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 April 2020, SPHEREx is targeted to launch in early 2024.[2] The Principal Investigator is James Bock at Caltech in Pasadena, California.

SPHEREx
Artist's concept of SPHEREx
Mission typeNear-infrared telescope
OperatorNASA
Websitespherex.caltech.edu
Mission duration25 months (proposed)
Spacecraft properties
Payload mass69 kg (152 lb)[1]
Start of mission
Launch dateQ1 2024[2]
Main telescope
Diameter20 cm[1]
WavelengthsNear-infrared
Transponders
BandS band, Ka band[1]
Instruments
spectrophotometer
Explorers program
 

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][1]

SPHEREx will complement planned Euclid and WFIRST spectroscopic surveys, but SPHEREx's lower redshift survey allows its measurement of inflationary parameters to be mostly independent to provide a new line of evidence.[1][6]

The telescope lens will have a diameter of 20 centimeters with a wide 3.5° x 7° field of view, imaged onto four 2k x 2k mercury cadmium telluride (HgCdTe) photodetector arrays.[1]

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).[8][9] 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 FINESSE.[5] Each team received $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 early 2024.[2] Medium-Class Explorer mission costs are capped at $250 million, not including the launch vehicle.[5] As of April 2020, the preliminary total cost of the mission is approximately $395 million to $427 million.[2]

References
  1. Proposed Astrophysics Mission to Conduct the First Infrared Spectral Survey of the Entire Sky. 27 August 2017.
  2. "GAO-20-405, NASA: Assessments of Major Projects" (PDF). GAO. 29 April 2020. p. 45. Retrieved 30 April 2020.
  3. "SPHEREx". NASA. 18 February 2019. Retrieved 19 February 2019.
  4. Cofield, Calla; Cole, Steve (13 February 2019). "NASA Selects New Mission to Explore Origins of Universe". NASA. Retrieved 13 February 2019.
  5. NASA Selects Proposals to Study Galaxies, Stars, Planets. Katherine Brown, NASA News. 9 August 2017.
  6. SPHEREx Science. Caltech. 2018.
  7. Missions to probe exoplanets, galaxies, and cosmic inflation vie for $250 million NASA slot. Daniel Clery, Science Magazine, 16 August 2017.
  8. SPHEREx News. SPHEREx, Caltech.
  9. NASA Selects Proposals to Study Neutron Stars, Black Holes and More. Karen Northon, NASA News. 30 July 2015.

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