Ike

Ike/Data

Ike is a moon and the only natural satellite of Duna. Ike has steep, rocky slopes and no atmosphere. Ike and Duna are tidally locked due to their proximity and Ike's size. This means that Ike is in synchronous orbit around its parent body, and that each body is only visible from approximately half of its partner's surface. (It would be exactly half, but Ike's slightly eccentric orbit creates regions for which Ike can be seen to set and rise. See Libration, below)

An encounter with Ike is quite likely when approaching Duna, provided the player's trajectory is near the plane of Ike's orbit. This is because Ike's sphere of influence is very high relative to the semi-major axis of its orbit — in fact, no other moon in the game has a larger SOI-to-semi-major-axis ratio.

Stationary orbit around Ike is not possible — it would require an altitude of 1 133.90 km, outside of Ike's sphere of influence. However, since Ike and Duna are tidally locked to each other, a spacecraft in stationary orbit around Duna will see Ike in a near stable, non-rotating position, as if it were in a stationary Ike orbit. It is not perfectly stationary as Ike has both a non-zero orbital eccentricity and a very small orbital inclination.

Although Duna is the game analog for Mars, Ike does not seem to represent Phobos or Deimos.

Geostationary Properties and Libration

Ike's orbit keeps it directly above a short range of Duna longitudes. The average Duna longitude where Ike tends to stay directly above in the sky (at the Zenith) is 3 degrees east, but the exact longitude oscillates between about 0 degrees and 6 degrees east due to the eccentricity of Ike's orbit. This eccentricity also makes Ike appear to grow slightly larger and smaller to an observer on the surface of Duna. The latitude for which Ike is in the Zenith also oscillates between 0.2 degrees south and 0.2 degrees north due to Ike's orbital inclination, making Ike appear to rotate upwards and downwards as viewed from the surface, but due to the extremely small orbital inclination, this effect is nearly imperceptible. These phenomena together are known as libration. Due to the oscillation in Ike's position above the horizon, areas from 90°W to 84°W and 90°E to 96°E on Duna can observe Ike rise and set at least partially across the horizon, as can any areas north of 89.8°N or south of 89.8°S

Traveling from a 50 km Duna orbit to a 10 km Ike orbit requires approximately 435 m/s of delta-V.

Topography

Ike is extremely rocky. Its tallest points are 12.75 km above its lowest, giving it an elevation range over 3 times that of the Mun despite the fact that the Mun has a 54% wider radius and 137% more surface area. The increased elevation and smaller size result in many steep slopes and make landing quite difficult. The bottoms of valleys are among the flatter, safer landing locations.

Ike lacks any visible impact craters. This is strange considering that it has no atmosphere and isn't much smaller than Duna which has plenty of craters.

The ground is dark grey, notably darker than that of other rock moons like Mun, and sprinkled with large rocks when terrain scatters are on. Sometimes the ground doesn't reflect sunlight, which generates an effect where if you're looking at the ground, it seems to be nighttime; if you look up, you can see that it is actually daytime.

Tracking Station Info

Ike is a relatively large, grey object occasionally seen orbiting Duna. Scientists have postulated that Ike is seemingly perfectly positioned to sneakily interfere with any object that presumes to come orbiting near its parent.

Easter eggs

Spoiler:

There is a boulder locked in a polar orbit, roughly 100 cubic meters, with green bands and a monolith. It has no gravitational pull (and is not affected by gravity). It has a flawed collision box, so an attempted landing always results in an explosion of some kind. It's called 'The Magic Boulder' which is it's official name (if you collide with it, you will see a message "Ship crashed into magic boulder"). An example video has been made by youtuber Scott Manley, who maintaned a distance of 8 meters long enough to give viewers an excellent picture of the object. (http://www.youtube.com/watch?v=WJBSea-3DHs)

Reference Frames

Time warp	Minimum Altitude
1×	Any
5×	5 000 m
10×	5 000 m
50×	10 000 m
100×	25 000 m
1 000×	50 000 m
10 000×	100 000 m
100 000×	200 000 m

Gallery

A gravitational assist from Ike can help reduce descent velocity down to Duna's surface.
Ike eclipsing Duna
Ike as seen in the Tracking Station
Ike's sky, with Duna in it at all times as well as Kerbol
A landing party on Ike's surface
Topographical map of Ike
Polar topographical map
A topographic height map of Ike made with the ISA MapSat plugin