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Trans-Mars injection diagram.
A = Hohmann transfer orbit. B = Conjunction mission. C = Opposition mission
A trans-Mars injection (TMI) is a propulsive maneuver used to set a spacecraft on a trajectory, also known as Mars transfer orbit, which will cause it to arrive at Mars.
Every two years, low-energy transfer windows open up which allow movement between planets with the lowest possible Delta-v requirements. Transfer injections can place spacecraft into either a Hohmann transfer orbit, or bi-elliptic transfer orbit. Trans-Mars injections can be either a single maneuver burn, such as that used by the NASA MAVEN orbiter, or a series of perigee kicks, such as that used by the ISRO Mars Orbiter Mission.