Transcript FPU Subunits

PACS SVR
22/23 June 2006
FM FPU Subunits
A. Poglitsch
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Performance of FPU and Subunits (I)
• Structure
– Temperature (stability) requirements
– Mechanical/optical tolerances, alignment
• Mirrors
– Optical performance
• Chopper
– Pointing accuracy
– Dynamic behaviour (duty cycle)
• Grating
– Optical performance of grating
– Mechanical performance of grating drive
• Precision of position readout/actuator; jitter
• Dynamic properties (scanning/dithering/frequency switching)
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Performance of FPU and Subunits (II)
• Filters
– In-band transmission
– Out-of-band suppression
• Calibration Sources
– Absolute emissivity
– Homogeneity
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FPU Structure
• Most (but not all) of the FPU structure has been used
in CQM
• Thermal requirements fulfilled by CQM as far as
tested – expect no changes with FM
– More detailed tests necessary w.r.t. sensitivity to L0/L1
interface temperature tolerances/variations
– Ge:Ga detector thermal interface changed for thermal curing
• LHe Optical Alignment Stability Test under way
– CQM ILT revealed no anomalies
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Optics: Mirrors
• All mirrors tested individually at ambient temperature
• Visible light end-to-end test
– Documentation with delivery of FPU
• No unexplained anomalies observed in QM
– But PSF measurements were hampered by telescope
simulator defocus
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Chopper
• Mirror optical performance
– Flatness
– Roughness
– Reflectivity
< 150 nm
< 50 nm
> 98%
tested; failed but accepted
tested; passed
by verified coating process
• Actuator performance (static/dynamic)
–
–
–
–
Range observation ± 4.1°; accuracy ± 1 arcmin
Duty cycle observation @ 10 Hz >80%
Range calibration ± 9°; accuracy ± 2 arcmin
Duty cycle calibration >70%
tested;
tested;
tested;
tested;
ok
ok
ok
ok
± 0.5 arcsec on sky
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Grating (I)
• Groove period - spec 117.65 (± 0.7) µm
– Only measured for CQM: g=117.66 ± 0.11 µm (2 sigma)
• Facet angles - spec 34.5° (± 1°) and 62.4° (± 1°)
– Average: 34.1846°; standard deviation: 0.3455°
– Average: 62.3264°; standard deviation: 0.4233°
• Groove regularity - spec 0.3 µm r.m.s.
– Not verified  search for grating ghosts in ILT essential!
– Positioning precision of machine used for ruling is 0.1 µm
w.r.t. reference (reference: Heidenhain glass ruler).
Measured ruler error (interferometric) over 100 mm travel:
0.15 µm (p-p); no measurement over full length available
• Groove depth - spec 56 µm ± 2 µm
– Not measured, but 0th order diffraction efficiency indicates
no major deviation of grating profile from spec
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Grating (II)
• Groove parallelism - spec ± 10”
– Each groove to each other: not verified, but hard to miss with
machine used for ruling
– Grooves to rotation axis: no absolute measurement done, but
grating drive wobble measured – uses up error entire budget!
Thorough test of position shifts and spectral shear/tilt as
function of grating angle during ILT required!
• Overall surface flatness - spec 3 (goal 1.5) µm r.m.s.
– Verification by WFE measurement with 10 µm interferometer
in three grating orders partly achieved (only partial coverage
of grating area by beam at a time); machining error <0.5 µm
(but internal stress in grating body could lead to deformation)
 Confirmation by measurement of PSF / spectral profile during
ILT
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Grating Drive
• Position precision within the useful angular throw:
8 arcsec (goal: 4 arcsec)
– Calibration certificate: ± 3 arcsec; ± 4 arcsec (nom.; red.)
• Grating position “jitter” shall be < 0.1 arcsec/√Hz
– verified by test
• Wavelength switching: amplitude of < 3 arcmin with
frequencies of < 3 Hz and a duty cycle of 80%
– verified by test
• Stabilization time for a grating step of 18 arcsec:
< 23 ms
– verified by test
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Filters: “Red” Photometer
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Filters: “Green” Photometer
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Filters: “Blue” Photometer
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Filters: “Red” Spectrometer
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Filters: “Green” Spectrometer
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Filters: “Blue” Spectrometer
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Calibration Sources
• No measurements of FM
CSs possible before FM ILT
• Cause of inhomogeneity in
CS1 illumination identified
in QM FPU; avoided in FM
FPU
• Emissivity adjusted
• Stability expected in spec
(similarity with QM)
CS2
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QM
CS1
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