Previous Year Question
An artificial satellite can be tracked very precisely from the earth by using
Doppler effect
Radar
Sonar
Pulsar
Correct Answer: A
Detailed Solution
When an artificial satellite moves relative to the Earth, the observed frequency of the radio signal received from it changes. This change in frequency caused by relative motion between the source and the observer is called the Doppler Effect.
When the satellite approaches the Earth, the received frequency increases, and when it moves away, the received frequency decreases. By accurately measuring this Doppler shift, the radial velocity of the satellite can be determined.
Continuous Doppler measurements, used along with the orbital parameters of the satellite, allow its position and orbit to be tracked with very high precision.
Historically, scientists also studied the Doppler shift in the radio signals of Sputnik-1 to determine its orbital position.