How COSMOS is built, and the rules every layer has to pass

Measured facts

Vertically integrated bodies

15 navigable destinations

Measured catalogue sources

371,766

Ephemeris coverage

2020-01-01 00:00 TDB through 2040-01-01 00:00 TDB

Renderer

TypeScript, React 19, Three.js r185, WebGLRenderer with logarithmic depth

State precision

float64 SI metres, seconds and radians inside explicit frames

Physical state is never the display scene

There is no universal floating-point scene in COSMOS. Canonical state is stored as float64 SI values inside a named reference frame, and every renderer rebases its origin near the camera or the current focus before uploading positions. That is why a metre-scale surface view and a kiloparsec-scale Galactic view can exist in the same continuous journey.

Display frames are explicit: ecliptic J2000 for the Solar System, an ICRS display basis for the stellar volume, and a galactocentric frame for the Milky Way model. During each handoff the outgoing renderer stays live until the incoming one reaches full opacity, so the shell, labels and selection never remount.

Time is bounded and never extrapolated

Sun, Moon, planet and Pluto positions are cubic-Hermite interpolations of geometric JPL Horizons state vectors in Earth-centred ecliptic J2000.0 / ICRF (origin Earth centre (399)), covering 2020-01-01 00:00 TDB through 2040-01-01 00:00 TDB. Every archive was validated against held-out Horizons epochs before release; the worst held-out position error across the primary objects is 67.7 km.

The Galilean moons use their own Jupiter-centred archive with per-moon cadence (io 0.08333333333333333 day, europa 0.125 day, ganymede 0.25 day, callisto 0.5 day) so that local precision is preserved. Requesting an epoch outside the declared window is rejected rather than approximated.

UI time is date-oriented UTC while ephemeris state is TDB. COSMOS applies a fixed modern 69.184-second offset for display and does not predict future leap seconds. "NOW" means the present epoch inside the recorded archive: it is not live imagery or a live scientific service call.

Provenance is data, not editorial text

Every provider returns its provenance with the payload, and a renderer cannot rewrite the category. A visible layer without a complete provenance record is a release blocker. These are the categories COSMOS distinguishes:

• Dataset version, resolution, spatial and temporal coverage, datum or frame and all transformations are recorded before release.
• Missing coverage stays missing or falls back to a named lower-resolution dataset. It is never filled with generated scientific detail.
• "Live", "current" and "real-time" are used only when acquisition and delivery semantics actually support those words.
• Lighting enhancement, cinematic compression, interpolation, reconstruction and simulation are visible user-facing states.

observational

A direct calibrated observation with a declared instrument and processing chain.

observational-composite

Observations combined, resampled, colour-adjusted or gap-filled into a scientific mosaic. Blue Marble and the LROC colour map are composites, not single photographs.

radar-derived-observation

Measured radar or backscatter products, never presented as visible-light ground photography.

processed-observation

Calibrated observations whose spectral band and transformations are disclosed. EUV solar images are processed observations with scientific false colour.

measured-catalogue-data

Published catalogue fields tied to a named release. Gaia astrometry and IAU feature coordinates are in this category.

derived-scientific-model

A reproducible calculation from scientific constants or measured inputs. The Milky Way reconstruction and interpolated Horizons states are derived.

numerical-simulation

The result of a declared numerical model with stated initial conditions.

artist-educational-representation

Explanatory artwork that does not claim measured geometry. Most planet appearance in the current slice is honestly labelled this way.

theoretical-speculative

A hypothesis or speculative visualisation that is not observational evidence.

Native resolution and camera floors

Every imagery provider declares a delivered resolution and a minimum safe approach. The camera will not descend past that floor, because past it the renderer would be magnifying source pixels and implying detail the dataset does not contain. These are the floors currently enforced across the navigable bodies:

Sun

1.08 mean radiieducational geometry

Mercury

2,679 km from the body centre (240 km above the mean-radius surface)surface provider

Venus

1.08 mean radiieducational geometry

Earth

6,551 km from the body centre (180 km above the mean-radius surface)surface provider

Moon

1,772 km from the body centre (35 km above the mean-radius surface)surface provider

Mars

3,790 km from the body centre (400 km above the mean-radius surface)surface provider

Jupiter

2.5 equatorial radiiatmospheric map

Io

1.08 mean radiieducational geometry

Europa

1.08 mean radiieducational geometry

Ganymede

1.08 mean radiieducational geometry

Callisto

1.08 mean radiieducational geometry

Saturn

4.0 equatorial radiiatmospheric map

Uranus

1.08 mean radiieducational geometry

Neptune

1.08 mean radiieducational geometry

Pluto

1.08 mean radiieducational geometry

Measured, derived and modelled stay apart

Measured: 371,766 individual Gaia DR3 sources, each with its own astrometry. Derived: the Milky Way reconstruction, whose 230,000 points are weighted density tracers from cited parameters. Contextual: an AllWISE infrared sky overlay that is a real observation but has no positional parallax. Illustrative: planet appearance where no observational product is validated, drawn as a labelled proxy.

These four kinds never share a label, a styling convention or a provenance category in the interface. The separation is the point of the project.

What is deliberately incomplete

• Five bodies (Venus, Uranus, Neptune, Pluto, and the Sun) have no observational appearance integrated yet; their imagery contracts remain pending validation.
• Only four Galilean moons and two named surface features are navigable, and no other satellite system is implemented.
• There is no terrain displacement anywhere: every body is a mean-radius sphere or a reference oblate ellipsoid.
• No mutual shadows, no physical ring-particle rendering beyond measured annuli, and no orbit path geometry are drawn.
• Lunar libration and precision lunar orientation are not implemented; the Moon’s orientation is explicitly approximate.