1. Page 1lOhcO 9 meeting From MDI to HMI Jesper Schou Stanford University jschou@solar.stanford.edu

2. Page 2lOhcO 9 meeting Outline MDI Status HMI –Overview –Observing scheme –Status –Schedule Transition

3. Page 3lOhcO 9 meeting MDI Status 10 year launch anniversary Dec 2! 100 million exposures Keyhole –Broken antenna –Flip every 3 months –Loose two weeks of high rate data –Difficult to get good dynamics runs Otherwise things are fine Plan to operate for 6-12 months after HMI is operational –Other SOHO instruments may be kept running after that

4. Page 4lOhcO 9 meeting HMI Overview The primary goal of the Helioseismic and Magnetic Imager (HMI) investigation is to study the origin of solar variability and to characterize and understand the Sun’s interior and the various components of magnetic activity. The HMI investigation is based on measurements obtained with the HMI instrument as part of the Solar Dynamics Observatory (SDO) mission. HMI makes measurements of several quantities –Doppler Velocity (13m/s rms.) –Line of sight (10G rms.) and vector magnetic field –Intensity –All variables all the time with 0.5” pixels –Most at 50s or better cadence –Variables are made from filtergrams, all of which are downlinked Higher level products will be made as part of the investigation. All data available to all. Launch in August 2008. 5 Year nominal mission. Education and Public Outreach program included.

5. Page 5lOhcO 9 meeting 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

6. Page 6lOhcO 9 meeting 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 Ration: f/35.2 Final Image Scale: 24  m/arcsec Primary to Secondary Image Magnification: 2 Focus Adjustment Range: 16 steps of 0.4 mm Filter Characteristics: Central Wave Length: 613.7 nm FeI Front Window Rejects 99% Solar Heat Load Bandwidth: 0.0076 nm Tunable Range: 0.05 nm Free Spectral Range: 0.0688 nm

7. Page 7lOhcO 9 meeting Instrument Overview – HMI Optics Package (HOP) OP Structure Telescope Front Window Front Door Vents Support Legs (6) Polarization Selector Focus/Calibration Wheels Active Mirror Limb B/S Alignment Mech Oven Structure Michelson Interf. Lyot Filter Shutters Connector Panel CEBs Detector Fold Mirror Focal Plane B/S Mechanical Characteristics: Box: 0.84 x 0.55 x 0.16 m Over All: 1.19 x 0.83 x 0.29 m Mass: 39.25 kg First Mode: 63 Hz Y X Detector Limb Sensor Z

8. Page 8lOhcO 9 meeting 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 – selected by rotating waveplates (polarizer for redundancy only) –Polarization state – selected by rotating waveplates –Exposure time –Camera ID –Compression parameters, … –Determined by subsystem settings E.g. motor positions Framelists –Fixed list of filtergrams repeated at fixed cadence during normal operations –Entirely specified in software – highly flexible

9. Page 9lOhcO 9 meeting 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! Interpolation necessary Fast and accurate algorithm exists –Correct for acceleration effects (temporal interpolation) Nyquist criterion almost fulfilled for Doppler and LOS Nyquist is grossly violated for vector measurements in case of long framelists Significant improvement from interpolation Clever tricks exist Temporal averaging helps –Fill gaps Data loss budget gives missing data in every filtergram! Various algorithms exist May do nothing for vector field oWhat do the users prefer?

10. Page 10lOhcO 9 meeting Observables Calculation Average in time, if desired –Done for at least some vector field inversions 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, etc. Community input needed! –Inversion codes –Which dataproducts do you want? –Science

11. Page 11lOhcO 9 meeting Status – What I hoped to show First HMI Dopplergram

12. Page 12lOhcO 9 meeting Status – What we got

13. Page 13lOhcO 9 meeting Status First set of Michelsons in house Optics and filters in house –Some spares still to be delivered Several flight 4096x4096 CCD’s in house Instrument being assembled –May see first light before Christmas Mechanisms –Shutters and HCMs finished life test successfully Electronics at various stages –Significant delays expected Instrument software at various stages Ground software at various stages

14. Page 14lOhcO 9 meeting Status - Integration Telescope Assembly on Alignment Plate Flight Structure Heater Wiring Primary & Secondary Lens Assemblies Flight Michelsons

15. Page 15lOhcO 9 meeting Status - Integration ISS Mirror Assembly ISS Fold Mirror Assembly ISS Sensor AssembliesBDS Fold Mirror Assembly CCD Fold Mirror Assembly

16. Page 16lOhcO 9 meeting Status - Mechanisms

17. Page 17lOhcO 9 meeting Status - Mechanisms

18. Page 18lOhcO 9 meeting Schedule Late 2005: First Sun test Feb 2006: Team meeting Summer 2006: Final instrument tests Feb 2007: Instrument delivery Aug 2008: Launch Nov 2008: Begin science observations Nov 2013: End of science observations Nov 2014: End of mission Stay tuned on http://hmi.stanford.edu !http://hmi.stanford.edu

19. Page 19lOhcO 9 meeting MDI -> HMI Transition Basically we will get 6-12 months of overlap Any particular things we should do during that period? Anything we need to do now?

20. Page 20lOhcO 9 meeting Summary 4096x4096 full disk coverage 0.5” pixels Continuous coverage Doppler and LOS at 40s cadence Vector magnetograms at 40s-120s cadence Uniform quality Same observing sequence all the time August 2008 launch 5 year nominal mission Lots of new science possible Need your help!

21. Page 21lOhcO 9 meeting Filter profiles Continuum MDI Line profile