Hacker News Reader

Comment by kylehotchkiss | Hacker News Reader

The linked FCC letter (https://apps.fcc.gov/els/GetAtt.html?id=203152&x=.) actually explained their rationale well (satellite too small to track with monitoring equipment so there was no way to warn other operators their satellite was about to be pummeled) and their idea to broadcast its location with GPS was not considered reliable enough.

Still seems weird the FCC and not NASA or the Air Force makes this call. Isn't the FCC busy diving into rooms full of gold coins from Verizon?

View on HN

I'm not surprised it's not the Air Force or NASA. As a civilian, there's no activity I undertake that any military person has any jurisdiction over at all (I suppose unless I go onto a military base). NASA, of course, is more of a research and launching facility; they don't really have investigators or the ability fine people.

Unless you use the GPS, and the cellular base stations are time sync with the GPS system, so your mobile phone.

Have you ever flown on a commercial plane? There are several parts of the US that you can't fly over because the USAF says you can't. They also control the GPS constellation and can turn it off at will or degrade the accuracy however much they like- although they've promised that they won't use the ability. The Army Corps of Engineers is involved in a significant portion of public construction like hydroelectric dams and do a lot of environmental regulation.

The military has jurisdiction over more than you might think, they just try to stay out of the way unless it impedes the national defense.

How does "global positioning system" work in space anyway? Was "GPS" an analogy? Is it actually using signals from GPS satellite network to determine position?

It would work the same way it does on earth. Spacebee satellites are at 500km and GPS satellites are at 20,000km, so it shouldn't be a problem getting a signal. You can even pick up GPS at higher orbits than 20000km, but it is more difficult:

https://www.technologyreview.com/s/401315/gps-in-space/

I was under the impression that all non-military GPS devices did not work after certain thresholds such as speed were exceeded to prevent them from being used in missiles.

https://en.wikipedia.org/wiki/Coordinating_Committee_for_Mul...

Entirely client side. Signal received is the same for everyone.

Military has access to higher resolution timestamps to improve accuracy.

Have to wonder if any manufacturers in non-COCOM countries are able to supply such units.

Or how long before you can get around this with an SDR.

Edit: looks like you already can: http://gnss-sdr.org/

On earth you can (in theory) get a position if you have a lock on three GPS satellites as you know that you are on the surface (intersection of 3 spheres). If you're higher up, you be a fourth sat.

I can't conceive how they could lock it down to low speed objects, as it is a one way communication link, but I'd be interested to know if it is possible.

Edit: looks like this is a limit built into GPS receiver devices, not the protocol. If you build your own receiver, then you can get around those restrictions. Not sure if there are licencing issues to worry about, but I can't imagine an adversary to care about that kind of thing, or a company that is launching 'rogue' sats.

It's literally GPS (with the artificial receiver limits removed)

It's being tracked. Look on n2yo. I don't know why they are saying this.

Isn't n2yo a predictor where you pass 6 kepler elements for every orbiting object and update every month for drag? In that case, IRSO could have updated those when they released the satellites right?

They're updated more frequently when the object is being measured.

http://www.n2yo.com/satellite/?s=43142

I took a look earlier today. The epoch for the TLE of this object was from yesterday, which implies that it's being measured in order for the TLE to have been updated.

And looking again now, I see it was updated again today.

Incredible they have this data for objects the size of a book floating at over 100 miles over our heads.

Just about everything sent up is going to want to transmit something down. And one of the FCC's reasons for existing is to try and minimize interference for broadcasters.

Reply on news.ycombinator.com