Orbit/Legends

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"We are approaching the planet Yavin. The Rebel base is on a moon on the far side. We are preparing to orbit the planet."

―The Death Star intercom announcing the Battle of Yavin^[1]

An orbit was the state of an object moving around a celestial body. Around a planet, a starship or space station in orbit held its position outside or just within the world's outer atmosphere. The completion of one orbit was known as a revolution. The Infinite Empire's chronological circuitry, which could be installed into Rakatan guardian droids such as the Overseer on Dantooine, could detect how many revolutions have taken place and were used as a dating device. By the time of the Jedi Civil War, the Overseer had worked as a Rakatan guardian droid for ten revolutions, which Bastila Shan realized corresponded to 20,000 years.

Orbit was also the second phase in a planetary assault and covered the gaining control of the orbital space around the target planetary system and the strategic orbital placement of the units in the invasion fleet.

Physics

"Actually, an orbit is a very delicate balance between a planet's gravity and a spacecraft's speed."

―4B-X^[2]

Slipping into orbit required a delicate balance between the starship's straightforward movement and the planet's gravity. While the First Law of Motion stated that a ship in motion should normally stay in the same motion, the planet's gravity would pull down on it. The perfect balance for orbiting was achieved when the pull was not strong enough to make the ship crash, and yet strong enough to keep it from flying away.^[2]

Two types of orbital assault

According to military strategist Michael Unther of the Galactic Empire, there were two main tactics within this phase: objective orbit and siege orbit.

Objective orbit

File:PlanetaryBombardment-SWGTCG.jpg

Imperial Star Destroyers and frigates bombard a planet from orbit

Objective orbit consisted in placing the entire invasion fleet in the space above one single objective like a capital or a starport. This would allow the invasion fleet to target key points while remaining safe from raids by small groups of defending ships, but also only allowed for the control of smaller areas. Moreover, this strategy did not allow the invasion fleet to control enemy supply lines. One strategy to reduce the number of objectives was simply to bombard cities and starports as well as industrial facilities.

Siege orbit

In a siege orbit, the units in the fleet are placed around the planet so as to prevent enemy ships from leaving and entering. Siege orbits thus reduced the number of logistic assets of the defenders and also allowed for the bombardment of enemy ground forces wherever they would concentrate.

Unther considered this a more risky alternative to the objective orbit, and argued that the orbital siege at the Battle of Hoth was an example of the weaknesses of siege orbits as Darth Vader's invasion force were somewhat handicapped due to Admiral Ozzel's mistake during the approach phase. Because the fleet came out of hyperspace too close to the Hoth system, the fleet units had to rush to get to their assigned positions, giving them little time for deploying fighter escorts. Several Rebel ships managed to escape the system before Imperial vessels had reached their planetary orbital positions.

Defending forces

An important aspect of this phase was, according to Unther, knowledge of the defending forces, as there were several different ways to defend a system from planetary assault. The unorthodox strategies of Carigan at the Battle of Bryx caused severe problems for the Imperial invasion fleet. The most common type of planetary defense, however, was the starfighter-based space-snipe strategy.