Astrometria solar usando o MDISOHO e HMISDO

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Astrometria solar usando o MDI/SOHO e HMI/SDO
Marcelo Emilio1, Jeff Kuhn2, Rock Bush3
1-DEGEO-UEPG 2-IFA-UH
3-Stanford University

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MDI-SOHO
Launch in 2/DEC/95
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Michelson Doppler Imager (MDI)?
Ni I photospheric absorption line at 6767.8 Å.
The width of the bandpass is fixed at 94 mÅ.
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• Primary Science Objectives
• Radial Stratification
• Determine the spherically symmetric
  components of the mean radial structure of the
  Sun in and below the convective envelope of
  pressure, density, composition, and sound speed.
• Internal Rotation
• Determine the rotation rate as a function of
  radius and latitude.
• Large-Scale Convection
• Large-scale convection cells and associated
  thermal structures
• Large-Scale Asphericity
• Determine the non-spherically symmetric
  components of the mean structure in the
  convective envelope of pressure, density,
  composition, and sound speed.
• Upper Convective Boundary Layer
• Make a detailed sampling of the sub-surface
  regions by determining the upper reflection point
  for most p-modes. Explore this region dominated
  by highly turbulent convection and fibril
  magnetic fields.
• Chromospheric Structure
• Analyze magnetic and thermal structures
  within the chromospheric acoustic cavity.
• Excitation and Damping
• Explore the coupling of acoustic-gravity
  waves to turbulent convection. Determine mode
  lifetimes, and elucidate the driving mechanisms.
• Active Region Seismology
• Measure the scattering and absorption of
  waves by active regions search for wakes behind
  sunspots search for pre-eruptive magnetic
  fields.
• Internal Global Scale Magnetic Fields
• Determine the strength of the toroidal
  magnetic fields at the base of the convection
  zone, and of the core fields.

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Transient thermal and optical response of MDI
after the front window was opened 1998 November
20. Time is measured along the horizontal axis in
minutes after the instrument is exposed to
sunlight. The best focus setting is in focus
block units the modeled window gradient (in C)
and the temperatures of the window and primary
and secondary lens (in tens of C) are indicated
on the left. The apparent solar radius (in
pixels) is shown on the right vertical scale.
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Mercury Transit 7 May 2003
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FW PL SL
Focus Annual Change
Trend
(pixels/?C) (pixels/?C) (pixels/?C)
(pixels/FB)? Model 1 0.01 -0.009
0.038 -0.097 Model 2 0.01
-0.0110.002 0.0410.002 -0.0790.005
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Solar cycle amplitude -17 /11 mas
2 s upper limit 22 mas
Linear trend .9 /- 1.6 mas/yr
2 s upper limit 3.2 mas/yr or .3 arcsec/century
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MDI-SOHO Roll Measurements

• 20 March 1997
• 14 Nov 2001
• 26 Out 2009

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Least Square Function Fitted
Phase Modulation Calculation
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1997
2001
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Solay Dynamics Observatory (SDO)?

• The total mass of the spacecraft at launch is
  3200 kg (payload 270 kg fuel 1400 kg).
• Its overall length along the sun-pointing axis
  is 4.5 m, and each side is 2.22 m.
• The span of the extended solar panels is 6.25 m.
• Total available power is 1540 W from 6.5 m2 of
  solar arrays (efficiency of 16).
• The high-gain antennas rotate once each orbit to
  follow the Earth.

2.5 TByte/day
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SDO Instruments

• HMI (Helioseismic and Magnetic Imager)?
• The Helioseismic and Magnetic Imager will extend
  the capabilities of the SOHO/MDI instrument with
  continuous full-disk coverage at higher spatial
  resolution. PI Phil Scherrer, PI Institution
  Stanford University.
• AIA (Atmospheric Imaging Assembly)?
• The Atmospheric Imaging Assembly will image the
  solar atmosphere in multiple wavelengths to link
  changes in the surface to interior changes. Data
  will include images of the Sun in 10 wavelengths
  every 10 seconds. PI Alan Title, PI Institution
  Lockheed Martin Solar Astrophysics Laboratory.
• EVE (Extreme Ultraviolet Variablity Experiment)?
• The Extreme Ultraviolet Variablity Experiment
  will measure the solar extreme-ultraviolet (EUV)
  irradiance with unprecedented spectral
  resolution, temporal cadence, and precision.
  Measures the solar extreme ultraviolet (EUV)
  spectral irradiance to understand variations on
  the timescales which influence Earth's climate
  and near-Earth space. PI Tom Woods, PI
  Institution University of Colorado.

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HMI GOALS

• Convection-zone dynamics and the solar dynamo
• Origin and evolution of sunspots, active regions
  and complexes of activity
• Sources and drivers of solar activity and
  disturbances
• Links between the internal processes and dynamics
  of the corona and heliosphere
• Precursors of solar disturbances for
  space-weather forecasts.

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HMI Products

• Stabilized 1 arc-second resolution full-disk
  Doppler velocity and line-of-sight magnetic flux
  images at least every 50 seconds
• Stabilized 1 arc-second resolution full-disk
  vector-magnetic images of the longitudinal solar
  magnetic field at least every 90 seconds
• From the filtergrams
• Dopplergrams
• Longitudinal and vector magnetograms
• Continuum intensity images

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Immediate prospects Solar Dynamics Observer
(SDO) HMI Optics Package (HOP)?
Connector Panel
Z
Focal Plane B/S
Fold Mirror
X
Shutters
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
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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Limb astrometry from Space
NB Telescope diffraction limit has very little
to do with astrometric accuracy
dr
Statistical distribution of angle of arrival
fluctuations define dr
dI
With no atmosphere, photometric gain uncertainty
(flatfielding) defines dr
In practice limb isnt knife edge, spacecraft
pointing jitter is about 0.01 pixel (and
correlated!), long term stability limitations are
due to optics thermal drifts (MDI) 1px2
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Conclusions

• MDI/SOHO allowed us to study the solar radius and
  shape variation.
• We established an upper limit to solar radius
  variations and our data shows that Solar Shape
  may change with the solar cycle.
• HMI/SDO will improve our determination of solar
  radius variation and study in detail shape
  variations (one roll each 6 months).
• Both Picard and SDO (Launch in January 2010) are
  planned to do solar astrometry.

HMI/SDO
Picard