The government announced yesterday the launching of a sophisticated undersea research station that allows scientists to work for "virtually unlimited time" to examine the ocean depths.

The National Oceanic and Atmospheric Administration (NOAA) said the 81-ton station, called Aquarius, has been placed on the floor of the Salt Water Canyon off St. Croix in the U.S. Virgin Islands.

The $5.5 million station, which is 43 feet long, 12 feet wide and 16 1/2 feet high, has three compartments and can house up to six people. It replaces the undersea station Hydrolab, which completed nearly 200 missions between 1966 and 1985 for NOAA.

The new station "makes it possible for scientists to live and work on the ocean floor for virtually unlimited time, allowing a nine-hour day of research before returning to the habitat," the agency said.

During the next two years, the Aquarius is to be used in various undersea research projects, including fisheries studies, oceanography, marine engineering research and studies into the cause of coral bleaching in the Caribbean.

The station is connected by an umbilical system to an unmanned surface support boat and functions without support from the shore. If power or air is interrupted, an emergency system activates, providing occupants up to 72 hours for decompression and swimming to the surface, the agency said.

The main chamber houses sleeping areas, laboratory equipment, computers and a galley. Scientists may view sea life through observation ports in the living compartment. A video system allows monitoring of sea bottom and surface conditions.