Archive for June 13, 2022

06/13/2022 – Ephemeris – What’s a near rectilinear halo orbit?

June 13, 2022 Comments off

Since I wrote and recorded this program on June 5th, the launch date has been postponed from June 13th. No new launch date has, been selected, though the launch window extends through the 22nd for this month’s attempt.

This is Ephemeris for Monday, June 13th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:29, and it will rise tomorrow at 5:56. The Moon, 1 day before full, will set at 5:41 tomorrow morning.

Last Friday I talked about the CAPSTONE mission to a near rectilinear halo orbit of the Moon, which, when I recorded this, could launch as soon as today. Anyway, what is a near rectilinear halo orbit? And why is it so special? It is a long looping orbit that comes quite close to the Moon over its North Pole, and very far away over the South Pole of the Moon. Instead of going behind the Moon from the Earth’s perspective, the orbit will always be face-on to the Earth. It will require occasional tweaks to keep it that way, just like the James Webb Space Telescope needs occasional tweaks to keep it in orbit of the Earth-Sun L2 point. That way a lander, or base at the South Pole of the Moon, can keep in communication with the Lunar Gateway for all but a couple of hours each week. Why the South Pole? That’s where the water ice is!

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.


NASA CAPSTONE pathfinder for gateway orbit

NASA CAPSTONE* pathfinder for gateway orbit is to be launched this year by Rocket Lab to prove out the near rectilinear orbit for the Lunar Gateway.

The orbit will pass 1,900 miles (3,000 km) above the Moon’s North Pole and out to 43,000 miles (70,000 km) above the South Pole. The period of such an orbit is about 6.5 days. Landing attempts at the South Pole of the Moon will begin as the lander departs the Orion spacecraft or the Lunar Gateway space station and begins its descent over the North Pole.