Keosynchronous orbit with inclinaton >90° ???

[Maelin]

I got offered this contract today:

How can one have a keosynchronous orbit with an inclination of 159.4°? Doesn't an inclination greater than 90° indicate that it is orbiting in the reverse direction to the planet's rotation?

(I wasn't sure if this was a bug with a mod or with the standard contracts, so not sure of a more suitable place to post this)

[Destroyer713]

I've gotten contracts just like that with mostly-stock KSP, so you're not the only one. Could just be a bug in how contracts spawn.

[impyre]

Geosynchronous and geostationary are two different things. Geostationary orbit is a special case of geosynchronous orbit; one in which the inclination allows the satellite to orbit while maintaining position over a certain geographical area. Geosynchronous orbit is simply any orbit with a period equal to the rotation period of the planet (accounting for orbit around the sun of course). Thus, geosynchronous orbits can happen at any inclination... they are just considered less often because they aren't usually as useful for line-of-site properties.

[bitbucket]

I got offered this contract today:

http://i.imgur.com/plH3j1b.png

How can one have a keosynchronous orbit with an inclination of 159.4°? Doesn't an inclination greater than 90° indicate that it is orbiting in the reverse direction to the planet's rotation?

"keosynchronous" just means a 6-hour orbital period. It doesn't say "keostationary," so what they're looking for here is a retrograde orbit.

[cantab]

What would the ground track of a retrograde synchronous orbit look like anyway? I know with a small inclination you get a figure eight, but with an essentially retrograde orbit I've got no idea.

[Deutherius]

What would the ground track of a retrograde synchronous orbit look like anyway? I know with a small inclination you get a figure eight, but with an essentially retrograde orbit I've got no idea.

How I imagine it (the unnecessary part):

I imagine it would look the same as a prograde one (just travelling in the opposite direction, of course). The satellite basically draws a sine wave on the ground. If your inclination is 0° or 180° (perfectly equatorial prograde or retrograde), the frequency of that wave is 0 - it's a line. Increasing the inclination increases the frequency in the interval <0°;90°> and <180°;270°> and decreases the frequency otherwise. The highest frequency achieved is in the 90° and 270° inclination, and how fast the trajectory oscilates depends on the planetary rotation. There is one thing to note however, as the satellite at polar orbit travels across the poles, the ground track "jumps" from one side of the planet to the other - essentially transforming the sine wave into a square wave with rounded edges.

A video to help visualising it (because I suck at words):

What you are probably looking for (an online simulator with ground track visualization):

http://en.homasim.com/orbitsimulation.php

EDIT: Frak, doesn't allow retrograde orbits (or at least I'm unable to create one)... I'll keep looking for a better simulator.

Edited April 4, 2015 by Deutherius

[impyre]

What would the ground track of a retrograde synchronous orbit look like anyway? I know with a small inclination you get a figure eight, but with an essentially retrograde orbit I've got no idea.

The ground track for an anti-normal synchronous orbit would appear just like any other ground track for non-synchronous orbits. The only difference is it's movement relative to the surface would appear to be much higher than other satellites at similar altitudes. Of course, the same holds true for anti-normal orbits when compared to normal orbits at all altitudes.

[Stone Blue]

Simple answer, yes.

0° - 89° would be a normal prograde orbit, 90° a polar orbit, and 91° - 180° would be a retrograde orbit...So think of 159.4°, as a retrograde orbit with a 20.6° inclination... (180° retrograde equatorial minus 159.4° prograde orbit).

Does that help?

Edited April 4, 2015 by Stone Blue

[Frybert]

How I imagine it (the unnecessary part):

I imagine it would look the same as a prograde one (just travelling in the opposite direction, of course). The satellite basically draws a sine wave on the ground. If your inclination is 0° or 180° (perfectly equatorial prograde or retrograde), the frequency of that wave is 0 - it's a line. Increasing the inclination increases the frequency in the interval <0°;90°> and <180°;270°> and decreases the frequency otherwise. The highest frequency achieved is in the 90° and 270° inclination, and how fast the trajectory oscilates depends on the planetary rotation. There is one thing to note however, as the satellite at polar orbit travels across the poles, the ground track "jumps" from one side of the planet to the other - essentially transforming the sine wave into a square wave with rounded edges.

A video to help visualising it (because I suck at words):

What you are probably looking for (an online simulator with ground track visualization):

http://en.homasim.com/orbitsimulation.php

EDIT: Frak, doesn't allow retrograde orbits (or at least I'm unable to create one)... I'll keep looking for a better simulator.

Orbiter comes to mind.

[Deutherius]

Orbiter comes to mind.

Well, yeah. I was looking for something online (platform independent, and not a java applet), easy and fast to use and with the ground track displayed on a flat map.

Meanwhile I found a neat android app, Orbit Designer, and totally forgot about everything else. I'll be sitting in a corner playing with my phone if anyone needs me.