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Aeolus Satellite: ALADIN Atmospheric Laser Doppler Instrument

The Aeolus satellite, equipped with the ALADIN payload, is designed for atmospheric research. ALADIN uses a large telescope and lasers to study the Earth's atmosphere. This satellite is compatible with small launchers and has a simple operation.

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Aeolus Satellite: ALADIN Atmospheric Laser Doppler Instrument

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  1. Status Martin Endemann

  2. Aeolus satellite with its ALADIN payload 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.

  3. …and the Aeolus satellite bus Flight Model during integration testing at Astrium Germany, Friederichshafen Most subsystems have been integrated, Flight software is under testing

  4. ALADIN Atmospheric Laser Doppler Instrument 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.

  5. ALADIN optical layout Transmitter laser assembly:Reference Laser Headwith stabilized tunable MISER lasersseeding the Power Laser Headwith low power oscillator,two amplifiers and tripling stagetwo redundant laser assemblies in ALADIN 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 Mie receiver: Fizeau interferometer, thermally stable design, Outputs collimated single accumulation CCD Rayleigh receiver: Double edge etalons, sequentially illuminated, Outputs focused on single accumulation CCD

  6. ALADIN transmitter laser (TXA) 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. 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.

  7. ALADIN transmitter laser (TXA)status (1) 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.

  8. ALADIN transmitter laser (TXA)the hardware Flight Model 1 of Power Laser Head during integration at Galileo Avionica, Pomezia (Italy) Dec 2006

  9. ALADIN transmitter laser (TXA)the hardware Flight Model 1 of Power Laser Head during integration at Galileo Avionica, Pomezia (Italy) Jan 2007

  10. 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

  11. ALADIN transmitter laser (TXA)status (3) 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 10.000-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.

  12. 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)

  13. ALADIN transmit/receive telescopeFlight Model • status: completed and integrated with ALADIN Structure at Astrium Toulouse

  14. 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. ALADIN Transmit/Receive Optics (1)

  15. Flight Model prepared for environmental testing, run by unit manufacturer Kayser-Threde at IABG, Munich. ALADIN Transmit/Receive Optics (2)

  16. Rayleigh Spectrometer completed at Oerlikon Space AG (ex Contraves), and delivered to Astrium Toulouse. Mie Spectrometer under environmental testing ALADIN Receiver OpticsRayleigh & Mie Spectrometers

  17. Rayleigh Spectrometer completed with isostatic mounts before integration to Optical Bench Assembly at Astrium Toulouse ALADIN Receiver OpticsRayleigh & Mie Spectrometers

  18. Validation of Performance ModelsALADIN 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 2005. An extended ground-based campaign with other lidars and conventional wind sensors has been completed in Oct 2006. 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 2007. First airborne campaign is planned for Sep 2007.

  19. Aeolus statussummary 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

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