The Halogen Occultation Experiment (HALOE) Level 3AT data product consists of daily vertical profiles of temperature, aerosol extinction and concentrations of HCl, HF, CH4, NO by gas filter correlation radiometry and H2O, NO2, O3 by broadband filter radiometry.  The instrument measured atmospheric infrared absorption at wavelengths from 2.43 to 10.25 microns.  HALOE was flown on NASA's Upper Atmosphere Research Satellite (UARS) to investigate upper atmosphere chemistry, dynamics and radiative processes, particlarly stratospheric ozone destruction and chlorofluromethane impact on ozone.  HALOE is a solar occultation experiment which typically views 15 sunrise and sunset events each day. Limb measurements were made in the altitude range between 15 km and 60 - 130 km (depending on channel) with about 2.5 km resolution. For a given day, the profiles were in two distinct latitude bands, for the sunset and sunrise events.  Coverage across the full range of latitudes between 80S and 80N was achieved on a time period ranging from about two to six weeks, depending on the time of year. The HALOE Level 3AT data were processed with the version 19 algorithm.
                                                      
The HALOE level 3AT product consists of 13 granules per day. A data granule is one HALOE species or subtype per day.  The following subtypes are available:

 1) AEXTCH4 - aerosol extinction at 3.46 um (CH4 gas filter)  [1/km]
 2) AEXTCO2 - aerosol extinction at 2.80 um (CO2 gas filter)  [1/km]
 3) AEXTHCL - aerosol extinction at 3.40 um (HCL gas filter)  [1/km]
 4) AEXTHF  - aerosol extinction at 2.45 um (HF gas filter)   [1/km]
 5) AEXTNO  - aerosol extinction at 5.26 um (NO gas filter)   [1/km]
 6) CH4     - methane                                         [vmr]
 7) H2O     - water vapor                                     [vmr]
 8) HCL     - hydrogen chloride                               [vmr]
 9) HF      - hydrogen fluoride                               [vmr]
10) NO      - nitric oxide                                    [vmr]
11) NO2     - nitrogen dioxide                                [vmr]
12) O3      - ozone                                           [vmr]
13) TEMP    - atmospheric temperature                         [Kelvin]

*vmr = volume mixing ratio

HALOE data are on the UARS standard pressure levels (in mbars) given by:

P(i) =  1000 * 10**(-i/6)  for i = 0, 1, 2, ... 54

Each of the 13 HALOE granules is accompanied by 2 additional parameter files, designated as level 3TP.  The first parameter file, subtype LAT, contains the latitude values for each pressure level of each event for the day.  The second parameter file, subtype LON, contains the longitude values.  The level 3AT files only contain the latitude/longitude location corresponding to the 30 km retrieval point. The data files are available in a binary record oriented format.