Figure: Above the atmosphere

The Universe emits a tremendous amount of information in the form of different types of electromagnetic radiation. Only a small fraction of this is visible from the Earth (white areas) as the atmosphere absorbs the rest before it reaches the ground (black areas). Water vapour, ozone and carbon dioxide in the atmosphere absorb large parts of the infrared spectrum so most infrared astronomical observations have to be carried out at high altitude by instruments mounted below balloons or in rockets or spacecraft. The higher above the atmosphere an infrared telescope is, the better the observing conditions. Apart from problems with atmospheric absorption, the atmosphere is itself also a source of infrared radiation, with a typical temperature of 10 C, making infrared observations of the coolest objects in the Universe difficult from the ground.

Credit: "The infrared revolution, unveiling the hidden universe", Monica Salomone, Lars Lindberg Christensen, Bruce Battrick, Martin Kornmesser (Hubble ESA Information Centre)

http://www.spacetelescope.org/about/further_information/brochures/html/infrared.html