MAJIS is part of the science payload of the ESA L-Class mission JUICE to be launched in 2022 with an arrival at Jupiter in 2030. MAJIS will perform imaging spectroscopy through two channels: VIS-NIR (0.50 µm - 2.35 µm) and IR (2.25 µm - 5.54 µm). The Royal Belgian Institute for Space Aeronomy (BIRA-IASB) and the Royal Observatory of Belgium (ROB) contribute to MAJIS with the characterization and calibration of the VIS-NIR Flight Model (FM) and Spare Model (SM) detectors, including the design, development, and validation of the setup, as well as the data processing pipeline. The FM and SM detectors are characterized under different illumination conditions (along four decades of dynamical range), temperature (125 K - 144 K), beam uniformities, exposure times, and/or data acquisition rates. In this paper, we describe the optical performances of the facility, which can be configurable for dark conditions, uniform light beam, and convergent beam with same focal ratio as MAJIS convergence optics. We provide a relative radiometry scale for the typical characterization measurements, as well as a fully characterized flux that will allow us to perform characterization measurements in an absolute radiometry scale, such as quantum efficiency (QE). In addition, we describe the thermal performances provided by the bench reaching different temperature scenarios, including the expected operating temperature of the detector at 132 K. The characterization facility was completed and subjected to validation tests in early 2020. The MAJIS VIS-NIR FM detector was delivered for its complete characterization in June 2020.
MAJIS (Moons And Jupiter Imaging Spectrometer) is one of the science instruments of the ESA L-Class mission JUICE (Jupiter ICy Moons Explorer) to be launched in 2022 with an arrival at Jupiter in 2030. MAJIS will perform imaging spectroscopy through two channels: VIS-NIR (0.50 um - 2.35 um) and IR (2.25 μm - 5.54 μm). The Royal Belgian Institute for Space Aeronomy (BIRA-IASB) and the Royal Observatory of Belgium (ROB) contribute to MAJIS with the characterization of the VIS-NIR Flight Model (FM) and Spare Model (SM) detectors, including the design, development and validation of the setup, and the data processing pipeline. Typical detector characterization measurements were performed during the campaigns but also calibrated measurements such as Quantum Efficiency (QE). Since some of the characterization measurements require different illumination conditions, temperature, beam uniformity, exposure time, and/or data acquisition procedure, the characterization setup is configurable for dark conditions, uniform light beam, and convergent beam with same focal ratio as MAJIS convergence optics. The thermal-vacuum characterization facility was completed at BIRA-IASB premises and was subjected to validation tests on late 2019 and early 2020. MAJIS VIS-NIR FM detector was delivered for its complete characterization in June 2020; SM characterization shall be performed after time of meeting. In this paper, we summarize the optical and thermal performances of the facility, the detector's mechanical integration method and its optical alignment into the setup, the security system implemented, the general operation of the setup during the characterization campaign, and FM preliminary result analyses.
Proc. SPIE. 10562, International Conference on Space Optics — ICSO 2016
KEYWORDS: Staring arrays, Signal to noise ratio, Point spread functions, Astronomy, Sensors, Laser range finders, Fourier transforms, Charge-coupled devices, Modulation transfer functions, Astronomical imaging
The intrapixel response is the signal detected by a single pixel illuminated by a Dirac distribution as a function of the position of this Dirac inside this pixel. It is also known as the pixel response function (PRF). This function measures the sensitivity variation at the subpixel scale and gives a spatial map of the sensitivity across a pixel.
The reduction of systematic effects is necessary to improve the accuracy in imaging and astrometry. For example, in Euclid Mission which aims at carrying out accurate measurements of dark energy and quantifying precisely its role in the evolution of the Universe, systematic effects need at be controlled to a level better than 10-7 (Euclid, Science Book). To achieve this goal, a high-level of knowledge of the system point spread function (PSF) is required. This paper follows the concept-paper presented at the last SPIE conference1 and gives the recent developments achieved in the design of the test bench for the intrapixel sensitivity measurements. The measurement technique we use is based on the projection of a high spatial resolution periodic pattern on the detector using the self-imaging property of a new class of diffractive objects named continuously self-imaging gratings (CSIG) and developed at ONERA. The principle combines the potential of global techniques, which make measurements at once on the whole FPA, and the accuracy of spot-scan-based techniques, which provide high local precision.
Theia is an astrometric mission proposed to ESA in 2014 for which one of the scientific objectives is detecting
Earth-like exoplanets in the habitable zone of nearby solar-type stars. This objective requires the capability
to measure stellar centroids at the precision of 1x10-5 pixel. Current state-of-the-art methods for centroid
estimation have reached a precision of about 3x10-5 pixel at two times Nyquist sampling, this was shown at
the JPL by the VESTA experiment. A metrology system was used to calibrate intra and inter pixel quantum
efficiency variations in order to correct pixelation errors. The Theia consortium is operating a testbed in vacuum
in order to achieve 1x10-5 pixel precision for the centroid estimation. The goal is to provide a proof of concept
for the precision requirement of the Theia spacecraft.
The testbed consists of two main sub-systems. The first one produces pseudo stars: a blackbody source is
fed into a large core fiber and lights-up a pinhole mask in the object plane, which is imaged by a mirror on the
CCD. The second sub-system is the metrology, it projects young fringes on the CCD. The fringes are created by
two single mode fibers facing the CCD and fixed on the mirror. In this paper we present the latest experiments
conducted and the results obtained after a series of upgrades on the testbed was completed. The calibration
system yielded the pixel positions to an accuracy estimated at 4x10-4 pixel. After including the pixel position
information, an astrometric accuracy of 6 x 10-5 pixel was obtained, for a PSF motion over more than 5 pixels.
In the static mode (small jitter motion of less than 1 x 10-3 pixel), a photon noise limited precision of 3x10-5
pixel was reached.
This paper is devoted to the presentation of a new technique of characterization of the Intra-Pixel Sensitivity Variations (IPSVs) of astronomical detectors. The IPSV is the spatial variation of the sensitivity within a pixel and it was demonstrated that this variation can contribute to the instrument global error. Then IPSV has not to be neglected especially in the case of under-sampled instruments for high quality imaging and accurate photometry. The common approaches to measure the IPSV consist in determining the pixel response function (PRF) by scanning an optical probe through the detector. These approaches require high-aperture optics, high precision mechanical devices and are time consuming. The original approach we will present in this paper consists in projecting high-resolution periodic patterns onto the whole sensor without classic optics but using the self-imaging property (the Talbot effect) of a Continuously Self Imaging Grating (CSIG) illuminated by a plane wave. This paper describes the test bench and its design rules. The methodology of the measurement is also presented. Two measurement procedures are available: global and local. In the global procedure, the mean PRF corresponding to the whole Focal Plane Array (FPA) or a sub-area of the FPA is evaluated. The results obtained applying this procedure on e2v CCD 204 are presented and discussed in detail. In the local procedure, a CSIG is moved in front of each pixel and a pixel PRF is reconstructed by resolving the inverse problem. The local procedure is presented and validated by simulations.