Narrative:

To improve efficiency and reduce crowding in Erebus Hut, four occupation periods were planned this year, beginning on 24 November with Otway, Currie and Bell, overlapping next with Dibble and Paintin, then Kyle's U.S. party, and finally Ueki and Koyama until the end of December. The weather and the helo operational problems this year made this impossible.

After reaching the hut on 21 December, the whole party was involved in carrying 20 Gel-cell batteries (20 lbs. each) from the hut to the telemetry transmitter site. In the absence of the Alaskan telemetry experts (who spent their grant on equipment for IMESS instead of travel) the New Zealand party installed the new solar panel, serviced the transmitter, and installed a new pressure sensitive microphone (NS LX6002 G) and associated 1700 Hz preamp/VCO. The new microphone is a temporary inexpensive one necessitated by an edict from DPP (NSF) banning descents into the main crater, where the existing microphone was installed (but not calibrated) last season. It was hoped that the old microphone would still work, and could be calibrated by comparison with the new one, because the crater is free from wind and many eruption sounds have been recorded there. Unfortunately, the cable down the crater wall had broken. The new temporary microphone is at the old Carbonaire battery site on the ridge between the Main and Side Crater, and will be replaced by a high quality one (courtesy of NSF) next season.

The New Zealand party also repaired the magnetic induction loop, and reburied most of the exposed sections which were at risk from weather and volcanic activity.

page 30

Telemetry recordings began from the summit seismometer on 24 December - from the infrasonic microphone (calibrated by raising and lowering it 3m at 5 second intervals to create a 24 Pa signal) on 26 December, and from the induction loop (calibrated by moving a set piece of the loop inside Erebus Hut through the geomagnetic field) on 29 December.

On 28 and 29 December following the arrival by helo of a Yamaha motor toboggan an electromagnetic (E-M) survey over about a quarter of the summit plateau was made using a portable 50m square loop, 24V battery, and reversing switch as the transmitter, and the induction loop around the crater as the receiver. Signals via the loops and also via VHF radio were recorded on separate channels of a tape-seismograph recorder, and contain data on possible presence of electrically conductive magma under the summit plateau.

Twelve stations were occupied in an area extending to 2/3 of the plateau radius and 1/3 of its circumference. Limitations were the E-M transmitter power (400 W) and VHF radio shadows. Between 24 and 30 December, another tape-seismograph recorder was used to record a Willmore Mk2 geophone (To = 3s, horizontal component transverse to the crater direction) sited 220m from the hut towards the crater and from 26 December the spare pressure sensitive microphone at the winch site was also recorded. A log of audio-visually observed eruptions was kept, but as the speaker in the hut was not hooked up to the microphone the log is not as complete as in previous years.

Readings of tiltmeter installed by Otway's party continued until 1 January 1983, and a beacon light was operated for Pat Tinnelly (L & S) to sight onto from Cape Royds. The New Zealand party descended on 4 January 1983.

The U.S. party collected lava bombs, installed aerosol collectors, and took a still and movie record of the lava lake and work in progress. Some of the film was shot for Science Express (NZTV). The Japanese party made a video tape of the crater and lava lake, and also a gravity survey of the summit area. They descended from Erebus on 27 December.

On 8 January, the new infrasonic microphone stopped working in a manner which suggested that it was producing a full scale DC signal. A helo flight was immediately requested, and thanks to the support of Dr. Kaminuma at McMurdo, Dibble, Bell and the Science Express camera crew got 2 hours on the summit on 11 January. The fault was traced to the pressure sensor, and the spare microphone was installed and calibrated. The only known defect in the summit installation was then in the geophone preamp/VCO (2380 Hz) which was converting the smooth changes in vibration amplitude into step changes (i.e. digitising it). Following the arrival of spare units from Alaska, McIntosh and Harrall (Sci. Lab technician for IMESS) flew to the summit on 27 January and replaced the faulty preamp/VCO with one on Hz. They descended believing that the installation was free of defects, but on 8 February the new unit went off frequency and then the transmitter went dead. The VXE-6 helo operations had ceased, and as only one member of the Survival School (Phil Austin) was available, no attempt was made to cure the fault. As at 28 February, the other 4 telemetry seismographs on Erebus are functional.