MASS is an instrument to measure the vertical distribution of turbulence in terrestrial atmosphere by analysing the scintillation (twinkling) of bright stars.

When stellar light passes through a turbulent layer and propagates down, its intensity fluctuates. Spatial scale of these variations depends on the distance to the layer. This dependence is used to separate the contributions from different layers by means of four concentric-ring apertures that work as a matched spatial filter. Turbulence profile is derived from the statistical processing of the series of photon counts with 1 ms sampling.

How it works?
The instrument
The team
Papers and documents
MASS database (Tololo, Pachon)
Data plotting and control scripts [.tar.gz]
News 2009  

April Results of the TMT campaign of testing 6 sites are publicly available.
Shoeck et al. "Thirty Meter Telescope Site Testing I: Overview" ArXiv:0904.1183 (contains the full list of future papers)
Els et al. "Thirty Meter Telescope Site Testing VI: Turbulence Profiles" ArXiv:0904.1865

April Update on the MASS-DIMM results at Kislovodsk. See the English version of the presentation by Kornilov et al.

News 2008  

December Free atmosphere at Mt. Maidanak (Uzbekistan) have been studied with MASS over 3 years (2005-2007). The median seeing in the free atmosphere (above 1km) is 0.37", the median isoplanatic angle is 2.47", and the median AO time constant is 7ms - almost two times larger than in most observatories! The paper by V.Kornilov, S.Ilyasov, O.Voziakova et al. with these results is accepted by "Astronomy Letters", see it on astro-ph ArXiv:0905.0741

November Seven MASS-DIMM instruments have been fabricated and tested at CTIO, to be delivered to various observatories. This brings the total number of MASS-DIMM instruments built to 31. There are no plans to continue this production!

June Several papers based on the MASS-DIMM results are presented at the SPIE Conference "Astronomical Instrumentation" in Marseille, e.g. by Els et al. and by Thomas-Osip et al.

February First results from the MASS-DIMM seeing monitor operated robotically at Kislovodsk (Northern Caucasus) are available in a report by V.Kornilov and his site-testing team [PDF, 2.8M ] . Over 3 months in 2007, the median seeing was 0.94", with 0.44" median seeing above 1km. The picture shows the RCX-400 telescope with MASS-DIMM, reinforced finder with a TV camera for pointing, and custom anti-fog protection (click to enlarge). See also MASS page at Sternberg
News 2007  

July Papers on the MASS-DIMM instrument and accuracy of the MASS and DIMM methods are submited to MNRAS:
"Combined MASS-DIMM instrument fro atmospheric turbulence studies" [PDF, 436K ]
"Accurate seeing measurements with MASS and DIMM" [PDF, 436K ]

June Two MASS-DIMM units are in regular operation at Palomar. More on the Palomar MASS-DIMM web page
See also recent paper
News 2006  

June Recent papers using MASS data on astro-ph:
astro-ph/0606332 Athey A. et al. "GMT Ground-Layer Experiment"
astro-ph/0604538 Kenyon S. et al. "Scintillation at Dome C, Antarctica"
astro-ph/0603170 Britton M. "Anisoplanatic PSF in Adaptive Optics"

June 10 Suzanne Kenyon compared the MASS data from Cerro Tololo (2002-2006, 64504 profiles) with the wind speed data extracted from NCEP/NCAR. Correlation between seeing in the free-atmosphere and wind speed. See also the new document on the calibration of MASS time constant [PDF, 150K].

March 24 Tests of the new MASS software, Turbina, are under way. The new version will permit a partial correction for strong scintillation. Example of re-processing

March 3-15 Four new MASS-DIMM instruments are produced for ESO, to support the European ELT site-testing program. Another set of 5 units is produced by CTIO for some other observatories. More on acceptance and testing of new MASS-DIMMs...

News 2005  

November A MASS is being used at the Mt. Maidanak observatory in the Republic of Uzbekistan to monitor the turbulence profile. More about this campaign...

September A MASS-DIMM starts regular operation at Palomar, in support of classical observations and adaptive optics. Provisionally, one of the TMT site-testing units is used while a fabrication of the permanent instrument is proceeding. See MASS-DIMM plots at Palomar

May Data of MASS-DIMM and SODAR from Cerro Pachon are used in a statistical model of the turbulence profile at this site. Paper submitted to MNRAS, see PDF, 365K [Accepted October 2005].
News 2004  

December Plastic replicas of MASS-DIMM segmentators are produced and installed in three new instruments. See the Report on replication process PDF, 312K .

December A campaign of comparison of SLODAR with MASS-DIMM and SODAR has been conducted at Cerro Tololo from Nov. 21 to Dec. 3, 2004 by R.Wilson, T.Batterley, M.Sarazin and A.Tokovinin. During this period, experiments on planet scintillations were performed: see the report .

October The problem of the MASS "over-shoots" is understood. See the Short explanation , Case-study report , Report on experiments , Simulations

September 16 A paper on the MASS results from Dome C is published in Nature. More information and links at the Mike Ashley's site

September 13 A stand-alone MASS module fed by a 8-cm refractor has been tested at La Silla as a "piggy-back" to the standard ESO site monitor, DIMM. It is now translated to the Paranal for providing real-time support of adaptive-optics work. MASS-LITE on top of the ESO DIMM See also the ESO MASS web site

May Inter-comparison of three different MASS instruments. Comparison plots

March March 24: MASS starts working at Dome C! First profiles from Antarctica.

Article on MASS-DIMM in NOAO/NSO Newsletter [PDF]

January Report on MASS-SCIDAR comparison from the Mauna Kea-2002 mission: PDF, 1.68M

News 2003  

December MASS-DIMM is installed at a site in the Northern Chile. The fabrication of nine MASS-DIMMs is finished!

October First light of MASS-DIMM at Tololo on October 3/4 2003: Cn2 profiles and free-atmosphere seeing

September MASS database is on-line! Look at

September Integration of several MASS-DIMM instruments starts in La Serena. See the presentation of MASS-DIMM electronics by Victor Kornilov on Sept. 24, 2003: Power-point, 254K Pictures of assembled MASS-DIMM , electronics and detector module, plate and segmentator. Pictures of MASS-DIMM with Meade telescope: picture1 , picture2 . More pictures...

May MASS-DIMM project

February 9 ESO MASS is installed at Cerro Paranal, to work in campaign mode in support of AO operations at VLT. More details here. The graphical report on the March 2003 campaign is prepared by M. Sarazin.

January 8 MASS starts site monitoring at Cerro Pachon, a campaign organized by CTIO and SOAR. See the REPORT on this campaign.

News 2002  

October 17-23: MASS is installed at the 24-inch telescope at Mauna Kea (Hawaii) and takes part in a site evaluation campaign together with SCIDAR and DIMMs. More on this campaign...

September: The results of 3 months of continuous monitoring of turbulence profile and seeing at Cerro Tololo are avilable here.

August 22-28: SPIE Conference "Astronomical Telescopes and Instrumentation". Get the paper 4839-102 and the poster on MASS instrument.

July 2002 : Campaign of comparison between MASS and SCIDAR starts at La Silla (ESO) on July 7. See some results here.

June 2002: Turbulence monitoring at Cerro Tololo continues. A 4-night period of exceptionally calm atmosphere was detected on June 19-22, 2002

May 14-22: Commissioning of ESO MASS at Cerro Tololo (M. Sarazin, V. Kornilov, A. Tokovinin, M. Schoeck). Results of comparison on May 20-22, 2002

April-May: MASS starts regular operation at Cerro Tololo

March 19-27: MASS Commissioning run at Cerro Tololo, Chile. See some results here.

January: MASS Commissioning in Moscow. M. Sarazin and N. Hubin (ESO) and A. Tokovinin (CTIO) worked with Kornilov's team.

Picture 1: N. Hubin and M. Sarazin discuss MASS alignment with Victor.

Picture 2: Victor explains the software.

Last modified: March 25, 2008 A. Tokovinin (