The ALADIN Transmit-Receive Optics (TRO) for the Space-borne ADM Aeolus Wind Lidar Mission

摘要

This paper describes the design of the so-called Transmit-Receive Optics (TRO) for the Aladin lidar instrument on the future ADM Aeolus weather satellite. The TRO as the central optical unit of the Aladin instrument feeds the optical signals from the laser source to the emitting/receiving telescope, and vice versa, the received back scattered signals from the telescope to the spectrometers for Doppler shift evaluation. Additionally, a calibration branch is supported, which bypasses the telescope (from the laser to the spectrometers) and aims at levelling out the received signals in terms of wavelength and signal height changes due to wavelength and intensity variations of the laser. The TRO makes use of refractive optics (lenses) to a high extend taking advantage of the fact, that the spectral range of the Aladin instrument is narrow (centred at 354.8 nm). The opto-mechanical concept of the TRO features afocal optical groups, which are connected by parallel beams. Extreme requirements have been defined for the TRO on the end-to-end transmission (>= 73 %) with an associated effective bandwidth of less than 1 nm over the 200 - 1100 nm spectral range. A solution to these stringent requirements is addressed in this paper. A further feature of the TRO are two so-called aberration generators on the emitting and calibration branch, with which an artificial astigmatism can be realised for eye safety reasons. A three lens configuration has been designed for the aberration genertor. Its effect on astigmatism is presented. This article also addresses the effort on stray light suppression, which is of high importance for the TRO. The qualification of optical coatings, the integration and test philosophy for the TRO concludes this paper.