Use of dispersion to eliminate multipath in planetary radio occultations

Journal Article · Thu Jul 01 00:00:00 EDT 1976 · Radio Sci.; (United States)

DOI:https://doi.org/10.1029/RS011i007p00629· OSTI ID:7181663

Croft, T A

During planetary atmospheric and ionospheric study through radio occultation of spacecraft, multipath propagation often occurs at several altitudes in the medium. Although the signals are then simultaneous in time, they are separate in frequency. It is shown that dispersion can be used to separate such signals because they are inherently single-valued with respect to a family of curves having dT/dF = lambdaD/V/sup 2/ (where F = frequency, T = time, V = velocity normal to the limb, lambda = wavelength, and D = distance from the spacecraft to the limb plane). The concept underlying this corrective measure is much like that of an FM--CW radar wherein frequency separation is converted to time separation. Application of the recommended dispersion may eliminate a major form of multipath and permit signal detection by receivers employing phase-lock loops that depend for their action on the existence of only one frequency. This should facilitate the processing of open-loop recorded data and it might permit the closed-loop reception of multipath signals without loss of information, making possible the observation of radio occultations with signals from Earth to spacecraft. Heretofore, this approach has not shown promise in multipath situations. No specific processes or designs are given, but there is a practical discussion concerning the degree of accuracy that must be provided in flight and during postflight analysis.

• Research Organization: Stanford Univ., CA
• OSTI ID: 7181663
• Journal Information: Radio Sci.; (United States), Vol. 11:7
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
PLANETARY ATMOSPHERES
WAVE PROPAGATION
DISPERSION RELATIONS
DISTANCE
EARTH PLANET
IONOSPHERE
PLANETS
RADIOWAVE RADIATION
SIGNALS
TIME DEPENDENCE
ATMOSPHERES
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
RADIATIONS
640107* - Astrophysics & Cosmology- Planetary Phenomena