A description of the High Resolution Dynamics Limb Sounder (HIRDLS) instrument

We describe the top level design of the High Resolution Dynamics Limb Sounder (HIRDLS) instrument including the optical and scanning subsystems which have been developed to meet 0.7 arcsec pointing and the 1% radiometric accuracy requirements. The HIRDLS instrument is an infrared limb-sounding radiometer designed to sound the upper troposphere, stratosphere, and mesosphere. The instrument performs high resolution limb scans at multiple azimuth angles, measuring infrared emissions in 21 spectral channels' ranging from 6 to 18 microns. The instrument design includes an off-axis Gregorian telescope with high resolution optical shaft encoders, a silicon carbide scanning mirror, and a vibration isolation system incorporating accelerometers in a feed-forward scanning control system. The detector subsystem includes 21 HgCdTe detector elements cooled by a mechanical Stirling cycle cooler.