NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
(abstract) Tropospheric Calibration for the Mars Observer Gravity Wave ExperimentIn spring 1993, microwave radiometer-based tropospheric calibration was provided for the Mars Observer gravitational wave search. The Doppler shifted X-band radio signals propagating between Earth and the Mars Observer satellite were precisely measured to determine path length variations that might signal passage of gravitational waves. Experimental sensitivity was restricted by competing sources of variability in signal transit time. Principally, fluctuations in the solar wind and ionospheric plasma density combined with fluctions in tropospheric refractivity determined the detection limit. Troposphere-induced path delay fluctions are dominated by refractive changes caused by water vapor inhomogeneities blowing through the signal path. Since passive microwave remote sensing techniques are able to determine atmospheric propagation delays, radiometer-based tropospheric calibration was provided at the Deep Space Network Uranus tracking site (DSS-15). Two microwave water vapor radiometers (WVRs), a microwave temperature profiler (MTP), and a ground based meterological station were deployed to determine line-of-sight vapor content and vertical temperature profile concurrently with Mars Observer tracking measurements. This calibration system provided the capability to correct Mars Observer Doppler data for troposphere-induced path variations. We present preliminary analysis of the Doppler and WVR data sets illustrating the utility of WVRs to calibrate Doppler data. This takes an important step toward realizing the ambitious system required to support future Ka-band Cassini satellite gravity wave tropospheric calibration system.
Document ID
20060039465
Document Type
Preprint (Draft being sent to journal)
External Source(s)
Authors
Walter, Steven J.
Armstrong, John
Date Acquired
August 23, 2013
Publication Date
January 5, 1994
Subject Category
Lunar and Planetary Science and Exploration
Distribution Limits
Public
Copyright
Other
Keywords
atmospheric water vapor microwave remote sensing
tropospheric calibration radiometer gravity wave experiment Mars Observer