AO Acquisition Tool

There is a new AO acquisition tool, which combines the previous NGS and LGS AO acquisition tools, fixes several existing bugs (or "features"!) and adds a few new functions. The GUI can be started from the MAORI pulldown (AO acquisition tool) or from the right click pulldown when logged on to k2aoserver.

The AO acquisition tool in NGS mode The AO acquisition tool in LGS mode

Changes to the acquisition widget

The major differences between the new AO Acquisition Tool and the old NGS and LGS AO Acquisition Tools are the following:

New features
WFS and WFC configuration archiver (NGS only)
The archiver saves the state of the wavefront sensor and wavefront controller for each acquisition. The saved configuration can then be retrieved and saved next time the target is observed or when obvserving another target.
Auto offset to target (LGS only)
The telescope will offset to the science target immediately after closing the loops, thereby saving time on LBWFS exposures, etc.
Return to guide star
The telescope will return to the guide star.
Different AO pointing origins for TSS and FSM
All of the pointing origins will have separate definitions for TSS and FSM. This is to allow for the small differences between the position of the star using each of these two methods, which is crucial for OSIRIS.
Ability to redefine all the AO pointing origins (other than OPT AXIS)
Redefining the OSPEC pointing origin, for example, is to be preferred to defining a new position such as USER1 for where the OSIRIS pointing origin really is.
New functionality
  • Pop-up requesting magnitude information if this is not supplied in the target list
  • Checks the pointing origins before trying to acquire guide star
  • USER1 and USER2 pointing origins automatically get saved in DCS (no need to save through the DCS GUI)
  • Additional decimal place for the RA and DEC offsets
  • Can change the object or the seeing parameter without running "Setup bench" again
  • Sets the FCS and WPS stages to Manual for NGS and NGS-STRAP
  • The estimated guide star magnitude is written back to the tool in NGS mode (like it is for LGS)
  • Star magnitude is read again after "Setup bench" (like it is for LGS)
  • Sets STRAP and the WFS differently depending on whether the beamsplitter or the sodium dichroic is in place
  • Upon clicking "Setup bench", LGS mode is set to LGS fixed, Auto offset is set to OFF.
  • Clicking "Abort" in MAORI while in LGS AO shutters the laser
Decommissioned functionality
Several status lights
Many status light gave inconsistent or redundant information
Taking backgrounds
The Wavefront Sensor Intensity Display should be used for taking STRAP and WFS backgrounds
Setting image sharpening modes
The LBWFS Manager can be used to set the modes and many other LBWFS settings
Frame rate setting
MAORI or the WFS Camera GUI can be used for changing the frame rate (but not while taking data). We are still working on a permanent solution.
Operation

An Observing Assistant would operate the acquisition widget in the following way:

  1. Select the target list at the beginning of the night
  2. Once the object has been selected and the telescope is slewing, select all the options on the GUI
  3. Click on SETUP BENCH
  4. Once the guide star is positioned at the desired pointing origin, click ACQUIRE GUIDE STAR
  5. Once the guide star is acquired, you may offset to the science target using OFFSET TO TARGET only if the correct offsets are indicated on the dRA and dDEC boxes.
You may abort at any step by pressing ABORT on the MAORI AO Control GUI.

Using the archiver (NGS only)

The archiver only works in NGS AO. Every time time a target is acquired, the configuration of the wavefront sensor and the wavefront controller is saved (regardless of the "Load" setting on the archive).

No Load: By default, these saved configurations are not used ("No Load").

Auto Load To load a previously saved configuration with the same DCS target name, change the setting to "Auto Load". Whenever "Setup Bench" is run, it will check to see if it has a saved configuration for that target. If so, it will load it. If not, you will need to change the setting to "No Load" or "Manual Load".

Manual Load To load a previously saved configuration with a different DCS target name, change the setting to "Manual Load" (this could be the same target with a different name, e.g., Uranus-12UT and Uranus-14UT). Whenever "Setup Bench" is run, it will prompt you to select a saved configuration. Select a file or press cancel.

If you accidentally loaded a configuration from the archiver that you do not want to use, you can always select the mode you want and run "Setup Bench" again.

When to use the archiver
  • Observing object with unusual configuration (e.g., bright stars for IF)
  • When reacquiring an object after a WFC reboot
  • Observing the same object multiple times
When not to use the archiver
  • When clouds lead to an object having a variable apparent magnitude
  • When in NGS-STRAP or LGS mode
  • When observing an object with a different angular extent (e.g., a PSF star for Uranus). If you do use it, please make sure that you reselect the object after running setup bench!

Description of Options

Target: The target name according to DCS should appear on the text window whenever a new target is selected. Alternatively, the target can be entered manually.

Target selection: Default=AUTO Whether the target name is automatically entered in the text box.

Loading starlist: First, load the starlist by clicking L and selecting the target list in use.

Magnitude and color: When slewing to a target, you should see the target name, R mag and B-V mag update if these last two are listed in the target list. If not, then they have to be entered manually.

Science target offset: The RA and DEC offsets from the tip-tilt star to the science target.

AO Mode: Select from NGS, NGS-STRAP and LGS mode. If NGS-STRAP mode is selected, the tool will prompt whether you want the beamsplitter or sodium dichroic in place.

Pointing reference:

Set the pointing reference to be used at acquisition here. The current FSM or TSS image plane coordinates can be saved as any of the pointing origins (not just USER1 or USER2) except "OPT AXIS", which is at (0,0) by definition. If the USER1 or USER2 position is saved, the tool will automatically save the DCS pointing origins as well (there is no need to save it using DCS GUI). The image plane coordinates of the pointing references are the FSM or TSS positions shown, in millimeters. To send the FSM or the TSS to the reference position, click the corresponding TO REF button. The FSMs and TSS are automatically sent to the pointing reference when running "Setup bench" or "Acquire star".

DAR:

Differential atmospheric refraction compensation is used to keep the science object in the same location of the science detector as the elevation changes.

Turning DAR acquisition ON means that the science object will start in the correct location of the detector at acquisition. This is accomplished using the field-steering mirrors (NGS) and the tip-tilt stage (NGS-STRAP, LGS) to place the object. In addition, DAR correction will occur at every telescope move. There are no negative consequences to using DAR acquisition and it is recommended for every observation.

DAR tracking keeps the science object steady while the loops are closed.

For LGS, DAR tracking is accomplished by having the TSS track the changes to the differential refraction. DAR tracking should be on by default in LGS.

For NGS, this is accomplished using the tip-tilt control offsets: instead of trying to drive the spots on the WFS to the center of the quad cells, the spots are driven to the location that keeps the science object in the right place. If the offsets get too large (above 0.2 arcseconds), the correction degrades substantially. It is very useful for spectroscopy or any time long integrations are taken. Do not turn this ON unless the observer asks you to (please check).

Guide Star: DEFAULT=STAR

The guide star selected is the object used for the wavefront sensing (which is not necessarily the science object). For extended objects, a different plate scale (lenslet array) may be used. In addition, the centroid gain and other wavefront controller are set according to the guide star. Please select star if you are not sure what the guide star is.' In LGS AO mode, the object will always be LGS.

Seeing: DEFAULT=0.75

Please select the seeing, at V-band, that is most representative of the conditions. This information is used to set the centroid gain. You can get a seeing estimate by using the r0 meter.

Background: DEFAULT=AUTO

Whether to force the tool to take a WFS or a STRAP background. The default it AUTO, which makes the tool decide for itself whether a background is needed based on the magnitude of the star. At the start of the night, before 12 degree twilight, it is recommended to turn the WFS background to YES since the sky background will be high.

Setup bench:

Press this button after the guide star has been selected and the magnitude, color, pointing origins, guide star and seeing have been set while the telescope is slewing. This will cause the tool to

  1. Open all loops
  2. Set the WFS optics
  3. Set the WFC settings

Acquire guide star:

Press this button to acquire the guide star once the star is at the pointing origin. If you are in NGS or NGS-STRAP mode, you should see light on the wavefront sensor before you proceed. The script will

  1. Close the loops
  2. Take a wavefront sensor background if necessary
  3. Measure the intensity and reconfigure the wavefront sensor if necessary (NGS)
  4. Propagate the laser (LGS)
  5. Get the LBWFS going

Offset to target:

This button is active only when loops have been closed. It will offset the telescope to the target from the TTref, using the offset computed from the starlist or typed into the dRA and dDe fields (offset FROM TTref TO target). An abort during this operation will cause the telescope to return to the original position.

Return to star:

After an "Offset to target" has been completed, you may use this button to return to the guide star.

Loops: Open

Open all the loops and shutter the laser.

Loops: Close

Propagate the laser (in LGS) and close all the loops.

Check Counts (NGS only): DEFAULT=ON

If CHECK COUNTS is ON, the acquisition widget will check the apparent magnitude on the WFS and use this information to adjust the WFS. This feature is useful in case of incorrectly specified guide star magnitudes and to prevent WFS saturation. If there is a problem acquiring stars with this feature enabled (e.g., the magnitude fluctuates due to clouds or there is a bug), please turn it OFF

Auto offset (LGS only): DEFAULT=OFF

If auto offset is enabled, the telescope will offset immediately upon closing the loop but before configuring the LBWFS. The LBWFS will be configured after the offset is complete. This can save a few minutes if the astronomer is not interested in getting images of the tip-tilt star. This gets reset to OFF when running "Setup bench", so it has to be set for every acquisition. Please check with the astronomer whether they are interested in this feature.


For more information, please contact
.