Review of Autonomous Undersea Vehicle (AUV) Developments 
presence of a notchlike magnetic low at the center of the new flow, which has been interpreted 
to be related to the thermal demagnetization of the underlying feeder dike. 
Figure 23. ABE Launch 
The survey with ABE flew at an altitude of 20 meters above the bottom and covered an area of 1 
kilometer by 300 meters with about 20-meter spacing between tracklines. ABE was designed to 
investigate how this anomaly changes with time, thereby providing constraints on the cooling 
and structure of the lava flow. 
In 1996 ABE was back on the Juan de Fuca Ridge, this time in conjunction with the ROV Jason. 
ABE mapped the magnetic field above a feature called New Flow, flew over Cage Seamount, 
and explored the Gorda New Eruption site. Long-baseline navigation significantly improved, 
and ABE flew closed-loop tracklines using its in-hull navigation in real time. This made the 
surveys much more efficient and gave more direct control to the science party. 
ABE's standard data products include the following items: 
e Vehicle position determined at the long-baseline (LBL) transponder cycle interval, 
typically every 10 seconds (water depth dependent). These data are obtained by ABE 
directly, so errors caused by uncertainties in the sound velocity profile of the water 
column are minimal. 
53 
