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Abstract: Abridged We examine the effects of charge transfer inefficiency CTIduring CCD readout on galaxy shape measurements required by studies of weakgravitational lensing. We simulate a CCD readout with CTI such as that causedby charged particle radiation damage. We verify our simulations on data fromlaboratory-irradiated CCDs. Only charge traps with time constants of the sameorder as the time between row transfers during readout affect galaxy shapemeasurements. We characterize the effects of CTI on various galaxy populations.We baseline our study around p-channel CCDs that have been shown to have chargetransfer efficiency up to an order of magnitude better than several models ofn-channel CCDs designed for space applications. We predict that for galaxiesfurthest from the readout registers, bias in the measurement of galaxy shapes,Deltae, will increase at a rate of 2.65 +- 0.02 x 10^-4 per year at L2 foraccumulated radiation exposure averaged over the solar cycle. If uncorrected,this will consume the entire shape measurement error budget of a dark energymission within about 4 years. Software mitigation techniques demonstratedelsewhere can reduce this by a factor of ~10, bringing the effect well belowmission requirements. CCDs with higher CTI than the ones we studeied may notmeet the requirements of future dark energy missions. We discuss ways in whichhardware could be designed to further minimize the impact of CTI.



Author: Jason Rhodes, Alexie Leauthaud, Chris Stoughton, Richard Massey, Kyle Dawson, William Kolbe, Natalie Roe

Source: https://arxiv.org/







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