A MEDIUM EARTH ORBIT CONTELLATION FOR POLAR WIND MEASUREMENTS

Low Earth orbits (LEO) and Geostationary Earth orbits (GEO) orbits have traditionally been the venues of choice for observations, albeit for very different reasons. LEO provides high spatial resolution with low temporal resolution while GEO provides for low spatial resolution, but high temporal resolution. NOAA utilizes both venues for their environmental satellites. The NOAA Polar-orbiting Operational Environmental Satellites (POES) reside in LEO Sun synchronous orbits at approximately 830 km in altitude, as do the Defense Meteorological Satellite Program (DMSP) satellites of the Department of Defense. In the near future the POES and DMSP satellites will be merged into a new satellite system referred to as the National Polar-orbiting Operational Environmental Satellite System (NPOESS). The NOAA Geostationary Operational Environmental Satellite (GOES) system, as the name specifies, resides at the other preferred observational venue of GEO. At the same time, wind information from NASA’s MODIS sensors on the satellite Terra and Aqua, has been shown to provide unexpectedly large improvements in numerical model predictions. This is true, even thought the winds are derived from images of cloud features which are separated by about 100 minutes. This study describes efforts to attain full coverage of regions of the Earth poleward of 60 degrees latitude (i.e., both poles) on a continuous basis, 24 hours a day, seven days a week. Such a system would b