Microbolometer arrays for ground-based infrared imaging

Mid-infrared observations are a vital tool for the study of a wide range of astrophysical phenomena. However, ground-based mid-infrared detectors must overcome the challenge of the overwhelming thermal background from sky and telescope emissions making them prohibitively costly for smaller (< 3 m) facilities. We describe the design and testing of a simple prototype, low-cost 10 µm imaging instrument built around an uncooled microbolometer camera. The instrument incorporates adjustable germanium re-imaging optics to rescale the image to an appropriate plate-scale for 1−2 m class telescopes and uses a gold coated chopping mirror to remove overwhelming sky background contributions. The instrument was tested with a programme of observations of bright mid-infrared sources on the 2 m Liverpool Telescope and the 1.52 m Carlos Sanchez Telescope. With these observations we confirm the instrument can be used for diffraction-limited imaging and has a photometric stability of ~10 %. We report an in-practice sensitivity limit of ~600 Jy, and a theoretical sensitivity limit of ∼ 450 Jy based on the noise equivalent differential temperature of the microbolometer system.