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The Maximum Entropy Method Using Visibilities

Explore MEM_NJIT software for solar flare imaging based on visibilities calculated from Schwartz MEM. Utilize advantageous linear combinations and instant results. Programming phase involves simulated data to map point, double, Gaussian sources. Future plans include imaging solar flares from RHESSI data and website updates. Acknowledgments to team members and interns.

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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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