Hi everybody, I wonder how astronauts measured the eccentries of planets?

Question

Since all planets have not equal eccentries. I wonder how astronauts measure eccentricities of elliptical orbits?

Answer 1

Astronomers use observations of the planet (visual, or if they know the plane's inclination, the speed with doppler). Then use mathematics and Kepler's laws of planetary motion to find the eccentricity.

http://en.wikipedia.org/wiki/Kepler%27s_laws

Answer 2

You mean astronomer, not astronaut.

Any way, as the first person said, you observe the location of the planet in at least two positions. In practice astronomers use many different observations of the position, more than just two, because of the inherent uncertainties in measurements. From there they mathematically fit the observed points to an ellipse with the Sun at one focus. Once that is done any aspect of the planet's orbit can be calculated.

Answer 3

Astronauts did not measure eccentricity.

The planets eccentricity was not "measured" either. It is calculated through astrophysics understanding of orbits. It is also relatively easy to calculate through observation of a planet's position at 2 points in time relative to the Sun.

Answer 4

Yeah, the first guy was right. Astronauts are too busy studying the effects of alien ant farms on man in the moon marigolds.