Satellite launch comes as Seoul seeks to bolster its ability to monitor nuclear-armed North Korea.
The launch on Saturday came less than two weeks after rival North Korea announced it had successfully launched its own reconnaissance satellite, underscoring the accelerating space race between the neighbours.
South Korea’s satellite, carried by a “KOREA”-emblazoned SpaceX rocket, launched from Vandenberg Space Force Base in California, entered orbit several minutes after launch and succeeded in communicating with ground control at 11:37am, South Korea’s defence ministry said.
The satellite promises to enhance Seoul’s ability to monitor nuclear-armed North Korea, which has until now been heavily dependent on the surveillance capabilities of its ally, the United States.
The satellite, which will operate between 400 and 600 kilometres (370 miles) above Earth, can detect an object as small as 30 centimetres (12 inches), according to the Yonhap news agency.
South Korea, which remains technically at war with the North, intends to launch four more spy satellites by the end of 2025 to boost its ability to keep tabs on Pyongyang.
North Korea’s launch of the Malligyong-1 satellite last month drew condemnation from the US, South Korea and Japan, whose governments view Pyongyang’s space programme as a pretext to test banned ballistic missile technology.
North Korea’s nuclear weapons and ballistic missile capabilities have advanced rapidly under Kim Jong Un, the third generation of his family to rule his secretive country, despite international censure and sanctions.
On Saturday, North Korean state media, which is known for its bellicose rhetoric, warned that any interference in the country’s satellite programme by the “brigandish” US would be considered a declaration of war.
“In case the US tries to violate the legitimate territory of a sovereign state by weaponising the latest technologies illegally and unjustly, the DPRK will consider taking responsive action measures for self-defence to undermine or destroy the viability of the US spy satellites by exercising its legitimate rights vested by international and domestic laws,” the Korean Central News Agency quoted a defence ministry spokesperson as saying.