Equator crossing times for NOAA, ERS and EOS sun-synchronous satellites

Abstract

The local Equator Crossing Times (EXT) of the 13 National Oceanic and Atmospheric Administration (NOAA) platforms (TIROS-N and NOAA-6 through -17) flown from 1978 until the present have been summarized as a function of time and approximated analytically. The fit equations accurately reconstruct all past EXTs to within ±2 min and also allow extrapolation in time, thus providing a useful insight into the phenomenology of its evolution. The EXTs of the three European Research Satellites (ERS: ERS1, ERS2 and Envisat) and two Earth Observing System satellites (EOS: Terra and Aqua) are also presented. In contrast to the NOAA platforms, the ERS/EOS orbits are adjusted in-flight. This makes an analytical fit to the resulting man-made EXTs impractical, and less needed as the EXTs are more stable.