= Control of the Radius of Curvature of some OMC mirrors =

we want(?) to be able to tune the g-factor of the cavity

in eLIGO, this happened because we had a heater as an actuator

in aLIGO this happens a little because the PZT bends the mirror surface

== Requirements ==
 * is this really necessary?
 * how much do we need to tune?