The AIRS Instrument
The Atmospheric Infra-Red Sounder (AIRS) instrument is a
- hyperspectral – measures a large number of wavelengths over a two-dimensional field of view, creating a ‘data cube’
- infrared – observes in the wavelengths redder than the eye can see
- atmospheric sounder – uses multiple, simultaneous wavelength measurements to understand the atmosphere as a function of altitude.
AIRS is part of the AIRS Project Instrument Suite.
Lockheed Martin Infrared Imaging Systems (LMIRIS) of Lexington, Massachusetts (initially part of Honeywell Electro-Optics Division, and then Loral) built AIRS under contract to NASA's Jet Propulsion Laboratory (JPL). LMIRIS has since become part of BAE Systems. LMIRIS also developed the infrared detectors. In addition to project management, JPL’s role in the development included requirements definition, design analyses, component and subsystem manufacturing support, test program support, spacecraft integration and test leadership, and on-orbit operations.
Five technology developments were required for AIRS:
- low-noise detectors for the wavelength range 3.7-15.4 μm
- low-vibration and long-lifetime cryocoolers used to keep the detectors cold
- Entrance aperture filters and Focal plane filters
- Detector read-out electronics and multiplexers
- Ruled aspheric gratings
Energy from the scan mirror is also directed to a set of visible and near infrared (Vis/NIR) photometers to observe low-level clouds in four bands. Low-level clouds are difficult to detect using longer wavelengths because low-level clouds are about the same temperature as the ground. The longer wavelengths used by the AIRS spectrometer and AMSU-A depend on temperature differences to differentiate emission from various altitudes.
The Electronics System has over 30,000 electronic parts. The system is microprocessor-controlled and has a high degree of configuration flexibility via ground commands. The overall electronics design emphasized radiation tolerance and redundancy to increase lifetime.
The Mechanical System maintains alignment stability and boresight relative to the spacecraft, after exposure to the environmental loads and gravity release.