE has had a big impact in the field of high-energy astrophysics research during its nearly twelve-year orbit.
Since its launch on April 23, 2007, AGILE has been on a mission to scan wide expanses of deep space and collect valuable data on both persistent and transient gamma ray sources. The satellite’s instrument core is a compact 2-foot cube, weighing about 220 pounds, that houses a gamma ray imaging detector with a mini-calorimeter, an x-ray imager, and an anti-coincidence system. Funded, produced, and operated solely in Italy, AGILE has an impressive field of view that encompasses about a fifth of the celestial sphere at any one time and uses its combination of gamma ray and x-ray detection devices to target activity in the 30 MeV to 50 GeV and 10 to 40 keV energy bands. AGILE also has the valuable ability to communicate its gamma ray detections quickly. Gamma ray bursts can be fleeting events, and this responsive data relay system allows other land and space observatories to follow up on the instrument’s finds with observations in multiple wavelengths.
Through the years, AGILE has opened up the field of gamma ray research. One of its most astounding finds was the discovery in September 2010 of strong gamma ray flares within the Crab Nebula, which challenged the belief that the system’s gamma ray and x-ray emissions were stable. The findings called long-standing models of particle acceleration into question and earned the AGILE team the American Astronomical Society’s prestigious Bruno Rossi Prize in 2012.
NuSTAR (Nuclear Spectroscopic Telescope Array)
Wavelength type: X-ray
Launch Date: June 13, 2012
Launch Site: Kwajalein Atoll, Republic of the Marshall Islands
On June 13, 2012, NASA’s NuSTAR observatory hitched a ride into a perfect low-Earth equatorial orbit aboard a Pegasus rocket dropped from an airplane flying at 40,000 feet. It was a flashy entrance for a relatively small space observatory, but in the years since, NuSTAR has proved it was worth the hype.
Part of NASA’s Small Explorer program, NuSTAR is an x-ray telescope that employs true focusing optics to get high-caliber images of X-rays with energies reaching up to an astounding 79 keV. In its surveys of high-energy sources like black holes, supernovae explosions, and neutron stars, NuSTAR has obtained a wealth of scientific data. One mission highlight was the surprising 2014 identification of a pulsar as an ultraluminous x-ray source — a role previously thought to belong exclusively to black holes. NuSTAR also has played a critical role in settling the debate over how stars explode through analysis of titanium in the supernova remnant Cassiopeia A.
Successes like these are due in large part to innovative choices made during NuSTAR’s design phase. In terms of optics, the team tweaked the traditional x-ray telescope design used in predecessors like the Chandra X-ray Observatory. X-ray light reflects off surfaces at glancing angles so x-ray telescopes have to use mirror shells of different sizes and angles nested inside one another to capture the beams. To snag the higher energy X-rays they wanted to target, NuSTAR designers had to dramatically increase the number of mirrors and maximize the reflectivity with a combination of both high-density and low-density specialized coatings. According to figures in the mission’s press kit, Chandra was designed with four shells of mirrors ranging between 2 to 3 centimeters in thickness. NuSTAR, by comparison, has 133 shells that are only .02 centimeters thick.
NuSTAR designers also had to figure out a way to get the 10 meters (33 feet) of focal length it required while still keeping the observatory compact enough to hitch a ride into space. Unlike the fixed structures of previous missions, NuSTAR has an extendable mast that was stowed away during launch and deployed after the observatory was in orbit. An adjustment mechanism on the mast keeps the telescope and the x-ray detectors aligned for precision performance.
Hisaki | Sprint A
(Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere)
Agency: Japan Aerospace Exploration Agency
Launch Date: Sept. 14, 2013
Launch Site: Uchinoura Space Center in Japan
While we may know more about Jupiter and other members of our Solar System than exotic objects in the deepest reaches of space, our planetary neighbors still have countless mysteries to unravel. More than five years ago, the Japan Aerospace Exploration Agency launched a space-based extreme ultraviolet spectroscope dedicated to remote observation of planets in our solar system with a particular focus on the Jovian system. The Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere (SPRINT A), also known as Hisaki, captures extremely short wavelengths of ultraviolet light that cannot be studied using ground-based resources due to their inability to make it through Earth’s atmosphere.
The observatory was designed to study the relationships between solar winds and the magnetospheres and atmospheres of certain planets. Jupiter has been a main target of Hisaki’s investigations because of its extremely strong magnetosphere. From the beginning, planned observations included studying the plasma flowing off of Io – one of Jupiter’s four Galilean moons — and gaining insight into how solar winds affect atmospheric evolution by recording the atmospheric components flowing out of certain planets. Among other revelations about Jupiter’s aurora, the telescope’s long-term observations of Jupiter have shown that solar wind has a significant influence on Jupiter’s inner magnetosphere.
BRITE Constellation (Bright Target Explorer)
Agencies: Universities in Austria, Canada, Poland
Launch Dates: from February 2013 to August 2014
Launch Sites: India, Russia, and China
The BRITE Constellation mission is a network of nanosatellites launched into orbit in four separate batches with a shared mission to study stellar seismology. The grouping was set to include six nanosats, which are each similar in size to a car battery, however one went astray and is assumed lost. In the years since, the remaining five have been diligently studying the most luminous stars in the night sky though high-resolution imaging with either blue or red filters.
The unique configuration of the BRITE Constellation allows for long monitoring periods of target stars and fields — which is something that is critical when collecting data on stellar variability. Information gleaned from BRITE’s observations address topics like pulsation, rotation, wind variations, star-disk interactions and more. BRITE has captured the full cycle of a nova, determined that the speed of rotation of Alpha Circini is decelerating, calculated the masses of the stars in the triple star system Beta Centauri, and recorded a “pulsation-driven mass transfer” from Eta Centauri to a gaseous disc surrounding it.
Spektr-R (RadioAstron Project)
Agency: Astro Space Center of PN Lebedev Physics Institute, Russia
Launch Date: July 18, 2011
Launch Site: Baikonur, Kazakhstan
Since radio wavelengths are not generally deterred by Earth’s atmosphere, there is a wealth of ground-based resources for radio observation. Some of these resources work in tandem to create a bigger receiver through a technique called interferometry. In this process, data from two radio telescopes is combined. The resulting images have better resolving powers than a single receiver could generate because the distance between the two telescopes now acts as a single aperture. The farther apart the two receivers are, the better the resolving power. The “apertures” you can get using this technique between ground resources is impressive but imagine if one of those receivers was in space. As one NASA site puts it, “By putting a radio telescope in orbit around Earth, radio astronomers can make images as if they had a radio telescope the size of the entire planet.”
In 2011, Russia launched its long-anticipated radio telescope Spektr-R into orbit and exponentially expanded our ability to observe the radio portion of the electromagnetic spectrum. Spektr-R has a 10m (32.8ft) parabolic dish made of twenty-seven carbon fiber petals that were deployed once the satellite was in position. Spektr-R, which is in an extremely elliptical orbit that stretches nearly to the Moon, works with ground-based radio telescopes as part of the RadioAstron project to study galactic and extragalactic sources of radio waves like Active Galactic Nuclei (AGN). These combined efforts have resulted in amazing discoveries. For example, Spektr-R worked with four ground-based resources — Green Bank Telescope in West Virginia, the Very Large Array in New Mexico, Effelsberg Telescope in Germany and Arecibo Observatory in Puerto Rico —to create a virtual radio telescope more than 100,000 miles wide. This massive receiver was used to study jets emanating from quasar 3C 273, and common understandings of the phenomenon were summarily upended. Prior to the RadioAstron observations, it was estimated that the temperature of these jets was at most 100 billion degrees. Researchers discovered the temperature actually surpasses 10 trillion degrees!
Launch Date: Dec. 10, 1999
Launch Site: Kourou in French Guiana
Almost 20 years ago, XMM-Newton was launched into orbit as the second “Cornerstone” mission in the European Space Agency’s ambitious Horizon 2000 program. Originally known as XMM as a call-out to its multi-mirror design, this massive x-ray telescope was renamed XMM-Newton in 2000 to honor physics icon, Sir Isaac Newton.
The equipment on board the XMM Newton is composed of three x-ray telescopes that include a mirror module consisting of a nest of 58 concentric mirrors, three photon imaging cameras designed to detect variations in x-ray wave intensity at stunning speeds, and two reflection grating spectrometers (RGS) that allow for more detailed analysis of the individual elements in a wavelength. In addition to its X-ray capabilities, the highly versatile XMM-Newton is also equipped with an optical monitor that allows for observations in the visible and ultraviolet wavelengths. With this plethora of equipment and a 48-hour orbital period that allows for long uninterrupted observations, it is easy to understand how the XMM-Newton has contributed to more than 5,000 published papers.
Some of its discoveries also can be attributed to the intentional choice to leave the instruments going as the telescope slews between chosen targets. These random sky surveys have revealed astounding surprises, such as a pair of supermassive black holes orbiting around one another in a “quiescent” galaxy. Until that observation, the few binary supermassive black holes that have been discovered were only in active galaxies. Another intriguing XMM-Newton mission highlight was witnessing the prolonged death of a star that was consumed at an agonizingly slow rate by a rare intermediate-mass black hole for more than a decade. Other cornerstone missions in the ESA’s Horizon 2000 program include SOHO (Solar and Heliospheric Observatory), Rosetta, and the Herschel Space Observatory.
Neil Gehrels Swift Observatory (Swift Gamma Ray Burst Explorer)
Wavelengths: Gamma ray, x-ray, ultraviolet, visible
Agencies: NASA with contributions from the Italian Space Agency and the United Kingdom’s Particle Physics and Astronomy Research Council
Launch Date: Nov. 20, 2004
Launch Site: Cape Canaveral Air Force Station in Florida
Just over 14 years ago, the Swift observatory was sent into orbit with a focused mission to study the flashiest phenomena in the known universe — gamma ray bursts. These brilliant yet fleeting celestial events have been the subject of much debate ever since they were first observed in the 1960s. Cracking the mysteries of gamma ray bursts is far from easy because they cannot be predicted and last anywhere from a few milliseconds to a few minutes. With these hurdles in mind, the Swift Gamma Ray Burst Explorer was designed to acquire the position of a detected gamma ray burst and relay that information to ground-based resources within 20 seconds and then slew to the burst’s location within 75 seconds to begin analyzing the burst’s afterglow in multiple wavelengths; the afterglow can linger much longer than the burst itself.
The observatory is outfitted with three telescopes — a burst alert telescope that has a large field of view, an x-ray telescope, and an ultraviolet/optical telescope that is as sensitive as a 13-foot optical ground-based telescope even though it is only 11.8 inches. Over the years, Swift has captured more than 1,000 gamma ray bursts and become a legend in time domain astronomy — the study of how astronomical objects change with time. Among its achievements is the discovery of a new ultra-long class of gamma ray bursts, the validation of a theory that short duration bursts — which are defined as those lasting less than two seconds — are related to the merger of two neutron stars and the observation of the farthest gamma ray burst. At one point, Swift also observed a burst that briefly blinded its x-ray telescope when it emitted 143,000 x-ray photons per second at its maximum brightness. It has also been employed to survey other objects like galaxies, comets, and asteroids.
Chandra X-Ray Observatory
Launch Date: July 23, 1999
Launch Site: Space Shuttle Columbia
One of NASA’s four “Great Observatories”, the Chandra X-Ray Observatory jettisoned from the bay of space shuttle Columbia nearly two decades ago and began an epic mission to study the hottest spots in the Universe. Named for the Nobel Prize-winning astrophysicist, Subrahmanyan Chandrasekhar, Chandra is an x-ray observatory with an orbit that reaches about one-third of the distance to the Moon — allowing for long, uninterrupted observing sessions that can last more than 50 hours. The telescope, which has a resolving power of 0.5 arc seconds, has a 10m focal length and an assembly of four nested pairs of mirrors coated with iridium and highly polished. NASA publications often emphasize the smoothness of Chandra’s mirrors by saying that “if Colorado was as smooth as Chandra’s mirrors, Pikes Peak would be less than one inch tall.”
Other science instruments on board Chandra are two transmission gratings, an advanced CCD imaging spectrometer, and a high-resolution camera. The contributions Chandra has made to the field of astrophysics are immeasurable. A few of the highlights include advancing dark matter research through its imaging of galaxy cluster collisions, providing new insight into the relationship between pulsars and nebulae through its study of the Crab Nebula, confirming the existence of a new classification of black holes —the mid-mass black hole, and monitoring the Alpha Centauri system for a decade to produce valuable data on habitability of the closest star system to our own.
Wavelength: X-ray, ultraviolet, visible
Agency: Indian Space Research Organization (ISRO)
Launch Date: Sept 28, 2015
Launch Site: Satish Dhawan Space Centre in Sriharikota, India
If a person had to describe India’s first space observatory in one word, that word would have to be “versatile”. AstroSat is a multi-wavelength observatory that can study the same object or field of view in the visible, ultraviolet, soft x-ray and hard x-ray ranges simultaneously. It is outfitted with five instruments: The Ultraviolet Imaging Telescope (UVIT), the Soft X-ray Telescope (SXT), the Large Area X-Ray Proportional Counters (LAXPC), the Cadmium-Zinc-Telluride Imager (CZTI) and the Scanning Sky Monitor (SSM). The ultraviolet telescope has an impressive field of view — 80 times larger than Hubble’s — but can still image with excellent resolution. This makes it ideal for deep field studies.
In the few years that AstroSat has been in orbit, it has already made major contributions. Using the CZTI, the AstroSat team was able to successfully tackle the difficult task of measuring the x-ray polarization of the pulsar in the Crab Nebula. The measurements challenged existing theories of how the pulsar produces X-rays and opened up the x-ray polarization field of study. In another highlight, the LAXPC was used to capture oscillations in the black hole system of GRS 1915+105 in high-energy X-rays. Although this system had been observed in low-energy X-rays, LAXPC added another dimension to the understanding of what is happening in the system.
Hard X-Ray Modulation Telescope (Insight)
Agency: China National Space Administration (CNSA)
Launch Date: June 14, 2017
Launch Site: Jiuquan Satellite Launch Center in Inner Mongolia
The launch of the Hard X-Ray Modulation Telescope marked China’s entrance into the orbiting telescope domain. The astronomy satellite, which was given the moniker Insight after its successful launch, is the first in a series of planned Chinese space observatories. The observatory includes three x-ray telescopes designed to detect three separate ranges of x-ray energy — high, medium, and low. Unlike other x-ray observatories, Insight uses a demodulation method instead of the traditional grazing mirror design to capture x-ray photons. This was done for utilitarian reasons, but it also will allow Insight to observe targets that are so bright they might temporarily blind other x-ray telescope resources.
The satellite’s mission includes scanning our galaxy for transient x-ray sources, observing the behavior of neutron stars that exist in conditions that feature strong gravity and magnetic fields, and detecting and studying gamma ray bursts to further humanity’s understanding of gravitational waves.
Spitzer Space Telescope
Launch Date: Aug. 25, 2003
Launch Site: Cape Canaveral Air Force Station in Florida
Thanks to creative design choices that conquered budgetary challenges, the Spitzer Space Telescope claimed its rightful place as the fourth and final member of NASA’s “Great Observatories” fleet more than fifteen years ago. The observatory targets infrared wavelengths, which is essentially the heat radiating from celestial objects. To avoid interfering with the heat signatures the Spitzer mission was designed to capture, the scientific instruments on board Spitzer had to be as cold as possible. To meet this critical temperature but stay within a tight budget, the designers made unique choices that included launching the observatory warm and then passively cooling it for three months and eventually putting it into a heliocentric orbit that leaves it trailing Earth on the planet’s journey around the Sun. Although the spacecraft is drifting away from Earth at the rate of about 1/10th of one astronomical unit per year, the unusual orbit has helped protect the observatory from the Earth’s heat and made it possible to view about a third of the sky at any one time. The instruments Spitzer uses are housed in a Cryogenic Telescope Assembly.
The Ritchey-Chrétien telescope has a 33.46-inch aperture and is made of a material that can be cooled very quickly. It sits atop the Cryostat chamber housing the observatory’s three scientific instruments —the Infrared Array Camera (IRAC), the Infrared Spectrograph (IRS) and the Multiband Imaging Photometer (MIPS).
On May 15, 2009, the coolant Spitzer depended on to keep all of its instruments viable finally ran out, and the observatory embarked on a “warm” mission using just two of the IRAC’s four detectors to study comets, asteroids, exoplanets and more. During both the “cold” and “warm” mission phases, Spitzer has made astounding scientific contributions. Highlights include discovering an enormous ring around Saturn that was previously undetected, helping analyze material ejected from Comet Tempel 1 when it was intentionally hit by NASA’s Deep Impact spacecraft, producing the first ever “weather map” of an exoplanet, identifying molecules in the atmospheres of exoplanets, revealing carbon is more abundant in our own Milky Way Galaxy than expected, determining the densities of the intriguing Earth-size planets in the TRAPPIST-1 system, and detecting the most distant proto-cluster of galaxies.
Transiting Exoplanet Survey Satellite (TESS)
Launch Date: April 18, 2018
Launch Site: Cape Canaveral Air Force Station: SpaceX Launch Complex 40 in Florida
Although it has been in orbit less than a year, NASA’s Transiting Exoplanet Survey Satellite has already picked up the mantle left by the highly successful Kepler Space Telescope, which identified thousands of exoplanets in its nine-year run. TESS is seeking to dramatically expand the catalog of known exoplanets through a two-year, all-sky survey encompassing an area 400 times larger than that covered by Kepler.
Exoplanets are planets orbiting stars other than our own, and the best way to find them is by monitoring stars for temporary but regular drops in brightness that indicate a transiting body. Over the next two years, TESS will focus on monitoring the brightest 200,000 stars because the exoplanets discovered around these are more likely to yield additional information like atmospheric composition, structure, and interactions with other planets and moons. The observatory is focusing on the Southern Hemisphere for the first year and the Northern in the second year. To make its observations, TESS has four red-sensitive CCD cameras that each have a wide 24° x 24° field of view, 100mm of aperture, and excellent resolution. The spacecraft’s high Earth orbit takes 13.7 days and provides these cameras with a mostly unobstructed view.
In its first few months of operation, TESS already has found three confirmed exoplanets and identified hundreds of candidates. The first of these confirmed finds was Pi Mensae c – an exoplanet about double Earth’s size that is orbiting a star similar to our own and is about sixty light years away. It also found a rocky planet about forty-nine light years away and a planet much larger than our own that is the longest-period transiting planet within 100 light years.
International Gamma Ray Astrophysics Laboratory (INTEGRAL)
Wavelength: Gamma ray, x-ray, optical
Agency: International mission
Launch Date: Oct. 17, 2002
Launch Site: Balkonur, Kazakhstan
Though launched in 2002, The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) began its journey in June 1993 when it was selected by the European Space Agency for the next medium-size scientific mission (M2) of the Horizon 2000 program. INTEGRAL’s mission is primarily led by the ESA but with cooperation from Russia and NASA.
INTEGRAL launched into space in search of the most energetic radiation that exists in space through fine spectroscopy and fine imaging. The telescope’s defining feature is being able to simultaneously observe gamma rays, X-rays, and visible light. Just some of the intense principle targets of this space telescope are supernova explosions and regions of space where black holes are thought to be located.
The information is collected by four instruments on board INTEGRAL, and that information is then relayed to scientific teams in Italy, France, Germany, Denmark, and Spain where the gamma ray data is analyzed. The first of these instruments is the SPI (Spectrometer on INTEGRAL) which uses nineteen hexagonal high purity germanium detectors to measure gamma-ray energies with extreme precision. The next instrument is the IBIS, the imager on-board. This gives INTEGRAL the capability of capturing sharper gamma-ray images than any instrument could capture before. The third instrument is the Joint European X-Ray Monitor (JEM-X). The JEM-X detects and identifies gamma-ray sources, and it aids in providing images in the 3 to 35 keV prime energy band with an angular resolution of 3 arcmin. The final instrument on INTEGRAL is the OMC, the optical camera, which allows INTEGRAL to make long observations of visible light from gamma rays and X-rays.
Fermi Gamma-ray Space Telescope
Wavelength: Gamma ray
Launch Date: June 11, 2008
Launch Site: Cape Canaveral Air Force Station: SpaceX Launch Station Complex 17 in Florida
The Fermi Gamma-ray Space telescope, originally known as GLAST, was launched from Complex 17 of the Cape Canaveral Air Force Station at 12:05pm with one mission: Explore the “numerous exotic and beautiful phenomena” that exist in the Universe through gamma-ray radiation. Some of the celestial objects this telescope set out to explore were supermassive black holes, merging neutron stars, streams of hot gas moving close to the speed of light, and much more.
Fermi gave scientists a chance to study subatomic particles at energies that are much greater than those in ground-based particle accelerators, particularly energies that are greater than one billion electron volts (GeV). Being able to study this phenomenon was no small feat. NASA teamed up with the U.S. Department of Energy and institutions in France, Germany, Japan, Italy, and Sweden to build the spacecraft.
After more than a decade in orbit, Fermi has provided the deepest and best-resolved portrait of the gamma-ray sky so far. Some of Fermi’s fantastic accomplishments include detecting erupting sun flares on the side of the Sun not visible to the spacecraft in 2012, the 2013 gamma-ray burst of a dying star, and the detection of supernova remnants in nebulae like the Jellyfish Nebula. Fermi currently studies the central region of the Milky Way and works to unravel the mysteries as to why this area is brighter in gamma rays than expected.
Launch Date: Dec. 19, 2013
Launch Site: Ensemble de Lancement Soyouz in French Guiana
Gaia shot forth into the sky on December 19, 2013 as part of an ambitious mission by the ESA to chart a three-dimensional map of the Milky Way Galaxy. The technology Gaia possesses will provide unprecedented positional and radial velocity measurements with accuracies needed to create a census of about one billion stars in our Galaxy; this is, by the way, only about one percent of the Galactic stellar population!
Though Gaia is still young when compared to the other space telescopes on this list, it has done much in contributing to the understanding of our Galaxy. Along with Hubble, Gaia has been able to accurately weigh the Milky Way, showing it’s mind-boggling weight at about 1.5 trillion solar masses within a radius of 129,000 light-years from the Galaxy’s center. This star surveyor has also spurred hundreds of scientific studies due to the data collected on the formation and evolution of stars within our Galaxy and beyond.
NEOWISE (Formerly Wide-field Infrared Survey Explorer)
Launch Date: Dec. 14, 2009
Launch Site: Vandenberg Air Force Base, California
NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission has been in orbit for nearly five years. In that five years since its launch from Vandenberg Air Force Base, it has significantly added to scientists’ knowledge of asteroids and comets within our solar system. NEOWISE has also expanded understanding of other stars and galaxies as well. Its studies are conducted by looking at infrared wavelengths, and during its time in space, NEOWISE has surpassed 95 billion recorded measurements, and it did all this while being a recycled spacecraft!
Originally, NEOWISE was known as WISE, or the Wide-field Infrared Survey Explorer, which was launched in December 2009 and dedicated to studying galaxies, stars, and solar systems by imaging the infrared light through the entire sky. In 2011, WISE was placed in hibernation after completing its primary astrophysics mission. That wasn’t the end for this successful space telescope, however. In September of 2013, WISE was reactivated and renamed NEOWISE so it could continue contributing high-quality data to IPAC at Caltech in Pasadena, California.
Since it’s reactivation, NEOWISE has scanned the entire sky nearly eight times and observed/characterized 29,375 objects, including 788 near-Earth objects and 136 comets. NEOWISE even detected an asteroid on April 23, 2014 whose size was estimated to be between 800 and 1,300 feet. NEOWISE has helped scientists detect countless large Near-Earth Objects that have passed by Earth and aided in detecting the size of these objects. With nearly 2.5 million infrared images of the sky collected in its four full years, NEOWISE has given much back to the studies of the Universe and shows no signs of stopping.