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The Gravity and Extreme Magnetism SMEX (GEMS) mission was a cancelled space observatory mission. The main scientific goal of GEMS was to be the first mission to systematically measure the polarization of cosmic X-Ray sources. GEMS would have provided data to help scientists study the shape of space that has been distorted by a spinning black hole's gravity and the structure and effects of the magnetic fields around Neutron stars. It was cancelled by NASA in June 2012 for potential cost overruns due to delays in developing the technology. GEMS was managed by the National Aeronautics and Space Administration NASA, the United States space agency, at the Goddard Space Flight Center. The project was an astrophysics program reporting to NASA's Science Mission Directorate (SMD) in Washington, D.C.. The spacecraft would have been launched on in July 2014 on a nine-month mission with a possible 15 month extension for a guest observer phase;〔(GEMS ), Smithsonian Astrophysical Observatory, accessed 2011-05-23〕 but the mission was terminated at the Confirmation Review stage on May 10, 2012 due to expected cost overruns. Cancelled missions can be reinstated for example NuSTAR was cancelled in 2006, but reinstated a year later and launched in June 2012.〔(W. Graham - Orbital’s Pegasus successfully launches NASA’s NuSTAR spacecraft (June 13th, 2012) )〕 However, NuSTAR was not cancelled due to project overruns, but rather due to changes in the overall NASA budget, so the circumstances for cancellation were very different. Of course small missions of the Explorer program offer a lot of flexibility and launch opportunities, and the lessons learned can be applied to the same missions goals, but on a different mission (Compare Vanguard 1 to Explorer 1) Just a couple years later two new X-ray polarimetry mission won a NASA award to develop a X-ray polarimetry missions.〔(NASA Selects Proposals to Study Neutron Stars, Black Holes and More )〕 ==Mission== The GEMS X-ray telescope was designed to indirectly measure the regions of distorted space around spinning black holes through a measurement of the polarization of X-rays emitted. It will thereby probe the structure and effects of the magnetic field around magnetars and dead stars with magnetic fields trillions of times stronger than Earth's. GEMS could reveal: * How spinning black holes affect space-time and matter as they are drawn in and compressed by strong gravitational fields. * What happens in the super strong magnetic fields near pulsars and magnetars. * How cosmic rays are accelerated by shocks in supernova remnants. Current missions cannot do this because the required angular resolution is limited and magnetic fields are invisible. The detector in GEMS would have been a small chamber filled with gas. When an X-ray is absorbed in the gas, an electron carries off most of the energy, and starts out in a direction related to the polarization direction of the X-ray. This electron loses energy by ionizing the gas; the instrument measures the direction of the ionization track, and thereby the polarization of the X-ray. The GEMS detector readout will employ a time projection chamber to image the track. The GEMS instrument is about 100 times more sensitive than previous X-ray polarization experiments. Mission costs were capped at US$105 million (in Fiscal Year 2008 dollars), excluding the launch vehicle,〔 but an independent confirmation review board at NASA claimed it would grow to an estimated $150 million, leading to cancellation of the mission. The cancellation of GEMS marks the end of a multi-year-long binge of cancellations and attempted cancellations of current and future missions: it was at the time the last funded future U.S. space telescope besides JWST. The cancellation of GEMS may have jeopardized the Pegasus XL launcher.〔(D. Leone - Demise of GEMS May Cost Orbital 150 Jobs, Doom Pegasus (2012) - Space News )〕 (The Pegasus XL has successfully launched other small explorer missions) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gravity and Extreme Magnetism」の詳細全文を読む スポンサード リンク
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