• (i) Sputnik 1 – First artificial satellite: Correct. Launched by the Soviet Union on October 4, 1957, it marked the beginning of the Space Age. It was a polished metal sphere with four external radio antennas to broadcast radio pulses.
(ii) Luna 2 – First satellite for commercial purpose: Incorrect. Luna 2 (1959) was actually the first spacecraft to reach the surface of the Moon (it was a lunar impactor). The first commercial communication satellite was Telstar 1, launched in 1962.
(iii) Explorer 1 – First satellite launched by the US: Correct. Following the success of Sputnik, the United States launched Explorer 1 on January 31, 1958. It is famous for discovering the Van Allen radiation belts.
(iv) Vanguard 1 – Oldest human-made object still in orbit: Correct. Launched in March 1958, it was the first solar-powered satellite. While communication with it was lost in 1964, it remains the oldest piece of space junk still circling the Earth.
