.jpg) SPHEREx on a work stand, being prepared for launch | |
| Names | Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer |
|---|---|
| Mission type | Astrophysics |
| Operator | NASA |
| COSPAR ID | 2025-047E |
| SATCATno. | 63182 |
| Website | spherex |
| Mission duration | Planned: 25 months Elapsed: 8 months, 16 days |
| Spacecraft properties | |
| Manufacturer | BAE Systems Inc. (PreviouslyBall Aerospace & Technologies) |
| Launch mass | 178 kg (392 lb)[1] |
| Start of mission | |
| Launch date | 12 March 2025, 03:10:00 UTC (11 March 2025, 8:10 pm PDT)[2][3] |
| Rocket | Falcon 9 Block 5 |
| Launch site | Vandenberg,SLC-4E |
| Contractor | SpaceX |
| Orbital parameters | |
| Reference system | Geocentric orbit |
| Regime | Sun-synchronous,low Earth orbit |
| Altitude | 700 km (430 mi) |
| Inclination | 97° |
| Period | 90 minutes |
| Main telescope | |
| Diameter | 20 cm (7.9 in) |
| Wavelengths | Near-infrared |
| Transponders | |
| Band | S-band,Ka-band |
| Instruments | |
| Spectrophotometer | |
SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer)[4] is anear-infraredspace observatory that will perform anall-sky survey to measure thenear-infrared spectra of approximately 450 milliongalaxies. In February 2019, SPHEREx was selected byNASA for its nextMedium-Class Explorers mission, beating out two competing mission concepts:Arcus andFINESSE.[5][6] SPHEREx launched on 12 March 2025 on aFalcon 9 Block 5 rocket alongside thePUNCH microsatellites fromVandenberg Space Force Base.[2][3] The principal investigator is James Bock atCalifornia Institute of Technology (Caltech) inPasadena, California.
SPHEREx will use aspectrophotometer to perform an all-sky survey that will measurenear-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 (in 96 different color bands, far exceeding the color resolution of previous all-sky maps[5]) four times during its nominal 25-month mission; the crucial technology is alinear variable filter,[7] as demonstrated by LEISA onNew Horizons.[8]
It will classify galaxies according toredshift 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 theepoch of reionization.[7] It would explore what drove the early universeinflation, explore the origin and history of galaxies, and explore the origin ofwater in planetary systems.[7][9][10]
SPHEREx will complement theEuclid and plannedNancy Grace Roman Space Telescope spectroscopic surveys. High precision redshift information of foreground galaxies provided by SPHEREx in correspondence withweak gravitational lensing measurements of background galaxies from Euclid and Nancy Grace Roman Space Telescope will allow direct measurement of the dark matter distribution surrounding the foreground galaxies.[11] The SPHEREx lowredshift survey allows its measurement ofinflationary parameters to be mostly independent, thus providing a new line of evidence.[10][7]
The triple mirror telescope has an aperture diameter of 20 centimeters with a3.5° × 11° field of view and six2K × 2Kmercury cadmium telluride (HgCdTe)photodetector arrays.[12][8] Each2K × 2K focal-plane array is covered with a linear variable filter, providing narrow-band response with a band center that varies along one axis of the array. SPHEREx obtains spectra through multiple exposures, placing a given source at multiple positions in the field of view, where it is measured at multiple wavelengths by repointing the spacecraft.[8]
The SPHEREx spacecraft and telescope were provided byBAE Systems Inc. Space & Mission Systems division (previouslyBall Aerospace & Technologies) while the payload was developed by Caltech and NASA'sJet Propulsion Laboratory. TheKorea Astronomy and Space Science Institute supplied a non-flight cryogenic test chamber.[13][14][15]
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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 theSmall Explorer program (SMEX).[16][17] 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 aMedium-Class Explorer (MIDEX), and it was selected as a finalist in August 2017, along two other competing missions:Arcus, andFast Infrared Exoplanet Spectroscopy Survey Explorer (FINESSE).[6] Each team received US$2 million to refine their mission concepts over nine-months.[6]
SPHEREx was selected as the winner in February 2019, and the mission was approved to proceed with construction and launch.[5] Medium-Class Explorer mission costs are capped at US$250 million, not including the launch vehicle.[6] As of April 2020, the preliminary total cost of the mission is approximately US$395 million to US$427 million.[18] The 2020 estimates include the costs of the launch vehicle and NASA reserves that are not part of the cost cap.
On 7 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.[19] On 4 February 2021, NASA announced they had selected theSpaceXFalcon 9 to launch the spacecraft, and total cost of the launch would be US$98.8 million.[20] In August 2022 NASA announced that the 4 microsatellites of thePUNCH constellation would be launched as rideshare payloads together with SPHEREx.[21] The mission launched on 12 March 2025.[2]First light was on April 2025.[22] Regular science operation started on 1 May 2025.[23]
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