Missile Guidance by GPS

8/13/2019 Missile Guidance by GPS

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2/20/2014





INTRODUCTION:

1) Introduction to missile guidance :Guidedmissile systems have evolved at atremendous rate over the past four decades,

and recent break through in technologyensure that smart warheads will have anincreasing role in maintaining our militarysuperiority . Innocent civilians are notharmed by misfire.

2) Concept of missile guidance :Missileguidance concerns the method by which themissile receives its commands to move



along a certain path to reach a target. Onsome missiles, these commands aregenerated internally by the missile

computer autopilot. On others, thecommands are transmitted to the missileby some external source. The missile sensoror seeker , on the other hand , is acomponent within a missile that generatesdata fed into the missile computer. This datais processed by the computer and used togenerateguidance commands.





TYPES OF MISSILE GUIDANCE:

Radar signal

Wires

Lasers

Most recently GPS.



Missile guidance using

radar signal : Many machines used in battle, such as tanks,planes , etc. and targets, such as buildings,hangers , launch pads , etc. have a specificsignature when a radar wave is reflected off

of it. Guided missiles that use radar signatures

to acquire their targets are programmed with

the specific signature to home in on. Oncethe missile is launched, it then uses itsonboard navigational array to home in

on the preprogrammed radar signature.



The major problem with these missiles intoday’s battlefield is that the

countermeasures used against these missileswork on the same principles that thesemissiles operate under. The countermeasureshome in on the radar signal source and

destroy the antenna array, which essentialshuts down the radar source, and hence theradar guided missiles cannot acquire theirtargets.



INTRODUCTION TO GPS :

GPS, which stands for Global PositioningSystem, is the only system today able toshow us our exact position on the Earthanytime, in any weather, anywhere. GPSsatellites, 24 in all, orbit at 11,000 nauticalmiles above the Earth. Ground stations

located worldwide continuously monitorthem. The satellites transmit signals that canbe detected by anyone with a GPS receiver.

Using



Elements of GPS :

GPS has three parts: the space segment, theuser segment, and the control segment. Thespace

segment consists of a constellation of 24satellites plus some spares, each in its ownorbit 11,000 nautical miles above Earth. The

user segment consists of receivers, which wecan hold in our hand or mount in a vehicle.The control segment consist, of ground

stations that make sure the satellites areworkin ro erl .





WORKING OF GPS:

1.) Technique called differential correction can yieldaccuracies within 1 -5 meters, or even better, withadvanced equipment.

2.) Differential correction requires a second GPS receiver,a base station, collecting data at a stationary position on aprecisely known point (typically it is a surveyedbenchmark).

3.) Because physical location of base station is known, acorrection factor can be computed by comparing knownlocation with GPS location determined by using satellites.



SATELLITE GUIDED WEAPONS:

The problem of poor visibility does not affectsatellite-guided weapons such as JDAM(Joint Direct Attack Munitions) , which usessatellite navigation systems, specifically theGPS system. This offers improved accuracycompared to laser systems , and can operate

in all weather conditions, without any needfor ground support. Because it is possible to

jam GPS, the bomb reverts to inertialnavigation in the event of losing the GPSsignal. Inertial navigation is significantly



MISSILE GUIDANCE USING GPS:

The central idea behind the design ofDGPS/GPS/inertial guided weapons is that ofusing a 3-axis gyro/accelerometer package asan inertial reference for the weapon'sautopilot, and correcting the accumulateddrift error in the inertial package by using

GPS PPS/P-code. Such weapons aredesignated as "accurate" munitions as theywill offer CEPs (Circular Error Probable) of theorder of the accuracy of GPS P -codesignals, typically about 40ft.



The next incremental step is then to updatethe weapon before launch with a DGPSderived position estimate, which will allow itto correct its GPS error as it flies to thetarget, such weapons are designated"precise" and will offer accuracies greater

than laser or TV guided weapons, potentiallyCEPs of several feet .For an aircraft tosupport such munitions , it will require aDGPS receiver, a GPS receiver and interfaceson its multiple ejector racks or pylons to



APPLICATIONS OF GPS:

1.) Navigation System Timing and Ranging(NAVSTAR) GPS is now available at any time ,in any weather, and at any place on orabove the earth. NAVSTAR also providesprecise time within a millionth of a second tosynchronize the atomic clocks used in

various military applications. 2.) GPS is even used in locating the present

position of living and non living things, this is

the concept which is used in famous“GOOGLE EARTH”.



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Missile Guidance by GPS

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