From MDI to HMI

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From MDI to HMI
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Outline

• MDI Status
• HMI
• Overview
• Observing scheme
• Status
• Schedule
• Transition

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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

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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 Suns 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.

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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

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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
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Instrument Overview HMI Optics Package (HOP)
Connector Panel
Z
Focal Plane B/S
Fold Mirror
Shutters
Alignment Mech
X
Limb Sensor
Y
Oven Structure
Detector
Michelson Interf.
Lyot Filter
CEBs
Detector
Vents
Limb B/S
Front Window
Active Mirror
Polarization Selector
Focus/Calibration Wheels
OP Structure
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
Telescope
Support Legs (6)
Front Door
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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

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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
• What do the users prefer?

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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

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Status What I hoped to show

• First HMI Dopplergram

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Status What we got
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Status

• First set of Michelsons in house
• Optics and filters in house
• Some spares still to be delivered
• Several flight 4096x4096 CCDs 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

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Status - Integration
Flight Michelsons
Flight Structure Heater Wiring
Primary Secondary Lens Assemblies
Telescope Assembly on Alignment Plate
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Status - Integration
ISS Fold Mirror Assembly
ISS Mirror Assembly
ISS Sensor Assemblies
BDS Fold Mirror Assembly
BDS Fold Mirror Assembly
CCD Fold Mirror Assembly
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Status - Mechanisms
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Status - Mechanisms
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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 !

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MDI -gt 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?

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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!

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Filter profiles
Line profile
MDI
Continuum
Continuum