HR: 16:35h
AN: SH52B-03    [PDF]
TI: GPS Occultation Sensor Observations of the Ionospheric E-Region
AU: * Straus, P R
EM: paul.straus@aero.org
AF: The Aerospace Corporation, Mail Stop M2-259 PO Box 92957, Los Angeles, CA 90009-2957 United States
AU: Hajj, G A
EM: george.hajj@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Anderson, P C
EM: phillip.anderson@aero.org
AF: The Aerospace Corporation, Mail Stop M2-259 PO Box 92957, Los Angeles, CA 90009-2957 United States
AU: Crowley, G
EM: gcrowley@swri.edu
AF: Southwest Research Institute, 6220 Culebra Road P.O. Drawer 28510, San Antonio, TX 78228-0510 United States
AB: GPS occultation sensor measurements of the GPS L1 (1575 MHz) and L2 (1227 MHz) signal phase can be used to derive line-of-sight total electron content (TEC). The GPS TEC values are highly precise in a relative sense, with noise levels on the order of ~0.01 TECu. Limb-viewing occultation profiles of vertical TEC may be converted into electron density profiles by means of the Abel transform. The high relative TEC accuracy potentially leads to very precise profiles, resulting in an ability to remotely sense density features below the 10E4/cc level. Thus one would expect GPS occultations to provide a new means for observing E-region features. This is particular true because the E-region often has significant vertical refractivity gradients, to which the occultation technique is particularly sensitive. However, the absolute accuracy of these retrievals can be compromised by the presence of F-region gradients, which violate the Abel assumption of spherical symmetry. We present an initial analysis of the gradient effects on E-region retrievals and discuss methods to mitigate the effects of asymmetry. Examples from simulations and actual observations from the Ionospheric Occultation Experiment (IOX) will be presented to illustrate our results. The utility of low-density E-region measurements will be discussed in the context of validation of models predicting the evolution of the structure of the post-sunset equatorial anomaly region.
DE: 2415 Equatorial ionosphere
DE: 2494 Instruments and techniques
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting