The VLTI Auxiliary Telescopes
The four 1.8-m Auxiliary Telescopes(ATs) were designed for interferometry and therefore essentially dedicated to the VLTI. The ATs were manufactured by AMOS (Belgium). They allow a more efficient use of the VLTI each night since most of the time the large telescopes are used for other purposes.
They are mounted on tracks and can be relocated at 30 different observing positions on the observatory platform enabling thus to change the entire configuration of telescopes according to the observational requirements. From these positions, the light beams are fed into the same common focal point via a complex system of reflecting mirrors mounted in an underground system of tunnels.
The Auxiliary Telescopes are placed in ultra-compact enclosures, complete with all necessary electronics, an air conditioning system and cooling liquid for thermal control, compressed air for enclosure seals, a hydraulic plant for opening the dome shells, etc. Each AT is also fitted with a transporter that lifts the telescope and relocates it from one station to another. It moves around with its own housing on the top of Paranal, almost like a snail.
Since the beginning of 2007all four Auxiliary telescopes are available and fully operational.