Introduction GPS signals Modulation Techniques Need of SATRACK SATRACK Measurement Concept GPS Translators SATRACK Configuration Accuracy Evaluation Concept Applications Advantages Disadvantages Conclusion

SATRACK is an evaluation methodology developed for the guidance system of the ballistic missiles.

It is responsible for accuracy evaluation of the Navy’s Strategic Weapon System.

It has the ability to receive ,record and track the satellite signals.

It obtains whole data from the test flights and

gives a guidance error model.

Gives the best flight path for the missile.

Detects small error contributors in

calculating distances.

Contd…Contd…

The signals for the GPS satellite navigation are two L-band frequency signals.

called L1 and L2. L1 operates at 1575.42 MHz. L2 operates at 1227.60 MHz.

Modulation techniques used are: 1. Narrow band clear/acquisition code. 2. Wide band encrypted P code.

L1 is modulated using the narrow band C/A code only.

It gives an accuracy of close to a 100m only.

L2 is modulated using the P code.

It gives an accuracy close to 10m only.

The parameters that a GPS signal carries are latitude,

longitude, altitude and time.

The modulations applied to each frequency gives the

measurements used to determine the distances to each

satellite.

The evaluation concept of very early weapons systems depended on the impact scoring technique.

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.

Contd…Contd… The radar systems did not provided the needed

accuracy or range in the broad ocean test ranges.

A new methodology was needed that provided a much improved flight-test environment.

SATRACK was developed with the necessary hardware and telemetry stations.

Contd…Contd…

The main parts are:

GPS satellites.

missile translator. and ground telemetry stations.

Missile receives the signals from the GPS

satellites.

translated to another frequency and sent to the

ground telemetry stations.

The station records the data for playback and for

post processing.

signals received at the missile are translated to S-

band frequencies using translators.

This hardware is fixed in the missile.

It receives the GPS signals and amplifies it,

shifts to frequency known as

S-band signals.

They are amplified again for transmission to

one or more ground stations.

Two types of GPS Translators :

Analog translators. Digital translators.

Analog translators heterodyne the L-band signal to S-band. Digital translators convert the received L-band signal to a

digital signal and in turn to S-band and transmit it to ground stations.

It is used for the post flight processing and tracking of signals.

The raw data processed are given to Kalman filter which gives navigation solution for missile.

The hardware has undergone lot of redesign due to evolvement of new translators , receivers.

Processes L1/L2 signals.

For a number of days GPS signals are received,

tracked, and recorded at the GPS tracking sites.

During the flight, GPS signals are received , translated

and transmitted to the surface station(s).

A tracking antenna at the station receives the missile

signals, separates the various components and records

the data.

(CONTD)…(CONTD)…

The post-flight process uses the recorded data to give

satellite ephemerides from the post-flight receiver.

After the datas are corrected it is used by the missile

processor to produce the flight test data products.

The data with the processed telemetry data provide the

tracking aids for the post flight receiver and measurement

estimates for the missile processor.

CONTD…CONTD…

Evaluation capability for cumulative flight test accuracy.

It is used in Army and Air Force missile test applications.

It provides a unique monitoring function that is critical to the maintenance of the Navy’s strategic weapon system.

It provides the best flight path for the missile.

The full digital implementation of processing facility leads to big improvement over analog circuitry.

It acquires the signal with no delay.

It can support potential new and extremely demanding tactical strike scenarios.

Large amount of infrastructure is needed to support it.

Implementation of large Kalman filter to process technique

SATRACK is a significant contributor to the operational success of the weapons system.

It provides a monitoring function that is critical to the maintenance of the weapon system.

The development and research has brought the latest in GPS receiver, translators, data recorders.

Many sophisticated tools for optimal striking target were developed.

Special tests have shown that high accuracy can be achieved to support new weapons system.

http://sprg.ssl.berkley.edu/~tohban/satrack.html

http://twitter.com/SatrackGPS

www.wikipedia.co/Satrack.html