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ATON – Autonomous Terrain based Optical Navigation

Motivation

The aims of future exploration missions include the research of local phenomena, experiments on the utilization of resources and the construction of bases on different bodies such as mars, moon and asteroids. The ability to land autonomously, precisely and safely is a precondition for successful missions.

Optical systems are a promising navigation-technology for realizing landing missions because their measurements are not dependent on Earth and can be captured autonomously with a small delay. The image data can be used for an autonomous determination of the Lander’s position when combined with other sensor data, such as acceleration indicators. This is a necessary ability for independent and precise landing. Additionally, the image data can be used to choose a secure landing place.

ATON – Autonomous Terrain based Optical Navigation

The “Navigation and Control Systems” department is working collaboratively with other DLR institutes to develop a new optical navigation system within the scope of the ATON project. This new system should permit a landing vehicle to autonomously, precisely and safely land on the Moon. It will consist of a camera and a stereo recording optical system (stereo camera or LIDAR). The optical sensors will be complemented with further on-board sensor technology, including an acceleration indicator and a rotational speed sensor. The main part of this work comprises the development of image processing software for analysing optical sensor data and the navigation software. Using the image processing results and the on-board sensor data the navigation software creates an estimation of position and attitude.
This project will result in hardware for demonstration purposes. The navigation system, consisting of the image processing software and the optical sensors, can be tested in the Testbed for Robotic Optical Navigation (TRON) and its function can be verified. 

Research work for ATON in the department Navigation and Control Systems

The work in Bremen can be divided into three main parts:

1. Autonomous Position calculation

Crater identification on images of Moon surface (images by Kaguya Image Gallery)

The aim of the project is autonomous position estimation with an accuracy of a few hundred meters in Moon orbit and while approaching. The position will be determined using images of the Moon’s surface. Our approach is to use the existing craters on moon as landmarks. Over the next few years these craters will be indexed with an accuracy of about 10 meters. The sensor under development will use the indexed positions to determine which crater constellation is in a given image which yields the vehicle’s orientation. The planned procedure is:

• Image the Moon’s surface underneath the vehicle
• Identify crater constellations via image processing
• Calculate position related to the Moon’s centre

2. Validation of landing areas

Analysis of an area with gradient, green and blue mark areas with low gradient  View of a simulated landing area (the yellow marked area is the visual field of the sensor)

The goal of the discussed exploration missions is to safely land on an unspecified target area. In order to land precisely and safely, the space vehicle must land in an area with smooth terrain, with few stones and illuminated by the sun. However, these characteristics of the landing area are not known sufficiently before the landing manoeuvre. Therefore, starting when the landing area is visible, an analysis of the criteria mentioned above must be conducted.
This issue is worked on collaboratively with other institutes and includes the calculation of safety relevant characteristics such as gradient, existence of stones and craters, illumination and the analysis on scientific criteria. Additionally, the particular fuel consumption for alternative places is taken into account. These calculations result in a recommendation for a landing area.

3. Laboratory test for the demonstration hardware

TRON setup: robotic system with camera in front of a test terrain model

After software development, the system must be tested under realistic conditions which will be supported by the TRON laboratory. This laboratory will enable the generation of images of the Moon’s surface under realistic illumination conditions. For testing the navigation sensors are installed on the TRON robot and moved over different terrain models, which represent the mission phases in steps. The aim is a real time test of the navigation system in representative sections of all approaching phases.