On Monday we moved one of the VLTI auxiliary telescopes, number 4 ("AT#4"), from the observing platform atop Cerro Paranal down to the base camp, where a large assembly hall is located. The hall is useful for implementing modifications to the telescopes in an enclosed environment.
The ATs are designed to be self-mobile atop the platform, but need a special truck to get down to the base camp. As such, we had to drive AT#4 from its current location to a spot where we could lift it onto a truck and take it off the summit.
Needless to say, it is an impressive thing to see a 30-ton telescope lumbering down the rails. There are spots on the platforms where the rails make a 90 degree turn, which is no problem - the wheel trucks on the telescope base can be rotated to switch onto the intersecting rails.
We did the switch once to go from the "G" set of telescope stations, and once again the "J" set of stations were reached.
At the "J" line of telescopes stations, AT#4 was then driven to a spot where it could be lifted up and a truck trailer backed beneath it.
How do you lift a 30-ton telescope? Very carefully!
Once the telescope was on the truck trailer, it was driven down to the base camp.
Arriving outside the assembly hall, the telescope was lowered (once again - very carefully!) onto a set of rails identical to the ones at the summit, and then driven into the hall under its own steam once again.
All in all, the operation took about 8 hours, and went very smoothly. The team handling the activity were all very professional - industrious, careful, with a great deal of attention to detail.
I have to say, the whole day was extremely impressive to me - after working a number of years on designs for the Keck Interferometer that involved moving apertures, and battling deeply entrenched attitudes about optical telescopes not being able to be moved, it was very gratifying to me personally to see exactly that sort of thing in action. True, the transport to the base camp was extremely manpower intensive, but the station-to-station relocation was rather perfunctory.