The HALOE home page on the WWW is
                  http://haloe.gats-inc.com/home/index.php
                  
                  The Halogen Occultation Experiment (HALOE) on NASA's Upper Atmosphere
                  Research Satellite (UARS) investigates upper atmosphere chemistry,
                  dynamics and radiative processes, particlarly stratospheric ozone
                  destruction and chlorofluromethane impact on ozone.
                  
                  HALOE is a solar occultation experiment designed to monitor the
                  vertical distribution of HCl, HF, CH4, and NO by gas filter
                  correlation radiometry and H2O, NO2, O3, and CO2 by broadband filter
                  radiometry.  The HALOE instrument typically views 15 sunrise and
                  sunset events each day, scanning the solar disk from limb to limb
                  during each event.  The latitude/longitude location of the HALOE data
                  varies with the spacecraft-Earth-Sun position.  For a given day, the
                  locations tend to be in two distinct latitude bands and to sweep
                  across the full longitude range.  Coverage across the full range of
                  latitudes is achieved on a time period ranging from about two to six
                  weeks depending on the time of year.  The latitude coverage extends
                  from 80 degrees north to 80 degrees south.
                  
                  The HALOE level 3AT data consist 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), 2) AEXTCO2 - aerosol extinction at 2.80 um (CO2 gas
                  filter), 3) AEXTHCL - aerosol extinction at 3.40 um (HCL gas filter),
                  4) AEXTHF - aerosol extinction at 2.45 um (HF gas filter), 5) AEXTNO -
                  aerosol extinction at 5.26 um (NO gas filter), 6) CH4 - methane, 7)
                  H2O - water vapor, 8) HCL - hydrogen chloride, 9) HF - hydrogen
                  fluoride, 10) NO - nitric oxide, 11) NO2 - nitrogen dioxide, 12) O3 -
                  ozone, and 13) TEMP - atmospheric temperature.  Aerosol extinction
                  coefficients are measured in units of 1/km, chemical species are given
                  in parts per million by volume (ppmv), and temperature is in units of
                  degrees Kelvin.
                  
                  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 HALOE level 3AT data product 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 3AT format is
                  common to all UARS instruments to allow for intercomparison.  The
                  level 3AT data product consists of time-ordered profiles, and are
                  spaced at intervals of 1 UARS minute (65.536 seconds), or about 495 km
                  along the tangent track (horizontal resolution).  The vertical
                  resolution for the level 3AT HALOE profiles is defined by the UARS
                  pressure levels (in mbars) given by:
                  
                  P(i) =  1000 * 10**(-i/6) for i = 0, 1, 2,...