SLA-OBS (Self-Landing and Ascending Ocean Bottom Seismometer)
A SLA-OBS is an autonomous oceanic seismic station, consisting of a buoyancy unit, an anchor weight,
a data recording system with an extremely precise oscillator, the sensor system (usually one hydrophone and a three-channel
geophone) and the power supply. As soon as the station touches the sea bottom, the geophone is lowered to the ground
by an extension arm in some distance from the station to uncouple it from the frame.
Developed in cooperation with  K.U.M. Gmbh
,Kiel, SEND GmbH offers a complete solution for seismic ocean bottom surveys in deep sea environments.
The OBS has an extremely flat profile which minimizes noise induced by frame vibrations and can be
deployed in depths up to 6000m. Recording times depend on the selection of the data logger, the sensors
and the battery capacity. By utilizing an additional pressure cylinder for batteries, the recording
time can reach well over a year.
The anchor weight is made from steel and mounted to the OBS-frame. At mission completion, an acoustic signal triggers
the ejecetion of the anchor weight and consequently the bouyancy unit will lift the station back to the surface.
Two pressure tubes are housing the ejection system, the seismocorder and the power supply. They can be opened easily
onboard the vessel to retrieve the data and to prepare the system for a new mission in very short time.
For locating and retrieving the OBS, a flag, a radio beacon, a flash, and the signaller of the ejection system are
mounted to the OBS frame. Titanium alloys are being used predominantly for the modules of the SLA-OBS to ensure
the corrosion resistance required in deap sea environments.
Specifications:
- weight: OBS: 240 kg (529 lb), anchor: 70 kg (154 lb)
- pressure tube: titanium cylinder
- buoyant material: syntactic rubber foam
- max. deployment depth: 6000 m (19.685 feet)
- retrieval trigger: acoustic trigger and time controlled trigger
- retrieval accessory: radio beacon, flash, flag, optional: GPS
- power supply: up to 72 D-cells or accumulator pack within pressure tube
- data rekorder: SEND Geolon-MES or MLS, Methusalem-MBS, 16-24 bit dynamik range, sample period from 16 to 0,1 ms
- geophone: e.g. K.U.M./Carrack 3C, recording bandwidth down to 14, 4.5 or 1 Hz, optional: gimbal-mounted
- hydrophone: e.g. HTI04 or similiar
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PDF brochure OBS Systems
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