| Title: | Configuration of Jupiter's Four Largest Satellites |
| Version: | 1.0.1 |
| Description: | Calculate and plot the configuration of Jupiter's four largest satellites (known as Galilean satellites) for a given date and time (ET - Ephemeris Time). The 'galsat' function returns numerical values of the satellites’ positions. x – the apparent rectangular coordinate of the satellite with respect to the center of Jupiter’s disk in the equatorial plane in the units of Jupiter’s equatorial radius; X is positive toward the west, y – the apparent rectangular coordinate of the satellite with respect to the center of Jupiter’s disk from the equatorial plane in the units of Jupiter’s equatorial radius; Y is positive toward the north. For more details see Meeus (1988, ISBN 0-943396-22-0) "Astronomical Formulae for Calculators". |
| License: | MIT + file LICENSE |
| Encoding: | UTF-8 |
| RoxygenNote: | 7.3.2 |
| Imports: | graphics, png |
| URL: | https://lechjaszowski.github.io/galilean_satellites/ |
| NeedsCompilation: | no |
| Packaged: | 2025-07-19 12:45:48 UTC; lechj |
| Author: | Lech Jaszowski 
[aut, cre, cph] |
| Maintainer: | Lech Jaszowski <lech.jaszowski@interia.pl> |
| Repository: | CRAN |
| Date/Publication: | 2025-07-21 09:51:31 UTC |
Calculate & draw the positions of the Galilean satellites
Description
galsat() is used to determine the positions of the four greatest satellites
of Jupiter (called Galilean satellites). Positions are shown on the plot for any
given time (ET – Ephemeris Time) with respect to the planet, as seen from the Earth.
The galsat() function returns numerical values of the satellites’ positions:
x – the apparent rectangular coordinate of the satellite with respect to the center of Jupiter’s disk in the equatorial plane in the units of Jupiter’s equatorial radius; X is positive toward the west
y – the apparent rectangular coordinate of the satellite with respect to the center of Jupiter’s disk from the equatorial plane in the units of Jupiter’s equatorial radius; Y is positive toward the north
Usage
galsat(year, month, day, hour, minute)
Arguments
year |
Type in the year (integer number greater then or equal 0). |
month |
Type in the month (integer number from 1 to 12). |
day |
Type in the day (integer number from 1 to 31). |
hour |
Type in the hour (integer number from 0 to 23). |
minute |
Type in the minute (integer number from 0 to 59). |
Details
The function is based on algorithms in the book: Astronomical Formulae for Calculators (4th edition), Jean Meeus, Willmann-Bell Inc., 1988
Value
data.frame: 4 observations of 3 variables:
$ moon: chr "Io" "Europa" "Ganymede" "Callisto"
$ x : num
$ y : num
Four rows - each row has the position (x,y) of one moon.
Additionally, the positions of the moons are shown graphically.
Examples
galsat(2025, 10, 13, 23, 30)