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I have been considering if it would be possible to place a satellite in a Sun-synchronous orbit in one of the lunar frozen orbits at 86°. According to NASA scientists there are four inclinations for orbits wherein a satellite can stay in low lunar orbit indefinitely:

"There are actually a number of 'frozen orbits' where a spacecraft can stay in a low lunar orbit indefinitely. They occur at four inclinations: 27º, 50º, 76º, and 86º"—the last one being nearly over the lunar poles.

-http://science.nasa.gov/science-news/science-at-nasa/2006/06nov_loworbit/

My question is whether precession would still be possible in a frozen orbit. An orbit over the lunar poles could potentially allow a continuous supply of solar energy. I believe this orbit might be possible with zero eccentricity at a bit above 200 km altitude. This is provided that the satellite can remain in the frozen orbit and would still precess due to the oblateness of the moon. However I am unsure if there might be some reason that this kind of orbital precession might not work as well since I am not very familiar with frozen orbits. I'm also unaware how long it might take for the Earth to perturb this orbit. Is a lunar Sun-synchronous orbit possible when using a frozen orbit?

I also did find an interesting way of reaching a lunar polar orbit on Hop's blog (who had directed me to this site): http://hopsblog-hop.blogspot.com/2013/08/lunar-ice-vs-neo-ice.html

Kind regards,

Peter

1337joe
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Peter
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1 Answers1

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The Moon's $J_2$ of $2.0330530\times 10^{-4}$ gives only very low, not very inclined retrograde orbits. The inclinations start at 130° at a zero altitude orbit, and go up to 180° at about 200 km altitude. See this answer for more details.

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Mark Adler
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  • Could Lunar slight orbital eccentricity be used to achieve orbital precession required? Perhaps in higher Lunar orbits? – TildalWave Sep 18 '14 at 11:41
  • No. You need to keep periapsis above the surface. Increasing $e$ also requires you to increase $a$ to hold periapsis. Overall, the rotation rate of the node goes down as you increase eccentricity. – Mark Adler Sep 18 '14 at 14:10
  • That makes sense, Mark. I think I was using the wrong J2 value in my calculations. Is the one listed in this chart some other coefficient? http://www.mathworks.com/help/aeroblks/zonalharmonicgravitymodel.html – Peter Sep 18 '14 at 19:04
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    Ack. No, I was using the wrong $J_2$ value! I just checked and the number I found was from a table of normalized coefficients, instead of unnormalized. The value you found is the right one to use. The most recent estimate is $2.0330530\times 10^{-4}$. I will update the answer. – Mark Adler Sep 18 '14 at 20:24
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    Er. For the less mathematically inclined such as I ... is answer to the question then a 'No'? – Everyone Sep 21 '14 at 13:10
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    @Everyone While there is barely a Sun-synchronous orbit possible at very low altitude and very high inclination (well past 130° for practicality), those orbits are always eclipsed - they go behind the Moon every 2 hours and experience darkness. Since the question asks about solar power and the nearly-polar 86° "frozen" orbit, the answer seems to be, sadly, and as you have proposed, "No". – uhoh Jan 28 '18 at 15:43