By Paul Reynolds
World Affairs correspondent, BBC News website
The Chinese hit their target, but most satellites are not so vulnerable
The announcement by China confirming that it has destroyed a satellite with a ballistic missile is a challenge to the recently formulated American policy insisting that Washington reserves its "rights, capabilities and freedom of action in space".
In 2002, China and Russia proposed a treaty banning the use of weapons in space, but the United States opposes such a treaty and the Chinese action is unlikely to weaken that primarily unilateral American approach.
Washington puts more faith in its own abilities to protect its interests than in a treaty.
US policy, authorised by President Bush on 31 August last year, included the statement: "The United States will oppose the development of new legal regimes or other restrictions
that seek to prohibit or limit US access to or use of space."
China might be saying that, without a treaty, anything goes and that includes the development of satellite-destroying systems.
Its action is likely to increase the US long-term determination to protect its satellites upon which it relies heavily for imagery, communications, targeting, navigation, early warning and weather.
At the moment, though, most of these satellites are in high orbit. This would protect them from the kind of operation carried out by the Chinese, which was against a low orbit vehicle.
Michael O'Hanlon of the Brookings Institution in Washington wrote in the Financial Times: "Most US satellites are not vulnerable to attack today nor are they likely to be in the years ahead.
"Thereafter, threats may often be handled through... redundant systems [having more than one satellite doing a particular task] rather than an all-out space weapons competition."
Space is not entirely a no-man's land, open to competition or cooperation as nations see fit
According to the British Parliamentary Office of Science and Technology (OST), the US operates over half the more than 270 military satellites in orbit.
Russia has about 85, but 45 nations in all have launched satellites for various purposes. India's and China's programmes are "developing fast" according to the OST. Over 800 satellites orbit the earth in all.
Space is not entirely a no-man's land, open to competition or cooperation as nations see fit.
The Outer Space Treaty of 1967, ratified by the major powers, does ban nuclear weapons in space. Its Article IV says: "States Parties to the Treaty undertake not to place in orbit around the earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner."
But significantly it does not mention other weapons. Therefore, although space has so far been
free of weapons based there, that might not last.
In 2004, the US Air Force issued a document called "Transformation Flight Plan" which envisaged a whole array of space weapons both offensive and defensive. They would include anti-satellite systems and even things called "hypervelocity rod bundles" that could be hurled down on a target from space.
In the meantime, the US is developing the so-called "son of star wars" missile defence system and only this week news emerged of American contacts with Poland and the Czech Republic about building links in the system there.
However, the Chinese action can also be seen as part of its general military build-up, a process designed to put it in a position to impose its will on its highest priority issue - Taiwan.
China's policy towards Taiwan is clear. A Chinese defence white paper in December 2004 stated: "We will never allow anyone to split Taiwan from China through whatever means. Should the Taiwan authorities go so far as to make a reckless attempt that constitutes a major incident of 'Taiwan independence', the Chinese people and armed forces will resolutely and thoroughly crush it at any cost."
It wants to be strong enough first to deter Taiwan from declaring independence and then strong enough to invade it if it does. However, the latter capability will take many years to achieve.
And knowing that it is possible that the US will defend Taiwan against any attack, it has to take into account US capabilities. This first exercise in undermining US reliance on satellite communications is a pointer to where it wants to go.
'Against the thaw'
The Chinese action has caused some consternation in the region as well as in Washington.
"It demonstrates that China's capabilities are developing but it is not very helpful to relations with its neighbours," according to John Swenson-Wright of leading UK think-tank Chatham House.
"It could be seen as showing a Sino-centric disregard for others, though China has pushed at the envelope before, by, for example, sending research vessels into Japanese waters.
"This military move goes against the political thaw that the Japanese Prime Minister Abe has initiated since coming to power. It will intensify the debate under way in Japan about its own military development which includes cooperation with the United States over a missile defence system."