HR: 0830h
AN: P41B-0405    [PDF]
TI: Resolving Diffractive Atmospheric and Surface Structures at Pluto Using New Horizons Multiple Frequency Radio Occultation and Back Propagation
AU: * Han, C
EM: chinsan@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305 United States
AU: Tyler, G
EM: len.tyler@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305 United States
AB: In a typical planetary radio occultation, a single frequency tone is transmitted toward a receiver as the line of sight is obstructed by or emerges from behind the planet limb, referred to as ingress and egress occultation, respectively. As the line of sight passes through the atmosphere, the carrier tone experiences a phase shift caused by both geometric and wave optic effects, e.g., refraction and diffraction. This phase information can be converted to refractivity, temperature, and pressure profiles using the Abel inversion. While this method is a very powerful tool for resolving atmospheric features, the Abel inversion is inherently diffraction-limited since it assumes geometrical optics. Therefore, by itself, the Abel inversion cannot resolve sub-Fresnel-scale structures such as sharp inversions and the planet limb. These features cause diffractive ringing in the occultation signal that limits vertical resolution in atmospheric profiles to the Fresnel scale. This is of special concern near the planet surface where the limb, behaving as a diffracting edge, can completely overwhelm subtle phase data from low altitude atmospheric features. This research addresses these problems for radio occultation experiments planned in the New Horizons mission to Pluto. The diffraction signatures from both hypothetical atmospheric structure as well as the planet limb have been modeled for single tone occultation. Further, back propagation has been determined to be an effective means of reducing the Fresnel scale. Abel inversion applied to back-propagated simulated data yields profiles with vertical resolutions improved by an order of magnitude. The New Horizons mission will also attempt to utilize multiple tones in order to produce additional profiles for a single occultation pass. This research has modeled the interaction of simultaneous, multiple tone occultation carriers and investigates the interaction and limitations imposed by the existence of multiple carriers on back propagation.
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 0350 Pressure, density, and temperature
DE: 6270 Pluto and satellites
DE: 6900 RADIO SCIENCE
DE: 6964 Radio wave propagation
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting