The Wrap-Up (9 July 2015)

Manny and Eckhart went up to the LBT to wrap LBTI in plastic and remove some optics. The plastic wrap will help protect the instrument in case of water leakage in the dome during the monsoon season. The removal of the optics has several goals, including:

1. Adjusting the preload springs of the off-axis elliptical mirrors (OAEs) to make them stiffer, so as to dampen vibrations in the optical train in the central piece of LBTI.
2. Removal of the SPC to fix a bad hardware limit switch that was always indicating 'closed.'
3. Making way for new SPC and FPC mirrors.
4. Re-angling the DX and SX WFS windows.
5. Fixing an aperture wheel located in the telescope's focal plane.

In the image above, Eckhart poses for scale on the instrument platform in front of the plastic-wrapped LBTI. Below, Manny stands next to the 'bogies,' the wheels which allow the dome to rotate. Each wheel carries about 50 tons.

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June B Run: Descent (local 1 July 2015)

The heroic efforts of the MGIO software staff and our telescope operator Geno enabled the LBTI to negotiate the leap-second without a hitch. Alas, after every possible second of data had been squeezed out of the observing run, the LBT's summer shutdown was upon us. Manny came up the mountain and, along with an early-rising Amali, removed the NIC instrument from the telescope, lovingly wrapped it in a rain tarp, and craned it into a pickup for the drive home. The tarp was removed en route when the possibility of rain receded, and was frantically replaced when storms reappeared to the west. NIC arrived unscathed on campus in the mid-afternoon.


June B Run: A Leap Second of Clouds (UT 1 July 2015)

What did you do with your leap second? Tonight we stared at thick monsoon-y clouds for an extra second. And then (many hours later) we went to bed.

Here's the almost-full moon rising at sunset.
Moon Rise at Sun Set
There was also going to be a spectacular conjunction of Jupiter and Venus, but I couldn't see it behind the lightning. Here's a panorama from the balcony at sunset:
(Click to embiggen)
Sun Set Panorama
It was a bittersweet night as we say goodbye to Vanessa, who has put her considerable skills and efforts to work making the LBTI run efficiently, over her past several years as a PhD student at Arizona. It is time, and she is graduating and moving on to a postdoctoral position with the Gemini Planet Imager at Stanford and Livermore National Lab. Thanks to Vanessa's hard work and dedication, new people such as Amali, Eckhart, Carl, and Jordan are being trained so that the whole operation can keep running once she leaves. Out with a wimper, thanks to the clouds:
Amali, Vanessa, and Carl
As for myself, I came on this run to compare and contrast the operations and instruments of MagAO and LBTI. I have just recovered from a 6.5-week MagAO run and so it is fresh in my mind. First of all, let's marvel at all this monitor real-estate that LBTI has. Not only are there 4 monitors for the AO guis and webpages, but there is a monitor overhead with the weather station, and an extra little L-offshoot of the desk to set your laptop for taking logs:
LBTI Monitor Real-Estate
Just for a comparison, I set up the AO windows MagAO-Style on 2 monitors. Note that I placed my laptop in front with the logsheet, and my iPad as the weather station, and the dinner plate --- to really give you an impression of MagAO style. LBTI doesn't have the Fast-Mirror Viewer but they do have the Technical Viewer and the PT Spiral so I put those in that place:
MagAO Monitor Real-Estate
Now, when you think about it, the LBT has two 8.4-m mirrors (and 4 monitors for each AO system for each mirror) while Magellan has one 6.5-m mirror. So that means LBTI should have 1.67 times as many monitors as MagAO. I guess they rounded up.

So what have I learned, comparing and contrasting these 2 complex systems?

Well, while our AO systems under the hood are almost identical, the start-up and loop-closing procedures are quite different. Take the case of acquisition. With MagAO we slew to a target, the TO does a Shack-Hartmann with our guider, and then hands off a fairly flat wavefront to AO --- then we preset the reconstructor and binning, and close the loop with a 10 modes gain vector, and finally hit it with auto-gain for a final closed loop. LBTI doesn't have a guider, so there are low-order aberrations that the AO operator must take out by hand, by applying nanometers of wavefront to M2. This has to happen before the loop closes, so it is part of the acquisition the AO operator does. Finally, the preset for LBTI is a bit different than the MagAO preset, and seems to be a bit buggy in terms of timing out, so the AO operator often sets up the reconstructor and binning by hand --- which is also easier for LBTI because most targets are the same brightness. The 10 modes loop is a reconstructor not a gain vector, so that's why it has to be set by hand after acquisition, preset, and static aberration correction. So a very complicated system in a different way.

LBTI has many complicated operator interactions, since both the TO and the AO operator can control the ASM. It also has a "200% efficiency" element as we have with MagAO, in terms of 2 science cameras that can operate simultaneously --- in this case LMIRCam and NOMIC. This leads to some of the same conversations as we have between Clio and VisAO, where the LMIRCam and NOMIC operators communicate to make sure each has obtained the data before nodding or moving to a new target. However, the two telescope PSFs showing up on the science camera makes for additional complexity, in that the LMIRCam operator must do a test nod to figure out which PSF is which.

There are a couple things I miss from MagAO. One is the Fast Mirror Viewer that Alfio made to show the peak mirror commands vs. time --- it has become my go-to plot for monitoring the loop status. Here it is after an earthquake last month:
Earthquake MagAO
Another thing I miss is the chefs. Someone turned down the temperature of the visitor fridge at LBTI yesterday and the food was warm and smelled bad...

But what does LBTI have that we could use at MagAO? Vanessa, Amali, and the team spend a lot of time creating useful explanatory diagrams, so that the wiki is quite comprehensive and informative. Take a look at this diagram Amali made tonight --- incredibly useful for diagnosing wavefront errors on the pyramid:
AO Refs for Operators
A lot of work has gone into making LBTI operable remotely from Tucson, so things like the power controllers for the AO hardware are accessed via a webpage. Part of Vanessa's dissertation has been working on non-common-path aberrations, and tonight she showed me the method for determining optical gain, which is variable and thus necessary to determine before the amplitude of an NCPA can be known. For another thing, the telescope-level plots are extremely thorough --- for example, I can lookup the temperature of the steel struts in the telescope structure. And finally, the LBTI has 2 primary mirrors, 2 AO systems, and many modes --- from IR imaging to nulling interferometry. It makes for a complex instrument with a lot of amazing capabilities! As soon as these clouds clear up.

Lately we've been losing sleep, praying hard to be counting stars:
OK I can't get the embedding to work, here you go:


June B Run: INAF's Enough (UT 30 June 2015)

The dome opened shortly before 11PM. We took an abbreviated but decent dataset of a star-forming region in another galaxy for the LBTO partner organization INAF (the Italian National Institute for Astrophysics). This was followed with calibration observations of a close binary system for the partner organization MPIA (the German Max Planck Institute for Astrophysics), but clouds swooped in again before we acquired any useful science data. The dome closed around 1:30AM.

In the plot below, the blast of wind at the secondary mirrors marks the brief window during which the dome was open. Note the bifurcation after UT 07:00, where the dome swiveled from the INAF to MPIA targets.


June B Run: Planets (UT 29 June 2015)

The sky was heavily clouded the first half of the night, and resulted in the loss of a half night of LEECH survey data. The only interesting thing to see in the sky was a spider sitting on the all-sky camera. Then the clouds suddenly cleared around 2AM, but LMIRCam refused to cooperate. After several minutes of attempted restarts, resets, and a computer reboot, it finally decided to work again.

What followed was a slam-bang series of observations of Pluto, Neptune, and the Neptunian moon Triton, plus a handful of photometric calibrator stars, all packed into a tightly-squeezed observing window. Amid the Polycom-combined cacophony of the control and remote rooms, Pluto appeared as a faint splotch floating in the noise of a background-subtracted LMIRCam image. (The timing is important: Pluto is due to receive its first spacecraft visitor in only two weeks, and this provides the opportunity for complimentary datasets.) Neptune first appeared on LMIRCam as a swoosh of latitudinal clouds, but a filter change suddenly revealed the planet to be a blazingly bright, cloud-wreathed spheroid.

LMIRCam remained fixed on Neptune to the last— until morning twilight flooded the wavefront sensors, and atmospheric Rayleigh scattering reasserted its grip.


June B Run: Will it clear? Will it not? (UT 28 June 2015)

The night began with heavy clouds, and some rain. The clouds cleared briefly to allow the dome to open at midnight... but then worsened again and forced another closure after only 15 minutes of sky-time.

Finally the dome was able to open again at 2AM, and Vanessa spent the rest of the night conducting engineering tests related to non-common path aberrations.


June B Run: Rain (UT 27 June 2015)

Jordan prepared a delicious meal of bratwurst with the LBT grill. In the background, rain and occasional lightning strikes were visible off to the southwest.

In the end, the telescope did not open due to inclement weather. Vanessa spent some closed-dome time doing engineering tests involving optical gains for the SX side AO.


June B Run: Bear Down (UT 26 June 2015)

On their way up the mountain, Amali and Vanessa spotted one of the University of Arizona's reclusive and camera-shy local mascots within feet of a 'Smokey the Bear' fire warning sign.

In the meantime, Phil and Manny cleaned the LMIRCam bias boards and the extender card with an eraser and contact cleaner. To dampen SPC mirror vibrations, they added lead shot weights to the mirror and installed a solid coupler between the stage and the motor.

The weather during the first half of the night included heavy clouds, and some lightning strikes were visible from the control room windows. The dome was finally opened around 2:50AM, which gave us time to take some LEECH data of a single target. Unfortunately, the SX side AO system spat out panic messages, so only DX was used. (A restart of the SX AdSec software would be required the next morning.) Also, Phil's suspicions that the SPC mirror was the culprit behind the longstanding tip-tilt vibrations visible in the DX PSF appeared correct, as the DX PSF looked much better tonight than it did on previous runs.

(Real bear image thanks to Amali; Smokey the Bear sign image from the MGIO Journal.)


June A Run: Engineering & Wall-eyed Observing (UT 13 June)

This night was split between further engineering tests, and wall-eyed observations of a secondary eclipse. LMIRCam still had streakiness issues, even after turning off the camera to give it a few minutes to cool, and after tugging around some more on the boards. The effort involved Vanessa and Amali troubleshooting in the dome, Eckhart serving as radio/Skype call relay between them and Andy and Manny, and Elwood assisting via email. Eventually it was decided that the team would have to settle for readout channels that were relatively streak-free, while leaving anomalous columns between the channels alone. Later on in the night the readouts improved, presumably due to cooling.


June A Run: Engineering & LEECH (UT 12 June)

In the first half of the night, Vanessa continued her engineering program. LMIRCam exhibited some worrisome streaking, so Vanessa went to the dome and tried removing the LMIRCam cover and tugging around on the bias boards. This helped. The second half of the night involved LEECH observations. In the process, we came across an apparent binary, which, for once, was evidently a real binary (since it was visible in both PSFs), and not just a stray optical reflection.

Below is a photograph taken of LMIRCam's scarcely photographable electronics during troubleshooting.


June A Run: LEECH, finally (UT 11 June)

High and unstable levels of humidity prevented opening the dome the first half of the night. However, conditions improved somewhat to open around midnight, and a few hours of LEECH survey data was taken, though PSFs exhibited some instability from pointing into the wind. In addition, there were intermittent bursts of seeing.

The LMIRCam detector readouts exhibited lines stemming from residual elevation of temperature from the power failure a few nights ago, and from lowering the telescope at intervals. (NIC's mechanical coolers do not function as well at low telescope elevations.) In the image below, the temperature lacuna is due to the power outage itself:

If we zoom in on the last several hours, we see temperature bumps corresponding to (L to R) dome repair work, uninstallation of the retroreflector and Prime Focus Camera cryogen refilling, and the opening for the night.

LMIRCam's temperature should be no higher than 60 K. Yifan assiduously wrote a reminder to himself on his laptop screen to remind Vanessa to set a new temperature setpoint for LMIRCam once the temperature had dropped to 55 K.


June A Run: No Opening Again (UT 10 June)

The day began with the LBT shrouded in mist. The cloud cover cleared somewhat around nightfall, but humidity remained very high, and there remained a problem with rotating the dome after having powered back up from the power outage last night. Undaunted, team members courageously continued work on miscellany including non-common path aberration removal, PSF stability, and pool-playing skills.


June A Run: Further Tests (UT 9 June)

The sky was heavily overcast again, which precluded on-sky observations. Vanessa and Amali wanted to generate more reconstructor matrices for the SX side, which Amali thinks were underperforming at large binnings. Meanwhile, Eckhart took LMIRCam readouts to track movement of the artificial Arizona source as a function of telescope elevation. However, tests were interrupted at 10:20 local, when three local power stations failed, plunging much of the LBT into darkness and freezing the telescope at ~12 degrees elevation.

In the picture below, team members meet to discuss their next move. (Left to right: Peter, Vanessa, Josh, Arturo, Yifan, Ian, Eckhart, and Amali.)


June A Run: Pinhole Migration (UT 8 June)

The cloud system from Hurricane Blanca covered the sky again tonight. With the dome closed, Eckhart and Phil used the time to do a test of the UBC pinholes to see how much they migrate over the LMIRCam detector as the telescope elevation changes. LMIRCam wrote out image arrays with the SX and DX pinholes illuminated with the thermal L-band background (the artificial Arizona source could not be well aligned with the new pinholes), while the telescope was slewed down and back up twice. The DX pinhole went clear off the detector the first time, and still moved more than 100 pixels the second time. SX stayed more-or-less put. Phil thinks the DX migration may lie with the Slow Piston Corrector (SPC).

Phil's list of bad-weather engineering objectives for this run is filling up with checkmarks.


June A Run: The Clouds Part (UT 7 June)

Beneath ominous clouds, Phil, Denis, Andras, and Eckhart took an early afternoon constitutional on the access road, where they were momentarily pelted with hail.

Mercifully, however, the clouds mostly cleared at nightfall.

An attempt was made at achieving a nulling sequence. First, the system was realigned, and the shifting of pupil images with the roof mirrors revealed that there was an exceptionally good common optical alignment between the NOMIC and LMIRCam science cameras. (Both are needed, because the fringes are easiest to find by using a grism in LMIRCam, and this gives the operators an idea of where to look in NOMIC.)

Interference fringes were found, but closing the phase loop failed. The failure may have been attributable to the level of precipitable water vapor (PWV), which introduces chromatic-dependent phase variations in the wavefronts. (Correction factors vary with PWV levels, so the variation is not easy to remove artificially.) We considered switching to LEECH, but due to uncertain weather forecasts, we ended up shifting ahead Denis' non-redundant masking (NRM) program by one night.

The NRM sequence involved pointing back-and-forth between science star and calibrator with a NRM mask over each pupil to do interferometry. Denis says the data set is "useable," even though we were pointed into roughly 10 m/s wind for the whole sequence. Denis notes that there is some angle to the wind within which vibrations can cause significant problems, but that it helped that interferometry was being done NRM-style on separate mirrors, rather than between the beams from each primary mirror.


June A Run: Engineering Tests (UT 6 June)

The weather conditions forced the dome to stay closed, so tonight was a night for some engineering tests.

One finding was that significant ~300 Hz accelerations on the universal beam combiner (UBC) were found to arise when turning on the DX side AC power. Interestingly, turning the DX cooling fans on and off made no difference. The culprit may be another, more strongly vibrating fan buried in the LBTI electronics racks.


June A Run: IFU etc. (UT 2-5 June)

Initial tests of the integral field unit (IFU) were encouraging. Time was also spent on validating the AO systems and testing a CCD (for optical images, as opposed to infrared) by mounting it outside the LBTI beamcombiner, while still using the LBTI wavefront sensor.


Reconstructor Generation (15-17 May)

The team has been working in the 'remote' room at Steward to make new reconstructor matrices-- the matrices that allow correction for turbulence, given the input from the wavefront sensor. This was necessary to help relieve the innermost ring of actuators on the right-side deformable secondary mirror from excessive forces due to an imperfection in the mirror face.

Amali was very excited to see the effect of the first reconstructor matrix on the wavefront sensor pupils at the end of the first day (below), and the corrective effect of a later reconstructor on the phase error of the wavefront after having been aberrated by fake turbulence (image further below). The scratchy red line represents the uncorrected phase variations due to turbulence, as a function of number of correction modes; white is that which is left over after having applied the reconstructor matrix. The further down the white is from the red, the better.

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LBTI March Run: Night 9 (UT 10 Mar.)

Tonight was a LEECH night, though poor seeing forced us to break off of some targets. At one point the International Space Station coasted by overhead, and was captured as a streak on the All-Sky Cam. (The bright light is the Moon.)


LBTI March Run: Nights 7-8 (UT 8-9 Mar.)

We observed Jupiter's moon Io, and could see volcanoes! On the second night, following a pointing error with the telescope, we switched to LEECH targets.