When developing new astronomical instruments, there is a need to perform the characterization of their individual components, especially the detectors, to ensure that their performances comply with the scientific objectives of the instrument. A visible-near infrared (VIS-NIR) facility was developed for the absolute and relative radiometric characterization of space-based detectors at the Royal Belgian Institute for Space Aeronomy (BIRA-IASB). The facility operates from 0.4 to 2.65 μm in an ISO-5 environment. It offers a tunable monochromatic flux with a high level of straylight rejection (10 − 8) and 2% uniformity, over a four-decade range of intensity with adjustable bandwidth. Latency measurements are also possible. Thermalization is offered within a precision of 7 mK between 50 K and 382 K. The ultimate vacuum level of the detector chamber is below 10 − 6 mbar. A robust security system avoids both reaching temperatures outside the operational range of the detector and its electronics, and contamination due to vacuum loss. The facility was already used to characterize the VIS-NIR detectors of the Moons And Jupiter Imaging Spectrometer (MAJIS), one of the instruments on board the Jupiter ICy Moons Explorer (JUICE). The versatility provided by the VIS-NIR facility allows its use for the characterization of other astronomical detectors.
The JUICE (JUpiter ICy moons Explorer) mission by ESA aims to explore the emergence of habitable worlds around gas giants and the Jupiter system as an archetype of gas giants. MAJIS (Moons and Jupiter Imaging Spectrometer) is the visible to near-infrared imaging spectrometer onboard JUICE which will characterize the surfaces and exospheres of the icy moons and perform monitoring of the Jupiter atmosphere. The launch is scheduled for 2023 with the first MAJIS observations inside the Jovian system occurring more than 8 years later. The MAJIS optical head is equipped with two Teledyne H1RG detectors, one for each of the two spectrometer channels (VIS-NIR and IR). This paper describes the characterization of the VIS-NIR Focal Plane Unit. These detectors will be operated in a non-standard way, allowing near/full-frame retrieval over short integration times (<< 1 sec) while maintaining good noise performance. After a quick description of the characterization strategy that was designed to evaluate the performances of the VIS-NIR detector according to the MAJIS operational specifications, the paper will address the data analyses and the main results of the characterization campaign. The major performance parameters such as dark current, linearity, noise, quantum efficiency, and operability will be presented and compared with the requirements.
KEYWORDS: Sensors, Frequency modulation, Fermium, Jupiter, Radiometry, Radio optics, Quantum efficiency, Data modeling, Temperature metrology, Spectroscopy
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.
KEYWORDS: Sensors, Frequency modulation, Fermium, Jupiter, Telecommunications, Data modeling, Control systems, Temperature metrology, Staring arrays, Spectroscopy
MAJIS is part of the science payload of the JUICE mission to be launched in 2022. BIRA-IASB and 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, as well as the data processing pipeline. The VIS-NIR detectors are thermalized within a temperature range from 125 K to 150 K during their characterization campaigns. Moreover, the temperature of their electronic units must always remain above 120 K to avoid any irreparable damage, and below 160 K for operative conditions. Likewise, to avoid any risk of contamination, the detector should preferably be operated below 10-5 mbar of vacuum. To fulfill these requirements, a complete security system was developed; it includes redundant thermal control loops, alarms from every pressure and temperature monitoring devices in use, and a robust semi-automatic control system for the pumping and cryocooling equipment. Moreover, the security system is complemented by the Temperature Ground Support Equipment (TGSE), which provides a LabVIEW user-friendly interface to communicate the status of the detector and the vacuum chamber in real-time. This subsystem was successfully validated in May 2020, before the delivery of the FM detector in June 2020. In this paper, we summarize the design, implementation and validation tests of the security system as well as the thermal and vacuum performances of the facility. We also show the thermal behavior of the detector during acquisitions representative of typical MAJIS observations.
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.
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