About · Product manual

Mission control for the sky

Meridian is a live console for everything above you, from satellites in low Earth orbit to galaxies millions of light-years away. It combines a true 3D model of the solar system, live monitoring of Earth and space, a stargazing planner and mission-analysis tools in one place, all computed for the exact moment you are looking at.

It is not a picture of space. Every position, time and number is measured by a spacecraft or observatory, or computed from published models and catalogues, and every source is credited. Nothing is invented: no random stars, no fake telemetry, no made-up fuel gauges. When a value is an estimate, Meridian says so.

Four jobs in one console

On top of these sits a presentation layer: Viewport shows just the sky, Voyage rides from world to world along real trajectories, and kiosk and screensaver links run unattended on a big screen, in a classroom or on a museum wall.

Getting started

• Your location. Meridian starts from an estimate of your city. For exact rise times and sky positions, open the Observer panel and tap Use my location (the coordinates never leave your device), or search for a city or postal code.
• Find anything. The search box at the top (/) knows every planet, moon, named star, deep-sky object, asteroid, comet and tracked spacecraft. Results say what each one is (“Star · Orion”, “Galaxy · Andromeda”).
• Point and click. Hover over anything in the view to see its name; click it for its card.
• Help is built in. The ? button opens the Guide, with a section for every feature and the full keyboard list.

The 3D view

The main view is where you act. Drag to turn, scroll or pinch to zoom, and use Go to (or the keys 0–9 and M) to jump between the Sun, planets and the Moon. Reset view returns to Earth.

Object cards

Every object opens the same kind of card, in the same order: what it is (type, size, brightness, distance and light-travel time), where it is in your sky (height and direction now, next rise, highest point and set, the Stargazer verdict, what you need to see it, telescope coordinates), how it moves (orbit, period, speed, sunlight or shadow) and one shared set of actions:

• Go there (G) flies to a planet or moon, flies to and follows a spacecraft, asteroid or comet from where it is right now, or centres a star or deep-sky object and zooms to frame it.
• Keep centred (K) and Chase view (T) while following a moving object.
• Stop holding lets go of a star or deep-sky object you went to (dragging the view does too).
• Your sky chart shows it among the stars above your horizon.
• Show at predicted time (re-entries) and Go to closest approach (close approaches) set the clock to the event.

Scale

Compressed scale (the default) keeps the whole solar system in one view: distances beyond Earth are square-root spaced and bodies are enlarged, while directions, order and timing stay true. True scale (S) shows everything unaltered, which is the only way to feel how empty space really is.

Layers

Layers switches every feature on or off: real Earth imagery, night lights, wildfires, smoke, aurora, clouds, city lights, orbits, labels (planets and moons, star names, spacecraft, asteroids and comets, deep sky), the Milky Way, Messier and NGC/IC objects, satellite features, each asteroid family, and which Console panels are shown. Your choices are kept in your browser.

Time

Meridian’s clock is checked against its server’s internet-synchronised time, to about a tenth of a second. The time controls at the bottom of the view play, pause, reverse and step time (← → one hour, with Shift one day), and run it from half speed up to a year per second. Type any date and time to see the sky then; Now (N) returns to the present. Everything, from planet positions to satellite shadows to the Stargazer panel, follows the clock.

Time dock speeds

0.5×, 0.75×, 1×, 1 min/s, 1 hr/s, 6 hr/s, 12 hr/s, 1 day/s, 1 week/s, 1 month/s, 1 year/s.

The solar system

• Planets and Pluto at their true positions on their true orbits (each orbit line is one full period of real positions, so it includes the planets’ pull on each other), turned the way they really face, lit by the Sun. Jupiter, Mars, Mercury and Pluto wear real spacecraft maps; Saturn’s rings come from Cassini’s measurements and cast real shadows.
• Earth with NASA’s Blue Marble and Black Marble maps, relief, a physically based atmosphere, yesterday’s real clouds and a 500-metre close-up of the region in view when you zoom in.
• The Moon from Lunar Reconnaissance Orbiter maps, lit with earthshine on its night side.
• The Sun with today’s real sunspots from NASA’s Solar Dynamics Observatory, turned with the Sun’s rotation.
• Moons: Jupiter’s four large moons, with their shadows on Jupiter when they happen, and Mars’s Phobos and Deimos.
• Planet cards give distance, light time, brightness, phase, apparent size, constellation, the next opposition or greatest elongation, and tonight’s rise, highest point and set.
• Next eclipses lists the coming solar and lunar eclipses with how they look from your location, and jumps the clock to each peak.

Stars, Milky Way and deep sky

• 9,096 real stars from the Yale Bright Star Catalogue, every star you can see with your eyes, at its true position, brightness and colour, with 338 official IAU star names. Search by name, Greek letter (“α Ori”), Flamsteed number or constellation.
• The Milky Way, rendered by us from the light of about 1.5 billion stars measured by ESA’s Gaia spacecraft, with its real dust lanes. Like your eyes, the view dims the stars when you look toward the Sun or a bright planet and lets them return slowly.
• Deep sky: all 110 Messier objects, the best-known galaxies, star clusters and nebulae, marked by quiet outlines at their true size and tilt, plus about 600 more from the NGC and IC catalogues (Layers). Go there centres an object and zooms to frame it; for most Messier objects it then shows the real Pan-STARRS survey photograph, laid on the sky at its true size and orientation. Cards give type, size, brightness and surface brightness, distance for galaxies (from their redshift), a Hubble photo where NASA has one, and when each is best seen from your location.
• Quasars: the 100 brightest, the black-hole-powered cores of galaxies billions of light-years away (Layers), with how long ago their light left and how far away they are now.

Asteroids and comets

About 95,000 real asteroids and comets from NASA/JPL: every known near-Earth asteroid, every asteroid larger than roughly 5 km, the Jupiter Trojans, bodies beyond Neptune and every numbered comet, refreshed monthly and computed on your graphics card. Families are colour coded and switchable. Search any by name or number (“Ceres”, “Bennu”, “Halley”), see its orbit and follow it. Asteroid flybys (in the Earth orbit panel) lists the next close approaches to Earth; tap one to see where it is now and its path past Earth and the Moon.

Satellites

• Tracking: the International Space Station, China’s Tiangong station, Hubble, weather satellites and recently launched satellites, computed in your browser from current orbit data with the standard SGP4 model (to about a kilometre).
• Sunlight and shadow: whether each is in sunlight or in Earth’s shadow, when that changes next and the orbit’s angle to the Sun.
• Satellites over you: visible passes over your location in the next 24 hours, with start, highest point and end, directions and estimated brightness, including freshly launched Starlink “trains”. Click one to see its orbit and follow it.
• Re-entry watch: objects about to fall back into the atmosphere, with the official predicted time, uncertainty window and location, and a flag when a window crosses your sky.
• Close approaches: the official public warnings of two objects passing close in orbit, with the time, miss distance and collision probability; one click jumps to the moment.
• Storm drag: how fast satellites sink from air drag, set against geomagnetic storms over the last two months.
• Ground track: a live map of where the tracked spacecraft are over Earth, with day and night and the points under the Sun and Moon; it opens full screen.

Earth, live

• Yesterday’s clouds from NASA’s weather satellites wrapped around the globe, and satellite imagery for any past date back to 2000 when the clock is set there.
• Last night’s lights, wildfires and smoke on Earth’s night and day sides.
• The aurora drawn on the night side at the strength measured in the last day.
• Whole Earth today: the latest full-disc photos of Earth from the DSCOVR spacecraft, a million miles away.
• See your area from space: a 250-metre satellite image of the region around you, as it looked yesterday.
• Next 24 hours: the Sun and Moon across your sky hour by hour, with your local weather: conditions, temperature and chance of rain.

Space weather

The Space weather panel shows the latest solar flare, any solar storm on its way to Earth and when it arrives, geomagnetic activity (Kp), the solar wind measured a million miles upstream, where the aurora may be visible and how likely it is where you are, and how the upper atmosphere is dragging on satellites. Flares also glint on the Sun in the 3D view.

Stargazer and the sky chart

• Tonight’s best targets: the Moon, planets, bright stars and the best deep-sky objects, each with its best time window and a 0–100 score that weighs height in the sky, darkness, moonlight and forecast cloud.
• Hour-by-hour sky quality until morning twilight, with cloud by layer, how steady the air is (from the jet stream) and the aurora chance.
• On every card: height and direction now, air mass, the angle from the Sun, “See it with” (naked eye, binoculars, small or large telescope) and telescope coordinates for both the catalogue epoch (J2000) and today’s date, ready for a GoTo mount.
• Your sky chart: the whole sky above your horizon at any time in the next 12 hours, with stars, planets, the Moon and deep-sky objects corrected to today’s date, the chosen object’s path through the dark hours, zoom and pan, and click-through to any card.

Launch windows

Launch windows (in the Observer panel) draws the classic “porkchop” plot for a trip to Mars, Venus, Mercury or Jupiter: launch date across, trip length down, and colour for the energy the launch needs, solved from the planets’ real positions. The cheap islands are the windows (Mars every 26 months). Pick any cell for its launch and arrival dates, launch energy (C3), the change of speed needed from low Earth orbit and the arrival speed, then fly that exact trip in Voyage.

Voyage

Voyage (V) is a quiet, cinematic ride as an astronaut from world to world, to where the planets are today, along real transfer orbits. It starts above your city, crosses to each destination with the time acceleration shown on screen, settles into orbit for a slow flyover of real surface maps and ends by looking back until Earth is one faint dot among the stars.

• Tours: Fresh (chosen from what is notable today), Today’s events, Grand Tour, Home (Moon and Earthrise), Inner Worlds, Mars (to Phobos), Asteroid Belt (Ceres and Vesta), or any launch window you picked.
• Gaze: Wander (slow turns between things worth seeing), Destination (locked ahead) or Free (drag to look around).
• Display: a subtle HUD, or full instruments (I): trajectory elements, transfer energy, navigation, sunlight and temperature, light-time delay and which Deep Space Network station would hear you, solar wind and a route map; every value computed, none invented.
• Rear view (B), letterbox, pace and arrival distance, and photo mode (P) for a 4K still stamped with where and when.

Modes, layout and screens

• Your layout: show or hide any panel, the Voyage button and a frame-rate readout under Layers → Interface.
• Unattended screens: #screensaver runs the Viewport with a slowly turning view; #voyage&kiosk runs Voyage with no exit control and restarts its tour a few minutes after the last touch; &span=2 spreads Voyage across two screens.
• On a phone: add Meridian to your home screen to run it full screen like an app.

Keyboard

How accurate it is

• Measured and refreshed every few minutes to hours: satellite orbits, asteroid flybys, space weather, the solar wind, sunspots, clouds, fires, smoke and night lights.
• Computed for the time shown: the Sun, Moon and planets from standard models (to about an arcminute), Jupiter’s moons, eclipses, rise and set times, satellite positions (to about a kilometre).
• Catalogue positions: stars and deep-sky objects at their catalogue positions, corrected to today’s date for your sky.
• Fixed orbits: the 95,000 asteroids and comets follow their orbits without the planets’ pull, refreshed monthly: good to a fraction of a degree in the sky over months.
• Display, not data: only in Compressed scale are distances and sizes altered, so everything fits in one view; True scale is exact.

Meridian is for education and enjoyment. Do not use it for navigation, safety or spacecraft operations, and never look at the Sun without certified eye protection.

Privacy

No accounts, no tracking scripts and no cookies. Your settings stay in your browser. Nearly all data is served from Meridian’s own server; the few services your browser contacts directly (weather for your rounded location, place search when you ask for it, NASA imagery for past dates and close-ups) are listed in the Privacy tab of the Guide, with every data source credited in the Credits tab.