Users Guide to The AutoAligner (tm)

Dualstar users can now make use of the automated CT alignment system. This system is intended to reduce the constant running back and forth to the delay lines to tweak the CT. However, note that it does still require the user to get the CT signal to begin with. The autoaligner merely holds the alignment.

The operational principle is simple: a camera is placed behind each of the dual-star beamsplitters (note that it requires they be installed, so single-star users are SOL for now). The camera has optics to reimage the CT-beams in the pupil, and it separates primary and secondary using polarization. The computer sitting next to the delay lines has a frame grabber. It calculates the 4 centroids of the CT spots (Primary North, Secondary North, Primary South and Secondary South), calculates any deviation from a set zero-point (set as part of the set-up procedure each night), and send commands to the pico-motors to correct the alignment.

The system operates at about 1 Hz bandwidth, and seems to keep things aligned quite nicely. When working you can switch stars multiple times without losing CT, and you don't have to manually tweak it every 15 minutes.

It is smart enough to realize when there is no CT signal (in which case it does nothing), and is (probably - still testing that, so don't rely too much on it) smart enough realize when the boresight laser is on. However, note that the picomotors are open-loop controlled, without limit switches, so Keep an eye on the system so it doesn't run away! Ignore that advice at your own peril (and whatever the h-ll you do, DON"T LEAVE IT RUNNING AS YOU GO TO BED, SAY, OR LEAVE IT UNATTENDED AND ON FOR A WEEK!

NOTE: When connecting/disconnecting the computer control for the picomotors, always turn off the power to the picomotor driver. Then plug/unplug the cable where it says "Disconnect here".

Here is how to run it:

At the beginnning of the night;

•  First, disconnect the computer cable between the 8732 picomotor driver and the computer, so you can do some manual adjusting. If you are experienced you can use the manual control option in the autoalignment program, but I find that you end up with a sore neck doing that.
• Tweak up the CT signal to your hearts desire. Note that you should see the spots on the monitors next to the autoaligner, try to put them near the tape markers by adjusting the fold mirrors (via picomotors) and you should see a CT signal. NOTE: Do a good job, because the system will only keep things as they were - it won't IMPROVE the CT signal, just stabilize it.
• Usually it is a good idea to start by putting both Primary and Secondary CT spots exactly on the (say) North CT corner cube (this prevents walking off by chasing local signal maxima). This is a 2 person job.  Then leave the North alone, and maximize the signal by moving South ONLY. Usually the signal will saturate even with ND 2 inserted in the beam.
• Now reconnect the computer control cable.
• Now you can fire up the autoaligner. If necessary, start up the PC. Hit "Cancel" when it asks for passwords and such stupidity. When you see the desktop, click on AutoAlign (v3).vi. If necessary, select PTI as the user, and AutoAlign (v3).vi to open. You should end up with a screen looking like this :(image to follow)
• Find the toggle between manual and auto control (lower left corner), toggle to auto. Four sub-windows should pop up, containing pieces of the images visible in the monitors to the left of the computer. (image to follow) Make sure that the little red double ring (indicating where it thinks the centroid is) is on top of the CT spots. If it isn't (e.g. due to scattered light in the image, you can adjust the background subtration: toggle the Background switch to "Adjust" and use the slider until the cetroid is better. Note that you should hardly ever have to do this).
• When you have the CT and centroid marker where you want it, hit "Set Zeropoint" (hold it down for a second or two). You should see two things happen: the red dot in the image should move to where the CT spot is, and you should see the X and Y numbers (green background) change. Do this for all four channels separately.
• Now close the loops by hitting the big Red button in the lower left corner labeled "Loop Control"  It should turn green and you should hear ticking out of the picomotors. You should also see the picomotor controller cycling channels "North Primary, North Secondary.." etc You can also disable individual channels via the small pushbutton in the lower right corner of each individual panel. It turns red when the channel is disabled.
• If any of the fake red LED indicators labeled "Wait" are illuminated on the panel then that channel is having problems, e.g. no signal, or it thinks the boresight is on.
• If the green fake LED's are illuminated it means it is working.
• The system should tweak away happily. Make sure you hear the picomotors ticking, and make sure the computer is hooked up.
• If you want to monitor it from the control room, use the PC next to hardcore. Click on the Radmin shortcut, and start up a session to 192.107.167.215. Password is written on the autoaligner computer. You should see a screen shot of the autoaligner computer - which is fully interactive, so you can open and close loops, etc.

Troubleshooting

• Is the Std Threshold limit set too low? If it is you will see the little red LED in the bottom of each cannel panel illuminate (Next to the control labaled Std Thresh). Increase the Std Threshold until the LED goes off. This is supposed to ensure that the system doesn't run away if the boresight is accidentially turned on.
• Is the channel disabled? If the big square pushbotton at the bottom of each channel panel is red then press it to enable the channel.
• Is the step limit reached? The big red LED in the Manual control portion of the panel will be illuimated. Select manual control, then reset the step counters. you could also just increase the step limit.
• Is the signal too weak? If the red circle is not on top of the CT spot the signal may bee too weak. Make sure the CT doesn't have an ND filter in the beam, and check that it is going down the pipe. Also make sure that the background subtraction isn't too big. You can adjust it by selecting "Adjust" and using the slider. The image should update. Choose a background subtraction that is a bright as possible but still has the red circle on top of the CT spot.

ben@huey.jpl.nasa.gov