Tag: 2014A

After another busy night, I didn’t put together a substantive post. Thankfully, today was a beautiful day, with plenty of both literal and eye candy for the blog.

Francois played Easter bunny and hid chocolate eggs around the control room for all to enjoy.

 

Jared spotted our friendly local Easter “bunny”

 

And Jen had a new roommate when she woke up this morning

 

I took a few last photos of the local flora at sunset

 

Here are a couple more  stunning photos Jan Skowran and Yuri Beletsky took over the last few nights:

I feel like I’ve just arrived, and it’s already time to head home. It’s been a blast working with a great group of team members, telescope crew, and observers.

Until next time, MagAO!

Though it’s about 24hr door to door, I remind myself that it’s not so far in the grand scheme of things:

I’m guest blogging for MagAO tonight.

I came out on Thursday for Subo Dong’s run, and then I’ll be observing again on Monday. In the meantime, I’ve got some down time for a few days. Mostly I’ve been planning like crazy for Monday’s observations. A big thanks to the MagAO team for all of their help answering questions.

The free-time also means I can take leisurely walks up to the telescope and watch the sunset.

I’ve been hanging out in the control room, watching the operation of the telescope and the instrument, and generally trying to absorb as much information about the system as possible.

Practical tidbit: I’ve been working on a way to implement a 9-pt dither pattern on Clio.
This turns out to be non-trivial since the available ways to move are either to do an AB nod (which only gets you 2 points) or to move in X or Y (moving in both is a two-step process). Katie came up with a clever way to combine different AB nods so you can move efficiently, which saves time overall if the integrations are long. The trick is to split the exposure at each nod position into two, so you can repeat the last ‘B’ position as the next ‘A’ position. So the sequence is nod AB, nod BC, nod CD etc.

(I’ve also been spending a lot of time sampling the contents of the cookie cabinet).

Because I’m feeling silly and haven’t really been doing too much over the past few days:

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

 

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!”

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.

 

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!

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

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:

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

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.

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

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

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.

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.

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: