Axel Rover Research Articles

Enabling new exploration opportunities on planetary surfaces: In situ geochemical characterization in soils by dielectric spectroscopy onboard the AXEL rover system

In the work, we present dielectric spectroscopy (DS) is an analytical method capable of characterizing and quantifying electrochemically active materials (water/ice, ions, etc.) in planetary regoliths. Detection of these materials occurs when a small amount of energy is applied to an in situ sample, causing perturbation in the form of potential kinetic energy and inducing polarization and/or relaxation processes in materials of interest. The frequency dispersion on the electrical properties of impendences, relative permittivity, and conductivity spectra represents chemical and physical properties in association with inherent material properties. Therefore, measuring these energetic states can provide a unique fingerprint of the materials, depending on the frequencies that are scanned. In the case of water content in soils, the Debye equivalent circuit model can accurately predict its electrical properties and provide excellent quantification of the water content in soils.Use of DS is enabled by miniaturization of the key components and the low power requirements. DS is therefore capable of offering substantial scientific returns as an in situ sampling and non-destructive measurement technique, making it ideally suitable for deployment onboard many smaller space exploratory platforms. This work reports the first deployment use of DS from a field test for geochemical characterization of in situ soils, specifically on the quantification of water onboard the AXEL mobility system in the Mojave Desert.Laboratory testing has confirmed the sensitivity of DS with respect to particle size (fine vs coarse) determination as well as water content (down to 0.01 ​wt%) under a wide range of environmental conditions. Water content associated with bound and bulk water was uniquely identified in the soil mixture. We also describe a field demonstration using DS using two distinct insertion dielectric probes specifically design for sub-surface measurements, verifying their mechanical robustness and chemical stability. The field measurements are in good agreement with laboratory data and effectively quantified water content at about 3.0 ​wt% and 8.0 ​wt% for field test sites #1 and #2, respectively.

Axel and DuAxel rovers for the sustainable exploration of extreme terrains

AbstractSome of the most appealing science targets for future exploration missions in our solar system lie in terrains that are inaccessible to state‐of‐the‐art rover technology. This paper discusses the challenges and constraints of designing a robotic explorer for these “extreme'' terrains and then examines the trade‐offs among different mobility architectures. To address many of these challenges, we have developed the Axel family of rovers. The Axel rover is a two‐wheeled tethered robot capable of rappelling down steep slopes and traversing rocky terrain. The DuAxel rover, which is a four‐wheeled vehicle formed from two Axel rovers, provides untethered mobility to get to extreme terrains. We describe the basic design principles of these rovers and review our efforts to implement the key features of the Axel concept. Limitations found during experiments with prior Axel rover prototypes led to the design of a third‐generation Axel rover. We describe the features of this new rover and then present a thermal analysis conducted to assess the feasibility of exploring lunar cold traps, which are expected to have a temperature range of 40 to 70 K. We conclude the paper with results showcasing Axel and DuAxel's extreme‐terrain performance as evaluated during two recent field tests in a steeply sloped Southern California rock quarry and at a location in Arizona that closely resembles rugged Martian terrain. We also summarize lessons learned during the Axel development program. © 2012 Wiley Periodicals, Inc.