ESA’s Science Payload Validation laboratory is characterising Leonardo’s IBEX detector. IBEX is new 2kx2k pixels MCT-hybridised detector that relies on avalanche photo-diode to provide effective sub-electron readout noise capabilities and low enough dark current compatible with long integration duration typical of photon-starved astronomy applications. In this contribution, we provide first an overview of the packaging solution and test setups including our custom readout chain and prototype controller. We then report on functional and performance test results for a bare-ROIC as well as early dark current performance for the hybridised arrays.
ESA’s Science Payload Validation laboratory is developing a new type of detector characterisation bench, designed to cope with new challenges set by future instrument requirements and newly developed detectors. This new bench can accommodate large format detector up to 4kx4k 10um pitch or at least two 2kx2k 15um pitch side by side, it enables measurement in the 300 to 4000nm wavelength range, and can bring the detector temperature down to 20K. Its concept, based on lessons learned accumulated over the last 10 years, enables light and dark measurements to be performed in a single configuration reducing handling and optimising testing time in test campaigns. This contribution provides a general overview of the bench concept and main features. It details the main design challenges and describes the corresponding opto-mechanical and thermal design solutions, validated by early commissioning results.
Under an ESA contract, Leonardo UK developed the IBEX detector also referred to as LAPD for Large-format Avalanche Photo Diode array. Leonardo’s packaging solution relied on a chip-on-board solution incompatible with technical and performance requirements of ESA characterization campaign and experimental setup. An in-house solution has been developed, with ESA responsible for the design, manufacture, and test. And Leonardo responsible for gluing the device to the carrier and the wire bonding. ESA’s packaging solution relies on molybdenum carrier and two flexible PCB cables. The design, manufacturing, testing, and assembling of the various components of the LAPD package assembly entailed a variety of design iterations, tests, and trials. The material choice was a compromise between optimal CTE mismatch of Invar 36 and excellent thermal conductivity of TZM molybdenum (TZM = 0.5% titanium, 0.08% zirconium, 0.02% carbon). TZM molybdenum was chosen, and it was decided to verify the behavior by test. A thermal-vacuum test campaign showed that a mounted ROIC survives test representative conditions i.e., various thermal cycles between 20 and 200K. The gold coating of the molybdenum carrier is a real challenge, we will report on lessons learned. Similarly, the flexible PCB cables gluing to the carrier performed in-house is a delicate exercise. The flex cables are bonded to molybdenum blocks which are permanently mounted in a recess in the back of the carrier. Several trials were done for the mounting until successful result was reached. A sequence of thermal cycles between 20 and 200K were performed and showed no evidence of failure throughout the bond line between the block and flex cable. A handling jig was designed to fit Leonardo’s bonding setups for the die mounting and wire bonding. The handling jig is also used to safely mount the device in an in-house designed transportation and storage container.
KEYWORDS: Video, Clocks, Power supplies, Field programmable gate arrays, Readout integrated circuits, Analog to digital converters, CMOS sensors, Optical proximity correction, Quantum reading, Microcontrollers
ESA’s Science Payload Validation laboratory is responsible for the characterization of detectors (CCDs, CMOS, MCT hybridised arrays, etc.) under technology development or foreseen to be used in ESA’s science missions. In this context, the ESA’s Science Payload Validation laboratory has developed COMODOR (ESA’s COntroller for cMOs DetectOR), a new modular CMOS controller focused on controlling and reading out new and future large format infrared and visible CMOS imaging sensors. A prototype for COMODOR has been developed and is currently in use to characterize Leonardo’s IBEX 2k x 2k pixels MCT-hybridised detector. To achieve such a goal, COMODOR is based on a modular architecture which contains a Xilinx PCIe FPGA Video card to readout the detector and to reconstruct the images, a PCIe Timing Card to drive the timing clocks and control the detector, an in-house Front End-Electronic Video board which accommodates ADCs to sample analogue video channels and Power Supply boards to provide low-noise power supplies for the analogue chain and to the detector. The entire system is under the control of a dedicated Linux computer. In this contribution we give an overview of the architecture, a description of key elements, and provide a first report on functionality and performance testing activities. We also provide an outlook of the next improvements and corresponding challenges.
Detectors are very often a performance-limiting component for space instrumentation – the better the detector, the better the instrument performance. Consequently, the European Space Agency (ESA) invests significant resources into the development of high-performance detector solutions for current and future missions. While technology developments span the full electromagnetic spectrum, infrared (and visible) wavebands are of particular interest and this paper presents a detailed overview of infrared detector development activities currently being undertaken by ESA in collaboration with European industrial partners.
With CMOS sensors starting to be utilised in astronomical telescopes, new uses for them are being explored. One such use is the possibility of observing distant, dim objects, which requires long integration times, and therefore low dark current. This work focuses on the dark current characterisation of the CIS220, a sensor made by Teledyne e2v for future space missions, at very long integration times at a range of temperatures, from +20 to –60 °C, before and after proton and gamma irradiation.
Pyxel is an opensource python-based framework to simulate images including instrumental effects with a focus on detector modelling (CCDs & EM-CCDS, CIS, Hybrid-CMOS, APDs, MKIDs etc.). Right from the start of its development at ESA, Pyxel has been conceived to easily integrate and pipeline models from different contributors and in this way foster collaboration in the instrumentation community. We give an overview of the framework focusing on the main improvements and evolution since v1.0 and examples of new features. On top of the many models that were added to the framework, the pipeline hosts now to two new model groups “scene generation” and “data processing” to make the framework even more self-consistent.
In November 2022, the ESA Science Programme Committee (SPC) selected ARRAKIHS as the second Fastimplementation mission (F2) within the Agency’s Scientific Programme, with a launch planned in 2030. ARRAKIHS is designed specifically to explore, at unprecedented depth, the predictions of the Λ-Cold Dark Matter (ΛCDM) cosmological model, and to assess the significance of reported tensions between model and observations in the local Universe. Through multi-band, ultra-low surface brightness imaging of the halos of a statistically representative sample of nearby Milky Waytype galaxies, ARRAKIHS will provide key tests with which to probe both the nature of Dark Matter in the Universe, and baryonic physics currently adopted in state-of-the-art galaxy formation models. This paper describes the ARRAKIHS mission concept and the main design and implementation challenges.
CIS221-X is a prototype complementary metal-oxide-semiconductor (CMOS) image sensor, optimized for soft x-ray astronomy and developed for the proposed ESA Transient High Energy Sky and Early Universe Surveyor (THESEUS) mission. The sensor features 40 μm pitch square pixels built on a 35 μm thick, high-resistivity epitaxial silicon that is fully depleted by reverse substrate bias. Backside illumination processing has been used to achieve high x-ray quantum efficiency, and an optical light-blocking filter has been applied to mitigate the influence of stray light. A comprehensive electro-optical characterization of CIS221-X has been completed. The median readout noise is 3.3 e − RMS with 90% of pixels reporting a value <3.6 e − RMS. At −40 ° C, the dark current is 12.4 ± 0.06 e − / pixel / s. The pixel photo-response is linear to within 1% for 0.3 to 5 keV photons (82 to 1370 e − ) with <0.1 % image lag. Following per-pixel gain correction, an energy resolution of 130.2 ± 0.4 eV has been measured at 5898 eV. In the 0.3 to 1.8 keV energy range, CIS221-X achieves >80 % quantum efficiency. With the exception of dark current, these results either meet or outperform the requirements for the THESEUS mission, strongly supporting the consideration of CMOS technology for soft x-ray astronomy.
Detector modeling is becoming more and more critical for the development of new instruments in scientific space missions and ground-based experiments. Modeling tools are often developed from scratch by each individual project and not necessarily shared for reuse by a wider community. To foster knowledge transfer, reusability, and reliability in the instrumentation community, we developed Pyxel, a framework for the simulation of scientific detectors and instruments. Pyxel is an open-source and collaborative project, based on Python, developed as an easy-to-use tool that can host and pipeline any kind of detector effect model. Recently, Pyxel has achieved a new milestone: the public release and launch of version 1.0, which simplified third-party contributions and improved ease of use even further. Since its launch, Pyxel has been experiencing a growing user community and is being used to simulate a variety of detectors. We give a tour of Pyxel’s version 1.0 changes and new features, including a new interface, parallel computing, and new detectors and models. We continue with an example of using Pyxel as a tool for model optimization and calibration. Finally, we describe an example of how Pyxel and its features can be used to develop a full-scale end-to-end instrument simulator.
Peter Verhoeve, Sander Blommaert, Dennis Breeveld, Joerg ter Haar, Kate Isaak, Frederic Lemmel, Cornelis van der Luijt, Thibaut Prod'homme, Hans Smit, Brian Shortt, Ivo Visser, Attila Simon, Andrea Fortier, Christopher Broeg
The CCD47-20 detector of CHEOPS (CHaracterizing ExOPlanet Satellite, ESA/Switzerland), operated at -45°C, is developing an increasing number of hot pixels in orbit, due to particle-induced radiation damage in its 700 km, sun-synchronous dawn/dusk orbit. While the satellite offers the possibility to raise the detector’s temperature to well above +20°C, it is not clear whether this could have a beneficial effect on the hot pixel distribution, and which temperature and duration would be required. To inform the mission on the potential benefits of in-orbit annealing, we irradiated CCD47-20s from the CHEOPS flight production batch at -45°C with protons. After irradiation, the hot pixels were monitored for 7 days at -45°C Subsequently, the temperature was raised step-wise (up to +80°C) for 12 hrs, each step followed by characterisation at -45°C. A significant reduction in the hot pixel count was observed at each step. A recommendation for a possible in-orbit annealing procedure was derived.
A monolithic CMOS image sensor based on the pinned photodiode (PPD) and optimized for X-ray imaging in the 300 eV to 5 keV energy range is described. Featuring 40 μm square pixels and 40 μm thick, high resistivity epitaxial silicon, the sensor is fully depleted by reverse substrate bias. Backside illumination (BSI) processing has been used to achieve high X-ray QE, and a dedicated pixel design has been developed for low image lag and high conversion gain. The sensor, called CIS221-X, is manufactured in a 180 nm CMOS process and has three different 512×128-pixel arrays on 40 μm pitch, as well as a 2048×512 array of 10 μm pixels. CIS221-X also features per-column 12-bit ADCs, digital readout via four highspeed LVDS outputs, and can be read out at 45 frames per second. CIS221-X achieves readout noise of 2.6 e- RMS and full width at half maximum (FWHM) at the Mn-Kα 5.9 keV characteristic X-ray line of 153 eV at -40 °C. This paper presents the characterization results of the first backside illuminated CIS221-X, including X-ray response and readout noise. The newly developed sensor and the technology underpinning it is intended for diverse applications, including Xray astronomy, synchrotron, and X-ray free electron laser light sources.
ESA’s Science Payload Validation section (SCI-FIV) is developing a new detector test bench to expand its existing suite of test facilities and enable the characterisation of larger detectors (4k x 4k 15 μm pitch devices), sensitive over the visible to mid-wave infrared wavelengths (300-4000 nm) and at colder temperatures (down to 20 K). In this contribution we describe the main requirements of the bench, the novel mechanical and thermal concepts of the modular cryostat, as well as the requirements of the readout electronics chain, including a new detector controller. We also present ESA’s package and flex design for Leonardo’s LAPD (Large-format Avalanche Photo Diode array) device, the first detector to be tested with this new bench.
To tackle the ever-more demanding requirements of upcoming astronomical instruments, emphasis is being put on accurate, reliable, and reusable models to simulate detector effects on images. The open-source python package Pyxel aims at solving these issues by providing a simulation framework where detector effects models can be easily implemented, pipelined and calibrated or validated against test data. In this contribution, we detail how by using the Pyxel framework, it is possible to calibrate ArCTIC – a model for simulating and correcting Charge Transfer Inefficiency in CCDs – and check its correction efficiency for realistic galaxy images acquired using an irradiated Teledyne e2v CCD273.
Peter Verhoeve, Sander Blommaert, Dennis Breeveld, Joerg ter Haar, Frederic lemmel, Yves Levillain, Cornelis van der Luijt, Thibaut Prod'homme, Hans Smit, Brian Shortt, Ivo Visser
This conference presentation was prepared for the X-Ray, Optical, and Infrared Detectors for Astronomy X conference at SPIE Astronomical Telescopes + Instrumentation, 2022.
Detector modelling is becoming more and more critical for the successful development of new instruments in scientific space missions and ground-based experiments. Specific modelling tools are often developed from scratch by each individual project and not necessarily shared for reuse by a wider community. To foster knowledge transfer, reusability and reliability in the instrumentation community, ESA and ESO joined forces and developed Pyxel, a framework for the simulation of scientific detectors and instruments. Pyxel is an open-source and collaborative project, based on Python, developed as an easy-to-use tool that can host and pipeline any kind of detector effect model. Recently Pyxel has achieved a new milestone: the public release and launch of version 1.0 which simplified third-party contributions and improved ease of use even further. Since its launch, Pyxel has been experiencing a growing user community and is being used to simulate all kinds of detectors beyond the traditional Charged-Coupled Devices and CMOS devices, for example Microwave Kinetic Inductance Detectors (MKID) and Avalanche Photo Diode (APD) devices. We give a tour of Pyxel’s version 1.0 changes and new features including a new interface, parallel computing, and new detectors and models. We continue with an example of using Pyxel as a tool for model optimization and calibration. Finally, we describe an example of how Pyxel and its features can be used to develop a full-scale end-to-end instrument simulator.
The exposure of Charge-Coupled Devices (CCD) to high-energy particles in space leads to a degradation of their performances. One of the observed mechanisms is the creation of defects in the CCD silicon lattice by displacement damage, inducing a reduction of the Charge Transfer Efficiency (CTE), i.e. the ability of the device to efficiently transfer the photo-induced charge to the read-out output node. Hence a reduction of the imaging quality of the detector. We present here a comparison of the modelled and measured optical quality of the FLEX CCD exposed to a high energy proton flux. The optical quality was directly measured on an irradiated flight representative device. A physical model of the detector, including an accurate modelling of the charge trapping dynamic, is used to generate synthetic scenes affected by CTE degradation from which the optical quality is assessed and compared to the measurement. Eventually the correlation of the model and the measurement will allow to accurately assess the performances of a detector exposed to space radiation environment.
The Soft X-ray Imager (SXI) on-board the joint ESA-CAS SMILE mission is a wide-field lobster-eye telescope designed to characterize the Earth's magnetospheric boundaries, by observing emission from the solar wind charge exchange (SWCX) process in the soft X-ray band. It has two large CCD370 (Teledyne-e2v) detectors, derived from the CCD-Bruyeres for ESA’s PLATO mission, with minor optimizations for soft X-ray detection, related to higher responsivity and increased radiation hardness. We present the first performance results under X-ray illumination of the CCD370 in SXI-specific operating conditions, including 6x6 on-chip pixel binning, over a range of pixel readout rates and operating temperatures.
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.
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.
THESEUS (Transient High Energy Sky & Early Universe Surveyor) is one of the three candidates for the M5 mission of the European Space Agency. The favoured mission will be announced in 2021 for an expected launch in 2032. THESEUS will be equipped with a Soft X-ray Imager (SXI) composed of a set of two telescopes using micro-pore optics offering an overall field of view of 0.5 sr (<2’ accuracy) for X-ray energies between 300 eV and 5 keV. The focal plane of each SXI telescope has a 16 x 16 cm2 cooled detector area. However, the limited radiator accommodation on the spacecraft prohibits the use of CCDs since cooling the focal planes to an optimal temperature for radiation hardness (<-100 ◦C) is not feasible. Therefore, the development of a suitable CMOS Image Sensor (CIS), capable of handling the expected levels of radiation at higher operating temperatures (approximately -30 ◦C) has been proposed. To demonstrate the performance required for the THESEUS SXI detector, a 2 x 2 cm2 prototype is under development using Open University pixel designs in a Teledyne-e2v digital CMOS platform. The pixel design will allow full depletion over silicon thickness of 35 µm for optimal soft X-ray quantum efficiency and instrument background suppression, and will be capable of near-Fano-limited spectral resolution that will also be of prime interest for synchrotron and Free Electron Lasers (FEL) applications. In this paper, we will present the design considerations and simulations leading to the implemented structures complying with THESEUS’ SXI requirements.
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 will provide a demonstration of Pyxel’s basic principles, describe newly added capabilities and the main models already implemented, and give examples of more advanced applications.
We present a ray tracing simulation of the Soft X-ray Imager (SXI) optics for the THESEUS observatory using the open-source McXtrace software package. THESEUS is a candidate mission within the Cosmic Vision programme of the European Space Agency and is designed to monitor high-energy transient events in the entire sky, therefore relying on fast slewing of the spacecraft. This capability will however impose large temperature variations and gradients across the optics which can cause thermoelastic deformation of the Soft X-ray Imager microchannel optics. The purpose of this study is to evaluate the impact on the point spread function (PSF) due to in-orbit temperature variation. Based on thermal analysis of the Soft X-ray Imager, perturbations to the ideal microchannel geometry are derived and provided as input to the ray tracer.
In the context of PLATO | ESA's exo-Earth hunting mission due for launch in 2026 | the Science Payload Validation team at ESA/ESTEC have performed a cryogenic proton irradiation and testing campaign of the PLATO CCD radiation test vehicle the Teledyne-e2v CCD280. Following the irradiation in standard conditions (room temperature, unbiased) of one device, and the irradiation of another in close to flight conditions (at T=203K and operated), the devices performance (CTI, dark current, hot pixels, trap population) were concurrently monitored over a two month period, first at a constant temperature and then following several temperature cycles. The results of these investigations will be presented.
Pyxel is a novel, open-source and Python-based framework designed to host and pipeline any type of models simulating detector effects such as cosmic rays, detector PSF, various noise sources, Charge Transfer Inefficiency or persistence on images produced by CCD or CMOS-based imaging detectors. It is currently under development at the European Space Agency with the goal of release it to the broader detector scientist community. We present here the architecture of the framework, how to integrate new models in it and give a few examples of its current simulation capabilities.
KEYWORDS: Particles, Charge-coupled devices, Data modeling, Silicon, Electrons, Computer simulations, Space operations, Monte Carlo methods, Stars, Sensors
ESA’s astrometry mission Gaia was launched in 2013 to establish the most accurate and complete map of the Milky Way by measuring the distance, position, proper motion, and astrophysical characteristics of two billion stars. It contains the largest focal plane ever flown in space comprising 106 CCDs. To downlink to Earth only useful data, an on-board algorithm was designed to discriminate between e.g. stars and cosmics- ionizing tracks left by energetic particles. A cosmic ray event generation simulator was developed to train and optimize this on-board source detection algorithm. We can now validate this model against Gaia data.
The European Space Agency strongly supports detector development in Europe from the gamma ray up to the far-infrared wavelengths. The requirements associated to these detector developments are linked to the spatial environment and the needed instrument performance. This paper reports on the status of these developments, the roadmap and the actual performance of the manufactured devices.
KEYWORDS: Charge-coupled devices, Monte Carlo methods, 3D modeling, Radiation effects, Device simulation, Electrodes, Data modeling, Instrument modeling, Signal processing, Imaging systems
The visible imager 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 charge-coupled device (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 be possible only through the correction of radiation damage effects. We have therefore created a Monte Carlo model that simulates the physical processes taking place when transferring signals 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 the three-dimensional trap position, potential structure of the pixel, and multilevel 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 making 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.
KEYWORDS: Sensors, Near infrared, Liquid phase epitaxy, Astronomy, Readout integrated circuits, Interference (communication), Digital signal processing, Signal detection, Capacitance, Prototyping
The Payload Technology Validation section in the Future Missions office of ESA's Science directorate at ESTEC provides testing support to present and future missions at different stages in their lifetime, from early technology developments to mission operation validation. In this framework, a test setup to characterize near-infrared (NIR) detectors has been created. In the context of the Astronomy Large Format Array for the near-infrared ("ALFA-N") technology development program, detectors from different suppliers are tested. We report on the characterization progress of the ALFA-N detectors, for which a series of rigorous tests have been performed on two different detectors; one provided by CEA/Leti-CEA/IRFU-SOFRADIR, France and the other by SELEX- UK/ATC, UK. Experimental techniques, the test bench and methods are presented. The conversion gain of two different detectors is measured using the photon transfer curve method. For a Leti LPE detector the persistence effect has been probed across a range of illumination levels to reveal a sharp linear increase of persistence below full-well and a plateauing beyond saturation. The same detector has been proton irradiated which has resulted in no significant dark current increase.
PLATO { PLAnetary Transits and Oscillations of stars { is the third medium-class mission to be selected in the European Space Agency (ESA) Science and Robotic Exploration Cosmic Vision programme. Due for launch in 2025, the payload makes use of a large format (8 cm x 8 cm) Charge-Coupled Devices (CCDs), the e2v CCD270 operated at 4 MHz and at -70 C. To de-risk the PLATO CCD qualification programme initiated in 2014 and support the mission definition process, ESA's Payload Technology Validation section from the Future Missions Office has developed a dedicated test bench.
PLATO – PLAnetary Transits and Oscillations of stars – is the third medium-class mission (M3) to be selected in the European Space Agency (ESA) Science and Robotic Exploration Cosmic Vision programme. It is due for launch in 2025 with the main objective to find and study terrestrial planets in the habitable zone around solar-like stars. The payload consists of >20 cameras; with each camera comprising 4 Charge-Coupled Devices (CCDs), a large number of flight model devices procured by ESA shall ultimately be integrated on the spacecraft. The CCD270 – specially designed and manufactured by e2v for the PLATO mission – is a large format (8 cm x 8 cm) back-illuminated device operating at 4 MHz pixel rate and coming in two variants: full frame and frame transfer. In order to de-risk the PLATO CCD procurement and aid the mission definition process, ESA’s Payload Technology Validation section is currently validating the PLATO CCD270. This validation consists in demonstrating that the device achieves its specified electrooptical performance in the relevant environment: operated at 4 MHz, at cold and before and after proton irradiation. As part of this validation, CCD270 devices have been characterized in the dark as well as optically with respect to performance parameters directly relevant for the photometric application of the CCDs. Dark tests comprise the measurement of gain sensitivity to bias voltages, charge injection tests, and measurement of hot and variable pixels after irradiation. In addition, the results of measurements of Quantum Efficiency for a range of angles of incidence, intra– pixel response (non-)uniformity, and response to spot illumination, before and after proton irradiation. In particular, the effect of radiation induced degradation of the charge transfer efficiency on the measured charge in a star-like spot has been studied as a function of signal level and of position on the pixel grid, Also, the effect of various levels of background light on the amount of charge lost from a star image are described. These results can serve as a direct input to the PLATO consortium to study the mission performance and as a basis for further optimization of the CCD operation.
PLATO { PLAnetary Transits and Oscillations of stars { is the third medium-class mission to be selected in the European Space Agency (ESA) Science and Robotic Exploration Cosmic Vision programme. Due for launch in 2025, the payload makes use of a large format (8 cm x 8 cm) Charge-Coupled Devices (CCDs) the e2v CCD270 operated at 4 MHz. The manufacture of such large device in large quantity constitutes an unprecedented effort. To de-risk the PLATO CCD procurement and aid the mission definition process, ESA's Payload Technology Validation team is characterizing the electro-optical performance of a number of PLATO devices before and after proton irradiation.
KEYWORDS: Charge-coupled devices, Radiation effects, Earth's atmosphere, Silicon, 3D modeling, Monte Carlo methods, Electrodes, Signal processing, Computer simulations, Neon
The radiation damage effects from the harsh radiative environment outside the Earth's atmosphere can be a cause for concern for most space missions. With the science goals becoming ever more demanding, the requirements on the precision of the instruments on board these missions also increases, and it is therefore important to investigate how the radiation induced damage affects the Charge-Coupled Devices (CCDs) that most of these instruments rely on. The primary goal of the Euclid mission is to study the nature of dark matter and dark energy using weak lensing and baryonic acoustic oscillation techniques. The weak lensing technique depends on very precise shape measurements of distant galaxies obtained by a large CCD array. It is anticipated that over the 6 year nominal lifetime of mission, the CCDs will be degraded to an extent that these measurements will not be possible unless the radiation damage effects are corrected. 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 close as possible. The code runs on a single electrode level and takes charge cloud size and density, three dimensional trap position, and multi-level clocking into account. A key element of the model is that it 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.
The European Space Agency has a very strong interest in the performance enhancement of detector arrays for future scientific and astronomy missions. Improvements in Visible and Infrared wavelengths are of particular interest and the Agency undertakes a programme of continuous development aimed at enhancing the capability of detectors in these wavebands. This paper presents the status of these detector technology development activities.
KEYWORDS: Charge-coupled devices, Diagnostics, Sensors, Space operations, Diagnostics, Solar energy, Atrial fibrillation, Staring arrays, Temperature metrology, Electrons, Solar processes
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.
Energetic particles in space damage electronic components, and in particular affect the capability of Charge-Coupled Devices (CCD) to transfer photo-generated charge packets to the output node. If not properly accounted for either during the instrument design process or in the mission data processing pipeline, radiation-induced Charge Transfer Inefficiency (CTI) causes image distortion, decreases the signal-to-noise ratio, and ultimately leads to bias in the measurement carried out. CTI is a well-identified error budget contributor for mission operating in the photon-starving regime like space telescopes dedicated to Astronomy, but is less studied in the context of Earth Observation missions. We present a study conducted during the Sentinel-4/UVN CCD pre-development to provide a first assessment of the CTI effects on the Sentinel-4 measurements.
KEYWORDS: Galactic astronomy, Charge-coupled devices, Point spread functions, Stars, Photomasks, Data modeling, Data acquisition, Electroluminescence, Modeling, Data processing
Euclid is the ESA mission to map the geometry of the dark universe. It uses weak gravitational lensing, which requires the accurate measurement of galaxy shapes over a large area in the sky. Radiation damage in the 36 Charge-Coupled Devices (CCDs) composing the Euclid visible imager focal plane has already been identified as a major contributor to the weak-lensing error budget; radiation-induced charge transfer inefficiency (CTI) distorts the galaxy images and introduces a bias in the galaxy shape measurement. We designed a laboratory experiment to project Euclid-like sky images onto an irradiated Euclid CCD. In this way – and for the first time – we are able to directly assess the effect of CTI on the Euclid weak-lensing measurement free of modelling uncertainties. We present here the experiment concept, setup, and first results. The results of such an experiment provide test data critical to refine models, design and test the Euclid data processing CTI mitigation scheme, and further optimize the Euclid CCD operation.
The science objectives of space missions using CCDs to carry out accurate astronomical measurements are put at risk by the radiation-induced increase in charge transfer inefficiency (CTI) that results from trapping sites in the CCD silicon lattice. A variety of techniques are used to obtain CTI values and derive trap parameters, however they often differ in results. To identify and understand these differences, we take advantage of an on-going comprehensive characterisation of an irradiated Euclid prototype CCD including the following techniques: X-ray, trap pumping, flat field extended pixel edge response and first pixel response. We proceed to a comparative analysis of the obtained results.
The radiation environment at L2 is of great importance to the science instruments of Gaia. Especially the non-ionising damage to the CCDs and the resulting increase in charge transfer inefficiency will ultimately limit the achievable science performance. With its launch in December 2013 for a nominal mission of 5 years Gaia is continuously collecting invaluable information of radiation effects on the 106 CCDs in the FPA from the analysis of the science data and dedicated calibration procedures. The paper shows first results and discusses the detected irradiation background with respect to predictions and reviews operational implications for the mission.
The focal plane array of the Euclid VIS instrument comprises 36 large area, back-illuminated, red-enhanced CCD detectors (designated CCD 273). These CCDs were specified by the Euclid VIS instrument team in close collaboration with ESA and e2v technologies. Prototypes were fabricated and tested through an ESA pre-development activity and the contract to qualify and manufacture flight CCDs is now underway. This paper describes the CCD requirements, the design (and design drivers) for the CCD and package, the current status of the CCD production programme and a summary of key performance measurements.
ESA’s astronomy missions make wide use of CCDs as their main photon detectors. Depending on the scientific goals of the mission, different aspects the CCD’s performance may be critical for the achievement of these goals. The Payload Technology Verification section of ESA’s Future Missions Preparation Office has a task to provide support on issues related to payload performance. For that purpose we operate a versatile CCD test bench. We present test results on CCDs for missions that are currently under study (PLATO) or under development (EUCLID, CHEOPS).
ESA's Gaia mission aims to create a complete and highly accurate stereoscopic map of the Milky Way. The
stellar parallaxes will be determined at the micro-arcsecond level, as a consequence the measurement of the
stellar image location on the CCD must be highly accurate. The solar wind protons will create charge traps in
the CCDs of Gaia, which will induce large charge loss and distort the stellar images causing a degradation of
the location measurement accuracy. Accurate modelling of the stellar image distortion induced by radiation is
required to mitigate these effects. We assess the capability of a fast physical analytical model of radiation damage
effects called the charge distortion model (CDM) to reproduce experimental data. To realize this assessment
we developed a rigorous procedure that compares at the sub-pixel level the model outcomes to damaged images
extracted from the experimental tests. We show that CDM can reproduce accurately up to a certain level the test
data acquired on a highly irradiated device operated in time delay integration mode for different signal levels and
different illumination histories. We discuss the potential internal and external factors that contributed to limit
the agreement between the data and the charge distortion model. To investigate these limiting factors further,
we plan to apply our comparison procedure on a synthetic dataset generated through detailed Monte-Carlo
simulations at the CCD electrode level.
The European Space Agency's Gaia mission1 is scheduled for launch in 2012. It will operate at L2 for 5 years,
rotating slowly 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 relative position, parallax-distance and proper motion of every
observed star, yielding a three dimensional dynamical model of our galaxy. The focal plane contains 106 large
area silicon CCDs continuously operating in TDI mode at a line rate synchronised with the satellite rotation.2
One of the greatest challenges facing the mission is radiation damage in the CCDs which will cause charge
loss and image distortion. This is particularly severe because the large focal plane is difficult to shield and
because the launch will coincide with solar maximum. Despite steps taken to minimize the effects of radiation
(e.g. regular use of charge injection), the residual distortion will need to be calibrated during the pipeline data
processing. Due to the volume of data involved, this requires a trapping model which is physically realistic, yet
fast enough and simple enough to implement in the pipeline. The current prototype Charge Distortion Model
will be presented. This model was developed specifically for Gaia in TDI mode. However, an imaging mode
version has already been applied to other missions, for example, to indicate the potential impact of radiation
damage on the proposed Euclid mission.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.