The Cryogenic Limb Array Etalon Spectrometer (CLAES) on NASA's Upper Atmosphere Research Satellite (UARS) measured the chemical composition of the stratosphere and mesosphere, and also investigated the depletion of stratospheric ozone and ozone chemistry.
The CLAES instrument measured the thermal emission ... spectra from the Earth's limb perpendicular to the spacecraft velocity vector. The characteristic vibration-rotation line spectra of atmospheric chemical species was measured simultaneously at 20 different limb altitudes in the 10 to 60 km range, with 2.5 km vertical resolution. An iterative relaxation algorithm inverted the measured radiance to yield profiles of temperature and concentrations of O3, H2O, CH4, N2O, NO, NO2, N2O5, HNO3, ClONO2, HCl, CF2Cl2 (CFC-12), CFCl3 (CFC-11), and aerosol absorption coefficients. The CLAES instrument consisted of a solid-etalon Fabry-Perot spectrometer cooled to 18K by a neon and carbon dioxide cryostat designed for an 18-month lifetime (the cryostat lasted 20 months before being exhausted). The etalon detectors had central wavelengths of 2843, 1897, 1605, 1257, 925, 879, 840, 792, and 780 cm^-1 (3.5 to 12.7 micron coverage)
The CLAES level 3A data products consist of profiles that have been interpolated both vertically and horizontally from the original profiles to standard surfaces and locations defined by the UARS project for all limb-viewing instruments. The level 3A format is common to all UARS instruments to allow for intercomparison. The CLAES level 3A data products consist of two product classes; 3AT time-ordered level 3A data, and 3AL latitude-ordered level 3A data.
The level 3AT data products consist of time-ordered profiles, and are spaced at intervals of 1 UARS minute (65.536 seconds), or about 495 km along the tangent track. Level 3AL data products consist of profiles at the intersection of the tangent track spaced at intervals of 4 degrees latitude (e.g. 80, 76, 72, ..., -72, -76, -80).
The CLAES level 3AT and 3AL data consist of 20 granules per day each. A data granule is one CLAES species or subtype per day. The following subtypes are available: 1) AERO780 - aerosol extinction at 780 cm-1, 2) AERO790 - aerosol extinction at 790 cm-1, 3) AERO843 - aerosol extinction at 843 cm-1, 4) AERO880 - aerosol extinction at 880 cm-1, 5) AERO925 aerosol extinction at 925 cm-1, 6) AERO1257 - aerosol extinction at 1257 cm-1, 7) AERO1605 - aerosol extinction at 1605 cm-1, 8) AERO1897 - aerosol extinction at 1897 cm-1, 9) CF2CL2 - CFC-12, 10) CFCL3 - CFC-11, 11) CH4 - methane, 12) CLONO2 - chlorine nitrate, 13) H2O - water vapor, 14) HNO3 - nitric acid, 15) N2O - nitrous oxide, 16) N2O5_OTHER - dinitrogen pentoxide, 17) NO - nitric oxide, 18) NO2 - nitrogen dioxide, 19) O3B9 - ozone at 780 cm-1 (filter 9), and 20) TEMP - atmospheric temperature. Aerosol extinction coefficients are measured in units of 1/km, chemical species are given in mixing ratios, and temperature is in units of degrees Kelvin. The data are at version 9 (except H2O which is version 7).
The horizontal resolution is 495-km along-track for the level 3AT files, and 4 degrees latitude for the level 3AL files. The vertical resolution for the CLAES profiles is defined by the UARS pressure levels (in mbars) given by:
P(i) = 1000 * 10**(-i/6) for i = 0, 1, 2, ...
which gives approximately 2.5 km increments between pressure surfaces.