Digital Ocean: Making Subsea Data More Easily Accessible
By Tom Mulligan
The digital ocean is a reality and U.K.-based digital
communications marine technology firm Sonardyne International Ltd
is one of the organizations driving innovation to enable the
extension of electronic and communications connectivity into the
subsea domain. Based on a presentation given by Tom Rooney, Lead
Trainer at Sonardyne, at the Digital Ocean conference held in
Galway, Ireland in June 2017, this article describes the current
state of play in the subsea acoustics and optical communications
technology field, presents examples of the many ways these
technologies are being applied and considers how the digital
ocean may work in the future.
U.K.-based subsea acoustics and digital communications specialist
Sonardyne International has been a major player in the offshore
energy sector for many years. Its technology portfolio has been
applied to the high-precision positioning of structures and
equipment, to the navigation of unmanned vehicles, digital
acoustic and optical communication systems, to asset monitoring
and data logging and for high-resolution subsea imaging. With
millions of dollars being spent daily, oil and gas sector
companies are the most demanding customers, as they expect high
levels of reliability and robustness, highly efficient operations
and supplier support in the harshest of environments. It was this
level of expectation that drove Sonardyne's research into and
development of new communications technologies for use in the
subsea environment.
Maritime security is also a key market for the company, with
technology and application variations on a similar theme to those
of the oil and gas sector, thus demonstrating the adaptability of
its technology to a wider variety of different application areas,
including ocean science, exploration, aquaculture and other
similar markets.
Technology Platforms - Acoustics
Sonardyne has developed an industry-leading wideband digital
communications platform upon which most of the company's acoustic
systems are based which is now in its sixth generation (6G). The
'pin-up' product for this technology is the Computing and
Telemetering Transponder (Compatt 6), a highly adaptable and
configurable instrument that is used in a wide range of
applications. It is made up of an acoustic transducer with
different frequency-band and beam-width options, advanced
processors, batteries, an optional release mechanism, and a suite
of science-grade sensors. In total, there are more than 3,000
possible configurations of Compatt 6. Here are some of the ways
they are utilized:
Positioning - Deployed with other transponders
on the seabed, Compatt 6 is used as a reference for Long BaseLine
(LBL) positioning, a concept similar in operation to above-water
global positioning, ie GNSS. LBL uses ranges measured by acoustic
'time-of-flight' calculations to determine with high precision
the position of a vehicle or structure using trilateration.
Compatt 6 can also be used in vessel dynamic positioning (DP)
applications using an Ultra-Short BaseLine (USBL) transceiver
deployed from a vessel, the acoustic ranges measured from seabed
references being used to aid the vessel/oil rig hold station
above an oil well or subsea structure. Finally, as a mobile
transponder, Compatt T6 can be attached to a vehicle or structure
to acoustically interrogate a network of LBL Compatt 6s in order
to calculate its position, or it can be tracked from the surface
using USBL.
PIES - The Pressure Inverted Echo Sounder (PIES)
unit is a variant of Compatt 6 that obtains average sound
velocity of a water column by measuring both pressure and the
time taken for a transmitted acoustic signal to reflect off the
sea surface. The unit is also capable of measuring other oceanic
properties such as local temperature, depth/tide variations, unit
pitch/roll and unit battery life. PIES units store processed and
raw data on an internal memory card: these data can be recovered
acoustically (e.g. from a passing subsea vehicle or from the
surface) while the transponder is deployed, or recovered serially
once the unit is remotely released and brought back to the
surface.
Autonomous Monitoring - An Autonomous Monitoring
Transponder (AMT) has all the functionality of a Compatt 6 with
the addition of autonomous logging and text messaging and can be
configured to autonomously log sensor and baseline data at
user-defined intervals. The data are logged to an SD card that is
retrieved acoustically while the transponder is still deployed or
serially once the transponder has been recovered, making the
system useful for operations such as the long-term monitoring of
seabed settling and tectonic plate movement.
Fetch - Sonardyne's wireless autonomous
sensor-logging node system Fetch provides the same functionality
as an AMT transponder but is housed in a glass sphere to give
excellent corrosion resistance for long-term deployments. The
design of the housing and built-in stand allows the instrument to
be 'free fall' deployed to land upright, thereby reducing both
deployment time and cost. The main applications for AMT/Fetch
units are seabed deformation and environmental monitoring and the
tracking of tectonic plate shifts, subsea earthquakes and, when
partnered with a surface communication gateway buoy, detecting
tsunamis.
Subsea Monitoring Analysis and Recording Transponder
(SMART) - SMART has been developed to cover complex
asset monitoring applications. Also part of Sonardyne's Sixth
Generation (6G) product range, the system combines low-power
electronics, long-duration data logging, subsea data processing
and acoustic telemetry into a single, easily deployed instrument.
SMART has the flexibility to interface with a wide range of
internal and external sensors and other data sources utilizing
standard or bespoke data analysis algorithms to provide operators
with key data when they are needed.
The advanced capability offered by SMART enables the technology
to be used as either a primary or backup subsea monitoring system
for a variety of tasks such as monitoring of subsea structures
including well heads and risers. The system can also be
configured for mooring-line and pipeline observation, both for
commissioning work and for longer-term monitoring. In fact, with
its ability to interface with most data sources, SMART can be
used just about anywhere information on the performance or
condition of subsea assets needs to be accessed.
SMART includes digital and analog inputs that can be configured
to connect to multiple data sources. Internal sensors available
for motion measurement include accelerometers, angular rate
sensors and inclinometers, as well as standard and high-precision
pressure and temperature sensors. External sensors that can be
interfaced include pressure sensors, strain gauges and acoustic
Doppler current profilers. For more bespoke applications, custom
interfaces can be created to link to instruments such as
corrosion monitors or vibration measurement tools.
A low-power data logger is a key feature of SMART, enabling data
received from external and internal sources to be securely
archived. A key benefit of SMART is its ability to process raw
data in the subsea environment to provide value-added
information, while the advanced data acquisition and processing
system, the heart of SMART, contains a highly capable processor
that can run sophisticated user-specified algorithms and perform
simple data analyses such as min/max/mean statistics and
thresholding for alarms and critical event reporting. By reducing
high-bandwidth sensor data to small, critical packets and by
efficiently managing power consumption, long deployment times can
be achieved from the internal battery pack, thereby enhancing
users' knowledge of the subsea environment.
In addition, where surface analysis of the telemetered data
requires a more thorough review of sensor parameters, SMART
enables acoustic recovery of raw data from specified time ranges.
Alternately, the system can be coupled via an Ethernet connection
to BlueComm (Sonardyne's high-bandwidth through-water optical
communication link), enabling larger quantities of data to be
retrieved from an ROV or AUV. All logged data can be downloaded
from safe storage when the unit is recovered.
The essence of SMART is flexibility and configurability, and the
ability to connect to different sensors and data sources is an
integral part of the SMART product line. However, these are not
the only options: SMART is available in a range of materials from
aluminum and aluminum bronze through super-duplex stainless steel
for the highest possible corrosion resistance. Other options
include longer 'maxi' housings for increased battery capacity and
different connector types and, if required, other functions,
including acoustic positioning, can be added to the monitoring
system.
Technology Platforms - Optical Communications
In addition to developing acoustic technologies, Sonardyne has in
recent years moved into the area of free-space optical
communications, successfully bringing to market high-speed
underwater modems.
Bluecomm - BlueComm is a through-water wireless
optical communication system that has been developed to transmit
subsea data, stream video and perform tetherless vehicle control
at very high speeds. The BlueComm modem family is currently made
up of three variants: BlueComm 100 is optimized for shallow-water
'high ambient light' operating environments and offers a good
balance between data rate and range; BlueComm 200 sends data at
up to 12.5 Mbps and is suitable for deep or night-time
operations; while the dual laser configuration of BlueComm 5000
supports data transfer rates of up to 1,000 Mbps.
BlueComm uses the electromagnetic spectrum rather than acoustic
pressure waves to transmit high volumes of data. Typically
operating in the 450nm blue region of the spectrum, BlueComm can
achieve data rates of greater than 500 Mbps. This optical data
transmission technology is highly efficient, enabling 1 Gb of
data to be transmitted with the energy contained within a single
lithium D-sized cell over distances greater than 150 meters.
The applications for Bluecomm are extensive: used in conjunction
with Sonardyne acoustics, low-bandwidth data can be transmitted
acoustically (for example by switching on the optics remotely)
and high-bandwidth data such as video or sonar imaging data files
can be transmitted using the optical method. Data from seabed
data storage centers or data-gathering vehicles can be collected
by AUVs and then relayed to ASVs or manned surface units for
transmission to ground stations via satellite.
Inertial systems - To complement its
state-of-the-art acoustic systems and provide the best possible
positioning solutions for subsea vehicles, Sonardyne has
developed its own inertial systems, Lodestar and SPRINT. Lodestar
is a combined solid-state attitude and heading reference system
(AHRS) that is upgradable to become the SPRINT acoustically-aided
inertial navigation system. The unit is comprised of three
high-grade, high-reliability, commercially-available ring laser
gyros (RLG) and accelerometers. The sensors used are the standard
for commercial aviation and have a proven track record of more
than 15 years and a mean time between failures (MTBF) of more
than 400,000 hours.
Lodestar AHRS supports serial, Ethernet and industry-standard
telegrams for easier interfacing and advanced outputs such as
acceleration and rotation rates are also available. On-board data
storage and backup battery functionality ensure continued
operation and no data loss even if communications or external
power is lost.
SPRINT is an acoustically-aided subsea inertial navigation system
for subsea vehicles that makes optimal use of acoustic aiding
data from acoustic USBL and LBL positioning and other sensors
such as Sonardyne's Syrinx Doppler Velocity Log (DVL) and
pressure sensors. This improves position accuracy, precision,
reliability and integrity while reducing operational time and
vessel costs. The system extends the operating limits of USBL
transmission and can dramatically improve the operational
efficiency of LBL systems. Sonardyne's new third-generation
SPRINT unit offers power pass-through to aiding sensors, thereby
reducing cabling and interfacing complexity.
SPRINT shares the same hardware platform as Lodestar and is a
combined AHRS and INS system: running both the AHRS and INS
algorithms concurrently allows inertial navigation to start or
restart instantaneously on receipt of a position update, as the
AHRS seamlessly provides orientation to the INS on start-up,
avoiding the lengthy 'alignment' period common to other INS
systems. Thereafter, the separate AHRS- and INS-computed
orientations are autonomously monitored as an indication of
system health.
The levels of accuracy provided by Sonardyne's acoustic-aided INS
system SPRINT-Nav are now enabling operators to conduct mobile
subsea laser mapping and metrology. Set-up and imaging
data-gathering times are greatly reduced and the post-processed
results achieved on the numerous trials and experimental projects
completed in 2017 have been reported as meeting all user
requirements.
Future Challenges
The challenges that remain to be addressed to complete the
introduction of automated subsea navigation, positioning and
communication center around achieving efficiency of operations
and the use of smaller vessels. For example, the introduction of
autonomous surface vessels (ASVs) will represent a culture
change, with operator safety cases relying on redundancy and
fallback systems to control vessels in the event of satellite
navigation failure or error. Other challenges include the
introduction and successful uptake of collision avoidance
systems.
Sonardyne is able to provide a complete suite of integrated
systems required for marine autonomy. Platforms such as its
AvTrak 6 instrument, which is optimized for AUVs, uses the
company's acoustic systems to enable long-distance, two-way
low-bandwidth data and communication transfer, while the longest
possible distances are achieved using acoustic-relay
transponders, thereby greatly increasing the operating ranges of
autonomous craft. Position data telemetry from USBL systems can
be sent to a subsea vehicle's INS navigation solution processor
as part of routine tracking communications and AUV status
information can be sent back via the same process. This same
telemetry can be used to control systems on the AUV, such as
those that update the mission, or to change the settings of
on/off sensor or optical modems. In the event of vehicle failure,
the AvTrak 6 will also act as an emergency locator beacon, going
into standby mode to save its independent battery, and it will
wake up and respond to interrogations from any Sonardyne 6G
system.
Where to Next?
Sonardyne has been pioneering digital oceanography technology for
more than four decades yet the list of applications for the
company's technology grows year-on-year, particularly where
automation and remote operations are concerned.
Modern technology can land a spacecraft on an asteroid or fly one
through the rings of Saturn from a control station on earth, and
therefore Sonardyne believes that the operation of an underwater
drone in the Earth's oceans is easily within human capability.
The company stresses that with fewer (or no) people at sea, the
provision of useable data for control, condition-based monitoring
and data gathering is paramount, but recognizes that operating on
or under the ocean presents significant technical and
environmental challenges.
Sonardyne also points out that lines of communication are not
point-to-point connections, but that they rely on multiple
systems working together, operating in different mediums and
changeable environments and with varying bandwidths across the
internet, linked via fiber optics, satellites, short-wave or
local wifi networks, acoustic modems, optical modems, Ethernet
connections and LANs, with a multitude of data formats, protocols
and operating systems that engineers have to somehow splice
together to provide the seamless connectivity expected by users.
Thus the main challenge in achieving effective integration of
complex systems is interoperability, with the digital
communications companies working together to share information
and agree on standardized data strings and protocols. The
aviation and automotive industries have demonstrated the success
that can be achieved by working in this way, and Sonardyne
believes that all sections of the maritime technology industry
stand to gain from a collaborative working approach: the digital
ocean is already here - it is up to the global marine community
to shape it in the way that benefits the growth of the industries
that will be using it.
Mar 12, 2018