Naval Warfare Beyond Sensor Range

Modern anti-ship missile batteries have ranges far beyond the effective range of their sensor systems. So, forward observer systems and secure, jam proof, real time communications back to forces with these longer range missiles are critical. But, forward observer units can be tiny compared to warships or conventional military aircraft, and aren't necessarily manned.

Visible range from near the surface on a calm sea in perfectly clear conditions is limited to about 26 nautical miles (a.k.a. about 30 ordinary miles which is about 50 kilometers) due to the curvature of the Earth, although it can be longer from higher elevations.

A nautical mile is 1.15 miles which is 1.85 km. 

A knot is 1.15 miles per hour which is 1.85 km/hour. 

The speed of sound (a "Mach") is about 666.7 knots at sea level.

The US military is expanding its inventory of long-range maritime strike missiles such as the Precision Strike Missile (PrSM), Maritime Strike Tomahawk (MST), Standard Missile 6 (SM-6), Long-Range Anti-ship Missile (LRASM), and Naval Strike Missile (NSM). These capable weapons all have ranges well beyond the effective range of the sensor systems organic to their launch platforms – meaning their effective employment relies on third party targeting data.

While these missiles all have terminal seekers for target acquisition and aim point selection, they require target location and identification information from deep-reach external sensor systems for mission planning, missile launch decisions, target location updates to in-flight missiles, and battle damage assessments (BDA).

The threat of long-range (400 km/160 nm), hypersonic, air-to-air missiles such as the PLAAF’s new PL-21 indicate that US conventional reconnaissance and targeting aircraft must now operate within protected airspace limiting their ability to target enemy ships out to the maximum ranges of US anti-ship missiles. As a result, targeting for US long-range anti-ship missiles is increasingly dependent on NRO and Space Force satellite reconnaissance and targeting systems.

A fundamental problem facing the US military is that the services have fielded capable, long-range missile systems, but only possesses limited deep-reach Intelligence, Surveillance, Reconnaissance and Targeting (ISRT) capabilities, limiting the effective employment of long-range missile systems. The National Reconnaissance Office (NRO) and Air Force/Space Force are developing satellite ISRT constellations to address the problem, but the services need to use a ‘Maritime Strike System of Systems’ approach to address the true functionality of US maritime strike capability.

From here.