Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rutgers!att!cbnews!cbnews!military From: carlo@gaia.gcs.oz.au (Carlo Kopp) Newsgroups: sci.military Subject: Re: Tomahawk Guidance Message-ID: <1991Jan27.101839.23986@cbnews.att.com> Date: 27 Jan 91 10:18:39 GMT References: <1991Jan22.022338.22603@cbnews.att.com> Sender: military@cbnews.att.com (William B. Thacker) Organization: AT&T Bell Laboratories Lines: 51 Approved: military@att.att.com From: Carlo Kopp In <1991Jan22.022338.22603@cbnews.att.com> faubert@cs.mcgill.ca (David FAUBERT) writes: >From: faubert@cs.mcgill.ca (David FAUBERT) > Does anyone know about the oft mentioned Tomahawk's guidance >system? I have heard that inertial guidance systems are not used, as >they are not accurate enough over very long ranges. If the guidance is >not inertial, what is it? Also, what kind of target recognition, if any, >is employed by the missile while in flight. Any information would be >appreciated. The AGM/BGM-109 Tomahawk series missiles employ either two or three guidance elements. Midcourse guidance is provided by a precision inertial system, which is periodically updated by TERCOM (TERrain COntour Matching) navigation equipment. TERCOM will take a series of radar altimeter readings and store a profile of the terrain under the missile. This profile is then matched against a stored map of a given area, a clever algorithm is used to determine the vehicle's position. The position information is then used to update the inertial system. As a result, the cruise missile will spend most of its time flying on inertial guidance and it will only do updates in preprogrammed areas. Using this technique, it is not necessary to map the whole of the enemy's landmass, as all that is required are maps along favourable approach routes. As the missile approaches the target, the resolution of the programmed grids is increased, so that the accuracy of the missile increases. Some Tomahawks are also equipped with the third guidance element, the DSMAC (digital scene matching area correlator) which uses a nose camera to look at the terrain beneath the missile and compares this with a stored image presumably acquired by satellite recce. DSMAC equipped Tomahawks are reportedly accurate to a CEP of the order of tens of feet. There have been some suggestions that the Tomahawks may also be fitted with GPS satnav to supplement the TERCOM equipment, does anybody out there have any details ? From: Carlo Kopp, Defence Writer for Australian Aviation journal Melbourne, Australia