The rocket itself is 30 meters, or about 100 feet, long. It was white, with red and blue paint.
International leaders have urged North Korea to cancel the launch, but Pyongyang has refused to back down, insisting that it needs the satellite to gather information on its crops, forests and weather.
An independent European analyst who visited the launch site said he saw nothing obvious that raised red flags.
"I don't know what they want to do in the future, but today what we see is a space launcher," Christian Lardier said.
Bill Richardson, the former U.S. ambassador to the United Nations, said Kim Jong Un may be trying to consolidate his leadership by sending a message to two audiences -- to the international community, he may be trying to establish himself as in charge. But his most important audience is the North Korean military and party leaders, he told CNN. "He's trying to show them that he is not going to buckle down from the United States or the six-party talks or China; that they're going to proceed with this launch; that they're going to proceed with him taking over the leadership of the country."
Richardson urged the United States not to react in haste. "Let's see what eventually happens," he said. "This is how the North Koreans operate: They try to send these huge, scary messages by these actions."
The last time Pyongyang carried out what it described as a satellite launch, in April 2009, the U.N. Security Council condemned the action and demanded that it not be repeated.
China, North Korea's closest ally and largest provider of aid, has expressed concern about the planned launch. Beijing says it has held talks with Pyongyang on the matter, but they appear to have had little effect on the North's plans.
"China strongly encourages everyone involved to remain calm and reasonable," said the Chinese foreign minister, Yang Jiechi, according to a report issued Monday by the official Chinese news agency, Xinhua. "These issues need to be worked out in a diplomatic and peaceful manner."
Analysts say the planned trajectory of the multistaged rocket's path is north to south over the Yellow Sea, with the main body of the projectile eventually landing in the Pacific Ocean near the Philippines.
President Benigno Aquino III of the Philippines has condemned any such launch as a "needless provocation" that could increase tensions in Southeast Asia.