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A detailed study of reciprocity failure in four 1.7 micron cutoff HgCdTe near-infrared detectors is presented. The sensitivity to reciprocity failure is approximately 0.1%decade over up to five orders of magnitude in illumination intensity. The four detectors, which represent three successive production runs with modified growth recipes, show large differences in amount and spatial structure of reciprocity failure. Reciprocity failure could be reduced to negligible levels by cooling the detectors to about 110 K. No wavelength dependence was observed. The observed spatial structure appears to be weakly correlated with image persistence.
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Flux dependent non-linearity (reciprocity failure) in HgCdTe NIR detectors with 1.7 micron cut-off was investigated. A dedicated test station was designed and built to measure reciprocity failure over the full dynamic range of near infrared detectors. For flux levels between 1 and 100,000 photons/sec a limiting sensitivity to reciprocity failure of 0.3%/decade was achieved. First measurements on several engineering grade 1.7 micron cut-off HgCdTe detectors show a wide range of reciprocity failure, from less than 0.5%/decade to about 10%/decade. For at least two of the tested detectors, significant spatial variation in the effect was observed. No indication for wavelength dependency was found. The origin of reciprocity failure is currently not well understood. In this paper we present details of our experimental set-up and show the results of measurements for several detectors.
Flux dependent non-linearity (reciprocity failure) in HgCdTe near infrared detectors can severely impact an instruments performance, in particular with respect to precision photometric measurements. The cause of this effect is presently not understood. To investigate reciprocity failure, a dedicated test system was built. For flux levels between 1 and 50,000 photons/s, a sensitivity to reciprocity failure of approximately 0.1%/decade was achieved. A wavelength independent non-linearity due to reciprocity failure of about 0.35%/decade was measured in a 1.7 micron HgCdTe detector.
Solar contamination, due to moonlight and atmospheric scattering of sunlight, can cause systematic errors in stellar radial velocity (RV) measurements that significantly detract from the ~10cm/s sensitivity required for the detection and characterization of terrestrial exoplanets in or near Habitable Zones of Sun-like stars. The addition of low-level spectral contamination at variable effective velocity offsets introduces systematic noise when measuring velocities using classical mask-based or template-based cross-correlation techniques. Here we present simulations estimating the range of RV measurement error induced by uncorrected scattered sunlight contamination. We explore potential correction techniques, using both simultaneous spectrometer sky fibers and broadband imaging via coherent fiber imaging bundles, that could reliably reduce this source of error to below the photon-noise limit of typical stellar observations. We discuss the limitations of these simulations, the underlying assumptions, and mitigation mechanisms. We also present and discuss the components designed and built into the NEID precision RV instrument for the WIYN 3.5m telescope, to serve as an ongoing resource for the community to explore and evaluate correction techniques. We emphasize that while bright time has been traditionally adequate for RV science, the goal of 10cm/s precision on the most interesting exoplanetary systems may necessitate access to darker skies for these next-generation instruments.
This paper proposes a cascading failure mitigation strategy based on Reinforcement Learning (RL). The motivation of the Multi-Stage Cascading Failure (MSCF) problem and its connection with the challenge of climate change are introduced. The bottom-level corrective control of the MCSF problem is formulated based on DCOPF (Direct Current Optimal Power Flow). Then, to mitigate the MSCF issue by a high-level RL-based strategy, physics-informed reward, action, and state are devised. Besides, both shallow and deep neural network architectures are tested. Experiments on the IEEE 118-bus system by the proposed mitigation strategy demonstrate a promising performance in reducing system collapses.
Teledynes H2RG detector images suffer from cross-hatch like patterns which arises from sub-pixel quantum efficiency (QE) variation. In this paper we present our measurements of this sub-pixel QE variation in the Habitable-Zone Planet Finders H2RG detector. We present a simple model to estimate the impact of sub-pixel QE variations on the radial velocity, and how a first order correction can be implemented to correct for the artifact in the spectrum. We also present how the HPFs future upgraded laser frequency comb will enable us to implement this correction.
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