Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 1 PACS Test Facility Capabilities – Cryogenics and OGSE Gerd Jakob Future Tests:

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 2 Overview: Test Facility Status for PACS FM ILT The set-up is basically as described in PACS Cryo Test Equipment and OGSE Specification, PACS-ME-DS-002, Issue 1.1 (Status of CQM). -> Document to be updated to FM status comprising following revisions: Test cryostat: windows and filters Test optics: design features and alignment upgrade H2O vapour cell: new design External blackbody: improvements Point source masks:status New molecular FIR laser source at LENS: first results Test equipment:schematic

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 3 Test cryostat (OGSE 3) TC is equipped with 2 windows: –Window 1, diameter 25mm: integr. sphere entrance –Window 2, diameter 85mm: external focus entrance Both windows are either equipped with: –Quartz glass for optical alignment verification tests: Transmission T~76% for λ>35μm Or with: –PE foil, 1mm thick, for FM ILT: Transmission T~80% for λ>35μm Window 1 is equipped with: –A manually operated cryo-shutter at ~90K with 2 positions: A) open (T=100%) at reference position 0 mm B) closed (T=0%) at reference position 30 mm Window 2 is equipped with: –A manually operated cryo-shutter at ~100K with 3 positions: A) FL_E-filter, T~85% for λ>52μm + quartz glass, 0.5mm thick, T~76% for λ>35μm at reference position 8.5 mm B) closed (T=0%) at reference position 98.5 mm C) quartz glass, 0.5mm thick, T~76% for λ>35μm at reference position mm –2 fixed filters in series at ~6K (each 2 μm thick mylar foil + Incornel coating): Transmission T~2.4% for λ>35μm, respectively T~0.58% for both filters Window 1 Window 2 Test cryostat temperature levels: L0 ~ 1.6K for ~7 days (13 LHe tankful) L1 ~ 4.8K for ~2 days (70 LHe tankful)

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 4 Test optics design Principal design unchanged to CQM ILT phase 2 cryogenic blackbodies (BB): –Temp. range: 5K – 80K –Absolute temp. accuracy: +/- –Thermal stability: –Power dissipation: 1 integrating sphere w. light cone 1 external focus access 2 flip mirrors for optical path selection (internal or ext. sources) 1 chopper wheel to chop between BB1 and BB2: f 7 Cernox temperature sensors

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 5 Test optics alignment (1) Complete new optical alignment verification started for FM campaign TO internal alignment complete: optimized imaging qualities and target positions achieved with no vignetting : –BBs and integrating sphere centered on Lyot stop to 1% of diameter each BB2BB1 Ext.focus entrance (window2) Int.sphere entrance (window1) Test optics PACS FPU Test cryostat

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 6 Test optics alignment (2) Internal and external focus positions verified by use of LED array: –best focus at +/-1mm from design value –Transverse position good to +/-0.2mm Image quality: –< 3 µm wave front error (  PACS) –field distortion less than 1 blue photometer detector pixel for the total chopped PACS field of view Test optics imager 1 and imager 2 with LED array in telescope focus position and target in external focus position IM2 Ext. focus target IM1 LED array

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 7 Test optics alignment (3) 1 st cryogenic optical alignment verification test at 5 Kelvin successfully performed Cryostat equipped with test optics, PACS mass and optical focus dummy Autocollimator telescope with digital camera aligned with cryostat Additional prism optics mounted to observe through both windows simultaneously 2 nd cryogenic reproducibility test planned for June / July Preliminary results (after 1 st run): –Stability (300K / 5K) of test optics axis relative to optical bench + PACS dummy: ~ 0.1 mm in Y and Z direction (position) < 30” angular –Stability (300K / 5K) of test optics + cryostat optical bench relative to external window flange: ~ 1 mm in +Y direction ~ 4 mm in -X direction (uncritical) < 20” angular –All measured values within design specs. Autocollimator telescope (ACT) aligned with test cryostat, test optics and reference prism optics ACT Prism optics cryostat with test optics, PACS mass and optics dummy

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 8 H 2 O vapour cell New design with imaging optics, covering the complete chopped PACS field of view: –Ceramics heater with T=800K –Thermal stability ~+/-1K –Settling time ~1min –Cell will be equipped with (only) 1 PE window (instead of 2 compared to CQM ILT) –Gap between cell and cryostat vented with dry N2 gas –Temperature und pressure data available for housekeeping system Expected improvement (compared to CQM ILT): –10% deep lines relative to measured continuum for saturated H2O –Improved line contrast of factor ~2-3 Available for FM ILT to be mounted at test cryostat window 2 position (external focus entrance)

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 9 External Blackbody Improved design with well defined pin holes (point sources) in a black painted surface (no structures) Available pin holes diameters: 0.45 / 0.7 / 1.0 / 1.5 / 2.0 / 4.0 / 10.0 / 15.0 / 25.0 mm Temperature range 300K – 1000K Thermal stability +/-0.25K X/Y-stage position reproducibility <20 μm 30-50% improvement of contrast (comp. to CQM ILT) by implementation of N2 gas environment Design description in PACS-ME- DS-003 will be updated External blackbody mounted on X/Y-stage at test cryostat window 2

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 10 Point source masks Design description unchanged from CQM ILT See document PACS-ME-DS-003 issue 1 ‘OGSE External Point Source Mask Specification’ Hot plate temperature up to 600K All available hole patterns at their nominal positions in the FOV: New: 30-50% improvement of contrast by implementation of N2 gas environment Hot plate assembled with X/Y-stage at test Cryostat window 2

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 11 New Molecular FIR Laser Source at LENS (OGSE 4) LENS is building a new molecular laser system: –CO2 pump laser with ~10 Watts output power; bandwidth 1 MHz –FIR output power typically mW for ‘strong lines’ and μW for weaker lines –Bandwidth for a FIR line ~ MHz –Basic FIR lines are covering the PACS spectral wavelength range In early May 2006 a performance demonstration at LENS in a pre-test with MPE’s PACS detector set-up was successful: –Two available lines were detected: μm and μm For the FM ILT (Sept-Oct) the final FIR source will be shipped to MPE to be installed with the cryostat optics Optical bench with CO2 laser and FIR laser source during pre-test with PACS detector module (integrated with blue test dewar) CO2 FIR Det. dewar

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 12 New Molecular FIR Laser Source at LENS Initial FIR methanol laser wavelengths for PACS spectral calibration test; further lines are feasible after successful technical upgrade of the laser system

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 13 FIR laser lines, PACS RSRF and 0.5m air transmission

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 14 New Molecular FIR Laser Source, beam input for FM ILT As successfully demonstrated during the pre-test two different optical set-ups are feasible for PACS FM ILT: –homogenous array illumination with FIR source and integrating sphere optics –single (or multi) pixel illumination with FIR source via external focus entrance (point source) –‘point source’ motion across the slicer Improved air transmission feasible by installation of N2 gas vented light pipe optics Laser power monitoring by EGSE suggested

Herschel Space ObservatoryPACS Science Verification ReviewMPE 22/23 June 2006 GJ / MPE 15 ILT Test Equipment Schematic