AEROSPATIALE, leading a European team, has just conducted a successful study, under ESA contract, to demonstrate the feasibility of a spaceborne Doppler Wind Lidar instrument meeting the scientific requirements of wind velocity measurements from space with high spatial resolution.A first parametric investigation, based upon the initial set of mission requirements, and supported by dedicated models and detailed trade-off studies, took account of capabilities of most promising signal processing algorithms and calibration/validation constraints: it yielded a large conically scanned instrument deemed technologically risky.A risk analysis was then carried out to propose a less challenging instrument meeting most key mission requirements. The fixed line-of-sight concept with return signal accumulation appeared as most attractive. A second set of requirements agreed upon by scientific users was therefore issued, with relaxed constraints mainly on horizontal resolution, keeping roughly the same level of wind velocity measurement accuracy. A second instrument and subsystem trade-off was then performed to eventually produce an attractive instrument concept based upon a pair of small diameter telescopes each one associated to one scanning mirror rotating stepwise around the telescope axis, which drastically reduces the detection bandwidth.Following the main contract, studies of accommodation on the International Space Station have been performed, confirming the interest of such an instrument for wind measurements from space.
This paper describes the development, characterisation and environmental testing of a high performance state-of-the-art optical filter for separating the Mie and Rayleigh backscatter signals for the ATLID LIDAR of the EarthCARE mission. The filter assembly utilises capacitance stabilised Fabry-Pérot étalon technology to provide high resolution optical filtering of the LIDAR signal, efficiently separating the two critical backscatter components from the atmosphere. The paper describes the development of the filter assembly and its subsequent performance testing. The filter has demonstrated state-of-the-art optical performance. Additionally, one of the étalons has been taken through complete environmental testing for space applications.
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