This was inspired by watching For All Mankind on Apple TV+. [Super tiny spoilers ahead.] In season 2, the US has established a pretty solid moonbase near the moon’s South Pole. At one point, the astronauts are watching a live (or near-live) news broadcast of a recent calamity on Earth.
What would be the best way for them to receive the broadcast (ca. 1983, with allowance for some technology having progressed 10 years ahead of schedule due to the continuing space race)? I assume, despite all the talk of aliens being able to receive our TV broadcasts from decades ago, that picking up a usable ordinary broadcast signal even from the distance of the moon would be dodgy—esp. given overlapping frequencies, atmosphere, etc.
Now, they could of course have a special uplink where NASA is sending snippets of news for a short period each day (they do, for example, show a moon-based astronaut being interviewed on the Johnny Carson show, but I assume there are special limited-time resources being dedicated to that). But is there a reasonable way for the astronauts to just kick back and tune in to Earth TV whenever they want? Could they steal HBO from satellite TV signals the way people used to in the 80s with giant satellite dishes in their backyards? Or would there need to be a dedicated Earth-based system constantly beaming junk TV programs to the moon?
A bit of a WAG, but I would assume that any sort of moon base would have a high-speed data link to Earth. I don’t see why that couldn’t include enough bandwidth to allow for streaming of TV content (via whatever the near-future equivalent of Hulu or YoutubeTV is).
@Jas09 nailed it for current 2023 tech. We have dedicated data links to/from the ISS. More and bigger would be built as part of the support infrastructure for a putative permanent Moon base.
In 1983, even with 1989 tech? Nope.
IMO …
There’d be one two-way vid link for Moon base - HQ business that could be repurposed when not in other use to transmit one channel of commercial vid. Most likely somebody on the ground would be responsible for assembling a daily “newspaper” and a few vid clips, then sending that up to the Moon base via the equivalent of email over a 2400 baud dial-up modem.
This is a series that has space shuttle orbiters flying to the moon and manned missions to Mars in a Soyuz module. Not only does it lack verysimilitude, it barely qualifies for somewhatsamilitude.
Given enough Effective Radiated Power, they could receive an 1980s style NTSC (or PAL) signal. Of course having a good gain antenna on the Moon would help. Probably would use different frequencies than broadcast TV. The transmit dish should steer to point to the Moon to maximize gain.
We got live TV, in colour, from the moon in 1972. Heck we had remote controlled broadcasts of live events, with nothing but the camera and tiny dish antenna on the lunar rover pointed back to Earth - famously:
Getting TV back to the moon is symmetrical. A big antenna on the Earth is easy enough, and building another three dedicated deep space network style antennae for a lunar station a trivial undertaking relative to the lunar outpost itself. Don’t even need to tie up the real Deep Space Network. So assume high power and high gain transmission.
Information transmitted is, as always just a matter of Shannon. If you build a nice big antenna on the moon pointed at the Earth the signal to noise improves and your information rate goes up.
Just look at the geostationary TV relay satellites in use in the 80’s. GEO is roughly one tenth the distance to the moon. The sats are about the size of a car, and the uplinking groundstations can be quite small, yet the satellite receives broadcast quality TV from the Earth on an antenna only about two metres in diameter.
To use exactly the same technology and size of receiving antennas on the moon would need 100 times the transmitted power - or a receiving antenna ten times the diameter. Or a mix. Which is reasonably easy, especially as from the point of view of the moon the Earth is near stationary. Corrections to pointing, if needed, happen very slowly, and only require a coverage of a small part of the sky. Depending on the properties of the regolith it may be as easy as laying out a flat phased array antenna on the face of a suitable crater.
Overall you could reasonably set up a permanent link that could include broadcast TV with off the shelf 80’s commercial level tech. Expensive tech, but off the self tech.
As for random reception of TV signals -
remember that channels were allocated by market so there wasn’t overlap. Like how Chicago and Milwaukee couldn’t both have channel 2. You’d get interference.
From the moon, it would be ALL interference. LA and NYC and everything in between are all able to be picked up. You’d get the strongest signal (which was probably Fargo from their high powered 2000ft antenna) and still some interference.
Best to have a dedicated directional broadcast on a different frequency if you intend to actually enjoy watching TV on the moon.
Are these back yards on Earth or on the Moon? The TV satellites were in geosynchronous orbits around the Earth so the satellite is always in the same position more or less with respect to a point on the Earth. Satellite dishes on the Moon, however would have to track the satellite so–harder but probably doable.
If the back yard is on Earth then the signal still needed to be sent to the moon. Probably not off-the-shelf in '83 in our universe but if there had been any demand for it then I don’t know why not.
Isn’t there a similar point, where a satellite could be placed in luna-stationary orbit around the moon, to relay signals between earth and a receiver downlink at the moonbase?
As far as I know, a luna-stationary orbit would work too but then Earth broadcasters would have to track that. Six of one or a half dozen of the other.
Generally speaking a luna-stationary orbit would be pretty tricky, given that it’s tidally locked to earth. The trick to stationary orbits is the orbiting body completes one orbit as the body it’s orbiting rotates one time. The earth rotates at a speed to make this viable at ~35,000 kilometers. For the moon that would be a orbital height of 87,000 kilometers. Unfortunately, this is outside the moon’s sphere of influence which is only 64,000 kilometers, so attempting to orbit that high would cause a satellite to fall toward the earth instead.
Luckily, there is a solution. Lagrange calculated points in a two-body system where a satellite can remain relatively stationary to both bodies. So simply put a satellite at the earth-moon L1, L4, or L5 points. That would let us keep a satellite in the same part of the sky relative to the lunar surface without worrying about Earth’s gravity.
Orbits are difficult around the moon, because of ‘Mascons’ or mass cncentrations. The gravity of the Moon is very ‘lumpy’, and most orbits are not stable (other than identified ‘frozen’ orbits).
Sending TV or internet to the Moon is not difficult. You just need either more power, or larger dishes on each end of the link. The video link from the moon was achieved with less than 20 Watts of power. This low power worked because the receivers were the Parkes or Goldstone dishes. Of course, an Earth-based transmitter could be thousands of Watts, and could be transmitted from a large dish.
I don’t think you’d have to bother. The ambient emissions from Earth would just be a low level of noise. The high-gain antenna that NASA is pointing at you would easily drown out everything else.
Pretty much all the equipment would be off the shelf. The sending side would multiplex whichever channels you wanted on the same frequency bands as a normal TV. They could even take the signals straight from the local stations without a frequency shift. And on the receiving end, you just plug the coax cable into a normal TV.
So you’re saying just use a high-gain antenna and broadcast channels 2, 4, and 7 (or your own local flavor of major network channels) directly at the moon, overpowering any noise from other earth-based broadcasters?
Yep. You’d want a fairly large dish due to the low frequencies; on the other hand, the large wavelengths mean it’s easy to build such a large, sparse dish. You could also build a flat phased array, even with 1983 tech.
Or, you could do a constant frequency shift if you really wanted to run in the GHz. It’s easy to just shift a frequency range up by, say, 2 GHz on the outgoing side, then -2 GHz on reception. After the upshift/downshift, the signals would again be in the 54-216 MHz range of standard VHF analog TV channels.
I would think since there’s a lag, all broadcasts are delayed, it would be simpler to TIVO programs up there. I’d suggest VHS or Betamax recording, but without air, will the recorder motors overheat?
