Note that not all data taken with all instruments can be made available for automatic download through the database. This is due to technical reasons, either because the data files are too large (e.g. the all-sky camera images) or because they require complex post-processing procedures that depend on the intended use of the data (e.g. SODAR or IRMA data). Check out the Data Fields page to see which data are available for automatic download. If you are interested in any of the other data (including raw data such as DIMM image frames), please contact us and we will be happy to provide the respective files.
At each site, a sonic anemometer (CSAT-3 model by Campbell Scientific) was placed at the level of the MASS/DIMM telescope, 7 m above the ground. It measures a "sonic temperature" (proportional to temperature, but also dependent on humidity and other parameters) and wind speed and direction. The raw data for turbulence measurements were also taken and saved.
We also installed 30 m towers on Armazones (September 2006) and Tolonchar (March 2007). These were equipped with sonic anemometers (CSAT-3's at Armazones and Ultrasonic Anemometers Model 81000 by Young at Tolonchar) and air temperature sensors at the 11, 20 and 28 m (Armazones) and 11, 20, and 30 m (Tolonchar) levels.
A DIMM is predominantly used for measuring the atmospheric seeing. The measurement of other parameters such as the isoplanatic angle, the turbulence coherence time and atmospheric transparency can also be attempted with a DIMM. During TMT site testing, we had other instruments available which produce these latter parameters with higher reliability. The TMT DIMMs were therefore only used for seeing measurements
For detailed information on DIMMs in general and the TMT DIMMs in particular, see:
M. Sarazin & F. Roddier, "The ESO differential image motion monitor", Astr. & Astroph. 227 (1), pp. 294-300 (1990)
A. Tokovinin & V. Kornilov, "Accurate seeing measurements with MASS and DIMM", Mon. Not. Roy. Astr. Soc. 381 (3), pp. 1179-1189 (2007)
L. Wang et al., "High-accuracy differential image motion monitor measurements for the Thirty Meter Telescope site testing program", Appl. Opt. 46 (25), pp. 6460-6468 (2007)
W. Skidmore et al., "Thirty Meter Telescope Site Testing V: Seeing and Isoplanatic Angle", Publ. Astr. Soc. Pac. 121 (884), pp. 1151-1166 (2009)
A MASS produces six-layer measurements of the turbulence profile, excluding the first few hundreds of meters. The layers are centered around 0.5, 1, 2, 4, 8 and 16 km elevation. Integrating over the profiles gives the seeing (excluding the ground layer) and the isoplanatic angle. The ground layer turbulence strength can be calculated from the difference between the DIMM and MASS seeing. For TMT site selection, the MASS data were also used to obtain estimates of the turbulence coherence time and presence of cirrus clouds.
For detailed information on the MASS principle in general and the TMT MASS units in particular, see:
V. Kornilov et al., "Combined MASS-DIMM instruments for atmospheric turbulence studies", Mon. Not. Roy. Astr. Soc. 382, pp. 1268-1278 (2007)
S. Els et al., "Study on the precision of the multiaperture scintillation sensor turbulence profiler (MASS) employed in the site testing campaign for the Thirty Meter Telescope", Appl. Opt. 47 (14), pp. 2610-2618 (2008)
W. Skidmore et al., "Thirty Meter Telescope Site Testing V: Seeing and Isoplanatic Angle", Publ. Astr. Soc. Pac. 121 (884), pp. 1151-1166 (2009)
S. Els et al., "Thirty Meter Telescope Site Testing VI: Turbulence Profiles", Publ. Astr. Soc. Pac. 121 (879), pp. 527-543 (2009)
T. Travouillon et al., "Thirty Meter Telescope Site Testing VII: Turbulence Coherence Time", Publ. Astr. Soc. Pac. 121 (881), pp. 787-796 (2009)
For details about the TMT SODARs and their notoriously difficult calibrations, see:
T. Travouillon et al., "
T. Travouillon et al., "
A detailed description of the cameras is given in:
D. Walker et al., "Monitoring the night sky with the Cerro Tololo All-Sky camera for the TMT and LSST
projects", Proc. SPIE 6267, p. 62672O (2006)
For details on the IRMA instruments in general and the TMT units in particular see:
I. Chapman et al.,"Correlation of atmospheric opacity measurements by SCUBA and an infrared radiometer", Mon. Not. Roy. Astr. Soc., 354, pp. 621-628 (2004)
A. Otárola et al., "
Dust/Particle Sensor
Dust particle sensors were installed at the level of the MASS/DIMM telescope 7 m above the ground.
The dust sensors are commercial units from Met One Instruments, model GT-321. They measure the particle
count in five different channels, for particle sizes 0.3, 0.5, 1.0, 2.0 and 5.0 μm. Here, the given size
is a lower limit, each channel counts all particles with sizes equal to or larger than the respective
value.
All-Sky Camera (ASCA)
All-sky cameras (ASCAs) were deployed at all candidate sites. The TMT ASCAs are replicas
of the Tololo ASCA and were built by the Cerro Tololo Inter-American Observatory (CTIO).
During the TMT site testing phase, the ASCAs were used for cloud cover, usable time and light pollution analyses as well as for operational purposes (determining conditions at the sites).
Infrared Radiometer for Millimetre Astronomy (IRMA)
Three Infrared Radiometer for Millimetre Astronomy (IRMA) units were built for TMT by the IRMA Group of the Institute for Space Imaging Science (ISIS) at the University of Lethbridge. An IRMA measures the sky flux around 20 μm wavelength
and derives a precipitable water vapor (PWV) value from this flux by use of a suitable atmospheric
model.
The three units were deployed on Armazones, Tolonchar and Mauna Kea 13N for varying amounts of time.