Wind Lidar Working Group, Miami 6 Feb Status Martin Endemann

Wind Lidar Working Group, Miami 6 Feb Aeolus mass is 1.1 t (plus fuel), the solar arrays are about 13 m wide to produce 2.2 kW (orbital average power 1.4 kW). It is compatible with small launchers (Vega, Rokot, Dneper). It carries a single payload, the Atmospheric LAser Doppler INstrument ALADIN. The satellite is designed for simple operation (7 day autonomy, 5 day unattended survival), repeating 7-day command cycles. Aeolus satellite with its ALADIN payload

Wind Lidar Working Group, Miami 6 Feb …and the Aeolus satellite bus Flight Model during integration testing at Astrium Germany, Friederichshafen Most subsystems have been integrated, Flight software is under testing

Wind Lidar Working Group, Miami 6 Feb ALADIN is the only payload of Aeolus. Its size is dominated by the large afocal telescope of 1.5 m diameter. It uses diode pumped Nd:YAG laser to generate UV-light pulses (355 nm) emitted to the atmosphere. Two transmitter laser assemblies (blue) and the receiver (yellow) are on the structure below the telescope. A large radiator (mounted on the satellite bus) is coupled with heat pipes to the transmitter lasers. Star trackers are mounted on ALADIN structure to give best possible pointing reference. Total mass is 480 kg, power 830 W. ALADIN Atmospheric Laser Doppler Instrument

Wind Lidar Working Group, Miami 6 Feb ALADIN optical layout Transmit/receive telescope: 1.5 m diameter, SiC lightweight structure (mass about 75 kg), thermally focused Transmit/receive optics: high stability optical design, polarizer as T/R switch, 1 focus for chopper location, 1 focus as field stop, background filter (1 nm equivalent bandwidth + prism for broad-band rejection Rayleigh receiver: Double edge etalons, sequentially illuminated, Outputs focused on single accumulation CCD Mie receiver: Fizeau interferometer, thermally stable design, Outputs collimated single accumulation CCD Transmitter laser assembly: Reference Laser Head with stabilized tunable MISER lasers seeding the Power Laser Head with low power oscillator, two amplifiers and tripling stage two redundant laser assemblies in ALADIN

Wind Lidar Working Group, Miami 6 Feb ALADIN transmitter laser (TXA) For single mode operation, the laser is injection seeded with output from a frequency stabilized cw Nd:YAG laser which is coupled via single-mode fibres to the power laser head. The laser is conductively cooled via heat pipes mounted on thermal interface plates. A diode pumped Nd:YAG laser is generating single frequency pulses at 355 nm wavelength with 120 mJ energy at 100 Hz repetition rate. It is operated in burst mode of 12 s on (5 s warm up, 7 s measurement), and 16 s off to increase life time and reduce power consumption.

Wind Lidar Working Group, Miami 6 Feb Engineering Qualification Model (EQM) has performed vibration test campaign, but with initial problems. However, these problems have been shown to come from external Ground Support Equipment, not the laser itself. Still, the sensitivity of internal laser alignment on external parts is unhealthy and has lead to a review of some design features… EQM has performed TV test campaign, but it needs to be repeated, probably due to a workmanship issue… Flight Model 1 has been integrated and initial tests show good performance. Laser has been closed and is presently undergoing full performance characterization. Dependent on results of design review, some retrofits will be introduced before delivery. ALADIN transmitter laser (TXA) status (1)

Wind Lidar Working Group, Miami 6 Feb ALADIN transmitter laser (TXA) the hardware Flight Model 1 of Power Laser Head during integration at Galileo Avionica, Pomezia (Italy) Dec 2006

Wind Lidar Working Group, Miami 6 Feb ALADIN transmitter laser (TXA) the hardware Flight Model 1 of Power Laser Head during integration at Galileo Avionica, Pomezia (Italy) Jan 2007

Wind Lidar Working Group, Miami 6 Feb ALADIN transmitter laser (TXA) status (2) Reference Laser Heads (RLH) Flight Model 1 has been delivered; FM 2 and FM 3 are in final testing – beautiful units from TESAT Transmitter Laser Electronics (TLE): FM1 completed, some retrofits required to improve communication to ALADIN Control Electronics

Wind Lidar Working Group, Miami 6 Feb Lifetime of pump laser diode stacks : After initial testing of various different commercial pump diodes, a manufacturer was selected (Nuvonyx-Europe, France) and Flight Model manufacturing initiated. Extended burn-in was performed to select best diode stacks for flight; lifetime testing is ongoing for final qualification (end Feb 07). Laser Induced Damage (LID) : Lifetime of high power optics is often limited by coating damage. Investigations have shown that damage threshold continues to decrease with the number of pulses fired. A power law has been assumed to extrapolate the damage threshold from a on-1 damage curve to end-of-life conditions (5 Gpulses). Laser Induced Contamination (LIC) : Outgassing of organic materials is known to generate absorbing layers on coatings, in particular in vacuum operation. Careful selection of materials and stringent cleanliness control are essential prerequisites for a long laser lifetime. ALADIN transmitter laser (TXA) status (3)

Wind Lidar Working Group, Miami 6 Feb ALADIN transmit/receive telescope Ultra-lightweight Telescope all in silicon carbide (SiC) Diameter: 1.5 m Afocal optics Mass complete: 75 Kg First frequency > 60 Hz Thermal re-focusing capability Wavefront error: 350 nm (complete telescope)

Wind Lidar Working Group, Miami 6 Feb status: completed and integrated with ALADIN Structure at Astrium Toulouse ALADIN transmit/receive telescope Flight Model

Wind Lidar Working Group, Miami 6 Feb ALADIN Transmit/Receive Optics (1) TRO combines the transmittter and receiver optical paths, carries the field-stop, background rejection filter and the laser chopper assembly, and the reference light path from transmitter to receiver. High stability and minimum wave front errors in a small compact unit are design drivers. In environmental testing right now.

Wind Lidar Working Group, Miami 6 Feb ALADIN Transmit/Receive Optics (2) Flight Model prepared for environmental testing, run by unit manufacturer Kayser-Threde at IABG, Munich.

Wind Lidar Working Group, Miami 6 Feb ALADIN Receiver Optics Rayleigh & Mie Spectrometers Rayleigh Spectrometer completed at Oerlikon Space AG (ex Contraves), and delivered to Astrium Toulouse. Mie Spectrometer under environmental testing

Wind Lidar Working Group, Miami 6 Feb ALADIN Receiver Optics Rayleigh & Mie Spectrometers Rayleigh Spectrometer completed with isostatic mounts before integration to Optical Bench Assembly at Astrium Toulouse

Wind Lidar Working Group, Miami 6 Feb Validation of Performance Models ALADIN Airborne Demonstrator A2D The pre-development model of the receiver and one of the breadboard lasers have been combined to a complete wind lidar to fit into the Falcon research plane from DLR together with the CTI 2-um wind lidar. Proving flights in the Falcon jet have been successfully completed in Oct An extended ground-based campaign with other lidars and conventional wind sensors has been completed in Oct Over 100 hrs of data have been collected and are being evaluated. However, transmitter laser has to be refurbished. Repeated proving flights planned for April First airborne campaign is planned for Sep 2007.

Wind Lidar Working Group, Miami 6 Feb Aeolus status summary First space mission to measure global wind profiles: new technology, new challenges Hardware manufacturing and integration is well advanced: Aeolus satellite bus mostly integrated, ALADIN structure/thermal/electronics hardware all available But the critical technologies do need time to chase the new Gremlins away… Launch in the mean time has officially been slipped to June 2009 Gilles Labruyére 2007