Why should we go to the expense of launching satellites
in order to gather spectral data that we could obtain from earth-based telescopes?
Because, unfortunately, the earth's atmosphere does not allow light of all
wavelengths to pass through it. In fact, the atmosphere will only allow
visible light and some long-wavelength radio waves to pass through it. In
order to see gamma, X ray, ultraviolet (UV), infrared, and microwave radiation
from space, we must place telescopes and other light-gathering instruments
above the atmosphere.