SPHEREx

SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer)[3] is a future near-infrared space observatory that will perform an all-sky survey to measure the near-infrared spectra of approximately 450 million galaxies. In February 2019, SPHEREx was selected by NASA for its next Medium-Class Explorers mission, beating out two competing mission concepts: Arcus and FINESSE.[4][5] As of January 2021, SPHEREx is targeted to launch no earlier than June 2024 on a Falcon 9 rocket from Vandenberg Air Force Base.[2][1] The principal investigator is James Bock at Caltech in Pasadena, California.

SPHEREx
Artist's concept of SPHEREx
Mission typeNear-infrared telescope
OperatorNASA
Websitehttp://spherex.caltech.edu/
Mission duration25 months (planned)
Spacecraft properties
Payload mass69 kg
Start of mission
Launch date17 June 2024[1]
RocketFalcon 9[2]
Launch siteVandenberg Air Force Base, California[2]
ContractorSpaceX
Main telescope
Diameter20 cm
WavelengthsNear-infrared
Transponders
BandS-band, Ka-band
Instruments
Spectrophotometer
 

Overview

SPHEREx will use a spectrophotometer to perform an all-sky survey that will measure near-infrared spectra from 0.75 to 5.0 micrometers. It will employ a single instrument with a single observing mode and no moving parts to map the entire sky four times during its nominal 25-month mission; the crucial technology is a linear variable filter.[6] It will classify galaxies according to redshift accuracy, categorizing approximately 450 million galaxies and fitting measured spectra to a library of galaxy templates. Specifically, SPHEREx will probe signals from the intra-halo light and from the epoch of reionization.[6] It would explore what drove the early universe inflation, explore the origin and history of galaxies, and explore the origin of water in planetary systems.[6][7][8]

SPHEREx will complement planned Euclid and Nancy Grace Roman Space Telescope spectroscopic surveys. High precision redshift information of foreground galaxies provided by SPHEREx in correspondence with weak gravitational lensing measurements of background galaxies from Euclid and Nancy Grace Roman Space Telescope will allow a for a direct measurement of the dark matter distribution surrounding the foreground galaxies.[9] Although, the SPHEREx low redshift survey allows its measurement of inflationary parameters to be mostly independent to provide a new line of evidence.[8][6]

The telescope lens will have a diameter of 20 centimeters with a 3.5° x 11° field of view and six 2k x 2k mercury cadmium telluride (HgCdTe) photodetector arrays.[10]

History

The SPHEREx proposal was submitted to NASA on 19 December 2014, and it was selected for further conceptual development (Phase A) on 30 July 2015 for the Small Explorer program (SMEX).[11][12] The detailed concept study report was submitted to NASA on 19 July 2016, but it was not selected for SMEX. An enhanced version of SPHEREx was submitted on 15 December 2016 as a Medium-Class Explorer (MIDEX), and it was selected as a finalist in August 2017, along two other competing missions: Arcus, and Fast Infrared Exoplanet Spectroscopy Survey Explorer (FINESSE).[5] Each team received US$2 million to refine their mission concepts over nine-months.[5] SPHEREx was selected as the winner in February 2019, and the mission has been given the green light to proceed with construction and launch.[4] The launch is currently targeted for June 2024.[1] Medium-Class Explorer mission costs are capped at US$250 million, not including the launch vehicle.[5] As of April 2020, the preliminary total cost of the mission is approximately US$395 million to US$427 million.[13] In January 2021, NASA announced that the mission has entered Phase C, which means that the early design plans have been approved and teams can begin the final design and assemble hardware and software; and that launch is expected between June 2024 and April 2025.[14] On 4 February 2021, NASA announced they had selected the SpaceX Falcon 9 to launch the spacecraft, and total cost of the launch would be US$98.8 million.[2]

References
  1. "SMSR Integrated Master Schedule" (PDF). Office of Safety and Mission Assurance. NASA. 3 September 2020. Retrieved 7 September 2020.
  2. Potter, Sean (4 February 2021). "NASA Awards Launch Services Contract for SPHEREx Astrophysics Mission". NASA. Retrieved 4 February 2021.
  3. "SPHEREx". NASA. 18 February 2019. Retrieved 19 February 2019. This article incorporates text from this source, which is in the public domain.
  4. Cofield, Calla; Cole, Steve (13 February 2019). "NASA Selects New Mission to Explore Origins of Universe". NASA. Retrieved 13 February 2019. This article incorporates text from this source, which is in the public domain.
  5. Katherine Brown (9 August 2017). "NASA Selects Proposals to Study Galaxies, Stars, Planets". NASA News. This article incorporates text from this source, which is in the public domain.
  6. "SPHEREx Science". Caltech. 2018. This article incorporates text from this source, which is in the public domain.
  7. Missions to probe exoplanets, galaxies, and cosmic inflation vie for $250 million NASA slot. Daniel Clery, Science Magazine, 16 August 2017
  8. Proposed Astrophysics Mission to Conduct the First Infrared Spectral Survey of the Entire Sky 27 August 2017
  9. Doré, Olivier; Bock, Jamie; Ashby, Matthew; Capak, Peter; Cooray, Asantha; de Putter, Roland; Eifler, Tim; Flagey, Nicolas; Gong, Yan; Habib, Salman; Heitmann, Katrin (25 March 2015). "Cosmology with the SPHEREX All-Sky Spectral Survey". arXiv:1412.4872 [astro-ph.CO].
  10. "SPHEREx Official Website". spherex.caltech.edu. Retrieved 6 October 2020.
  11. SPHEREx News. SPHEREx, Caltech. This article incorporates text from this source, which is in the public domain.
  12. Karen Northon (30 July 2015). "NASA Selects Proposals to Study Neutron Stars, Black Holes and More". NASA News. This article incorporates text from this source, which is in the public domain.
  13. "GAO-20-405, NASA: Assessments of Major Projects" (PDF). GAO. 29 April 2020. p. 45. Retrieved 30 April 2020. This article incorporates text from this source, which is in the public domain.
  14. https://www.cnn.com/2021/01/07/world/nasa-spherex-telescope-scn-trnd/index.html
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