Leading figures from New Zealand's astronomy community have questioned our involvement in building the planet's largest radio telescope - with one top scientist labelling it a "zombie project".

But the head of the Kiwi alliance helping develop the massive Square Kilometre Array (SKA) insists the project is well worth New Zealand's investment, which runs into the millions of dollars so far.

Projected to cost more than $2b, the SKA is touted to ultimately reveal unprecedented information about the nature and origins of our universe.

Once fully constructed in 2030, the vast array would be 100 times as sensitive as the biggest present-day telescopes and have image resolution quality 50 times the Hubble telescope's.

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Its backers say it will be able to capture signals produced by sources that could be traced as far back as 13 billion years ago, when the first galaxies began appearing, and detect radio activity up to 50 light years from Earth.

So far, only some of the precursor infrastructure has been built ahead of its first phase of construction, called SKA1, which itself represented just 10 per cent of the total project.

New Zealand, part of a 10-nation consortium contributing to its construction, first proposed hosting the array jointly with Australia in 2009, but dual sites in the remote deserts of Australia and South Africa were later picked instead.

Despite that, teams of New Zealand experts have remained involved, with one helping design what is effectively the SKA's brain, its Central Signal Processor, and another working on its Science Data Processor, combining the processing power of 100 million computers.

The Government has so far spent more than $2m on the project and involved companies and groups from the ICT community say it could help make New Zealand a global big data hub.

But University of Auckland cosmologist Professor Richard Easther said many Kiwi astronomers were sceptical about what he considered a "zombie project" and its supposed spin-offs.

"This is going to be easily the biggest investment in astronomy in New Zealand - but it's not being welcomed by most astronomers."

Easther said the SKA project had been "down-scoped" and its build timeline had been pushed out to the point it was a "thin-shadow" of what was talked about a decade ago.

The biggest science goals still fell inside the roadmap of the project's second phase, "and they don't even have a plan to figure out what SKA2 would look like", he said.

"So I can't even see that starting before the 2030s, and by that time, more nimble things would have come along and done all of it already."

Easther was concerned there had been no cost-benefit analysis that pitted the SKA against other big projects to invest in instead.

"There has always been this assumption that we can get into it as a way of building international relations, but there was always a kind of baseline assumption that the New Zealand astronomy community would be really excited about it.

"And if I look around the community, the majority of astronomers in New Zealand are really concerned that the SKA will turn into this white elephant for us, rather than an asset.

"I think that if we were to ask the hard questions about the SKA, there would be a graceful exit, rather than a greater commitment."

University of Canterbury astronomer Associate Professor Michael Albrow was concerned the SKA had been funded by New Zealand more as an IT infrastructure project rather than a science project.

"This is going to be easily the biggest investment in astronomy in New Zealand - but it's not being welcomed by most astronomers," Professor Richard Easther says. Photo / File

"The majority of New Zealand astrophysics researchers feel that this particular project will not generate the greatest scientific return for New Zealand relative to its cost," he said.

"This would probably be true for exclusively committing to any single very large offshore project."

University of Auckland astrophysicist Dr Nick Rattenbury argued New Zealand's research community hadn't grown in ways that would utilise the SKA to answer outstanding questions in astrophysics.

"We have yet to develop, as a nation, a robust process for determining how and when the country spends significant sums of money in order to join large international scientific collaborations lasting many years."

Another Canterbury University astronomer, Dr Simone Scaringi, said there hadn't yet been any process where interested astrophysicists had been consulted to recommend the best way of supporting astronomy and IT research in New Zealand.

"Thus the benefits the SKA might provide to New Zealand science are extremely limited," Scaringi said.

"The SKA will eventually be a revolutionary radio telescope. The key word here, however, is 'eventually'.

"The timeline for the development keeps being delayed, up to the point where various smaller incarnations of the project are now being considered.

"The direct consequence of this is that some of the major science questions the original SKA was hoping to answer will be addressed by other projects by the time the SKA becomes a reality."

AUT's Dr Andrew Ensor, director of the NZ SKA Alliance, said Kiwi members had been clarifying with visiting science director of the global SKA Organisation, Dr Robert Braun, what science could be expected out of the first phase.

"What we have done is declared that these are the likely science objectives for phase one of the project, and some have been pushed off, while others have been prioritised," Ensor said.

But, he added, carrying out the science would still take a long time.

"These mega-science projects take a very long time, and scientists, like all of us, are quite impatient about things - they want the science now."

Some top scientists had already been attracted here because of the SKA, and the project had benefited his own group.

"As a member country of this, it does mean, naturally, that over time you are going to attract more researchers and more funding into this area of astronomy."

Ensor said a cost-benefit analysis had already been carried out - and the debate about whether New Zealand should take part had been had, a decade ago.

He argued that New Zealand wasn't locked into the SKA, as member countries could change what they contributed down the track.

The total cost of the project would also be spread wider as more nations signed up.

MBIE's innovation and international science general manager Peter Crabtree also argued there had been "clear benefits" from New Zealand's involvement, including the development of niche ICT capabilities.

MBIE was still involved in discussions about setting up the SKA as an international organisation under a convention, which would require longer term financial contributions from countries that sign up to the convention.

"The Government has not yet taken a decision on signing the convention," Crabtree said.

"In making that decision, MBIE will provide advice to the Minister of Research, Science and Innovation that will weigh up factors such as scientific and industry opportunities for New Zealand, financial commitments and our science relationships with other countries."