DI I&T Testing Update Wednesday January 29, 2003 CML Latest update on the testing : The ITS CCD is still cooling as of 5PM today; it is expected to reach operating temperature by 6 PM. We are continuing to take dark current estimates, which are trending down exponentially. The MRI/HRI vibe test results have been updated. Further analysis of the frequency signatures from the second axis vibe show an additional change over Mondayıs results. While no further alignment change was found, the frequency spectrum change was large enough to concern the testers. The current plan is to do a few more diagnostic sine sweeps at low amplitude, to attempt to locate the weak link(s), if any, then tackle the system back in the clean room for reassembly. This will affect the upcoming IP testing schedule more than the 1 day slip we have already incurred (nominal start of IP testing Feb 8th). Don has just run a radiometry model of Jim Baerıs IR baffle design for the 45 degree port, using a 2" diameter entrance aperture. The numbers look encouraging ­ 300K gives us a peak of about 1000 DN at column 480, 350 K gives us a markedly increased max signal of ~ 5000 DN at column 480, and 400 K gives us some saturation at column 480. We look to have plenty of signal, even from the room. There should be enough difference between the SIRTF BB on and off for us to determine easily. If we can get this while filling the FOV, that would be great. An ND2.5 filter would be too much attenuation; the smallest ND filter available, the ND1.0 filter, may still be a bit too much. We can stop down the aperture instead using a filter holder to reduce the input signal. In a review meeting of the calibration testing plans, Don asked Bill and I if there were any changes to the nominal plan he had circulated. I mentioned that at UMD, we had found some systematic changes in the dark frames as a function of time after mode switches; while this was in the IR instrument, it could possibly also be found in the optical CCD cameras. The best time to test this is now, in the relatively relaxed ITS testing; so we have put a call out to Ken Klassen and Tony Farnham to ask which mode switches we should look at, i.e. the ones represented most heavily in the nominal observing sequence. We also went over the idea of testing the IP both pre- and post-bake out during the upcoming testing, in order to quantify the range of the focus changes in the HRI telescope due to water bakeout in flight, which has potentially become more important in a short flight scenario. Both Bill and Don felt that warm pre-bakeout, and both warm and cold post-bakeout testing was enough to separate the two effects on the focusing of the HRI telescope. The alternative, adding an approximately 5 day pre-bakeout cooldown cycle, was felt to be too expensive in terms of schedule and resources to warrant the extra information gained in case of a total or near-total bakeout failure.