Front- vs. back-illuminated CCD cameras for photometric surveys: a noise budget analysis

TL;DR

This paper analyzes noise sources in CCD cameras for high-precision photometry, comparing front- and back-illuminated CCDs, and provides guidelines for optimizing PSF size and aperture to minimize instrumental noise.

Contribution

It introduces a semi-analytical noise model and compares CCD types through simulations, guiding instrument choice for photometric surveys.

Findings

Gaussian PSF > 1.6 pixels reduces electrode noise

Photometric aperture should be ≥2.5× PSF FWHM for small PSF

Front-illuminated CCDs are preferred for the A STEP project

Abstract

Exoplanetary transit and stellar oscillation surveys require a very high precision photometry. The instrumental noise has therefore to be minimized. First, we perform a semi-analytical model of different noise sources. We show that the noise due the CCD electrodes can be overcome using a Gaussian PSF (Point Spread Function) of full width half maximum larger than 1.6 pixels. We also find that for a PSF size of a few pixels, the photometric aperture has to be at least 2.5 times larger than the PSF full width half maximum. Then, we compare a front- with a back-illuminated CCD through a Monte-Carlo simulation. Both cameras give the same results for a PSF full width half maximum larger than 1.5 pixels. All these simulations are applied to the A STEP (Antarctica Search for Transiting Extrasolar Planets) project. As a result, we choose a front-illuminated camera for A STEP because of its better resolution and lower price, and we will use a PSF larger than 1.6 pixels.