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The Maximum Entropy Method Using Visibilities

The Maximum Entropy Method Using Visibilities. Rick Pernak RHESSI Team. Summer Project. Figure out MEM_NJIT See if it works! Imaging of Solar Flares Make visibility maps Based on visibilities calculated from Ed and Richard Schwartz. MEM. Maximum Entropy Method

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The Maximum Entropy Method Using Visibilities

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  1. The Maximum Entropy Method Using Visibilities Rick Pernak RHESSI Team

  2. Summer Project • Figure out MEM_NJIT • See if it works! • Imaging of Solar Flares • Make visibility maps • Based on visibilities calculated from Ed and Richard Schwartz

  3. MEM • Maximum Entropy Method • MEM of any type (e.g. VIS, SATO) produces the most probable image • Program maximizes an entropy term: S = -E FIJ log(FIJ)

  4. Visibility • Amplitude and a phase Vis = A(k) * exp(-2πi*(k * x)) • Where k = (u,v) and x = (x,y) • And A(k) = exp(-((k/kmin)/2)2)

  5. Advantages of Visibilities • analogous to Modulation profile • NRAO/OVSA already have programs to map visibilities – we want to use their software! • MEM_NJIT is based on OVSA MEM program

  6. More Advantages • Visibilities have a few more advantages: • Linear Combinations • “Compact” • “Instantaneous Results”

  7. Project Details • First 2 months: PROGRAMMING • Trying to figure out MEM_NJIT • Used mostly simulated data • Simple stuff: • Point source, double source, constant amplitude… • Gaussian source (with constant amp) • ‘tapering’ amplitude function (with point source)

  8. Plots of Simulated Data

  9. Future Plans: • Imaging solar flares from RHESSI Data • Adding maps to website • hesperia.gsfc.nasa.gov/~schmahl/comparisons/mem.html • Data chosen from RHESSI database HEDC

  10. Back Projection vs. MEM_NJIT

  11. Thank you: • Brian Dennis • Gordon Holman • All of the interns – it’s been a lot of fun • Most Importantly, Ed Schmahl

  12. Special Thanks • Ana Rosas: Awesome Intern Coordinator

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