Jaret Matthews

Athlete: A cargo handling and manipulation robot for the moon

A robotic vehicle called ATHLETE—the All-Terrain Hex-Limbed, Extra-Terrestrial Explorer—is described, along with initial results of field tests of two prototype vehicles. This vehicle concept is capable of efficient rolling mobility on moderate terrain and walking mobility on extreme terrain. Each limb has a quick-disconnect tool adapter so that it can perform general-purpose handling, assembly, maintenance, and servicing tasks using any or all of the limbs.

Traverse Performance Characterization for the Mars Science Laboratory Rover

It is anticipated that the Mars Science Laboratory rover, named Curiosity, will traverse 10–20 km on the surface of Mars during its primary mission. In preparation for this traverse, Earth-based tests were performed using Mars weight vehicles. These vehicles were driven over Mars analog bedrock, cohesive soil, and cohesionless sand at various slopes. Vehicle slip was characterized on each of these terrains versus slope for direct upslope driving. Results show that slopes up to 22 degrees are traversable on smooth bedrock and that slopes up to 28 degrees are traversable on some cohesive soils. In cohesionless sand, results show a sharp transition between moderate slip on 10 degree slopes and vehicle embedding at 17 degrees. For cohesionless sand, data are also presented showing the relationship between vehicle slip and wheel sinkage. Side by side testing of the Mars Exploration Rover test vehicle and the Mars Science Laboratory test vehicle show how increased wheel diameter leads to better slope climbing ability in sand for vehicles with nearly identical ground pressure. Lastly, preliminary data from Curiositys initial driving on Mars are presented and compared to the Earth-based testing, showing good agreement for the driving done during the first 250 Martian days.

Borehole imagery of meteoric and marine ice layers in the Amery Ice Shelf, East Antarctica

A real-time video camera probe was deployed in a hot-water drilled borehole through the Amery Ice Shelf, East Antarctica, where a total ice thickness of 480 m included at least 200 m of basal marine ice. Down-looking and side-looking digital video footage showed a striking transition from white bubbly meteoric ice above to dark marine ice below, but the transition was neither microscopically sharp nor flat, indicating the uneven nature (at centimetre scale) of the ice-shelf base upstream where the marine ice first started to accrete. Marine ice features were imaged including platelet structures, cell inclusions, entrained particles, and the interface with sea water at the base. The cells are assumed to be entrained sea water, and were present throughout the lower 100-150m of the marine ice column, becoming larger and more prevalent as the lower surface was approached until, near the base, they became channels large enough that the camera field of view could not contain them. Platelets in the marine ice at depth appeared to be as large as 1-2 cm in diameter. Particles were visible in the borehole meltwater; probably marine and mineral particles liberated by the drill, but their distribution varied with depth.

On the design of the Axel and DuAxel rovers for extreme terrain exploration

The solar systems most scientifically tantalizing terrain remains out of reach for traditional planetary rovers, which are typically limited to driving on slopes below 30 degrees. This paper details the design of a novel robotic explorer that would open access to these previously inaccessible locales, such as Martian crater walls where evidence of salty water was recently detected, Lunar polar craters where evidence of water ice was detected, and Lunar and Martian lava tubes for future habitability. The Axel rover is a two-wheeled robot capable of rappelling down steep (even vertical) slopes supported by a tether. The DuAxel rover is comprised of two Axel vehicles docked to a central module. Unrestricted by tether length, this four-wheeled system would be capable of driving long distances from a safe landing zone to the extreme terrain of interest. Once in the vicinity of terrain in which the tether would be required, one of the Axel rovers could undock from the central chassis and rappel downslope. The other Axel and central chassis would remain topside to act as an anchor and to provide line of site to Earth (for communications) and the Sun (for energy). As the detached Axel descends into the area of interest, it would receive power and relays data through conductors in its tether. Each Axel would carry a suite of instruments in a bay that would be tucked inside the wheels. Because of the novel configuration of Axels major degrees of freedom, these instruments could be precisely pointed at targets at any desired downslope spatial separation. These instruments could then be deployed into close proximately to the ground by means of a simple mechanism, allowing for detailed study of the strata on the slope. Axel could accommodate a host of instruments, including a microscopic imager, infrared spectrometers, thermal probes, and sample collection devices. This paper will describe the design of both the latest generation of Axel and DuAxel systems and their instrument/sampling mechanisms. Results from recent field trials at a rock quarry in California and a Martian analog site in the desert of Arizona will be described.

Lunar Surface Operation Testbed (LSOT)

This paper describes a high fidelity mission concept systems testbed at JPL, called Lunar Surface Operations Testbed (LSOT). LSOT provides a unique infrastructure that enables mission concept studies designers to configure and demonstrate end-to-end surface operations using existing JPL mission operations and ground support tools, Lander, robotic arm, stereo cameras, flight software, and soil simulant (regolith), in a high fidelity functional testbed. This paper will describe how LSOT was used to support the MoonRise mission concept study. MoonRise: Lunar South Pole-Aitken Basin Sample Return Mission would place a lander in a broad basin near the moons South Pole and return approximately two pounds of lunar materials to Earth for study. MoonRise was one of three candidate missions competing to be selected as the third mission for NASAs New Frontiers Program of Solar System Explorations. LSOT was used to demonstrate JPLs extensive experience and understanding of the MoonRise Lander capabilities, design maturity, surface operations systems engineering issues, risks and challenges.