1st ShaneAO Workshop

We had a very successful User Workshop on Dec 17 at UC Santa Cruz.

All the users, the instrument developers, and others interested were invited. Many came, and we had a lively discussion of ShaneAO capabilities, science uses, and plans for future upgrades.

Link to the presentations

Attending the workshop were:
Mark Ammons LLNL, Will Deich UCO, Gaspard Duchene UCB, Sandy Faber UCO, Ellie Gates, UCO, Don Gavel UCO, Lea Hirsch UCB, Kyle Lanclos UCO, Paul Lynam UCO (by video), Geoff Marcy UCB, Claire Max UCO, Rosalie McGurk UCSC, Mike Rich UCLA (by phone),  Connie Rockosi UCO, Angie Wolfgang UCSC (by Skype)

ShaneAO Status Report

Compiled for the UCOAC meeting at UCLA on Wednesday 5/21

Present Status

• ShaneAO has completed two engineering runs (one in April, one in May) 
• Now in the midst of the first shared-risk observing nights.
• We have commissioned both natural guide star (NGS) and laser guidestar (LGS) modes for observing. Most systems are checked out and working well: 

ShARCS

• ShARCS cold stop aligned to telescope pupil - much improvement in background over IRCAL's emissivity 

AO Natural Guide Star Mode

• Bright star NGS AO @ 1.5kHz correction - high Strehl (~0.8 ish, as expected in K) 
• Dim NGS down to 12'th mag - M92 picture was taken  with an 11'th mag NGS 

AO Laser Guide Star Mode

• LGS locked in 16x and 8x modes (16x, 8x = wavefront sensing at 16, 8 samples across the aperture respectively) - Laser is dim this time of year, so not much correction, but it locked and is stable 
• Laser uplink tilt correction working 
• Dim tip/tilt star in LGS mode, worked down to 15th mag., goal is 16th 
• LGS mode field steer to tip/tilt star >50 arcsec off-axis and lock

Observing Scripts

• Nod along spectrograph slit - done, but cumbersome, needs some work 
• NGS mode field steer - not very accurate and needs work - automatic nodding scripts close, but not quite finished. 
• Still needs to be done: 
• flexure compensation models for long exposures - needs data collection and implementation 
• field rotation (align along slit via Cass tub rotation) - needs checkout 

More info and pictures: http://lao.ucolick.org/ShaneAO/material/index.html 

Closed-loop PSF - J,H,K bands on-sky

From 5/15

Shared-risk science observer Tucker Jones was kind enough to let us collect point-spread function data at wavelengths across the near IR coverage of ShARCS.

Here's AO-corrected images on-sky in K, H, and J bands:

Point-Spread functions in 3 science bands, compared to open-loop seeing.
ShARCS pixels are 0.035 arc seconds.

The bright-star Strehl ratio performance looks remarkable. Looking at the H band star PSF and comparing it to the image-sharpened internal source, we can make a rough calculation of on-sky relative Strehl:

Strehl in H is around 78%*
*relative to internal calibrator

"Second Light" Engineering Run for ShaneAO

First night saw light overhead cirrus and reasonably normal seeing; about 1 arc second. The goals of the first night were to finish a few NGS mode engineering tasks and start on the LGS ones, then to continue on with deeper exposures of the science targets we started on the first light run. In particular we were able to take another exposure of the open cluster M92, using an 11'th magnitude natural guide star. The guide star appeared dimmer than last time, probably due to the cloudiness. This gave us a chance to tune up on dim star AO performance:

AO with a dim guide star. This was after adjusting settings for low signal-to-noise. 

The second night was beset by clouds and bad seeing, and we were barely able to get even the brightest star to have any signal on the wavefront sensor. The third night was heavy fog and rain and we didn't even open the dome.

Tonight, Friday looks hopeful for clouds clearing by evening. The laser is turned on for the next three nights and the LGS mode AO controller is in place, so we hope to get our first LGS guided images by the end of the run (through Sunday night). Several LGS mode operations and systems need to be tested for the first time on sky, so we hope to get a jump on that starting tonight.


Engineering tasks completed:

• Connected and verified operation of the high-voltage driver for the laser uplink fast steering mirror
• Calibrated 22 more field-steering positions for the wavefront sensor, adding to the set of 4 cardinal points we got on the first light run. We're going to fit a model to these in order to enable arbitrary position offsetting of the natural guidestar.
• We unveiled the GUI for image sharpening. Image sharpening is a calibration process that peaks the PSF on the science image by adjusting the wavefront sensor's definition of "flat wavefront." This cancels the internal aberrations in the science camera. We tested the theory that the image-shapening offsets need to have a scale factor of d/r0 to account for the difference of starlight and internal source size as seen by the wavefront sensor, and this works. We verified with improved on-sky PSFs over no offsets and over not applying the scale factor.

Results of image sharpening

• Validated the dim guidestar AO tuning parameters and closed down to signal-to-noise = 2 on the wavefront sensor. This is an about 11'th magnitude star. Noise is completely dominated by "sky background" noise. We need to investigate now whether some of this "sky background" is in fact caused by glowing lights from electronics boxes and other powered items on the AO bench! If this accounts for say a factor of 2 in background it could make a really big difference in terms of sky coverage in NGS mode - almost a factor of 10 improvement in sky coverage per additional magnitude deeper on a statistical star count basis.

ShaneAO First Light On Sky!

Within an hour of opening the Shane mirror cover on April 12, we had the telescope aligned into the AO system and closed the loop on a bright star, Phi Geminorum.

First, the background sky is used to align the telescope pupil with the AO pupil. Reni is happy about it.

This is "on-sky" closed-loop. Lots of Airy rings on Phi Geminorum!

See the first light photo album for pictures and movies of the events, which include mounting to the telescope, videos of the telescope pointing and instrument rotating, first light activity in the control room.

First light images and tests included

• closed loop images of a bright star
• offload of tip/tilt to telescope guiding (worked like a charm, the Alpao woofer tilt range is adequate between offloads)
• a closely spaced binary star pair - overlapping Airy rings!
• a spectrum of a star, and another after accurate nodding along the slit
• closed loop PSFs with a succession of dimmer magnitude guide stars (in NGS mode)
• closed loop PSF performance at several science wavelengths from 1 to 2.2 microns wavelength
• image of a star cluster (M92), nodded around the field - testing field of view and camera distortion - this is a beautiful demonstration of resolution change from AO off to AO on
• a planetary nebula (IC 4593) - testing imaging of diffuse structure
• the minor planet Ceres - test of resolution and low contrast detail
• closed loop on the laser guide star (but no science images yet; we still need to commission the tip/tilt sensor's closed-loop software, which will happen in our next engineering run)
• outgoing laser wavefront control experiments with prototype high power coated MEMS DMs from IrisAO

The ShaneAO commissioning team in the 120" control room

Stars in the M92 globular cluster

Link for further information, pictures, and presentations on ShaneAO:

http://lao.ucolick.org/ShaneAO

AO Control with turbulence plates!

This is from Tuesday afternoon.

We closed the adaptive optics control loop in simulated atmospheric conditions (created by a spinning phase plate in the telescope beam simulator). The AO system is correcting aberrations using both the woofer and the tweeter deformable mirror in closed loop at a 1500 Hz control update rate.

Click on either of the bottom two images to see a video.

Here is a video of the diagnostic screens. Notice how the "wind" blows from upper right to lower left on the DM screens (bottom two).

ShaneAO MEMS Installed

Success to report today:

In spite of very cranky computer hardware --

• a complete meltdown of the original RTComputer on Friday
• the heroic effort to rebuild everything onto a substitute machine Friday night and Saturday
• and it's still cantankerous: multiple crashes today...

We have closed the AO loop on the MEMS!

Explanation: the AO system is now assembled and aligned - this is a process that has taken the last 6 months. The final step is to insert the deformable mirrors. There are two of them: the "woofer" and the "tweeter".  The tweeter is the 1000-element MEMS device that provides the fine wavefront control. The mirrors were tested and pre-calibrated in the lab, so, for example, we know the voltages that when applied to the mirrors, make them flat to a fraction of a wavelength.

We installed and tested both DMs last week, and poked their actuators to make sure they were working. Thursday, the woofer was taken out and replaced with a fixed mirror in preparation for testing just the tweeter.

On the left is the PSF of the beam when the tweeter is set to its flat-voltage. The steps are:

• With the mirror voltages set to the known flattening settings and light going through the system, collect reference data from the wavefront sensor.
• Relax the mirror to it's nominal "out-of-the-box" shape (believe me, this is far from flat)
• Close the AO control loop, now sending updates to the deformable mirror at the 1000 Hz frame rate of the wavefront sensor camera.

The PSF goes from a very blurry blob to the image shown on the right. The static flat and the closed loop PSFs have very close to the same full-width-half-max (about 2.8 pixels). Further analysis and testing is needed to get a reportable Strehl number, but it's looking very good.

The "ghost" image you see to the upper right is due to a UV leak in the dichroic splitter. This won't be there (will be filtered out) in the Sharcs camera images.

...

I experimented with various adjustments, feedback gain and things called "integrator leaks". The real system behaves surprisingly close to the simulations (I did a careful job writing a wave-optics simulator that the RTCode can wrap around).

Here are some pictures of the control screens:

In the foreground is the AO operator's console, showing (clockwise from upper left):

Hartmann wavefront sensor    |   Light intensity on the pupil (of the wfs)

Control signals to the tweeter  |   Control signals to the woofer

The display in the background shows the PSF camera image. This is a visible wavelength CCD camera.

MEMS flattening voltages applied, statically

DM in "unpowered" state

AO control loop closed. Note the PSF brightens.

Command console: <<loop closed>>!!!

After some more settings adjustments with the AO control loop closed

<<loop open>>

This is a cute movie. I boosted the feedback gain until the system was just on the verge of instability. A note of explanation: To have control sent to the right actuator, the system must know where that actuator is on the wavefront sensor plane. This "registration" calibration was done last Tuesday. The alignment has drifted ever so slightly since then (a few microns). The result is the waves you see drifting from lower right to upper left. This is Helmholtz equation in action! The wave velocity is the registration offset divided by the control cycle time.

Sorry about the poor video shot from my cell phone. I need to learn to turn the phone sideways to shoot a movie!

Download a better video showing the waves (14Mb).

Acronomia:
AO - adaptive optics
DM - deformable mirror
RT - real-time (anywhere from 50 to 1500 Hz control loop rates)
RTCode - the software that runs in real time
RTComputer - the hardware that runs the RTCode