The replacement Orbiting Carbon Observatory will monitor Earth’s carbon sinks and sources. Credit: NASA/JPL

The US Congress is ratcheting up demands for NASA to launch Earth-monitoring satellites that could help to verify the emissions targets currently being debated in Copenhagen.

In a US$447-billion spending bill approved on 13 December (see ), lawmakers told NASA to spend $50 million in fiscal year 2010 on a replacement for the Orbiting Carbon Observatory (OCO), which crashed into the ocean near Antarctica in February after a rocket failure. "It looks like there is a future here," says David Crisp, the mission's principal investigator at the Jet Propulsion Laboratory in Pasadena, California. But by adding the OCO to NASA's already long list of Earth-science missions — and with no promise of future funding — some Earth scientists worry that Congress is asking the agency to do too much. Berrien Moore, director of Climate Central, a think tank in Princeton, New Jersey, says that he was both "pleased and worried" by the OCO funding because of the additional burden on the mission programme.

By measuring levels of atmospheric carbon dioxide, the OCO could provide baseline emissions data and act as a proof-of-concept that carbon sources and sinks can be monitored from space. The observatory would measure CO2 changes to a precision of 1 part per million at a resolution of about 3 square kilometres — nearly 30 times that of the Japanese Greenhouse gases Observing Satellite (GOSAT, also known as IBUKI), which launched in January. Replacing the OCO will cost about the same as the original $280-million mission, says Crisp; if funding continues to be granted, the observatory could be launched as early as 2013.

That would require a much bigger budget for fiscal year 2011, but because NASA is one of several science agencies not included in a targeted doubling of basic-science funding (see 'Will the budget bubble burst?'), it may well face a flat budget next year. "Or worse," says Moore.

NASA already has a list of 15 other Earth-science missions that were identified in a 'decadal survey' to prioritize missions over the next ten years. In the spending bill, Congress said it was "concerned" about the limited progress of those missions, and gave $15 million to accelerate two that are intended to monitor global climate change. It has also instructed NASA to look at using commercial providers, following the lead of a panel that reviewed the agency's human spaceflight programme and earlier this year called for greater reliance on commercial rocket companies.

But Moore doesn't see the Earth-science missions being profitable enough for commercial companies to be interested in running them. In lieu of a surprise windfall in February's 2011 budget proposals, he says, NASA might need to delay the missions further: "We may have to rename the decadal programme the centennial."