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FM FPU Subunits

FM FPU Subunits. A. Poglitsch. 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

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FM FPU Subunits

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  1. FM FPU Subunits A. Poglitsch PACS FPU Subunits

  2. 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. Performance of FPU and Subunits (II) • Filters • In-band transmission • Out-of-band suppression • Calibration Sources • Absolute emissivity • Homogeneity PACS FPU Subunits

  4. 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. 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. ± 0.5 arcsec on sky 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 PACS FPU Subunits

  7. 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. 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. 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 PACS FPU Subunits

  10. Filters: “Red” Photometer PACS FPU Subunits

  11. Filters: “Green” Photometer PACS FPU Subunits

  12. Filters: “Blue” Photometer PACS FPU Subunits

  13. Filters: “Red” Spectrometer PACS FPU Subunits

  14. Filters: “Green” Spectrometer PACS FPU Subunits

  15. Filters: “Blue” Spectrometer PACS FPU Subunits

  16. 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) QM QM CS2 CS1 PACS FPU Subunits

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