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QinetiQ
Chris Dorn
Lightweight optics for Extreme UV Spectrometer
9 July 2002
Medium Wave Infra Red (MWIR)
Space Telescope
Pushing technology harder
MWIR
Railway and station
3
M1
Pixels: 35m
A5(T)
Grand Union Canal
Dead Pixels
Orbit: 450 x 1750km, 69°
Milton Keynes 12th
August 2000 14:42 UTC
Level 2 processing;
stagger bar re-sampling
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TopSat
A new chapter in optical missions
Rutherford
Appleton
Laboratory
5
TopSat - overview
• 2.5m target resolution,
panchromatic baseline + 3 band
colour at 5m
• 15% system MTF, 50:1 SNR
• 15km FoV
• 1 year mission life
• Near real time operations
• In-theatre demonstration
• Launch planned 2004
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6
Lightweight Optics
• Variety of materials tested
• Carbon fibre selected, due to:– High specific stiffness
– “Controllable” CTE
– Low cost
– Relatively simple process
• Coatings technologies
– Durable
– Polishable
• Zerodur 24 x 28cm, 4300g
• CFC 28cmØ, 250g
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7
Results
• Interferogram of:-
– “flat” CFC mirror
– unpolished
• The Spherical Mirror is
– more accurate
– has been polished
• ~5.6 kg/m2
– Topsat 164 kg/m2
– Hubble 180 kg/m2
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ALCAMIST
(Adaptive Lightweight CArbon MIrror SysTem)
9
ALCAMIST
• Faraday Partnership project,
Smart Optics
• 55cm adaptive mirror
• CFC faceplate
• 19 actuators
• Greater understanding of:– CFC mirrors
– Manufacturing issues
– Practical problems
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Timeline
Now
1995
1997
1999
2001
2003
Launch
2005
2007
2009
2011
EUS
Phase B
start
MWIR
ALCAMIST
LW mirrors
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11
Post Meeting Notes/Comments
•
Following our attendance at the Cosener’s House meeting, several issues, questions, actions and comments arose:–
Some further work is recommended to define the physical dimensions of the science module, so that only viable
optical designs are investigated.
–
Further work is recommended on the realistic electrical noise environment within the detector and ADC (including
quantisation noise). By setting an acceptable signal to noise ratio, the suitability of optical designs can be
evaluated.
–
Consideration should be given to novel observation strategies that are limited by the data transfer and instrument
power limitations, while simplifying the thermal management situation. Eg. looking away from the sun or use a
shutter to reduce solar input.
–
The operating temperature range for a “typical” carbon fibre (eg. EX1515/M46J) has been qualified for space at
+120°C to -170°C. Our materials specialists suggest that +200°C is probbaly achievable with that resin/matrix
system, however, they have not been tested at such temperatures. The advatnageof composite materials is that
the resin and matrix can be selected for the expected conditions and several alternative resin/matrix systems are
available that have been tested to significantly higher tempeatures. The ALCAMIST technology allows a mirror to
be adjusted over this temperature range, hence maintaining optical requirements. A short test programme to
demonstrate this and suitable coatings would ensure that this technology was available for consideration in the
design.
–
With optical systems, there are 2 main design routes; fixed and adaptive. Engineering a “fixed” optical system (on
a 2m scale) that remains within tolerance over such a wide operating temperature range and within a realistic
mass budget is extremely risky. By following the adaptive or “smart structure” route, the changes in the optical
system can be sensed and corrected. This trades mass for technical complexity, but careful selection of mature
technologies will minimise this. An ALCAMIST style mirror can also provide the raster scan function.
–
My contact details; [email protected]
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