Lunar surface mobility autonomous navigation is becoming an important area of research again as the need arises to define the architecture of how science rovers and manned sortie missions will perform surface mobility navigation missions. Decisions need to be made as to what navigation aids and devices these vehicles will use to gain knowledge of their lunar surface position. During the Apollo era, surface mobility navigation missions utilized an autonomous navigation system consisting of an inertial measurement unit and star trackers.
The Lunar Surface Mobility Autonomous Navigation Assessment, conducted at the NASA Glenn Research Center, characterized the performance of two surface mobility profiles that could be used to traverse from the lunar module to the mission destination. The first of the surface mobility profiles was a circular path with a constant velocity. The radius of the path was 15 km. Instead of stopping at the destination 30 km from the lunar module, the profile followed the circular path to return to base. The second of the surface mobility profiles was a straight path with a variable velocity. The path length was 30 km in one direction. This profile stopped at the endpoint before returning to the lunar module.
Circular-track, constant-velocity profile.
Long description of figure 1.
Straight-track, variable-velocity profile.
Long description of figure 2.
The navigation assessment was based on using an autonomous navigation system. The system would contain measurements from a gyroscope and an accelerometer. Sources of gaussian error in the gyroscope instruments that were modeled included bias drift, scale factor, and random walk. Two sources of error in the accelerometer instruments that were modeled included bias repeatability and scale factor. Nonorthogonality in the gyroscope and accelerometer instruments were not modeled for this analysis. The performance of the surface mobility profiles was assessed for 20 different noise profiles to attempt to characterize the performance of the navigation system. Results of the simulations were computed in terms of the error in the three local Cartesian dimensions from the location of the lunar module. Results show that maximum errors of up to 5 km in a single Cartesian dimension1 could arise with this type of autonomous navigation system.
Circular-track, constant-velocity profile results, showing topocentric position errors for 20 cases. The three subplots correspond to local Cartesian coordinates x, y, and z (top to bottom).
Long description of figure 3.
Straight-track, variable-velocity profile results, showing topocentric position errors for 20 cases. The three subplots correspond to local Cartesian coordinates x, y, and z (top to bottom).
Long description of figure 4.
The Lunar Surface Mobility Autonomous Navigation Assessment effort is managed under the Space Communications and Data Systems Project at Glenn. The work was performed in-house by members of the Communications Systems Integration Branch in Glenn’s Communications Technology Division.
Find out more about the research of Glenn’s Communications Technology Division: http://ctd.grc.nasa.gov
Glenn contacts:
Bryan W. Welch, 216-433-3390, Bryan.W.Welch@nasa.gov
Joseph W. Connolly, 216-433-8728, Joseph.W.Connolly@nasa.gov
Author:
Bryan W. Welch
Headquarters program office:
Space Communications Technology Program
Programs/projects:
Space Communications and Data Systems Project, Space Communication Architecture Working Group
Last updated: December 14, 2007
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