The Magellan AO system will begin commissioning in early 2012. Its VisAO camera will provide 20 mas FWHM images with mean Strehl ratios of ~ 0.2 in R band on a 6.5m telescope. Depending on seeing conditions, Strehl ratio may reach... more
The Magellan AO system will begin commissioning in early 2012. Its VisAO camera will provide 20 mas FWHM images with mean Strehl ratios of ~ 0.2 in R band on a 6.5m telescope. Depending on seeing conditions, Strehl ratio may reach temporary peaks as high as 0.5 at these wavelengths. To take advantage of these brief periods of high performance, we plan to adopt lucky imaging style data taking and reduction techniques. As part of this effort we have developed a novel real-time frame selection technique, which will use AO system telemetry and a fast shutter to limit CCD exposure to these very brief moments of higher Strehl. Here we describe the expected benefits of our frame selection techniques in various operating modes. We also present the results of laboratory characterization of the shutter, and describe the performance of predictive algorithms used to control it.
At the University of California's Lick Observatory, we have implemented an on-sky testbed for next-generation adaptive optics (AO) technologies. The Visible-Light Laser Guidestar Experiments instrument (ViLLaGEs) includes... more
At the University of California's Lick Observatory, we have implemented an on-sky testbed for next-generation adaptive optics (AO) technologies. The Visible-Light Laser Guidestar Experiments instrument (ViLLaGEs) includes visible-light AO, a micro-electro-mechanical-systems (MEMS) deformable mirror, and open-loop control of said MEMS on the 1-meter Nickel telescope at Mt. Hamilton. (Open-loop in this sense refers to the MEMS being separated optically from
The aim of this work is to determine the influence of interocular differences in retinal image quality on binocular visual performance. We measured the contrast sensitivity function (both monocular and binocular) and we computed binocular... more
The aim of this work is to determine the influence of interocular differences in retinal image quality on binocular visual performance. We measured the contrast sensitivity function (both monocular and binocular) and we computed binocular summation. Data on retinal image quality were taken from a double-pass device (oqas™, Optical Quality Analysis System; Visiometrics SL. Tarrasa, Spain), providing the Strehl ratio as a parameter to quantify retinal image quality. A total of 28 observers took part in the experiments. Binocular summation for the contrast sensitivity function was found to be significantly (p < 0.001) correlated with interocular differences in the Strehl ratio. The higher the interocular differences in the Strehl ratio, the lower the binocular summation. Binocular summation is less effective as the interocular differences in retinal image increase.
Non-redundant masking (NRM) is a high contrast high resolution technique that is relevant for future space missions dedicated to either general astrophysics or extrasolar planetary astronomy. On the ground NRM has opened a rich target... more
Non-redundant masking (NRM) is a high contrast high resolution technique that is relevant for future space missions dedicated to either general astrophysics or extrasolar planetary astronomy. On the ground NRM has opened a rich target space between 0.5 to 4 resolution elements from bright stars. It enabled moderate contrast very high angular resolution observations that have provided dynamical masses for targets beyond the resolution of the Hubble Space Telescope. Such observations challenge the best models of ultra-cool dwarf stars' atmospheres and interiors. The technique succeeds because it sidesteps the effects of speckle noise that plagues direct imaging at moderate Strehl ratios. On a space telescope NRM mitigates instrument-induced speckle noise, thus enabling high contrast even when images are barely diffraction-limited. The non-redundant mask in the Fine Guidance Sensor Tunable Filter Imager (FGS-TFI) on the James Webb Space Telescope (JWST) will open up a search space between 50 and 400 mas at wavelengths longer than 3.8μm. We present simulations that estimate achievable contrast on JWST, and report preliminary results of a testbed experiment using a mask with the same geometry as JWST's. We expect contrast of the order of 104 will be achievable in a 10 ks exposure of an M = 7 star, with observing, target acquisition, and data calibration methods common to the three other imaging instruments on board JWST. As an example of the potential science possible with NRM, we show that if a planet were responsible for clearing the inner 5 AU of the disk around HR8799, it would likely be detectable using JWST FGS-TFI's NRM at 4.6 microns. Stars as bright as M = 3 will also be observable with JWST's NRM, meshing well with next-generation ground-based extreme adaptive optics coronagraphs. JWST NRM's parameter space is inaccessible to both JWST coronagraphs and future 30-m class ground-based telescopes, especially in the mid-IR.
