Reference
Passes: when a satellite crosses the sky over a place
import { … } from "@johnmorrisdotca/chikyu-earth/passes";Exports
| Name | Kind | What it is |
|---|---|---|
Compass | type | The sixteen points of the compass, the words a pass table uses for a direction. |
compassOf | function | The compass word for a direction. |
ESTIMATED_CROSS_SECTIONS | constant | The average cross-sections, in square metres, that this package assumes for the bright satellites it names by NORAD number: the ISS (25544), China's Tianhe (48274) and the Hubble Space Telescope (20580). |
findPasses | function | Every pass of the satellites over a place in a span of time, the ones a person can see or all of them. |
GroundPoint | type | One point of a satellite's ground track: the place on the Earth straight under it. |
groundTrack | function | The places straight under a satellite from one moment to another: its ground track. |
magnitude | function | The apparent magnitude of a satellite, treating it as a sphere that reflects light evenly: the standard magnitude, dimmed by the distance (5 magnitudes for every tenfold) and by how little of it the Sun lights from where the watcher stands (the phase angle, 0 when the Sun is behind the watcher and the satellite is fully lit, 180 degrees when it is all dark). |
Observer | type | Where the watcher stands: degrees of latitude (north is positive) and longitude (east is positive), and the height above sea level in metres (0 by default). |
PassOptions | type | What findPasses may be asked. |
passPath | function | The satellite's track across the sky for a pass: a point every stepSeconds from the pass's start to its end, with the first and last on the start and the end. |
PassPoint | type | One moment of a pass: when, which way, how high and how far. |
PassReason | type | Why a pass is or is not visible: visible; daylight (the watcher's sky is too bright for the whole pass); shadow (the sky is dark enough but the satellite is in the Earth's shadow for all of it); faint (it is lit and the sky is dark, but it is fainter than the limiting magnitude). |
PassWindow | type | The span of time to look in: a pass is listed when its highest point is in it. |
PathPoint | type | One sample along a pass: when, where in the sky, and whether the satellite is in sunlight (the track is drawn solid there and dashed in the shadow). |
satelliteAt | function | Where one satellite is in the sky over a place at one moment, and what the light is like: its direction and height, its distance, whether the Sun lights it, how high the Sun is, and how bright it looks. |
SatellitePass | type | One pass of a satellite over a place: it comes up through minAltitude, reaches its highest and goes down below minAltitude, with whether and how it can be seen. |
skyAt | function | The name of the sky for a Sun altitude. |
SkyLabels | type | The words on a sky dome: the four directions and the three marks on the track. |
SkyName | type | How dark the watcher's sky is, by the Sun's altitude: day (the Sun is up), civil twilight (the Sun is below the horizon by up to 6 degrees: the brightest stars and planets show), nautical (6 to 12 degrees), astronomical (12 to 18 degrees) and night (more than 18 degrees below). |
SkyOptions | type | What skySvg may be asked. |
skySvg | function | A pass drawn on the sky as an SVG string: the horizon as a circle, the zenith (straight overhead) in the middle with rings at 30 and 60 degrees, north up and east on the left (the way a star chart is held over your head), and the satellite's track as a line that is solid and warm where the satellite is in sunlight and dashed where it is in the Earth's shadow, with its start, highest point and end marked. |
STANDARD_MAGNITUDES | constant | The standard magnitudes this package assumes for the satellites in ESTIMATED_CROSS_SECTIONS (standardMagnitude of each, with the default albedo). |
standardMagnitude | function | The standard magnitude of a satellite worked out from its size: the brightness, from 1000 km away with half of it lit by the Sun, of a sphere with the same average cross-section that reflects albedo of the light that falls on it evenly in every direction. |
sunAltitude | function | The Sun's altitude over a place at a moment, in degrees (above 0 the Sun is up). |
VisiblePart | type | The part of a pass a person can see: from when the satellite is lit, the sky is dark enough and it is bright enough and above the lowest altitude, to when one of them stops; and the highest point of that part. |