anand sivaramakrishnan space telescope science institute peter tuthill, anthony cheetham
DESCRIPTION
A Back-up Method for Coarse Phasing JWST - Operational Considerations possible with any/all of NIRCam LW, NIRCam SW, NIRISS, MIRI. Anand Sivaramakrishnan Space Telescope Science Institute Peter Tuthill, Anthony Cheetham University of Sydney Scott Acton Ball Aerospace Alexandra Greenbaum - PowerPoint PPT PresentationTRANSCRIPT
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A Back-up Method for Coarse Phasing JWST - Operational Considerations
possible with any/all of NIRCam LW, NIRCam SW, NIRISS, MIRI
Anand SivaramakrishnanSpace Telescope Science Institute
Peter Tuthill, Anthony CheethamUniversity of Sydney
Scott ActonBall Aerospace
Alexandra GreenbaumJohns Hopkins University
Ed NelanSpace Telescope Science Institute
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A long time ago in a galaxy far, far away.…
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…the big one near the Andromeda, you know the one, they’re almost
twins
Milky Way, Sun, Earth, Hawaii, Keck telescope, 2007…
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Mid-Infrared Segment-Tilt `Masking’: 9-segment pattern
Peter Tuthill
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Mid-Infrared Segment-Tilting: Raw Data
CCD Chip
Peter Tuthill
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Ireland, Monnier & Tuthill ApJ 2007
23% of 1-1.5 Msun have companion with log(P)=4 – 6.5
Total accretion one to a few Mjup (3Mjup)
Birth rate = 0.25 x death rate. Therefore MiraAB type systems about as common as YSOs
1st Mid-IR Sparse-Aperture results:Rebirth from the Ashes
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Fizeau Interferometric Cophasing of Segmented Mirrors
precomputed look-up tables from detector data
Three NRT’ed segments
Perfect
Piston errors
Piston and tilt errors
Cheetham, Tuthill, Sivaramakrishnan & Lloyd Optics Express 2012
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FICSMFizeau Interferometric Cophasing of Segmented Mirrors
Segment tilting – choose non-redundant patterns NRT
Recover segment piston (few nm) & tip-tilt (10mas)
Capture range >150 micron pistons, 0.5 arcsec tilts (NIRCam LW)
Should work on NIRISS/NIRCamLW/NIRCamSW/MIRI
Cheetham, Tuthill, Sivaramakrishnan & Lloyd Optics Express 2012
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JWST Commissioning
8Exit gate: no segment deviates in piston from PM segments’ mean by > 150nm
DHS – coarse phasing baselineFICSM – coarse phasing backup
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PSFS during commissioning?
9Contos et al. 2006 SPIE
d e f
a b c
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Image Stacking process
10Acton et al. 2006 SPIE
Baseline: move all segments to a single STACK CENTERLarge moves inaccurate small moves accurateMust guide during this process
Ball Testbed Telescope data
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Image Stacking before Coarse Phasing
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segment images moved to fall at a common location on one detector - “Stack Center”
Large moves inaccurate, small moves accurate
Not ITAR-restricted information
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FICSMOptics Express 2012
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Coarse Phasing with Non-Redundant Tilts and FICSM
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Instead of stacking all segments at same location, separate them into NRT’ed sets, use FICSM on them to phase them (images in 3 filters yield pistons + tilts)
3 applications of FICSM to sets of NRT’ed segments
If you want details…
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Keck – 36 segments, atmospheric blur determines separation of NRT sets on detector (few to several arcsec)
JWST – 18 segments, /segmentDia determines separation of NRT sets on detector (½ - 1 arcsec)
A scaled down Keck-type segment tilting approach works well for JWST
Shorter baselines mitigate against higher vibration during JWST commissioning
Seed segments and first guiding segments on backplane (not wings)
JWST-STScI-002527 on NRT (Sivaramakrishnan & Acton)
Tests at Ball Testbed Telescope planned (Acton, Greenbaum, Sivaramakrshnan, Cheetham, Tuthill)