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Explorer 49
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<p>Explorer 49 (also called Radio Astronomy Explorer-2, RAE-B) was a <a href="/facts/NASA/TIMCV0yV">NASA</a> 328 kg (723 lb) satellite launched on 10 June 1973, for <a href="/facts/Longwave/w4flmdvu">long wave</a> <a href="/facts/Radio_astronomy/TdjF4LgL">radio astronomy</a> research. It had four 230 m (750 ft) X-shaped antenna elements, which made it one of the largest spacecraft ever built. </p>