Accession Number : ADP009127

Title :   Measurement of the Frequency Stability of Responders in Aircraft,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GREENBELT MD GODDARD SPACE FLIG HT CENTER

Personal Author(s) : Liu, Xiaofan

Report Date : 02 DEC 1993

Pagination or Media Count : 12

Abstract : Measurement on an aircraft orbit, such as a satellite launching orbit, is made by the responder in the aircraft along with several remote track stations on the ground. During the launching, the system is required to have precise time synchronization and frequency accuracy. At the same time, accurate measurement of aircraft velocity requires high frequency stability of the system. However, atomic frequency standards in the ground stations supply time and frequency reference standard with excellent long term and short term frequency stability for the above-mentioned goals. The stability of responder is also an important factor affecting the performance of the system and there are more requirements for the corresponding time/ frequency measurements. In the system, the responders do not use continuous wave (CW) but narrow pulse modulated wave, consequently, the characterization theory of their stability is more complicated and the measurement technique is more difficult for pulsed wave than that for CW.

Descriptors :   *FREQUENCY STANDARDS, *MEASUREMENT, *TRACKING, *RECONNAISSANCE SATELLITES, *FLIGHT PATHS, *TRANSPONDERS, ACCURACY, AIRCRAFT, CONTINUOUS WAVES, GROUND STATIONS, REQUIREMENTS, STABILITY, STATIONS, THEORY, TIME, TRACKS, CHINA, PULSE MODULATION, HIGH RESOLUTION.

Subject Categories : Space Navigation and Guidance

Distribution Statement : APPROVED FOR PUBLIC RELEASE