The Maximum Entropy Method Using Visibilities Rick Pernak

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

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)

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

More Advantages ► Visibilities have a few more advantages: § Linear Combinations § “Compact” § “Instantaneous Results”

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)

Plots of Simulated Data

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

Back Projection vs. MEM_NJIT

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

Special Thanks ► Ana Rosas: Awesome Intern Coordinator