Autonomous positioning and orientating for lunar launch

The initial positioning and orientating of the inertial navigation system (INS) is the critical issue for launch especially on the moon. The problem of positioning has been traditionally solved by radiometric tracking from the earth-based ground system or from the spacecraft on lunar orbit just like what the Apollo did. The orientating or alignment of INS on lunar surface is another question. In Apollo the inertial measurement unit (IMU) alignment was finished by astronauts using the Alignment Optical Telescope (AOT). To increase the safety of the project, a new designed optical navigation sensor system is adopted as a backup navigation method in NASA's Constellation program, which can perform the determination of launch position and launch attitude independent of earth support. But this equipment is complex and should still be operated by astronauts. In this paper an autonomous positioning and orientating method for lunar ascent with only two sensors, a star tracker and a set of IMU, is introduced. The whole algorithm is discussed in details and its precision with the influence to lunar ascent was verified by a Mont-Carlo simulation. Copyright ©2010 by the International Astronautical Federation. All rights reserved.