Our ranks are thinning — Alan Uomoto left today and I didn’t even get to say goodbye. Bye Alan! Thanks for all your help in getting us up and running!!
Bye Alan!
We are still engineering our many modes on sky and debugging telescope and instrument problems. One of our exciting new modes is Simultaneous Differential Imaging (SDI), which we tried out on-sky tonight!
Here is Kate operating the VisAO camera in SDI mode for the first time on-sky!
Our ASM is a beautiful piece of advanced technology, keeping our wavefronts flat at 1000 times/second (read Kate’s post for why!). But occasionally the slopes being sent cause the ASM shell to go into its safe position. It’s either the switch BCU or the BCU 39. We have a spare switch BCU (see below), but don’t have a spare BCU 39 with us. Hang in there BCUs.
Switch BCU
My mom would like to know what a vizcacha is — They are these little rodents, basically a rabbit, squirrel and kangaroo in one package, that live here at LCO and entertain us sunning themselves on the wall or hopping like kangaroos across the rocks! The official mascot of VisAO is Vizzy the Vizcacha:
And speaking of mascots, the Clio team have been wearing our UA Wildcat pride here at LCO:
Today we were down 50% of our tenured professors and 50% of our Italians. Phil left yesterday and Simone and Enrico left this morning. Therefore, I was a little worried because their presence is definitely missed. Luckily, it was a good night anyway!
Runa represents 50% of our remaining Italians. He keeps the ASM in good working condition, while Alfio keeps the loop closed.
We weren’t socked in with high cirrus like we were yesterday, so we were able to keep the loop closed much of the night. We focused through several of the filters in Clio (Clio has 10 color filters, 2 neutral density filters, and 2 cameras — so it’s quite a lot of modes to commission! Not to mention the coronagraphs, prism, and non-redundant masks!).
We also got nodding fully functional on Clio. Nodding is when you move the star to another part of the detector chip. This is important in the thermal infrared where you have to subtract adjacently-nodded images to subtract the warm sky background. We nod Clio by nudging the telescope pointing a bit. This causes the star to also move on the AO wavefront sensor and on the other science camera VisAO.
The AO system can handle the nods, and gets the star back on-axis for VisAO, but it takes a second or two. During that time, Jared has to deal with bursts of poor image quality on VisAO. So nodding is working, but now we are working on traffic control. We are working on getting a smooth operation between the two science cameras that allows Clio to nod without affecting VisAO’s image quality too much. We are working on taking darks with VisAO’s shutter closed during the bursts of poor image quality. Watch this video to see how we are dealing with the problem:
Here we’re enjoying some good closed loop images:
Laird, Jared, and T.J. admire the closed loop images and real-time WFE and Strehl calculation on VisAO
“You can look on either camera for good images!!!” – T.J.
“We’re nodding. Deal with it.” — Katie
“The loop is back. Deal with it.” — Alfio
“It’s ballpark super-well focused.” — T.J.
“Your advisor is telling you to take a break???” — T.J. to Jared Re: Laird
“Eat your vegetables at dinner. They’re good for you.” — Phil (T.J.’s advisor)
“Those are pretty high gains… it’s like we’re doing real AO!” — Laird (1.4 tt and 0.4 ho)
“Look at what Clio is doing to VisAO! It’s criminal! See, this is why you never use two science cameras simultaneously!” — Laird
“It’s a frickin’ miracle!” — Laird, commenting on having two science cameras operating simultaneously behind an AO system.
Katie and Laird take a picture for their various mothers.
Today we worked more on interaction matrices and calibrations during the day.
In the evening, Phil and T.J. spent some time optimizing and testing Clio. Clio got to move to the big computer in the Clay control room for the first time (instead of running it off Phil’s laptop). Here are some pictures of the big event.
T.J. is impressed by all the real estateOptimizing the systemT.J., Phil, and Jared working on their respective science camerasMeanwhile, I was running the AO loop
Jared is taking the slopes from the wavefront sensor and multiplying them by the reconstructor to determine the phase of the wavefront (including adding back in the high order terms that are above our cutoff frequency). He writes the residual wavefront error to the VisAO FITS headers. He also records the gimbal position so we know the position of the star in the image with respect to the center line set by the AO Pyramid. Jared has calibrated the gimbal position and the wavefront error using the focal plane. Soon, we will only need the VisAO FITS headers, not the images themselves!
The VisAO quick-look guiJared's VisAO software reports the AO loop status, the wavefront error, and the Strehl in real timeThe VisAO FITS headers record the WFE and the gimbal position, so in principle you can reconstruct the image plane without needing the actual FITS image
Sunrise from this morning:
Sunrise from this/yesterday morning.Moonrise from this evening.
Jared: I record the wavefront error and position of the star in the FITS headers.
Katie: So what do we need the VisAO CCD for anyway?
Kate: To calibrate the FITS headers!
We passed a big milestone today with the ASM working in closed loop with 400 modes at 1 kHz (the most complex AO mode)! This 400 mode interaction matrix has been made possible by the excellent trouble shooting from our friends at Arcetri Observatory, Simone, Enrico, Alfio, Armando and Marco!
It was such an exciting event that Alan Uomoto made a movie:
How did this happen? Well, yesterday the AO loop was struggling to close on the bumps we were referring to as Viscachas:
The Viscacha is a bump causing a dark spot in the Pyramid pupils at around 2:30 o'clock.
When the loop tried to close on this, we would get a higher and higher unstable patch of actuators trying to correct it:
Here is the ASM display after closing the loop yesterday on 200 modes at 600 Hz. You can see the commands on the bad patch at ~2:30 o'clock; the mirror is working hard to correct something there, but we didn't know what.
So Simone and Enrico figured out that we were actually getting cross-talk from the Pyramid, because the phase bump was so high. This is similar to a quad-cell Shack-Hartmann without a guard band, where a subpupil may wander into an adjacent subaperture. Here is Simone’s drawing where he works out the solution:
Simone's drawing to solve the problem of the viscacha
So the solution is kinda a hack, whereby we applied a negative sign to the interaction matrix for that patch — and the bump and the viscacha disappeared!
Evolution of the Viscacha -- Final rendition, all corrected!
And so tonight we were able to close the loop with our new interaction matrix, and get a nice flat wavefront!
Result: Closed loop, flat wavefront, no viscacha!
New arrivals today: T.J. Rodigas (Steward) and Runa Briguglio (Arcetri).
