The calibration is necessary to ensure that the approach aids are still functioning to the specified standards, but side effects include interruptions to other traffic [especially VFR flights like the aero club's flights!].
Anyway, the aircraft being used [pictured below] is a Vincent Aviation Jetstream J31, ZK-JSH, on behalf of the Airways Corporation of NZ.
Other aircraft from today include a Robinson R22 Beta, ZK-HHQ and registered to Heliflite of an Auckland address and a Piper PA18 Cub, ZK-BQY which is also registered to an Auckland address.
The last photo shows the new fence that has sprung up around the old aero club hanger which the the airport company [Wellington International Airport Ltd - WIAL] is preparing to demolish. A real shame...