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mfb- t1_iyaxg35 wrote

Reply to comment by KonigVonMurmeltiere in Astronomers Worldwide Troubled by New 'Cell Phone Towers in Space' by IslandChillin

Starlink has uncovered cells around major radio telescopes, i.e. it doesn't send direct signals in that direction. AST SpaceMobile could do the same. How much would that help?

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KonigVonMurmeltiere t1_iyb0jj2 wrote

It would help a lot, and that’s exactly what radio astronomers are proposing. The FCC required Starlink to create those gaps, and they aren’t perfect. Enforcement is lax and the protected areas aren’t big enough so radio observations are still impacted by Starlink, but it’s still a big improvement. Basically radio astronomers are asking the FCC to treat 5g cell frequencies with the same care and consideration that other frequencies already get. The Government Accountability Office (GAO) wrote a recent report that could be interpreted as saying the FCC needs to be looking into this and other concerns.

It’s important to note that the FCC has not granted permission for AST SpaceMobile’s plans yet, they only have an experimental license for one single satellite. So there is time to act and come to an agreement. But compared to SpaceX, Blue Origin, and others, AST Spacemobile has not been very cooperative about working with astronomers. They ignored dozens of invitations to meet and discuss the problem, various conferences on the topic, etc, and are only just now in the early stages of discussing it - but have made no public comments or promises.

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Born_Employment405 t1_iybfhic wrote

AST owns no spectrum. It has to have a local partner in country like Tmobile or Claro to operate. They use the partner's spectrum. If they transit without spectrum rights they'll be fined. If they receive without an MNO partner it's unlawful surveillance. They're only going to operate in places where their partner is currently permitted to operate. If there's a prohibition on transmission because of radioastronomy AST will need to observe that prohibition too. Also, GPS space segment clocks are hyperstable over long periods, they only need to be calibrated once every 10 years.

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KonigVonMurmeltiere t1_iybihpj wrote

Correct, they'll only be broadcasting in certain areas where the partners are permitted to operate, using their spectrum. At the moment there are few regulations on mobile providers in most places, as stated in the article. In the past that wasn't a big deal because most radio observatories are remote and many are typically situated in valleys or bowls so the terrain helps block the interference, but that may not be enough anymore.

The clocks may be stable but the Earth is changing all the time so it still has to be updated frequently, not just time offsets but position offsets to account for tectonic activity, changes in the Earth's rotation and precession, etc. It is all very small but over time the errors grow.

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toodroot t1_iyb3oe5 wrote

You can get Starlink at several EHT stations, so I'm not so sure how true that is. For example, Haystack.

Maybe that changed more recently?

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mfb- t1_iyb4s5g wrote

It can be a bit confusing, but if you check the map then it has gaps in these locations. I have a list of all of them, there are two holes without an explanation and something weird at the Polish border, but apart from that all holes are radio telescopes. It looks like actual signup is not always following the map 1:1.

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toodroot t1_iybalip wrote

OK so that changed. I had put in reservations for Owens Valley, Haystack, and the LMT in Mexico and was notified that the first 2 cells were opened... but that was quite a while ago now.

Other ones not there off the top of my head:

EHT: Kitt Peak and Mt. Graham AZ; IRAM 30m uphill from Grenada; NOEMA in the French Alps, and I know that Thule Greenland is using Starlink. The South Pole will likely want to use Starlink.

VLBA: Arecibo (the VLBA antenna didn't fall down)

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mfb- t1_iybh5uw wrote

Several radio telescopes don't have empty cells, indeed. I don't know how they decided on that list and it can change on short notice - it's just a software setting anyway.

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toodroot t1_iybjotr wrote

One nit is if they actually have customers in those cells -- no one lives near the LMT, NOEMA, or the IRAM30m, but actual people certainly do live near Haystack.

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ahecht t1_iybuwm4 wrote

Starlink currently has a gap over Haystack, as well as one over the nearby VLBA antenna in Hancock, NH.

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