Subject: HRI/MRI IP TV4 Flash report Date: Wed, 26 Feb 2003 21:50:35 -0500 From: Dennis Wellnitz Hi all, We once again started off the day today (Wednesday, February 26) with functional tests of the HRI and MRI Instrument Electronics at a temperature of 60 C, but this time at a power supply voltage of 28 volts. Both the HRI and MRI showed some problems with the stepping of the filter wheel motors, but there seem to be reasonable explanations due to the high temperature of the motors. These temperatures are much higher than any temperatures at which we expect to be operating them, so we are not greatly concerned. When the power supply voltage was raised to 35 volts for the HRI the motor ran as expected; that test was not done for the MRI. As the Instrument Electronics began cooling down we began working on setting up for the tests to be done as the system cools down. Once they had cooled adequately, we took through-focus pinhole data on the MRI through filter number 4, a 100-nm wide filter centered at 750 nm, to determine best focus at this temperature and to see if the slight ellipticity seen in white light for the MRI on Monday, presumably due to the wedge of the chamber window, would disappear. The images at best focus appeared nice and round. The best solution for focus was where we expected it, and gave a full-width at half-max of 1.51 pixels, the best seen so far, and very consistent with the requirement of 1.5 pixels! We then did another HRI through-focus pinhole measurement using filter 7 (100 nm wide filter centered at 750 nm), using a smaller pinhole than was used yesterday. The focus determination from those measurements showed minimal motion from the previous day's measurement, and gave a full-width at half-max of 1.7 pixels, far better than the requirement of 2.5 pixels! These results are very good portents for good results when we get cold. After looking carefully at the mass spectrometer out-gasing measurements for water, the focus measurements, and the expected bake-out time at the recorded temperatures for the starting water content, we concluded that the water content of the composite structures had been decreased to about 6-7% of maximum. For the cold tests we wanted it less than 10%, so at 4 pm we turned off the bake-out heaters, and shortly thereafter set the shrouds to 0 C to start cooling. In late afternoon, after the HRI focus work was completed, when the Instrument Electronics had reached -30 C we ran another set of functional tests of the HRI and MRI Instrument Electronics, this time at 28 volts, with everything coming out nominal. The last stage of the thermal cycling raises the temperature of the Instrument Electronics to 20 C, with a final test with the power supply at 28 volts. We will continue to vary the temperature of the Instrument Electronics between -20 C (cold encounter prediction) and +45 C (warm encounter prediction), and perhaps to the operational limits for thermal balance tests and to better understand the functional test results. We are measuring dark currents for the CCDs starting at 20 C, and will continue with those measurements every few degrees as they cool down. We will take a break to sleep and plan to set the shrouds to cool the system to -20 C overnight, so that we can take flat fields on the MRI and the HRI at that temperature in the morning. Then we plan to continue the cool-down of the MRI to -35 C for through-focus pinhole measurements at the ITS operating temperature. As soon as that is finished we plan to continue the cool-down to MRI and HRI operating temperatures. As mentioned earlier, we expect the MRI to cool faster than the HRI, so cold tests of the MRI are expected to begin before cold tests of the HRI. As we cool toward operating temperatures, we are increasing the number of Science Team representatives physically present to take performance and calibration data and to analyze the data as it comes in. To the group of representatives already present (Casey Lisse, Stef McLaughlin, and Dennis Wellnitz), we will be adding Mike A'Hearn on Thursday and Friday, Jessica Sunshine starting Thursday afternoon (if predicted snow in the east doesn't keep her from the airport), Bill Smythe starting Saturday morning, Alan Delamere helping out as needed on Saturday and Sunday, and Ken Klaasen starting Monday morning. 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