HR: 0800h
AN: A51D-0816    [Abstracts]
TI: Retrieval of Thermospheric Molecular Oxygen Profiles from Solar and Stellar Occultation Measurements.
AU: * Lumpe, J
EM: lumpe@cpi.com
AF: Computational Physics, Inc, 8001 Braddock Road, Suite 210, Springfield, VA 22151 United States
AU: Floyd, L
EM: linton.floyd@nrl.navy.mil
AF: Interferometrics, Inc., 14120 Parke Long Court, #113 , Chantilly, VA 20151 United States
AU: Snow, M
EM: marty.snow@lasp.colorado.edu
AF: University of Colorado, LASP, Campus Box 392 UCB, Boulder, CO 80309 United States
AU: Picone, J M
EM: picone@uap2.nrl.navy.mil
AF: Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 United States
AU: Rottman, G
EM: gary.rottman@lasp.colorado.edu
AF: University of Colorado, LASP, Campus Box 392 UCB, Boulder, CO 80309 United States
AB: We present two new data sets of thermospheric molecular oxygen (O2) density profiles retrieved from both solar and stellar occultation measurements. The solar occultation measurements are made by the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) instrument onboard the UARS satellite, and the stellar occultations are obtained from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) on the SORCE satellite. Both instruments are nominally solar experiments whose primary mission is to measure the magnitude and variability of the UV solar irradiance. However, a simple extension of either the operational solar measurements (in the case of SUSIM) or the daily stellar calibration sequence (in the case of SOLSTICE) provides an opportunity to remotely sense the Earth's upper atmosphere using occultation. By measuring the attenuation of sunlight or starlight in the O2 Schumann Runge continuum (140 - 170 nm), it is possible to retrieve density profiles of O2 in the thermosphere (120 - 250 km). Since October 1991, SUSIM has performed solar occultation measurements one day per week, measuring full-disk solar extinction as a function of tangent altitude at 141, 160 and 171 nm. Over 1500 occultation profiles are currently available for analysis, spanning a wide range of solar and geomagnetic activity. Two identical SOLSTICE instruments have been operating onboard the SORCE satellite since January 2003. In the first year of operation approximately 100 occultation events were obtained but since May 2004 these measurements have been made on a routine basis, approximately 10 times per week. Both data sets cover a wide range of latitudes in each hemisphere - up to 67.5 degrees for SOLSTICE and 75 degrees for SUSIM. Retrieval of O2 density profiles from the SUSIM and SOLSTICE transmission measurements is achieved using an optimal estimation inversion algorithm, similar to the operational algorithms used for the POAM II and III multi-wavelength solar occultation instruments. We present the retrievals obtained from these two data sets, and use them to study trends in the variation of O2 density as a function of latitude, season, local time, and solar and geomagnetic activity. The results of this parametric analysis will be compared systematically to the predictions of the MSIS-90 and NRLMSIS-00 thermospheric models.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0355 Thermosphere--composition and chemistry
DE: 0360 Transmission and scattering of radiation
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting