Time Delay Changes With Temperature in a TWSTT Monitoring System

Phu Mai, James DeYoung

Abstract:	The US. Naval Observatory (USNO) Time Service (TS) uses the AOA TWT-100 AtIantis Modem for its most important Two-Way Satellite Time Transfer (TWSTT) application. A method was devised to measure delay changes due to hardware failures in an operational monitoring system. The VSAT on the Roof (VSR) of building 78 is a 1.8-meter dish using a SKYDATA RF unit and is used as the primary operational earth station for TWSTT with the USNO Alternate Master Clock (MC) located at Falcon AFB, Colorado and for other stations. The Mobile Earth Station (MES) monitors the VSR performance bymaking six experiments per day. A second 1.8-meter VSat on the other roof (VSO) is also used us a monitoring system. As long as the hardware remains in normal operating specifications, a constant time difference should result. The MES, VSR, and VSO are co-located with a common-clock refernence, Master Clock 2 (MC 2). Temperature measurements were taken using a thermocouple-based temperature measuring system. The thermocouple probes used to monitor the temperatures of each modem are located on top of the analog section. This paper presents the results of the estimation of time delay change with temperature difference between the modem in MES and a modem in the USNO TS earth station control room.
Published in:	Proceedings of the 29th Annual Precise Time and Time Interval Systems and Applications Meeting December 2 - 4, 1997 Sheraton Long Beach Hotel Long Beach, California
Pages:	265 - 268
Cite this article:	Mai, Phu, DeYoung, James, "Time Delay Changes With Temperature in a TWSTT Monitoring System," Proceedings of the 29th Annual Precise Time and Time Interval Systems and Applications Meeting, Long Beach, California, December 1997, pp. 265-268.
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