TARGETING THE MARTIAN MOONS VIA DIRECT INSERTION INTO MARS’ ORBIT Davide Conte * , David B. Spencer † Here, we analyze interplanetary transfer maneuvers from Earth to Mars in order to target the Martian moons, Phobos and Deimos. Such analysis is done by solving Lambert’s Problem and investigating the necessary targeting upon arrival at Mars. Additionally, the orbital parameters of the arrival trajectories as well as the relative required Δv’s and times of flight were determined in order to define the optimal departure and arrival windows for a given range of dates. It was found that minimum Δv trajectories for Earth-Phobos and Earth-Deimos transfers do not necessarily occur when Δv for Earth-Mars transfers is minimized, but they depend on the orientation of the arrival orbit and the type of maneuver that is performed to rendezvous with one of the Martian moons. INTRODUCTION Due to budget pressures, the cost of space missions has become a more important key factor in deciding whether a mission will take place. Therefore, it is necessary to make propellant-efficient decisions starting from the trajectory design. Optimal trajectories will not only reduce the cost of missions to Mars, but they will also allow for more massive payloads to be transported in orbit around and possibly land on the red planet. The low Martian atmospheric density makes the en- try, descent and landing (EDL) process for large payloads particularly difficult. Perhaps a first approach to missions to Mars will be represented by landing on one of the moons of Mars, Pho- bos or Deimos. In fact, neither moon possesses an atmosphere, making EDL and ascent to orbit an easier task for both robotic and crewed missions. In this paper, low Δv trajectories from Earth to the Martian moons are found by analyzing the orientation of the arrival orbits at Mars. Alt- hough only a few specific cases are presented here, additional results can be found in Conte. 2 MISSIONS TO PHOBOS AND DEIMOS Although various mission scenarios to Phobos and Deimos have been proposed in the past, no actual mission ever successfully flew to either of the moons. The mission Phobos-Grunt, a com- bined effort of the Russian and Chinese space agencies, had the purpose to fly to Mars, deploy a Chinese orbiter (YH-1) around the planet, and return a regolith sample from Phobos. Unfortu- nately, the probe failed to leave Earth’s orbit after launching in November 2012. According to the National Centre for Space Studies (CNES), the maneuvers required to rendezvous with Phobos upon arrival at Mars would have taken up to nine months and five or six orbit corrections would have to be conducted. One primary factor which dictates such an extended timeframe is commu- * Ph.D. Candidate, Department of Aerospace Engineering, The Pennsylvania State University, 229 Hammond Building, University Park, PA, 16802. † Professor, Department of Aerospace Engineering, The Pennsylvania State University, 229 Hammond Building, Uni- versity Park, PA, 16802. AAS 15-580 1