ALMA can change the way it watches the sky, depending on whether the object being studied calls for high sensitivity to faint light, high resolution for seeing fine details, or some combination of both. To make high sensitivity maps of large structures (such as gigantic stellar nurseries), the telescopes need to be close to one another. To spot the pinpoints of once-hidden objects (such as planets going around other suns), the telescopes should be spread far apart. To switch between these set-ups, at least 50 of the 66 plus telescopes of ALMA can be moved for miles around the Chajnantor Plain observatory site in Chile.
Lifting and moving a 115-ton telescope requires a beast of a vehicle -- half crane and half tank. Scheuerle Fahrzeugfabrik of Germany built two of these "Transporters" for ALMA. Named "Lore" and "Otto," these monster trucks are incredible feats of engineering. A Transporter is 33 feet (10 m) wide, 66 feet (20 m) long, and 20 feet (6 m) high, and uses twenty-eight tires to drive its 130-ton mass up to 20 mph.
As a crane, the beastly Transporter shows its gentleness. An operator drives the Transporter like a giant forklift, using its unique U-shape to surround the telescope. Hooks on the ramped sides of the Transporter clamp on to lifting brackets welded to the sides of the telescope.
Once lifted up safely from its mounts, the telescope is unplugged from its power and control sockets and plugged into the Transporter. The Transporter's hooks then crawl up its sloped ramps, pulling the telescope up with them.
Loaded with a telescope, one of these giant trucks can attain speeds of up to 12 mph. With an engine rivaling that of two Formula One racecars, the Transporter can take up to seven hours to carry its burden carefully up from the telescope testing area to the observatory site. In part, this is because the engine loses half of its fuel-burning power as it climbs into the thinner air at the observatory, 16,000 feet (5,000 m) above sea level.
When he finally arrives at the telescope's concrete pad, the Transporter operator removes the dashboard and leaves the vehicle to remotely control it from a clearer view outside. The Transporter's wheels twist and turn the truck in tight circles, so that the operator can position the telescope within millimeters of its exact footing location. The operator commands the Transporter to gently lower the telescope almost all of the way to the pad. Then, the operators wrangle the final bolt-down and power-up.
Join Adrian Russell in the Transporter garage as he gets up close to one of these gentle giants.