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Proceedings Paper

On-Board Correction Of Systematic Errors Of Ir Horizon Sensors Due To Seasonal Changes Of Radiance In 15 Microns Band
Author(s): T K Alex; S K Srivastava
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Paper Abstract

Earth sensors working on the principle of detection of infrared discontinuity at the horizon are affected by systematic errors due to seasonal changes in radiance. Horizon Crossing Sensors used in spinning satellites, conical scanning or oscillatory types of sensors which find application in three-axis stabilized satellites are generally susceptible to this type of error. The method currently in use involves post-facto corrections by ground based modelling of the radiance which is a function of seasons, latitude and longitude. The latest trend is towards using 'Smart Sensors' with an ability to correct the errors on-board itself. This paper presents an algorithm developed for correcting the systematic error due to radiance changes, on-board the satellite. In this new approach, a relation between systematic errors and radiance gradient between two horizon points is established. The method of sensing the radiance and computing the gradient on-board the spacecraft and a simple correction algorithm which is suitable for implementation by microprocessors have also been derived. Typically, the maximum error due to gradient in radiance is 0.05 degree and it depends upon the type of orbit. The results of the correction algorithm applicable to a typical conical scanning earth sensor for a sun-synchronous, 3 - axis stabilized satellite are included in the paper. The systematic error is reduced to less than 0.01 degree. This is comparable with that from ground based computation which involves the determination of satellite position in orbit and the use of atmospheric models based on large observational data base.

Paper Details

Date Published: 10 August 1988
PDF: 6 pages
Proc. SPIE 0926, Optical, Infrared, Millimeter Wave Propagation Engineering, (10 August 1988); doi: 10.1117/12.945782
Show Author Affiliations
T K Alex, ISRO Satellite Centre (India)
S K Srivastava, Indian Institute of Science (India)

Published in SPIE Proceedings Vol. 0926:
Optical, Infrared, Millimeter Wave Propagation Engineering
Norman S. Kopeika; Walter B. Miller, Editor(s)

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