SPHEREx will launch no earlier than February 2025, and carry out its survey observations for about two years, ending normal flight operations in spring 2027. SPHEREx is therefore well-timed to follow up on the results from missions such as JWST, TESS, and eROSITA, to identify targets for more detailed study by JWST, SOFIA, or ALMA, and to set the stage for later missions such as the Nancy Grace Roman Space Telescpope and PLATO. The figure below illustrates how SPHEREx will overlap with numerous other missions. Most of those shown are either unbiased or targeted surveys. The synergies of SPHEREx with these many other observatories, which were first discussed at the 2016 SPHEREx community workshop in Pasadena, were developed in detail during the 2nd SPHEREx community workshop in Cambridge in 2018. For details, see Doré et al., 2018.
The chart above shows the capabilities of different missions (including SPHEREx) in terms of wavelength coverage and spectral resolving power. Note that this chart was generated in 2018 and included the best estimate of the launch dates then. SPHEREx provides almost unique access with significant spectral resolution to the wavelength range between 2.5 and 5 µm, while also extending to shorter wavelengths to overlap with numerous ground-based and space-based imaging and spectroscopic surveys. The synergy between SPHEREx and JWST is particularly strong, because JWST is the only space-based mission with comparable wavelength grasp and spectral resolution: SPHEREx goes wide while JWST goes deep. Not shown here are the 10-30-meter class telescopes currently operating on the ground and planned for the future. Their overlap with SPHEREx will be similar to that of JWST, with the additional consideration that they will not have full access even to the 2.5-to-5 µm wavelength region because of atmospheric absorption. Nevertheless, we anticipate that these telescopes, with their much higher spectral and spatial resolution, will be effectively used in following up targets and scientific questions identified by SPHEREx.