# Tag Info

## Hot answers tagged pyephem

7

As a new user I cannot comment or tweak the original answer, so I'll try my own. Happy update per any recommendations that come up. @uhoh's answer is close, but a few things to note. The TLE tells us the number of orbits per day is 15.50995519 (line 2 columns 53–63)  \frac{24 \frac{hours}{day} * 60 \frac{mins}{hour} }{15.50995519 \frac{orbits}{day}} = ...

3

A TLE describes the orbit of a body at a single reference point in time, which is called the epoch. It is straightforward to extrapolate the position of the object for some time forward or backward from that snapshot, but beyond that, limitations of the propagation model cause errors to grow, and the position of the object cannot be accurately estimated. ...

2

MEGA note: My answer is totally wrong and should be unaccepted by any means necessary. Luckily @AllenKummer's answer explains why and gives a revised script. This was posted at about 7 AM local time and must have been pre-coffee; the period shown here is only 40 minutes, seeing that it's wrong would have been a no-brainer, which is indeed the state I'm often ...

1

As far as I know, Skyfield itself doesn't contain any tabulated data on astronomical bodies itself†. Instead, it allows you to draw data from other sources. for motion, you select a NASA JPL ephemeris yourself and Skyfield downloads and interpolates the positions and velocities for Earth artificial satellite motion Skyfield downloads TLEs or lets you type ...

1

note: Alas, PyEphem is deprecated, so to plot from TLE's use Skyfield, written/maintained by the same person as PyEphem. I show an example here. Step 1: Convert your orbital parameters to a state vector A state vector is a 6 dimensional vector which is the combination of a position vector $\mathbf{x}$ and a velocity vector $\mathbf{v}$. In a deterministic ...

1

Not necessarily "outdated" as much as simply exactly what the ever-articulate (see also) Brandon Rhodes has written: "X days from the epoch" (unsigned, could be either direction) because TLEs are sometimes post-dated to the future by as much as several weeks, and PyEphem may feel that it is too early to use that TLE as well as too late. note: pyephem (...

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