
Spacebook: AGI's near Real-Time satellite viewer - dricornelius
http://apps.agi.com/SatelliteViewer/
======
L_226
This one is pretty good too, and doesn't eat all my RAM -
[http://stuffin.space/](http://stuffin.space/)

------
pierrec
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:

    
    
      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

~~~
molyss
A few interesting things :

The sum of all mission-detailed satellites is lower than the total (even
thought there’s a « no recorded » line

There’s a grand total of 58 surveillance satellites around the earth today ?
Yeah... I think there’s a few missing

------
SanchoPanda
This is wonderful.

If it catches your fancy, I have also found termtrack to be a great way to
fill in a corner of a tmux window.

[https://pypi.org/project/termtrack/](https://pypi.org/project/termtrack/)

------
CSMastermind
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).

They build an open-source WebGL-based competitor to Google Maps' engine.

Patrick Cozzi, the driving force behind the technology is one of both the
smartest and nicest people I've met during my career.

~~~
pedalpete
We use Cesium at [https://ayvri.com](https://ayvri.com) (with some of our own
magic sprinkled in). It is an incredible bit of software, completely agree
with your comments regarding Patrick. He's also the driving force behind glTf
and wrote the book on virtual worlds in webGL.
[https://www.amazon.com/Patrick-
Cozzi/e/B004LGLPIA/ref=dp_byl...](https://www.amazon.com/Patrick-
Cozzi/e/B004LGLPIA/ref=dp_byline_cont_book_1)

------
ascales
[http://www.lizard-tail.com/isana/lab/orbital_decay/](http://www.lizard-
tail.com/isana/lab/orbital_decay/)

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.

------
emptybits

        Total objects:          17,642
        Status non-operational: 15,389
    

Yikes?

~~~
xt00
Yea for sure.. I would hope that there is some rule now related to making sure
things can be deorbited with some scheme relatively easily? For example a
mandatory unit that attaches to the side of your satellite that has a small
antenna only possible to communicate with using a high gain antenna on the
ground that can transmit back using a battery that is only for that unit and
can only command some relays to fire thrusters to de orbit the thing and read
back basic telemetry to help validate what the slow down burn direction is..
anybody know how they accomplish this?

~~~
Nodraak
To deorbit a satellite, you need an antenna (to receive the command),
electricity (working solar panel / battery), working on board computer, fuel,
correct attitude determination. So basically you need a full working
satellite. As soon as one of these element fails, your satellite is dead. At
10-20 k dollars per kg, you dont want to add another satellite to your already
expensive satellite.

Concerning rules, there is some progress, because nobody wants a Kessler
syndrome, too much is at stake. For instance, European satellites are launched
only if they naturally deorbit in less than 25 years (for LEO, of course.
Above a certain height, atmospheric drag is too weak).

~~~
Sanzig
Actually, the newly-proposed FCC rules would require fail-safe deorbit systems
when operating above 550 km and below 2000 km. Above 550 km, most stuff takes
more than 25 years to deorbit, and the NGSO volume below 2000 km is considered
the most useful (and thus most likely to get crowded). These fail-safe systems
should be designed to cause the satellite to deorbit within 25 years of
activation.

[https://docs.fcc.gov/public/attachments/FCC-18-159A1.pdf](https://docs.fcc.gov/public/attachments/FCC-18-159A1.pdf)

The FCC hasn't proscribed exactly what these look like (that's
implementation), but electrodynamic tethers would seem likely.

------
alkonaut
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.

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". [https://en.wikipedia.org/wiki/Two-
line_element_set](https://en.wikipedia.org/wiki/Two-line_element_set)

Here is the current state of the international space station for example as
described in a TLE:

    
    
        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
    

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.

[https://www.celestrak.com/NORAD/elements/visual.txt](https://www.celestrak.com/NORAD/elements/visual.txt)

Once you have the TLE for a satellite which describes where it was a while
ago, you need a function that gives you the _current_ 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
[https://en.wikipedia.org/wiki/Simplified_perturbations_model...](https://en.wikipedia.org/wiki/Simplified_perturbations_models)

Basically current_state = SGP4(old_state, time_since_old_state)

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 [https://github.com/brandon-
rhodes/python-sgp4/blob/master/sg...](https://github.com/brandon-
rhodes/python-sgp4/blob/master/sgp4/propagation.py)

------
jonbaer
[https://en.wikipedia.org/wiki/Kessler_syndrome](https://en.wikipedia.org/wiki/Kessler_syndrome)

~~~
willis936
I hope we get the GPS III constellation up and running before any catastrophic
LEO cascades. Having a self sustaining common clock system that can run for
centuries has a very high scientific value (and really, just a huge value for
any industrial, commercial, and consumer applications).

~~~
GhettoMaestro
From what information are you assuming these will run for centuries? Most sats
have a design life of like 10 to 25 years max. Also keep in mind that station-
keeping and correction data is mandatory to keep the accuracy in check. I
think I read somewhere that after 180 days of un-corrected drift the GPS would
be able to get you within a few km of your target - not meters/feet.

~~~
willis936
I was told by someone who follows theses things more closely than me that
block III GPS would have an inter satellite network that could share clock
information independently of ground control. While looking into it the closest
I could find was references to OCX, which is ground based controls. So maybe
we're not there yet idk.

------
inamberclad
If people want to see some good satellite data, I very much recommend
[https://worldview.earthdata.nasa.gov/](https://worldview.earthdata.nasa.gov/)

------
ilaksh
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?

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.

~~~
wrigby
NORAD tracks everything in space, and works directly with satellite operators
to reduce collision risks on the rare occasion that it could happen.

------
ilaksh
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.

Or is it just a bunch of random tracking efforts with duplication and
incompletion?

~~~
modeless
The data for Spacebook, like almost all public satellite position data, comes
from tracking radars run by the US Air Force. They have a public website and
database with API at [https://space-track.org](https://space-track.org).

I've been working on my own website using the space-track.org API to show you
when/where/how to see satellites in the sky with your naked eyes from your own
backyard. Hopefully launching soon.

------
gchokov
So many dead satellites. Is there solution to that, or is there a problem with
it in the first place?

~~~
panzagl
Most of the current debris comes from an anti-satellite missile test (China)
and 1 collision caused by an out-of-control (Russian COSMOS) satellite. So,
basically stop blowing shit up in orbit and it should be ok.

------
rtkwe
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.

------
Applethief
Wow that's a lot.

------
willis936
Using this I just learned that Beidou's orbit is geosynchronous with a high
inclination. That's a lot of delta-V!

~~~
cfraenkel
Not really. They're launched from a base at 28 deg N. So assuming they launch
due east, you can get to a 56 deg inclination and spend less delta-v than
you'd need to drop the inclination to zero.

------
richk449
Was expecting social media, al la seveneves, but that is much better. I wonder
where the data comes from?

~~~
chrissng
I might be wrong, but I don't think they are data captured in real-time.

Based on a cursory understanding of the AGI STK, these satellite positions are
calculated from ephemeris data which are updated on a regular basis (e.g.
weekly).
[https://en.wikipedia.org/wiki/Ephemeris](https://en.wikipedia.org/wiki/Ephemeris)

~~~
modeless
The ephemeris data is updated approximately daily and also allows you to
predict the satellite's position fairly accurately several days in the future.
Satellites change orbits very infrequently, so it's close enough to real time
for most purposes.

------
zionazhy
so cool

