1. Page 1HMI/AIA Science Meeting – February 13, 2006 HMI Instrument Overview and Calibration Status HMI/AIA Science Meeting February 13, 2006 Jesper Schou HMI Instrument Scientist Stanford University jschou@solar.stanford.edu (650) 725-9826

2. Page 2HMI/AIA Science Meeting – February 13, 2006 Outline Instrument overview Calibration activities –Overview –Status Conclusion

3. Page 3HMI/AIA Science Meeting – February 13, 2006 Instrument Overview Optics package –Telescope section –Polarization selectors – 3 rotating waveplates for redundancy –Focus blocks –Image stabilization system –5 element Lyot filter. One element tuned by rotating waveplate –2 Michelson interferometers. Tunable with 2 waveplates and 1 polarizer for redundancy –Reimaging optics and beam distribution system –Shutters –2 functionally identical CCD cameras Electronics package Cable harness

4. Page 4HMI/AIA Science Meeting – February 13, 2006 Image stabilization mirror CCD fold mirror Fold mirror ¼ Waveplate ½ Waveplates Telescope lens set Telecentric lens Calibration lenses and focus blocks Front window filter Relay lens set Blocking filter BDS beamsplitter Narrowband Michelson Polarizer ISS beamsplitter and limb tracker assembly Tuning waveplates Beam control lens Lyot Wideband Michelson CCD Shutter assemblies Aperture stop Instrument Overview – Optical Path Optical characteristics: Focal length: 495 cm Focal ratio: f/35.2 Final image scale: 24  m/arcsec = 0.5”/pixel Primary to secondary image magnification: 2 Focus adjustment aange: 16 steps of 0.4 mm Filter characteristics: Central wavelength: 613.7 nm FeI Front window rejects 99% solar heat load Final filter bandwidth: 0.0076 nm Tuning range: 0.069 nm All polarization states measurable

5. Page 5HMI/AIA Science Meeting – February 13, 2006 Observing Scheme Observables –Dopplergrams –Magnetograms, vector and line of sight –Others: Intensity, line depth, etc. Observables made from filtergrams described by framelists Filtergram properties –Wavelength and polarization state –Exposure time, camera ID and compression parameters, … Framelists –Fixed list of filtergrams repeated at fixed cadence during normal operations –Entirely specified in software – highly flexible

6. Page 6HMI/AIA Science Meeting – February 13, 2006 Observables Calculation Make I, Q, U, V, LCP, RCP –Linear combinations of filtergrams –Correct for flat field, exposure time and polarization leakage –Correct for solar rotation and jitter (spatial interpolation) Sun rotates by 0.3 pixels in 50s, so interpolation necessary Fast and accurate algorithm exists –Correct for acceleration effects (temporal interpolation) Nyquist criterion almost fulfilled for Doppler and LOS but is violated for vector measurements Significant improvement from interpolation and averaging –Fill gaps Data loss budget gives missing data in every filtergram, various algorithms exist May do nothing for vector field Calculate observables –MDI-like and/or least squares for Doppler and LOS –Fast and/or full inversion for vector field Many challenges remain –Calibration, code development, lists of dataproducts etc. –Community input needed!

7. Page 7HMI/AIA Science Meeting – February 13, 2006 Calibration Activities - Overview Individual items Assemblies Assembled instrument –First Sun test Instrument partially finished Warm, so camera noise is high –In air test Almost complete instrument Warm, so camera noise is still high –Vacuum test Final instrument Good environment, but little time

8. Page 8HMI/AIA Science Meeting – February 13, 2006 Sun Test Objectives Learn how to operate the HMI optics package. Learn how to characterize/calibrate the instrument. In some cases, obtain initial calibration parameters. Discover gross errors in design or workmanship of the HMI optics package. Determine position of focus to set the final shim on the telescope secondary lens. Determine position of waveplates in polarization selector to set the final orientation relative to hollow core motor step locations. Results of the Sun test will directly feed into the plans and procedures for the formal test and calibration series. The Sun test does not provide formal verification of any requirements.

9. Page 9HMI/AIA Science Meeting – February 13, 2006 Calibration Status as of Feb. 12, 2006 White – Not yet finished –Taken: Data taken but not yet analyzed –?????: May not be doable with current configuration (eg. high camera dark current) Green – Test done, all is OK Yellow – Minor problems –Incomplete or buggy analysis software. –Fixable test setup problem or apparent test glitch (eg. clouds) –Problem is understood and is easy to correct –Problem is understood and can’t be fixed, but does not impact full science objectives Red – Instrument problem potentially impacting science objectives, but –Not yet fully understood –Has known likely solution with modest modest schedule and cost impacts Black – Fatal problem found –Problem understood and science objectives can’t be met –Solution is unknown or has severe cost or schedule impacts Surgeon General’s warning: Preliminary results may cause severe upsets!

10. Page 10HMI/AIA Science Meeting – February 13, 2006 Calibration Matrix

11. Page 11HMI/AIA Science Meeting – February 13, 2006 Image Quality Distortion –Procedure works, but problems with stimulus telescope illumination. Difficult to do with Sun. Image scale –All OK. 0.5025”/pixel MTF –Astigmatism seen, but problems with stimulus telescope illumination –Sun data not yet analyzed Focus and field curvature –Right on for lamp. Bad seeing during Sun test –Field curvature analysis not complete Ghost images and scattered light –Difficult to do with high camera noise. May have to be deferred to vacuum test Contamination –Still needs to be done Image motions –Saw problems with test setup. Probably has been solved –Some displacements seen with focus blocks

12. Page 12HMI/AIA Science Meeting – February 13, 2006 Image focus

13. Page 13HMI/AIA Science Meeting – February 13, 2006 Special target continued

14. Page 14HMI/AIA Science Meeting – February 13, 2006 Image Wobble

15. Page 15HMI/AIA Science Meeting – February 13, 2006 CCD and Camera Flat Field –Details still to be worked out Linearity and gain –Still to be done. –Difficult due to thermal noise and camera drifts –Drifts believed due to known problem with this particular camera Quadrant crosstalk –Probably has to await vacuum test due to high thermal noise in air

16. Page 16HMI/AIA Science Meeting – February 13, 2006 Filter transmission Wavelength and spatial dependence –Phase maps have been made with laser and Sun –Test equipment problems for wavelength dependence. Believed fixable. –Elements will be replaced (decided before this test) Angular (as seen from detector) dependence –Still to be done Stability –Will try, but oven stability in air likely insufficient Throughput –Looks good –But gain drifts make things difficult

17. Page 17HMI/AIA Science Meeting – February 13, 2006 Phase Maps

18. Page 18HMI/AIA Science Meeting – February 13, 2006 Polarization Some data taken, but much analysis still to be done Significant problem found. –Linear polarization into instrument gives circular polarization of up to +/- 0.4!

19. Page 19HMI/AIA Science Meeting – February 13, 2006 Observables and Miscellaneous Observables –Still to be done. May wait for some instrument upgrades Thermal effects –Probably not doable in air Alignment legs –Range and step size determined. Meets spec. –Repeatability. Looks adequate, but more tests planned

20. Page 20HMI/AIA Science Meeting – February 13, 2006 Conclusion Tests progressing –Some tests done –Some not Some problems found –Some fixed –Some still need work –No showstoppers! Lots of data to analyze –Over 10000 images so far –Need people Stay tuned! Ask not what HMI can do for you! Ask what you can do for HMI!

21. Page 21HMI/AIA Science Meeting – February 13, 2006 Status - Mechanisms