S/N and Polarimetry With HMI

1
S/N and Polarimetry With HMI

• Bruce W. Lites
• High Altitude Observatory
• National Center for Atmospheric Research
• HMI Team Meeting, Palo Alto, 1-2 May 2003

2 May 2003
2
Significant Considerations for S/N and Accuracy
of Vector Magnetic Field Inversions
Results are compromised by

• Spectral resolution
• Spectral sampling
• Noise level
• Detector full-well issues non-linearity,
  intensity margin
• Duty cycle of instrument
• Accuracy of measured instrument spectral profile

Bruce Lites, HMI Team Mtg., 2 May 2003
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Noise Simulations with ASP Data
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Realistic Simulations?

• HMI Vector field tests so far only indicate the
  best case inversions are initialized from the
  solution, or very close to it
• Realistic simulations must account for the issue
  of initialization
• New pattern recognition techniques (principal
  components analysis, neural network, support
  vector machine) do not rely on initial guess, but
  also may substantially miss the solution if the
  data are too noisy

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Recommendation

• With the HMI CCD source now in question, an
  opportunity exists to examine the choices for
  detectors with a view of larger full-well
  capacity, or
• With Solar-B, the technology exists for space
  instrumentation to do rapid readout/summing of
  images