PACS SVR 22/23 June 2006 PACS FPU Subunits1 FM FPU Subunits A. Poglitsch.
-
Upload
brooke-jenkins -
Category
Documents
-
view
221 -
download
0
Transcript of PACS SVR 22/23 June 2006 PACS FPU Subunits1 FM FPU Subunits A. Poglitsch.
PACS FPU Subunits 2
PACS SVR 22/23 June 2006
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)
PACS FPU Subunits 3
PACS SVR 22/23 June 2006
Performance of FPU and Subunits (II)
• Filters– In-band transmission– Out-of-band suppression
• Calibration Sources– Absolute emissivity– Homogeneity
PACS FPU Subunits 4
PACS SVR 22/23 June 2006
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
PACS FPU Subunits 5
PACS SVR 22/23 June 2006
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
PACS FPU Subunits 6
PACS SVR 22/23 June 2006
Chopper
• Mirror optical performance– Flatness < 150 nm tested; failed but
accepted– Roughness < 50 nm tested; passed – Reflectivity > 98% by verified coating process
• Actuator performance (static/dynamic)– Range observation ± 4.1°; accuracy ± 1 arcmin tested;
ok– Duty cycle observation @ 10 Hz >80% tested;
ok– Range calibration ± 9°; accuracy ± 2 arcmin tested;
ok– Duty cycle calibration >70% tested; ok± 0.5 arcsec on sky
PACS FPU Subunits 7
PACS SVR 22/23 June 2006
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
PACS FPU Subunits 8
PACS SVR 22/23 June 2006
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
PACS FPU Subunits 9
PACS SVR 22/23 June 2006
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