Bob Moler's Ephemeris Blog

Ephemeris for Thursday, October 25th. The Sun will rise at 8:11. It’ll be up for 10 hours and 30 minutes, setting at 6:41. The Moon, 1 day past full, will rise at 7:44 this evening.

A joint mission to Mercury by the Europeans and the Japanese called BepiColumbo was launched late Friday night October 19th our time (EDT), 20th (UT). It will take 7 years to be able to drop into orbit of the innermost planet to make only the second spacecraft to do so. To drop into Mercury’s orbit from the Earth’s orbit the spacecraft will need to lose a whole lot of velocity. The trip there will entail one flyby of the Earth, two of Venus, and six of Mercury itself. Planetary flybys have been used since the 1970s to use a planet’s velocity to add to or subtract from a spacecraft’s velocity, depending on how it approaches the planet. If crossing in front of a planet some velocity is subtracted from the spacecraft, allowing it to drop closer to the Sun. If coming up from behind the spacecraft gets to add to its velocity relative to the Sun.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

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