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Page 2 lOhcO 9 meeting
Outline
• MDI Status
• HMI
– Overview
– Observing scheme
– Status
– Schedule
• Transition
Page 3 lOhcO 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
Page 4 lOhcO 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.
Page 5 lOhcO 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
Page 6 lOhcO 9 meeting
Image Stabilization Mirror
CCD Fold Mirror
CCD Fold MirrorFold Mirror
¼ Waveplate ½ Waveplates
Telescope lens set Telecentric
Lens
Calibration lensesand Focus Blocks
Front Window Filter
Relay Lens Set
Blocking Filter
BDS Beamsplitter
NarrowbandMichelson
Polarizer
ISS Beamsplitterand Limb Tracker Assembly
TuningWaveplates
Beam Control Lens
Lyot
WidebandMichelson
CCD
CCD
Shutter Assemblies
Aperture Stop
Instrument Overview – Optical Path
Optical Characteristics:Focal Length: 495 cmFocal Ration: f/35.2Final Image Scale: 24m/arcsecPrimary to Secondary Image Magnification: 2Focus Adjustment Range: 16 steps of 0.4 mm
Filter Characteristics:Central Wave Length: 613.7 nm FeIFront Window Rejects 99% Solar Heat LoadBandwidth: 0.0076 nmTunable Range: 0.05 nmFree Spectral Range: 0.0688 nm
Page 7 lOhcO 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 MirrorFocal Plane B/S
Mechanical Characteristics:Box: 0.84 x 0.55 x 0.16 mOver All: 1.19 x 0.83 x 0.29 mMass: 39.25 kgFirst Mode: 63 Hz
YX
Detector
Limb Sensor
Z
Page 8 lOhcO 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
Page 9 lOhcO 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 fieldo What do the users prefer?
Page 10 lOhcO 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
Page 11 lOhcO 9 meeting
Status – What I hoped to show
• First HMI Dopplergram
Page 12 lOhcO 9 meeting
Status – What we got
Page 13 lOhcO 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
Page 14 lOhcO 9 meeting
Status - Integration
Telescope Assembly on Alignment Plate
Flight Structure Heater Wiring
Primary & Secondary Lens Assemblies
Flight Michelsons
Page 15 lOhcO 9 meeting
Status - Integration
ISS Mirror Assembly ISS Fold Mirror Assembly
ISS Sensor Assemblies BDS Fold Mirror Assembly
BDS Fold Mirror Assembly CCD Fold Mirror Assembly
Page 16 lOhcO 9 meeting
Status - Mechanisms
Page 17 lOhcO 9 meeting
Status - Mechanisms
Page 18 lOhcO 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 !
Page 19 lOhcO 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?
Page 20 lOhcO 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!
Page 21 lOhcO 9 meeting
Filter profiles
Continuum Continuum
MDI
Line profile
