Accession Number : AD0922542

Title :   Single-Frequency Refraction-Free Satellite Navigation.

Descriptive Note : Technical memo.,

Corporate Author : JOHNS HOPKINS UNIV LAUREL MD APPLIED PHYSICS LAB

Personal Author(s) : Schwab, V. ; Prozeller, E. F.

Report Date : JAN 1974

Pagination or Media Count : 85

Abstract : The Triad satellite was launched in September 1972 as an experimental member of the Navy Navigation Satellite System and contained several innovative experiments. PRN(pseudorandom noise) modulation was applied for the first time to the 150- and 400-MHz carriers transmitted by Triad. This modulation made possible a direct measurement of the instantaneous slant range between Triad and a modified SRN-9 integral doppler receiver located at APL. The receivers also made conventional integral doppler measurements over nominal 4.6-second intervals. Integral doppler measurements are proportional to changes in the satellite-to-receiver phase pathlenght, while PRN-ranging measurements are proportional to the length of the group path. The differences in length between the vacuum path and the phase and group paths are due primarily to the presence of the ionosphere. At frequencies of 400-MHz or above, the group path exceeds and the phase path falls short of the vacuum pathlength (true slant range) by nearly equal amounts.

Descriptors :   *DOPPLER NAVIGATION), (*NAVIGATION SATELLITES, REFRACTION, PSEUDO RANDOM SYSTEMS, PSEUDO NOISE SYSTEMS, MODULATION, ALGORITHMS, IONOSPHERE.

Subject Categories : Unmanned Spacecraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE