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Description
Recent studies have shown that stratigraphically disturbed meteoric ice bedded at Vostok Station between 3318 and 3538 m dates back to 1.2 Ma BP, and possibly beyond (Lipenkov et al., 2019). As part of the VOICE (Vostok Oldest Ice Challenge) initiative, in the 2018/19 austral season, a new deviation from parent hole 5G-1 was made at depths of 3266-3291 m with the aim of obtaining a replicate core of the old ice. The deviation operation was performed using the standard KEMS-132 electromechanical drill routinely used for deep ice coring at Vostok, without significant changes in its initial design. Here we describe the method and operating procedures for replicate coring at a targeted depth in an existing slant hole, which imply using a cable-suspended electromechanical drill. A design of the drill cutter head suited to the deviation operation is presented. The performance characteristics and the experience of drilling two branch holes, 5G-2 and 5G-5, at Vostok are described and discussed.
