The design of a 50 Hz single longitudinal mode, diode-pumped and frequency-tripled Nd:YAG master oscillator power amplifier is described, and the first measurements of output parameters are presented. The laser oscillator is injection-seeded by a tuneable monolithic Nd:YAG ring laser and frequency stabilized by minimising the Q-switch build-up time. The laser system will be an integral part of an airborne instrument demonstrator for a first satellite based Doppler wind lidar to measure vertical profiles of one component of the atmospheric wind vector. This paper focuses on the investigation of the frequency jitter and the linewidth of the laser, which are measured on a pulse-to-pulse basis. For this purpose a compact, high accuracy beat frequency monitoring system has been developed at DLR. By operating the amplifier stage at half the repetition rate (50 Hz) of the oscillator, we could reduce the frequency stability from 10 MHz (rms) to 1.3 MHz (rms) (over a 14 s period). We have determined a mean linewidth of 15 MHz (FWHM) at 1064 nm. These measured laser parameters enable wind velocity measurements in the atmosphere (0-15 km) at an accuracy of 1 to 2 m/s.

We report on the design and performance of the laser deployed in the airborne demonstrator Doppler wind lidar for the Aeolus mission of the European Space Agency (ESA). The all-solid-state, diode-pumped and frequency-tripled Nd:YAG laser is realized as a master oscillator power amplifier (MOPA) system, generating 60 mJ of single-frequency pulses at 355 nm wavelength, 50 Hz repetition rate and 20 ns pulse duration. For the measurement of the Doppler frequency shift over several accumulated laser shots, the frequency stability of the laser is of crucial importance. Injection-seeding, in combination with an active cavity control based on the Ramp-Delay-Fire technique, provides a pulse-to-pulse frequency stability of 0.25 MHz measured at 1064 nm under laboratory conditions. This value increases to 0.31 MHz for airborne operation in a vibration environment that has been characterized by multiple acceleration sensors during different flight conditions. In addition, a pure Ramp-Fire setting was tested for comparison leading to a frequency stability of 0.16 MHz both in airborne operation and on ground. The laser cavity control electronics also have to provide a trigger signal for the lidar detection electronics, about 60 μs prior to the expected laser pulse emission and with high timing stability. An in-flight timing stability of below 100 ns was measured decreasing to 20 ns for a shorter pre-trigger time of 10 μs.

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The Methane Remote Sensing LIDAR Mission (MERLIN) is a joint French-German cooperation on the development, launch and operation of a climate monitoring satellite, executed by the French Space Agency CNES and the German DLR Space Administration. It is focused on global measurements of the spatial and temporal gradients of atmospheric Methane (CH4) with a precision and accuracy sufficient to constrain Methane fluxes significantly better than with the current observation network.Merlin is a LIDAR Instrument using the IPDA principle. This instrument principle relies on the different absorption of the laser signal by atmospheric Methane at two laser wavelengthson-line and off-line -both around 1.645 μm, reflected by the Earth surface or by cloud tops. The attenuation is strong at the on-line wavelength; the off-line "reference" wavelength is selected to be only marginally affected by Methane absorption. Being an active instrument with its own light source, the MERLIN LIDAR Instrument does not have to rely on sun illumination of the observed areas and can therefore continuously operate over the orbit.Airbus DS GmbH was selected by the German DLR Space Administration as the industrial Prime Contractor for the Mission Phase C/D, to build the MERLIN Payload, which is the first realization of such an instrument for space in Europe.This presentation will concentrate on the Architecture and the Design of the MERLIN Payload developed during the ongoing Mission Phase C. Further details of the instrument development status will be shown by an overview of the current hardware and design status of the major subsystems.