Real-time visualisation of orbiting satellites | Hacker News Reader

Real-time visualisation of orbiting satellites

apps.agi.com

76 pointsJosephRedfern26 comments

Holy shit, we have a lot of junk out there. It seems like we're building a multi-layered defense shield against alien invasion - the outer band will damage the enemy staging their attack from the Moon, and the inner band shall make it impossible to keep their motherships in low-orbit for continued planetary assault.

"Real-time" is a bit relative (wink) when it takes minutes to get the data into the browser.

The locations are most likely calculated using orbit information published by NORAD and/or the spacecraft operators. This is called ephemeris data, and is usually published in a format called "two-line element," or TLE. A TLE contains a complete description of the spacecraft's orbit at a specific time, so you can then calculate where the spacecraft will be at any moment given that it stays in that orbit.

See http://www.celestrak.com for a bunch more information on the subject. Of particular interest is the TLE format itself (http://www.celestrak.com/NORAD/documentation/tle-fmt.asp).

It's calculated using historical data (the most recent observation) using the Simplified General Perturbations model: https://en.wikipedia.org/wiki/Simplified_perturbations_model...

This is why it's a beast to run. It's looping through some hefty calculations for each satellite every second.

Anybody knows what "nonoperational" means. Are those simply shutdown collecting space dust?

Leaving aside if it's allowed/legal .. I wonder if it's possible to establish communication with a nonoperational satellite, and what tools are required to do so

Last year a team of people crowdfunded, bought some radios off eBay, and took over a decommissioned NASA satelite.

http://observer.com/2014/08/civilians-in-abandoned-mcdonalds...

That's both cool and scary. Someone with a bit of money and a bit more malice could cause a lot of trouble by taking over a satellite:

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

Most of these are probably completely out of fuel so I wouldnt worry about this.

And even if it had fuel, making it collide with something will be tough. And even if you do that, it's happened before without going all Kessler, although that doesn't mean it can't happen the next time.

If I learned anything but watching The Martian, it's that the law of the sea applies in space. So a nonoperational satellite would be subject to salvage rights?

You should probably qualify that with a Andy-Weir-is-not-a-lawyer disclaimer. There are a few space treaties that probably supersede some elements of "maritime" law.

have you ever tried an orbital rendezvous in KSP?

I am amazed by the Nonoperational/Operational ratio.

It takes a lot of fuel to deorbit something in a controlled manner.

I'm curious, at what appears to be GEO (Geostationary Earth Orbit) there is a ring of green "operational" satellites that align with the equator, then there is a "belt" of non-operational satellites that seem to have spread out from them.

1. Is this because the non-operational ones can no longer station keep and slowly spread out?

2. Why are they in a belt shape?

3. Why is the belt not centered on the green ring? They seem to be all "moving" in the same direction? (When I looked at it, their orbits tend to "dip" south while above the western hemisphere and north while above eastern hemisphere)

The belt shape is an aggregate. Each individual orbit's plane must contain the Earth's center. So the "belt" is an aggregate of many orbits at various inclinations relative to the equator.

Geostationary satellites are boosted into a graveyard orbit at the end of their lives.

I believe it's due to the point of ascension changing. With the earth tilting at 23.5 degrees, a GEO orbit also has to be at that angle relative to the sun. Once they are no longer operational, they will stay at that 23.5 degree angle, but the point of ascension will drift as the altitude (and therefore the orbital period) changes.

Can someone explain why there are so many satellites in a cylindrical section far from the earth and not much in-between it and the earth?

That is geostationary orbit. The active satellites are in circle along the equator while the inactive ones are in wider band outside of geostationary orbit.

There's only a few weather satellites. That surprises me. You'd think there was a lot of demand for something like that?

A single weather satellite can cover a huge chunk of the Earth. You don't need that many for complete coverage.

Does it include military/spy satellites? If not, then there's likely even more satellites both operational and non up there.

[Edit] Scanning the skies above Russia and China for satellites with a non-specified mission doesn't bring up a single US satellite. So it appears that this data does not include spy satellites.

If you click the 'X' next to ComSpOC - removing the filter - there are a TON more satellites. What is that filter and what are all the additional satellites?

It's their company's tracking repository, which is an alternative to the Joint Space Operations Center's (JSPOC) repository.

Who remembers NASA's J-Track?

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