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Questions tagged [jpl-horizons]

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

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13 votes
1 answer
410 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/...
1 vote
1 answer
118 views

Meeus on the Positions of the Satellites of Jupiter

Ex. 44.a of Meeus Astronomical Algorithm, Second Edition, provide the position of the Galileans on December 16 1992 at 0h UT (p.311/488). Procedure 1: For Io, in terms of the Jupiter's equatorial ...
3 votes
1 answer
394 views

What was Chang'e-2's 3D orbit in space? (since it's not in Horizons)

edit: A simple web search in Chinese may turn up something, but I don't know anyone personally who is both both fluent and interested in space exploration. This is a pretty cool orbit - there must be ...
1 vote
1 answer
190 views

Distance between Sun and Earth using JPL horizons

Using the JPL Horizons app at https://ssd.jpl.nasa.gov/horizons/app.html#/ would someone help to calculate the distance between the Sun and the Earth say 1 May 2023 00:00 UT? I used the following for ...
1 vote
0 answers
61 views

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 ...
9 votes
3 answers
594 views

Are there any sources with high-confidence state vectors for GRAIL-A?

I have been experimenting with propagation of Moon-orbiting satellites. In particular, of GRAIL-A. In order to obtain state vectors to use as starting points for my propagation, and to compare the ...
5 votes
0 answers
175 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 ...
4 votes
0 answers
78 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 ...
3 votes
1 answer
298 views

Horizons ephemeris - how did they calculate that “Keplerian GM” value?

I’ve been playing with the NAIF’s SPICE library for some time (CSPICE in particular). In order to obtain the state vector of an asteroid from its osculating elements, I’m calling the “conics_c” ...
3 votes
1 answer
120 views

Why does Earth's North Pole RA flip by ~180 deg around AD2000 relative to SSB? (JPL Horizons data)

Using JPL's Horizons API I see that the Earth's North Pole RA flipped by ~180 degrees quite suddenly around AD 2000. It was pretty stable around 180deg for at least 1000 years prior, and then remains ...
4 votes
0 answers
64 views

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). ...
5 votes
2 answers
205 views

Why is there a 38.6 km Earth-Moon distance difference between Ephemeris types "Observer table" and "Vector table" on Horizons Web Application?

The image above is a screenshot from Horizons Web Application with the Ephemeris type: Observer Table. It shows the distance (delta) from the geocentric observer location to target Moon on April 15, ...
6 votes
4 answers
919 views

Access to Chebyshev coefficients from JPL ephemerides

I want to generate an ephemeris file containing the Chebyshev coefficients, similar to how we can generate ephemeris file of positions with Horizon tool (https://ssd.jpl.nasa.gov/horizons/app.html#/). ...
18 votes
2 answers
2k views

How can I derive an mass/size estimate of an asteroid from JPL parameters?

I'm looking for a list of objects with a semi-major axis between 0.95 AU and 1.05 AU that are probably larger than 1 km in diameter. For this, the JPL Small-Body Database Search Engine seems to be ...
4 votes
2 answers
249 views

How to calculate earth's precession using JPL Horizons System?

I'm new to JPL Horizons and understanding how to use the tool efficiently. I'm looking to extract earth's precession data and understand where we are in the current cycle. I understand we progress 1 ...
0 votes
0 answers
45 views

Astroquery is returning very different semi major axis compared to one in https://ssd.jpl.nasa.gov/sats/elem/

...
3 votes
1 answer
297 views

Determining the spacecraft position vector with respect to ICRF frame for Venus flyby

For an interplanetary mission design to Saturn, I have considered doing multiple gravity assists starting with Venus. I am using the JPL Horizons ephemeris and ESA Lambert Solver. I have the velocity ...
6 votes
0 answers
376 views

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 ...
2 votes
0 answers
99 views

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 ...
11 votes
3 answers
3k views

How to calculate the planets and moons beyond Newtons's gravitational force?

The question Calculating the planets and moons based on Newtons's gravitational force was pretty much answered with two items: Use a reasonable ODE solver; at least RK4 (the classic Runge-Kutta ...
1 vote
1 answer
197 views

How can I find the old reference orbit for JWST (from 2014) and get AltAz positions from Earth without learning Spice? Can Horizons do it? Can Python?

In this ancient 2017 answer to What happens to JWST after it runs out of propellant? I've plotted an eleven year long reference orbit for JWST that was available form Horizons at the time. Now that ...
15 votes
1 answer
3k views

Where to find the best values for standard gravitational parameters of solar system bodies?

Where can I find the best values to use for standard gravitational parameters of solar system bodies for numerical simulation experiments? Here are two sets I've put together. The first set is from ...
2 votes
2 answers
233 views

Why hasn't DSCOVR's trajectory determination been updated in JPL's Horizons after 2015-Aug-4?

I tried to download orbital positions for the DSCOVR spacecraft in its Lissajous orbit around Sun-Earth L1 from JPL's Horizons web page but I was surprised to see the following! No ephemeris for ...
5 votes
2 answers
699 views

Juno's original orbit around Jupiter - is this apsidal precession? If so, need expression

Below is a plot of Juno's originally planned orbit around Jupiter, extracted from JPL Horizons. It's shown in J2000 ecliptic coordinates, centered on the Jupiter barycenter. It turns out the orbit is ...
9 votes
3 answers
2k views

Getting state vectors from JPL Horizons ephemerides

I'm simulating the Sun-Earth-Moon system by numerical integration of equation of motion. I've confused a little bit in JPL Horizons ephemerides. Could anyone explain (if possible, on pictures), how ...
2 votes
2 answers
942 views

Is it posible to convert JPL Horizons Vectors to ECEF?

I'm needing to accurately find the sun and moon position in ECEF and I'm wanting to make use of JPL's Horisons VECTORS to do this. What data should I export from the web interface and how should I ...
0 votes
1 answer
212 views

How can the data rate be increased in noisy outer space?

What can we do to improve the data rate in outer space? I see that there are some noise sources that affect the signal quality between ground stations & deep space. As I've read so far in various ...
3 votes
2 answers
181 views

Generating JPL HORIZONS parameters for use with JPL HORIZONS itself

I want to be able to calculate RA/Dec for a given body with JPL HORIZONS, using a heliocentric specification of the orbital elements for a small solar system body (say, Apophis), but instead of using ...
1 vote
1 answer
266 views

Was the famous SPICE package of programs, utilities and data kernels named after "Melange" found on the planet Arrakis?

This question is NOT about a fictional planet: This question is about NASA JPL history and the naming of SPICE. It is not primarily about the fictional planet Arrakis nor the fictional drug Melange ...
3 votes
1 answer
282 views

Should coordinate transformations from J2000 to ITRF93 in quaternions be cyclic?

I used SPICE's pxform at an interval of epochs to determine the transformation from J2000 (inertial) to ITRF93 (Earth body-fixed) frame. Then, I converted these rotation matrices to quaternions with ...
3 votes
1 answer
138 views

Why aren't there any trajectories for the Viking missions in JPL Horizons' database?

Horizons has calculated trajectories for deep space spacecraft, including six objects related to Apollo 8 through 12. See an (old) list in the currently unanswered question What was Chang'e-2'...
4 votes
2 answers
188 views

How can I know if NASA Horizons output is measured, calculated, estimated or what-else?

This link allows downloading from NASA Horizons server data about the distance of a body (OSIRIS-REX spacecraft ) from the Sun (see link here): How can I know how the distance is obtained? Is it ...
3 votes
1 answer
695 views

How exactly to use astroquery.jplhorizons to get the state vectors of Mercury and the Parker Solar Probe?

In the question Is the Parker Solar Probe's semimajor axis being so close to that of Mercury's just coincidence? Does it help somehow? I used a Python script to plot the heliocentric orbit of the ...
5 votes
2 answers
1k views

How is the Chebyshev method used by JPL?

In the DE packages, NASA gives us a series of coefficients for the Chebyshev approximation. As I understand it, those approximations are given by a series of polynomials $T_n$ for the interval $[-1,1]$...
1 vote
1 answer
526 views

Why is the highest speed that Voyager 2 achieved from the Jupiter gravity assist not at perijove?

I plotted some data of the speed of Voyager 2 for various times (around the Jupiter flyby) and noticed that the highest speed that Voyager achieved was not at perijove and was wondering why this might ...
18 votes
2 answers
2k views

Is this what station keeping maneuvers look like, or just glitches in data? (SOHO via Horizons)

I've been enjoying the JPL Horizons web interface and after I discovered the incredibly extensive database associated with SOHO (Solar and Heliospheric Observatory, also see sohowww.nascom.nasa.gov) ...
0 votes
0 answers
62 views

Where are post-2017 EPIC images of Earth and the DSCOVR spacecraft coordinates available for download?

I tried to download orbital positions for the DSCOVR spacecraft in its Lissajous orbit around Sun-Earth L1 from JPL's Horizons web page but I was surprised to see the following! No ephemeris for ...
2 votes
0 answers
113 views

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 ...
1 vote
2 answers
195 views

Possible idea for a simulation in orbital mechanics using data from the JPL [closed]

I have to write a research essay and have decided to write it on orbital mechanics where I would use data from the JPL to perform an experiment (simulation). I was thinking of using the location data ...
2 votes
2 answers
541 views

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 ...
1 vote
1 answer
105 views

How to find instantaneous mass of a central body that results in a given osculating orbit?

This question was underspecified, so I'm going to try again. Osculating orbital elements are Keplerian elements of a hypothetical orbit around a specified center which would be tangent to a specified ...
4 votes
1 answer
168 views

Does JPL's Horizons have better MU69 state vectors for the New Horizons flyby somewhere?

Today I downloaded the state vectors for New Horizons and MU69 Arrokoth and subtracted their positions. The two new get closer than about 596,000 kilometers. The New Horizons output header says: <...
1 vote
2 answers
294 views

What's going on with NASA's Solar System Dynamics?

JPL's Horizons web interface generates the following orange announcement: IMPORTANT: The SSD Announcement email list is now available. Major changes are coming in the near future, including possible ...
1 vote
1 answer
125 views

JPL ephemerides: effect of Saturn, Uranus and Neptune

According to the Folkner ( Folkner et al, 2014, The Planetary and Lunar Ephemerides DE430 and DE431, IPN Progress Report 42-196 • February 15, 2014), JPL ephemerides consider the following effects: ...
2 votes
1 answer
112 views

What time is NASA using for Horizons web output?

Here's an example of some output from JPL's Horizons web interface. NASA does not (appear to) specify which GMT is at those hours that the specific transits occurred, or at least I can't find it. ...
15 votes
2 answers
1k views

Why is the sidereal period of the Earth 362.392667 days?

Using JPL's Horizons API I can look at the orbital elements for the EM Barycenter wrt the Solar System Barycenter at J2000. The output looks like this: Watch for the PR (Sidereal orbit period) ...
2 votes
1 answer
413 views

Rotation matrix from J2000 to ITRF2008

I want to rotate a vector from the inertial J2000 frame into ITRF2008. I am using the NASA SPICE library, which provides a rotation matrix from J2000 to ITRF93 (they plan to upgrade the library to a ...
0 votes
1 answer
356 views

How to find Horizons ephemerides or Spice kernels for the cis-lunar halo orbits of the Themis B & C) spacecraft?

The Themis spacecraft B and C have been renamed ARTEMIS P1 and P2 and moved around in cis-lunar space from Earth orbit to Lunar orbit. This transfer involved libration point orbits, as discussed in ...
4 votes
0 answers
702 views

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 ...
3 votes
1 answer
492 views

Why are JPL using this expression to emulate Schwarzschild orbits?

From the documentation ”Formulation for Observed and Computed Values of Deep Space Network Data Types for Navigation ” expression 4-61 on page 4-42 it can be seen that JPL uses the following ...