On the extraction of extended structure from Herschel-SPIRE scanning observations in the presence of 1/f noise

We present results from a study of the impact of uncorrelated 1/ f noise on the extraction of spatial structure, on a range of scales, from sky mapping observations made using the Herschel-SPIRE (the spectral and photometric imaging receiver) photometer in the scan-map mode. These studies were carried out using a detailed instrument simulator, and the output reduced using the map-making algorithm to be implemented in the SPIRE data pipeline. The influence of source size scale, telescope-scanning rate and 1/ f noise knee frequency is investigated, and operational bounds to the expected losses are presented, using the case of zero 1/ f (white) noise as a benchmark. Both cross-linked and non-cross-linked observing options are studied. The results presented here represent the best current estimate of the sensitivity of the SPIRE photometer to emission on arbitrary scales. The data presented are general and scalable to any SPIRE observation made using the scanning mode.     

measurement of noise power spectrum in photon counting PMT's and the effect of the observed (1/f) noise on astronomical photometry

In astronomical photometry, the sensitivity of observations is limited by the dark counts of the photomultiplier tube. In the present work, the effect of dark count noise in photon counting systems is investigated by theory and experimental measurements. Dark counts are considered to be originating from two sources, namely: dc fluctuations and random pulses.Experimental measurements were carried out to determine noise effects in different operating regions of noise dominance. The results provide strong evidence that: in normal operating mode, where the effect of random pulses is dominant, dark counts do not follow Poisson statistics. The observed noise shows strong (1/f) power spectrum, where the observed noise power is found to increase with time of observation.The results are important in photon counting systems operating under dark count limited mode. The conclusions drawn can be useful in obtaining more accurate error estimates and in assessing astronomical photometric observations and data reduction techniques.