
This is a captivating mystery. In 1990 and 1992 when the Jupiter probe Galileo used the Earth for gravitational assists (or “slingshots”), ground-based observers noticed a small (unexpected) boost in velocity as the spacecraft approached Earth. A boost in a few millimetres per second had also been observed in the slingshot of NASA’s NEAR probe two years previously. The same was seen in the flybys of Cassini (in 1999), MESSENGER and Rosetta (in 2005). Many explanations have been put forward – including my favourite that it could be dark matter in Earth orbit kicking our robotic explorers around – but flyby anomalies may have a more mundane explanation.
In keeping with Occam’s Razor (i.e. the simplest explanation is usually the right one), a short paper has been published suggesting that flyby anomalies can be accounted for by using conventional physics…
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