amardeep mishra
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@The Deterrent
@Oscar
We all very well know the importance of INS+GPS package for guidance of missiles.I will begin my analysis from briefly describing the INS+GPS and then eventually building on TERCOM and DASMAC guidance schemes. I have certain reservations regarding pakistani access to accurate maps- but i am guessing china would provide these to pakistan?
There are Two GPS/INS integration approaches commonly used. These are
(a) the tightly coupled integration approach, which yields higher accuracies; and
(b)the loosely coupled integration approach used for short time and/or ranges,yielding lower accuracies
Normally the GPS receiver of the missile is interfaced with
(1)altimeter
(2)flight control system,
(3)the INS’s serial/digital interface,
(4) and the carrier aircraft/launching platform
The navigator (i.e., dynamic navigation equations), consisting of a 15-state Kalman filter(in case anyone of you want an elaborate analysis of how KALMAN filters are used to fine tune/filter various sensor outputs,i can provide an indepth analysis as well- for more advanced readers- Amardeep Mishra), is normally updated by the onboard navigation computer every 50 milliseconds (or a 20-Hz rate),while the GPS is updated at1-Hz rate.The GPS will normally consist of a 8-state Kalman filter,so that both the INS and GPS Kalman filters operate in a cascaded mode.Inertial aiding provided to the GPS receiver- tracking loop is at a 10-Hz rate. (Note that the INS is of the strap down class. Thus,the basic strap-down INS algorithms that maintain the body-to-level-axis transformation matrix and transform the body-axis velocity increments to a locally level coordinate frame can be performed at a rate of 50 Hz, while the basic INS algorithms can be performed at an iteration rate of 10 Hz.).
A significant characteristic of the ALCM is the high accuracy at long missile ranges provided by its terrain correlation updated navigation system. In order to implement a terrain correlation updated navigation system, reference terrain elevations must be stored in the missile’s computer prior to launch.This elevation data must be gathered, stored in ground computers, precisely selected for each mission, stored in the carrier aircraft, and transmitted to the missile prior to launch. More specifically, the missile’s navigation and guidance unit uses a terrain contour matching (TERCOM) system that periodically updates the missile’s inertial navigation system by comparing terrain over which the missile flies with stored mapping data.
Now here is the trouble,where does pakistan sources,such an "elevation data"?In USA's case,this data is collected by Defense Mapping Agency-Aerospace Center (DMAAC).In india's case this data is gathered by most probably the RISATs in orbit(more preferabbly by RISAT-2 that has an x-band AESA SAR that can map very very accurately)
The above figure shows visually the steps involved in planning a test mission from launch
point (Point 0) to the target (Point 6). The planner first selects a path from launch to the target in the horizontal plane that passes through the required maps (maps 1 and 3, in the example). In the horizontal plane selection, the mission planner takes into account the terrain over which the missile will fly,special test objectives,and distance between maps. The mission planner has two ALCM simulation tools (or modules) available to aid him in planning missions. These are
(a) the clobber analysis module
(CAM), and
(b) the navigation accuracy module (NAM)
Both these programs reside in a ground-based computer. CAM provides the capability to the mission planner to compute either probability of ground clobber given a specified ground clearance, or ground clearance given a specified probability of clobber. CAM can operate in a rapid mode or a slower mode that provides more detailed results. NAM predicts accuracy and map crossing probabilities along the route of the mission from launch to target. Each of the horizontal maneuvers or any missile mode or speed change requires a missile waypoint. A waypoint is defined as an action point.
The vertical profile is then selected. Here again, a waypoint is needed for each vertical change either in terrain following or barometric hold. Once the mission is selected and all way point and maps defined,the defined mission is inputed to the mission data preparation system
@Oscar
We all very well know the importance of INS+GPS package for guidance of missiles.I will begin my analysis from briefly describing the INS+GPS and then eventually building on TERCOM and DASMAC guidance schemes. I have certain reservations regarding pakistani access to accurate maps- but i am guessing china would provide these to pakistan?
There are Two GPS/INS integration approaches commonly used. These are
(a) the tightly coupled integration approach, which yields higher accuracies; and
(b)the loosely coupled integration approach used for short time and/or ranges,yielding lower accuracies
Normally the GPS receiver of the missile is interfaced with
(1)altimeter
(2)flight control system,
(3)the INS’s serial/digital interface,
(4) and the carrier aircraft/launching platform
The navigator (i.e., dynamic navigation equations), consisting of a 15-state Kalman filter(in case anyone of you want an elaborate analysis of how KALMAN filters are used to fine tune/filter various sensor outputs,i can provide an indepth analysis as well- for more advanced readers- Amardeep Mishra), is normally updated by the onboard navigation computer every 50 milliseconds (or a 20-Hz rate),while the GPS is updated at1-Hz rate.The GPS will normally consist of a 8-state Kalman filter,so that both the INS and GPS Kalman filters operate in a cascaded mode.Inertial aiding provided to the GPS receiver- tracking loop is at a 10-Hz rate. (Note that the INS is of the strap down class. Thus,the basic strap-down INS algorithms that maintain the body-to-level-axis transformation matrix and transform the body-axis velocity increments to a locally level coordinate frame can be performed at a rate of 50 Hz, while the basic INS algorithms can be performed at an iteration rate of 10 Hz.).
A significant characteristic of the ALCM is the high accuracy at long missile ranges provided by its terrain correlation updated navigation system. In order to implement a terrain correlation updated navigation system, reference terrain elevations must be stored in the missile’s computer prior to launch.This elevation data must be gathered, stored in ground computers, precisely selected for each mission, stored in the carrier aircraft, and transmitted to the missile prior to launch. More specifically, the missile’s navigation and guidance unit uses a terrain contour matching (TERCOM) system that periodically updates the missile’s inertial navigation system by comparing terrain over which the missile flies with stored mapping data.
Now here is the trouble,where does pakistan sources,such an "elevation data"?In USA's case,this data is collected by Defense Mapping Agency-Aerospace Center (DMAAC).In india's case this data is gathered by most probably the RISATs in orbit(more preferabbly by RISAT-2 that has an x-band AESA SAR that can map very very accurately)
The above figure shows visually the steps involved in planning a test mission from launch
point (Point 0) to the target (Point 6). The planner first selects a path from launch to the target in the horizontal plane that passes through the required maps (maps 1 and 3, in the example). In the horizontal plane selection, the mission planner takes into account the terrain over which the missile will fly,special test objectives,and distance between maps. The mission planner has two ALCM simulation tools (or modules) available to aid him in planning missions. These are
(a) the clobber analysis module
(CAM), and
(b) the navigation accuracy module (NAM)
Both these programs reside in a ground-based computer. CAM provides the capability to the mission planner to compute either probability of ground clobber given a specified ground clearance, or ground clearance given a specified probability of clobber. CAM can operate in a rapid mode or a slower mode that provides more detailed results. NAM predicts accuracy and map crossing probabilities along the route of the mission from launch to target. Each of the horizontal maneuvers or any missile mode or speed change requires a missile waypoint. A waypoint is defined as an action point.
The vertical profile is then selected. Here again, a waypoint is needed for each vertical change either in terrain following or barometric hold. Once the mission is selected and all way point and maps defined,the defined mission is inputed to the mission data preparation system
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