The float was launched in a triad with NPS#8 and NPS#10 about 100 km southwest of San Francisco (Figure 2). The floats in the triad were launched in a nearly equilateral triangular pattern with a side of about 8 km.

Immediately after launching the float was entrained by the undercurrent and moved along the coast for 27 days till September 29, 1993. At Punta Gorda (Figure 1), the trajectory of NPS#4 curved offshore and then passed over the Gorda Escarpment and the Mendocino Ridge. Then it moved southward in a relatively smooth trajectory. At the time of surfacing the float appeared to be in a mesoscale eddy of radius 67 km and period 35 days.

The float was ballasted for 350 dbar but the real depth reached by the float was between 218 and 280 m (Figure 3). After launching the float settled at 240.4±9.4 dbar and sank to 258.1±9.8 dbar after it curved to southwest on October 13, 1993. While the float was moving in the Undercurrent, the temperature was gradually decreasing from 8.9 till 7.2 C and was 7.4±0.2° till it was entrapped by a mesoscale eddy on December 8, 1993. For the rest of the mission the float remained in cooler water with temperature 7.2±0.8°.