Tiny satellite will use the dark side of the Moon as a shield | Hacker News Reader

Tiny satellite will use the dark side of the Moon as a shield

cam.ac.uk

Would a satellite positioned at Earth Moon L2 be stable enough? It would also need a relay to communicate with earth…

It takes a bit of stationkeeping to stay at L2; like keeping a ball at the top of a low, smooth hill - needs a nudge every now and then.

A circular Moon orbit can last years with no fuel use if you pick your inclination correctly. Look up "frozen orbits" (the Moon is lumpy)

> Once CosmoCube’s data is back on Earth

Did I miss it or did they fail to explain how that would work? Does it just slowly move around the moon so it gets its 1000 hours of observation, then eventually comes out of the EM shadow?

Or is there some final boost that pushes it?

Will it crash into the moon eventually?

It would orbit the moon as a satellite, presumably in a fairly tight and low orbit; the article says a 2 hour period, which is < 100 km above the surface. About half the time it would be on the "far side" and Earth would be blocked by the Moon below it.

The other half it would have line-of-sight with Earth and be able to communicate, but also exposed to radio pollution. Presumably the mission designers would hibernate the experiment for this period.

It will almost certainly hit the moon one day. The moon has many mascons (mass concentrations, a.k.a. lumps) and destabilizes anything orbiting it over a long period of time. Or even a short period of time: https://en.wikipedia.org/wiki/Apollo_16#Particles_and_Fields... But an orbit can be chosen to give at least a couple years, which is the mission goal.

I remember mentions of mascons during the Apollo missions. They were at the time a bit mysterious but their existence and influence were known.

Moon-Earth is 384,400 km, and Moon-L2 is 61,347 km. The moon has a radius of 1,737 km. From the L2 point, a beam shearing the moon's surface will pass earth at a distance of 12,642 km from its center - or 6,272 km above the surface. That is well within the orbit of geostationary and GNSS satellites. So yes, you do indeed need a relay, but it can piggyback off of a MEO constellation like O3b, or make use of one of the many TV broadcast sats. Use two 90-degree out-of-phase GEO sats and your comms beam passes a comfortable 2,363 km above the moon's surface.

Usually sats like those (there have been several dozen) aren't at the L2 point, but are in a Lissajous orbit around it. This avoids the worst stability issues, although they are still dynamically unstable so they'll require minor station keeping adjustments from time to time.

Plot twist, they just bolted one of these onto the back of the cubesat:

https://www.goldrecordart.com/product/sku/PFplat1

RFSoCs seem like extreme overkill for this frequency range, though since Xiphos makes a space-grade one, it's not so unreasonable I guess.

Alas, I'm working on a competing project that I won't go into detail about :).

s/dark side/far side/

You're generally correct, but in this particular instance it does actually make sense to call it the dark side. Dark, as in "quiet" from RF interference. Just like some areas on Earth, near radio observatories, are declared "dark" (i.e. everyone tries to avoid using high RF emitting stuff in these regions, even comms satellites avoid it).

> even comms satellites avoid it.

If only ... Starlink is nominally "off' over the RQZ in W.Australia, but still leaking interference from not fully shielded electronics.

Starlink Coverage holes (3 years ago) - https://old.reddit.com/r/Starlink/comments/ymm6rv/starlink_c...

(July 2025) Starlink satellites disrupting astronomy research in WA's Murchison, study finds - https://www.abc.net.au/news/2025-07-25/starlink-satellites-d...

Dark side of the moon = the side opposite the sun, doesn't change here

It's only facing away from earth, it can face the sun just fine. Rotation is every 4 weeks.

To be launched within five years?! The Chinese will long before that have produced something similar and returned the data already.

The UK has to become a lot more active in getting this project to the launchpad.

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