# Questions tagged [skyfield]

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### Is 75 meters an exceptionally close distance for two satellites to pass at >6,000 m/s?

While researching for this question I ran across something called Celestrak Socrates. I requested the ten closest predicted approaches, and saw distances of closest approach of the order of 100 ...
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### How can I plot a satellite's orbit in 3D from a TLE using Python and Skyfield?

I have obtained a Two Line Element (TLE) of a satellite in Earth orbit from Celestrak at https://celestrak.org/NORAD/elements/ and I would like to use it to calculate an orbit. How can I calculate the ...
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### How to obtain UTC of the epoch time in a satellite TLE (two line element)?

I want to convert the epoch time of a TLE to UTC. At this moment I am less interested in explanations and history - I just want to know quantitatively, with certainty, how to convert. I'm confused ...
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318 views

### Different Earth-centered ICRF positions in GMAT and Skyfield/Spiceypy with DE421

I compared the Earth-centered positions from the Moon in the ICRF (i.e., in GCRF) using three different sources: SpiceyPy (https://pypi.org/project/spiceypy/) Skyfield (https://rhodesmill.org/...
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### How to get earth-centered, earth-fixed coordinates from Skyfield?

I recently started using Skyfield (python) to find (x, y, z) coordinates of things in space. Now I'd like to transform between Earth-Centered, Earth-Fixed (rotating) and Earth-Centered Inertial (non-...
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601 views

### What exactly is the interaction that blocked Juno's data downlink near solar conjunction?

According to Space.com's article Juno Phones Home: Jupiter Probe Reconnects with Earth After 8th Flyby, Juno's recent close flyby of Jupiter and data collection happened while Jupiter was too close to ...
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### Does it even make sense to talk about Mercury's triangular libration points (L4, L5)?

The recent question How much radiation shielding would be required for a habitat at Mercury–Sun L5? got me thinking. There are a large number of disadvantages and challenges to building or putting a ...
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### What is the difference between GCRS and J2000 frames?

What is the difference between GCRS and J2000 frames? Which is commonly used worldwide in satellite communications? I've read a statement here, that ...
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### How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time?

I have obtained TLE information of a satellite from space-track.org for three different times. I am trying to study any deviation of the satellite trajectory from its usual path. Here I am comparing ...
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### Time, UTC, Julian Date, TLE epoch - how are they related quantitatively?

I am trying to understand the relationship (quantitatively) between JulianDate, UTC, and the epoch of Two Line Elements. It's a deep subject, especially if you include relativity, and a long subject - ...
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496 views

### Need help getting the true ICRF coordinates of SOHO using Horizons

In this answer I calculated the approximate angular separation between Mercury and the Sun as seen by the SOHO satellite using Skyfield's method of ...
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323 views

### Was the time of Schiaparelli's landing chosen specifically so the Giant Meter Wave Radiotelescope could listen?

The ESA blog post Listening to an Alien Landing describes the plan to monitor a UHF beacon transmitted by Schiaparelli during it's upcoming descent and landing on Mars (2016-10-19 about 14:45 UT). The ...
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### How can I calculate if a satellite is currently in sunlight or eclipse using pyEphem or Skyfield (preferred)?

I'd like to add this to some existing python scripts to model cubesat battery life and payload temperature but the math escapes me.
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### JPL Horizons original reference orbit data for Juno - how to retrieve now that it's been updated?

Because of the slow helium valve responses, Juno was not instructed to execute the large delta-v maneuver to drop from the ~53 day orbit to the ~14 day orbit originally scheduled for 2016-Oct-19. I'd ...
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### What does it mean to ask for a date beyond epoch time?

I am fairly new to this industry. As I am playing around with a library on Python, ephem, I have encountered an error saying that: ...
529 views

### Asteroid 2013 TX68 March 5, 2016 close approach, and calculating with Skyfield

This NASA webpage describes the close approach of asteroid 2013 TX68 on March 5, 2016 and shows a probability distribution of the point of closest approach based on the only data available at this ...
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### How to (correctly) rotate this data so the Ecliptic is in the XY plane?

When plotting orbits using the Python package Skyfield, the coordinates are barycentric ICRS. This puts the center of mass of the solar system at the origin, but the $\hat{z}$ axis is tilted about 23° ...
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241 views

### How to get lunar L, B, C parameters from the Moon's 3x3 rotation matrix from the Python package Skyfield?

Answers to What are the “Moon L, B, C” angles shown in this solar eclipse simulation? explain that L and B (or "l" and "b") are the "selenographic coordinates of the Moon's apparent center" (latitude ...
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432 views

### How to calculate a satellite LTAN on the basis of Cartesian coordinates in GCRS frame?

I have calculated the Cartesian coordinates of a satellite in GCRS frame using Skyfield package in python. Propagating the sun-synchronius orbit, I want to analyse the change in its LTAN. How could I ...
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### Skyfield, how to use https:// instead of ftp://?

Using skyfield I get the error : OSError: cannot get ftp://cddis.nasa.gov/products/iers/deltat.data because <urlopen error ftp error: TimeoutError(10060, 'Ein Verbindungsversuch ist fehlgeschlagen, ...
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### How to calculate cone angle between two satellites given their look angles?

I have the azimuth, elevation and distance of 2 satellites relative to a ground station, defined by latitude and longitude, as I've discussed in my previous question. I'm using the satellites' TLEs ...
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### satellite ground track calculation

I'm trying to calculate the ground track of an earth-orbiting satellite (Longitude, latitude) I found this handy way on the documentation but it's good when trying to find a single point what if I'm ...
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### Why can n2yo somehow interpret this TLE but Skyfield can't? Why does it return nans and zeros for position?

@Rafa pointed out that there is at least one officially released TLE for the JWST mission after it left Earth orbit, and here's the latest one at n2yo.com: ...
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### How big is Mars as seen from Phobos?

If I were standing on the surface of Phobos looking at Mars, how big would it appear in the sky? Would it be like one hand at arm's length? Or take up like a third of the sky?
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### Python - Beyond Orbit raises TleParseError for valid TLE [closed]

I've been using the example script for ground track from the beyond library documentation. I've been using TLEs from Celestrak's set of NOAA satellite TLEs, located here. This was working fine until I ...
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### Better way to get approximate ground track for a satellite using Skyfield?

I wanted to make a quick ground-track plot, so I used the Python package Skyfield to propagate a TLE and return Earth-Centered Inertial coordinates. Then I created a ...
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299 views

### How to calculate the phase angle between satellite and sun with the use of skyfield

With the discussion that took place on answer(s) to How to calculate cone angle between two satellites given their look angles? I would like to ask if my proposal solving that question works like ...
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510 views

### How to satellite-to-site range given site coordinates and satellite ephemeris?

How can I calculate the distance of a position on earth to a satellite (for example a GPS satellite)? The satellites position is exactly known by its ephemeris data. In a related question I've asked ...
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### Ephemeris output from Skyfield

Is it possible to use Skyfield to propagate a TLE forwards and then output its ephemeris, rather than geometric x,y,z at some point in the future? I've worked through the examples in the API and may ...
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### Local observer coordinate system at satellite panel (LVLH coordinate system)

In skyfield I want to calculate alt-az distance from one reference satellite to next (for antenna pointing simulation). My current workaround is to create the reference observer at sat1 height and ...
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### Ephemeris for lunar body-centered body-fixed coordinates?

I'm going to try to do a modest simulation of the Moon's libration as seen from the Earth (geocenter), similar to the technical one's I've shown in this question. I'll do it in Python and render it in ...
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### How to find/extract the semi-major axis from a TLE with Skyfield?

I have a TLE: 1 33591U 09005A 21024.46740879 .00000049 00000-0 52095-4 0 9997 2 33591 99.1927 41.5349 0014084 172.6670 187.4709 14.12449679616592 And I would like ...
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### Calculating Which Satellite Passes are Visible - Need help

I am a beginner Python programmer. I am trying to get the code in the article "Calculating which satellites are visible" to function without success. My plan is to identify satellites that ...
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### How can I plot a satellite TLE from its orbital parameters using python and skyfield? [closed]

I have a function that uses TLEs (Two-line elements) from Celestrak to plot the visibility of a satellite in Python. Is there a method with skyfield or poliastro to plot a TLE from given orbital ...
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1 vote
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### Has Skyfield or any other SGP4-capable open-source Python package yet wrapped/implemented the new, improved SGP4 (version 8+)?

The first release on Github was in 2014. I have noticed Brandon Rhodes has contributed quite a bit to the Skyfield source code, so I will tag him here and in a comment. EDIT: I changed the title to ...
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1 vote
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### What are the product terms shown here representing an orbit?

I can compute Kepler parameters from a given TLE using Skyfield. I am checking the satellite information from this website and the orbit is represented as  546 \times 548 \text{ km} \times 53.1 \...
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1 vote
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### A dataset for Earth satellite size information?

I am lookin for a dataset where I can find or calculate the size information of an Earth satellite as described in the seconds page of this paper. It is basically the radius of the smallest sphere ...
1 vote
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### What is ephem's body size attribute equivalent in Skyfield?

I am porting some code that uses PyEphem to using Skyfield. Somewhere along the code I use the body's size attribute: ...
1 vote
121 views

### How to convert Geocentric Coordinates to ECEF using Skyfield?

I'm trying to obtain ECEF coordinates from geocentric coordinates and then plot the ground track using the subpoint function. Any advice? My objective is to create an accurate ground track. Additional ...
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1 vote
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### satellite ground track in skyfield

I'm trying to get the geographic location (longitude & latitude of a satellite) converted from the position in space for example: position = (7033.45648791, 178.93192295, 0.00290722) Km. longitude ...
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1 vote
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### calculating satellite position and velocity from TLE

I'm trying to calculate satellite orbit from the TLE set at first, I used several libraries including SGP4, Skyfiled to get the initial position and velocity of the satellite at the epoch time I know ...
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