Mars Rover communications and autonomy Dr Anthony J H Simons (from NASA materials)

2 Rover and Lander Different Configurations Solo rover, or working with lander and/or orbiter? Landing: arrest via rocket, parachute, or airbag? Swarms: copters, biomorphs, penetrators Different Control Strategies Signals direct to rover, or via orbiter, lander? Base, orbiter, lander, rover distribution of control Sensors: pressure, altimeter, laser, radar, vision Control: experiment deployment, data uplink

3 Example Missions NASA Pathfinder Sojourner July-September 1997 Lander base station plus small rover NASA Mars Exploration Rovers January-April 2004 (but still active) Two independent rovers Spirit and Opportunity landed at different locations

4 NASA Pathfinder Sojourner Image © Neil English, Exploring Mars, Pole Star Publications Ltd. Antenna Solar cells Multi-wheel drive Steerable front pair

5 Pathfinder Sojourner Lander Airbags to cushion landing Exit track for rover Lander bounces (like ball) Airbags deflate and shell opens Lander has uplink Image © Neil English, Exploring Mars, Pole Star Publications Ltd.

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9 NASA Spirit Rover (MER) Image © Neil English, Exploring Mars, Pole Star Publications Ltd. Stereo imaging and navigation cameras Direct-to- Earth uplink Poseable instrument package Multi-wheel drive Special hazard cameras Strut for long reach

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12 Deep Space Communications Distance to Mars Closest to Earth: 54.5 million km Furthest from Earth: million km Signal times Based on c = 299,793 km/s ~ 3.03 minutes (Earth/Mars closest) ~ minutes (Earth/Mars farthest) Consequences Base cannot react in real-time Rover must act autonomously

13 Mission Management Base station (Earth) Mission goals, priorities, master control Master data uplink, processing science results Local station (Orbiter, Lander) Local area planning, local priorities, alternate tasks Global hazards, sandstorm warnings, rover safety local data uplink, local processing, data reduction Rover Navigation, terrain following, obstacle avoidance Experiment selection, control, completion

14 Hardware Issues Satellite uplink Need for Earth/Mars, Rover/Orbiter communications What hardware, comms. protocols, power rating? Microcontrollers Small processors to read sensors and drive devices What memory, buses/ports, power rating, software? Communications bus How many sensors, devices, moving parts to control? Devices and sensors What devices/sensors? What registers to read/write?

15 Navigation Global Positioning System (GPS) Could the Rover use this to find out its location? How many Orbiters/registration signals? How often/accurately measured? How important? Tilt Sensors (Accelerometers) Compute velocity, position from known starting point using internal acceleration sensors Integrate acceleration over time for velocity, velocity over time for distance – but how to correct drift errors? Ultrasonic sensors Echo location system for computing distance from target Use in Martian atmosphere for obstacle avoidance?

16 Ultrasonic Sensors SRF08 ultrasonic sensor On-chip microcontroller PIC determines distance from objects Detects objects from 3cm – 6m I2C bus communicates with external TINI TINI concentrates on high- level control Product image © Total Robots. SRF08 sensors available from Total Robots

17 Instrument Packages Navigation Stereo navcams, hazcams, laser striper, ultrasound, inertial compass (no magnetic field) Science 360  panoramic camera, HD cameras Spectrometers: infrared/thermal emission (carbon, minerals), Moessbauer (iron-bearing properties) Rock abrasion tool Microscope (spores, bacteria) Wet science chemistry (lifesign reactions)

18 Software Issues Multi-tier AI for high-level autonomous decisions Stereo vision algorithms for navigation Sensing, analysis and data compression Reliability Triple-redundant voting system? Cosmic ray damage: reboot and/or reconfigure? Failsafe shutdown options Communications Coordinate rover, lander, orbiter?

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29 Future Missions NASA Phoenix Scout Launched in 2007, Polar Lander Wet chemistry, water-finding, life? NASA Mars Science Laboratory Launch in 2009, 10*payload of MER Skycrane rocket lander, nuclear power Projected Biomorph Swarms Aerobot/rotorcraft, biomorph/micro-rovers and subsurface penetrators Work as cooperating swarm, resilient to failures

30 NASA’s Phoenix Scout Lander only mission Mission to northern polar region Subsurface water ice? Wet water chemistry experiments Image © Neil English, Exploring Mars, Pole Star Publications Ltd.

31 NASA Mars Science Laboratory Direct-to- Earth uplink Much larger rover (*10) Image © Neil English, Exploring Mars, Pole Star Publications Ltd. Nuclear powered

32 Stanford: Mesicopter Swarm Swarm rotorcraft Robust and redundant Cooperating agents Image © NASA/DoD Second Biomorphic Explorers Workshop, JPL Work by Ilan Kroo, Peter Kunz, Dept. of Aeronautics and Astronomy, Stanford University

33 Swarm Exploration Image © NASA/DoD Second Biomorphic Explorers Workshop, JPL Work by Ilan Kroo, Peter Kunz, Dept. of Aeronautics and Astronomy, Stanford University

34 ANTS Mission

35 Swarm Control Massively parallel system How to predict all possible interactions? Cannot hope to test all behaviours System must be correct by design Tools for understanding, specifying swarms Individual-based modelling (FLAME tool) models cellular automata Formal method: X-Machines specifies cellular automata

Any Questions?