IRAS Explanatory Supplement
XI. Known Processing Anomalies
B. Instability and Lag of Noise Estimator
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The noise estimator (Section V.C.2) was picked for its computational speed and its Performance in quiet areas of the sky. It performed poorly in regions of rapidly changing noise amplitude. As a result, the noise estimator near regions of high source density was a major reason for incompleteness for sources that would properly have had a signal-to-noise ratio of three or more because the estimator erroneously increased the noise level so that the computed signal-to-noise ratio fell below the threshold. Furthermore, the noise estimator exhibited a lag which resulted in the almost complete excision of sources within a degree or two on one side of the Galactic plane.
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