Are we tracking the spectra of everything visible in the sky? How much data is that?
Are we tracking the spectra of everything visible in the sky? How much data is that?
We have photometric all-sky surveys that can map the entire sky (visible from the telescope location) during a night up to a certain brightness. But those only take images of the sky, not spectra (Zwicky Transient Facility and the planned Vera C. Rubin Observatory).
What we also have are integral-field spectrographs which can take 2D images with a twist: there is one image for every ~0.1nm from 480nm to 950nm. You take one exposure with the instrument and you get a stack of thousands of images. If you go through the stack at a fixed spatial position you get the spectrum. The problem is that the integral-field spectrograph with the largest field-of-view is already huge (it is called MUSE at is located at the Very Large Telescope). And its field-of-view is "only" 1 arcmin^2 (1 deg = 60 arcmin), which is by far too small for large surveys. If you wanted to image the whole sky each night with MUSE clones, you would need several millions of them. A single MUSE exposure is about ~5 GB in the end but there are intermediate data products which are about 10 GB, if I remember correctly.