Safe Navigation and Visual Odometry-based Localization for Planetary Exploration Rovers

<p>The future robotic exploration of planetary surfaces will require autonomous and safe operations to accomplish outstanding scientific objectives. The main goal of space robotic systems consists in expanding our access capability to harsh environments in the solar system (<em>e.g.</em>, Martian polar caps, icy moons). However, the operations of systems onboard landers and rovers are still mainly commanded and controlled by ground operators. To enhance the efficiency of future rovers, we are developing a robust guidance, navigation and control system that enables safe mobility on different terrain and slopes conditions, including the presence of obstacles.</p><p>High slippery terrains, such as sandy-loose soils, could prevent the rover locomotion, affecting its safety. Furthermore, the presence of these demanding terrains may impact on the rover navigation, leading to inaccuracies in the Wheel Odometry (WO) measurements because of wheels’ loss of traction. Therefore, we implemented a navigation algorithm based on Visual Odometry (VO) that is the technique based on the processing of stereo-camera images captured at successive times during the vehicle’s motion. This method is fundamental to help WO during operations that require fast responses and high-accurate positioning. We also adopted a LIDAR sensor to improve the position estimate accuracy by processing measurements associated with well-known terrain features.</p><p>We present here numerical simulations of rover navigation across different terrain conditions by using accurate dynamical models, including the deformability of both wheel and terrain. VO and LIDAR data are simulated and processed to determine the positioning accuracies that enable safe navigation. The results are in full agreement with the existing (<em>i.e.</em>, Mars Exploration Rovers (MER)) and future (<em>i.e.</em>, ExoMars) rover performances. Our algorithm allows reconstructing the rover trajectory with higher accuracies compared to the localization system requirement of the NASA MER rovers (<em>i.e.</em>, 10% error over 100 meters traverse).</p>

Boundary Layer Characterization using Mini-TES observations from the Mars Exploration Rovers

<p>The Mars Exploration Rovers (MER), Spirit and Opportunity, landed on Mars in 2004 just weeks apart. Using spectra from the Miniature Thermal Emission Spectrometer (Mini-TES), both rovers were able to sample the lowest 2 km of the vertical temperature profile of the atmosphere. During a single observation for Mini-TES, spectra were taken every two seconds with observations lasting up to 42 minutes. While results up to this point have averaged the spectra together to retrieve information on dust, water vapor and temperature, individual temperature retrievals are possible every two seconds and contain information on short timescale atmospheric fluctuations. These fluctuations are indicative of boundary layer behavior at each site. We have retrieved the vertical temperature profile from individual spectra and have used these profiles to assess boundary layer conditions at each rover location. We will present temperature profiles from individual retrievals and identify and characterize fluctuations within these profiles. We will also show the seasonal variation of these fluctuations over the first 1200 sols (nearly 2 Mars Years) for both Spirit and Opportunity rovers.</p>

Enhancing the Science Return of Landed X-ray Spectrometers on the Mars Rovers

<p>Alpha Particle X-ray Spectrometers (APXS) have flown on the Mars Exploration Rovers (MER) <em>Spirit</em> and <em>Opportunity</em> as well as the Mars Science Laboratory (MSL) rover <em>Curiosity</em>. The APXS was designed and calibrated for in situ interrogation of solid martian samples through the use of complementary particle-induced X-ray emission and X-ray fluorescence analysis techniques. Its compact and robust design, combined with low power and data demand, further suit the APXS instrument and method for lengthy missions to the surface of rocky bodies in our solar system. Since their three respective landings, the science derived from the latest APXS instruments has been expanded beyond its original scope through the integration of computational techniques and modest changes to how the instrument is utilized on Mars. We will discuss these new methods, operational considerations, as well as the enhanced science achieved, with a particular focus on the relevance and future application on the surface of Mars.</p>

Absolute Navigation and Positioning of Mars Rover Using Gravity-Aided Odometry

Positioning and Navigation (PN) of Martian rovers still faces challenges due to limited observations. In this paper, the PN feasibilities of Mars rovers based on a Gravity-aided Odometry (GO) system are proposed and investigated in terms of numeric simulations and a case study. Statistical features of the Mars gravity field are studied to evaluate the feature diversity of the background map. The Iterative Closest Point (ICP) algorithm is introduced to match gravity measurements with the gravitational map. The trajectories of Mars Exploration Rovers (MER) and Mars Gravity Map 2011 (MGM2011) are used to complete the experiments. Several key factors of GO including odometry errors, measurement uncertainties, and grid resolution of the map are investigated to evaluate their influences on the positioning ability of the system. Simulated experiments indicate that the GO method could provide an alternative positioning solution for Martian surface rovers.