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Last Updated: Thursday, 22 July, 2004, 11:54 GMT 12:54 UK
Nasa rethinks probe to the Sun
By Paul Rincon
BBC News Online science staff, in Paris

The probe would carry instruments to examine particles and radiation
A mission to put an orbiting spacecraft around the Sun may get a second chance, after being rejected by the US space agency five years ago.

A positive assessment of the proposal by the National Research Council has renewed interest at Nasa.

So the team behind the idea is working on another study to examine how such a mission might be carried out.

A new vision for "Solar Probe" was outlined by the project's team at a space exploration conference in Paris.

But building a spacecraft that can survive repeated flybys of the Sun poses significant challenges.

"In order to go close to the Sun and make measurements, you have to deal with the incredible heat that you have there," said team member David J McComas, of the Southwest Research Institute in Texas, US.

"There's something like 2.4 megawatts on a reasonable-sized shield.

"Most of it is radiated out into space, but you still have kilowatts of power that you have to get rid of in other ways," he told the Committee on Space Research (Cospar) scientific assembly.

Sun's corona

The probe would carry a suite of instruments to examine particles and radiation emitted by the star.

It would also investigate the Sun's corona, magnetic field, and internal phenomena such as solar plumes.

Nasa is currently pretty risk-averse, so we can't take too many risks
David J McComas, Southwest Research Institute
Solar Probe might have a type of periscope that could take a safe portion of the Sun's light into the spacecraft for readings to be made.

Proposals for solar probe missions in the US go back as far as 1958. Over the years, many spacecraft designs have been put forward, but they can largely be grouped into two categories: the "dunce cap" and the "parabola".

The dunce cap is conical, to provide a large surface area. The parabola features a large heat shield and an antenna.

The definition team will also be adjusting the project outline to fit the current political climate.

"Nasa is currently pretty risk-averse, so we can't take too many risks. This has to be as low-risk as you can make a mission to go within four or five solar radii of the Sun," said Dr McComas.

The earliest the craft could launch is 2010.

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