Questions tagged [ephemeris]
The ephemeris tag has no usage guidance.
24
questions
18
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2answers
3k views
Why does the Earth have a z-component at the start of the J2000 epoch?
When I go to the NASA HORIZONS webpage
https://ssd.jpl.nasa.gov/horizons.cgi
and ask for the VECTOR coordinates of the Earth on 1 January 2000, it tells me that Earth has the following coordinates ...
2
votes
0answers
61 views
How to choose between methods to resample/interpolate ephemeris state vectors? Are there recognized techniques for orbital data?
I have ephemeris data for state vectors of a satellite in a J2000.0 coordinate system. This data is already filtered and cleaned.
The data sample rate ranges between 1 second and 60 seconds, and I ...
1
vote
1answer
91 views
How to calculate the ground track of the Moon's position on the Earth's surface?
I would like to project the Moon's position on to the surface of the Earth, starting with its position expressed as Right Ascension in degrees.
I know that the declination of the Moon corresponds to ...
1
vote
1answer
316 views
How to get ephemeris data for location?
How can I obtain ephemeris data which fits to a specific location? Differently phrased: I need ephemeris data of satellites which orbited a specific location. Is there a document where I can look up ...
2
votes
1answer
133 views
Calculating right ascension for two planets and their separation using python
I am experimenting with the Python library PyEphem for astronomy, and I am trying to recreate/understand some of the basic calculations there.
There is a function called separation that, given two ...
4
votes
1answer
151 views
Why is the time between equinoxes different?
The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse.
Since an ellipse, by definition, is symmetrical with respect to the foci, ...
4
votes
1answer
125 views
Predicting accurate time of local sunrise in mountainous area?
Is there any software which will tell me accurately at what moment any part of the solar disk will become from a specific point on the ground taking account of terrain. I feel like Google maps should ...
1
vote
1answer
91 views
Ephemeris data mismatch between Nasa Horizonz and Astro.com
I have tried to compare the Ephemeris data from Nasa's Horizons with ephemeris
tables from astro.com. And they do not match. Example:
Date: 22th of July 2018. Body: Mars. Time 00:00 UT
Horizons: 309 ...
7
votes
1answer
112 views
What are the problems that need to be taken in consideration when trying to find planetary position by using jpl ephemerides?
I'm currently trying to determine the position of the sun and the moon from jpl ephemeris DE200 which is referred to the dynamical equator and equinox of 2000 and uses tdb time. I am using the j2000 ...
0
votes
2answers
59 views
What is the official classification and naming system of objects in the universe(, or what would my URI look like)?
Poetic human centric approach:
Universe/Laniakea/Virgo/MilkyWay/Sol/Earth/Humans/AndreasT
Little bit more technical:
...
5
votes
1answer
83 views
Which kernel does HORIZONS get the Geometric Albedo from?
I am new to using SPICE and the SPICE Toolkit. My goal is to extract body radius, albedo, and distance from the sun of a number of solar system objects. The tools provided by NAIF are great and I ...
4
votes
1answer
66 views
Where to get rate of change for calculating ephemeris from JPL Horizons
I have a working implementation of Schlyter's method for calculating the Sun's position. I would like to know how Schlyter got the 3.24587E-5_deg in the following calculation for Mercury.
...
1
vote
1answer
189 views
Finding Asteroid Geocentric Longitude and Latitude
I started using the software that comes with Jean Meeus book Astronomical Algorithms. I am now using the updated code from naughter(dot)com/aa.html.
I am able to calculate the heliocentric longitude ...
2
votes
1answer
717 views
where to obtain ephemeris data for geodesy satellites?
Is anyone aware of where one can obtain ephemeris data in Geocentric Celestial Reference Systems (GCRS) coordinates for a geodesy satellite such as LAGEOS (It doesn't really matter which mission)? Or, ...
1
vote
1answer
378 views
Converting Earth Moon Barycenter coordinate to Geocentric coordinate
I have Earth Moon Barycenter coordinate (J2000) generated from VSOP2013 in Astronomical Units,
...
3
votes
1answer
284 views
How to visually chart HORIZON ephemeris
I'm trying to build a 3D model of the Sun, Earth and Moon in in Javascript (using Three.JS, which relies on x,y,z coordinates for all objects) in order to simulate the Aug. 21 eclipse. I've ...
1
vote
1answer
465 views
calculating lunar phases
Given a date, I'd like to return the lunar phase.
Jean Meeus's Astronomical Algorithms book and the many packages like PyEphem that make use its algorithms provide ways to calculate when a primary ...
0
votes
1answer
249 views
How Can I Interpolate Ephemerides?
I have two ephemerides for orbital elements—that is, each contains $a$ (semi-major axis), $e$ (ecc.), $i$ (incl.), $\Omega$ (long. asc. node), $\omega$ (arg. of peri.), $\tau$ (time of peri.), $T$ (...
4
votes
2answers
134 views
JPL DE Documentation
I'm currently trying to write a C++ library that makes accessing binary data from a JPL ephemeris file easier. So far I sifted through the web, trying to find a good and thorough documentation about ...
1
vote
0answers
56 views
Is there an English translation of the Parisian Alfonsine tables
I'm interested in the Alfonsine tables published in Paris in the 1400s. I know there is an English translation of what survived of earlier Alfonsine tables from Castile, but that's not what I'm ...
1
vote
1answer
2k views
How to calculate the current distance between two planets [duplicate]
I'd like to add a feature to one of my apps that calculates the current distance between the Earth and Mars (or any other planet, for that matter). My google searches have led me to statistics of ...
2
votes
1answer
54 views
How can we map masses orbiting the outer Solar System by determining the orbits of planets and smaller objects?
Neptune was discovered 170 years ago with the help of observations of Uranus' orbit. A great demonstration of the scientific principle for its time. Recently, Earth and cis-Lunar based radio ...
5
votes
0answers
49 views
Did the Juno mission locate Jupiter at the same precision as Saturn (4 km)?
Juno's low perijove should be great for measuring Jupiter's gravitational effect on Juno's orbit. Cassini together with VLBI has measured Saturn's location to within 4 km.
Will Was Juno be able to ...
8
votes
1answer
198 views
Exactly what in Saturn has been located to within 4 km precision?
Saturn has been located with fantastic precision thanks to Cassini and VLBI. The location of the 120,000 km diameter giant planet (when defining the 1 bar pressure level as its surface) is known to ...
