Transparency of the atmosphere

Transparency of the atmosphere

In this diagram, the brown curve shows how transparent the atmosphere is at the given wavelength to radiation from space. The major windows are at visible wavelengths (marked by the rainbow) and at radio wavelengths from about 1 mm to 10 m. ALMA operates in a borderline region, where the opacity depends strongly on how high and dry the site is. In space, observations can be done outside the atmospheric windows as illustrated by XMM-Newton, Hubble and the Spitzer Space Telescope.