We now continue our review of NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission, which launched June 13th. In this outing, we learn about the progression of people, events and observatories that caused NuSTAR to be...
Uhuru and Einstein
NuSTAR continues a strong tradition of spaceborne X-ray astronomy that dates back 60 years. Starting in the late 1950s, early experiments were performed on short-duration rocket payloads. The first orbiting X-ray satellite was Uhuru, launched in December 1970.
(Learn more about Uhuru at heasarc.gsfc.nasa.gov/docs/uhuru/uhuru.html and nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1970-107A)
And the first fully imaging X-ray satellite was the Einstein Observatory, also known as HEAO-2, launched in November 1978.
(Learn more about the Einstein Observatory at heasarc.gsfc.nasa.gov/docs/einstein/heao2.html and nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1978-103A)
The work of these two satellites led Riccardo Giacconi, an Italian-American astrophysicist, to win the Nobel Prize in Physics in 2002 for “for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources.”
Why do we need another X-ray satellite? NuSTAR, for the first time, brings the telescope technologies employed by Einstein and its successors for low-energy X-rays into the higher-energy X-ray band. This radical shift in technology provides NuSTAR with vast improvements in both resolution and sensitivity. NuSTAR will be a pathfinder, opening a new window on the high-energy X-ray universe.
Predecessors and Contemporaries
Several X-ray missions currently in operation or nearing launch are described below.
NASA’s Chandra X-ray Observatory is the third of NASA’s family of four Great Observatories, a group that includes the Hubble Space Telescope, the Spitzer Space Telescope, and the Compton Gamma-Ray Observatory. Chandra, which launched from the Space Shuttle Columbia in July 1999, works in the low-energy X-ray regime (0.1 to 10 kilo electron volts or keV). NuSTAR extends similar grazing-incidence X-ray technology employed by Chandra to higher energies. NuSTAR has several approved observing programs planned in coordination with Chandra, including monitoring of the supermassive black hole that resides at the center of the Milky Way galaxy.
(Learn more about Chandra at chandra.harvard.edu and www.nasa.gov/Chandra and nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1999-040B)
XMM-Newton (European Space Agency), also known as the X-ray Multi-mirror Mission, is Europe’s flagship counterpart to Chandra. XMM-Newton, which launched in December 1999, also employs grazing-incidence X-ray optics in the low-energy X-ray regime (0.1 to 15 keV). NuSTAR has several approved programs planned in coordination with XMM-Newton, including observations of extremely luminous supermassive black holes, which will measure the rate at which the black holes are spinning. Working together, NuSTAR and XMM-Newton will make significantly more precise measurements than possible by either facility individually.
(Learn more about XMM Newton at xmm.esac.esa.int and science.nasa.gov/missions/xmm-newton and heasarc.gsfc.nasa.gov/docs/xmm/xmmgof.html and nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1999-066A)
INTEGRAL (European Space Agency), the INTErnational Gamma-Ray Astrophysics Laboratory, launched in October 2002. This telescope contains a suite of instruments designed to study the high-energy sky, both with X-rays and with even higher-energy gamma-rays. The instrument that has the most overlap with NuSTAR, called the Imager on-Board the INTEGRAL Satellite or IBIS, observes large swaths of the sky from 15 keV to 10 mega electron volts (MeV). Unlike IBIS, NuSTAR will focus the X-ray light, giving it better resolution and sensitivity for observing smaller patches of sky.
(Learn more about INTEGRAL at www.esa.int/SPECIALS/Integral and sci.esa.int/science-e/www/area/index.cfm?fareaid=21 and heasarc.gsfc.nasa.gov/docs/integral/inthp_about.html and nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=2002-048A)
NASA's Swift Gamma-Ray Burst Mission launched in November 2004 as part of NASA’s Medium Explorer program. Swift’s primary science objective is to study “gamma-ray bursts,” employing three science instruments for rapid follow-up of these tremendous cosmic explosions at ultraviolet, optical and X-ray energies. The Burst Alert Telescope (BAT) instrument monitors 25 percent of the sky instantaneously at a time in the high-energy X-ray band (15 to 150 keV), looking for new, extremely energetic events. This instrument is designed to see large portions of the sky at low resolution. It signals the telescope to autonomously slew to the cosmic events, and follow-up with its other instruments in more detail, including a lower-energy X-ray instrument. This information is then automatically conveyed to the science community who then deploy ground-based facilities to study and understand the cosmic explosions before they fade away. NuSTAR will work in a similar energy band to Swift’s BAT instrument, but focuses the X-ray light, giving it much improved resolution and sensitivity.
The NuSTAR team plans several observations in coordination with Swift, including a survey of bright galaxies radiating high-energy X-rays and gamma-rays. The telescopes will complement each other, improving our understanding of the physics and demographics of supermassive black holes. Because the high-energy emission from these galaxies varies, simultaneous coverage is essential, requiring careful coordination between the science and mission operation teams.
(Learn more about Swift at www.swift.psu.edu and www.nasa.gov/mission_pages/swift/main)
Suzaku (Japan), formerly Astro-E2, was launched in July 2005, replacing the Astro-E mission that was unfortunately lost during launch in February 2000. Suzaku includes focusing, grazing-incidence optics that work in the low-energy X-ray regime (0.2 to 12 keV), as well as non-focusing X-ray technologies that work at higher energies (10 to 600 keV). This broad energy capability complements NuSTAR. There are plans for several joint calibration and science campaigns between NuSTAR and Suzaku.
(Learn more about Suzaku at www.astro.isas.jaxa.jp/suzaku/index.html.en and www.nasa.gov/mission_pages/astro-e2)
NASA’s Fermi Gamma-Ray Space Telescope, launched in June 2008, is a joint venture primarily between NASA and the United States Department of Energy. Fermi works at higher energies than NuSTAR, reaching the MeV and GeV range, and scans the sky about 16 times a day for the variable objects that dominate the cosmos at these extreme energies, such as supermassive black holes with jets pointing toward Earth. One of the key NuSTAR science objectives is to coordinate observations with Fermi, studying the jets spewing from black holes at close to the speed of light. Such observations, which will be done in coordination with ground-based facilities working in the radio, optical, infrared and tera electron volt (TeV) gamma-ray regime, will help astrophysicists understand the physics of particle acceleration in these extreme sources.
(Learn more about Fermi at fermi.gsfc.nasa.gov and nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=2008-029A)
Astro-H (Japan, with important NASA participation), JAXA’s successor X-ray mission to Suzaku, also known as the New X-ray Telescope (NeXT), is planned for launch in 2014. Astro-H has several instruments, including a low-energy X-ray calorimeter spectrometer and the second focusing high-energy X-ray optics after NuSTAR’s. Astro-H can perform low- and high-energy X-ray observations simultaneously; NuSTAR is able to perform similar science by working in coordination with Chandra, Suzaku, Swift, and/or XMM-Newton. The Astro-H high-energy imager works in a similar energy band as NuSTAR (5 to 80 keV) with a similar effective area. Astro-H expects to have typical angular resolution of 60 to 90 arcseconds (half-power diameter), slightly poorer than the current best estimate of 50 arcsecond performance expected for NuSTAR.
(Learn more about Astro-H at science.nasa.gov/missions/astro-h/ and heasarc.gsfc.nasa.gov/docs/astroh/ and astro-h.isas.jaxa.jp)
And now, the mission particulars...
NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley (UC Berkley); Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; and ATK Aerospace Systems, Goleta, California. NuSTAR will be operated by UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA. For more information on the NuSTAR mission, visit www.nasa.gov/nustar and http://www.nustar.caltech.edu/ .
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