Transcript Presentation

From MDI to HMI
Jesper Schou
Stanford University
[email protected]
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Page 1
Outline
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MDI Status
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HMI
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Overview
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Observing scheme
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Status
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Schedule
Transition
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Page 2
MDI Status
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10 year launch anniversary Dec 2!
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100 million exposures
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Keyhole
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Broken antenna
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Flip every 3 months
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Loose two weeks of high rate data
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Difficult to get good dynamics runs
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Otherwise things are fine
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Plan to operate for 6-12 months after HMI is operational
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Other SOHO instruments may be kept running after that
Page 3
HMI Overview
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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.
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The HMI investigation is based on measurements obtained with the HMI
instrument as part of the Solar Dynamics Observatory (SDO) mission.
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HMI makes measurements of several quantities
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Doppler Velocity (13m/s rms.)
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Line of sight (10G rms.) and vector magnetic field
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Intensity
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All variables all the time with 0.5” pixels
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Most at 50s or better cadence
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Variables are made from filtergrams, all of which are downlinked
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Higher level products will be made as part of the investigation.
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All data available to all.
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Launch in August 2008. 5 Year nominal mission.
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Education and Public Outreach program included.
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Page 4
Instrument Overview
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Optics Package
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Telescope section
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Polarization selectors – 3 rotating waveplates for redundancy
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Focus blocks
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Image stabilization system
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5 element Lyot filter. One element tuned by rotating waveplate
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2 Michelson interferometers. Tunable with 2 waveplates and 1 polarizer for redundancy
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Reimaging optics and beam distribution system
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Shutters
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2 functionally identical CCD cameras
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Electronics package
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Cable harness
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Page 5
Instrument Overview – Optical Path
Image Stabilization
Mirror
Beam Control
Lens
¼ Waveplate
½ Waveplates
Aperture Stop
Blocking Filter
Wideband
Michelson
Telescope lens set
Telecentric
Lens
Lyot
Polarizer
Tuning
Waveplates
Narrowband
Michelson
Calibration lenses
and Focus Blocks
ISS Beamsplitter
and Limb Tracker
Assembly
BDS
Beamsplitter
Relay Lens
Set
Front Window Filter
CCD
Shutter
Assemblies
CCD
CCD Fold Mirror
Fold Mirror
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
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CCD Fold Mirror
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
Page 6
Instrument Overview – HMI Optics Package (HOP)
Z
Connector Panel
Focal Plane B/S
Fold Mirror
Shutters
X
Alignment Mech
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
Telescope
Front Door
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Support Legs (6)
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
Page 7
Observing Scheme
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Observables
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Dopplergrams
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Magnetograms, vector and line of sight
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Others: Intensity, line depth, etc.
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Observables made from filtergrams described by framelists
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Filtergram properties
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Wavelength – selected by rotating waveplates (polarizer for redundancy only)
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Polarization state – selected by rotating waveplates
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Exposure time
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Camera ID
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Compression parameters, …
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Determined by subsystem settings
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E.g. motor positions
Framelists
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Fixed list of filtergrams repeated at fixed cadence during normal operations
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Entirely specified in software – highly flexible
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Page 8
Observables Calculation
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Make I, Q, U, V, LCP, RCP
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Linear combinations of filtergrams
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Correct for flat field, exposure time and polarization leakage
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Correct for solar rotation and jitter (spatial interpolation)
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–
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Sun rotates by 0.3 pixels in 50s!
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Interpolation necessary
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Fast and accurate algorithm exists
Correct for acceleration effects (temporal interpolation)
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Nyquist criterion almost fulfilled for Doppler and LOS
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Nyquist is grossly violated for vector measurements in case of long framelists
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Significant improvement from interpolation
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Clever tricks exist
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Temporal averaging helps
Fill gaps
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Data loss budget gives missing data in every filtergram!
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Various algorithms exist
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May do nothing for vector field
o
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What do the users prefer?
Page 9
Observables Calculation
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Average in time, if desired
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Calculate observables
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MDI-like and/or least squares for Doppler and LOS?
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Fast and/or full inversion for vector field
Many challenges remain
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Done for at least some vector field inversions
Calibration, code development, etc.
Community input needed!
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Inversion codes
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Which dataproducts do you want?
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Science
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Page 10
Status – What I hoped to show
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First HMI Dopplergram
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Page 11
Status – What we got
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Status
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First set of Michelsons in house
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Optics and filters in house
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Some spares still to be delivered
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Several flight 4096x4096 CCD’s in house
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Instrument being assembled
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Mechanisms
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May see first light before Christmas
Shutters and HCMs finished life test successfully
Electronics at various stages
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Significant delays expected
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Instrument software at various stages
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Ground software at various stages
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Page 13
Status - Integration
Flight Structure Heater Wiring
Flight Michelsons
Primary & Secondary Lens Assemblies
Telescope Assembly on Alignment Plate
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Status - Integration
ISS Mirror Assembly
ISS Sensor Assemblies
BDS Fold Mirror Assembly
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ISS Fold Mirror Assembly
BDS Fold Mirror Assembly
CCD Fold Mirror Assembly
Page 15
Status - Mechanisms
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Page 16
Status - Mechanisms
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Page 17
Schedule
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Late 2005: First Sun test
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Feb 2006: Team meeting
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Summer 2006: Final instrument tests
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Feb 2007: Instrument delivery
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Aug 2008: Launch
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Nov 2008: Begin science observations
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Nov 2013: End of science observations
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Nov 2014: End of mission
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Stay tuned on http://hmi.stanford.edu !
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Page 18
MDI -> HMI Transition
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Basically we will get 6-12 months of overlap
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Any particular things we should do during that period?
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Anything we need to do now?
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Page 19
Summary
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4096x4096 full disk coverage
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0.5” pixels
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Continuous coverage
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Doppler and LOS at 40s cadence
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Vector magnetograms at 40s-120s cadence
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Uniform quality
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Same observing sequence all the time
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August 2008 launch
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5 year nominal mission
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Lots of new science possible
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Need your help!
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Page 20
Filter profiles
Line profile
MDI
Continuum
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Continuum
Page 21