IEEE Robotics & Automation Magazine - December 2016 - 31

Directional
Thruster

Rear Thruster

located hundreds of kilometers from sea ice and the open
ocean. This unique deployment and recovery method provides access to more remote areas than those that can be
investigated using other platforms and represents a likely
method for use in future planetary missions. A small-diameter (3.3 mm) optical fiber tether is used for deployment and
recovery of the vehicle as well as for real-time communication
and control. This lightweight tether has minimal impact on
the dynamics of the vehicle and provides sufficient bandwidth
for communication and control from the surface. Despite its
small displacement, the tether also provides a strong mechanical connection (rated at 272 kg) to the surface that ensures
vehicle recovery. The tether connects to the vehicle through a
reinforced termination that can support up to 453 kg.
The vehicle's maiden sub-ice voyage occurred during part
of the 2014 austral summer deployment of the NASA-funded
project, Sub-Ice Marine and Planetary-Analog Ecosystems
(SIMPLE), at McMurdo Station, Antarctica. The goal of the
deployment was to support a NASA scientific expedition and
provide an assessment of the under-ice vehicle and deployment strategy to help lay the initial groundwork for both terrestrial and planetary exploration. Final Icefin integration
took place in austral spring 2014, and its maiden voyage
beneath the ice occurred in November 2014. For system testing, Icefin was first deployed from a dive jetty on the sea ice
close to McMurdo Station. Following validation of the vehicle's controls and communications, it was deployed through
the ice at SIMPLE site E (Figure 2) on the McMurdo Ice Shelf.
Scientists and engineers collected video, sonar, and other scientific data for analysis. Icefin returned data of the previously
unexplored under-ice and seafloor environment adjacent to

Black Island in McMurdo Sound. Field deployment to Antarctica ended in December 2014. This article provides an
overview of Icefin design, including mechanical, electronics,
and control details, as well as a summary of the 2014 deployment field trials and lessons learned with extrapolations for
future polar exploration missions.
Background and Related Work
Antarctica is earth's southernmost, coldest, driest, and windiest
continent, with 98% of its land covered by a thick continental
ice sheet and 44% of its coastline consisting of permanent ice
shelves [10]. The average annual temperature at McMurdo
Station is -18 °C and can vary from -50 °C in the winter to
8 °C in the summer [2]. In addition to the continental ice
sheet and shelves, the oceans around Antarctica are extensively covered by both annual and multiyear sea ice (almost
20 million km2 area in the winter [3] and typically 2-5 m thick).
Although Antarctica's harsh climate prevents easy colonization, humankind has been driven to explore the continent for
almost two centuries. Divers and various observing platforms
have conducted exploration below the sea ice and in sub-ice
lakes in the Antarctic dry valleys via auger-drilled and melted
access holes. However, despite scientific interest, exploration of
the ocean environment beneath its thick ice shelves had been a
nearly impossible feat before the advent of new drilling technology, remote sensors, ROVs, and AUVs. Ice thickness and
harsh climate have limited the use of human divers and
manned submersibles for sub-ice oceanic exploration. Most
data currently collected from below ice shelves are derived
from long-lived ocean moorings set through the shelf via
hot-water-drilled holes and allowed to freeze into the ice.

(a)
Electronics

Wet Sensor

Directional
Thruster

Front

(b)
Figure 1. (a) The Icefin computer-aided design with modules and syntactic foam. (b) The Icefin modular vehicle partially assembled.
Modules (from left): rear thruster, directional thruster, electronics, wet sensor, directional thruster, and front.

DECEMBER 2016

IEEE ROBOTICS & AUTOMATION MAGAZINE

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - December 2016