2007 report
Progress: 45%
This highly technical task is divided into three main themes: long-range navigation under sea-ice, short-range communications and satellite telecommunications. A special technical workshop was organized by ATL at Farnham UK in late February 2006. Associated reporting can be found from project's intranet. Additionally, several members of the task participated in the Acoustic Navigation and Communication for High-latitude Ocean Research (ANCHOR) Workshop in Seattle USA (27/2 - 1/3/06). The workshop was organized partly because there is a clear need to agree globally on some common issues (e.g., communication protocols). The workshop provided also a forum for the DAMOCLES group to work together on technical details. Besides these two events, there has been some other meetings, such as a technical meeting between UPMC, Martec and ATL in late May 2006.
Long-range navigation under sea-ice:
The main objective of this work is to develop an under sea-ice localization and navigation system for gliders in DAMOCLES using low frequency sound sources and advanced estimation techniques. The extreme under ice conditions set hard constraints for the design of their navigation systems. The large uncertainty of the system arises not only from the difficult environment, but also from sensors, actuators, internal models and algorithmic approximations the robots use. Normal GPS based localization while on the surface is a rare exception and the system can not be build around it. Additionally, these robots have severe limitations when we talk about their maneuverability. On top of that, payload, energy and finance restrictions will make the case even more challenging. The actual work is focused on the detailed conceptual specification of the localisation and navigation system and algorithms for the gliders. There are several possible algorithms that could be used for localisation. The decision of which to use with DAMOCLES, should be made after testing the algorithms in situ or in realistic simulations. HUT has implemented extended Kalman filter, batch optimization and sequential importance sampling-resampling filter (SIR) and tested them in a simulator developed for DAMOCLES. Based on the localization estimate, a priori mission specifications and commands from the operator / Mission Control Software, the glider will perform the required navigation tasks. These tasks will include the following cases:
§ navigation towards a particular float (to get data from it),
§ navigation towards a particular AITP (to get data out to the users),
§ navigation towards a mooring site (to get data from it),
§ navigation towards open water (to get data out or for recovery purposes),
§ short range navigation.
The operational procedures for these various cases have been developed and will be implemented first in a realistic simulator and then in a real glider. Additionally, deliverables D8.1-1, D8.1-2 and D8.1-3 have been submitted.
Based on the work (literature survey, algorithms development, simulator testing and Deliverables) the development of reliable localisation estimation (odometry of the glider + low frequency acoustic information) method and suitable navigation algorithms for various tasks will continue.
The properties of SOFAR signals will be studied during winter 2006-2007 (Tara ice camp). These results will provide valuable information about the possibilities and restrictions of low frequency sounds under the sea ice cover.
The further testing of ENSIETA glider will provide the needed information about the dynamics of the vehicle and about the performance of the on-board sensors.
Above information is essential for the development of robust localisation estimation algorithm, which can then be tested extensively, first in a realistic simulator and then later inside a real glider. Furthermore, a separate hardware module will be designed, implemented and tested. This module will be connected to the main processor module of the glider and it will run the estimation algorithms required for the localisation of the glider. After testing, multiple modules will be manufactured and integrated to the gliders before the final sea testing. Additionally, for successful navigation the following three documents must be defined: Mission Specifications (for gliders), Deployment and Recovery Plan (for gliders, floats and AITPs), and Standard Information Package (from operator via AITP to gliders). For details, please refer to Deliverable D8.1-1.
Short range communications
Aquatec Telemetry, the responsible partner in short range communications, has so far made the following major progress steps in the DAMOCLES project:
§ Acoustic propagation simulation based on the complex under-ice environment in the in the Arctic, this entailed writing Matlab code to perform ray tracing based on profiled data of temperature and salinity in varying regions of the arctic.
§ Design of electronics for the Acoustic modem, including low power operation to limit power requirements of the instrumentation to be attached to the modem.
§ Lab based tests on Acoustic modem include acoustic transmission / reception tests, data logging facility and communications with 3rd party instruments using the WHOI open protocol standard.
§ Submission of: - "Deliverable D8.1-4 - Standards and protocols and reporting for short range communication high frequency systems"
§ Designed and built specialised acoustic array for use in gathering data to aid the simulation of the arctic environment throughout the project.
In the near future Aquatec Telemetry will focus on the following issues:
§ Finish acoustic testing in shallow water, under ice conditions, in Finland or similar.
§ Finalise communication algorithms to use in the modem software.
§ Integrate the modem with gliders, floats, AITP's, and the tomography array (for which 4 modems are required)
Make 15 further units for the projects use.
Two Iridium modems have been acquired and are being tested. A complete system for the reception of all the messages coming from various platforms equipped with Iridium modem is under development, in order to ensure the safeguard of the data and to redistribute these data in near real time at the laboratories concerned. Two protocols are available: point to point and Short Burst Data (SBD). Due to the complexity of the point to point protocol, we suggest to use only the SBD protocol. The server to receive the data (storage and redirection toward the different labs) is ready. Detailed information about the volume and the frequency of data to be transferred daily must be specified by the partners, before this task can be finalized. The deliverable D8.1-5 has been submitted.
