1993
DOI: 10.1086/133188
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Signal-to-noise ratios in IUE low-dispersion spectra. II - Photometrically corrected images

Abstract: The character of detector noise is explored in photometrically corrected images from the short-wavelength and long-wavelength prime intensified vidicon cameras of the International Ultraviolet Explorer A protocol is proposed for deriving realistic "noise models"-crucial to the application of Optimal extraction algorithms like that of Kinney, Bohlin, and Neill (1991, PASP, 103, 694)-from the available collections of UV-Flood calibration images. The protocol includes evaluation of the "noise-filtering" propertie… Show more

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Cited by 12 publications
(13 citation statements)
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“…Since IUE was in high earth orbit, part of the output signal was due to particle background, as well as to a pedestal of read noise. Consequently, the maximum S/N possible for a single pixel was ∼ 10 : 1 (see Ayers 1993 for a more thorough discussion). Since a low dispersion spectrum typically had a full width perpendicular to the dispersion of about 3 pixels, the maximum S/N of a spectral pixel was ∼ √ 3 × 10 or ≃ 17 : 1.…”
Section: Overviewmentioning
confidence: 99%
“…Since IUE was in high earth orbit, part of the output signal was due to particle background, as well as to a pedestal of read noise. Consequently, the maximum S/N possible for a single pixel was ∼ 10 : 1 (see Ayers 1993 for a more thorough discussion). Since a low dispersion spectrum typically had a full width perpendicular to the dispersion of about 3 pixels, the maximum S/N of a spectral pixel was ∼ √ 3 × 10 or ≃ 17 : 1.…”
Section: Overviewmentioning
confidence: 99%
“…5); and (3) the ITF DN to FN conversion is represented by a fourth-order polynomial (rather than the linear interpolation used in NEWSIPS). As Ayres (1993) has discussed, the lack of an explicit registration of the science image and ITF fixed patterns should have Fig. 3.…”
Section: Introductionmentioning
confidence: 99%
“…However, the NEWSIPS approach should be more effective for those (significant numbers of ) images taken at camera temperatures more than a few degrees from the nominal. Ayres also has derived an empirical noise model for IUE data based on an analysis of the ITF image sets (SWP and LWP only), including two-dimensional Fourier power-spectrum tests to evaluate the effective smoothing imposed on the vidicon images at different positions (Ayres 1993). When the latter was taken into account, Ayres concluded the rms noise characteristics are roughly independent of position on the camera.…”
Section: Introductionmentioning
confidence: 99%
“…While that defect is remedied in the NEWSIES software, such information is not yet available for LW-HI data. NEWSIPS-like schemes, with reahstic "noise models," have been implemented for SWP-LO (e.g., Ayres 1993;Ayres et al 1995) and for SWP-HI (e.g, Ayres et al 1993; but, again, are not yet available for LW-HI. Therefore we have adopted a straightforward scheme to assign errors to our lUESIPS-processed spectra.…”
Section: No 1 1996mentioning
confidence: 99%
“…In the presence of significant morphological profile variations, the method overestimates the photometric noise. In the empirical "calibration" of the noise model, we compensated for any prior smoothing of the (oversampled) profiles and for the intrinsic spatialaveraging properties of the detectors (see discussion in Ayres 1993). The 1 a errors fisted in Tables 2-8 represent these photometric noise estimates, augmented (in quadrature) when necessary by the uncertainty in the flux calibration of those images processed with LWPITF1.…”
Section: No 1 1996mentioning
confidence: 99%