Infrared techniques

In general infrared techniques make the observation of relatively cool objects in the universe possible. Objects that are not visible in the optical, ultraviolet or X-ray spectrum. It also enables astronomers to look through dense areas of dust and gas.

An image of a planet forming in the protoplanetary disk around the young star PDS 70. The light of the central star is blocked out. (photo: ESO/A. Müller et al.)

Good examples of the cool objects mentioned above are protoplanetary disks around young stars in which new planets are formed. Large young planets (gas giants) radiate infrared radiation and can be detected as well.

Infrared measurements on Earth are challenging because water vapour in our planet’s atmosphere blocks a large part of the infrared radiation of astronomical sources. Observations are mostly done by space telescopes or Earth based telescopes at high elevations.

Mirrors and detectors need to be cooled to temperature well below freezing – minus 200 degrees Celsius – to minimise infrared (heat) radiation that would otherwise render the observations useless.

METIS

At LEOPARD we have developed several parts and techniques for the mid-infrared imager and spectrograph METIS that will be installed on the Extremely Large Telescope. The development was possible through close collaboration with the NOVA Optical IR Instrumentation Group at ASTRON.

We have worked on the following techniques.
 
  • cryogenic, ultra-fast beam chopping mirror (see photograph)
  • high resolution immersed grating (made of germanium)
  • cryogenic “set-and-forget” mirror
  • ultra-precise image derotator optics
  • polished precision aluminium mirrors
  • APP coronagraphic masks
  • infrared detector specification and testing
Prototype of METIS ‘cold chopper’ mirror which is crucial to the performance of the instrument. It quickly ‘switches’ the image between infrared sources and other parts of the sky. The design of the cold chopper is by JPE. (photo: Roel van der Heijden)

MATISSE

LEOPARD scientists are also involved in the MATISSE instrument (Multi AperTure mid-Infrared SpectroScopic Experiment) of the Very Large Telescope which astronomers use to observe protoplanetary disks, minor bodies in our solar system and young giant exoplanets.

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