Table 1 GRACE components and specifications

Hull dimensions

103 × 20 × 30 cm (L x W x H)

Tail-to-nose length

140 cm

Wingspan

60 cm

Weight

20 kg

Robot hull material

Carbon fiber

Battery capacity

555 W H Li-ion polymer (approx. 5 days of continuous actuation with 1400 dive cycles @ 5-min intervals)

Processors

Raspberry Pi Zero W, Microchip dsPIC30F6014A MCU

Communication

XBee

Positioning

GPS and pressure sensor

Orientation

VN100S IMU and attitude and heading reference system

Buoyancy tank volume

190 mL

Pitch control^a

+ 40° (pitching up), − 25° (pitching down)

Average swimming speed

25 cm/s

Average glide speed

13 cm/s (as low as 5 cm/s against current and a high of 35 cm/s with current)

Environmental sensors

Dissolved oxygen and temperature, photosynthetically active radiation, freshwater blue green algae, chlorophyll