Advanced Rayleigh-Guided Ground Layer Adaptive-Optics System 

Advanced Rayleigh-Guided Ground Layer Adaptive-Optics System 

The ARGOS project equips the LBT, the Large Binocular Telescope, with an up-to-date laser guide star and wavefront sensing facility. ARGOS operates multiple pulsed lasers to generate artificial guide stars. A total of six laser guide stars are used to correct the ground layer turbulence above each of the LBT mirrors. The primary goal of the facility is to correct the distortions induced by atmospheric turbulence, thus enhancing the imaging and spectroscopic capabilities for LUCI over a wide field of view. ARGOS is capable of reducing the seeing by a factor of two to three over a field of view of 4 arcminutes.

The system consists of:

  • Laser systems, each of them containing three powerful pulsed green lasers
  • Beam expanders to enlarge the lasers to a 40cm diameter and project them to sky
  • Wavefront sensors to detect the backscattered light from the beacons
  • The adaptive optics control of LBT's deformable secondary mirrors


ARGOS Paper in A&A (January 2019)

Our ARGOS paper now finally made it into the Astronomy & Astrophysics Volume 621 (January 2019), and the ARGOS laser image is on the title page:

All the best, and a happy New Year to all of you!

Run March 2017: Binocular Laser Guide Star Adaptive Optics

The weather and the technology behaved well for these days and nights. During the wohle run, we had both sides operating binocular. The ARGOS acquisition for both sides works flawlessly, usually within short time.
While operating the telescope with both sides in parallel, we tested several observing modes: 
  • Taking images of the same object in parallel on both sides works without problems. Either exactly the same program is executed on both sides, which is easy, or different filters on both sides with approximately matched observation times between offsets can be taken. 
  • LS spectroscopy has been tested with half the K-band on one side and the other half on the other side, gaining R ~ 10,000 resolution over full K-band.
  • We observed identical MOS masks on both LUCIs with either the same wavelength setting to increase the S/N or as well K-band on one side and H-band on the other to detect Ha and OIII simultaneously at z ~ 2, with ~0.3 arcseconds spatial and R ~ 8,000 spectral resolution.

First Successful Binocular ARGOS-Corrected Observation

At the end of the December commissioning run we can proudly state that the binocular operation mode with Argos and both Luci's is in good shape. We tried out modes of simultaneous offset pointings of both eyes and as well a first test of commanding one side of the telescope independent offsets while the other side happily integrates on target.
Despite being really proud of quite some achievements, we still will be working hard on the system, needing severe software work, but as well hardware upgrades, to finally make it a reliable observation machine.

Commissioning May 2016

The team has spent ten nights and several preparation days before at LBT, trying to advance the system. For this run, we have mainly focused on the combination of ARGOS plus LUCI, carrying out observation tests on a variety of targets. Within the last weeks, we have accumulated a lot of data and evaluated both astronomical and technical information as well as doing the time recording. 
Going through a mixed program with object proposals from the instrument partners, we looked at several nearby galaxies in imaging – which is becoming almost easy – and achieved a good resolution. We successfully executed long-slit observations, both on nearby objects and a lensed line emitter. We were able to execute some hour-long integrations by using curved slits on gravitationally lensed arcs, and clearly detected Hα in all cases.
Image: M51,  ARGOS&LUCI imaging

Commissioning (December 2015/March 2016)

We have focused on using one side of the telescope, SX with LUCI1, to bring it further toward completion. Having learned what is needed to do an acquisition of ARGOS with LUCI, we were able to carry out the process from telescope pointing, collimation, AO preset, laser launch, laser acquisition, guide star aquisition, loop closure, and observation quite frequently this time. The whole preset scheme has now solidified, and we could run observations scripted with LUCI. Within low winds and good seeing, the systems turn out to run in a stable way. To check our performance on sky, we pointed several imaging targets, from star clusters to nearby galaxies and gravitational lenses. While heading back and recalling our exciting observations, we are looking forward to the next run in May.

Wavefront Sensor SX Comissioning (October 2015)

Currently, we are in the last night of our first wavefront sensor comissioning run on SX side. The sky is clear, aircraft spotters are freezing at their stations (2degC), and all systems are running smoothly.
In addition to the second wavefront sensor, we brought some more equipment with us this time:
the newly installed launch system thermal management keeps the mirrors in shape while the new Laser Alignment Telescope (LAT) controls the star constellation's position on sky. During our last run in September, we already brought the whole new bipolar, fully remote controlled Pockels cell driver and upgraded the Pockels cells.
The ARGOS laser guide star facility has now been completely installed into the telescope, and we are looking forward to adjusting all the subsystems and making them work together like a single machine. This will keep us busy for quite some time!

Wavefront Sensor Refurbishment (August 2015)

The second wavefront sensor was shipped to the telescope, and together with its already installed brother from DX, both sensors were brought to the clean room, updated, aligned, and tested. Now they are ready for installation on the instrument platform.

Laser-AO-corrected LUCI images (May 2015)

During our commissioning run in April/May 2015, we used the ARGOS laser guide star facility to take pictures with LUCI2. There are still many things to be done, and we are looking forward to it.
Let us introduce NGC6384!

GLAO Closed Loop (December 2014, Mouse)

We have been able to lock the AO on the three laser guide stars simultaneously and quickly achieved an impressive correction on the LUCI2 images. With the help of good sky conditions, we took 0.3 to 0.4 arcsecond images in J, H, and K, corrected from 0.7 to 1 arcsecond seeing, with the best image reaching down to 0.22 arcseconds in Ks with a factor of four in PSF improvement.
See the gallery for some pictures:

Loop Closed on ARGOS LGSW (November 2014, Mountain Lion)

The wavefront sensor was reinstalled after its removal during the summer shutdown.
After the first day of calibration, we were able to measure a 150-mode interaction matrix simultaneously on the three LGSs and close the GLAO loop.
Now the system is prepared for closed-loop tests on sky.

Wavefront Sensor Commissioning (May 2014, Western Tanager)

In this commissioning run, we started to close the loop between DX wavefront sensor and adaptive secondary mirror. This is a very complex procedure, which involves a bundle of the telescope's AO subsystems and the whole Argos system – and of course, this requires a clear sky. All these difficulties could not stop us, and last night we were able to correct the first 20 modes. Now we hope for clear skies for the last night of this campaign.
Additionally, the laser interlock system was replaced by a new one, as the old system could hardly fulfill the updated requirements. This new system simplifies operation a lot and makes the laser officer's life much easier.

On Sky: First Light on DX Wavefront Sensor (March 2014)

We could see the laser guide stars on the wavefront sensor during the nocturnal on-sky tests! We (strongly simplified) focus three laser beams in 12 km height and used a 8.4 m telescope to project them trough a 2.8 mm hole on a 13 x 13 mm CCD. The picture shows the Shack-Hartmann patterns of three laser guide stars on the detector CCD. The dark spot in the middle is the shadow of the secondary mirror, even its spider is vaguely discernible.

Wavefront Sensor DX Installation (March 2014, Snowman)

Last week, we smoothly installed the WFS/LGSW DX and its infrastructure. Now the system is up and we are preparing the on-sky tests.

Successful On-Sky Tests (October/November 2013, Bobcat)

At last, we are finishing a great commissioning run of ARGOS. With nearly three weeks of day work and four nights, we have finally seen our laser beams on sky. As last night's highlight, the LUCI team managed to bring both LUCI1 and LUCI2 quickly on sky, taking an image and a spectrum for us to make sure that no detectable background radiation is seen from the lasers.
See the gallery for some amazing pictures!

More On-Sky Testing (November 2013)

First Laser Test on Sky (November 2013)

We just tested our lasers on sky for the very first time!
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