Right of Reply; The science adviser to the Royal Astronomical Society answers Charles Arthur

THE INTERNATIONAL Space Station (ISS) has become a target for disgruntled scientists and hostile commentators who dismiss it as a "waste of space". What are the grounds for this strident criticism?

First, that it is years behind schedule. Yet hardly any major international projects involving advanced technology have been delivered on time. The Eurofighter is an example.

Second, that there is no guarantee that it will produce any money-spinning breakthroughs. If the 15th-century explorers had adopted the same attitude, Christopher Columbus would never have ventured forth from the safe, charted waters of the Mediterranean. As the scientist Saunders Kramer has commented, "We'll find 10,000 things to do on the station that nobody's thought of or even imagined."

Third, that it is a PR exercise. It is undoubtedly true that Nasa actively seeks to promote the advantages of its manned and unmanned programmes, but this can hardly be a crime for an agency that depends for funds on the support of politicians and the public.

Fourth, that it was the dream child of Ronald Reagan. In fact, an American space station was envisaged back in the late Sixties. Indeed, the space shuttle was originally intended to act as a supply ship for such a station.

Fifth, that the station is unsafe. Not a single astronaut has died in action since the Challenger accident 13 years ago. Risk-taking is necessary for progress. The ISS is a unique opportunity to exploit near-Earth space. It provides jobs, boosts technological development and will lead to unforeseen spin-offs. Spread over 15 years, the cost per person is equivalent to less than one lottery ticket per year. Let's build the monster and then see where it leads us.