July 2001 W. Traub SUMMER PLAN IOTA 2001 ===================== Remove siderostat flats 1 & 2, early July, send to Denton Vacuum for FS-99 overcoated silver, back about 6 wk later, deliver to IOTA by 10 Aug. target, reinstall. Removal-reinstallation by Marc and support staff, very carefully. Side fixtures on mirror are epoxied, so can stay in place for coating run. Shipping boxes exist, use FedEx. Marc and support crew. Write new star-tracker code to acquire 3 stars simultaneously. See separate memo for suggested details. Basic idea is to use tip-tilt mirror for spiral search (to vastly speed up the stepping time), to step and integrate (not slew) each new field (to increase signal on a given pixel of CCD and thus make detection quicker), to use auto-threshholding (whereby the computer measures the rms of the CCD response during dark-field exposure, and uses 5 (say) times this level as a criterion to detect star above the background noise), all 3 telescopes will search simultaneously and all will stop as soon as a star is detected (to cut search time by factor of 3), all shutters will close, then open one at a time until the telescope which found the star is identified, this shutter is then closed and the other 2 opened and the spiral search continued where it left off (not a new spiral, but the remainder of the old is to be carried out), the process repeated when a star is found with the 2-telescope pair, and finally the last telscope by itself searches, after which a mini-version of above is re-executed to find the possibly-wandered (but only by a few arcsec) stars, and finally all 3 are sent to their respective quadrants of the CCD and all 3 locked up, all in 1 minute or less, which is theoretically easy, based on experience with past star-tracking light levels and speed of response of the tip-tilt mirrors. Needs user-friendly interface. Angela. Exercise versions of star-tracker code throughout summer, after clouds clear, typically 1-4 A.M., weekly until perfect. Goal is 1 minute from time telescopes are at nominal star position until all 3 stars are locked up on CCD. Angela and Marc. Write new telescope solution vector code. First code can be based on Chip Coldwell's code in the Quadra, adapted to the Ultra-10; purpose is using this model first is to get something working quickly, in July. Goal is to reduce current error radius from about 60 arcsec to 20 arcsec, and to have working procedure in place, that any user can work with. Should include a list of stars, to be selected by code depending on season and time of night. Needs user-friendly interface. Angela. Exercise telescope solution vector code on tel. 3 while other mirrors are out for re-coating, then 1 & 2 after flats return and are reinstalled, until code operates smoothly and accurately. Angela and Marc. Second version of telescope solution vector code can be written at UMass, since they have a strong interest in this problem vis a vis the LMT. Pete. Clean up OT code for speed and interface useability. Pete. Clean up LD control code, for both LD 1 & 2, in both the laser fringe-count mode and the motor pulse-count mode, since we need all of these options. Marc knows the peculiarities, and can advise Angela. Need user-friendly interface and display of positon, laser voltage, status (e.g., when last homed and indexed, and whether laser has lost lock since last homed). Angela and Marc. Write new LD Yaw code, using mag-light in dome as guide, location of mag-light image on ST CCD before LD move as a reference point, and location of mag-light image after LD move as a command signal to tell yaw which direction to move, how long to run, then iterating, and ending with a plus yaw (needed to shut of yaw motor driver circuit on the LD carriage and thus conserve battery power). Note yaw light locus on CCD is diagonal at 45 deg, from upper left to lower right corner, so this is a 1-dimensional servo problem. Suggest simple servo commands like "on for 2, 1, 0.5 sec" depending on how far away light is from target. Iterate until centered within 0.5 small pixel on CCD. Note should calculate and display continuous centroid while LD moves, so can predict where light is after carriage stops, as sensory feedback to observer, and since mag-light may stop at a position which is out of the field of view, and we need to know which way to correct, else may jam motor on wrong side of travel. Will be a wonderful productivity aid, and will be praised by all when works. Angela for code, Marc for hardware. Remove ring on vacuum tank, make thread insert for bolt D, where thread is stripped and bolt not useable, run tap through other holes (A, B, C) to clean out as needed, have ring machined flat if not already flat (either the tank rims or the ring are warped, and clamping down on C and D is always very difficult, since vacuum seal usually has gap, and leaks), and replace on tank (carefully!). Marc. Make 4 new clamps for same flange, using leverage efficiently. Also obtain high-strength bolts, and grease threads, for same. Marc. O-ring for same vacuum tank end is getting stiff, and needs to be replaced, and RTV'd in place. Marc. Replace power supplies and motors on telescope 3, because present switching power supply unavoidably radiates or propagates pulses to other electronics, and in particular it adds pulses to the SD pulses from the Galil controller so that the SD will receive about 1-2000 extra pulses per sec while it is slewing at about 10^6 steps per sec, thus generating a 0.1-0.2 percent position error, typically amounting to 0.1-0.2 cm. Marc. Buy and populate new 36-inch black storge cabinet for optics, since present 3 cabinets are dangerously over-stuffed with expensive optics. Goes in corner near current cabinets; shelving needs to be cleaned up and moved elsewhere, either electronics area or machine-shop area. Marc. Laser interferometer test plate for telescope alignment does not hang properly in telescope 3 dome, due to slight differences in postion of sloping back plate with respect to vertical beam center line, and also due to different width of vertical support angle brackets holding up the double platform table on which interferometer unit rests. Careful measurement and some adjustment of tel. 3 metal needs to be done to accomodate interferometer plate. Marc. Air-conditioning consultant will visit site and recommend 2 units to be put in optics area, one perhaps in the south wall near the visible beam-combining table (with appropriate baffles or distribution tubing to prevent direct air flow onto table or dislodging of accumulated dust on ceiling and platform above table), and one in the south-west corner area near tank end or along west wall (similarly baffled from direct impingment of air and dust onto optics, especially if tank end is open). These units should have heating capability as well, for winter. The present air conditioner was installed in June in the window in the computer and people area, and has been running continuously at 70 deg. F since then, with very good effect on the comfort level of people as summer approaches, and also helping (but not sufficiently) to maintain a constant temperature in the optics area. Expect FLWO to fund, this summer. Marc and Steve Criswell. Baffles need to be devised, or beams need to be diverted elsewhere, from laser in LD hut, since the laser beams directly impinge on the star-tracker CCD, and probably as well on any visible science detector. Optics may need to be tilted, and baffles installed in the LD paths. A large baffle has already been installed at the LD -20 cm position, and it is useful as a beam guide, but does not exclude the off-axis laser ghosts beams which are the problem here. Wes and Nat, Sept. Tip-tilt platforms and piezos need to be installed for telescopes 1 & 2, to match the system already in telescope 3. Motors need to be added for remote platform control. Wes and Nat, Sept. Lights need to be added to the feed mirror positions, since it is very difficult for a non-professional to identify and center up on this mirror, at the end of a long path. Either a small few-watt christmas tree bulb or a set of 4 surrounding diodes aimed toward the viewer are needed. Remote on/off of course. Also helpful if same lights or a reversed set of diodes could be seen from to of stovepipe as an alignment guide to the person at the bottom of the stovepipe, with commands from the person at top of stovepipe, directing the precise azimuthal and radial position of the manhole cover, which at present is a frequent source of vignetting for non-professional aligner personnel. Marc. Intercom system is source of frustration for some of us, and it would be a relief if a 3-channel system could be installed instead, with no action needed by the observers except a simple on-off switch in the control room, and no volume or other adjustments to be made. Multiple microphones in lab area and control area are needed, so we don't have to hunt for these items and drag them across computers and optics. Marc. White target for telescope 3 is needed, identical to ones in other telescopes. Marc. Later (Sept.) need to ensure that center hole in this target is truly on the telescope axis, to 0.5 mm accuracy, all 3 telescopes. Wes and Nat. Assemble and test triple-scan platform. Wes Star-tracker and telescope solution vector and LD control and auto-yaw should be completed and tested by 15 September. Marc and Angela. Data acquisition and detector work and beam-combiner work will be done in Cambridge and Amherst throughout summer by people there, and ready for integration on-site 15-30 Sept. All. More voltage outputs are needed; 3 for scanning and fringe tracking, 1 for phase closure mirror; 6 for JPB's piezo controls of 3 fibers times 2 axes each, and 2 for yaw; total 12 voltages). Perhaps the new AO6 board can be retrofitted from 4-current and 4 voltages to 8 voltages, or we may need to buy another all-voltage board. CB com has one failed relay which needs replacing. Are solid-state versions available instead, as a later replacement if we need this? The ADC board needs to have several inputs provided, perhaps via BNCs. Some signals to be fed to it are the SD currents and error signals. A display of these needs to be arranged on the OT. We need a focus screw on the metal piece holding the SM fiber at the focus of the parabolas on the visible APD feed, and the infrared PICNIC feed as well. Science observing will start 1 October. --- RMG additions: Snout masks for PICNIC camera need to be designed and fabricated, for background reduction. Each beam combiner will likely require a different mask. Make steel fitting for PICNIC dewar valve. Return current valve to John Geary. Finalize implementation of motor controller for PICNIC filter wheels. Controller box made by ML needs to be tested and then control from VxWorks needs to be wired (via DIO card) and software needs to be written. Opto-switches need to be implemented. Current PICNIC electronics cables (for data and clocks) do not reach from the vicinity of the VME rack to the optical table where the 3T classical combiner will live. Longer cables need to be made if PICNIC interface really needs to be near VME rack.