Archive
04/15/2019 – Ephemeris – Why land at the Moon’s south pole?
Ephemeris for Tax Deadline Day Monday, April 15th. Today the Sun will be up for 13 hours and 28 minutes, setting at 8:27, and it will rise tomorrow at 6:57. The Moon, 3 days past first quarter, will set at 5:53 tomorrow morning.
The hottest piece of real estate on the Moon is the south pole. Unlike the Earth’s south pole and the rest of the Moon, except the north pole, there are mountain tops that are always in sunlight. The Moon has a very small axial tilt, only a degree an a half, compared to the Earth’s 23 and a half degrees which plunges the earth’s poles into a 6 month’s night. Another benefit of the small tilt is that the floors of craters at of near the poles never see sunlight, so are hundreds of degrees below zero and can be cold traps for water vapor from passing or colliding comets. Yes, thar’s water in them thar craters. It’s more valuable than gold, providing oxygen to breathe and hydrogen and oxygen for rocket fuel.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The south pole of the Moon where the presence of water ice is detected by the absorption of neutrons by the hydrogen atoms in the ice. Credit NASA/GSFC/SVS/Roscosmos.
10/26/2015 – Ephemeris – RIP Robert Farquhar interplanetary navigator extraordinaire
Ephemeris for Monday, October 26th. The Sun will rise at 8:12. It’ll be up for 10 hours and 28 minutes, setting at 6:40. The Moon, 1 day before full, will set at 8:10 tomorrow morning.
This morning Jupiter and Venus appear close together in the morning sky. They are said to be in conjunction. Also Venus is at its greatest separation from the Sun today. It will slowly begin to fall back toward the Sun. Last week Sunday Robert Farquhar died. He developed the technique of orbiting the L1 point between the Sun and the earth where the Earth nullifies the Sun’s gravity, so a spacecraft can stay there between the Earth and the Sun. He designed the trajectory for the ISEE-3 spacecraft that acted as an early warning for particles coming from the Sun. He also liberated it in 1982 and through a series of ingenious maneuvers worked it into a solar orbit that flew it through the tail of Comet Giacobini-Zinner.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
ISEE-3’s orbital path to the halo orbit at the Earth-Sun Lagrangian L1 point and out to cross the path of Comet Ziacobini-Zinner ahead of the fleet heading to Comet Halley. It was renamed ICE (International Comet Explorer). Credit: NASA/GSFC
Here’s a link to a page that recounts the quest to return the spacecraft to its L1 position by Farquhar and his band of “rouges” last year.
Bob Moler's Ephemeris Blog 