American warships assigned to the West Pacific (7th Fleet) have been receiving more China-specific electronic sensors and jammers to deal with Chinese weapons that are not exported and expected to only reveal their abilities in an actual shooting war. Most U.S. surface warships have a basic version of the AN/SLQ-32 (or "Slick 32") that can monitor enemy electronic transmissions in real-time, identify them as much as it can and instantly share the information with nearby U.S. forces.
During the Cold War Russia was the primary naval opponent equipped with advanced electronic sensors and weapons and Slick 32 capabilities were installed on American ships expected to encounter Russians. Since 2019 ships with SLQ-32 have been receiving a series of major upgrades called the SEWIP (Surface Electronic Warfare Improvement Program) The full name of the SEWIPed gear is AN/SLQ-32(V)7 and it was developed as three major components or “Blocks”. Block I improved the basic capabilities of SQL-32 and improved the displays and UI (User Interface). Block II improved detection and identification of electronic signals near the ship. Block III included some major capability upgrades. This meant determining how to respond to an attack by identifying which electronic or non-electronic (missile, autocannon) system on the ship was best suited for the task and rapidly using it, as well as additional defenses required. The complete SEWIP upgrade enables a ship to make the most of its defensive weapons and quickly incorporate data on new enemy electronic and non-electronic weapons. BLOCK I and II were available in 2019 but the more complex Block III is only arriving in 2021 and 2022.
The Chinese have been introducing a lot of new radars and other sensors along with ECM (Electronic Countermeasures). Block III had to handle all these as well as new systems and do so fast enough to keep ships protected. To do this SEWIP is taking advantage of more powerful data processing systems to provide each SQL-32 system with rapid machine learning, also called AI (Artificial Intelligence) which quickly figures out what a new electronic signal or combination signals is and what it is capable of. This means which offensive electronic countermeasures; jamming or deceptive signals (spoofing) are best suited to protect a ship.
SLQ-32/Slick 32 first appeared in the late 1970s and since then has quietly evolved to deal with new threats. That development continued after the Cold War ended in 1991 as the Russian threat largely evaporated, along with most of the huge Russian fleet. By the late 1990s, it became apparent that the Chinese were picking up where the former Soviet Union left off and since then AN/SLQ-32 has been evolving more rapidly to keep up with new Chinese capabilities. One of the other China-specific items added to the U.S. Pacific based warships is the AN/SLQ-59. This is a TEWM (Transportable Electronic Warfare Module) device only found on 7th Fleet ships. The hardware is a refrigerator-size metal device found mounted on the exterior of warships. The capabilities of the AN/SLQ-59 are one of those military secrets China is eager to obtain. There is little unclassified information about AN/SLQ-59, other than the official name and that it is part of TEWM and related to the larger AN/SLQ-32 family of sensors.
When it comes to EW (Electronic Warfare) the Chinese Navy has one major disadvantage, it’s relatively small and constricted coastline compared to the United States. This limits the areas where new navy electronic systems can be tested over water without electronic surveillance by foreign nations. The American military has the largest and most experienced force of long-range electronic surveillance aircraft. What exactly these aircraft are looking for and, more importantly, what they discover, is kept secret. Sometimes the results of discoveries by these surveillance aircraft, and ships, does become public.
Navies and air forces seek to detect new enemy electronics used in offensive weapons and defensive systems. This is where the U.S. Navy has long had an edge. Not only does the navy have several AGI (Auxiliary General Intelligence, or electronic reconnaissance) ships, but also specialized AGI aircraft. How important these aircraft are to the Chinese was made clear in the late 1990s when American electronic reconnaissance aircraft were increasingly harassed when found flying off the Chinese coast, outside of Chinese territorial waters (everything 22 kilometers from the coast) but close enough to detect the electronic emissions of Chinese electronic systems. The Chinese were trying to drive off these aircraft and that led to a collision between a U.S. Navy EP-3 electronic reconnaissance aircraft and a Chinese fighter in April 2001.
Since the EP-3 incident, run-ins between Chinese and US aircraft have continued along the Chinese coast. There have been no more aircraft lost or forced to make an emergency landing. The Chinese have increased the number of AGI ships. It is feared that China might eventually be able to station EP-3 type aircraft in Cuba or Venezuela but that would still not enable them to monitor U.S. Navy tests of new equipment off the west coast of North America or Hawaii, except occasionally when one of their new aircraft carriers was in the area.
At the time of the 2001 incident, China had begun developing a modern AGI ship. China now has nine Dongdiao class Type 815 AGI vessels. In a tradition stretching back to the Cold War (1948-1991), AGIs regularly show up uninvited at naval exercises held in international waters. There these ships loiter while collecting all the electronic and photographic data they can. What AGI ships cannot do is fly off the coast on short notice to monitor tests of new weapons and sensors.
While the growing number of Chinese warships visiting foreign waters appears threatening, the AGIs are not warships but in many respects are more of a threat. In the last twenty years, China has become a major user of AGIs which, during the Cold War, were mainly used by the U.S. and Russia. The Americans still have a lot of them but Russian AGIs have largely disappeared, and are now replaced by even more capable Chinese models.
The growing military use of electronic sensors and communications (ESM or Electronic Support Measures) has made forces more capable, but also more vulnerable, especially if enemy AGIs spend a lot of quality time monitoring your operations.
As a counter to ESM scrutiny and vulnerability (to detection in combat) equipment can be disguised where possible. Signals can be varied in some circumstances. For equipment that is detected by shape and composition, like aircraft and ships, their shape and substance can be designed to minimize detection. This is the essence of the stealth technology that the United States is applying to a number of vehicles, especially aircraft. Small ships, aircraft, helicopters, and vehicles loaded with sensors do most of the collecting. Low flying satellites are useful for catching signals deep inside a nation’s territory. UAVs and unmanned surface and subsurface vessels are used also, plus robotic sensors that are left on the ground or sea bottom. The collection involves more than sensors. Recording devices, foreign language interpreters and signal processing equipment also come into play.
Computers are increasingly crucial in sifting through the ocean of data swept up. Huge libraries of signals are collected, analyzed and boiled down to manageable amounts of data which friendly troops and weapons can use. ESM has been so successful that one entire class of sensors, active sensors, has become endangered. Active sensors detect things by broadcasting a signal. When this signal bounces off something, the sensor detects the bounce back and knows something is out there. This is the basis of radar, which broadcasts microwaves, and sonar, which broadcasts sound. Because of the signal being broadcast, a passive sensor can detect it.
Passive sensors just listen. Because active sensor signals must reach an object with sufficient energy to bounce something back, a vehicle carrying a passive sensor will detect a vehicle carrying an active sensor first. This is what happens when you use a radar detector in your car to detect police speed trap radars. You usually have time to slow down before your illegal speed is detected by the police radar. As users of these devices well know, there is constant competition to come up with better radars and countermeasures. Passive sensors are the hot item in research and development these days and for obvious reasons. Passive sensors are nearly impossible to detect. Passive sensors can also pick a wide variety of signals. Infrared sensors can detect heat, including something as faint as body heat or the hot skin of an approaching jet aircraft.