Where the data comes from
Orbital elements are published by CelesTrak,
a non-profit that makes space data freely available. A scheduled job fetches the active
catalog once a day and commits it alongside this page, so the page itself never queries
CelesTrak — however many people are watching, the load upstream is one request a day.
If that job stops, the elements go stale rather than disappearing.
How positions are calculated
Positions are propagated from those elements using SGP4, the model ground stations use.
They are calculated approximations, not live satellite telemetry and not exact real-time
positions. Accuracy decays as elements age, which is why they are refreshed daily. A
spacecraft is shown as visible only when the Sun is more than 6° below the horizon in
Seattle and the spacecraft itself is still in sunlight.
How spacecraft are classified
Every object on this map is a satellite. The shapes — imager, servicer, tug,
broadband slab and so on — describe what each one does. Those descriptions are
ours. The official catalog sorts objects into only three kinds: satellites, spent
rocket stages, and debris. Everything shown here is a satellite, so the catalog alone
cannot tell one apart from another. The finer types are assigned by this project, per
operator, to make the sky readable.
How the sky is drawn
The circle is the whole sky as seen from Seattle, Washington: the center is straight
overhead, the rim is the horizon, north is at the top. Color identifies the operator and
shape identifies the type of spacecraft. Trails show roughly where an object has been and
where it is heading over the following minutes.
The Moon and Mt Rainier
Both are reference points, not tracked objects. The Moon is drawn at its true bearing
and elevation with its correct phase, but at perhaps twenty times its real size — at
true scale it would be a single pixel. Mt Rainier sits at its true bearing of 152° and
its true angular width, but its height is exaggerated three times: from Seattle its summit
is only 2.3° above the horizon, which would otherwise be an invisible sliver.
Washington-built, and why it is hard to know
Washington-built means the satellite was made here — either its main body
was manufactured in Washington, or it was assembled here before launch. Where the company
is headquartered does not count. Neither does who operates it, nor where it launched from:
nothing on this map launched from Washington. Parts alone do not count either, so
Washington-made thrusters fly on many satellites we do not include. Knowing this is harder
than it sounds. The catalogs that track satellites record where each one is and who is
responsible for it. None of them record who built it. That has to be gathered by hand, from
company announcements, regulatory filings and trade press. The attributions here are
assigned by this project from documented sources, starting with
GCAT, which
records the factory rather than the parent company. Counts reflect satellites operating in
orbit now, not everything Washington has ever built.
Distance flown*
An estimate, not a measurement. Derived rather than claimed: orbital speed comes from the element set, elapsed time
from the CelesTrak launch date. Both are catalog values. It is an approximation — it
assumes a near-circular orbit at today’s altitude across the whole life of the
spacecraft and ignores drag, orbit raises and maneuvers, so treat it as an order of
magnitude rather than an odometer. Spacecraft without a recorded launch date are left out
of the total rather than estimated.
Time
The clock beneath the sky shows the time the view is drawn for, in Pacific Time and in
UTC. Using the play button or the slider moves the sky forward and the clock moves with it,
so the time shown is always the time that sky belongs to.
Credits and terms
The design and code of this page are not licensed for commercial use. The
underlying data carries its own terms and is not restricted by that. This page sets no
cookies, runs no analytics, and sends nothing anywhere — it is a single static file.
Orbital data is published by
CelesTrak. Manufacturer
data is from GCAT
(J. McDowell), used under CC-BY. Neither organization is affiliated with this project or
responsible for what it shows. Satellite names appear as they do in the public catalog, so
anything shown here can be checked against it.
