FACTBOX: Key facts about Japan's space program

(Reuters) - Japan's space agency plans to launch a lunar explorer called Selenological and Engineering Explorer (SELENE) on Friday, its first mission to orbit and explore the moon.

Nicknamed "Kaguya" after a moon princess in a Japanese fairy-tale, the lunar orbiter will study how the moon was formed.

Here are some facts about Japan's space program and its lunar probe:

-- Japan's space program was begun in the 1950s by universities and government laboratories. The country launched its first satellite in 1970, making it the fourth nation to do so after the Soviet Union, the United States and France.

-- The program is run by the Japan Aerospace Exploration Agency (JAXA), created in October 2003 when three organizations merged. Mitsubishi Heavy Industries works closely with JAXA in manufacturing satellite launch rockets. JAXA has an annual budget of 183 billion yen ($1.6 billion).

-- Japan had launched 120 satellites by 2006, ranking fourth globally but lagging far behind top-ranked Russia with about 3,200 launches, including those by the former Soviet Union, and the United States with around 1,800.

-- Japan's space program has suffered a number of setbacks, including in 2003 when a domestically developed H-2A rocket carrying two spy satellites veered off course and had to be destroyed. In March, one of what had become a set of four such satellites malfunctioned and will not be replaced until 2011.

-- Japan's space scientists have long complained that the country's technical prowess is hampered by a 1969 parliamentary resolution that limits the use of space to peaceful purposes. The ruling Liberal Democratic Party wants to relax the restriction but with the opposition now in control of parliament's upper house, doing so would likely be difficult.

-- Japan's 55 billion yen ($484 million) lunar probe project has itself been plagued by technical problems and is four years behind schedule. The project aims to place a main satellite in orbit around the moon at an altitude of about 100 km (60 miles) and two smaller sister satellites in polar orbits, in a step towards the possible creation of a manned lunar base by 2020.

-- Europe's first lunar orbiter SMART-1 completed its mission in 2006, while China, India and the United States also plan lunar probe launches by the end of 2008.

Sources: Reuters/JAXA (www.jaxa.jp)/NASA (www.nasa.gov)/The House of Representatives (www.shugiin.go.jp)

($1=113.59 Yen)