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Questions tagged [ephemeris]

An ephemeris provides a means for quickly estimating the positions, and sometimes orientations, of solar system bodies as a function of time.

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JPL ephermeris table

For an interplanetary mission design problem, I am using the JPL Horizons Ephermeris to obtain the state vectors of Venus and Earth. I have selected the Coordinate origin as the body centre of the Sun....
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SPICE GFPOSC is returning incorrect sunrise (and sunset) times for topocentric frames

I cannot get SPICE to produce accurate sunrise times for topocentric frames I specify. I'm using spiceypy to interface with SPICE. As a first test, I set up topo coordinates for the MARE landing site,...
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Orbit ephemeris or visualization for the BepiColombo mission?

Where is it possible to see the progress of the BepiColombo mission in terms of ephemeris and or graphical visualisation? I should add, I've checked JPL Horizons, though its not clear how to specify ...
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What happened to time in 1962? (JPL Horizons changes displayed time from UT1 to UTC for dates starting in 1962)

I was viewing some observer output from JPL's Horizons while writing this answer and I saw this annotation. "Prior to 1962, times are UT1. Dates thereafter are UTC". Presumably users of JPL's ...
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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 $[-1,1]$...
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Calculation of Sun-Satellite and Moon-Satellite distance

I have the coordinates of a satellite in the Earth Centered Inertial frame. I have calculated the Sun-Earth and Moon-Earth vectors using the JPLEphemeris package. Now I have to calculate the Sun-...
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146 views

Difficulty trying to use the SPK file ast343de430.bsp

I'm looking for a NAIF SPK file (these typically end in .bsp) for a bunch of asteroids in the J2000 reference frame. I found ...
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I've almost learned to spell Chebyshev, why has JPL switched to Hermite interpolation for DE438?

According to @ChrisR's thorough answer One caveat however is that the interpolation in DE438 is a Hermite interpolation, and no longer a Chebychev interpolation, so you may need to update your code....
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How does Curiosity know how to point and move it's high gain antenna in real time?

The Curiosity rover has a compact X-band high-gain antenna (HGA) that allows for low data rate communication directly with Earth, but is used mostly for higher data rates to spacecraft orbiting Mars, ...
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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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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 ...
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Interpolate the ephemerides of the Earth

I have a table of state vectors generated from ephemerides of the Earth with time steps of 1 minute. Now I would like to interpolate this to a finer time increments in order to use it as part of an ...
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Any algorithmic models of our solar system to predict positions relative to earth?

I'm looking for a map/model of the movements of our solar system and associated moons. What are the 'best' algorythmic models to represent our solar system. Looking to write a game/edutainment app ...
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Calculating the planets and moons based on Newtons's gravitational force

I am trying to understand how to calculate the orbits of solar system bodies in an n-body framework, based on the pair-wise gravitational interaction between the objects. At present, I am considering ...
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Discrepancy between HORIZONS and SPICE

I am trying to reproduce the output of the HORIZONS system using the SPICE toolkit from NASA, but I am not getting exactly the same results. I am using this script to compute the position and velocity ...
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The Moon's shadow could not possibly look like this — could it?

The NASA Goddard video Tracing the 2017 Solar Eclipse is a visualization of the calculated shape of the umbra during the upcoming August 2017 total solar eclipse, as it moves across North America. ...
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Elevation and Azimuth of satellite in different location

I know the Elevation and Azimuth of the a specific GPS satellite (I have the RINEX files of the station in a specific Location 4.4801,-73.3433; in order to calculate this), but I want to know the ...
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Comparing results with Pyephem

I'm trying to calculate the position of each satellite of the GPS constalation, using TLE files and library pyephem, I want to know the position Elevation-Azimuth. But when I compare with the results ...
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PRN number in TLE files are the same in RINEX files? (in GPS constellation)

I want to compare the position calculated with Pyephem and TLE files, with RINEX files and GPSTK library in a specific date and time, but I have not the certainly if the name of the satellite "PRN ##" ...
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Calculating positions of Moon's ascending and descending nodes from ephemeris files

I am trying to find the position of planets and moon at any specific date which I was able to find using the JPL ephemeris ASCII files. I am however stuck now at finding the positions of the moon's ...
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1answer
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Ground longitude/latitude under a satellite (cartesian coordinates) at a specfic epoch

The script I'm wanting to develop uses the cartesian coordinates (XYZ) from a satellite, and in conjunction with the range, elevation and azimuth from a location, I then take a satellite’s orbital ...
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Satellite Ephemeris File Formats

I'm looking for information on commonly used geocentric artificial satellite ephemeris file formats. I'm working on extending an analysis tool for earth orbiting satellites to add the ability to read ...
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Tracking of Mir space station backwards in time?

Is there a site with the tracking information for the old space station Mir? Or some place with the data location tracking information still available? Maybe even a site with orbital mechanics ...
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What is the exact format of the JPL ephemeris files?

I'm attempting to do some basic planet position calculations using the JPL ephemeris data. The first step is to properly parse the files. Here's my understanding so far: The header file gives a ...
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Is there a way to extract the Chebyshev coefficients for a body from a SPICE kernel?

I want to extract the Chebyshev coefficients for the positions of the Moon and Sun relative to the Earth from a SPICE kernel (mainly because DE430 is too large for me to include in a software package, ...
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How to use “HORIZONS” tool by NASA to get orientation of comet 67P/Churyumov-Gerasimenko axis?

I found this powerful online tool from NASA: http://ssd.jpl.nasa.gov/horizons.cgi#top It allows getting orbital data for the comet, but what I actually need is the orientation of the axis of the ...
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How accurate are modern ephemerides, and how does their accuracy degrade over time?

I was reading about what is involved in making an ephemeris and wondered about this. Feeling I'd read pieces that extrapolated orbits over many thousands of years, I looked for an example and found ...
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How to specify a point along the ephemerides of a comet

I'm working on a tool to simulate comet trajectories. Just the usual method where you place the sun and the planets in their orbits and then solve for the comets' trajectories using the gravitation ...
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1answer
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Do the proper ephemeri yet exist to calculate trajectories to Sedna?

While going through links mentioned in What software can be used to determine deep-space trajectories? and What are the choices today for orbital mechanics simulation software?, I find that a great ...
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Ephemeris data usage in interplanetary trajectory application

I'm trying to write a Mathematica application that allows users to choose their date of departure and time-of-flight for an interplanetary transfer mission (currently only working for Earth-Mars ...