Status
Martin Endemann
Wind Lidar Working Group, Miami
6 Feb 2007
1
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.
Wind Lidar Working Group, Miami
6 Feb 2007
2
…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 2007
3
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.
Wind Lidar Working Group, Miami
6 Feb 2007
4
ALADIN optical layout
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
Mie receiver:
Fizeau interferometer,
thermally stable design,
Outputs collimated single
accumulation CCD
Wind Lidar Working Group, Miami
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
6 Feb 2007
5
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.
Wind Lidar Working Group, Miami
6 Feb 2007
6
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.
Wind Lidar Working Group, Miami
6 Feb 2007
7
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 2007
8
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 2007
9
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 2007
10
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.
Wind Lidar Working Group, Miami
6 Feb 2007
11
ALADIN transmit/receive telescope
Sic secondary
mirror
Sic parts linking legs
and M2
Upper Strut Thermal
Protection
SiC legs with
tubular section
Titanium brackets
SiC Primary mirror
Titanium Isostatic
mounts
Wind Lidar Working Group, Miami
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)
6 Feb 2007
12
ALADIN transmit/receive telescope
Flight Model
status: completed and integrated with
ALADIN Structure at Astrium Toulouse
Wind Lidar Working Group, Miami
6 Feb 2007
13
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 2007
14
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 2007
15
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 2007
16
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 2007
17
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 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.
Wind Lidar Working Group, Miami
6 Feb 2007
18
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…
Gilles Labruyére 2007
Launch in the mean time has officially
been slipped to June 2009
Wind Lidar Working Group, Miami
6 Feb 2007
19