Transcript Instrumentation Cost Drivers

NGAO Instrumentation
Cost Drivers and Cost Savings
September 2008
Sean Adkins
What drives science instrument costs?
• All designs are relatively lean already
• Suspected cost drivers:
– Technical difficulty
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d-IFS probe arm accuracy and stability
Near-IR and Visible coronagraphs
Visible IFU
Internal wavefront error control for all instruments
Calibration and alignment (pupil registration, etc.)
– Pixel sampling and FOV (detector size)
– Number of d-IFS channels
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What can save cost?
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Keep the imagers simple
– Resist the temptation to ask for more than one plate scale
– Accept that imagers do not offer spectroscopy
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Accept higher static instrumental wavefront error
– Design instrument to optimize performance of wfe measurement
– Allocate some DM stroke to correcting static instrumental wfe
– Incorporate some other correction technique?
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Evaluate the possibility of putting the coronagraph in the AO system
– Hard to do for both wavelength ranges
– Compounds the alignment difficulties – need imager to align coronagraph? ( may
imply coronagraph belongs in instrument)
– May not or won’t work for near-IR (needs to be cryogenic)
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Stripper imagers
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Just detectors and filters
No coronagraphs
Keep telecentric ~ f/46.5 narrow field relay but eliminate field curvature
Must put Lyot stop in AO system, still has to be cold for near-IR
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“Radical” Cost Saving Concept
• Standardized near-IR cryostat, camera, focal plane design used for
both the near-IR imager and each d-IFS spectrograph channel
• Common MOAO relay design for TT and d-IFS w/ 32 x 32 MEMS
• Eliminate narrow field relay
• Incorporate 64 x 64 MEMS in each imager and locate at “wide” field
relay/OSM plane
– Eliminates dichroic changer
– Include on instrument low order wavefront sensing
• Duplicate the narrow field MOAO relay (30" dia. FOV), but 32 x 32
MEMS for d-IFS, 3 d-IFS channels (post OSM) per MOAO relay
instead of 1
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