IRAS Explanatory Supplement
V. Data Reduction
D. Point Source Confirmation
D.2 Overview of Seconds-Confirmation
D.2.j In-Band Seconds-Confirmation Statistical Processing
Table of Contents | Index | Previous Section | Next Section
When detections were found to be confirmable in the absence of confusion, saturation, effects due to failed or noisy detectors, fluxes which did not qualify for refinement, or occurrence of the detections exclusively at the boundary of the survey detector array area in the focal plane, then the discrepancies in the in-scan position angle and the flux were computed for statistical analysis. The values and significances of these were used to adjust and then verify the a priori error variance models.
In each band the relative flux discrepancy standard deviation as a function of signal-to-noise ratio was computed. The mean discrepancy was not significantly different from zero, and typical standard deviations ran from 20% for weak sources to about 10% in the 12 µm band 15% in the 25 µm band and 20% in the 60 and 100 µm bands for bright sources. These standard deviations were used to examine the behavior of the photometric error at the sampling intervals involved. After about 30 days of data had been accumulated the variances obtained in this way were used to supply new a prior flux error variances for the rest of the mission. It was not necessary to cycle subsequent results through this process again, i.e., the statistical properties of the photometric discrepancies sampled at intervals of a few seconds and a few hours (from similar analysis at hours-confirmation) were stable over the lifetime of the space-craft.
Table of Contents | Index | Previous Section | Next Section