arXiv subjects

Thibaut Prod'homme

Publications and source records attributed to Thibaut Prod'homme.

11 recordsLinked to original sources

arXiv2024

PLATO's signal and noise budget

ESA's PLATO mission aims the detection and characterization of terrestrial planets around solar-type stars as well as the study of host star properties. The noise-to-signal ratio (NSR) is the main performance parameter of the PLATO instrument, which consists of 24 Normal Cameras and 2 Fast Cameras. In order to justify, verify and breakdown NSR-relevant requirements the software simulator PINE was developed. PINE models the signal pathway from a target star to the digital output of a camera based on physical models and considers the major noise contributors. In this paper, the simulator's coarse mode is introduced which allows fast performance analyses on instrument level. The added value of PINE is illustrated by exemplary applications.

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arXiv2023

The ESO's Extremely Large Telescope Working Groups

Since 2005 ESO has been working with its community and industry to develop an extremely large optical/infrared telescope. ESO's Extremely Large Telescope, or ELT for short, is a revolutionary ground-based telescope that will have a 39-metre main mirror and will be the largest visible and infrared light telescope in the world. To address specific topics that are needed for the science operations and calibrations of the telescope, thirteen specific working groups were created to coordinate the effort between ESO, the instrument consortia, and the wider community. We describe here the goals of these working groups as well as their achievements so far.

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arXiv2021

The Infra-Red Telescope (IRT) on board the THESEUS mission

The Infra-Red Telescope (IRT) is part of the payload of the THESEUS mission, which is one of the two ESA M5 candidates within the Cosmic Vision program, planned for launch in 2032. The THESEUS payload, composed by two high energy wide field monitors (SXI and XGIS) and a near infra-red telescope (IRT), is optimized to detect, localize and characterize Gamma-Ray Bursts and other high-energy transients. The main goal of the IRT is to identify and precisely localize the NIR counterparts of the high-energy sources and to measure their distance. Here we present the design of the IRT and its expected performance.

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arXiv2020

Pyxel: the collaborative detection simulation framework

Pyxel is a novel python tool for end-to-end detection chain simulation i.e. from detector optical effects to readout electronics effects. It is an easy-to-use framework to host and pipeline any detector effect model. It is suited for simulating both Charge-Coupled Devices, CMOS Image Sensors and Mercury Cadmium Telluride hybridized arrays. It is conceived as a collaborative tool to promote reusability, knowledge transfer, and reliability in the instrumentation community. We provide a demonstration of Pyxel's basic principles, describe newly added capabilities, and give examples of more advanced applications.

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arXiv2020

A smartphone-based arbitrary scene projector for detector testing and instrument performance evaluation

Using the high-resolution OLED screen of a smartphone to project arbitrary scenes and patterns can open a complete new dimension for testing sensors in the visible. Based on an original concept from JPL (Jet Propulsion Laboratory), this contribution describes a new experimental setup designed to achieve the demanding performance of its first application by ESA (European Space Agency): the evaluation of radiation-induced CTI (Charge Transfer Inefficiency) on Euclid's weak lensing measurement. We show that pushed to its limits especially in terms of calibration such a simple experiment can deliver a level of optical performance high enough to be applied in the verification of high-precision astronomy instrument performance.

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arXiv2017

Comparing simulations and test data of a radiation damaged charge-couple device for the Euclid mission

The VIS instrument on board the Euclid mission is a weak-lensing experiment that depends on very precise shape measurements of distant galaxies obtained by a large CCD array. Due to the harsh radiative environment outside the Earth's atmosphere, it is anticipated that the CCDs over the mission lifetime will be degraded to an extent that these measurements will only be possible through the correction of radiation damage effects. We have therefore created a Monte Carlo model that simulates the physical processes taking place when transferring signal through a radiation-damaged CCD. The software is based on Shockley-Read-Hall theory, and is made to mimic the physical properties in the CCD as closely as possible. The code runs on a single electrode level and takes three dimensional trap position, potential structure of the pixel, and multi-level clocking into account. A key element of the model is that it also takes device specific simulations of electron density as a direct input, thereby avoiding to make any analytical assumptions about the size and density of the charge cloud. This paper illustrates how test data and simulated data can be compared in order to further our understanding of the positions and properties of the individual radiation-induced traps.

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arXiv2016

Radiation effects on the Gaia CCDs after 30 months at L2

Since the launch of ESA's Gaia satellite in December 2013, the 106 large-format scientific CCDs onboard have been operating at L2. Due to a combination of the high-precision measurement requirements of the mission and the predicted proton environment at L2, the effect of non-ionizing radiation damage on the detectors was early identified pre-launch as potentially imposing a major limitation on the scientific value of the data. In this paper we compare pre-flight radiation-induced Charge Transfer Inefficiency (CTI) predictions against in-flight measurements, focusing especially on charge injection diagnostics, as well as correlating these CTI diagnostic results with solar proton event data. We show that L2-directed solar activity has been relatively low since launch, and radiation damage (so far) is less than originally expected. Despite this, there are clear cases of correlation between earth-directed solar coronal mass ejection events and abrupt changes in CTI diagnostics over time. These sudden jumps are lying on top of a rather constant increase in CTI which we show is primarily due to the continuous bombardment of the devices by high-energy Galactic Cosmic Rays. We examine the possible reasons for the lower than expected levels of CTI as well as examining the effect of controlled payload heating events on the CTI diagnostics. Radiation-induced CTI in the CCD serial registers and effects of ionizing radiation are also correspondingly lower than expected, however these topics are not examined here in detail.

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arXiv2015

How well can Charge Transfer Inefficiency be corrected? A parameter sensitivity study for iterative correction

Radiation damage to space-based Charge-Coupled Device (CCD) detectors creates defects which result in an increasing Charge Transfer Inefficiency (CTI) that causes spurious image trailing. Most of the trailing can be corrected during post-processing, by modelling the charge trapping and moving electrons back to where they belong. However, such correction is not perfect -- and damage is continuing to accumulate in orbit. To aid future development, we quantify the limitations of current approaches, and determine where imperfect knowledge of model parameters most degrade measurements of photometry and morphology. As a concrete application, we simulate $1.5\times10^{9}$ "worst case" galaxy and $1.5\times10^{8}$ star images to test the performance of the Euclid visual instrument detectors. There are two separable challenges: If the model used to correct CTI is perfectly the same as that used to add CTI, $99.68$ % of spurious ellipticity is corrected in our setup. This is because readout noise is not subject to CTI, but gets over-corrected during correction. Second, if we assume the first issue to be solved, knowledge of the charge trap density within $Δρ/ρ\!=\!(0.0272\pm0.0005)$ %, and the characteristic release time of the dominant species to be known within $Δτ/τ\!=\!(0.0400\pm0.0004)$ % will be required. This work presents the next level of definition of in-orbit CTI calibration procedures for Euclid.

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arXiv2014

An improved model of Charge Transfer Inefficiency and correction algorithm for the Hubble Space Telescope

Charge-Coupled Device (CCD) detectors, widely used to obtain digital imaging, can be damaged by high energy radiation. Degraded images appear blurred, because of an effect known as Charge Transfer Inefficiency (CTI), which trails bright objects as the image is read out. It is often possible to correct most of the trailing during post-processing, by moving flux back to where it belongs. We compare several popular algorithms for this: quantifying the effect of their physical assumptions and tradeoffs between speed and accuracy. We combine their best elements to construct a more accurate model of damaged CCDs in the Hubble Space Telescope's Advanced Camera for Surveys/Wide Field Channel, and update it using data up to early 2013. Our algorithm now corrects 98% of CTI trailing in science exposures, a substantial improvement over previous work. Further progress will be fundamentally limited by the presence of read noise. Read noise is added after charge transfer so does not get trailed - but it is incorrectly untrailed during post-processing.

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arXiv2013

An Analytical Model of Radiation-Induced Charge Transfer Inefficiency for CCD Detectors

The European Space Agency's Gaia mission is scheduled for launch in 2013. It will operate at L2 for 5 years, rotating slowly to scan the sky so that its two optical telescopes will repeatedly observe more than one billion stars. The resulting data set will be iteratively reduced to solve for the position, parallax and proper motion of every observed star. The focal plane contains 106 large area silicon CCDs continuously operating in a mode where the line transfer rate and the satellite rotation are in synchronisation. One of the greatest challenges facing the mission is radiation damage to the CCDs which will cause charge deferral and image shape distortion. This is particularly important because of the extreme accuracy requirements of the mission. Despite steps taken at hardware level to minimise the effects of radiation, the residual distortion will need to be calibrated during the pipeline data processing. Due to the volume and inhomogeneity of data involved, this requires a model which describes the effects of the radiation damage which is physically realistic, yet fast enough to implement in the pipeline. The resulting charge distortion model was developed specifically for the Gaia CCD operating mode. However, a generalised version is presented in this paper and this has already been applied in a broader context, for example to investigate the impact of radiation damage on the Euclid dark-energy mission data.

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arXiv2011

The impact of CCD radiation damage on Gaia astrometry: I. Image location estimation in the presence of radiation damage

The Gaia mission has been designed to perform absolute astrometric measurements with unprecedented accuracy; the end-of-mission parallax standard error is required to be 30 micro-arcseconds for a G2V type star of magnitude 15. These requirements set a stringent constraint on the accuracy of the estimation of the location of the stellar image on the CCD for each observation: e.g., 0.3 milli-arseconds (mas) or 0.005 pixels for the same V=15 G2V star. However the Gaia CCDs will suffer from charge transfer inefficiency (CTI) caused by radiation damage that will degrade the stellar image quality and may degrade the astrometric performance of Gaia if not properly addressed. For the first time at this level of detail, the potential impact of radiation damage on the performance of Gaia is investigated. In this first paper we focus on the evaluation of the CTI impact on the image location accuracy. We show that CTI decreases the stellar image signal-to-noise ratio and irreversibly degrades the image location estimation precision. As a consequence the location estimation standard errors increase by up to 6% for a radiation damage level equivalent to the end-of-mission. In addition the CTI-induced image distortion introduces a systematic bias in the image location estimation (up to 0.05 pixels or 3 mas in the Gaia operating conditions). We present a novel approach to CTI mitigation that enables, without correction of the raw data, the unbiased estimation of the image location and flux from damaged observations. Its implementation reduces the maximum measured location bias for the faintest magnitude to 0.005 pixels (~4e-4 pixels at magnitude 15). In a second paper we will investigate how the CTI effects affect the final astrometric accuracy of Gaia by propagating residual errors through the astrometric solution.

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