North Korea's "unshakable stand" that the rocket programme will continue despite UN condemnation and calls for new sanctions.
The huge rally in Pyongyang, shown on state television, came two days after the launch of the three-stage rocket and just ahead of the anniversary Monday of his father Kim Jong-Il's death.
The huge crowd standing in organised ranks in Kim Il-Sung Square -- named after Kim Jong-Un's grandfather -- cheered as top officials hailed the success of the launch and praised the "bravery and wisdom" of the dynasty's scion.
Refuelling its criticism of Wednesday's launch, the US State Department said Kim had the chance as new leader "to take his country back into the 21st century" but instead was making the "wrong choices".
Unbowed, Kim stressed the need "to launch satellites in the future... to develop the country's science, technology and economy", according to the North's official Korean Central News Agency (KCNA).
It gave new details of the launch of the rocket to propel a satellite into space, which the United States, China and others on the UN Security Council said violated a ban on long-range ballistic missile tests by North Korea.
Kim had issued the final written order for the launch on Wednesday morning and "keenly observed" the whole process, KCNA said.
By placing a satellite in orbit, North Korea "showed at home and abroad the unshakable stand... to exercise the country's legitimate right to use space for peaceful purposes", Kim said according to the agency.
The UN Security Council held emergency talks on Wednesday after the North, already under international sanctions for nuclear tests in 2006 and 2009, ignored pleas from friends and foes and went ahead with the launch.
The council warned of possible measures over what the US called a "highly provocative" act as countries including South Korea and Japan pressed for stronger sanctions.
The rocket launch has been seen as a timely boost for Kim, laying to rest the humiliation of a much-hyped but failed launch of North Korea's Unha-3 rocket in April, when the carrier exploded shortly after take-off.
Outrage over the recent launch was mixed with concern that North Korea may follow past practice in following up a missile or rocket launch with a nuclear t after it tested a long-range missile. The second test, in May 2009, came a month after a rocket launch that North Korea claimed had put a satellite in space.