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 utilizes 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 atmospheric turbulence induced distortions, thus enhancing the imaging and spectroscopic capabilities for LUCI over a wide field of view. ARGOS is capable to reduce the seeing by a factor of 2-3 over a 4 arcmin field of view.

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 (Jan. 2019)

Our ARGOS paper now finally made it into the Astronomy & Astrophysics Volume 621 (January 2019), and the ARGOS laser image onto 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 during these days and nights. During all the run we had both sides operating binocular. The ARGOS aquisition for both sides works flawlessly, usually within short time.
In operating the telescope with both sides in parallel we have tested several observing modes: 
-taking images of the same object in parallel on both sides workes without problem. Either exactely the same program is executed on both sides, which is easy, or different filters on both sides with aproximately 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~10000 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'' spatial and R~8000 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 make it finally a reliable observation machine.

The team has spent 10 nights and several preparation days before at LBT, trying to advance our system. This run we have being mainly focussed onto the combination of ARGOS plus LUCI, exercising observation tests on a variety of targets. As within the last weeks we have accumulated a lot of data and the evaluation of both, astronomical, technical and as well the time bookkeeping. 
Going through a mixed program with object proposals from the instrument partners we looked at several nearby galaxies in imaging- which is getting actually close to easy- achieving good resolution. We executed sucessfully longslit observations- both on nearby objects, but as well on a lensed line emitter. We could execute some hour long integrations using curved slits on gravitationally lensed arcs, detecting clearly Halpha in all cases.
Image: M51,  ARGOS&LUCI imaging
We have focussed on using one side of the telescope, SX with LUCI1, to bring it further towards completion. Having learned what all is needed to do an aquisition of Argos with LUCI, we could exercise this time quite often the process from telescope pointing, collimation, AO preset, laser launch, laser aquisition, guide star aquisition, loop closure and observation. The whole preset scheme has now well solidified, and we fully could run observations scripted with LUCI. Within low winds and good seeing the systems turns out to run stable. To check our performance on sky we have pointed several imaging targets, from star clusters, to nearby galaxies, to gravitational lenses. With the team now heading back, some really exciting observations in the luggage, we are looking forward for the next run in May.
Currently we are in the last night of our first wavefront sensor comissioning run on SX side. Sky is clear, aircraft spotters are freezing at their stations (2degC) and all systems are running smoothly.
Beside the second wavefront sensor, we brought some more stuff with us this time: 
The newly installed launch system thermal managment 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 biploar, fully remote controlled THE POCKELS CELL driver and upgraded the pockels cells itself.
Including much more little things and tasks, the ARGOS laser guide star facility is now completly installed to the telescope, and we are looking forward to adjust all the subsystems and make them work together like a single machine. Will keep us busy for quite some time.
The second wavefront sensor was shipped to the telescope, and together with it's already installed brother from DX side both sensors were brought to the clean room, updated, aligned and tested. Now both sensors are ready for their installation on the instrument platform.
During our commissioning run in April/May 2015, we used the ARGOS laser guide star facility to take images with LUCI 2. There is still lots of things to do, and we are looking forward to do it.
Let us introduce miss NGC6384!
We have been able to lock the AO on the three laser guide stars simultaneously and achieved very soon an impressive good correction on the Luci2 images. With good sky conditions nicely supporting, we have achieved 0.3 to 0.4 arcsecond images in J, H and K, corrected out of 0.7...1 arcsecond seeing, with the best image reaching down to 0.22 arcseconds in Ks with a factor 4 in PSF improvement. more
The wavefront sensor was reinstalled, after it was removed during the summer shotdown.
After the first day of calibration we were able to measure a 150modes interaction matrix simultaneously on the 3 LGSs and close the GLAO loop.
Now the system is prepared for closed loop tests on-sky.
In this comissioning run we started to close the loop between DX wavefront sensor and adaptive secondary. This is a very complex procedure, which involves a bundle of the telescope's AO subsystems, the whole Argos system and of course this requires clear sky. All these difficulties could not stop us and last night we could correct the first 20 modes. Now we pray 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 fullfill the updated requirements. This new developed system simplifies operation a lot and makes the laser officier's life much easier.

On sky: First light on DX wavefront sensor (Mar. 2014)

We could see the laser guide stars on the wavefront sensor during the nocturnal on-sky tests! We (strongly simplified) focus 3 laser beams in 12km height and using a 8.4m telescope we project them trough a 2.8mm hole on a 13x13mm CCD. The picture shows the Shack-Hartmann patterns of 3 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 visible.

Wavefront sensor DX installation (Mar. 2014, Snowman)

During the last week we smoothly installed the WFS/LGSW DX and its infrastructure. System is up and we are now preparing the on-sky tests.
Finally we are finishing a great commissioning run of Argos. With nearly three weeks of day 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- probing that no detectable background radiation is seen from the lasers.
See the gallery for more amazing pictures! more

More on-sky testing (Nov. 2013)

First laser test on sky (Nov. 2013)

We just tested our lasers on sky for the very first time!
Go to Editor View