21-08-2013, 04:36 PM
Seminar Report ’03 SATRACK
[attachment=57333]
INTRODUCTION
According to the dictionary guidance is the ‘process of guiding the path of an object towards a given point, which in general may be moving’. The process of guidance is based on the position and velocity if the target relative to the guided object. The present day ballistic missiles are all guided using the global positioning system or GPS.GPS uses satellites as instruments for sending signals to the missile during flight and to guide it to the target. SATRACK is a system that was developed to provide an evaluation methodology for the guidance system of the ballistic missiles. This was developed as a comprehensive test and evaluation program to validate the integrated weapons system design for nuclear powered submarines launched ballistic missiles.this is based on the tracking signals received at the missile from the GPS satellites. SATRACK has the ability to receive record, rebroadcast and track the satellite signals. SATRACK facility also has the great advantage that the whole data obtained from the test flights can be used to obtain a guidance error model. The recorded data along with the simulation data from the models can produce a comprehensive guidance error model. This will result in the solution that is the best flight path for the missile.
GPS SIGNALS
The signals for the GPS satellite navigation are two L-band frequency signals. They can be called L1 and L2.L1 is at 1575.42 MHz and L2 at 1227.60 MHz.The modulations used for these GPS signals are
1. Narrow band clear/acquisition code with 2MHz bandwidth.
2. Wide band encrypted P code with 20MHz bandwidth.
L1 is modulated using the narrow band C/A code only. This signal will give an accuracy of close to a 100m only. L2 is modulated using the P code. This code gives a higher accuracy close to 10m that is why they are encrypted. The parameters that a GPS signal carries are latitude, longitude, altitude and time. The modulations applied to each frequency provide the basis for epoch measurements used to determine the distances to each satellite. Tracking of the dual frequency GPS signals provides a way to correct measurements from the effect of refraction through the ionosphere. An alternate frequency L3 at 1381.05MHz was also used to compensate for the ionospheric effects.
SATRACK CONCEPT
Guidance system evaluation concept of very early weapons systems depended on the impact scoring techniques. This means that the missile was shot and the accuracy was formulated on the scoring or the target destruction. This evaluation method was unacceptable for evaluating the more precise requirements of the latest systems. A new methodology was needed that provided insights into the major error contributors within the flight-test environment. The existing range instrumentation was largely provided by radar systems. they however did not provide the needed accuracy or range in the broad ocean test ranges. The accuracy projections needed to be based on the high confidence understanding of the underlying system parameters. SATRACK was developed with the necessary hardware and telemetry stations.
GPS TRANSLATOR
This flight hardware is fixed in the missile. The translator receives the GPS signals and they are amplified, shifted to an intermediate frequency, filtered to cover the satellite signal modulation bandwidth, shifted to an output frequency. Then they are amplified for transmission to one or more ground stations.
FIELD SUPPORT EQUIPMENT
SATRACK is the most useful tool because of its post flight processing facility .The ground equipment consists of receiving antenna, data recorder and auxiliary reference timing systems. The equipment receives the translated GPS signal along with other telemetry signals and distributes it to the data recorder. Most ground stations are capable of generating a precise atomic timing standard. The earlier equipments were narrowband recorders that relied on high-speed tape recorders. These gave up to 14 tracks of recording channels with four mega samples per second.
PORTABLE GROUND EQUIPMENT
This hardware is used for the post flight processing and tracking of the satellite signals. The SATRACK facility processes the raw data into a time series of range and Doppler measurements for each satellite, and the Kalman filter, which incorporates various corrections and generates a navigation solution for the missile. The system has undergone a lot of redesign and development as the requirements evolved with new type of translators and receivers. The latest system processes the wideband L1/L2 signals dual frequency P-code as required by wide band translators. The system hardware is based on Analog Device SHARC processor. Most of the custom GPS processing hardware is based on field programmable gate arrays [FPGA]. Each board has the ability to track up to eight channels. The user interface is done using windows based PC workstations.
CONCLUSION
SATRACK is a significant contributor to the successful development of and operational success of the trident weapons system. It provides a unique monitoring function that is critical to the maintenance of strategic weapons systems. The development and research leading up to this technology has been instrumental in bringing out the latest in GPS receiver, translators, data recorders etc.several special test have been conducted with various combinations of inertial systems, GPS receivers, translators as well as RF/antenna designs. Special tests have demonstrated that accuracy a be achieved to support potential new and extremely demanding tactical strike scenarios. The development of SATRACK looks forward to the implementation of the Low Cost Missile Test Kit. [LCTMK]. one other main development from this technology was the development of sophisticated tools for optimal target patterning. Instrumentation, analytic methods, and modelling and the use of limited and expensive flight tests assets were also born out of the SATRACK research.
[attachment=57333]
INTRODUCTION
According to the dictionary guidance is the ‘process of guiding the path of an object towards a given point, which in general may be moving’. The process of guidance is based on the position and velocity if the target relative to the guided object. The present day ballistic missiles are all guided using the global positioning system or GPS.GPS uses satellites as instruments for sending signals to the missile during flight and to guide it to the target. SATRACK is a system that was developed to provide an evaluation methodology for the guidance system of the ballistic missiles. This was developed as a comprehensive test and evaluation program to validate the integrated weapons system design for nuclear powered submarines launched ballistic missiles.this is based on the tracking signals received at the missile from the GPS satellites. SATRACK has the ability to receive record, rebroadcast and track the satellite signals. SATRACK facility also has the great advantage that the whole data obtained from the test flights can be used to obtain a guidance error model. The recorded data along with the simulation data from the models can produce a comprehensive guidance error model. This will result in the solution that is the best flight path for the missile.
GPS SIGNALS
The signals for the GPS satellite navigation are two L-band frequency signals. They can be called L1 and L2.L1 is at 1575.42 MHz and L2 at 1227.60 MHz.The modulations used for these GPS signals are
1. Narrow band clear/acquisition code with 2MHz bandwidth.
2. Wide band encrypted P code with 20MHz bandwidth.
L1 is modulated using the narrow band C/A code only. This signal will give an accuracy of close to a 100m only. L2 is modulated using the P code. This code gives a higher accuracy close to 10m that is why they are encrypted. The parameters that a GPS signal carries are latitude, longitude, altitude and time. The modulations applied to each frequency provide the basis for epoch measurements used to determine the distances to each satellite. Tracking of the dual frequency GPS signals provides a way to correct measurements from the effect of refraction through the ionosphere. An alternate frequency L3 at 1381.05MHz was also used to compensate for the ionospheric effects.
SATRACK CONCEPT
Guidance system evaluation concept of very early weapons systems depended on the impact scoring techniques. This means that the missile was shot and the accuracy was formulated on the scoring or the target destruction. This evaluation method was unacceptable for evaluating the more precise requirements of the latest systems. A new methodology was needed that provided insights into the major error contributors within the flight-test environment. The existing range instrumentation was largely provided by radar systems. they however did not provide the needed accuracy or range in the broad ocean test ranges. The accuracy projections needed to be based on the high confidence understanding of the underlying system parameters. SATRACK was developed with the necessary hardware and telemetry stations.
GPS TRANSLATOR
This flight hardware is fixed in the missile. The translator receives the GPS signals and they are amplified, shifted to an intermediate frequency, filtered to cover the satellite signal modulation bandwidth, shifted to an output frequency. Then they are amplified for transmission to one or more ground stations.
FIELD SUPPORT EQUIPMENT
SATRACK is the most useful tool because of its post flight processing facility .The ground equipment consists of receiving antenna, data recorder and auxiliary reference timing systems. The equipment receives the translated GPS signal along with other telemetry signals and distributes it to the data recorder. Most ground stations are capable of generating a precise atomic timing standard. The earlier equipments were narrowband recorders that relied on high-speed tape recorders. These gave up to 14 tracks of recording channels with four mega samples per second.
PORTABLE GROUND EQUIPMENT
This hardware is used for the post flight processing and tracking of the satellite signals. The SATRACK facility processes the raw data into a time series of range and Doppler measurements for each satellite, and the Kalman filter, which incorporates various corrections and generates a navigation solution for the missile. The system has undergone a lot of redesign and development as the requirements evolved with new type of translators and receivers. The latest system processes the wideband L1/L2 signals dual frequency P-code as required by wide band translators. The system hardware is based on Analog Device SHARC processor. Most of the custom GPS processing hardware is based on field programmable gate arrays [FPGA]. Each board has the ability to track up to eight channels. The user interface is done using windows based PC workstations.
CONCLUSION
SATRACK is a significant contributor to the successful development of and operational success of the trident weapons system. It provides a unique monitoring function that is critical to the maintenance of strategic weapons systems. The development and research leading up to this technology has been instrumental in bringing out the latest in GPS receiver, translators, data recorders etc.several special test have been conducted with various combinations of inertial systems, GPS receivers, translators as well as RF/antenna designs. Special tests have demonstrated that accuracy a be achieved to support potential new and extremely demanding tactical strike scenarios. The development of SATRACK looks forward to the implementation of the Low Cost Missile Test Kit. [LCTMK]. one other main development from this technology was the development of sophisticated tools for optimal target patterning. Instrumentation, analytic methods, and modelling and the use of limited and expensive flight tests assets were also born out of the SATRACK research.