A quest for signature management

Prominent among the many new systems on the future Canadian Surface Combatant (CSC) will likely be a next generation signature management system. And it will owe its capability to a research vessel named Quest and an international experiment called RIMPASSE.

Every ship has distinct signatures, some of which change as it deploys around the world. So as countries such as Canada replace aging war ships, the ability to measure and understand a ship’s signature without entering a fixed range has certain implications for ship design and onboard systems.

For the better part of three months in the fall of 2011, military research organizations from 16 countries including Canada, Germany, the Netherlands, the United Kingdom, Norway, France and the United States conducted a series of trials known as the Radar Infrared electro-Magnetic Pressure Acoustic Ship Signature Experiments, or RIMPASSE.

Central to the experiments were two research vessels, Canadian Forces Auxiliary Vessel Quest, and a German ship, Planet.

The objective of the experiments was to collect data from a number of locations and under various conditions to develop and demonstrate a prototype by 2016-17 that can then be developed by industry into a signature management system ready for ships expected to enter service in the early 2020s.

“The type of integrated signature management system that we are talking about really does not exist in industry right now,” Dr. Zahir Daya, advisor on signatures for Defence Research and Development Canada and the Canadian trial chief scientist for the RIMPASSE experiments, explains in his office in Dartmouth. “Industry will tell you they have different elements of it and that they can create the full thing, but access to research vessels with unique defence research capabilities is very limited. This was such an important trial that countries lined up to participate so they could get hold of the data.”

Signature significance
Every ship emits a variety of signatures. They can vary by location and water depth, climate, above or below water environments, and by the age of the ship and how much she has sailed. From infrared to visual, radar cross section, acoustic, magnetic and electric signatures, all can affect how the ship is detected and targeted.

The most studied in RIMPASSE, though, was the magnetic signature, which Daya divides into two parts: the permanent and the induced. “The permanent really depends on where the ship was built and what kind of steel was used. The induced depends on where you are in the world. The earth’s magnetic field is mapped so the induced part is rather easy to calculate: you put steel somewhere, it will have an induced component. The permanent is more difficult. Whenever you put a bunch of iron together, it will have some kind of magnetic field, and each is unique.

“Right now, if we send a frigate to the Gulf, it will stop in Augusta, Italy, for check ranging to better optimize the signature. But if we had a closed loop degaussing system, in principle you’d never have to do that. You’d be able to optimize on the spot, wherever you are. So with the RIMPASSE data, can we now develop the mathematical knowledge and models to be able to do this for any ship? That is direction we are working toward.”

Trial of the seas
The trial consisted of a series of experiments in different ranges involving shallow and open or deep water tests, under a tight and demanding schedule.

Following a brief preparation period in June and July to establish baseline acoustic and magnetic measurements, Quest departed from Halifax on August 3 for Loch Goil and Loch Fyne in Scotland to conduct acoustic noise transfer experiments, static ranging and dynamic ranging.

From there, Planet and Quest conducted open sea measurements before visiting two ranges in Norway, Herdla, a multi-influence range focused on mine threats with acoustic, pressure, electronic and magnetic sensors, and Heggernes, an acoustic range co-owned by Norway, the Netherlands and Germany. Measurements taken at the latter were similar to those in Scotland but under different bathymetries.

Quest then had her permanent magnetic signature “de-permed” at Friedrichsort in Germany before proceeding to Surendorf for above water experiments measuring infrared and radar cross section signatures while the magnetization settled. With the port half of the ship painted grey, Quest provided important infrared imaging data.

Experiments were also conducted to understand infrared signatures under solar loading conditions and to measure the efficiency of hull water cooling systems. “We were doing sensitive experiments on experimental infrared imaging seekers looking at the ship,” Daya explained. “We fired off flares without the system working and with the system working to measure when the ship was detected, or when the missile algorithm breaks lock from the ship and goes for the flare – it was easier to break lock when the ship was cooled down.”

The ships then conducted electric and pressure signature measurements in Auschau, a fixed range site in Germany, before arriving at the earth field simulator in Bünsdorf, a unique German (submarine) facility that allows the separation of the permanent from the total magnetic signature. Over six days in early October, Quest was run through a sequence of more than 600 different earth magnetic field settings, replicating signatures from Halifax to the Caribbean and even Australia.

“You’ll never have a pure reading of the permanent signature after a ship is built, so the question is, if you can understand the permanent part, can you make strides managing the magnetic signature?” Daya said.

Quest returned to Halifax on October 31 following a rough crossing of the North Atlantic, before conducting southerly latitude measurements near the Caribbean island of Sint Eustatius. In total, she visited 11 ranges over more than 100 days (Planet, by comparison, saw five ranges in 36 days).

Mining the data
Since the experiments concluded in 2012, participating countries have been working with the data, with key members developing different projects. Although Canada and Germany were the largest contributors, with Canada availing the signature management systems onboard Quest and Germany providing extensive use of high-demand ranging facilities, all countries contributed what they could, said Daya, who has been working full time on RIMPASSE since 2009. “It is an international collaboration that would otherwise have been impossible.”

For Canada, the focus has been on an integrated signature management system. Together with Germany, the Netherlands, Norway and Belgium, Canadian researchers are collaborating on what is being called the Onboard Ship Signature Management System through the German-Dutch led Centre for Ship Signature Management. Once a prototype is ready for demonstration, hopefully by 2016, the five countries will then return to the Baltic to conduct a smaller demonstration trial.

“The next step is to have modules that given measurement inputs will be able to make predictions for signatures in near real-time, and then other modules that given the signatures will be able to assess the susceptibility of the ship,” Daya said. “Each country could have its own algorithm in the modules. We could have competing algorithms during the demonstration.”

“Signature requirement, signature management is a two-way thing. What your threat and operational requirements are will determine your requirements for signatures and signature management. And once you know your signatures and signature management systems, you can determine your response given your threats.”

DRDC has been working with the Canadian Surface Combatant project, he added.

“When I look at the body of work that we have synthesized from everything we collected, we have distilled it down into what we believe the signature requirements should be. RIMPASSE made an important contribution to that.”

Author: Chris Thatcher (from Feb/Mar 2014)

Share This Post On
468 ad

Submit a Comment

Your email address will not be published. Required fields are marked *

Visit Us On TwitterVisit Us On FacebookVisit Us On LinkedinVisit Us On Youtube