From rayner@galileo.ifa.hawaii.edu Tue Nov 16 11:04:28 1999 Date: Thu, 11 Nov 1999 19:18:37 -1000 (HST) From: John Rayner To: bergknut@jeans.ifa.hawaii.edu, denault@jeans.ifa.hawaii.edu, gching@galileo.ifa.hawaii.edu, kuwata@jeans.ifa.hawaii.edu, neill@galileo.ifa.hawaii.edu, onaka@jeans.ifa.hawaii.edu, rayner@galileo.ifa.hawaii.edu, rayner@galileo.ifa.hawaii.edu, toomey@jeans.ifa.hawaii.edu, vern@hokuhele.ifa.hawaii.edu, watanabe@jeans.ifa.hawaii.edu SpeX Progress 11/11/99 SpeX is now warm and open. I opened it up today to examine the prisms, gratings and spectrograph lenses. They look fine and the AR coats are intact. There were a couple of surprises during warming. After about 12 hours I noticed some coloured fringes on the polished surface of the dichroic turret box, and the outer parts of the PK-50 blocker just inside the side window looked opaque and milky white. On further warming the PK-50 opaqueness decreased but the fringes turned milky. All trace of the "frost" disappeared when the temperature of the cold structure reached about 200K, which is a signature of CO2. Strangely, I didn't see any frosting on the dichroics themselves which must have been the coldest things in the turret. On cooling the spectra shifted 30 pixels to the long wavelength so I expected to see the reverse on warming. Wrong. The spectra only shifted back by 8 pixels. Maybe this was stress relief? On Friday I repeated the flexure test of the GT, but with the cryostat now warm. The results were practically the same. So we can now test and fix the GT flexure warm. Following that, Greg rotated the cryostat 90 degrees so that we could measure flexure in the other axis. Whereas before we didn't see any evidence for flexure of the slits, in this axis the slits moved about 4 pixels in the guider images when going from zero to 60 degrees tilt. The direction of movement is exactly in the sense of the weight of the slit wheel compressing its axial spring by 0.1mm. (So you were right Vern.) Hopefully making this spring stiffer should fix things. Unfortunately removing the slit wheel and that bastard retractable baffle is a trip so before doing anything we should confirm that this is the problem. By removing the slit wheel hall effect cover I think we can push on the wheel and compress the spring whilst taking images with the guider. Similarly, we need to do push tests of the GT. Both the GT and slit wheel tests should be done before doing any of the planned mods: *New WARM TESTS Done 1) Measure spectral shifts, focus shifts going from cold to warm (measure under vacuum and in air) 2) Try to reproduce flexure of GT. Done 3) Measure flexure in different axes by rotating cryostat *4) Try to reproduce flexure of slit wheel FIXES/MODS BEFORE NEXT COOLDOWN 1) GT mods? 2) Replace focus stage ball drive etc. 3) Move spectrograph detector 2.0mm closer to lens 4) Metrology of muxes in mounts (so we know where to place the science arrays) 5) Put temp sensor on GT 6) Install and test new filter holder 7) Remove and paint baffle in DIT 8) Paint and install window baffles 9) Assemble and install as much of the cal box as possible *10) Slit wheel mods? *11) Fix leak in electrical feedthrough *12) Fix broken connector on GT motor (it was me) *13) Get guidedogm to read correct temperatures Darryl should plan on coming across next week (I'll give you a call Darryl). Thanks, John