National Security Technology Team Ardent About At-Sea Tests

by Paulette Campbell

For nearly three decades, the National Security Technology Department has been conducting at-sea tests and research for a variety of Navy and Department of Defense programs. Recently, nearly 40 NSTD scientists, engineers and data processors journeyed to the Gulf of Alaska for Ardent-3 to explore underwater acoustics.

The data collected may help the Navy to, among other things, better detect and classify slow-moving submarines operating in the world’s oceans. “Optimizing acoustic sensors for submarine detection requires knowledge of both the structure and behavior of the originating signal and the background noise field,” explains Steve Root, an assistant group supervisor in NSTD’s Acoustics and Electromagnetics Group and the project manager for Ardent-3.

The tests, conducted in July and August, involved the use of a towed-array  system designed and built to measure noise in the very low frequency regime. The acoustic arrays measure two inches in diameter and 2,000 feet long. The system consists of a wet-end component that serves as the in-water acoustic sensor; a towing and handling system used for deployment and retrieval and for stable towing while taking measurements; and a data acquisition and processing system, which records the data and displays processed acoustic measurements, as well as the status and health of the array’s sensors.

Testing and Integration

Conducting at-sea tests involves much more than putting the right people on the boat, says Ralph Brown, of NSTD’s Engineering and Testing Group. “We begin years in advance, designing, fabricating and testing equipment, then pack the gear and transport it – all before the at-sea testing even begins.”

While still at APL, they conduct a full-system integration process that involves hooking up the big pieces of equipment to the computers, turning the power on and seeing how it works. “Typically there are lots of bugs, so we spend time working out all the kinks,” Brown says.

With Ardent-3, because of the size of the acoustic arrays (the reelers are eight feet wide, 12 feet long and 10 feet high and, when loaded with arrays, weigh 52,000 pounds), the engineers conducted the tests in the parking lot near Building 49.

Packing It In

After two months of testing and integration, the two-week packing process began. The big pieces – the reelers and acoustic arrays – filled about seven flatbed trucks, and the smaller pieces – the computers and electronic equipment – were loaded on several full-size trucks.

After the equipment arrived at the staging area, engineers and welders spent several days installing it on ships. “You plug in all the equipment, see that everything works, and then remove the mooring lines for the ship, and away you go,” Brown says.

The Science Sailors

These at-sea experiments require a multidisciplinary team, and Root’s squad consisted of 37 APL staff members on three different platforms. On the acoustic sensor tow vessel were six scientists largely responsible for running experiments and ensuring data quality; six array engineers and technicians tasked with deploying and retrieving the towed array and making repairs; and two environmental scientists, because, as Root notes, “the proper interpretation of the acoustic data requires a thorough understanding of the oceanographic and meteorological environments.”

Also aboard the acoustic sensor ship were five data acquisition and processing engineers to ensure that acoustic data were properly archived and all real-time processing systems operated properly; and three operations specialists who monitored the overall progress of the tests, coordinated the platform movements and scheduled the daily routines aboard each vessel.

A second ship with seven APL staff aboard operated an acoustic transmitter. The crew included two environmental scientists, two operations specialists and a principal acoustic source engineer, who assembled a complete data set of source transmissions to support post-test analysis. Two people operated a conductivity-temperature-depth sensor.

APL also had three personnel in Navy P-3 aircraft who operated special data acquisition equipment and collected oceanographic information from air-deployed probes. They also helped the Navy aircrew gather information using organic radar and optical sensors. Root and his band of science sailors spent 34 days at sea working in shifts continuously, seven days a week, 24 hours each day. “About a third of the staff got sea sick during the first couple of days, but after that it was smooth sailing, in 54-degree temperatures for the most part,” Root says.

Once the tests were completed, Root’s team made its way back to the West Coast, off-loaded the equipment from the ships and on to trucks bound for the Lab for repairs, adjustments and storage before the next trip.

Future Tests

There may be an Ardent-4, but Root says that is still under discussion. NSTD conducts about one Ardent exercise every two years and several sea tests each year in support of other departmental projects. “While this is an absorbing and expensive process, it is well worth the investment because it provides the U.S. Navy keen insights into the practical application of today’s state-of-the-art technology,” Brown says.