Development of Precise Lunar Orbit Propagator and Lunar Polar Orbiter's Lifetime Analysis

Abstract

To prepare for a Korean lunar orbiter mission, a precise lunar orbit propagator; Yonsei precise lunar orbit propagator (YSPLOP) is developed. In the propagator, accelerations due to the Moon's non-spherical gravity, the point masses of the Earth, Moon, Sun, Mars, Jupiter and also, solar radiation pressures can be included. The developed propagator's performance is validated and propagation errors between YSPOLP and STK/Astrogator are found to have about maximum 4-m, in along-track direction during 30 days (Earth's time) of propagation. Also, it is found that the lifetime of a lunar polar orbiter is strongly affected by the different degrees and orders of the lunar gravity model, by a third body's gravitational attractions (especially the Earth), and by the different orbital inclinations. The reliable lifetime of circular lunar polar orbiter at about 100 km altitude is estimated to have about 160 days (Earth's time). However, to estimate the reasonable lifetime of circular lunar polar orbiter at about 100 km altitude, it is strongly recommended to consider at least 50 × 50 degrees and orders of the lunar gravity field. The results provided in this paper are expected to make further progress in the design fields of Korea's lunar orbiter missions.

Ground Contact Analysis for Korea's Fictitious Lunar Orbiter Mission

“…To predict the orbiter's states expressed in both Moon and Earth centered coordinate systems, a previously developed and performance verified precise lunar orbit propagator developed by Song et al (2010b) is used and modified. This propagator was developed to design and analyze the spacecraft's states flying in the vicinity of the Moon.…”

“…This propagator was developed to design and analyze the spacecraft's states flying in the vicinity of the Moon. However, of the various Earth centered reference frames the precise lunar orbit propagator developed by Song et al (2010b) was only able to express the orbiter's states in E-EME2000 coordinate system. For the purpose of this research, additional functionalities to express the spacecraft's states in other Earth centered reference frames are implemented.…”

“…To design missions with a spacecraft located in very close proximity to the Moon, Cho et al (2009) analyzed optimal lunar landing trajectories with knowledge of parking orbits before the descent phase with assumptions of 2-dimensional problem and later, Jeong et al (2010) presented a precise planetary landing method with terrain aided inertial navigation. In subsequent research, Song et al (2010b) developed a precise lunar orbit propagator and analyzed the lunar polar orbiter's lifetime, concluding that the lunar polar orbiter's lifetime is strongly affected by the Moon's non-spherical gravitation and the Earth's point mass perturbation. In addition to these studies, Rew et al (2010) presented conceptual design results for KARI's dynamic simulator, which is especially designed to prepare Korea's future lunar explorer.…”

Analysis of Delta-V Losses During Lunar Capture Sequence Using Finite Thrust

“…It is assumed that the spacecraft is already located in the vicinity of the Moon, and thus the spacecraft's states are expressed in the reference coordinate frame of the Moon centered Moon mean equator and International Astronomical Union vector of epoch J2000 (M-MME2000). For more detailed information on the M-MME2000 coordinate frame, readers may refer to literature by Song et al (2010b).…”

“…To design missions with a spacecraft located in very close proximity to the Moon, Cho et al (2009) analyzed optimal lunar landing trajectories with knowledge of parking orbits before the decent phase with assumptions of 2-dimensional problem, and later, Jeong et al (2010) presented a precise planetary landing method with terrain aided inertial navigation. Song et al (2010b) developed a precise lunar orbit propagator and analyzed the lunar polar orbiter's lifetime, which is strongly affected by the Moon's non-spherical gravitation and the Earth's point mass perturbation.…”