The document summarizes the key functions of the telemetry, tracking and command (TT&C) subsystem of a satellite. It discusses how TT&C provides vital communication between the satellite and ground stations by (1) monitoring the satellite's status and measurements through telemetry, (2) sending commands from the ground to control satellite functions, and (3) tracking the satellite's location through antenna positioning and Doppler effect measurements. The TT&C subsystem receives commands from and provides data to the satellite's command and data handling system and performs autonomous operations like antenna pointing and fault recovery.

1. ELECTRONIC AND CONTROL
LOGIC
BY: ROSHAN LAL KUMAWAT

2. Contd…
1. Brain of the nanosatellite
2. Maintains the function of the satellite
3. Processes the command or instruction given by
ground management system
4. Provides proper command to the required
subsystem

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Transmission
Polarization
Low Noise conveter
Reception
Tuner
Operation of satellite

5. How SatellitesWork
1. A Earth Station sends
message in GHz range.
(Uplink)
2. Satellite Receive and
retransmit signals back.
(Downlink)
3. Other Earth Stations receive
message in useful strength
area. (Footprint)

6. Telemetry Tracking
& Command SERVICES

7. Introduction
The telemetry, tracking and control subsystem
provides vital communication to and from the
satellite
TT&C is the only way to observe and to control the
satellite’s functions and condition from the ground

8. TELEMETRY
Telemetry - one direction ( Satellite to ground )
Monitor the satellite through status reports &
anomalies.
Telemetry - set of measurements taken on board the
satellite and then sent to the operations control Centre.
Measurements concern magnitudes - temperatures,
voltages, currents etc.

9. COMMAND
1. Command In the other direction (ground to satellite)
2. Used either for routine programming or for sending
commands to carry out specific actions to handle
events.
3. Although modern satellites operate automatically, they
still need to receive commands from the ground.
4. If the solar arrays have been automatically deployed,
commands sent by the control centre switch on the
equipment that was off during the launch: recorders,
payloads and passengers if any.

10. TRACKINGThe same link is used for tracking. This term describes
measurements taken to accurately locate the orbiting
satellite (orbit determination);.
This involves:
Measuring the time taken by RF signals for the round
trip journey (station - satellite- station
Measuring, based on the Doppler effect, the frequency
shift due to satellite velocity - calculate satellite range
rate.
Measuring antenna orientation with respect to the north
(azimuth) and the horizon (elevation).

11. TT&CFunctions

12. 1. Measuring of angle and range for the localization
of the satellite.
2. Transmission of housekeeping information.
3. Status of a satellite to the ground control station.
4. Receiving command signals for the station
keeping operations of the on-board equipments.

14. CarrierTracking
1. Two-way coherent communication
2. Transmitter phase-locks to the received
frequency
3. Transmitted frequency is a specific ratio of
the uplink frequency
4. Easy to find and measure the frequency
received on the ground
5. Doppler shift provides range rate

15. SubsystemOperations
1. Receive commands from Command and Data
Handling subsystem
2. Provide health and status data to CD&H
3. Perform antenna pointing
4. Perform mission sequence operations per stored
software sequence
5. Autonomously select Omni-antenna when spacecraft
attitude is lost
6. Autonomously detect faults and recover
communications using stored software sequence

16. CommandSystem
Reconfigures satellite or subsystems in
response to radio signals from the ground
Command timing
Immediate
Delayed
Priority driven (ASAP)

17. Typical tracking, telemetry, command and monitoring system.

18. SatelliteCommandSystemBlockDiagram

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