Future exploration missions require the ability to land precisely and safely on the moon, mars and asteroids. A promising approach to fulfill these requirements is the application of optical navigation, which can determine the vehicle’s position using images of the target body. This has the advantage of on-site data recording with almost no delay and the possibility to act independently from Earth, thereby avoiding long signal propagation times to Earth. Additionally, the navigation system is not affected by unfavorable communication conditions when the system is masked by sun or the target body. Several navigation sensors such as cameras and LIDARS are being developed for such purposes.
In cooperation with other DLR institutes, the department of Navigation and Control Systems is developing a sensor to independently, precisely and safely land on the Moon. The work is described in more detail on the ATON project page.
Before a new sensor system is employed on an exploration mission, it must be tested in a realistic scenario. Therefore, all environment data relevant for an optical navigation system must be simulated. This includes the dynamic, geometric and optical conditions which can occur during a Moon landing. The Testbed for Robotic Optical Navigation (TRON) is being developed at DLR Bremen in parallel to ATON. With TRON it will be possible to perform hardware-in-the-loop tests. For these purposes, the facility is equipped with the following:
1. Dynamic requirements
The task of the dynamic system is to realize a sensor system’s movement, which can be controlled in real time. This should correspond with the movement of a landing vehicle in Moon orbit. A KR16 by KUKA was chosen as the robotic system and it is installed on an 11m long linear track. The robot is operated in real time by a simulation computer with 85 Hz and has extremely high repeatability. Scales between 1:50000 and 1:100 can be used for the Moon landing phase, depending on the scenario.
2. Optical Requirements
The optical environment requirements of landing on the Moon are created by a lighting system. The lighting system consists of a lamp which can be moved by a crane installation in four degrees of freedom, which simulates the solar radiation from different sun positions. External light is blocked from entering the laboratory to ensure that the terrain models are only illuminated by the lighting system. Incident light is also blocked by covering the walls of the lab with black fabric to absorb stray light reflected by the terrain models.
3. Terrain Geometry: 3D Terrain Models of various size and scale
The laboratory has many possibilities for testing active (e.g. LIDAR) and passive optical sensors (e.g. cameras). While points 1 and 3 are most important for LIDAR tests, the testing of camera systems requires active lighting using point 2.