METimage Visible and Infrared Detectors End to End Co-Alignment Verification at Cryogenic Subsystem Level

METimage is a cross-purpose, multi-spectral optical imaging radiometer for meteorological applications. It measures thermal radiance emitted by the Earth and solar backscattered radiation in 20 spectral bands from 443 to 13345nm with one visible and two infrared detectors accommodated on the Cryogenic Subsystem. One of the key requirements of the instrument is the pointing and spatial co-registration of the infrared and visible detectors, mainly achieved at subsystem level. This paper presents the challenging development and verification approach of this subsystem until delivery of the first Proto-Flight Model end of 2022. The whole sequence had to be drastically adapted because of major programmatic constraints with the target to achieve the detectors co-alignment at the first attempt. The selection method used to re-visit the development risks after the withdrawal of the Engineering Model by shuffling the verification and qualification activities on the Structural-Thermal Model and the introduced Proto-Flight Model is enlightened in details: First, the maximized use of heritage technologies and the early verification by test of innovative design features for a subsystem accommodating both cold and warm optics are described. Afterwards, a specific focus is put on the achievement of the co-alignment requirement with the basis alignment using a smart alignment breakdown of the components reference focal planes. It provides a flexible parallel integration of the warm and cold optical assemblies to cope with another constraint: the late delivery of a central optical part. Finally, the cryogenic co-alignment verification approach in the Vacuum Chamber is described from detectors data generation using dedicated electronic and Optical Ground Support Equipment until image post processing and detectors spatial localization. The full multi-disciplinary engineering activities, development and testing have been performed at Airbus Defence and Space premises in Friedrichshafen. METimage is a German Space Agency (DLR) Customer Furnished Instrument for the EUMETSAT MetOp-SG Satellite A.