Artemis Trans-lunar INJECTION

NASA's THEMIS mission, launched in 2007 from Cape Canveral, gave some pioneering results about Earth magnetosphere, especially confirming the existence of magnetic reconnection and of Birkeland currents.

However, this article won't cover details about the scientific payloads of the mission. It will instead focus on the its extension, decided in 2008, which redirected THEMIS-B and THEMIS-C to the Moon, using a very interesting orbit called Lissajous orbit. The new mission was renamed ARTEMIS.

    We will analyze the orbit using SPICE kernels, a binary data format which cover complete ancillary data of an object (such as velocities, orientations and reference frames). This file format, together with software APIs and other utilities is maintained by The Navigation and Ancillary Information Facility (NAIF).

 SPICE kernel content. Source: NAIF 

        Situated on an orbit with an constantly increasing eccentricity starting with 2008, the spacecraft, was inserted into its Lissajous orbit starting with 2010, performing two Lunar and one Earth flybys. On 22 June 2011, a firing maneuver was performed, putting the spacecraft on its transfer orbit onto the Moon, which was reached in July, same year. Lissajous orbit is a multi plane orbit, around a Lagrange point of two-body system (a restricted solution of three-body problem, where the third body is very small, the spacecraft in our case). 

        The orbit computation was performed using Cosmographia software, Berkley SPICE kernels, and a generic spacecraft. Below you can find the result, using an Earth centered inertial J2000 coordinate system. Unfortunately due to some limitation of the website, the quality of the visualization is drastically reduced.

Thanks for reading!