Intercomparison of MLT Winds Derived From TIMED/TIDI and UARS/HRDI

The simultaneous operation of two MLT wind sensors, the TIMED Doppler Interferometer (TIDI) and the High Resolution Doppler Imager (HRDI) provides a unique opportunity to inter-calibrate these instruments. Both instruments are Fabry-Perot interferometers used to measured emission lines in the MLT region. The TIMED and UARS satellites orbit at similar altitudes, but the orbital inclination of TIMED is 74 degrees while that of UARS is 57 degrees. This difference in inclination means that the latitude coverage is different for the two instruments and the orbital, and hence local time, precession is significantly faster for UARS (5 degrees/day) than for TIMED (3 degrees/day). There are relatively few opportunities for direct comparisons of observations co-located in space and time. Statistical methods are required to perform the most meaningful comparisons. This paper will discuss methods of comparing data from the two instruments.