The effects of a map of the sky are not usually instantaneous but they are lasting. Through the use of SPHEREx, NASA has now a repeating, calibrated infrared universe view that can be stacked, cross matched and mined over the years and has made “the sky” into a data set that becomes even more powerful with each 6 months.
Following about six months of operation, SPHEREx has already completed its first all sky mosaic, a collection more than 100 single exposures into a single composite. It will be the first of at least four full-sky passages scheduled in the telescope primary two-year mission, each new pass intended to overlay on the previous one to draw away less salient structures and less conspicuous signals.
The trick of SPHEREx, however, is not sharper vision, but rather more coverage. The observatory divides incoming light into 102 separate infrared wavelengths, producing what is in effect a stack of full-sky maps in which each of the colors represents a particular physical ingredient. Practically, that implies that the same section of sky may be interpreted in various ways: there are stars and hot gas and dust structures woven through the Milky Way, as well as the total light of the other galaxies that are farther than the Milky Way. This is scalable to the mission, as it is fast approaching 3,600 images per day as well as because it surveys wide; a single SPHEREx frame covers an area of sky many times larger than the snapshots of traditional space-telescopes.
The NASA management has pointed out the extent to which that combination can be helpful. Cited by Shawn Domagal-Goldman, acting director of the Astrophysics Division at NASA Headquarters: It is amazing how much data has been gathered by SPHEREx in six months time, and that this data will be highly useful when combined with the data of our other missions to gain a better understanding of our universe. He wrote: We literally have 102 new maps of the complete sky, each viewed in a different wavelength and each holding distinct information about the objects observed in them.
It is there that the engineering payoff is scientific leverage. By measuring distance to large populations of galaxies, SPHEREx will map the three dimensional distribution of matter in a volume large enough to test theories of cosmic inflation a rapid, early expansion that left subtle traces of statistical imprints in the present day distribution of galaxies. The spectral method can also be applied to track icy materials of interstellar clouds water, carbon dioxide, and carbon monoxide ice which are related to the chemistry that possibly occurs before the formation of the planet.
The sky under which SPHEREx is active is no longer an exclusively natural one too. The simulation of a low-Earth-orbit environment full of satellites predicts that satellite trails may soon become an invariable part of the wide-field space astronomy, and simulations have suggested that over 96 per cent of SPHEREx exposures may be compromised in some megaconstellation cases. The identical body of work observes that Hubble imagery has already revealed quantifiable contamination and that mitigation relies on measuring brightness, and on creating robust masking and correction into pipelines-not a one-time correction but a systematic troublesome of the systems issue that extends to spacecraft design, and to spacecraft operations and data processing.
The complication notwithstanding, the initial mosaic puts in place what is dear to mission teams and astronomers a reference sky. Repeated, 102-band coverage, and free access to the archive makes SPHEREx the place where discoveries are compared on a consistent baseline- again and again, as each new six-month sweep is located.
