Some considerations for using AVHRR data in climatological studies: I. Orbital characteristics of NOAA satellites

Abstract Seven years of data are used to examine the orbital characteristics of five NOAA satellites and the implication for using AVHRR data in climatological studies is investigated. Generally a steady drift from a nominally Sun-synchronous orbit results in the earlier arrival of even-numbered satellites and the later arrival of odd-numbered satellites. The most extreme example of drift, for the case of NOAA-6 resulted in a difference of average arrival time of 90 minutes over the operational lifetime of the satellite. Phasing results in a ±51 minute variation in arrival time. The combination of drift and phasing can have a significant effect on the use of AVHRR and other NOAA satellite data in climatological studies, particularly for the mid- and high-latitudes during the winter and summer solstices.