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Victoria University Antarctic Research Expedition Science and Logistics Reports 1982-83: VUWAE 27

EREBUS STUDIES AND IMESS (K4) - R.R. Dibble

page 29

EREBUS STUDIES AND IMESS (K4) - R.R. Dibble

The IMESS team this year was as follows:
New Zealand: Dr. Ray Dibble, Victoria University of Wellington.
Mr. Ian Paintin, Victoria University of Wellington.
Mr. Peter Otway, NZ Geological Survey.
Mr. Steve Currie, NZ Geological Survey.
Mr. Lindsay Bell, Antarctic Division.
U.S.A.: Dr. Phil Kyle, New Mexico Institute of Mining and Technology.
Mr. Eric Bigelow, New Mexico Institute of Mining and Technology.
Miss Julie Palais, Institute of Polar Studies, Ohio State University.
Japan: Dr. Katsutada Kaminuma, National Institute of Polar Research.
Dr. Sadato Ueki, University of Sendai.
Mr. Etsurou Koyama, Asama Observatory, University of Tokyo.

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.

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Transport:

Transport to and from Antarctica was as follows:
Dr. R. Dibble 15.11.82 NZAF Herc 12.1.83 VXE-6 Herc
I. Paintin (Member of K5) 8.1.83 VXE-6 Herc
P. Otway 22.11.82 NZAF Herc 17.12.82 VXE-6 Starlifter
S. Currie 22.11.82 NZAF Herc 17.12.82 VXE-6 Starlifter
24 Nov Otway to Fang
29 Nov Fang - Hut

No problems were experienced going to Antarctica. Returning to New Zealand proved difficult because resupply flights to Pole and Siple Stations had been delayed, and were first priority. Pressure for seats can be gauged from Dibble's experience. Although already delayed 2 weeks and in spite of priority assigned by the DOIC for family weddings beginning 12 January and preparation for the Pacific Science Conference beginning 1 February, he had to toss for the last of the 26 Kiwi seats available on the 8 January flight (and lost).

Helo transport to and from Erebus also proved difficult. On 30 November while still with K5, Dibble, Paintin requested a helo for a move to the Fang and were assigned 6 December as the earliest opportunity. On 3 December Dibble and Paintin returned to Scott Base in the surveyor's snotrac. From then until 17 December, the days we were on the helo schedule began cloudy (sometimes clearing later but Erebus was always scheduled for 9 a.m. and not rescheduled later) and on fine days we were not on the schedule. Flights up Erebus need to be on a weather-opportunity basis, but with many parties waiting for the helos, good lobbying at McMurdo was needed for this. Few of the helo crews had flown up Erebus before. The crew rostered to take us to Fang on 17 December declined, and we were fortunate that other crews volunteered.

On 17 December a US/Japan/NZ party of 7 flew to Fang, and otway's party of 3 descended to Scott Base 8 days after they had completed their work. On 18 December, W. McIntosh, J. Gamble and J. Berg reached the Fang on 3 Skidoos and on 19 December, McIntosh's party (and P. Kyle) reached the summit hut on 2 Skidoos (one got stuck in snow) only 3 days after leaving McMurdo, but they were unable to take any load above Fang, and were not properly acclimatised, so they returned to McMurdo next day.

On 21 December a helo came up empty to take the US/Japan/NZ party to the hut, and then brought L. Bell plus cargo up from Scott Base. On 22 December the remaining cargo was flown up. This included a Yamaha toboggan (350 c.c.) which was subsequently used during surveys of the summit plateau. It was not tuned for altitude, was hard to start, and lacked power at low speeds. It is garaged in the hut for the winter.

On 27 December, the US/Japan party descended to McMurdo by helo on a clear but humid day. During the first attempt to land contrails enveloped the helo and it had to circuit while the pad cleared. On take-off, contrails page 32 again enveloped it and with visibility obscured, the crew were unaware that the helo rotated on lift-off, until they flew out of the cloud straight towards a tent. They avoided it but thundered over the hut at low level.

The NZ party were scheduled to descend on 30 December and asked for an afternoon flight. Instead they were rescheduled for the next day which was unflyable. The next scheduling was 4 January which was cloudy but clearing at 0800. We suggested the helo wait until mid morning, but they came at 9 a.m. and could not land. The cloud cleared, as predicted and we were brought down by Lt. Turner in a perfect flight (with the helo absolutely full) at 1830 McMurdo time.

On 11 January, Dibble, Bell and the Science Express camera crew flew to the hut and returned to Scott Base 2 1/4 hours later.

To summarise, few delays were experienced when ground transport was used, even on Erebus, but Dibble and Paintin were delayed 19 days waiting for Helos up (14 days) and down (5 days) Erebus, and Dibble was delayed a further 4 days waiting for a flight back to New Zealand.

Weather:

The weather on Erebus between 17 December and 4 January was generally fine with a marked absence of wind.

Instrumental observations reported on 0800 sked were:
18 Dec Clear sky, -13°C 30 kmph wind
19 Dec Clear sky, -13°C 16 kmph wind
20 Dec Clear sky, -17°C 10 kmph wind
21 Dec Clear sky, -19°C 0-15 kmph wind

Once at the summit, weather reporting (and radio skeds) were taken over by the field leader, Lindsay Bell.

Communications:

K4 had a compak and two VHF radios. We suffered less from the poor ionospheric conditions and high noise level on the Scott Base receiver than other field parties, and were often called upon to relay messages. This rapidly exhausted the batteries of Otway's party, and they were incommunicado for about a week. Our party took more batteries and also a solar panel and American radio. The latter performed disappointingly, but the solar panel (with a 50 ohm resistor in series to limit the current) proved invaluable for recharging the 10 volt VHF batteries. Voltage had to be constantly monitored to prevent overcharging, and for safety an automatic regulator would be essential.

The VHF radios were invaluable for communication with Andrew Harrall in the science lab at Scott Base, and also between Erebus Hut and the E-M survey page 33 party on the summit plateau. The latter circuit worked over only that quarter of the plateau area visible from the hut. A portable repeater is needed for a complete E-M survey.

Recommendations:

1.The IMESS group ensure that the Scott Base leader and technician for IMESS receive an integrated set of instructions for each year.
2.That the technician visit VUW and become familiar with IMESS equipment, recordings and results before going south.