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

3. Noise Simulations with ASP Data

4. 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

5. 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