A world-renowned astronomer, who has discovered more than 400 comets and asteroids, may be forced to abandon his work searching the night sky for objects on a potential collision course with Earth.

Australian Rob McNaught has lost the Nasa funding he relies on as the only astronomer in the southern hemisphere working on a survey to find and track near-Earth objects and possibly help prevent catastrophic collisions.

The Australian National University has stepped in to temporarily support McNaught's position, but has said long-term funding needed to keep the work going beyond the end of this year is ''not going to come from the university''.

McNaught's record working in the Uppsala Schmidt Telescope at Siding Spring Observatory, near Coonabarabran in northern NSW, is formidable.

Since 1987, he has discovered 70 comets, more than twice as many as any other astronomer in history.

According to McNaught, the Siding Spring Survey, the only project observing near-Earth objects in the southern hemisphere, "get[s] a chance to see objects that the northern hemisphere surveys can't research''.

Since 2004, the survey has discovered 412 near-Earth objects, including 80 classified as a potential hazard because they have a diameter of between 100 and 150 metres and an orbit that comes within 7.5 million kilometres of the Earth's orbit.

A fellow astronomer at Siding Spring, Peter Poulos, describes his friend as ''the guardian of all of us, in many ways''.

''He doesn't wear a uniform or a cape, but in the end he's the hero in the movie. He's the scientist that will discover the bad thing heading our way.''

McNaught has been ''extraordinarily successful'', said the head of ANU's school of astronomy and astrophysics, Harvey Butcher.

"We think he's just wonderful  one of the best in the world. This is work that very much needs to be done."

But Professor Butcher said without a new, more powerful telescope and better facilities likely to cost ''a couple of million dollars'', there is ''no clear channel of finance'' to continue it.

McNaught said he had appealed to the Minister for Science and Research, Chris Evans, and the Minister for Industry and Innovation, Greg Combet, to fund the program.

''There is no reason why Nasa should fund every space program in the world,'' he said.

- Sydney Morning Herald