A team from the Applied Physics Laboratory of the University of Washington (APL-UW) conducted underwater sound propagation exercises from 5 to 29 May 2010 aboard the R/V Roger Revelle in the Philippine Sea. This research cruise was part of a larger multi-cruise, multi-institution effort, the PhilSea10 Experiment, sponsored by the Office of Naval Research, to investigate the deterministic and stochastic properties of long-range deep ocean sound propagation in a region of energetic oceanographic processes. The primary objective of the APL-UW cruise was to transmit acoustic signals from electro-acoustic transducers suspended from the R/V Roger Revelle to an autonomous distributed vertical line array (DVLA) deployed in March by a team from the Scripps Institution of Oceanography (SIO.) The DVLA will be recovered in March 2011.

Two transmission events took place from a location designated SS500, approximately 509 km to the southeast of the DVLA: a 54-hr event using the HX554 transducer at 1000 m depth, and a 55-hr event using the MP200/TR1446 "multiport" transducer at 1000 m depth. A third event took place towing the HX554 at a depth of 150 m at roughly 1–2 kt for 10 hr on a radial line 25–43 km away from the DVLA. All acoustic events broadcasted low-frequency (61–300 Hz) m-sequences continuously except for a short gap each hour to synchronize transmitter computer files. An auxiliary cruise objective was to obtain high temporal and spatial resolution measurements of the sound speed field between SS500 and the DVLA.

Two methods were used: tows of an experimental "CTD chain" (TCTD) and periodic casts of the ship's CTD. The TCTD consisted of 88 CTD sensors on an inductive seacable 800 m long, and was designed to sample the water column to 500 m depth from all sensors every few seconds. Two tows were conducted, both starting near SS500 and following the path from SS500 towards the DVLA, for distances of 93 km and 124 km. Only several dozen sensors responded during sampling. While the temperature data appear reasonable, only about one-half the conductivity measurements and none of the pressure measurements can be used. Ship CTD casts were made to 1500 m depth every 10 km, with every fifth cast to full ocean depth.

The research reported here was a component of a three-year program at the University of Washington to improve fundamental knowledge that is important for developing new technologies and approaches to counter improvised explosive devices (IEDs). The focus of our component was to develop methods for identifying explosive materials using X-ray spectroscopy.

All chemical explosives store energy in specific, high-energy chemical bonds. Detecting and classifying explosives is a matter of analyzing the structure of these bonds by some method, either direct or indirect. One direct method is to measure the X-ray emission spectrum of the relevant elements involved in the chemical bonds, such as nitrogen or oxygen in a typical explosive. A complementary technique is provided by a particular type of non-resonant inelastic X-ray scattering (NRIXS).