The visible and near-infrared domain

Space observations at visible and near-infrared wavelengths are free from the absorption, high foreground radiation and wavefront distortion caused by the Earth’s atmosphere. The absence of these effects in space permits observations of higher sensitivity and stability with better angular resolution and with a larger dynamic range than their counterparts from the ground. Observations from the Hubble Space Telescope, the ISO and Spitzer satellites and survey satellites such as IRAS are still unsurpassed by ground-based telescopes for their sensitivity, radiometric stability, angular resolution over large fields of view, dynamic range and complete spectral coverage. This chapter discusses the inherent limitations of ground-based astronomy that are overcome by space observations and lists some of the spacecraft that have demonstrated these advantages for scientific study.