WASHINGTON (Reuters) - North Korea’s controversial rocket launch put two objects in space, according to the U.S. Joint Space Operations Center. It is unclear if either is sending out signals. Following is what is known about the launch so far.

- North Korea launched what it said was its Kwangmyongsong-4 satellite earlier than expected. The launch took place at 8:59 a.m. local time on Sunday in North Korea. Pyongyang moved up its launch window, which was initially slated to begin on Feb. 8.

- The U.S. Joint Space Operations Center (JSPOC), an arm of U.S. Strategic Command, said on the public website Space-Track.org that it is tracking two objects in orbit at an inclination of 97.5 degrees, a nearly polar, sun-synchronous orbit.

- The launch vehicle was likely similar to the one used in North Korea’s last launch in December 2012, since the satellite orbit and other details are similar, said John Schilling, an aerospace engineer and missile technology specialist contributing to the Washington-based 38 North project that monitors North Korea.

- The satellite North Korea launched in December 2012 circles the earth every 95 minutes, but no signal has ever been detected from the 100-kg (220-pound) hunk of black metal the North said was equipped with cameras to send images back to earth.

- U.S. officials and experts said it would likely take several days to determine if the satellite can stop tumbling in orbit and communicate with the ground. It is apparently intended to stay in orbit for about four years, Schilling said.

- North Korea launched the satellite on an 80-ton rocket called the Unha-3, or one that was very similar. The United States and its allies believe the launch was cover for a missile test, but some experts question whether the Unha-3 can be converted into an effective intercontinental ballistic missile (ICBM), that is capable of reaching the U.S. mainland.

- The long-range rocket flew over the airspace of Japan’s Okinawa region, according to Japan’s NHK television. Okinawa is home to the U.S. 7th Fleet, which includes some 70 to 80 ships and submarines, 140 aircraft, and about 40,000 troops.