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.


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.


LBTI March Run: Nights 3-6 (UT 4-7 Mar.)

These nights included a "high resolution companion search towards a sample of the lowest mass members of the Taurus star-forming region," in order to "investigate the effect of companions on disks, in particular transition disks and truncated disks that may result from dynamical interactions." It may also be possible to see their effect on any young, thermally active planets that are discovered in the process. (Quoted text from J.B.)

Here are some example plots of a single star and two binary systems that were imaged:

(Image credit also J.B.)

And how big is a 2 x 2 arcseconds, anyway? Well . . . LMIRCam's full field of view is about 10 x 10 arcseconds, which would be enough to inscribe only a piece of the International Space Station as it flies overhead:


LBTI March Run: Nights 1-2 (UT 2-3 Mar.)

A total loss! These nights were weathered out.


LBTI February Run: Night 8 (UT 9 Feb.)

Tonight we took more observations of LEECH targets, though we were harassed by bad seeing. Around 10PM it was particularly berserk, veering between 2 and 5 arcseconds, which forced us to move to another target. For a few minutes the seeing was, quite literally, off-the-charts.


LBTI February Run: Night 7

Can you see our solar system's zodiacal dust disk in the image from the all-sky cam below?

If we draw an angle between the disk of the Milky Way and our own zodiacal dust, we can see that the solar system is tilted by about 60 degrees relative to the Galaxy.


LBTI February Run: Night 3

The goal of last night was to carry out extensive nulling sequences on bright and then faint stars. While we had clear conditions, the PWV increased during the night, and we found it essentially made our attempts to record calibrated null sequences useless. Consequently, we switched to the LEECH program for the second half of the night.

We started by carrying out further testing of the phase loop. We saw similar behavior to the previous night (350-450 nm RMS). In checking out the system, we uncovered a problem with the fringe "hopping" code. This is intended to bring the phase loop to the correct OPD, by jumping one wavelength whenever it detects an asymmetry in the fringe envelope. After fixing the problem, we noticed much smoother behavior in our phase loop. Indeed, this may have solved the majority of the phase loop "break" issues. The rest of the night the loop behaved much smoother than it had any previous run. Conditions were average to mediocre for seeing (1-1.3 ") so this was encouraging. At this point, the PWV was 3.8 mm.

We carried out 8.7 and 11.1 nulling sequences to understand the phase stability in each passband. We noted that the tip-tilt stepping for 8.7 needs to be set differently.

We then moved to a HOSTS target to carry out nulling sequences. Setting the best set-point was significantly more difficult than our attempts the previous night. Indeed, when we looked at the data we were seeing nulling variations of 10-15% over 10s timescales. The cause appeared to be the 5 mm of PWV . Simultaneous LMIRcam dispersed fringe data were acquired, so we have data to learn whether this can be used to modify the NIR set-point.

There are two problems with high PWV. The first is that it adds phase variations to the null sequence. However, this should be random, and average down, even if it decreases our precision. The second problem is that it becomes difficult or impossible to measure the correct set-point for obtaining a good 10 micron null. This results in the sequence having few frames that measure the true null depth. Essentially, we can end up taking junk sequences in bad PWV conditions.

Looking back at our null stability over our past several attempts we see a clear trend. Here's the rough numbers:
UT Date PWV (mm) null stability (PPM)
Nov. 9 3.6 80
Nov. 10 4.6 100
Jan. 10 6.5-7 unusable (>300?)
Feb. 3 2.5 70
Feb. 4 5 unusable (>300?)

This suggests we really need <4 mm (<3 mm preferred) for usable nulling data. This is reasonably common. The SMT, next door tracks these statistics. You can find there statistics at:

Note their data is in tau_225. The conversion to PWV is PWV=20*T_225. Looking at their data we can expect < 3mm 30-50% of the time.

Going forward, I think we need a two prong strategy:
  1. Develop queue scheduling that allows HOSTS to use dryer conditions.
  2. Develop an algorithm that uses the LMIRcam fringes to track the water vapor dispersion.
Both of these are likely doable, although timescale and effort needed are still open questions.


LBTI February Run: Night 2

We characterized the vibration at the beginning of the night. The symptom was a strong peak (~300 nm RMS) at approximately 100 Hz We tracked this to a malfunctioning fan in the NIC electronics rack. This was turned off for the night.

We still appear to see higher than typical noise at 176 Hz, but the RMS was consistently 350-450 nm RMS, similar to November.

We carried out bright star engineering. We confirmed that we were able set the null reliably and set up a procedure for routinely coming to the same spot for set up between different stars and nods.

Observations were taken of a calibrator star to compare long and short DIT. Betrand and Denis analyzed this, suggesting slightly worse systematics for 60 ms, but both comparable (or perhaps better?) compared to November.

Clouds cut our nulling sequences short at 3 am. We continued to look for vibrations sources (it's not the L-N rack) and tested path length offloading.

The new NOMIC computer worked reliably all night.


LBTI February Run: Night 1

A snow storm dumped a huge amount of snow on Mount Graham Thursday through Sunday last week. Because of this the road was almost impassable for our first night. We elected to observe from Tucson.

A dedicated effort to clear the snow off the building was made over the weekend by the observatory staff. Thus, despite it snowing on Sunday, we opened essentially on schedule Sunday evening.

Conditions for seeing were good to mediocre throughout the night. We carried out a new alignment procedure for pupil overlap which, we hope will improve null depth. Throughput data at 11.1 and 8.7 were acquired.

Phasing loop parameter refinement was carried out. We found that under good conditions were were reproducing the 300-400 nm RMS phase variations seen in November.

The big problem for the night was a vibration seen in the data at ~100 Hz whenever we were above 50-60 degree elevation. Attempts to identify and mitigate it are ongoing. The effect is large enough to prevent us from getting routine closed loop data.

NOMIC computer is occasionally crashing and needs to be replaced. We are headed to the mountain Monday during the day to be able to work on these various problems more efficiently.


LBTI January Run: Nights 7-8

It was looking grim. It snowed on Wednesday night and into Thursday. Bill Danchi and Rafael Millan-Gabet joined the observing team Thursday as Vanessa Bailey and Mickael headed down the mountain. The forecast for the weekend called for continued snow, with maybe a pause in the action Friday night.

Worried that we would be caught on the mountain due to the snow accumulation, we headed back to Tucson on Friday, with the option to carry out remote observing from Tucson. Surprisingly, it cleared down in the valley around sunset. Geno, (the telescope operator) kept the roof heaters going and cleared the snow off. Around 9 pm it started clearing on the mountain top, and we gathered in Tucson to begin the night.

The first step was to debug the stability of phasecam. The system appeared to be losing lock every time we tried to adjust which "fringe" the system locked on. It appeared to be due to some interaction between the tip feedback and the fringe hopping routine. We also found out that an attempt to limit the tip-tilt errors added in December seemed to be making the instability worse. We took additional data and refined gain parameters to have a reasonably stable phase loop. It would still break every other nod or so (every ~five minutes) but was usable. The data gathered should allow us to develop improved filtering of the phase-tip-tilt errors.

Surprisingly, as we completed this, the sky had cleared enough that we could gather decent quality 10 micron images. It was high humidity but clear. We set up on beta Leo and a calibrator and went to work. We gathered one SCI-CAL-SCI sequence before the rising humidity forced us to close around 5 am. The nulling sequences were taken at both 30 and 60 ms DIT (detector integration time). This will be compared to November's use of 15 ms for sensitivity and systematic errors to settle on an optimum DIT for HOSTS nulling sequences.

The remote observing worked surprisingly well, and may become more routine, if we can solve some network congestion issues.

The group's feeling by the end of the night:

Can we make it to the end of the night?


Movie Review: The Blob

Poor conditions on Wednesday night forced us close with little hope of opening the next night. So, at the end of the night we decided it was time for a movie. We whittled down the choice to "The Blob" or "The Red Planet" from the LBT's large movie collection. Vanessa, in her role as senior grad student, chose The Blob (1958), and we settled in for a viewing.

Girl and Boy are on a date when an asteroid hits. They investigate, but not before the lone old man gets there. Some gooey substance jumps onto his hand. The Girl and Boy take him to a doctor. Blob consumes the old man, then a very slow moving nurse (important lesson: don't run toward the blob), the doctor and so on. Don't bother shooting it or trying to kill it with acid. It consumes a good fraction of the town before they realize you should just freeze it.

This was Steve McQueen's first role. He's not a very convincing teenager, but, to be honest, the script doesn't give him much to do other than look concerned or try to convince others he's seen a hug red blob.

What is The Blob? Why was it popular? What does it represent? All good questions that pretty much went unanswered as we finished this slow moving movie. It ended (or did it?) by the army dropping the blob in the arctic. I won't hold my breath for The Blob 2.

Moral of the Review: don't let Vanessa choose the movies (again).


LBTI January Run: Nights 4-6

Reasonably good conditions for our last two nights. However, tonight it looks like our luck ran out.

On January 5, we had a second LEECH night with good, clear conditions. Data looked to be of good quality. The image quality on the right side may not be as good as the left, for reasons we have not figured out.

On January 6, a set of LBTB (Germany ) programs were scheduled, including young stars and Kepler followup. Mostly clear and good seeing throughout the night.

Tonight (Wednesday, January 7) we opened and tried to get set up on similar science for LBTB. Clouds (1 magnitude of extinction) and poor seeing (1.5-2") impacted data quality. By 8:30 pm we had to close due to increasing cloud cover.

The forecast for tonight and the remaining two nights is poor. Rain is forecast to start later tonight and then snow pretty continuously between now and the weekend. This impacts the HOSTS program most acutely. It was due to be executed starting the second half of tonight and the next two nights.


Phil watching the SpaceX rocket on the pad, before the launch was aborted due to "actuator drift."

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LBTI January Run: Nights 1-3

The LBTI team, including Andy Skemer, Vanessa Bailey, Amali Vaz, and Eckhart Spalding, welcomed the New Year by trying to make it up to Mt. Graham on January 2 (night 1), in snowy conditions. Andy made it, the rest were stranded in Safford for the night. The telescope was closed for the night due to snowfall that afternoon.

By January 3 (night 2) the snow had melted and the crew was able to open. An offloading error on the right side kept the team from using the right telescope for the beginning of observing (Follette program). During the night the offloading was fixed, just in time to carry out Fizeau observations of Io (Director's time). Some noncommon path aberration engineering rounded out the night, which had good seeing and was clear.

For January 4, we have had good seeing, but some light clouds rolling through. It is the LEECH program. Phil Hinz and Mickael Bonnefoy joined the existing team.


LBTI December Run: Nights 4-8

The remainder of the December time has been clobbered by two storms moving through the state. The first one passed through Saturday. By Sunday evening we could open. We phased the interferometer, but had trouble locking the system for use with the non redundant masking program (NRM) scheduled that night. The NRM program used single aperture observing. We used the final portion of Sunday night to test the robustness of the phasing system. This work continued for the first part of Monday night. Most of this time was intermittently cloudy, preventing any acquisition of nulling sequences.

Run Highlights:

  • Closed Loop Phasing with the FPC cold was demonstrated, and appeared to work well.
  • We determined the likely cause of the "fragility" of the phase loop is the tilt capture range.
  • Integration of phase and group delay tracking was improved.
  • Script testing and detector characterization was worked on while closed.
  • Realignment of the left side WFS was carried out to improve its robustness.
  • Testing of the replaced "UBC" computer was successful. This computer was showing problems in November.

Nightly Tally:

  • Saturday: Closed
  • Sunday: Open, carried out NRM. Phasecam engineering for last four hours of night.
  • Monday: Cloudy conditions. Opened 5-midnight for further Phasecam engineering.
  • Tuesday: Closed
  • Wednesday (tonight): Lost due to snow storm.

Technical Issues:

  • The NOMIC camera computer appeared to have a disk failure Tuesday night.
  • The SPC translation stage is continuing to show lack of responsiveness. A fix is planned using a new motor controller.
  • The NOMIC noise performance vs. flux shows strange behavior that needs to be understood.


LBTI December Run: Nights 1-3

The LBTI crew is back on the mountain for a December block of time (the nights of December 10-17). This time the core observing team is Vanessa Bailey, Denis Defrere, Phil Hinz, and Amali Vaz. As we began the run, it was clear that a winter storm would interrupt the middle of it.

The first and second night were allocated for the LEECH survey. The first night was mostly clear and average seeing. Both AO systems worked routinely for the night. The second night was mostly clear in the first half. During the second part of the night, clouds rolled in and we were unable to connive the program. We could still view bright stars through the clouds. We used the remainder of the night to set up the interferometry and phase sensing. While we acquired fringes, no phase correction was attempted due to poor seeing.

We are now on night 3 and the clouds prior to the storm have arrived. We are in fog and very unlikely to open at all tonight. Tonight was allocated to take some nulling commissioning tests. This will now have to wait until our next allocated block on Monday evening. Feel pity for two programs, Kepler K2 supporting observations by Ian Crossfield, and non redundant mask observations by Stephanie Sallum on Friday through Sunday. They are likely to lose most of their allocated time due to the storm.

Weather Forecast


LBTI November Run: Night 7

Another good night. The seeing was more variable. The wind picked up near the end. However, we were able to continue nulling commissioning. We spent the beginning of the night refining our algorithm for setting the stepping. This mainly resulted in taking a bunch of data which will need to be analyzed to complete this task. We then took another complete nulling sequence. A preliminary look at this data was very encouraging. The variability within a pointing looked much less than this spring. It is clear we are now dominated by systematics in our setup. We also took short exposures to allow testing of the NSC pipeline.

The tests later in the night were affected by wind and variable seeing. So, we used this to test the limits of our phasing algorithm. Results seemed to show that we could stay closed and remove a vibration signal which was approximately 10 microns peak to peak (this sounded almost too good to be true, so consider this number TBC). In any case, it proved we are able to acquire reasonable data, even int he presence of vibrations similar to typical to mediocre conditions seen at the LBT.


LBTI November Run: Nights 5 and 6

It was a roller coaster time the last two nights, mostly related to the nulling commissioning.

Friday night was split between the LEECH and HOSTS program. The LEECH time had reasonably good seeing, and the clear sky clock predicted improvement over the night. We transitioned to nulling in the middle of the night. Alignment and phasing of the system was completed early on. However, when we went to reproduce the phase control results from October we were unable to do so. The system was "fringe hopping" every couple seconds or so, keeping us from acquiring any nulling data. To make matters worse, as the night went on the seeing degraded, so we had difficulty troubleshooting the issue. It was painful to go to bed without understanding the issue.

Saturday we resumed troubleshooting. The seeing was much improved. We quickly found out the system was occasionally pausing due to low SNR, and allowing the fringe hops. With a little bit of tuning we were back to the October performance. Better yet, last night we were finally able to integrate the coarse and fine phase loop. This allows accurate correction, and a large capture range. The full system was tested out and verified. To benchmark where we were, we took two nearly complete nulling sequences (CAL-SCI-CAL) at the end of the night. These will be ideal for learning the current null repeatability, and understanding how to improve our observing sequence for better performance. So, tonight, we're going to bed much happier.


LBTI November Run: Nights 3 and 4

Wednesday was slated for LEECH observations. We opened and had mediocre seeing and winds, but were able to observe. However, by the middle of the night, the seeing and windspeed kept us mostly from getting useful science data. We closed by 2 am.

An offset problem was uncovered in the right side AO system. Doug tracked it down to a missing gain file, used when pausing and resuming the loop. Once this was restored the system worked as expected.

Thursday night was the second night of the LEECH block. We were closed until 1:15 am, when the wind finally dropped to below limits to open. Seeing gradually improved throughout the night (2 arcsec to start down to 1 by the end) , and we were able to obtain useful data. The left side AO system was RIP'ing more than usual, causing inefficiencies in observing. The suspicion was that we had a bad actuator. Images of Io were acquired near the end of the night.


LBTI November Run: Nights 1 and 2

Local Observing Team: Jarron Leisenring, Mike Skrutskie, Denis Defrere, Amali Vaz
Remote Observing: Vanessa Bailey, Phil Hinz, John Hill

Monday evening was our first night back on sky with LBTI. We carried out an LMIRcam program which was partially direct imaging and partially interferometry.

Both AO systems worked routinely for the evening. We were able to phase the system and carry out lucky fringing on a couple different targets. Seeing was ~1.4 arcsec.

Tonight (Tuesday night) various issues cropped up all night to prevent much new data from being acquired. At the beginning, thick clouds prevented us from getting on sky. When those disappeared the humidity spiked. It dropped around 11 pm and we opened for awhile to try some nulling. However seeing was horrible (1.5-5(!) arcsec). We measured the system emissivity (29%) and reset all the various set points to be ready for nulling. It was never good enough to try closing the phase loop. By 2:30 we were again forced to close due to high humidity.

Reasonably high winds (10-12 m/s) were causing the structure to vibrate more than we saw during the calm October nights. We noticed that the left M3 structure in particular appears to have a larger amplitude vibration response than either of the secondary structures when facing into the wind. This surprised us, as it is less exposed.

Seeing measurements during Night 2