An operationally optimized ocean-bottom seismometer capsule

A new free-fall ocean-bottom seismometer capsule has been designed which is more versatile, lower cost, and easier to deploy than previous versions. The pressure case consists of a 1.3 m long 15.24 cm inside diameter aluminum tube. Positive buoyancy is provided by three 33 cm diameter glass spheres. Release is accomplished with dual explosive bolts which screw directly into the end cap of the pressure housing. The electronics consist of 3-component geophones, gain-ranging amplifiers and filters, multiplexer, 12-bit analog to digital converter, microprocessor controller, digital cassette tape deck, and acoustic transponder and command system. The gain-ranging amplifiers result in 128 dB of dynamic range. The batteries will power the electronics for three months. Checkout, data playback, and battery charging can be accomplished without opening the pressure case, considerably reducing the effort required to recover and redeploy the capsule. The microprocessor controller enables the system to be adapted to a wide variety of sophisticated oceanographic data sampling and recording experiments. The mechanical design is consistent with deployments of 1 year or longer. Its total estimated parts cost is U.S. $ 13,000.