http://www.navsource.org/archives/01/57s1.htm
TASM
In November 1972 design began for the Tomahawk anti-ship missile.
It carried the same 1,000-pound high-explosive semi-armor-piercing warhead as the conventional land-attack Tomahawk.
It could penetrate a submarine's pressure hull or a large warship's hull plating.
Originally it was planned for a range of 140 nautical miles, which was adequate for underwater launch, since submarines find targets by sonar and are invulnerable to hostile cruise missiles during approach to target.
Surface warships needed a longer-range weapon to attack Soviet warships, which could fire their anti-ship missiles from 250 nautical miles.
Surface search radars cannot be used for long-range anti-ship targeting (over-the-horizon targeting) because of their inherent horizon-limited range, about 2—50 miles.
The challenge was not to build a 250-nautical-mile-range missile but to plan a targeting system for it.
Critics doubted that a task group would fire weapons over the horizon at targets that task group sensors could not locate, since the probability of missing the targets would seem to be high, making an over-the-horizon attack an act of unilateral disarmament.
The same critics accepted that the large Soviet anti-ship cruise missiles were threats from 250 nautical miles' range. Rear Admiral Walter Locke, the cruise missile project officer, asked the John Hopkins University Applied Physics Laboratory and the Harpoon seeker contractor, McDonnell Douglas, to investigate whether a Tomahawk could search for a target inside an area of uncertainty. emphasis mine
Replacing the Tomahawk anti-ship missile turbojet with the costlier land-attack Tomahawk turbofan engine could increase TASM range to over 300 nautical miles to allow the missile to fly search patterns. In 1975 the applied Physics Laboratory developed search patterns so that the Tomahawk anti-ship missile was capable of autonomous scouting and strike missions.
The next problem was how to get surveillance information to the launching ship for over-the-horizon targeting.
Opponents within OSD refused to authorize funds for research into over-the-horizon targeting, but the Naval Electronics Systems Command funded an experiment called Outlaw Shark.
For this experiment, a computer database was set up at the Submarine Operational Command Center in Naples, Italy and another computer was installed aboard a submarine.
The Naples Outlaw Shark system copied operational intelligence data being collected for later transmission to a Sixth Fleet aircraft carrier, condensed the data and relayed it without delay to the submarine over a computer-to-computer encrypted radio data link. Outlaw Shark, gotta love the Navy's names
Sometimes the submarine received intelligence data only six minutes after the occurrence of the event being described. The submarine's computer correlated the intelligence data with its own contact data and prepared search patterns adequate for an immediate Tomahawk anti-ship attack.
In December 1976 the submarine used this system to generate search patterns for actual ships not held by its own sensors.
Analyses showed that the search patterns would result in Tomahawk hits on those ships.
The first test of a Tomahawk anti-ship missile was a launch at a target hulk 224 nautical miles away.
The Tomahawk flew 175 nautical miles to the target and began searching.
It then flew 173 nautical miles in search patterns and found the target.
This was the first long-range anti-ship cruise missile flight not to use a data link between the missile and a controller.
Tomahawk anti-ship missiles became operational in 1982.
In contrast to the procedure for early Tomahawk land-attack missiles, for the anti-ship mission the ship controlled all targeting and planned the entire strike mission.
Tomahawk weapons control systems were SWG-2 for armoured box launchers and SWG-3 for vertical launch systems.
Each provided track – and launch control functions.
The ship used the launch-control group to track the status of the Tomahawk missiles and to fire them.
The Tomahawk anti-ship missile used the Harpoon active radar guidance section with a passive seeker for identification and direction finding.
The missile classified and prioritized targets to attack the most valuable target.
As with Harpoon, Tomahawk anti-ship missiles could fly dogleg courses so that they could attack from unexpected directions and in such a way that missiles from one or more ships arrived on target simultaneously.
The ship kept a database of surface ships in her assigned patrol area on the track-control group computer.
In the initial Tomahawk weapons control system, each ship kept her own track database.
With newer versions, one ship was the force over-the-horizon track coordinator (FOTC) for a task group.
Track data came from the ship's own sensors, NTDS data links and intelligence sources.
General surveillance information came from surveillance satellites and aircraft, from SOSUS and from shore-based (Outboard) radio direction finding.
Each ship's Tomahawk weapon control system was linked to tactical information exchange satellite radio broadcasts (TADIXS and OTCIXS) over the ship's radios.
A newer system, JOTS, recorded data from OTCIXS and TADIXS broadcasts and maintained a local picture as seen by off-ship sensors.
JOTS used commercial computers and was entirely passive.
The ship could get into Tomahawk range without revealing her presence to the target.
A Tomahawk anti-ship missile could be fired as a "wake-up call" or "screaming meemie" towards a radio-silent enemy battle group.
It the enemy ships would switch on their radars to target the actively searching Tomahawk, a follow-on strike could exploit the newly available locating information.
Spruance class destroyers and Ticonderoga class cruisers can use their long-range passive towed-array sonar to locate targets over the horizon.
Submarines have long used the same tactic.
