Heliocentric to geocentric

  • Thread starter PikesPeak
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In summary, to convert heliocentric coordinates to geocentric coordinates for a satellite simulation, you need to use the orientation of the Earth's axis in relation to the sun. This can be calculated by using precession angles and the Greenwich Mean Sidereal Time to determine the satellite's equatorial coordinates. Then, using the GST, longitude along the ecliptic, and apparent right ascension and declination of the sun, you can determine the azimuth and elevation of the satellite in Earth-centric coordinates. This will give you the orientation of the satellite in Earth-centric coordinates. Good luck!
  • #1
PikesPeak
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Hi all,

I'm working on a satellite simulation, and I need to convert heliocentric coordinates to geocentric coordinates. I get the heliocentric coordinates from Celestia for two objects – the Earth and a satellite. The satellite's +Z axis points to the center of the earth, and the +X axis points down the line of travel, so I can get the orientation of the satellite from there.

Since I know the time of the simulation, I can use G. D. Mead’s Fortran routine to get Greenwich Mean Sidereal Time, Longitude along the Ecliptic, and Apparent Right Ascension and Declination of the sun over the earth. I have all of that working.

My question is how to use the data from Mead’s routine to first get the orientation of the earth’s axes, and then the orientation of the satellite in Earth centric coordinates.

Am I heading down the right path? I know this is not that hard of a problem, I just don’t know how to get there.

Thanks in advance!
 
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  • #2
Yes, you are heading down the right path. You need to use the orientation of the Earth's axis in relation to the sun to determine the orientation of the satellite in Earth-centric coordinates. First, you need to calculate the equatorial coordinates of the satellite from the heliocentric coordinates. This can be done using the precession angles of the equator and the ecliptic.Next, you will need to convert the equatorial coordinates of the satellite into the Earth-centric coordinates. This can be done by using the Greenwich Mean Sidereal Time (GST) to calculate the hour angle and declination of the satellite. Finally, you need to calculate the azimuth and elevation of the satellite, which can be done by using the GST, the longitude along the ecliptic, and the apparent right ascension and declination of the Sun. With all of this data, you should be able to determine the orientation of the satellite in Earth-centric coordinates. Good luck!
 

What is the difference between heliocentric and geocentric?

Heliocentric and geocentric are two different models used to explain the movements of celestial bodies in our solar system. Heliocentric means that the Sun is at the center of the solar system, while geocentric means that the Earth is at the center.

Who proposed the heliocentric model?

The heliocentric model was first proposed by the ancient Greek astronomer, Aristarchus of Samos, in the 3rd century BC. However, it was not widely accepted until the 16th century when Nicolaus Copernicus published his book "On the Revolutions of the Celestial Spheres".

What evidence supports the heliocentric model?

One major piece of evidence that supports the heliocentric model is the observation of retrograde motion of planets. In a geocentric model, planets would appear to move in a straight line across the sky, but in a heliocentric model, the observed retrograde motion can be explained by the planets' orbit around the Sun.

Why was the heliocentric model controversial?

The heliocentric model was controversial because it challenged the widely accepted geocentric model that had been supported by the Catholic Church for centuries. This challenged the belief that the Earth was at the center of the universe and caused a lot of controversy and debate among scientists and religious leaders.

Which model is accepted by modern science?

The heliocentric model is widely accepted by modern science as the most accurate representation of our solar system. It has been supported by numerous observations and experiments, and is currently used to make predictions and calculations in astronomy.

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