Correction for ionospheric refraction for COBRA DANE

A hit-to-hit correction for range error arising from ionospheric refraction has been developed for the COBRA DANE radar. First a FORTRAN procedure was developed to compute monthly median refraction corrections over the field of view. These were provided to the radar in the form of equivalent look-up tables. A FORTRAN program was developed for the radar computed index values for each target position (azimuth, elevation, and range) and a correction was determined for each radar hit. This procedure removed about 75 percent of the monthly mean ionospheric effect. A further reduction was then made by using first and update factor determined by the Air Force Global Weather Central and then a more accurate update derived from a two-frequency calibration made by the radar itself. These procedures are shown to be capable of removing up to 90 percent of the mean ionospheric effect.