Category: MagAO-C

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.

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.

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.

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.

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.

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.

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:

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))

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

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

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:

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.

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.

And we got some amazing data.

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:

It was a beautiful night.

We’re all quite tired.

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!

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.

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

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

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.

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

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

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.

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

Here’s the song of the night:

Have you ever heard that pigeons are the rats of the sky? Well, tonight we were contemplating that binaries are the vermin of the sky. The binaries we are talking about are “stars” that are actually two stars, only they are so close together that they weren’t discovered to be 2 stars by the early astronomy surveys. But when you have AO on a large telescope like we do, you find out that a lot of stars you thought were single are in fact binary. And then you are disappointed if you were looking for something else when you chose to look at that star.

Laird discovered a binary with the pyramid wavefront sensor tonight. The pyramid pupils were lit up diagonally, and he correctly predicted its properties (about an arcsecond separation, about equal brightness) before we even saw it on one of our cameras VisAO or Clio2. Here it is:

We have been looking at disks around stars recently. Here is a Clio2 image by T.J. of a star that was supposed to have a disk… but instead it was a binary star:

Kate, Alycia, and T.J. are heading down tomorrow, and our mean tiredness is going to go way up. Thanks for all your hard work, guys!

Tonight we got on sky about half an hour earlier than normal, to get some narrow-camera K-band flats, which have proved to be difficult to get enough light. I’ve made a new page with all the Clio2 calibrations, and I’m posting the flats as we get them. They are still not ideal due to an in-focus pupil glow that we think may be related to a slight pupil misalignment. Here we are opening up the dome the previous night:

And from the inside:

We miss Alfio, but things have been running pretty smoothly, which is a testament to the amazing software he left for us.

 

Although this post says day 18, we started the 2014A blog on “day 0” (the PI arrived on “day 1”) and it took 2 days to travel here …. so Jared, T.J., and I left our homes 3 weeks ago now, and it’s been 20 days for Laird.  In honor of that milestone, here are some pictures from the run that haven’t made it onto the blog yet:

And here’s a bird, but not a vermin of the sky:

Here’s a movie Jared took of the LCO whistler, watch/listen to the video and you’ll know why. Note how it tips it’s head back when it whistles!

My brother gave me some mp3’s of him playing some peaceful songs on piano, which has been nice to listen to when I need to focus on reducing data in the control room. One of them is Prelude Op 28-15 “Raindrop” and here’s a version of the song from Youtube:

Tonight we are happy to present you with the first release of the official trailer for the MagAO movie, directed by Alycia Weinberger.

Coming soon to a theatre or scientific journal near you.

We’re still here at LCO, observing star after star, seeing disk after disk, maybe a high contrast close separation point source or two, and we aren’t out of cookies yet. Here’s a few more things going on:

Alycia got a good picture of a cute little vizzy at the ASB which she posted the other day. I saw him or her tonight, and I’m sure this is a new animal that we haven’t been seeing before, maybe a young vizzy. In any case, it’s cute.

We are now totally on a night schedule. Here’s Laird, Kate, and T. J., heading down to a late breakfast before bed.

It’s always pretty here, and watching the sunset is our nightly ritual.

This came up last night. Man these guys are cool.