AAS 98-117

ESTIMATION OF RADAR ORIENTATION, LOCATION AND OTHER CALIBRATION PARAMETERS USING REGULARIZED RESIDUALS

M. F. Storz - Falcon AFB Space Warfare Center

Abstract

Calibration of space surveillance radars to remove systematic biases is a cost-effective way to improve metric observation accuracy, leading to more accurate satellite orbit determination. Radar calibration can be performed more effectively today because of the many available reference orbits with sub-meter accuracy. CALIBRE, described in this paper, is a new software program that simultaneously estimates the values and covariances for the following bias parameters: sensor location, sensor clock bias, sensor orientation, isotropic range and range rate biases, and an ionospheric bias. CALIBRE transforms look angle (azimuth/elevation) residuals and look angle rate residuals into a localized angular coordinate frame that removes the geometric distortions that arise near the zenith. These regularized residuals lead to better least squares estimates. Range (and its rate and acceleration) observations are also used as input. Look angle biases are estimated as a single rigid-body rotation of the sensor axes, a method more physically realistic than the common practice of estimating a bias in azimuth and a bias in elevation as decoupled parameters. Operational application of CALIBRE promises to provide significant improvements in the metric calibration of space surveillance radars and the resulting orbital accuracy.

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