This one is pretty good too, and doesn't eat all my RAM - <a href="http://stuffin.space/" rel="nofollow">http://stuffin.space/</a>
Interesting stuff, it appears to be their own data (I'm guessing aggregated from sources like the UN registry and observation). I was curious about the statistics on satellite missions so I put it into a table:<p><pre><code> Operational satellites by mission:
total 2154
Communications 740
Scientific 592
Navigation 135
Technology Development 109
Earth Observation 99
Surveillance 58
Engineering 20
Weather 13
Not Recorded 8
Early Warning 3
Search and Rescue 1
Space Station Flight 1</code></pre>
This is wonderful.<p>If it catches your fancy, I have also found termtrack to be a great way to fill in a corner of a tmux window.<p><a href="https://pypi.org/project/termtrack/" rel="nofollow">https://pypi.org/project/termtrack/</a>
So the Cesium you see at the bottom is actually a new startup they spun out of AGI (note the letter order, very different from AIG).<p>They build an open-source WebGL-based competitor to Google Maps' engine.<p>Patrick Cozzi, the driving force behind the technology is one of both the smartest and nicest people I've met during my career.
<a href="http://www.lizard-tail.com/isana/lab/orbital_decay/" rel="nofollow">http://www.lizard-tail.com/isana/lab/orbital_decay/</a><p>If you want to see how long it takes for satellite orbits to decay in LEO, check this out. Illustrates how quickly some of these satellites would reenter without station keeping.
I made a similar site 20 years ago (an applet, what else) and a lot of people seem to be wondering "how does it work" or "where does the data come from?". I can only describe how I implemented it, but it's probably similar.<p>Data is not "real time" for each satellite in any sense. But since satellites follow orbits, it's enough to have recent state, and you can extrapolate where they are. The data comes from places like NORAD, and has a standardized format called a "Two line element set". <a href="https://en.wikipedia.org/wiki/Two-line_element_set" rel="nofollow">https://en.wikipedia.org/wiki/Two-line_element_set</a><p>Here is the current state of the international space station for example as described in a TLE:<p><pre><code> ISS (ZARYA)
1 25544U 98067A 19238.30917157 .00002323 00000-0 48072-4 0 9991
2 25544 51.6438 13.4147 0007728 328.5901 233.9236 15.50389701186137
</code></pre>
It's mostly opaque but we can see near the end of the second line that at the current orbit means it does around 15.5 orbits per day.
When I implemented my app, I just grabbed some data from a public link with up to date TLE's. Such as this one, for the 100 brightest satellites is a good start for a simple visualization app.<p><a href="https://www.celestrak.com/NORAD/elements/visual.txt" rel="nofollow">https://www.celestrak.com/NORAD/elements/visual.txt</a><p>Once you have the TLE for a satellite which describes where it was a while ago, you need a function that gives you the <i>current</i> state vector for the satellite, given the time delta since the known state. Far from earth this can be done approximately with simple orbital mechanics, but close to earth you need to account for athmospheric drag and also the uneven or "bumpy" gravitational field. At some point someone devised a set of algorithms for this called the simplified perturbations models in 1988 <a href="https://en.wikipedia.org/wiki/Simplified_perturbations_models" rel="nofollow">https://en.wikipedia.org/wiki/Simplified_perturbations_model...</a><p>Basically current_state = SGP4(old_state, time_since_old_state)<p>Luckily, these functions were released together with a Fortran implementation, so porting it to whatever language you want is fairly straight forward. Here is an example port of SGP4 to python <a href="https://github.com/brandon-rhodes/python-sgp4/blob/master/sgp4/propagation.py" rel="nofollow">https://github.com/brandon-rhodes/python-sgp4/blob/master/sg...</a>
If people want to see some good satellite data, I very much recommend <a href="https://worldview.earthdata.nasa.gov/" rel="nofollow">https://worldview.earthdata.nasa.gov/</a>
Are there standard libraries or agencies or something for aggregating the latest data and then based on your satellite's planned trajectory, ensuring that you aren't getting too close to another satellite?<p>I am guessing that space is pretty big even in low earth orbit and so probabilities are small even with thousands of objects. But even so, if you are spending millions of dollars, you would want to have some idea rather than just keeping your fingers crossed.
Is there a global database or protocol or blockchain or something where satellite positional data is aggregated? Like if you are launching a satellite then you log into a website or something and enter the planned orbit. Or something.<p>Or is it just a bunch of random tracking efforts with duplication and incompletion?
What's neat is you can see the actual Starlink chain and a few other defined satellite trains. I'd link to it but I don't see a way to link directly to a particular satellite.