Geophysical Observatories at Neumayer

Location: Ekström Shelf Ice, Atka Bay, northeast Weddell Sea Position: 70°39'S, 08°15'W

The geophsyical observatory at the German Antarctic research base "Neumayer Station" on the Ekström Ice Shelf is operating since 1992. It continuous the observatory program of the former "Georg von Neumayer Station" (GvN) which started in 1982. The new observatory was completely modernized concerning most of the electronics as well as the data acquisition systems and computing facilities.

The main tasks of the observatory are related to seismology and geomagnetism. The "seismic" and the "magnetic" observatory are located about 850 meters south of the base to eliminate any disturbances caused by the base itself and its activities. The magnetic observatory is seperated again by about 100 meters from the seismic observatory. At both sites special laboratory containers are installed inside deep snow caverns, initially about 7 meters below the normal surface, to ensure a minimum of wind induced noise and to guarantee stable temperature conditions. The caverns are covered by wooden roofs which were designed to withstand the weight of several meters of accumulated snow. Despite the ventilation of waste heat from the heated seismic observatory its roof started breaking in 1997 due to the formation of a solid ice layer directly above the plywood boards. Therefore all instruments inside the this observatory have to be moved to a new location in near future. The almost unheated magnetic observatory not aaffected by this and will remain in operation for some more years in this form. The left picture above shows a view from the seismic observatory to the magnetic observatory. The right picture above gives an impression how deep the observatories are now below the snow surface. The shafts have to be raised by another segment every second year due to snow accumulation. Currently the total height is almost 12 meters.

Inside the magnetic observatory a stable and thermally well insulated plywood container houses a fluxgate sensor triple for measuring the NS, EW and Z components of the Earth's magnetic field and a theodolite to determine the field's declination and inclination. Although there is no special temperature control the temperature inside this container is kept fairly stable at about 0 and +2 degrees Celsius only by some electric bulbs. For data acquisition the output signals of the fluxgate sensors are transmitted via cable to the seismic observatory. The sensors of the two proton precession magnetometers (PPM) for total field measurements are installed in small wooden shelters buried in the snow some 50 meters outside the seismic observatory. In the background of this picture the cardanic suspended fluxgate sensor triple can be seen., the foreground shows the theodolite for measuring the declination D and inclination I.

The seismic observatory is the central part of the geophysical observatory, but it is only a small part of the entire seismic network at Neumayer Station. It was given this name because inside its cavern the station's main seismometers are installed. Despite its name this observatory mainly serves for recording the geomagnetic field data which is performed with a Unix based workstation. This computer is connected to the station's main server via a fibre-optical link. All other workstations in the station's network have access to the observatory's hard disk. This link enables continuous online monitoring of the data acqisition inside the station's geophysical laboratory. This picture shows the 19"-rack with the various electronic devices for recording the geomagnetic field.

In the station's geophysical laboratory all incoming data are stored and refined for further processing. There are two main data streams to the laboratory: The digital geomagnetic and tidal gravity data from the observatory and the telemetered continuous digital PCM-encoded data from two remote seismological stations. The data from the the seismological remote stations are combined with the data from the observatory's seismometer to a single data stream. The resulting single data stream is decoded and transferred to another workstation for storage, automatic event detection and localization. The laboratory is the working place for two geophysicists. Besides processing and evaluation of observatory data the system management of the station's computer network is also part of their duties.

This picture is a panorama view of the geophysical laboratory at Neumayer Station. On the right side there are the radio receivers and PCM-Mixer and PCM-Encoder / Decoder for recording the seismological data. Beside the shelf with the PCM-eclectronics there is one of the two conventional endless paper chart recorders which are still very useful for a quick look on the seismic activity.