satellite.ppt
TRANSCRIPT
FUNCTIONAL BLOCKS OF SATELLITE COMMUNICATIONVishal Patil Milind Vaidya
POWER SUBSYSTEM:(MATERIALS USED)
●SOLAR CELL:●It Converts light (Sun Light) into Electricity.
Features :●They have less efficiency about 10%.●It requires continuous sunlight for the generation of power.
Main use:●It provides DC power and regulated secondary supply voltages for satellites● voltages range 5v to 15v.
SOLAR ECLIPSE CONDITION FOR SATELLITES:
●What is solar eclipse?
●Eclipse condition :The sun light gets cut off and the solar cell power gets cut.
● Then during this period of time Back up batteries are used to generate power at that time.
●Hence storage battery must be capable of providing continues power for more than 12 hours.
●Amplifiers and DC to DC convertors are required.
TELEMETRY TRACKING & COMMAND(TT&C)
●The Telemetry, Tracking and Command subsystem provides vital communication to and from the spacecraft & allows to manage or monitor satellites from ground ●They use entirely different communication channel. ●They consist of various sensors for various parameters
TT&C FROM GROUND STATION
TELEMETRY SUBSYSTEM 1.Sensors & Transducers measures……●Internal voltage ,Currents ,Temperature●Fuel level, Pressure, Power supply●Positional & orientation information●Environmental information magnetic field
radiation
2.Telemetry Encoder Multiplexes various analog & digital information
& modulate before transmission
3.Transmitter It will transmit modulated information through
Telemetry antenna (Omni-directional)
SATELLITE TRACKING SYSTEM
●It uses frequency scanning effect●satellite signals transmitted from a satellite via an antenna mounted on a moving body are analyzed to acquire a position of the satellite●the acquired position of the satellite is continuously tracked, thereby smoothly receiving the satellites signals
COMMAND
●Receiver : Demodulation
● Command decoder: decodes the encoded command signals with special techniques for security & convert it to appropriate pulses
●Driver amplifier: Amplification Then these signal used by satellite for execution
COMMUNICATION CHANNEL SUBSYSTEM:
●Satellites are build to communicate.
●A transponder is used in satellites before transmitting the signal to earth station.
●Transponder: An automatic device that receives, amplifies, and re-transmits a received signal on a different frequency.
TRANSPONDER TRANSPONDER CONSIST OF….
●Filter●Low Noise Amplifier (LNA)●Band pass filter●Mixer plus Local Oscillator●Another Band pass filter and●Power amplifier.
BLOCK DIAGRAM OF TRANSPONDER: Power amplifiers like TWT are used for generating the required
●It Provides necessary gain & output power required for transmitting back to earth station.
●Advantages (TWT):●High gain ●High efficiency●Light weight●Reliable and consistent.
●In the recent years TWT have been replaced by Solid Power Amplifier.
●Multiple channels are used for greater reliability.
●Now days advance transponders demodulate and re-modulate with another using another specific modulation
ATTITUDE CONTROL SUBSYSTEM:
●Satellite attitude is the orientation of satellite with respect to earth.
●Attitude control sub-system provides stabilization in orbit and senses the change in orientation of satellite.
●With built in jet thruster it makes the necessary corections to the altitude of satellite.
●When this subsystem senses the change In position of satellite from the desired position it receives the command and control system and that fires the appropriate thruster at proper time.