A report discusses a computer vision algorithm for position estimation to enable precision landing during planetary descent. The Descent Image Motion Estimation System for the Mars Exploration Rovers has been used as a starting point for creating code for precision, terrain-relative navigation during planetary landing. The algorithm is designed to be general because it handles images taken at different scales and resolutions relative to the map, and can produce mapped landmark matches for any planetary terrain of sufficient texture. These matches provide a measurement of horizontal position relative to a known landing site specified on the surface map. Multiple mapped landmarks generated per image allow for automatic detection and elimination of bad matches. Attitude and position can be generated from each image; this image-based attitude measurement can be used by the onboard navigation filter to improve the attitude estimate, which will improve the position estimates.

FFT Map-Matching Concept.
The algorithm uses normalized correlation of grayscale images, producing precise, sub-pixel images. The algorithm has been broken into two sub- algorithms: (1) FFT Map Matching (see figure), which matches a single large template by correlation in the frequency domain, and (2) Mapped Landmark Refinement, which matches many small templates by correlation in the spatial domain. Each relies on feature selection, the homography transform, and 3D image correlation. The algorithm is implemented in C++ and is rated at Technology Readiness Level (TRL) 4.

This work was done by Andrew Johnson, Adnan Ansar, and Larry Matthies of Caltech for NASA's Jet Propulsion Laboratory.

The software used in this innovation is available for commercial licensing. Please contact Karina Edmonds of the California Institute of Technology at (626) 395-2322. Refer to NPO-44463.

Topics:
Computer software and hardware Imaging and visualization Mathematical models Optics Simulation and modeling Software
This Brief includes a Technical Support Package (TSP).
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Mapped Landmark Algorithm for Precision Landing

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NASA Tech Briefs Magazine

This article first appeared in the September, 2007 issue of NASA Tech Briefs Magazine (Vol. 31 No. 9).

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Overview

The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing the Mapped Landmark Algorithm for Precision Landing, identified as NPO-44463. This package is part of NASA Tech Briefs and aims to disseminate information on aerospace-related developments with potential technological, scientific, or commercial applications.

The Mapped Landmark Algorithm is designed to enhance precision landing capabilities for spacecraft. It utilizes advanced computer vision techniques to match descent imagery with pre-existing map data, allowing for accurate navigation and landing on various celestial bodies. The algorithm's effectiveness is demonstrated through a series of experiments and simulations, which assess its performance under different conditions.

Key components of the document include:

  1. Flight Testing and Data Collection: The algorithm was tested during a flight in April 2006, utilizing imagery from various altitudes (from 1600m to 300m AGL) and at different resolutions (ranging from 1.5m to 0.3m). The data collection involved a camera operating at 30Hz, GPS for position tracking, and an Inertial Measurement Unit (IMU) for motion sensing.

  2. Scalability Experiments: The document discusses experiments that evaluate the algorithm's performance under varying lighting conditions and image noise. These experiments are crucial for understanding how the algorithm can adapt to different environments, such as those encountered on the Moon or Mars.

  3. Image Matching Techniques: The algorithm employs sophisticated image matching techniques to correlate descent imagery with map data. This process is vital for ensuring that the spacecraft can accurately identify its landing site and make necessary adjustments during descent.

  4. Technical Support and Collaboration: The document emphasizes the collaborative nature of the research, inviting further inquiries and partnerships through the NASA Innovative Partnerships Program. It provides contact information for those interested in exploring the technology further.

Overall, the Technical Support Package serves as a comprehensive overview of the Mapped Landmark Algorithm, showcasing its potential to improve the safety and accuracy of spacecraft landings. It highlights the importance of ongoing research and development in aerospace technology, aiming to facilitate future missions to various celestial bodies. The document underscores NASA's commitment to innovation and the sharing of knowledge within the scientific community.