Charting the 'Invisible Terrain'

By Rear Admiral Tim Gallaudet, U.S. Navy

EMW Today

The Naval Meteorology and Oceanography Command has many capabilities that can contribute to the Navy’s EMW campaign plan, similar to how it brings unique capabilities to the undersea warfare environment. In the undersea realm, meteorological and oceanographic (METOC) professionals measure the physical properties of the ocean and predict how the ocean affects acoustic propagation. This is similar to how electromagnetic waves proliferate.

An accurate knowledge of the atmosphere and an understanding of how current and future conditions impact EM wave propagation specific to that frequency and outputted energy are also critical to succeed in EMW. In a vacuum, our radar pulses and communications signals would travel in straight lines. But in the atmosphere, they are affected by different values of pressure, temperature, and relative humidity, with respect to height; all of these factors impact the speed of electromagnetic waves, which consequently refract toward areas of slower propagation speeds. This phenomenon impacts the transmitter’s area of coverage—and therefore the range that the transmitter can see a target and the range that a receiver can detect the transmitter. It also leaves areas of “shadow” and extended range returns. These atmospheric Navy METOC values are measured and predicted as part of our normal day-to-day operations.

The physical attributes of frequency and power are controllable, and the conditions of the atmosphere are measurable and predictable. These two facts allow us to optimize a transmitter’s potential coverage and effectiveness. The EMW campaign plan real-time spectrum operations (RTSO) capability is a map of the EMS with sensors identified by their frequency and bandwidth. Inserting METOC data into that RTSO capability is a key contribution to the EMW campaign plan. METOC professionals can use that information, along with our organic EM Tactical Decision Aid (TDA) of the Advanced Refractive Environmental Prediction System (AREPS) to help ascertain where the environment is conducive for shadows and extended range returns.

Navy METOC professionals know and understand the limitations of predicting the actual environment and can translate that knowledge to probabilities of EM performance. With the right atmospheric measurements and EMS competency, we will know when, where, and how long to transmit any type of EM wave throughout the EMS to optimally accomplish the assigned mission.

Advancing EMW in the Future

While Navy METOC personnel are performing tasks that make exploiting the EMS possible, there is room for improvement. In the undersea environment, we made small underwater platforms key to our sensing of the ocean medium. These unmanned undersea vehicle (UUV) platforms are deployed worldwide in the pursuit of making our oceanographic models better and to allow us to make smart decisions by using acoustic predictions to exploit the undersea domain. However, our capability to determine the environment conducive to EMW is hampered by our limited in-situ sensing capability of the near-surface atmosphere.

To address this limitation, the Office of Naval Research awarded a multidisciplinary, multi-university research project led by the Naval Postgraduate School known as Coupled Air-Sea Processes and EM Ducting Research (CASPER) to further explore the ocean and atmospheric impact on electromagnetic wave propagation. With new sensor technology and innovative approaches to ocean and atmospheric modeling, the opportunity exists to refine our skills at EM propagation forecasting. In addition to improving our ability to predict EM propagation paths, the CASPER project aims to better understand and predict the disruption of EM energy caused by weather systems and sea-surface wave and temperature conditions. These technologies will be rolled into making AREPS better and could lead to a unified propagation model linked with other predictive EMS decision aids such as RTSO.

The Naval Meteorology and Oceanography Command is also making investments in the electro-optical (EO) realm of the EMS. The same types of METOC fields that affect EM propagation, such as clouds, rain, sea salt, and dust, affect EO systems like night-vision goggles. With our transition partners at the Naval Research Laboratories, we are pursuing EO performance predictions that provide a capability for a nonspecialist to understand which wavelengths will be best used for relevant targeting and monitoring and high energy systems.

One of the most challenging aspects for dominating the EMS is the high variability of the atmosphere and the sharp gradients that make EM propagation complicated. There are three potential actions that will allow the METOC community to better characterize this variability and improve its support to the Navy’s EMW campaign plan.

1. Employ unmanned aerial vehicles (UAVs) for atmospheric sensing. METOC-specific UAVs would ensure that temperature, humidity, wind, and pressure sensors are transmitting the data back to operators on board and that the data would be routed to our production centers for future atmospheric predictions. The UAV profiles of the atmosphere can mimic the path of the EM wave by moving away from the ship’s sensor and measuring atmospheric data along the path of propagation instead of a single data point on board ship as with traditional METOC capabilities. The proliferation of these vehicles allows for more collection of METOC data, over a wider area than ever before.

2. Exploit all available airborne platforms. The capability exists to sense the environment from any aircraft and provide more environmental measurements than were once sensed by our weather balloons. Miniature atmospheric sensors are installed on commercial aircraft today, and commercial off-the-shelf solutions can be employed on naval aircraft to sense the environment.

3. Exploit “through the sensor” capabilities. One of Naval Meteorology and Oceanography Command’s most successful programs uses the SPS-48G air-search radar for Doppler weather data through an inexpensive software addition called the hazardous weather detection and display capability. This provides large-deck aviation platforms Doppler weather radar capability. Additional inexpensive software modules can also extract EMS data from organic EM sensors. This data will feed tactical decision aids for EMW prediction and validation.

Sun Tzu said, “Know the enemy, know yourself; your victory will never be endangered. Know the terrain, know the weather; your victory will then be total.” As the Commander of Naval Meteorology and Oceanography Command/Commander, Task Group 80.7, I am determined to know the weather and the environmental terrain as it affects EMW. We will integrate our knowledge of the physical environment to that of the EMS and exploit the vulnerabilities of the enemy, while protecting our advantage across all domains.

1. Navy Warfare Development Command, “U.S. Navy Fleet EMW Terms of Reference Guide,” 27 March 2015 (Version 1.0).

2. ADM Philip S. Davidson, USN, Comments to USNI-AFCEA West 2015, 10 February 2015.

Rear Admiral Gallaudet received a bachelor’s degree in oceanography from the U.S. Naval Academy in 1989. He received master’s and doctoral degrees in oceanography from Scripps Institution of Oceanography in 1991 and 2001. He is currently the Commander, Naval Meteorology and Oceanography Command/Commander, Task Group 80.7.


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