difference between active and passive satellite in wikipedia
Communications satellite There are two major classes of communications satellites, passive and active. Passive satellites only reflect the signal coming from the source, toward the direction of the receiver. With passive satellites, the reflected signal is not amplified at the satellite, and only a very small amount of the transmitted energy actually reaches the receiver. Since the satellite is so far above Earth, the radio signal is attenuated due to free-space path loss, so the signal received on Earth is very, very weak. Active satellites, on the other hand, amplify the received signal before retransmitting it to the receiver on the ground.[3] Passive satellites were the first communications satellites, but are little used now. Telstar was the second active, direct relay communications satellite. Belonging to AT&T as part of a multi-national agreement between AT&T, Bell Telephone Laboratories, NASA, the British General Post Office, and the French National PTT (Post Office) to develop satellite communications, it was launched by NASA from Cape Canaveral on July 10, 1962, in the first privately sponsored space launch. Relay 1 was launched on December 13, 1962, and it became the first satellite to transmit across the Pacific Ocean on November 22, 1963.[8]
Passive immunity An individual's immune response of passive immunity is "faster than a vaccine" and can instill immunity in an individual that does not "respond to immunization", often within hours or a few days. Another advantage to passive immunity is that maternal antibodies that are passed to the newborn during nursing boosts the newborn's immune system having lasting effects on the baby's health such as decreased risk of obesity.[17][24]