Near Infrared Instrumentation for Large Telescopes

This paper reviews near infrared instrumentation for large telescopes. Modern instrumentation for near infrared astronomy is dominated by systems which employ state-of-the-art infrared array detectors. Following a general introduction to the near infrared wavebands and transmission features of the atmosphere, a description of the latest detector technology is given. Matching of these detectors to large telescopes is then discussed in the context of imaging and spectroscopic instruments. Both the seeing-limited and diffraction-limited cases are considered. Practical considerations (e.g. the impact of operation in a vacuum cryogenic environment) that enter into the design of infrared cameras and spectrographs are explored in more detail and specific examples are described. One of these is a 2-channel IR camera and the other is a NIR echelle spectrograph, both of which are designed for the f/15 focus of the 10-m W. M. Keck Telescope. The Near Infrared Waveband In the last ten years there has been tremendous growth in the field of Infrared Astronomy. This growth has been stimulated in large part by the development of very sensitive imaging devices called infrared arrays . These detectors are similar, but not identical, to the better-known silicon charge-coupled device or CCD, which is limited to wavelengths shorter than 1.1 µm. In particular, near infrared array detectors are now sufficiently sensitive that images of comparable depth to those obtained with visible-light CCDs can be achieved from 1.0 µm to 2.4 µm and high resolution IR spectrographs are now feasible.