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Lifting of the AWS
The image shows lifting operations of Modesta station at the Priestley Glacier, for clearing it from about a meter of snow.
This operation is generally carried out every two or three years depending on the snow accumulation characteristic of the site.
A few cubic meters of snow must be removed digging out with shovels. Under the snow, a case containing batteries is located beside the trellis base and it must also be lifted and repositioned; then power cables are disconnected and recovered, taking care to avoid damaging them with shovels. Finally, the lifting of the heavy structure can start.
Firstly, sensors should be removed to avoid damaging. Next, an operator climb up the trellis while the others stand at the stays and the helicopter takes off to hook the trellis.
This operation is tricky and dangerous because the operator is very close to the helicopter!
Hooked the trellis the operator at the top moves away, the others drop the stays while the helicopter flies maintaining a constant position over the ground (hovering) and keeping tight the line.
This is a very complex operation, stays must be maintained until the trellis is completed undocked, then released simultaneously to avoid trellis twisting
that could be dangerous for staff at the ground and for the helicopter.
Moreover, the pilot is unable to see what happens under the helicopter and he constantly communicates with a second helicopter at the ground which gives precise indications of the operation
Finally, the helicopter moves away the trellis and the snow surface is prepared for the new installation.
The helicopter goes back carefully unloading the trellis on the ground, three operators properly position it,
grab and fix the stays. Lastly, the pilot releases the line and safely lands at distance.
Instrumentation is mounted again and the mission accomplished!