LGS-AO Acquisition
- Assume:
-
- We are locked on a target: the laser is propagating
and the loops are closed.
- There are 3 people involved: the observer, the OA, and the
LGS-AO operator.
N.B. the OA and LGS-AO roles may be combined.
- Before moving:
- Observer
- Gives OA the new object.
- If on-axis, give the science target (lgs=1 target)
- If off-axis, give the tip-tilt star for the science target
- LGS-AO
-
- Opens the loops and shutters the laser via the "Open Loops"
button on the "LGS-AO Acq. Widget".
- Notifies the OA that they can slew to the new object
- During Slew:
- Observer
- Set new rotator angle and mode
- LGS-AO
- Within the "LGS-AO Acq. Widget":
- Set AO Mode (NGS-AO, LGS-AO)
- Set DAR (usually Acq & Track)
- Set desired pointing origin (NIRC2, OSPEC, OSIMG) and notify
OA of the desired PO
- Click "Setup Bench"
- Check that the tip-tilt star's name, Rmag, B-V color, and
offset to the science target (if any) have
loaded. If not, ask the observers for that info.
- Acquisition:
- Observer
- Identify the tip-tilt object for the OA
- OA
-
- Center the tip-tilt object on the "REF-L" PO using "Adj
Pnt" so that FACSUM coords match the object
coords
- Send the object to the desired PO and notify LGS-AO
- Turn off ACAM to preserve its shutter
- Request permission to propagate the laser from the Laser
Safety Observers or verify no aircraft with TBAD
- LGS-AO
-
- Click "Aquire TT ref" from "LGS-AO Acq. Widget"
- If OA hasn't asked already, request permission to propagate
the laser
- Watch "TT Sensor Stage" widget to see that the tip-tilt star is
acquiring. If not, may have to abort
acquisition (from MAORI) and retry.
- Laser will propagate and loops will close automatically
- Once "LGS-AO Acq. Widget" reports "Acquisition Complete",
watch "LBWFS Manager" for the system to be
optimized.
N.B. "Optimized" will mean different things on
different nights and with different objects.
Bright tip-tilt objects will often show RMS
Wavefront errors of <100 nm. On dim tip-tilt
objects, errors may be >200 nm. Poor native
seeing and high windshake will also degrade
performance. There's only so much that AO can
do--remember: garbage in = garbage out.
- While waiting for optimization, inform observers that they
may take images of the tip-tilt object
without dithering.
- Once optimized, if the science target is off-axis, offset to
the science target if approved by the
observer.
- Notify observer that they are ready to observe
- While observing:
- Observer
- Run dither scripts to observe objects. Keep in mind that for
optimum performance, the dwell time in each dither
position must be at least 2x the integration time
of the LBWFS.
- LGS-AO
- Monitor the following:
- "TT Sensor Stage" to see that tip-tilt object counts stay
constant
- "WFS Intensity Display" to see the laser return
- "LUI" to see all green
- "LBWFS Manager" to see that the RMS WF error remains low and
fairly constant.
- "MAORI" to watch the loop status (especially after a dither)