An analytical model of radiation-induced Charge Transfer Inefficiency for CCD detectors

Short, A.; Crowley, C.; Bruijne, J. H. J. de; Prod’homme, Thibaut

doi:10.1093/mnras/stt114

Cited by 44 publications

(61 citation statements)

References 9 publications

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“…Traps, in combination with TDI operation, affect the detailed shape of the point spread function of all instruments in subtle yet significant ways through continuous trapping and de-trapping (Holl et al 2012b;Prod'homme et al 2012), removing charge from the leading edge and releasing it in the trailing edge of the images and spectra. The resulting systematic biases of the image centroids and the spectra will be calibrated in the onground data processing, for instance using a forward-modelling approach based on a charge-distortion model (CDM; Short et al 2013). The CCDs are passively cooled to 163 K to reduce dark current and minimise (radiation-induced) along-and across-scan CTI.…”

Section: Focal Plane Assemblymentioning

confidence: 99%

TheGaiamission

Prusti¹,

Bruijne²,

Brown³

et al. 2016

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Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.

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Section: Focal Plane Assemblymentioning

confidence: 99%

TheGaiamission

Prusti¹,

Bruijne²,

Brown³

et al. 2016

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“…Currently the acquired data is used to monitor the evolution of the CTI; however, the baseline for data processing is to use these data to calibrate a semi-physical CTI model (e.g. Short et al 2013) and to treat the raw images with this forward-model in later iterations of the data processing.…”

Section: Cti In the Serial Register (Ac Direction)mentioning

confidence: 99%

GaiaData Release 1

Crowley

Kohley

Hambly

et al. 2016

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The European Space Agency's Gaia satellite was launched into orbit around L2 in December 2013 with a payload containing 106 large-format scientific CCDs. The primary goal of the mission is to repeatedly obtain high-precision astrometric and photometric measurements of one thousand million stars over the course of five years. The scientific value of the down-linked data, and the operation of the onboard autonomous detection chain, relies on the high performance of the detectors. As Gaia slowly rotates and scans the sky, the CCDs are continuously operated in a mode where the line clock rate and the satellite rotation spin-rate are in synchronisation. Nominal mission operations began in July 2014 and the first data release is being prepared for release at the end of Summer 2016. In this paper we present an overview of the focal plane, the detector system, and strategies for on-orbit performance monitoring of the system. This is followed by a presentation of the performance results based on analysis of data acquired during a two-year window beginning at payload switch-on. Results for parameters such as readout noise and electronic offset behaviour are presented and we pay particular attention to the effects of the L2 radiation environment on the devices. The radiation-induced degradation in the charge transfer efficiency (CTE) in the (parallel) scan direction is clearly diagnosed; however, an extrapolation shows that charge transfer inefficiency (CTI) effects at end of mission will be approximately an order of magnitude less than predicted pre-flight. It is shown that the CTI in the serial register (horizontal direction) is still dominated by the traps inherent to the manufacturing process and that the radiation-induced degradation so far is only a few per cent. We also present results on the tracking of ionising radiation damage and hot pixel evolution. Finally, we summarise some of the detector effects discovered on-orbit which are still being investigated.

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“…Previous studies have modelled the resulting function through the use of a power law [37], such that the volume occupied varies with signal to the power β. In our own studies, however, we propose the use of an additional parameter to describe the specific behaviour observed at lower signal levels, Equation 5, where α, β and ɣ are all constants that will vary from one trap species and dwell time to another.…”

Section: Charge Storage Geometrymentioning

confidence: 99%

Challenges in photon-starved space astronomy in a harsh radiation environment using CCDs

et al. 2015

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The Charge Coupled Device (CCD) has a long heritage for imaging and spectroscopy in many space astronomy missions. However, the harsh radiation environment experienced in orbit creates defects in the silicon that capture the signal being transferred through the CCD. This radiation damage has a detrimental impact on the detector performance and requires carefully planned mitigation strategies.The ESA Gaia mission uses 106 CCDs, now orbiting around the second Lagrange point as part of the largest focal-plane ever launched. Following readout, signal electrons will be affected by the traps generated in the devices from the radiation environment and this degradation will be corrected for using a charge distortion model. ESA's Euclid mission will contain a focal plane of 36 CCDs in the VIS instrument. Moving further forwards, the World Space Observatory (WSO) UV spectrographs and the WFIRST-AFTA coronagraph intend to look at very faint sources in which mitigating the impact of traps on the transfer of single electron signals will be of great interest.Following the development of novel experimental and analysis techniques, one is now able to study the impact of radiation on the detector to new levels of detail. Through a combination of TCAD simulations, defect studies and device testing, we are now probing the interaction of single electrons with individual radiation-induced traps to analyse the impact of radiation in photon-starved applications.

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An analytical model of radiation-induced Charge Transfer Inefficiency for CCD detectors

Cited by 44 publications

References 9 publications

TheGaiamission

TheGaiamission

GaiaData Release 1

Challenges in photon-starved space astronomy in a harsh radiation environment using CCDs

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