October 16-18, 2012Working Group on Space-based Lidar Winds 1 AEOLUS STATUS Part 1: Design Overview

October 16-18, 2012Working Group on Space-based Lidar Winds 2 Outline of the presentation Introduction to ALADIN Laser transmitter (TXA) specification Overview on the Laser optical design Overview on the Laser thermo-mechanical design

October 16-18, 2012Working Group on Space-based Lidar Winds 3 Wind measured by Doppler shift of backscattered light Single line-of-sight of horizontal wind (HLOS) Sun-synchronous orbit Random error: < 2 m/s Zero wind bias < 0.4 m/s ALADIN Measurement Geometry

October 16-18, 2012Working Group on Space-based Lidar Winds 4 ALADIN Measurement principle Doppler shift of backscattered light vs laser pulse Aerosols signal (Mie) predominant at low altitude (< 2kms) Molecules (Rayleigh) predominant at higher altitude (> 2 kms)

October 16-18, 2012Working Group on Space-based Lidar Winds 5 ALADIN Optical Functional Diagram RSP principle

October 16-18, 2012Working Group on Space-based Lidar Winds 6 T/R Optics Rayleigh Spectrometer Detection Front-end Chopper Receiver Equipments

October 16-18, 2012Working Group on Space-based Lidar Winds 7 ALADIN Instrument Overview

October 16-18, 2012Working Group on Space-based Lidar Winds 8 Instrument Core

October 16-18, 2012Working Group on Space-based Lidar Winds 9 The ALADIN laser Transmitter (TXA) ParameterRequirements Energy/pulse> Hz PRF Wavelength Polarisation 355 nm Linear, better than 100:1 Beam diameter Output divergence 7.5 mm < 400  rad full angle Pulse duration< 100 ns FWHM Pulse linewidth< 50 MHz FWHM Spectral purity99% of pulse energy within 90 MHz Frequency stability< 4 MHz rms over the observation time Tunability+ 7.5 GHz for initial adjustment + 5 GHz in calibration mode (25 MHz steps, 250 MHz steps) Tuning accuracy< 1 MHz over 28 min (noise) < 1.7 MHz rms over 28 min (slow drift)

October 16-18, 2012Working Group on Space-based Lidar Winds 10 The ALADIN Laser Transmitter (TXA) The ALADIN Laser transmitter is a Nd:YAG Q-switched Master Oscillator Power Amplifier (MOPA), frequency tripled & Injection-seeded. It operates in Continuous Mode with a PRF of 50 Hz The injection-seeding principle is based on the Ramp- Hold-Fire

October 16-18, 2012Working Group on Space-based Lidar Winds 11 The ALADIN TXA Functional Block Diagram

October 16-18, 2012Working Group on Space-based Lidar Winds 12 Injection + Master Oscillator section 5 mJ IR energy 1 1/e 2 Rod Q-Switch Polarizer

October 16-18, 2012Working Group on Space-based Lidar Winds 13 Amplification Section Input Energy 5 mJ st pass Output Energy ~50 mJ 2 nd pass Output Energy 130 mJ 3 rd pass Output Energy 350 mJ (IR)

October 16-18, 2012Working Group on Space-based Lidar Winds 14 Harmonic section 350 mJ IR Energy 150 mJ UV Energy 200 mJ IR + VIS

October 16-18, 2012Working Group on Space-based Lidar Winds 15 Laser Opto-Thermo-Mechanical Design description

October 16-18, 2012Working Group on Space-based Lidar Winds 16 Reference Laser Head (RLH) Based on two Non Planar Ring Oscillators (monolithic design ensures high stability) The Reference Laser is stabilized to a low drift resonator The beat signal between seeder laser and reference laser is processed by a digital PLL (frequency locking loop) The seeder beam is injected in a monomode fiber connected to the PLH

October 16-18, 2012Working Group on Space-based Lidar Winds 17 Power Laser Head (PLH) Optomechanical Layout

October 16-18, 2012Working Group on Space-based Lidar Winds 18 Power Laser Head (UOB + LOB)

October 16-18, 2012Working Group on Space-based Lidar Winds 19 Upper Optical Bench (UOB) of the PLH

October 16-18, 2012Working Group on Space-based Lidar Winds 20 Master Oscillator (MO) Cavity length is folded by 4 mirrors mounted on an Invar plate The output coupler, the cavity end mirror (on the rod) and the Invar plate are mounted on the UOB The piezo-actuator holds the output coupler Invar plate Rod & R Max

October 16-18, 2012Working Group on Space-based Lidar Winds 21 Pump unit (1) Zig-Zag Nd:YAG slab Laser diode pumped in front of the beam TIR for efficient optical energy extraction Slab TIR coating LIDT about 100 MW/cm W Laser Diodes Stacked Array derated power ( ~700 W) Typical lifetime shots LD1 LD3LD5LD7 LD2LD6LD4LD8

October 16-18, 2012Working Group on Space-based Lidar Winds 22 Pump Unit (2) The pump unit (PU) is made in copper Conductively cooled unit ( with thermal filler to minimize air-vacuum transition effect) 50 Hz About 200 W average Heat dissipation PU longitudinal cross section

October 16-18, 2012Working Group on Space-based Lidar Winds 23 PUMP UNIT (3) Pre-Amp PU installed on the UOB

October 16-18, 2012Working Group on Space-based Lidar Winds 24 Harmonic Generation LBO crystals used for SHG (25mm) and THG (35mm) Type I Phase Matching for SHG, Type II Phase Matching for THG Heater controlled crystal temperature higher than 30 o C

October 16-18, 2012Working Group on Space-based Lidar Winds 25 UOB Power Laser Head (PLH)

October 16-18, 2012Working Group on Space-based Lidar Winds 26 LOB Power Laser Head (PLH)

October 16-18, 2012Working Group on Space-based Lidar Winds 27 Pump Laser Diodes operation The heat current will be adjusted according to the formula: to keep constant the distribution of absorbed pump energy in the Nd:YAG rod and slab (same heat laser diode => same emission wavelength)