HESSI PSF in Polar Coordinates
This figure shows the HESSI point spread function for 9 subcollimators
as computed in polar coordinates (using polar_psf.pro) and then
projected onto the x-y plane. The upper left hand corner is at Sun
center, and the outermost radius is 1000´´ from Sun center.
The original pixel sizes of the polar PSF were 1´´ in radius
and 0.35° (6.1 milli radians) in azimuth. The point source was
taken to be at r=600´´, AZ = -45°. At this distance from
Sun center, the azimuthal size of the PSF pixels is 3.7´´, about the
resolution of the 2nd finest subcollimator, but not really
adequate for the finest subcollimator, whose spatial resolution
is 2.2´´.
The advantages of using polar coordinates for the PSF are that
- The PSF is computable using a very fast convolution, potentially
speeding up MEM and CLEAN by an order of magnitude.
- All PSFs on a given radius are exact shifts of any other,
reducing storage requirements for CLEAN and MEM by a large factor.
December 2 Version of POLAR_PSF.PRO
Edward J. Schmahl
Last modified: Thu Dec 2 12:32:31 EST 1999