# Questions tagged [jpl-horizons]

Questions relating to the JPL Horizons solar system data and ephemeris computation service

15 questions with no upvoted or accepted answers
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### 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 does JPL define the exact position of Lagrange points in the real solar system where (I thought that) they can't be defined?

My answer to Does the distance to L2 vary? is The correct answer is "No, they are only mathematically defined when the orbit is circular". but @DavidHammen's answer explains that they can ...
• 149k
163 views

### Positions of asteroids in heliocentric ecliptic (x,y,z) coordinates

I would like to make positions of asteroids in heliocentric ecliptic (x,y,z) coordinates plot for a given date, like in the image below (Matsuoka N. Ryo (CC-BY 4.0)). For that I need so-called state ...
73 views

### What are exactly each of the coefficients in Modified Difference Arrays?

I am looking into the different types of SPK kernels. Type 1 are the so-called Modified Difference Arrays (MDA). The linked document mentions that its reference 163 contains a description of the ...
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### Where to get data for axis of rotation of solar system bodies?

Where can I get data for the axis of rotation of the (major) bodies of the solar system? For each solar system body, I want to get a unit vector of its axis of rotation (at a specified point in time). ...
• 143
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### Sources for SPICE Kernel (SPK) files for asteroids

Besides the official source for SPK files (ftp://ssd.jpl.nasa.gov/pub/eph ...) is there a place where people upload kernels for the smaller bodies in the solar system? I was looking for the Jupiter ...
525 views

### Ecliptic reference frame for satellite orbits in JPL Horizons

I'm trying to get orbital elements for natural satellites of all the plates with respect to their system's barycenters and I don't see how it is possible that using the ecliptic as a reference plane ...
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### What is the inertial heliocentric reference system used by NASA JPL to calculate the ephemerides of Near Earth Objects?

I'm using the website of NASA JPL Horizon system at this link Small-Body Database Query to download a database of orbital elements for NEOs (asteroids and comets). Although I checked the Horizons ...
• 433
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### Where can I find the specific details of a gravity assist space mission?

0 I am writing a research essay where I need to know the specific details of a gravity assist mission such as Voyager 2's flyby of Jupiter for example (but any mission would work as long as it is a ...
695 views

### How to get the coordinates from NASA JPL Ephemerides DE430 ( ECRS) to ECI?

I'm trying to make a software that determines the orbit of a satellite which is affected by the Sun and Moon. The coordinates [x y z] that I have for the satellite are in Eci. For the position of the ...
1 vote
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### Using NASA Horizons with Celestrak Socrates's TLE CDMs?

Has anyone succeeded with getting a list of Collision Data Messages (CDMs) from nice sites like Celestrak in order to feed them into NASA Horizon's ephemeris computation service. These would include ...
1 vote
207 views

### Will these equations give me the approximate apparent RA and Dec using positions from Horizons?

In this answer @DavidHammen showed me how to get coordinates from JPL's Horizons using the Earth's equatorial plane as a reference plane by selecting ...
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1 vote
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### How does JPL calculate Epochs for generating ephemerides?

How exactly do epochs fit into the computational propogation of data of NASA's Jet Propulsion Laboratory and what methods do they use to calculate the properties of those epochs in the first place? ...
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