Low Latitude Thermospheric Winds Observed by the Timed Doppler Interferometer (tidi) during the C/nofs ERA

The TIMED Doppler Interferometer, TIDI, began synoptic observations of the upper thermosphere on 25 September 2008, four months after the launch of C/NOFS. The upper thermosphere is sampled with the routine science mode at tangent heights from 160 to 300 km at 20 km increments, at 4 seconds per altitude sample. Unlike C/NOFS, the precession rate of the TIMED satellite is slow (12 minutes per day) implying that TIDI samples any latitude circle every 24 degrees of longitude at approximately the same dayside Local Solar Time (LST) and the same nightside LST. Over the latitude range monitored by C/NOFS, TIDI performs at least 4 altitude scans through the upper thermosphere on each side of its orbit providing at least 120 horizontal wind vector measurements per day that are pertinent to C/NOFS science. This paper will summarize the past two years of horizontal neutral wind observations at low latitudes. It is quite clear that the signal level of the raw OI (6300A) spectra has increased since September 2008, corresponding to the increase in the solar flux. This provides higher confidence in Doppler wind retrievals.