J. Kissel, J. Driggers

A little more information / motivation here. 

There are 4 degrees of freedom when it comes to keeping the green arms aligned: X and Y arms, in both Pitch and Yaw. There are three optics involved in each of these systems -- each arm's ITM, ETM, and TMS. As such, we've constructed a sensor array that has three sensors for each arm: a green WFS A, a green WFS B, and that arm's ITM camera. We've arranged it such that WFS A (in the I phase) is "DOF 1" which is controlled by the ETM, WFS B (again in the I phase) is "DOF 2" controlled by the TMS, and the ITM camera is "DOF3," which is controlled by a little bit of all the optics; ETM, ITM, and TMS -- but mostly the ITM.

As such, each of these templates contain the error signals for each of these loops for the 4 degrees of green alignment. 

The goal during their use: 
Minimize (bring the absolute value toward zero) each of the sensor, or "error," signals, while maximizing the last signal in each template: the (normalized) power stored in the arms.

When you'll typically need these templates:
- Only when trouble shooting the green WFS alignment step of initial alignment, where the "trouble" is that every time the green WFS engage, it steers the arm (X or Y) off into the weeds (in Pitch or Yaw) and breaks the green arm lock. 
- We've found that this will only typically be after a particularly rough event on one (or several) of the chamber's isolation system, for example, an ISI or HEPI platform has tripped. (Or a maintenance day when the SEI platforms are brought down for a model change, or if there's been a site-wide power outage, etc.) 
- In such a case where you have to invoke this technique, it's likely that only one of the error signals is too large for the alignment system to handle.

Strategy:
- Be sure to turn OFF the automatic alignment before getting started. It's the auto-alignment that's the problem, so you must be sure it's not fighting you while you're manually 6pushing the optics to the right place. Do this by heading to the ALS controls overview screen of which ever arm and angular DOF you're fighting (X or Y,  Pitch or Yaw), open each of the WFS "DOF" filters, and turn ON a limit of 0.0 for each. (If you turn OFF the input or output, guardian will fight you and automatically turn these things back ON. No good.)
- Keep the alignment adjustments small (0.1 micro radians on each optic's slider), and make sure to write down where you've started on each so you yourself don't get lost in the weeds.
- Be mindful of the optic indicated by the DOF which has a particularly large error signal. If WFS A error signal is large, it's likely that the ETM should be adjusted.
- The error signals only should be used when the cavity is locked on a zero-zero mode. That means you've got to get the alignment most of the way there *by hand* before using this system. Further, you have to make sure that the *automatic* green alignment system is OFF so that it's not fighting your manual alignment.
- Most typically, it's the camera error signal that's large. Unfortunately that error signal corresponds to a degree of freedom that is control by all three of the optics, so use your best judgement as to which optic to try first (based on your knowledge of what happened to the chambers and optics prior to you starting the alignment process). However, if no major alignment changing events have occured, start with the ITMs. As usual, if you change the alignment of an optic in either direction and it only seems to make all metrics worse, or break the lock, then that's not the problem optic!
- Once you have the error signals relatively small (Under +/- ~1000 - 2000 counts for the WFS, Under +/- ~0.1 to 0.2 counts for the Camera), re-engage the auto-alignment by releasing the limits of 0.0 in each of the "DOF" filter banks.
- Rinse and repeat until the arm cavity stays locked on the 00 mode with the auto-alignment engaged.

In Jeff's first paragraph, he forgot to include the other 2 degrees of freedom: the input beam pointing, which is defined by the TMS for the green lasers.  So, there are 6 degrees of freedom for each arm.