Fig. 1

A visual depiction of how the activity time-series (ATS) metric is calculated onboard the pop-off satellite tag (PSAT). (1) Tri-axial acceleration values are sensed at 8 Hz, and (2) are summarized as a single mobility (M) value (the mean standard deviation of the sum of Ax, Ay, and Az over a 3-s moving window). (3) The distribution of M over a set summary period is centered at zero, and a threshold value for HA events is established (the absolute value of the minimum of the centered distribution), such that (4) an M value greater than the threshold is considered a high-activity (HA) event. (5) The number of HA events is recorded over predetermined time-series (every 75 s) for transmission as ATS