Engineering topics
Johnson, A. E.
Publications and source records attributed to Johnson, A. E..
Optical landmark detection for spacecraft navigation
In this paper, a new crater detection algorithm is suggested. Experimental studies show that this new algorithm can achieve sub-pixel accuracy in position, its detection rate is better than 90% and its false alarm rate is less than 5%. These good characteristics indicate that it is an ideal crater detection algorithm for spacecraft optical navigation.
Probabilistic #D data fusion for multiresolution surface generation
In this paper we present an algorithm for adaptive resolution integration of 3D data collected from multiple distributed sensors. The input to the algorithm is a set of 3D surface points and associated sensor models. Using a probabilistic rule, a surface probability function is generated that represents the probability that a particular volume of space contains the surface. The surface probability function is represented using an octree data structure; regions of space with samples of large conariance are stored at a coarser level than regions of space containing samples with smaller covariance. The algorithm outputs an adaptive resolution surface generated by connecting points that lie on the ridge of surface probability with triangles scaled to match the local discretization of space given by the algorithm, we present results from 3D data generated by scanning lidar and structure from motion.
Scanning LIDAR algorithms for safe and precise landing on Mars
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Descent-speed testing of a hazard detection system for safe landing on Mars
In a previous paper we described an approach for testing a prototype system designed to detect hazards during the terminal descent phase of a mission to Mars. The system under development at the Jet Propulsion Laboratory (JPL) utilizes a scanning laser radar and an inertial measurement unit to map the landing zone, identify hazards, and thenguide the vehicle to a safe landing site. The test approach consisted of a placing this system on a rocket sled, accelerating the sled to typical descent speeds, and mapping a simulated Martian terrain. The data would then be processed to identify hazards and locate a safe landing site. Since ref. 1 was written several such tests have been performed. In this paper we provide an update on the testing methodology and we present preliminary results from one of the tests.
Passive imaging based hazard avoidance for spacecraft safe landing
In this paper, a new and fast passive sensing based hazard avoidance approach for spacecraft safe landing is suggested. This approach contains two important algorithms: a texture based landing site selection algorithm and a landing site slope estimation algorithm.
Efficient passive image-based hazard detection for safe landing on Mars
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Lidar-based hazard avoidance for safe landing on Mars
This paper describes the algorithms and the models that comprise a scanning lidar-based hazard avoidance simulation including a terrain generator, a lidar model, hazard avoidance algorithms and powered landing guidance algorithms.
HAL/S-360 compiler system specification
A three phase language compiler is described which produces IBM 360/370 compatible object modules and a set of simulation tables to aid in run time verification. A link edit step augments the standard OS linkage editor. A comprehensive run time system and library provide the HAL/S operating environment, error handling, a pseudo real time executive, and an extensive set of mathematical, conversion, I/O, and diagnostic routines. The specifications of the information flow and content for this system are also considered.