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SODISM Analysis – Yale Effort

SODISM Analysis – Yale Effort. Sabatino Sofia and Terry Girard Department of Astronomy, Yale University & Ulysses J Sofia Physics Department, American University. SODISM Analysis – Yale Effort Objectives. Why establish a separate analysis effort?

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SODISM Analysis – Yale Effort

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  1. SODISM Analysis – Yale Effort Sabatino Sofia and Terry Girard Department of Astronomy, Yale University & Ulysses J Sofia Physics Department, American University

  2. SODISM Analysis – Yale Effort Objectives Why establish a separate analysis effort? The expected diameter changes are at the mas level. The extremely high precision requirement involves sensitivities order of magnitude higher than required by previous instruments. When precision requirements increase, algorithms that were adequate for earlier analysis may no longer suffice. Objective of our group: To develop specific algorithms for SODISM data analysis, and subject them to extensive testing. They will be compared with the equivalent algorithms developed at LATMOS for comparison, and when appropriate, they will be incorporated into the PICARD data processing software.

  3. SODISM Analysis – Yale Effort Objectives continued... This objective requires a continuing effort, and we are now only at the beginning stage. We started our work on issues where we have extensive experience obtained from our past work on the analysis of SDS data: 1) Flat field 2) Intensity as a function of time 3) Determination of the inflection point 4) To characterize all significant optical properties of SODISM The eventual ultimate objective is: 5) Determination of the SIZE and SHAPE of the solar disk.

  4. SODISM Analysis – Yale Effort Presentation overview U.J. will describe the current status of items 1) and 2), and discuss anticipated needed improvements. Terry will describe items 3) and 5), and discuss some of their implications regarding item 4). 1) Flat field 2) Intensity as a function of time 3) Determination of the inflection point 4) To characterize all significant optical properties of SODISM... 5) Determination of the SIZE and SHAPE of the solar disk.

  5. SODISM Analysis – Yale Effort Photometric reductions UJ's slides to be inserted here

  6. SODISM Analysis – Yale Effort Overall astrometric strategy • Parametrize solar disk size/shape and the various telescope aberrations. • Solve for the best-fit parameters via 2 minimization of measured and model Inflection-Point Position (IPP) differences for a series of observations that allows for separation of the intrinsic solar and instrument parameters: IPP(;Rsol,Rsol;xc,i,yc,i;xo,yo,ptilt,qtilt,s,d3,d5) Iterative strategy: • Initial/(previous) guess at parameters, • Calculate model (elliptical) solar disk IPPmodel, • Compare with IPPmeas2, • Modify parameters, go to step 1) and repeat; searching for 2 minimum. optical system solar frame

  7. SODISM Analysis – Yale Effort From frames to radii: our current procedure For each FITS frame: bin pixel data into 4096 angular sectors, w.r.t. frame center, yielding an intensity profile, I(r), for each sector take numerical derivative; dI/dr find the dI/dr peak within a search window select nearby dI/dr points (>0.4 interior to peak; >0.1 exterior to peak) fit with a gaussian IPP and width (slope) filter spurious IPPs as a function of  find barycenter of all sector wedges; xc,yc best-fit circle and best-fit ellipse; Rsol, Rsol correct to 1 AU fourier decomposition of the residuals as a diagnostic tool

  8. SODISM Analysis – Yale Effort Inflection point determination

  9. SODISM Analysis – Yale Effort Limb profiles

  10. SODISM Analysis – Yale Effort Inflection Point Position (IPP) vs 

  11. SODISM Analysis – Yale Effort Circle-fit residuals & Fourier coefficients deviations from circle exaggerated 1000

  12. SODISM Analysis – Yale Effort Disk radius as a function of time

  13. SODISM Analysis – Yale Effort Disk radius: detail

  14. SODISM Analysis – Yale Effort Disk barycenter

  15. SODISM Analysis – Yale Effort Disk shape: ellipticity and triangularity

  16. SODISM Analysis – Yale Effort Disk-shape variation with time

  17. SODISM Analysis – Yale Effort Inflection point slope, ( i.e., width of fit to first derivative)

  18. SODISM Analysis – Yale Effort Summary of disk size/shape results Noteworthy results include: long-term trends in Rsol vs t ; vary with filter ; correlate with shape two “families” of Rsol vs t for same filter (at times) ; correlate with shape disk shape is different for different filters ; evolves with time full (RS) data give same results as wide-ring (DL) data inflection slope (width) varies with ; steepest at poles

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