Sylvain Ferriol

Impact of noise covariance and nonlinearities in NIR H2RG detectors

We characterize at pixel level a NIR H2RG detector read with SIDECAR ASIC, similar to the detectors used in Euclids Near IR Spectrometer Photometer (NISP). We derive the full covariance matrix formulae, extending the results from previous publications, and compare them to data and simulations for NISP baseline operating modes. The nonlinear response of the detector is measured and high precision maps are derived for in-flight or on-ground correction. High precision maps of the conversion gain are also determined using the Photon Transfer Curve technique.

Detector chain calibration strategy for the Euclid flight IR H2RGs

Euclid is an ESA mission to map the geometry of the Dark Universe with a planned launch date in 2021.1 Two primary cosmological probes, weak gravitational lensing and baryonic acoustic oscillations, are implemented through a VISible imager (VIS) and a Near-Infrared Spectrometer and Photometer (NISP).2 The ground characterization of the NISP Flight Sensor Chip Systems (SCS) followed by the pixel response calibration aims to produce all informations to correct and control the accuracy of the signal. This work reports on the ground characterization of the NISP detector chain. The detector and electrical effects are likely to generate statistical fluctuations and systematic errors on the final flux measurement. The analysis strategies to maintain the pixel relative response accuracy within 1% is proposed in this work. The Euclid NISP test ow is presented and the main concerns of the detector chain calibration, such as non-linearity, charge trapping and de-trapping are discussed on the basis of the analysis of the flight detectors characterization data.

Impact of common modes correlations and time sampling on the total noise of a H2RG near-IR detector

We present the readout noise reduction methods and the 1/f noise response of an 2K × 2K HgCdTe detector similar to the detectors that will be used in the Near Infrared Spectrometer Photometer - one of the instruments of the future ESA mission named Euclid. Various algorithms of common modes subtraction are defined and compared. We show that the readout noise can be lowered by 60% using properly the references provided within the array. A predictive model of the 1/f noise with a given frequency power spectrum is defined and compared to data taken in a wide range of sampling frequencies. In view of this model the definition of ad-hoc readout noises for different sampling can be avoided.

Random telegraph signal (RTS) in the Euclid IR H2RGs

Euclid is an ESA mission to map the geometry of the dark Universe with a planned launch date in 2021. Euclid is optimised for two primary cosmological probes, weak gravitational lensing and baryonic acoustic oscillations. They are implemented through two science instruments on-board Euclid, a visible imager (VIS) and a near-infrared photometer/spectrometer (NISP), which are being developed and built by the Euclid Consortium instrument development teams. The NISP instrument contains a large focal plane assembly of 16 Teledyne HgCdTe H2RG detectors with 2.3 μm cut-off wavelength and SIDECAR readout electronics. The performance of the detector systems is critical for the science return of the mission and extended on-ground tests are being performed for characterisation and calibration purposes. Special attention is given also to effects even on the scale of individual pixels, which are difficult to model and calibrate, and to identify any possible impact on science performance. This paper discusses the known effect of random telegraph signal (RTS) in a follow-on study of test results from the Euclid NISP detector system demonstrator model [1], addressing open issues and focusing on an in-depth analysis of the RTS behaviour over the pixel population on the studied Euclid H2RGs.

Characterization of H2RG IR detectors for the Euclid NISP instrument

Euclid, a major ESA mission for the study of dark energy, will offer a large survey of tens of millions of galaxies thanks to its Near-Infrared Spectro-Photometer. For it to be successful, the 16 Teledynes 2.3 μm cutoff 2048x2048 pixels IR HgCdTe detectors of the focal plane must show very high performances over more than 95% of pixels, in terms of median dark current, total noise, budget error on non-linearity after correction, residual dark due to latency effects and quantum efficiency. This will be verified through a thorough characterization of their performances, leading to the production of the pixel map calibration database for the Euclid mission. Characterization is challenging in many ways: each detector will have to be fully and accurately characterized in less than three weeks, with rather tight requirements: dark current at the 10-3 e-/s level with 10% accuracy, relative Pixel Response map better than 1%, obtained with an illumination flatness better than 1%, measurements alternating dark and high level illumination taking care of latency impacts. Due to statistics needs, very long runs (24h without interrupts) of scripted measurements would be executed. Systematics of the test bench should be at the end the limiting factor of the parameter measurement accuracy. Test plan, facilities with functionalities developed for those specific purposes and associated performances will be described.

Low noise flux estimate and data quality control monitoring in EUCLID-NISP cosmological survey

Euclid mission is designed to understand the dark sector of the universe. Precise redshift measurements are provided by H2RG detectors. We propose an unbiased method of fitting the flux with Poisson distributed and correlated data, which has an analytic solution and provides a reliable quality factor - fundamental features to ensure the goals of the mission. We compare our method to other techniques of signal estimation and illustrate the anomaly detection on the flight-like detectors. Although our discussion is focused on Euclid NISP instrument, much of what is discussed will be of interest to any mission using similar near-infrared sensors.

Random telegraph signal (RTS) noise and other anomalies in the near-infrared detector systems for the Euclid mission

Euclid is an ESA mission to map the geometry of the dark Universe with a planned launch date in 2020. Euclid is optimised for two primary cosmological probes, weak gravitational lensing and galaxy clustering. They are implemented through two science instruments on-board Euclid, a visible imager (VIS) and a near-infrared spectro-photometer (NISP), which are being developed and built by the Euclid Consortium instrument development teams. The NISP instrument contains a large focal plane assembly of 16 Teledyne HgCdTe H2RG detectors with 2.3μm cut-off wavelength and SIDECAR readout electronics. The performance of the detector systems is critical to the science return of the mission and extended on-ground tests are being performed for characterisation and calibration purposes. Special attention is given also to effects even on the scale of individual pixels, which are difficult to model and calibrate, and to identify any possible impact on science performance. This paper discusses a variety of undesired pixel behaviour including the known effect of random telegraph signal (RTS) noise based on initial on-ground test results from demonstrator model detector systems. Some stability aspects of the RTS pixel populations are addressed as well.

Characterization of Euclid-like H2RG IR detectors for the NISP instrument

The success of the Euclids NISP (Near-Infrared Spectro-Photometer) instrument for the Euclid mission requires very high performance detectors for which tight specifications have been defined. These must be verified over more than 95% of the focal plane which is equipped with 16 H2RG infrared pixel detectors. Teledyne will provide these detectors and their electronics under ESA and NASA contracts. The detectors will be selected, qualified then delivered to the NISP instrument under Euclid specifications. To prepare the future calibration plan, these detectors must also be fully characterized at the pixel level before their integration. This characterization is crucial to the future processing and in-flight calibration. For a good control of the performance, the detector specifications for Euclid require in one hand to know some characteristics such as noise and dark current at a level as low as 10-3 e- /s , but also in other hand, require to have model of some specific properties of these detectors such as their non-linearity response, or their latency signals, which will imply specific measurements, characterization and studies. For this purpose, we have constructed dedicated facilities, and prepared a full test plan with adapted analysis methods and software tools that will be used to calibrate flight detectors. Here we describe the status of this plan, the facilities and their validation. We then present some preliminary results on dark current, total noise, CDS noise and some first estimations of persistence, using high performance engineering grade Euclid detectors provided by ESA. A pilot run is foreseen at the end of the year to validate the full test plan. Next step will be the characterization of flight detectors expected to start mid 2016.