Table 1. Selected characteristics of some satellite-based, visible-wavelength radiometers of potential use in the ARM Program. These are nominal values since there are slight variations among individual instruments in any given instrument series.

                                                      Nadir -
                                      Visible-        Viewing
             Operational             Wavelength        Ground      Type of
             Satellite    Orbit       Channels       Image Size    On-board
Instrument    Platform     (km)         (m)           (km)      Calibration(a)
----------   ----------- --------   --------------     ---------  ------------
AVHRR         NOAA-10      833     Ch. 1: 0.58-0.68   1.1 x 1.1    Space View
              NOAA-11    Sun Sync. Ch. 2: 0.725-1.0

VISSR/        GOES-6      35800    Ch. 1: 0.55-0.75   0.8 x 0.9    Space View
VAS           Geostat.   Geo. Sync.

TM           Landsat-4     705     Ch. 1: 0.45-0.52   0.03 x 0.03  Space View
             Landsat-5   Sun Sync. Ch. 2: 0.53-0.61                  Lamp
                                   Ch. 3: 0.62-0.69
                                   Ch. 4: 0.78-0.91

SPOT/          SPOT        832     Pan.(b) 0.51-0.73  0.01 x 0.01  Space View
HRV                      Sun Sync. Ch. 1: 0.50-0.59   0.02 x 0.02    Lamp
                                   Ch. 2: 0.61-0.59   0.02 x 0.02  Sun View
                                   Ch. 3: 0.79-0.89   0.02 x 0.02

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AVHRR: Advanced Very High Resolution Radiometer
VISSR/VAS: Visible and Infrared Spin-Scan Radiometer/VISSR Atmospheric Sounder
TM: Landsat Thematic Mapper
SPOT/HRV: Satellites Probatories d'Observations de la Terre/High Resolution Visible
GOES: Geostationary Operational Environmental Satellite
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(a) Only the space view provides a practical absolute calibration
(b) Pan. = Panochromatic