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An Earth-viewing satellite that few Earth scientists want may be of more use to space physicists stunned by the apparent loss of the US-European Solar and Heliospheric Observatory (SOHO) (see Nature 394, 5; 1998).

Earth in view: Gore's announcement (above) of his Triana project has met criticism in Congress. Credit: AP/KUNI

The US space agency NASA last week asked for proposals for the Triana spacecraft, suggested by US Vice-President Al Gore in March as a way of inspiring the public with live pictures of Earth taken from space (see Nature 392, 220; 1998).

The $50 million satellite, to be launched in late 2000 (when Gore is expected to be campaigning for the presidency), would be parked in a stable orbit 1.5 million kilometres from Earth in the direction of the Sun.

According to a reference mission design provided by NASA, the only instrument on board would be a colour camera capable of returning a new image of the whole Earth every three minutes. The best resolution would be 14 kilometres; this is poor by the standards of the remote-sensing satellites now in Earth orbit, which can see details as small as a few metres across.

Earth scientists have been largely indifferent to Gore's idea, or have grumbled, in private, that it may take funds from more legitimate peer-reviewed projects. Most of the scientists who answered an informal NASA request for ideas for Triana in April proposed adding something else to the satellite, such as solar radiation sensors or a more capable camera.

Such extras may in fact be necessary to save the project. Appropriators in the US House of Representatives have blocked funding for Triana until NASA can show — based on the proposals it receives by the end of August — that the idea has support in the scientific community or private sector.

“NASA must demonstrate for the [appropriations] committee that the agency has a plan for a public-private, peer-reviewed mission, which has resulted from a competitive process,” wrote the lawmakers in a report accompanying NASA's 1999 spending bill. The chairman of the House subcommittee on space, Dana Rohrabacher (Republican, California), has dismissed Triana as a “$50 million politically correct screensaver”.

NASA's solicitation encourages proposers to embellish the basic single-camera concept, as long as they supply the additional funds. The fact that Triana is destined for the same unusual orbit as SOHO has drawn the attention of NASA managers working on contingency plans should the $1 billion solar observatory be declared a loss.

George Withbroe, who heads NASA's solar and space physics programme, says it may be several months before SOHO's fate is known, as its solar panels may slowly turn to catch enough sunlight to repower its batteries. Although engineers are uncertain this will work, or what condition SOHO would be in after a long dormant period, Withbroe says “I'm not going to write it off yet.”

But, to preserve the option of launching some solar-observing instruments in time to monitor the solar sunspot maximum expected to begin next year, officials from NASA and the European Space Agency have already started looking at quick, cheap recovery plans. Triana's fast track to launch makes it especially appealing.

The proposed spacecraft is much smaller than SOHO, but Withbroe says it may be able to piggy-back some high-priority instruments, such as a coronagraph, if necessary.

NASA is looking at other options, such as speeding up the STEREO solar-imaging mission now planned for launch in 2004.

US and European space managers will meet this month for further discussions on recovery plans for SOHO.