Sammanfattning
The AVHRR/3 imager on the NOAA-15 satellite (launched in May 1998) includes a new spectral channel at 1.6 μm ( denoted 3A) which has not been used earlier for operational monitoring of meteorological conditions. This channel has been available in research mode from the ATSR instrument onboard the ERS satellites and from the Thematic Mapper instrument of the Landsat satellites. However, the use of channel 3A for NOAA-15 will be restricted to a few test periods since the 3.7 μm channel (denoted 3B) will still be maintained as the operational A VHRR channel 3. Such a test period occured during the spring of 1999. From March 9th until April 20th NOAA-15 were transmitting AVHRR Channel 3A and 3B data according to the following schedule: Channel 3A was operational during daylight passes only, as the spacecraft crosses the terminator into daylight, with the additional constraint that the spacecraft subpoint is North of 40 degrees N. As the spacecraft crosses the terminator into darkness, Channel 3A is toggled off, and Channel 3B toggled on.