Summary of Science Run: 16-31 Jan. 2003: Sam Ragland dated on 07 Feb. 2003

Hi All,

The secondary mirrors of Tel. A & B were realigned by Marc and Nat just before this science run. Hence, getting the telescope beams into the laboratory and realigning the star-acquisition CCD mounts took almost two nights. Thanks Nat!.

I made some science measurements on the third night but in the presence of strong laser background light on the star-tracker CCD. I opened the tank, improved the baffling and realigned the IOTA relay mirrors. Since then, I didn't have any laser leak problem. Then a storm passed by and I had a bad weather for more than a week. The sky cleared up, but the seeing was terrible during next two nights. I made lot of measurements, but mostly without a fringe tracker.

The last four nights were excellent and I recorded good amount of data during these nights.
  • Telescope Focusing: Looking at the stellar images generated by scanning with IONIC fibers, I got the impression that the focusing of Telescope A & B are much much better than Telescope C. To make this case stronger, the flux on PICNIC for Tel. A and B were about a factor of two more than that of Telescope C. But, later I noticed by looking through the alignment telescope that the focusing of Telescope C is not all that bad. Also, I noticed that the focusing of Telescope A is not as sharp as Telescope B. So, I suspected the IONIC alignment for Telescope C. I realigned the flat mirror and the dichroic (since I didn't want to touch the parabola) on the IONIC table corresponding to the Telescope C in order to improve the image of Telescope C as seen by the IONIC fiber. Now, the flux on the PICNIC and the star-tracker CCD are comparable for all three telescopes. I estimate the coupling efficiency of IONIC (under excellent seeing conditions) as 65% for Telescope B and about 40% for Telescope A & C. Both Telescope A & B images (as seen by the fibers) are elongated in one axis. Re-aligning corresponding secondaries may improve the coupling efficiency of IONIC. However, I believe that at this level of alignment, equally important is the alignment of the parabolas on the IONIC table.
  • Laser Leak: I did manage to keep the laser spots out of the star-tracker CCD, but they are there. It could be a serious problem when we have a more sensitive star-tracker CCD. So, it should be eliminated soon. Although, the indirect solution suggested by John is attractive, I think, we should try to find a direct solution to this problem. probably, any residual leak could be blocked with a Notch filter as and when required.
  • Long Delay server: Seeing the good performance of the ldelay server, I decided to run the 'server' program on the console. I didn't have to reload the server program during rest of my run. I killed the program just before leaving the mountain for security concern. I noticed that ldelay computer doesn't have 'xlock' application on it, although there are document files related to 'xlock' in this machine. I think, it's good to load this application and lock the display after launching the 'server' program. Now that the ldelay server is performing well, I don't see any reason to power it up though CBCOM. I think, ldelay should be powered directly, running all the time. If so, the existing CBCOM could be used to recycle power for the LD motors in order to save its life time. 'vxworks-start' and 'vxworks-stop' scripts could power on and power off LD motors.
  • Tracking failure with Telescope C: Telescope C fails to track at low declinations, while A & B are tracking well. OT says that the telescope is tracking with zero 'error' value and it reads the 'position' as 'command' value. But, the star is drifting at about the sidereal speed and it's not possible to acquire the target again. Is it an issue of telescope imbalance or telescope modeling?