Subject: Re: ITS Room-Temperature Calibration Flash report Date: Fri, 17 Jan 2003 19:53:31 -0500 From: Dennis Wellnitz Hi all, After lots of effort today in a variety of directions, we tried masking off all the surfaces around the ITS and around the pinhole to eliminate stray light, because Dennis Gallagher thought some of the "astigmatic line foci" looked more like an additional image due to stray light. With that change, the out-of-focus images of the pinhole became round and the in-focus images looked like those we saw in the MRI. We have found the problem: stray light masquerading as astigmatism. Tomorrow, Saturday, with the stray light masks in place, we plan to run through a new set of vertical and horizontal knife edges through focus to determine the best ITS focus, to see whether the focus is close enough to optimal focus to go on to thermal vac, or whether we need to move the CCD to optimize focus. At this point it appears that the earliest start of ITS thermal vac would be about Tuesday, with a possibility that the start could be as late as Thursday if we need to move the CCD. Calibration starts after the bake-out is finished, which takes a minimum of 48 hours, so the earliest calibrations could start would be about Friday, January 24, and calibrations could start as late as Monday, January 27. Please let me know if you have any comments or questions. If you would prefer not to receive these Flash reports on the ITS Room-Temperature Calibration, please let me know. Dennis