Artist's concept of SPHEREx
|Mission type||Near-infrared telescope|
|Mission duration||25 months (planned)|
|Payload mass||69 kg|
|Start of mission|
|Launch date||17 June 2024|
SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) 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. As of September 2020, SPHEREx is targeted to launch on 17 June 2024. The principal investigator is James Bock at Caltech in Pasadena, California.
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. 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. 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.
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. Although, the SPHEREx low redshift survey allows its measurement of inflationary parameters to be mostly independent to provide a new line of evidence.
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). 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). Each team received US$2 million to refine their mission concepts over nine-months. SPHEREx was selected as the winner in February 2019, and the mission has been given the green light to proceed with construction and launch. The launch is currently targeted for June 2024. Medium-Class Explorer mission costs are capped at US$250 million, not including the launch vehicle. As of April 2020, the preliminary total cost of the mission is approximately US$395 million to US$427 million.