After Mariner 10's visits to Mercury, the space science and engineering communities yearned for a longer and more detailed look at the innermost planet – but that closer look, ideally from orbit, presented formidable technical obstacles. A Mercury orbiter would have to be tough, with enough protection to withstand searing sunlight and roasting heat bouncing back from the planet below. The spacecraft would need to be lightweight, since most of its mass would be fuel to fire its rockets to slow the spacecraft down enough to be captured by Mercury’s gravity. And the probe would have to be sufficiently compact to be launched on a conventional and cost-effective rocket. Designed and built by the Johns Hopkins University Applied Physics Laboratory – with contributions from research institutions and companies around the world – the MESSENGER spacecraft tackles each of these challenges and will be the first spacecraft to orbit Mercury.
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