Altitude profiles of lower thermospheric temperature from RAIDS/NIRS and TIMED/SABER remote sensing experiments

Thermospheric temperatures derived from limb observations of the O-2 A-Band (0,0) emission spectrum obtained from January-July 2010, with the Remote Atmospheric and Ionospheric Detection System (RAIDS) Near Infrared Spectrometer (NIRS) aboard the International Space Station, are compared to temperature results from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment. To account for a lack of simultaneous common volume observations, the observed temperatures were scaled by the NRLMSIS-00 model temperatures for comparison. It was found that on average SABER, temperatures are warmer than NIRS at all altitudes between 90 and 140km. In the altitude range 90-100km, the SABER temperatures were warmer than NIRS by similar to 10K consistent with previous validation experiments and in agreement with Optical Spectrograph and Infrared Imaging System (OSIRIS) O-2 A-band comparisons in the polar mesopause region. At higher altitudes, the differences between SABER and NIRS exceed 30K on average. Thus, the NIRS observations reinforce the idea that the SABER temperatures are too warm below similar to 110km; and above that altitude, they are increasingly in error consistent with expectations based on estimated inaccuracies in the retrieval algorithm. Large standard deviations of the SABER and NIRS ratios are reflective of substantial variability of the thermospheric temperatures throughout the region.