Space agencies employ a sophisticated system to track and control satellites in orbit, ensuring their proper functioning and adherence to designated orbits. This process involves a combination of ground-based tracking stations, orbital predictions, ground control centers, telemetry, tracking, and command (TT&C), and onboard systems.

Ground-based tracking stations are strategically located around the globe to provide continuous coverage of satellites in orbit. Equipped with radar and radio antennas, these stations communicate with satellites and accurately determine their positions. By tracking the satellite's signals, these stations gather essential data to calculate its orbit.

Two-Line Element Sets (TLEs) are pivotal in this process. TLEs are sets of parameters describing a satellite's orbit, continually updated based on tracking station data. Space agencies employ specialized software to process TLE data, enabling them to predict when a satellite will pass over specific tracking stations. These predictions guide communication and command planning.

Ground control centers serve as mission control hubs. Engineers and operators monitor the satellite's status, health, and overall operations from these centers. They use TLE data to schedule communication windows when the satellite is visible to tracking stations, ensuring efficient data exchange and command transmission.

Telemetry, Tracking, and Command (TT&C) are the core functions of satellite control. Telemetry involves receiving data from the satellite, including information about its status, health, and scientific observations. Tracking stations continuously monitor the satellite's position, sending tracking data back to ground control. Commands are sent from ground stations to the satellite, guiding its operations, and making necessary adjustments.

Onboard systems play a crucial role in satellite autonomy. Satellites are equipped with redundant systems, sensors, and processors to perform tasks without continuous ground intervention. They can adjust their orientation, activate scientific instruments, and manage power usage based on predefined commands and programming.

In conclusion, the tracking and control of satellites in orbit are complex operations that rely on an integrated system of ground-based tracking stations, TLE data, ground control centers, and onboard systems. This infrastructure ensures satellites remain on course, maintain communication, and execute commands, facilitating their missions and contributing to our understanding of space and Earth.