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Mosaic: this view of Earth was assembled from 70 images. Triana will capture the scene in one frame. Credit: NASA

The US space agency NASA and Congress have given the go-ahead to a $75 million satellite that will regularly return updated pictures of Earth from space, beginning in early 2001.

Dubbed ‘Triana’ after the Spanish sailor who was Columbus's lookout, the satellite was conceived by Vice-President Al Gore as an “inspirational” project (see Nature 394, 213; 1998 ). Money for Triana will come from the agency's existing $1.4 billion budget for Earth science.

A mission concept by Francisco Valero of the Scripps Institution of Oceanography in San Diego has beaten eight other proposals submitted to NASA earlier this year. Triana will be stationed at the L1 ‘neutral gravity’ Lagrange point, 1.5 million kilometres from Earth in the direction of the Sun. It will have a 16-channel, multispectral imaging camera designed by Lockheed-Martin, which has flown previously on other spacecraft. Valero's group also plans to fly a radiometer for measuring the total energy reflected from the Earth, and a small solar wind monitor.

Measuring Earth's reflected energy currently requires piecing together thousands of satellite observations, says Valero. Triana's whole-Earth view will allow scientists to “look at the planet in a new way”. Its unique viewing geometry will also show “hot spots” of reflected light, yielding information about forest canopy structure and vegetation health.

Owen Toon of the University of Colorado, who heads one of the interdisciplinary science teams for NASA's Earth Observing System (EOS) of satellites scheduled to start launching next year, believes Triana will be an “interesting platform” for observing Earth from a new location. Piecing together the global radiation budget is not a negligible problem, he says.

NASA had no plans to fly an all-Earth radiometer before Gore came up with the Triana concept. Bruce Wielicki of NASA's Langley Research Center in Virginia, the principal science investigator for the EOS CERES instrument that will measure energy reflected from clouds, agrees that the new vantage point could have scientific value. But he believes, like many scientists, that Triana will be “more of an emotional and educational thing” than a research programme. “I don't think it's what [scientists] would have picked a priori,” he says.

Wielicki, however, believes the Earth science community could use a high-profile mission to engender public interest, just as the Hubble Space Telescope does for space-based astronomy. “The American public, to be honest, doesn't want just pure science,” he says.

NASA, which announced its choice of Valero's design last week, is not saying what other parts of the Earth science programme will be squeezed to pay for Triana, although it has submitted to Congress a plan for “rephasing” some projects. Building the spacecraft and instruments will cost $35 million this fiscal year, with the balance spent in 2000.

Although many researchers are uneasy with the way Triana came about — Gore effectively handed his pet project to NASA as an assignment — it is unlikely to be a major burden on the Earth science community. “It's a small enough project that everybody knows it's not going to break the bank,” says Wielicki.

The House of Representatives prevented NASA from spending money on Triana until Congress was convinced it had support in the scientific and/or commercial sectors. But that restriction was removed in the agency's funding bill passed last month. Congressional sources say Gore took his case in person to Jerry Lewis (Republican, California), the House appropriations subcommittee chairman, before the bill was finalized.

Valero's concept leaves the non-scientific aspects of the mission to NASA. The agency says it plans to solicit educational proposals next year and commercial partnerships “over the coming months”.