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Astrophysics Explorers

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The overall Explorer program is managed by the Heliophysics Division. Small- and medium-class, PI-led Astrophysics missions, as well as Astrophysics missions of opportunity, are selected under the Explorer program, and are managed by the Astrophysics Division. Explorers are opportunities for focused scientific investigations, and fill the scientific gaps between the larger missions. For example, the Nuclear Spectroscopic Telescope Array (NuSTAR) is conducting a census of black holes for the Physics of the Cosmos program and studying the birth of elements for the Cosmic Origins program. In April 2013, the Transiting Exoplanet Survey Satellite (TESS) was selected to move into formulation. TESS will identify terrestrial planets in the habitable zones of nearby stars. The Neutron Star Interior Composition Explorer (NICER) Mission of Opportunity was also selected in April 2013. It will be mounted on the space station and measure the variability of cosmic X-ray sources to explore the exotic states of matter within neutron stars and reveal their interior and surface compositions.

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DivisionNameLaunch DatePhase
Astrophysics FUSE
Far Ultraviolet Spectroscopic Explorer (FUSE) studied the far ultraviolet portion of the electromagnetic spectrum from high orbit. This range provided an opportunity to answer important questions about many types of astrophysical objects, such as the nuclear regions of active galaxies ...
19990624 June 24, 1999 4Past
Astrophysics GALEX
GALEX explored the origin and evolution of galaxies and the origins of stars and heavy elements. It also conducted an all-sky ultraviolet survey.
20030428 April 28, 2003 4Past
Astrophysics GEMS
GEMS was not confirmed to move into development. GEMS would have used an X-ray telescope to measure the polarization of the X-rays coming from the vicinity of compact objects in the universe.
Astrophysics HETE-1
The prime objective of the HETE spacecraft was to carry out the first multiwavelength study of gamma-ray bursts with Ultraviolet, X-ray and gamma ray instruments. A unique feature of the mission was its capability to localize bursts with several arc-second ...
19961104 November 04, 1996 4Past
Astrophysics HETE-2
HETE-2 was a small scientific satellite designed to detect and localize gamma-ray bursts.
20001009 October 09, 2000 4Past
Astrophysics Hitomi (ASTRO-H)
Hitomi is a powerful orbiting observatory developed by the Japan Aerospace Exploration Agency (JAXA) for studying extremely energetic processes in the universe.
20160217 February 17, 2016 3Operating
Astrophysics NICER
The Neutron star Interior Composition ExploreR (NICER) is a NASA Astrophysics Explorer Mission of Opportunity dedicated to the study of the extraordinary gravitational, electromagnetic, and nuclear-physics environments embodied by neutron stars.
20170201 February 2017 2Development
Astrophysics NuSTAR
The Nuclear Spectroscopic Telescope Array is a pathfinder mission that will open the high energy X-ray sky for sensitive study for the first time. This mission is part of SMD's Astrophysics Explorers program.
20120613 June 13, 2012 3Operating
Astrophysics RXTE
Rossi X-ray Timing Explorer studied variability over time in the emission of X-ray sources, with moderate spectral resolution. This time behavior is a source of important information about processes and structures in white-dwarf stars, X-ray binaries, neutron stars, pulsars and ...
19951230 December 30, 1995 4Past
Astrophysics Suzaku (Astro-E2)
Suzaku (formerly Astro-E2) provides powerful tools to use the Universe as a laboratory for unraveling complex, high-energy processes and the behavior of matter under extreme conditions. This mission is part of SMD's Astrophysics Explorers program. This mission was awarded via ...
20050710 July 10, 2005 4Past
Astrophysics SWAS
The Submillimeter Wave Astronomy Satellite (SWAS) instrument was a submillimeter wave telescope that incorporated dual heterodyne radiometers and an acousto-optical spectrometer to investigate the composition of dense interstellar clouds.
19981206 December 06, 1998 4Past
Astrophysics Swift
Swift Gamma Ray Burst Explorer is a three-telescope space observatory for studying the position, brightness, and physical properties of gamma ray bursts. Although gamma ray bursts are the largest known explosions in the Universe, outshining the rest of the Universe ...
20041120 November 20, 2004 3Operating
Astrophysics TESS
The Transiting Exoplanet Survey Satellite (TESS) will use an array of telescopes to perform an all-sky survey to discover transiting exoplanets ranging from Earth-sized to gas giants, in orbit around nearby bright stars.
20180601 June 2018 2Development
Astrophysics WISE
WISE spent over a year imaging the entire sky in the infrared. The NEOWISE Survey surveyed small bodies, asteroids, and comets in our solar system.
20091214 December 14, 2009 4Past
Astrophysics WMAP
WMAP addressed fundamental questions in cosmology: What is the geometry of the Universe? How did structures, such as galaxies and galaxy clusters, that we see in today’s sky come about? How old is the Universe, and what are its constituents?
20010630 June 30, 2001 4Past