Site Study

Research on meteorological condition in the atmosphere with satellite data

Meteorological conditions, including cloud coverage, have been studied based on data provided by a weather-monitoring satellite (1993 - 1999). Around Chajnantor, the rate of photometric nights is 70%, and precipitable water vapor is extremely low, which means that the site is suitable for infrared observations.

Research on topographical features by field works

Carried out in 8 field expeditions until 2004

▲ Reached the summit of Chajnantor by foot on November 2002

Research on meteorological condition near the ground with a weather monitor

The direction and speed of wind, and temperature, humidity, and pressure of the air are always being monitored. The desired good results were obtained in the flat area around Chajnantor. Since April 2006, weather observations have been continued at the summit of Chajnantor.

Weather monitor observing at the summit of Chajnantor

Research on seeing condition with a seeing monitor

Atmospheric turbulence affects astronomical observations because it causes vibration and expansion of stellar images. A true point source, like most stars, will be spread out by the turbulence into a small angle, the so-called seeing size; this has been measured and its effect has been evaluated. Very sharp stellar images with a seeing size of about 0.5 arcsec have been obtained around Chajnantor.

Picture of the seeing monitor. It uses an improved commercial telescope.

Research on meteorological condition in the atmosphere with an infrared cloud monitor

The cloud coverage throughout the entire sky is always monitored by measuring thermal radiation from any clouds. It has been confirmed that good weather conditions are very often present around Chajnantor. Meteorological observations have been carried out at the summit of Chajnantor since April 2006.