Techniques to estimate reentry vehicle weather erosion parameters from satellite measurements are described. The techniques were developed over a period of three years. An empirical approach was followed with simultaneous measurements of clouds by aircraft and satellite sensors in a series of 41 cases covering a great range of cloud conditions. For each case the aircraft measurements of clouds supplemented by surface weather reports and radar pictures were converted to profiles of hydrometeor densities vs altitude. The erosion parameters predict the amount of material eroded from a nosetip and the range error of the reentry system due to erosion by ice and water particles in the atmosphere. The erosion parameters were related to infrared and visible satellite imagery data from NOAA ITOS satellites by means of non-linear equations. Equations were also developed to estimate total cloud mass and thickness from the same satellite data. Extensive applications and tests were made of the equations to estimate erosion parameters from satellite data.

A weather erosion parameter known as the Environmental Severity Index (ESI) has been estimated using infrared and visible data from satellites. Cloud sampling requirements limited the original prediction equations to satellite data averaged over a horizontal scale of 70 km. Further experiments have demonstrated great utility for satellite estimates on a scale of 10 km and also revealed some systematic differences between the coarse and the fine scale estimates. The ESI averages 1 percent to 10 percent higher for the fine scale estimates and high values of ESI are observed more frequently. (Author).