faubert@cs.mcgill.ca (David FAUBERT) (01/22/91)
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.
denbeste@uunet.UU.NET (Steven Den Beste) (01/24/91)
From: etnibsd!denbeste@uunet.UU.NET (Steven Den Beste) In article <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. Cruise missile guidance works by recognition of ground features. Programmed into its guidance system are topological maps of one or more areas over which it will pass. After a couple hundred miles, it enters a square which it knows. Its radar then compares where it is (by matching the shape of the ground against its on-board model) to where it is supposed to be and corrects its course accordingly. It then flies blind until it reaches the next area it knows. There are good sides and bad sides to this design. The missile isn't depending on any outside control (including sattelites) so it should be largely immune to ECM. Its radar is pointed down (to see the ground) and is off most of the time anyway (when between squares) so it doesn't give itself away. On the other hand, it requires distinctive geology to fly over so that it can recognize terrain features to adjust its course. That means that there are large areas of the Soviet Union which couldn't be reached via strategic-range cruise missiles because the local geology is simply flat, or rolling hills. That`s why, back in the good old days of the Cold War, cruise missiles were not a replacement for ballistic missiles. It also implies that a substantial amount of effort is required to program a cruise missile. We're talking weeks, not hours. There simply isn't any good way to spontaneously retarget a cruise missile to respond to changing conditions - unless you've captured and stored an appropriate model of the entire grand-tactical battlefield, which we seem to have done in the case of Iraq between September and now. The word in Newsweek this week was that General Schwarzkopf (sp?) insisted on them doing this - and now it is paying off in spades.
carlo@gaia.gcs.oz.au (Carlo Kopp) (01/27/91)
From: Carlo Kopp <carlo@gaia.gcs.oz.au> 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
rqdms@lims01.lerc.nasa.gov (Dennis Stockert) (02/04/91)
From: rqdms@lims01.lerc.nasa.gov (Dennis Stockert) In article <1991Jan22.022338.22603@cbnews.att.com>, faubert@cs.mcgill.ca (David FAUBERT) writes... > > 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. This was just discussed in this group not long ago. The Tomahawk uses a guidance system called TERCOM (TERrain COntour Matching) which compares the topography of the terrain over which it's flying to digital maps stored in the on-board computers. It does this comparison periodically as it progresses along its flight path, and makes necessary guidance corrections accordingly. *********************************************************************** * Dennis Stockert * Life is what happens to you while * * rqdms@lims01.lerc.nasa.gov * you're planning other things - Mom * *********************************************************************** * No one that knows me would mistake my opinions for those of * * any respectable organization * ***********************************************************************