SPHEREx (MIDEX 9, Explorer 102)

SPHEREx (MIDEX 9) [JPL]

SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) is an all-sky infrared spectral survey explorer satellite developed under NASA's MIDEX (Medium Explorer) program. SPHEREx is a partnership between California Institute of Technology (Caltech), JPL, Ball Aerospace, and the Korea Astronomy and Space Science Institute.

SPHEREx adresses all three science goals in NASA's astrophysics division, with a single instrument, a wide-field spectral imager:

• Mapping the large scale structures if galaxies to study the process of inflation in the early universe, adressing the objective to probe the origin and destiny of the universe.
• Measuring the total light production from stars and galaxies across cosmic history adressing the objective to explore the origin and evolution of galaxies.
• Determining how interstellar ices bring water and organics into proto-planetary systems furthering the objective to explore, whether planets around other stars could harbor life.

SPHEREx will create spectra (0.75 – 4.2 µm at R = 40, and 4.2 – 5 µm at R = 135) with high sensitivity using a cooled telescope with a wide field-of-view for large mapping speed. During its two-year mission, SPHEREx will produce four complete all-sky maps that will serve as a rich archive for the astronomy community. It will perform an all-sky survey to measure the near-infrared spectra of approximately 450 million galaxies.

SPHEREx implements a simple and robust design that maximizes spectral throughput and efficiency. SPHEREx achieves this with no moving parts except for one-time deployments of a sunshield and aperture cover. Design features have been proven effective on previous missions, and include:

• 20 cm all-aluminum telescope with a wide 3.5° × 11° field of view, imaged onto six 2K × 2K HgCdTe detector arrays. These H2RG arrays have been qualified for space observations by the James Webb Space Telescope, and are built on a long successful history of space instruments using arrays in smaller formats.
• Six space-demonstrated linear varable filters (LVFs) to produce spectra. The spectrum of each source is obtained by moving the telescope in the dispersion direction of the LVF in discrete steps. This method was demonstrated by LEISA on New Horizons to obtain excellent spectral images of Jupiter and Pluto.
• A telescope that is radiatively cooled to 80 K and three detectors that are cooled to 55 K with 660 % total margin on the net heat load. The thermal methods employed on SPHEREx have been previously demonstrated by Planck, Spitzer, and WISE.