The infrared waveband is usually, by convention, split into three parts: near-infrared, mid-infrared and far-infrared. The significance behind this distinction in terms of observing these wavelength regimes is the varying opacity of our atmosphere.
Telescopes observing in the near-infrared regime can be ground-based, because atmospheric opacity is - albeit worse than in the optical band - not prohibitive. Therefore, many observatories listed as "optical observatories" also have instruments operating at near-infrared wavelengths, in the range from 1 to a few micrometers.
Examples of dedicated ground-based near-infrared telescopes are:
- The United Kingdom Infra-Red Telescope, UKIRT (external link)
- The three automated 1.3-m telescopes collecting data for the 2 Micron All-Sky Survey (2MASS; external link) on Mount Hopkins (2 telescopes) and at Cerro Tololo (CTIO; 1 telescope)
A new dedicated infrared space observatory that is currently in the design and development phase is:
- James Webb Space Telescope, formerly the "Next Generation Space Telescope", NGST (external link)
All other near-infrared telescopes are equipped with both optical and near-infrared detectors. Here a few examples:
- The two 10-m telescopes of the Keck observatory (external link)
- ESO's Very Large Telescope (VLT)
- Also the Hubble Space Telescope, HST (external link) has near-infrared detectors on-board.
Although atmospheric transparency becomes worse at longer wavelengths, there are still windows that can be used. With adequate instrumentation telescopes that operate in the near-infrared regime can extend their range by observing into the mid-infrared regime, from about 2 to 15 micrometers.
Examples for instrument working in this waveband are:
- The LWS camera and spectrometer on the Keck telescopes (external link)
Beyond about 15 micrometers wavelength observations through (parts of) the atmosphere undergo severe losses due to absorption of light. Therefore, far-infrared emission is normally observed from high in or above the atmosphere.
There is, to my knowledge, only one observatory that, until 1995, observed routinely from high within the atmosphere, namely NASA's
- Kuiper Airborne Observatory (KAO),
Its next-generation successor will be called the
- Stratospheric Observatory For Infrared Astronomy, SOFIA (external link)
However, normally one will go even higher to escape the disturbing influence of our atmosphere and observe far-infrared emission from outer space, using satellites. Some examples:
- Infra-Red Astronomical Satellite, IRAS (external link)
- Infrared Space Observatory, ISO (external link)
- Spitzer Space Telescope (formerly the Space Infra-Red Telescope Facility, SIRTF; external link)
A future far-infrared (to mm-wavelength radio) space observatory will be
- Planck (external link)
The reason why I am not showing photos of ground-based infrared telescopes is that I have not visited one yet (except for the VLT). As for the satellites - maybe I can get a ticket some day for a trip... and showing pictures from the clean rooms in which they were assembled and tested is just not the same.
A special observing mode that is available in the optical/near-infrared waveband since only a very short time is interferometry .