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DiamondGeezer
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Does anyone know how to manipulate the ephemeris data from JPL HORIZONS in order to find out the tangential velocity of a body relative to a topographic center, eg the Sun?
D H said:Use the vector output capability rather than observer (right ascenscion/declination) output. This will give you the position vector and velocity vector in ICRF coordinates of some body relative to some origin. Computing the component of the velocity vector normal to the position vector is vector simple arithmetic.
To access the vectors from JPL Horizons, you can go to their website and use the search tool to locate the specific object you are interested in. Once you have selected the object, click on the "Vectors" tab to view and download the available vector data.
The vectors on JPL Horizons are provided in three formats: Cartesian (x,y,z), ecliptic (l,b,r), and equatorial (RA,Dec,r). You can choose the format you prefer by selecting the appropriate option under the "Table Settings" tab.
Yes, you can get vectors for multiple objects at once on JPL Horizons by using the "Batch Interface" tool. This allows you to input a list of objects and retrieve their respective vectors in a single download.
The accuracy of the vectors on JPL Horizons depends on the source of the data. For solar system objects, the vectors are based on data from NASA's Jet Propulsion Laboratory and are typically accurate within a few kilometers. For stars and other non-solar system objects, the accuracy may vary.
Yes, you can manipulate the vector data from JPL Horizons for your own calculations. The data is provided in a tab-delimited text file, so you can import it into a spreadsheet or use it in your own software. Be sure to review the accuracy and units of the data before using it for calculations.