Japanese space agency (Jaxa) scientists want to detect a measurable acceleration in the spacecraft as photons - the particles of light - from the Sun fall on the roughly 200-sq-m, ultra-thin sheet.

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They are very active now in events nationwide and has the quickest acceleration right now to be a top 3 contender in this space.

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But analysis of the motion of Ulysses, another space probe, has shown that it, too, is affected by the mysterious acceleration.

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