Status of Aeolus ESA s Wind Lidar Mission Roland Meynart, Anders Elfving, Denny Wernham and Anne Grete Straume European Space Agency/ESTEC Coherent Laser Radar Conference, Boulder 26 June-01 July 2016
Page 2 Atmospheric large-scale circulation
Aeolus: Mission Objectives Scientific objectives To improve the quality of weather forecasts; To advance our understanding of atmospheric dynamics and climate processes; Explorer objectives Demonstrate space-based Doppler Wind LIDARs potential for operational use. Observation means: Provide global measurements of horizontal wind profiles in the troposphere and lower stratosphere Payload ALADIN: Atmospheric LAser Doppler INstrument 3.
Aeolus: Measurement Principle Direct detection UV Doppler wind Lidar operating at 355 nm and 50 Hz PRF in continuous mode, with 2 receiver channels: Mie receiver (aerosol & cloud backscatter) Rayleigh receiver (molecular backscatter. The line-of-sight is pointing 35 o from Nadir to obtain horizontal backscatter component HLOS The line-of-sight is pointing orthogonal to the ground track velocity vector to minimize contribution from the satellite velocity. Spacecraft regularly pointed to nadir for calibration 4.
Mission characteristics Mission Parameters Orbit: sun-synchronous Mean altitude: ~400 km 320 km considered because of low solar activity Local time: 18:00 ascending node Inclination: 96.97 o Repeat cycle: 7 days / 111 orbits Orbits per day: ~16 Mission lifetime: 3 years 5.
ALADIN instrument 6.
Aeolus: Instrument Principle Doppler shift < 100 m/s Laser pulse Mie signal 30 m/s Rayleigh signal 600 m/s Mie channel: Aerosol/cloud backscatter Imaging technique Rayleigh channel: Molecular backscatter Double-edge technique 7.
Aeolus: Observational Requirements PBL Troposphere Stratosphere Vertical domain [km] 0-2 2-16 16-20 (30)* Vertical resolution 1 [km] 0.5 1.0 2.0 Horizontal domain Global Number of profiles [hour -1 ] >100 Horizontal track data availability > 95% Temporal sampling [hr] 12 Horizontal resolution / integration length 2 [km] 15 (target) 100 (threshold) Horizontal sub-sample length [km] km scale Random error (HLOS Component) [m/s] 1 2.5 3 (3-5)* Systematic error (HLOS component) [m/s] 0.7 0.7 0.7 Dynamic Range, HLOS [m/s] ±150 Error Correlation per 100 km < 0.1 Probability of Gross Error [%] 5 Timeliness 3 Length of Observation Dataset [yr] 3 1 24 atmospheric samples for Mie & Rayleigh channel with 0.25km minimum vertical resolution 2 L1B data: 90 km horizontal integration length * Desirable range 8.
Aeolus: ALADIN Instrument Transmitlasers Optical Bench Courtesy: Airbus DS 9.
Aeolus: ALADIN Laser Transmitter Master Oscillator with end-pumped Nd:YAG rod: pulses of about 5 mj energy at 1065 nm (PRF: 50 Hz). Two slab amplifiers generate about 350 mj Frequency tripling to 355 nm) in two LBO crystals with ~40% efficiency. Operation under a pressure of 0.6 mbar 10. Courtesy: Finmeccanica/Leonardo Harmonic conversion and UV beam optics
Aeolus: Highlights of Laser Test Experiences 2000-2004: - Laser Diode Reliability - Laser performance demo 2005: Laser Diode Performance 2012: LID on UV Optic Coatings 11.
Laser qualification (1) Both FM lasers delivered after qualification, omechanical oemc othermal vacuum oburn-in (6 weeks, > 200Mshots ) FM lasers further used in testing and still in good health. UV beam @ THG Inspection after 450 Mshots: no damage identified 12.
Laser qualification (2) Laser life test on the flight spare model (FM-C) started in February (continuation of the previous burn-in test). Duration: 6 months (780 Mshots) So far, the laser has run for 144 days corresponding to 630 Mshots The degradation measured internally by the laser UV photodiode is lower than 5 % External degradation due to LIC on surfaces exposed within the vacuum chamber Courtesy: Leonardo Other long term trends of laser parameters are being analysed 13.
Optical Bench Assembly (OBA) Courtesy: Airbus DS Rayleigh spectrometer side Mie spectrometer side 14.
Instrument integration Courtesy: Airbus DS First laser FM in instrument Integrated instrument before closure 15.
Integrated instrument 16.
Integrated instrument Courtesy: Airbus DS 17.
Instrument testing The optical test equipment is a key system to validate the instrument; Reception path to analyse the beam emitted by the instrument Emission path to generate a synthetic atmospheric echo (+background) Shape, amplitude and frequency of the atmospheric echo can be modulated 18.
Instrument full performance tests Tests at ambient pressure Validation of random error and some systematic errors Rehearsal of the vacuum performance test Detailed correlation analysis on-going, taking into account testing effects Random errors extrapolated from tests within 5% of expectations for Mie and Rayleigh channels Response slopes verified Endurance test on emission path show good stability 19.
Next steps Shipment to the satellite (Airbus D&S UK) Mid July Transport of spacecraft to test facilities end of 2016 Mechanical and thermal vacuum tests foreseen first half 2017 Mechanical tests in ITS (F): sine, acoustic and shocks Thermal vacuum test in CSL (B) Full performance test in vacuum in CSL (B) Flight readiness in 4 th quarter 2017 Courtesy: Airbus DS 20.
Another lidar in development: ATLID EarthCARE mission: Improve understanding of cloudaerosol-radiation interaction Payload: Cloud profiling Radar (JAXA), Multi Spectral Imager, Broad Band Radiometer, Atmospheric Lidar, Mission parameters Sun synchronous orbit, 393 km altitude, LTDN 14:00 Mass 2350 kg, power 1.7 kw, 3 yr lifetime Flight readiness: 4 th quarter 2018 21.
EarthCare / ATLID Bi-static architecture Complete separation of the emission path from the rest of the instrument to avoid cross-contamination LIC mitigation Full pressurisation of the emission path Reduction of laser fluence 22.
ATLID laser development 1st transmitter in qualification 4-week burn-in test completed - vibration test successfully passed, thermal vacuum test on-going 2 nd transmitter integration on-going Courtesy: Leonardo λ = 355 nm E = 38 mj @ 51 Hz 23.
Future laser (FULAS) New generation Nd:YAG laser developed Coordination with German national developments for MERLIN Cement-free design, welded housing 90 mj @ 100 Hz, 1064 nm O-O efficiency (IR): 20 % Courtesy: Airbus DS + ILT 24.
Conclusion 1. The Aeolus development has faced many challenges during the last 15 years, particularly for the laser transmitter 2. Invaluable experience has been gained 3. We believe we see the end of the road 4. The mission remains unique 5. We thank the community for their patience 25.
Thank you for your attention Visit us @ www.esa.int 26.