The METimage instrument is an Airbus-primed passive superspectral imaging radiometer measuring thermal radiance emitted by the Earth and solar backscattered radiation in 20 spectral channels from 0.44µm to 13.35µm. The instrument achieves the entire Earth coverage at a low-Earth polar-orbit on daily basis by constantly scanning with spatial resolution of 500m at nadir and constant spatial sampling angle (SSA) across a 2670km swath. In the thermal domain, the most crucial part of the system is the pair of cryogenically-cooled HgCdTe (MCT) photodetectors intended for thermal-domain SMWIR and LVWIR, the development and manufacturing of which was contracted to LYNRED, who have successfully delivered the flight models to Airbus. In this work, the results of the Airbus-hosted flight detection-chain level test campaign in nominal vacuum and cryogenic environment are presented. Their system impacts are evaluated to conclude the expected full flight-worthiness of both delivered photodetectors into the METimage optical payload. First, both dark currents and offsets are characterized: both parameter noise levels quantitatively outperform their predicted values, minimizing their impact on the system signal-to-noise ratio (SNR). Then the response linearity of both photodetectors over the required thermal radiance ranges has been measured and has shown better performances than predicted by design over the setup-accessible solar and 185K to 280K thermal radiance ranges. Finally, the random telegraph signal (RTS) signature of both photodetectors is thoroughly characterized based on a novel sharp-edge detection method in conditions mimicking in-orbit operation: after periodic cooldowns and at stable nominal temperatures. Based on these measurements, the sub-pixel selection map (SPSM) is generated, enabling to deselect image elements that are deemed to degrade overall performance from a system perspective. Thanks to a demanding flight model selection procedure applied by LYNRED, the RTS test results of the sorted out devices are significantly better than expected, hence ensuring compliance for system SNR and homogeneity. Full flight worthiness is therefore confirmed and final integration of both photodetectors in the first METimage flight instrument optical system is currently ongoing. Additional presentation content can be accessed on the supplemental content page.
SOFRADIR is one of the leading companies involved in the development and manufacturing of infrared detectors for space applications. As a matter of fact, SOFRADIR is involved in many space programs from visible up to VLWIR spectral ranges. These programs concern operational missions for earth imagery, meteorology and also scientific missions for universe exploration. One of the last space detectors available at SOFRADIR is a visible – SWIR detector named Next Generation Panchromatic Detector (NGP) which is well adapted for hyperspectral, imagery and spectroscopy applications. In parallel of this new space detector, numerous programs are currently running for different kind of missions: meteorology (MTG), Copernicus with the Sentinel detectors series, Metop-SG system (3MI), Mars exploration (Mamiss, etc….)… In this paper, we present the last developments made for space activity and in particular the NGP detector. We will also present the space applications using this detector and show appropriateness of its use to answer space programs specifications, as for example those of Sentinel-5.
SOFRADIR is one of the leading companies involved in the development and manufacturing of infrared detectors for space applications. As a matter of fact, SOFRADIR is involved in many space programs from visible up to VLWIR spectral ranges. These programs concern operational missions for earth imagery, meteorology and also scientific missions for universe exploration. One of the last space detectors available at SOFRADIR is a visible – SWIR detector named Next Generation Panchromatic Detector (NGP) which is well adapted for hyperspectral, imagery and spectroscopy applications. In parallel of this new space detector, numerous programs are currently running for different kind of missions: meteorology (MTG), Copernicus with the Sentinel detectors series, Metop-SG system (3MI), Mars exploration (Mamiss, etc.). In this paper, we present the last developments made for space activity and in particular the NGP detector. We will also present the space applications using this detector and show appropriateness of its use to answer space programs specifications, as for example those of Sentinel-5.
Sofradir is developing products for space applications since the early 1990th. Thanks to this experience and based on the
different programs conducted up to now, Sofradir became a major supplier for the space industry regarding infrared
detectors.
Sofradir has developed a robust and versatile technology enabling to address most of the infrared detectors required by
space applications. Thus, Sofradir proposes high reliability Mercury Cadmium Telluride (MCT) with different format
(off-the-shelf or customized) covering bandwidths from visible to over 15 μm. In this connection, the latest development
concerned the extension, characterization and improvement of the MCT technology in visible range for hyperspectral
and spectroscopy needs. On the other part of the spectrum, Sofradir is continuing the development of detectors with large
cut-off wavelength (above 13 μm) for future space applications like meteorology for example. Finally, a recurrent work
is performed by Sofradir concerning the analysis of the compatibility of our infrared detectors with space environment
and in particular with radiation environment.
Adaptive optics provides a real time compensation for atmospheric turbulence which severely limits the resolution
of ground-based observation systems. The correction quality relies on a key component: the wavefront sensor.
An adaptive optics system in the mid-IR providing high spatial resolution for ground-to-air applications has been
designed at ONERA and is currently integrated. It includes an IR Shack-Hartmann wavefront sensor operating
on an extended source. This paper describes and justifies the design of the IR wavefront sensor. First images
and tests with the Shack-Hartmann wavefront sensor camera are presented.
HgCdTe (Mercury Cadmium Telluride / MCT) staring arrays for infrared detection do show constant improvements regarding their compactness and performances. New detectors are now proposed offering system solutions in the different IR wavebands and profiting of the latest technology improvements as well as MCT performance advantages and cost reduction. As a matter of fact, the size of MCT wafer has grown to 4", the pixel pitch was lowered to 15μm while maintaining outstanding results on the Focal Plane Arrays (FPA) uniformity. New functions as the Analog to Digital Conversion (ADC) are added to read-out circuits.
Results are presented concerning Non Uniformity Corrections (NUC) stabilities for two Sofradir products. Then results from developments of integrated ADC are addressed and finally, the Jupiter 1280x1024 mid-wave (MWIR) MCT detector performance results are presented.
The purpose of this paper is to present the latest developments in Defir (LETI / Sofradir joint laboratory) in the field of bi-color and dual band infrared focal plane arrays (FPA) made with HgCdTe.
The npn structure is achieved using the Molecular Beam Epitaxy (MBE) technique, planar ion implantation, and both dry and wet etching steps. This back to back diode architecture that allows a perfect spatial coherence with a high field factor and large quantum efficiencies needs only one indium bump connection per pixel. This makes it possible to achieve small pitches (below 25μm) and opens the way to the fabrication of large FPAs (TV/4 to TV) with reasonable wafer sizes.
In this paper we present electro optical characterizations of 256x256 prototypes fabricated in Defir operating in two MWIR bands (3.1 and 5μm) with a pitch of 25μm that exhibit background limited performances together with a very high operability (above 99.9%) and NEDT below 22mK for integration time of only 0.5ms. In parallel an industrial product soon available from Sofradir has been developed with a 320x256 format and with a 30μm pitch operating in the same bands. This product exhibits the same operability and NETD as low as 15mK for an integration time as short as 1 ms. Finally, last results regarding 256x256 prototypes operating in MWIR/LWIR bands are presented, together with preliminary APD operating mode for the MWIR photodiodes of this last dual band detector.
CLOUDS is a project co-funded by the EC under FP-4 (Environment and Climate), conducted by 12 European partners (7 scientific institutes and 5 industrial companies), also cooperating with NOAA/ETL. It is the mission study of a monitoring satellite to perform measurements necessary to describe cloud-radiation interaction in operational models for climate and long-term weather prediction. Complementary to missions for process study (Picasso-Cena, CloudSat, .. . ), CLOUDS addresses the monitoring aspect. As such, it has to comply with requirements of sufficiently frequent observing cycle, and operational sustainability. This prevents using active systems (radar and lidar) and leads to consider passive radiometry only, however exploiting as much as possible of the e.m. spectrum, with more polarisations and more viewing geometries. The paper reports on the instruments and system concepts developed to comply with the mission requirements. Six instruments are described, operating, respectively, in narrow channels of the UV/VIS/NIRISWIR, the TIRIFIR, the Sub-mm waves and the MW, in broad-band channels from UV to FIR, and in a relatively large-band channel of VIS/NIR. Several channels have three or four polarisations, all take images fore- and aft- (conical scanning), one has multi-angle-viewing capability. The overall system size is estimated as 900 kg mass, 1600 W power, 1 .1 Mbps data rate for real-time S-band transmission and 30 Mbps data rate for global data recovery in X-band.
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