Performance of Phase Apodization Coronagraphs at the MMT Michael Gaj Dr. John Codona The University of Arizona Center for Astronomical Adaptive Optics Arizona Space Grant Consortium Statewide Symposium April 18th, 2008

Astronomical Imaging Two main problems in extrasolar-planet are diffraction patterns and atmospheric speckles. Although adaptive optics systems do a good job of suppressing atmospheric turbulence, they cannot correct diffraction patterns and speckles. Some diffraction patterns can be corrected with modern coronagraphs, but they cannot eliminate the speckles.

What is the Phase Apodization Coronagraph? Unlike other coronagraphs, the PAC is able to eliminate diffraction patterns while maintaining constant telescope position. Result: Speckles can be averaged and the background can be smoothed. Astronomers are now able to observe nearby extrasolar planets thousands of times fainter than their parent star.

Image at MMT with PAC

PAC Efficiency Although the PAC is a proven method of image correction, the device breaks down and looses its effectiveness at a certain wavelength. The question then becomes: At what wavelengths can the PAC successfully operate?

Simulated Images at MMT 5 Microns 2.2 Microns 1.65 Microns 1 Micron .8 Microns

Performance of PAC

Results From the graph, the PAC proved to be most effective at a wavelength of 5 microns. However, there is very little sensitivity difference for wavelengths of 5, 2.2 and 1.65 microns over an angle of .7 arc seconds. Wavelengths lower than this value showed no significant improvement in image quality.