Subject: HRI/MRI IP TV4 Flash report Date: Thu, 06 Mar 2003 02:32:18 -0500 From: Dennis Wellnitz Hi all, This is the flash report for Wednesday, March 5, 2003. Everyone has been increasingly concerned about how much time it might take to do all the remaining test during this thermal vac. Based on a prioritized list of remaining items and estimated times for each item, we estimate that we will finish all of the required items at coldest temperature late on Friday, if we continue to work at least 12-hour test days. That would permit raising the temperature 10 degrees for additional tests on Saturday, and then warming up over Sunday and the first couple of days of the following week. We put together a prioritized list of test items for daytime and after dark (the radiometric measurements generally require darkness to reduce the influence of ambient light), and will work hard to stay on schedule. The first item of the day was an HRI through-focus pinhole. This focus test gave acceptable results and indicates that the focus of the HRI is within microns of the desired position. Based on this data there appears to be no need to adjust the focus of the HRI. In fact, the smallest possible shim would probably make it worse instead of better, considering the risk involved in changing shims. Congratulations to all who made this possible! Following this was a test of the effective focal length of the HRI, which was within 0.17% of the expected focal length. We also appended to this test an image of the pinhole in every filter. We then did a number of imaging tests on the HRI. First was the sine target in all filters. Next was the Air Force Resolution (AFR) test target imaged in all filters, in 9 positions for all but the clear filters, and in only 4 positions for the clear filters because we were running low on time for this test. We followed this with the latent image test for the HRI, centering the AFR test target and then over-illuminating it to look for latent images in succeeding images. We then switched back to the MRI for a couple of imaging tests. First we did the sine wave target through the two UV filters using the continuous source because the flash lamp was not bright enough. We followed this with images of a pinhole through all the filters. As we were finishing the MRI imaging tests, it was beginning to get dark, so in parallel with those tests we began setting up the large, 27-inch aperture integrating sphere so that we could start the radiometric calibrations of the HRI. While the lamp in the integrating sphere was equilibrating (which takes about half an hour from turn-on) we took a series of all-mode HRI-VIS bias images (shutter closed and chamber window covered). Then when the lamp was equilibrated we took flat fields in all modes in the clear filter, followed by mode 1 in all filters. This was followed by flat fields in the clear filters, with various exposures both in the linear regime and near saturation for filter 1, but only in the linear regime for filter 6. We saw no surprises in quick looks at these measurements. While we had the clear filter in place, we also took a long exposure with the shutter closed, to test the light rejection of the HRI shutter. It was about 10 times better than the MRI! Finally, we started taking flat fields with various exposure times in the linear regime for each of the bandpass filters. For each of these filters we took several levels in mode 1, and then all modes at mid-level exposures. For a short-wavelength filter that had very low light levels for short exposures, we took many frames at very low light levels to study that end of the response curve in detail. We did filters 2, 3, and 4 tonight, and will continue with the other bandpass filters tomorrow night. The HRI filter table is appended to this report. At the end of the night's work we took two exposures of the integrating sphere in each of the operating modes of the IR spectrometer. The integrating sphere is currently being illuminated by one quartz halogen lamp with a color temperature of about 3000 K. For the spectrometer mode with the shortest integration time, only a few columns near 2.5 microns are saturated, but for the modes with two and four times the integration time, large parts of the array shortwards of the 2.6 micron cut-off of the fused silica chamber window are saturated. We will have to investigate reducing the brightness of the integrating sphere by a factor of about 5 to get all areas of interest below saturation. However, it was already obvious that we were getting useful amounts of signal in the area below 2.5 microns all the way down to 1.05 microns. For the first time we seem to be seeing fairly clearly the periodic transmission variation of the beamsplitter in the short-wavelength area. Also, once again in these quick looks we see no hint of the 5 micron ghosting that was so obvious before the installation of the baffle. Please let me know if you have any questions or comments. Also please let me know if you would prefer not to be included on this Flash report distribution list, or if there is someone else who should be included on this distribution list. Dennis ---------- HRI filters Number Center Width (nm) 1 650 >700 4 350 100** 2 450 100 3 550 100 9 650 100 7 750 100 8 850 100 5 950 100* 6 600 >700 * 950 filter is longpass ** due to materials constraints, cut-on wavelength is about 340 nm