Regional threats

Japan's spy satellite programme was initiated after North Korea launched a ballistic missile that flew over Japan in 1998.

The programme was delayed in 2003 when a rocket carrying two satellites veered off course and had to be destroyed in a spectacular fireball.

North Korea ratcheted up regional tensions last year when it conducted a nuclear test in October after a salvo of missile tests in July.

In January, China destroyed one of its own satellites with a ballistic missile, an experiment that sparked criticism around the world.

Law change

Japan's space scientists have long complained that the country's technical prowess has fallen behind because of a 1969 parliamentary resolution limiting the use of space to peaceful purposes.

China, for example, has carried out manned space flights, a feat Japan has never attempted.

Shinzo Abe's, Japan's prime minister, is likely to submit a bill to the current session of parliament that would ease regulations and allow non-aggressive military use of space, government officials have said.

The rocket launched on Saturday was also carrying an experimental optical satellite, aimed at improving the level of detail obtained from the next generation of satellites.

At present, Japan's spy satellites can distinguish objects one metre or more in diameter, whereas US military satellites are said to be able to pick up items one-tenth that size.

Japan has encountered difficulties with other space projects.

Its biggest-ever satellite, launched last year and designed to improve mobile phone communications, is itself having communication difficulties.