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2014A Day 23: It’s good to be back

Hi everyone!  With the beautiful weather and amazing avocados for every meal, it’s good to be back on the mountain again!

The obligatory selfie in the funhouse mirror.

 

Because MagAO is now open to the public (so to speak) and we’re executing a variety of programs, I’m learning about a wide range of science projects.

Of course, there’s the “run of the mill” high-contrast imaging with VisAO. See the ring around the star in the image? That’s not a disk of material around the star; it’s a sign of a beautiful AO image. With very high-quality correction, the star’s light in concentrated into the core of the star image, leaving a “dark hole” around the star. The better the correction, the deeper the hole. Outside the hole, at the “control radius,” is a ring of small uncorrectable residuals. They look really prominent here because of the stretch, but they’re actually incredibly faint. At the right edge of the picture is a faint reflection, or ghost, of the star; you can see how tight the core of the star image is and how very faint the ring is by comparison. As Laird put it, “We get better quality on our ghost than most people do on their images!”

Beautiful H-alpha image from VisAO. The wavelength of this light detected here is ~650nm, which your eye would see as red.

Switching gears, we also took wide-field images taken of stars toward the “bulge” in the central regions of the Milky Way. After spending so much time taking really sensitive images of single star systems, I’d forgotten Clio could take images like the one below! Subo, Ping, and Jen are following up “microlensing” target hosts with these data. Microlensing is a sweet technique for indirectly detecting planets around other stars. The gravitational pull of a massive object like a star or planet can actually bend light passing by it, creating an effect similar to how a glass lens bends light that passes through it. An everyday magnifying glass uses this bending of light to magnify objects. In the same way, a “gravitational lens” can magnify objects behind it via the gravitational bending of  light. So if a planet and star just happen to pass in front of a more distant star, they will briefly magnify the light of the distant star in a particular way that astronomers can use to measure the mass of the planet – pretty wild! High-resultion imaging helps to constrain the planet models, so we followed up several different planet candidates as part of this program.

I’ve never seen so many stars on Clio before!

 

AO was running very smoothly for most of the night tonight under Katie’s watchful eye (the screen saver went on several times because nothing needed adjusting for so long!). We also had our first guest AO operator tonight. Dave Osip stopped by for a while to check in, and we roped him into operating for a while. It’s a good sign for the usability of the system if we can start having guest operators – thanks to the AO team for all the user interface and hardware reliability improvements!

Dave takes a turn at operating AO.

And, of course, I went wildlife watching.  From the control room window at dawn I saw a couple vizzies hopping on the rocks below.

Good morning, vizzies!

And I’ll leave you with a very serious analysis of the vastness of the universe in song form. Including, perhaps, a postulate on multiverse theory:

2014A Day 22: Grumpy’s Back!

The big news of today is that our favorite Viscacha made an appearance at the clean room wall today. We’ve been missing him!

We hadn’t seen the old man, Grumpy Viscacha, Vizzy himself, for a long time. We were getting worried. Yes, he’s still grumpy looking.

After a few days of Engineering and Arizona science, we welcomed Subo Dong from Peking University to the Clay telescope. Jennifer Yee (Harvard), who is observing in a few nights, was also here to help out and see how things work.

Jared, Subo, Jennifer, and Katie set a record for most Sagan fellows (current or past) using MagAO at one time.

We continue to make progress in improving the quality of MagAO operations.

This blog gets results! Here we see logs being taken by the AO operator.

The MagAO team is thoroughly nocturnal now. But that means our food is eaten in the wrong order by all standards of civilization.

Katie’s breakfast. Which was really her supper. Or whatever you call the meal before you go to bed.
Just some flowers cuz I saw them today.

Finally, we have a clarification from Katie’s post about all of our control loops. Though not specifically annotated, the VisAO Gimbal was shown on the diagram, and you just have to know where to look for our X-Y-Z stages.

The board GUI (code by Alfio), with extra annotations to show where everything is. Today’s free-sticker-question: what’s wrong with our X-Y-Z coordinate system?

Listen close to this song, and you’ll hear an entire verse about adaptive optics. Plus, once you’ve been on a month long MagAO run you’ll know what Bono is saying, though maybe not in spanish.

2014A Day 21: Loops of MagAO

A closed feedback loop is when you are monitoring some output so that you can control some input. How many closed loops does MagAO run? Here we present: The Loops of MagAO.

The top-level loop: The AO loop.

1. The AO System’s Pyramid WFS and ASM

The top-level loop is the adaptive optics (AO) loop. This is the loop that all the others are here to serve. We are making flat wavefronts so that our science cameras can take sharp images, and it is a serious business.

How a closed-loop AO system works: Your flat wavefront in space is distorted by turbulence in the atmosphere.  The distorted wavefront encounters the deformable mirror at the telescope (the ASM), and a beam splitter sends the bluer light to the wavefront sensor (WFS), where a control system calculates the shape of the wavefront, then applies the opposite shape to the ASM.  The corrected, flat wavefront is then sent to the science camera (Clio2 or VisAO).
The AO system in control
Me running the AO system a few nights ago. Dear Laird: Do you notice how I’m taking logs?
And when everything is running smoothly, this is the AO Interface that the AO operator can use to close the loop

2. The Camera Lens

This loop is my favorite, because it’s one of the subtle calibrations we do that keeps our AO system one of the best in the world. The camera lens loop keeps the positions of the Pyramid pupils aligned to the pixels on the WFS CCD to a tenth of a pixel. This means our AO system is always calibrated, in the way that it measures brightness and on the CCD and converts it to slopes to send to the ASM.

The camera lens loop is my favorite. (Well of course, besides the AO loop). Left: The light falls in these 4 pupils after it hits the pyramid, one for each facet. Center: We measure the position of the pupils in software (red cross-hairs and thin circles). Right: We compare the measured positions to where the software is expecting the light (blue and red lit-up pixels), and the camera lens loop moves the camera lens to line up the pupils with the pixels we want them to fall on.

3. The 585 ASM Sensors

The ASM has 585 actuators to control its shape at 1000 times per second, and they have sensors to control their current and check their temperatures.

The subtlety is that the mirror shape is actually controlled by the DSPs upon the back of the ASM itself.
The control electronics for the MagAO ASM
Keeping house
The ASM housekeeper tracks the temperatures, currents, and forces of the 585 ASM actuators

4. Telescope Off-loading

We send some of the wavefront correction to the telescope — we call this off-loading. For example, if the ASM has to tilt too far to the side and starts to use up all its “throw” or stroke, then we just send a little nudge to the telescope and re-point the whole telescope, flattening out the ASM. We do this once per second, and we off-load focus once every minute.

5. VisAO Coronagraph Guider

Jared wrote a little opto-mechanical loop for VisAO in coronagraph mode. He nudges the VisAO gimbal mirror to keep the star aligned precisely behind the coronagraph. The loop runs once every few to tens of seconds.

Jared running the coronagraph guider loop on VisAO
Here we see the offsets scrolling by, and finally a gimbal command at the end
The coronagraph guider in action

6. Clio Temperature Controller

The Clio2 optics are kept at 77K via the outer dewar, by the LCO staff who refill its liquid nitrogen dewar every morning. The Clio2 detector is kept at 55K by a pump that lowers the pressure of the liquid nitrogen and makes it solid inside the inner dewar. However, the pump could keep lowering the pressure and thus the temperature even more, but it’s important to keep the temperature stable. Therefore, we have a heater that senses the current temperature, and turns on a bit when the temperature is below 55 K, and keeps it always at 55K. This is a closed feedback loop.

The Clio temperatures

7. Mechanical Loops with Encoders:

We also control a lot of mechanical components using encoders. On the WFS/VisAO board, called the “W-unit”, we have the Bayside stages X, Y, Z; the PI piezo Tip/Tilt mirror X, Y; the camera lens X, Y; the two atmospheric dispersion compensators (ADCs) and the re-rotator (K-mirror); the beamsplitter and the two VisAO filter wheels; and the gimbal motors X, Y. That’s 15 encoders:

All the things on the wavefront sensor and VisAO that move mechanically and with encoders

8. Finally, the telescope itself has several mechanical loops: Elevation; Azimuth; the Dome; and Active Optics (the primary mirror M1 has ~150 actuators controlled via a closed-loop Shack-Hartmann (plus the 5-d vane ends (x,y,z, theta, phi))

The Shack-Hartmann guider loop
The back of the primary mirror, where there are actuators controlling the active optics

Well, I lost count, but that’s a lot of control loops! And when it’s all working, this is what we get:

60 milli-arc-second PSF at H-band on a 7th-magnitude guide star. That’s really good! Also it has a faint companion…

Well, that’s it for tonight, suffice it to say we had a good busy night on sky.

The moon to the west, at sunrise, from Clay
The moon setting as the sun was rising, the morning after the lunar eclipse

The song of the day has an astronomical theme, is by a top South American artist, and it came out on Vevo the day we left Tucson for this trip:

Here’s another good one by Shakira, from when the World Cup was in South Africa, it’s in the top ten most viewed Youtube music videos of all time:

Speaking of the World Cup, I’m happy to report that there is a soccer field at LCO! But it’s near the gate and we never go by there, so I’ve never seen anyone playing soccer here.

2014A Day 20: Spares and backups

Vanessa arrived safely today after boarding 6 planes (but only traveling on 3) to get here. We are happy to see her! She is helping with Clio2 engineering as well as AO operations. We also had 2 of our observers arrive today; their run is in a couple days but they wanted to get up to speed on the system. Unfortunately, we couldn’t show them much at the start of the night, because while closing the loop on the first star, we had a hardware failure that got us pretty worried for a few hours. The ethernet module on our slope computer failed. Luckily, we had a spare, and Jared and Laird put it together without any help from our Italian friends who were all sound asleep in Tuscany.

Two photos of the spare BCU 39 slope computer
The failed ethernet module (top) was swapped out for the spare (bottom)

After they got that fixed (in the mean time, Vanessa and I were working on the CLio computer backup), we got on sky. We had amazing seeing tonight.

I know there’s a reason we picked this site.

And we got some amazing data.

A bright star behind the coronagraph on VisAO at i’ (770 nm) with very high Strehl

We also took some spectral-differential imaging (SDI) data with the Wollaston beamsplitter in to divide the light into the narrow-band and continuum beams. Here is Laird inserting the Wollaston, which he has to go up to the instrument in the telescope to do:

Here is Laird inserting the Wollaston by feel and sound

It was a beautiful night.

The ASM by moonlight.  Photo courtesy Prof. Laird M. Close.
The Clay telescope by moonlight.  Photo courtesy Prof. Laird M. Close.

We’re all quite tired.

The P.I. with his Fanta

But seeing Raphael and Pele dance it up on Xai //na gomasen is quite energizing!

And you can see their dancing much better in this video, I love the Namibian dance style!

2014A Day 19: The Shadows Of The Night

T.J., Alycia, and Kate left us yesterday. Vanessa was supposed to be here, but her flight was delayed. So, it was down to Laird, Katie, and Jared to carry on the MagAO mission tonight.

Our day started early. We had to get up before dinner to do some maintenance on our shell wind monitor. This is a little anemometer attached right at the edge of the secondary mirror to tell us if the winds get too high. One flaw with our current device is that it is battery powered and the batteries only last about 10 days. So the crew tipped the telescope over for us, and Laird and Katie climbed up to replace the batteries.

Laird and Katie replacing the batteries on the wind monitor.

After that bit of periodic maintenance was taken care of, we headed back down the hill for our usual breakfast.

We have a nice steak dinner just about every evening — for breakfast.

After that we headed right back up, and closed the loop. Our minimum number of planets detected tonight is 1 (100% confidence). The maximum number is 4, with a most likely value of 2. Stay tuned.

How the AO system looks when it’s running well.

Tonight was a little bit more interesting than usual, since we got to enjoy a total lunar eclipse. We knew we were in for a special night when we saw the moon rise over the Andes on our walk up to the telescope after dinner

The moon looked almost shy.
Let the show begin!

With only 3 of us to operate MagAO, Clio2, and VisAO, plus Ernan our telescope operator, we had to watch the eclipse in shifts, leaving one person inside the control room to come holler if something went wrong.

Laird worked hard to get some nice shots of the dark moon.

The eclipse as seen from just outside the Clay control room.
Laird might have had too much caffeine before taking this shot. He might also be over-driving tip and tilt.

When the moon is full here, the mountain top is really really bright.

Clay, containing the MagAO system, by the partially eclipsed light of the moon.

MagAO also obtained world-wide coverage of the eclipse. Well-planned, I say.

The departing members of the MagAO team saw the eclipse from the Miami airport this morning.

On our walk up at sunset, the Moon and Sun were 180 degrees apart in the sky. On our walk down at sunrise, they had nearly exactly swapped positions. Mornings here can be stunningly beautiful.

The moon, now opposite the sunrise. Free MagAO sticker to the first person who emails me the name of the pink band on the horizon (hint, the answer is in a blog post from last April).

You might remember that this isn’t the first time we’ve observed an eclipse at LCO.

Here’s the song of the night: