Monthly Report: 2003 December

Also available here.

Murison continued work on the adaptive optics (AO) front end for the FTS project.  He implemented in Maple an analytic model of the relevant optics, including rotation and translation misalignments of each optical element, then used a computer algebra package he previously developed for other projects to analytically trace through the adaptive optics system.  He successfully solved for the rotation angles required by the AO mirror to correct the location of the stellar image on the focal plane (specifically, to put the star on the end of the 50 micron fiber optic) for tip/tilt errors due to atmospheric fluctuations as measured by a separate video camera.  The solution includes 28 separate misalignment parameters.  This is one aspect of the AO mirror feedback loop model that will be incorporated in the AO control program that Murison is writing.  Murison has partially completed a technical memorandum describing his AO work.

Murison designed and implemented a test configuration that will allow him to debug his AO control program using the actual AO hardware that will go into the FTS.  The test rig is conveniently set up in Murison’s office.

Murison also came up with a modification that should solve a serious vibration problem due to the mechanical shutter employed by the FTS.  The shutter vibration problem has always been present, but, due to the placement of the FTS optical bench on solid concrete at the USNO 24-inch, the vibrations damped quickly and did not interfere with observations.  However, at the 25-inch telescope at the Clay Science Center, a resonance is now present and the vibrations do not damp quickly enough.  (Either that or the shutter has begun a long slide toward failure.) Murison solved the problem by vibrationally isolating the shutter assembly from the rest of the FTS.  He employed two of the most important problem-solving tools in scientific instrumentation: duct tape and a number 2 pencil.

The analytical ray tracing computer algebra package mentioned above that Murison wrote is described, in part, here.  Web pages summarizing Murison’s FTS-related activities are here.