Gravity and Extreme Magnetism Small Explorer (GEMS or SMEX-13) mission was a

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

space observatory mission. The main scientific goal of GEMS was to be the first mission to systematically measure the

polarization Polarization or polarisation may refer to: Mathematics *Polarization of an Abelian variety, in the mathematics of complex manifolds *Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by ...

of X-ray sources. GEMS would have provided data to help scientists study the shape of

spacetime In physics, spacetime, also called the space-time continuum, is a mathematical model that fuses the three dimensions of space and the one dimension of time into a single four-dimensional continuum. Spacetime diagrams are useful in visualiz ...

that has been distorted by a spinning

black hole A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...

's gravity and the structure and effects of the

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

s around

neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...

s. It was cancelled by NASA in June 2012 for potential cost overruns due to delays in developing the technology and never moved into the development phase. GEMS was managed by the NASA

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...

(GSFC). The project was an

astrophysics Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the ...

program reporting to NASA's

Science Mission Directorate The Science Mission Directorate (SMD) of the National Aeronautics and Space Administration (NASA) is one of the six directorates that constitute NASA. Its responsibility is to define and direct research into scientific questions of interest, shari ...

(SMD) in

Washington, D.C. Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...

Cancelled missions can be reinstated - for example,

NuSTAR NuSTAR (Nuclear Spectroscopic Telescope Array, also named Explorer 93 and SMEX-11) is a NASA space-based X-ray telescope that uses a conical approximation to a Wolter telescope to focus high energy X-rays from astrophysical sources, especial ...

was cancelled in 2006, but reinstated a year later and launched in June 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. Small missions of the Explorer program offer much flexibility and launch opportunities, and the lessons learned can be applied to the same missions goals, but on a different mission (compare, for instance,

Vanguard 1 Vanguard 1 (Harvard designation: 1958-Beta 2, COSPAR ID: 1958-002B ) is an American satellite that was the fourth artificial Earth-orbiting satellite to be successfully launched, following Sputnik 1 Sputnik 1 (, , ''Satellite 1''), ...

Explorer 1 Explorer 1 was the first satellite launched by the United States in 1958 and was part of the U.S. participation in the International Geophysical Year (IGY). The mission followed the first two satellites, both launched by the Soviet Union duri ...

). Several years later two new X-ray polarimetry missions won a NASA award to develop X-ray polarimetry missions. NASA's

IXPE Imaging X-ray Polarimetry Explorer, commonly known as IXPE or SMEX-14, is a space observatory with three identical telescopes designed to measure the polarization of cosmic X-rays of black holes, neutron stars, and pulsars. The observatory, ...

X-ray polarimetry telescope was launched in 2021; its X-ray observational capabilities and mission objectives are very similar to those (proposed) of the GEMS.

Launch

The spacecraft would have been launched in July 2014 on a nine-month mission with a possible 15-month extension for a guest observer phase; but the mission was terminated at the Confirmation Review stage on 10 May 2012 due to expected cost overruns.

Mission

The GEMS

X-ray telescope An X-ray telescope (XRT) is a telescope that is designed to observe remote objects in the X-ray spectrum. X-rays are absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets ...

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 would have also probed the structure and effects of the

s around

magnetar A magnetar is a type of neutron star with an extremely powerful magnetic field (~109 to 1011 T, ~1013 to 1015 G). The magnetic-field decay powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays.Ward; Br ...

s and other star remnants with magnetic fields trillions of times stronger than Earth's. GEMS could reveal: * How spinning black holes affect space-time and matter as it is drawn in and compressed by strong gravitational fields * What happens in the very 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 Angular resolution describes the ability of any image-forming device such as an Optical telescope, optical or radio telescope, a microscope, a camera, or an Human eye, eye, to distinguish small details of an object, thereby making it a major det ...

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 The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

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 was to employ a time projection chamber to image the track. The GEMS instrument was planned to be about 100 times more sensitive than previous X-ray polarization experiments.

Cancellation

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 US$150 million, leading to cancellation of the mission. The cancellation of GEMS marked 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

James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope designed to conduct infrared astronomy. As the largest telescope in space, it is equipped with high-resolution and high-sensitivity instruments, allowing it to view objects too old, Lis ...

(JWST). The cancellation of GEMS may have jeopardized the

Pegasus XL Pegasus is an air-launched multistage rocket developed by Orbital Sciences Corporation (OSC) and later built and launched by Northrop Grumman. Pegasus is the world's first privately developed orbital launch vehicle. Capable of carrying smal ...

launcher. (The Pegasus XL has successfully launched other small explorer missions)

Project status

GEMS was one of six Small Explorer missions selected in May 2008 for the

Small Explorer (SMEX) Program Phase A study. In June 2009, GEMS was chosen to be the second of these missions to go forward into Phase B, starting in October 2010 for a launch in April 2014. The project completed and successfully passed the Systems Requirements Review (SRR) in December 2010. GEMS did not pass a confirmation review conducted on 10 May 2012, which effectively cancelled the project. The project team intended to appeal the cancellation. On 7 June 2012, NASA officially announced the cancellation of the GEMS project. The mission was supposed to launch in July 2014 to study black holes and neutron stars, but external reviews found the project would likely exceed its budget. GEMS was supposed to hold at US$119 million, not counting the launch vehicle. NASA's astrophysics director,

Paul Hertz Paul may refer to: People * Paul (given name), a given name, including a list of people * Paul (surname), a list of people * Paul the Apostle, an apostle who wrote many of the books of the New Testament * Ray Hildebrand, half of the singing duo P ...

, says the technology needed for the instrument took longer to develop than expected, and that drove up the price. NASA continued studying X-ray polarimetry missions in 2015 for future Explorer program observatories.

Project and Science Team

The GEMS principal investigator was Dr Jean H. Swank, of NASA's

Greenbelt, Maryland Greenbelt is a city in Prince George's County, Maryland, United States, and a suburb of Washington, D.C. At the 2020 United States census, 2020 census, the population was 24,921. Greenbelt is the first and the largest of the three experimental ...

Project Team

* GSFC was responsible for the GEMS instrument, system engineering, spacecraft contract, and the overall program management. *

Ames Research Center The Ames Research Center (ARC), also known as NASA Ames, is a major NASA research center at Moffett Federal Airfield in California's Silicon Valley. It was founded in 1939 as the second National Advisory Committee for Aeronautics (NACA) laborat ...

would have provided co-investigators and performed the Education and Public Outreach (EPO) support. * The satellite would have been built by

Orbital Sciences Corporation Orbital Sciences Corporation (commonly referred to as Orbital) was an American company specializing in the design, manufacture, and launch of small- and medium- class space and launch vehicle systems for commercial, military and other governmen ...

using its LEOStar-2

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are less customized than specially-produced satelli ...

design, and would also conduct mission operations, under a

US$ The United States dollar (Currency symbol, symbol: Dollar sign, $; ISO 4217, currency code: USD) is the official currency of the United States and International use of the U.S. dollar, several other countries. The Coinage Act of 1792 introdu ...

40 million contract. *

Alliant Techsystems Alliant Techsystems Inc. (ATK) was an American Aerospace manufacturer, aerospace and arms industry, arms manufacturer headquartered in Arlington County, Virginia. The company operated across 22 states, Puerto Rico, and internationally. ATK reven ...

(ATK) would build a deployable boom to place the X-ray mirrors at the proper distance from the detectors or polarimeters. *

University of Iowa The University of Iowa (U of I, UIowa, or Iowa) is a public university, public research university in Iowa City, Iowa, United States. Founded in 1847, it is the oldest and largest university in the state. The University of Iowa is organized int ...

would have provided instrument calibration assistance and would have had students prepare a small instrument that could be part of the mission.

Science Team

Co-investigators

NASA Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...

NASA Ames Research Center The Ames Research Center (ARC), also known as NASA Ames, is a major NASA research center at Moffett Federal Airfield in California's Silicon Valley. It was founded in 1939 as the second National Advisory Committee for Aeronautics (NACA) laborat ...

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...

(MIT)

Science collaborators

Other GEMS collaborators are from universities include: GEMS home page, accessed 2009-08-14 *

Johns Hopkins University The Johns Hopkins University (often abbreviated as Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland, United States. Founded in 1876 based on the European research institution model, J ...

Cornell University Cornell University is a Private university, private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson W ...

Rice University William Marsh Rice University, commonly referred to as Rice University, is a Private university, private research university in Houston, Houston, Texas, United States. Established in 1912, the university spans 300 acres. Rice University comp ...

University of Oulu The University of Oulu () is one of the largest universities in Finland, located in the city of Oulu. It was founded on July 8, 1958. The university has around 14,200 students and 3,800 staff. 21 International Master's Programmes are offer ...

(

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

) *

North Carolina State University North Carolina State University (NC State, North Carolina State, NC State University, or NCSU) is a public university, public Land-grant university, land-grant research university in Raleigh, North Carolina, United States. Founded in 1887 and p ...

Washington University in St. Louis Washington University in St. Louis (WashU) is a private research university in St. Louis, Missouri, United States. Founded in 1853 by a group of civic leaders and named for George Washington, the university spans 355 acres across its Danforth ...

References

External links

NASA Project Homepage

NASA Science Homepage

GEMS Homepage at Orbital Sciences

{{Space observatories NASA programs Explorers Program Space telescopes X-ray telescopes Proposed NASA space probes