Robotic Platforms for Rapid Prototyping and Deployment of Sensor Systems in Support of Orbital Surveys A. Elfes1, D. Clouse1, M. Powell1, E. A. Kulczycki1, J. L. Hall1, G. Podnar2, J. M. Dolan2 1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA ([email protected]/Fax: +1-818-393-5007)1 2 Robotics Institute, Carnegie-Mellon University, Pittsburgh, PA 15213 Abstract — Earth science research uses data obtained from TABLE OF CONTENTS space, the atmosphere, the oceans and the Earth’s land 1. INTRODUCTION ................................................................... 1 surfaces to improve understanding of our planet and its 2. AUTONOMOUS AEROBOTS.................................................2 natural processes. Orbital assets have so far been the 3. THE POTENTIAL OF AIRSHIPS FOR EARTH greatest source of the data that goes into atmospheric and OBSERVATION ......................................................................... 4 oceanic models, as well as into snow or vegetation cover 4. ROBOTIC OCEAN BOATS....................................................5 analyses and land utilization studies, to name just a few 5. CONCLUSIONS ..................................................................... 7 applications. At the same time, they are limited in terms of 6. ACKNOWLEDGMENTS ........................................................7 temporal/geographical coverage, resolution, cloud cover, REFERENCES ........................................................................... 7 and the physical properties measured by the onboard instruments. Crewed survey systems, including aircraft and ocean vessels, are expensive to deploy and have either 1. INTRODUCTION limited mission times (aircraft) or low survey speeds and Earth science research uses data obtained from space, the restricted sensorial extent (boats), while sensor networks are atmosphere, the oceans and the Earth’s land surfaces to limited in their sensor reach. Mobile robotic sensing improve understanding of our planet and its natural systems are emerging as new platforms for Earth science processes. Orbital assets have so far been the greatest source research. These platforms can be used in two different of the data that goes into atmospheric and oceanic models, modes: 1) to complement existing orbital and stationary as well as into snow or vegetation cover analyses and land sensing assets, or 2) to substitute for orbital or stationary utilization studies, to name just a few applications. assets. As mobile in situ platforms, they can provide data at spatiotemporal resolutions and geographical coverage that However, satellites are limited by cloud cover, complement what can be collected from orbiters or temporal/geographical coverage and sampling rates, stationary sensor networks. In this paper we review our resolution, and the physical properties measured by onboard work on the development of mobile platforms for sensing a sensors. Crewed survey systems, including aircraft and changing world, and their potential use to complement or ocean vessels, are expensive to deploy and have either provide an alternative to orbital assets. We discuss the use limited mission times (aircraft) or low survey speeds and of autonomous airships for aerial surveys, and the use of restricted sensorial extent (boats). Weather balloons or autonomous ocean surface robot boats for in situ surveys ocean buoys are relatively cheap, but cannot actively control triggered by orbital observations. We also discuss the their motion to reach specific areas of interest. Sensor development of software architectures for coordination and networks with geographically stationary nodes can provide control of multiple sensor platforms, and show results persistent (long-term) observation of areas of interest with obtained from field tests of aerial and ocean vehicles. We modest power and bandwidth requirements, at low to conclude with an outlook on the challenges that have to be moderate complexity and cost. The drawback is that the addressed to fully insert robotic vehicles in an Earth sensor payload available at each node of a stationary observing system. network is limited and configured prior to installation. Furthermore, these networks cannot be easily moved to another area if an event at a different geographical location is to be observed. Mobile robotic sensing systems are emerging as new platforms for Earth science research [1]. They include unmanned aerial vehicles (UAVs), autonomous water 1 978-1-4244-3888-4/10/$25.00 ©2010 IEEE 1 surface vehicles (ASVs), and autonomous underwater in their design, but limited in their “go-to” capability. vehicles (AUVs). These platforms can be used in two Advantages and disadvantages of different aerial vehicle different modes: 1) to complement existing orbital and designs for planetary exploration are assessed in [7]. stationary sensing assets, or 2) to substitute for orbital or stationary assets. In a complementary mode, robotic Since 2003 we have been developing the autonomy vehicles are deployed to an area of interest and instrumented technologies required for robotic lighter-than-air vehicles with a sensor payload configured to the specific natural and (aerobots) [8, 9]. While the initial exploration targets were environmental processes to be investigated. As mobile in defined as Titan and Venus, it is clear that aerobots, situ platforms, they can provide data at spatiotemporal particularly autonomous airships, can also play a significant resolutions and geographical coverage that complements role in science data gathering on Earth. This will be what can be collected from orbiters or stationary sensor exemplified below. networks. The current prototype JPL aerobot testbed (Fig. 1) has a In a substitutive mode, robotic vehicles (particularly UAVs), length of 11 m, a diameter of 2.5 m, total volume of 34 m3, can be used to provide an alternative to orbital systems. The two 2.3 kW (3 hp) 23 cm3 (1.4 cu inch) fuel engines, desire for an alternative can have several reasons, including: maximum speed of 13 m/s (25 kts), maximum ceiling of a) an orbital asset has become unavailable (such as the 1000 m, average mission endurance of 60 minutes, static lift demise of the Orbiting Carbon Observatory); b) a sensor payload of 12 kg ASL, and dynamic lift payload of up to 16 system has to be calibrated on Earth using an aerial vehicle kg ASL. The avionics and communication systems are before being sent to space (satellite mimicry); c) the need installed in the gondola. for alternatives that are cheaper and/or have faster development and deployment times that orbiters. While robotic systems have provided very successful platforms for scientific research elsewhere in the Solar System (such as the Mars Exploration Rovers), it is noteworthy that the use of robot explorers on Earth is still in its infancy. In this paper we review our work on the development of mobile platforms for sensing a changing world, and their potential use to complement or provide an alternative to orbital assets. We discuss the use of autonomous airships for aerial surveys, and the use of autonomous ocean surface robot boats for in situ surveys triggered by orbital observations. We also discuss the development of software architectures for coordination and control of multiple sensor platforms, and show results obtained from field tests of aerial and ocean vehicles. We conclude with an outlook on the challenges that have to be addressed to fully insert robotic vehicles in an Earth observing system. 2. AUTONOMOUS AEROBOTS Figure 1: The JPL aerobot during autonomous flight Robotic Lighter-Than-Air Vehicles tests. These flight tests were conducted at the El Mirage dry lake in the Mojave desert. In addition to Earth, seven other bodies in the Solar System have enough atmosphere to allow aerial exploration: Venus, The aerobot avionics system is built around a PC-104+ Mars, Jupiter, Saturn, Uranus, Neptune, and Saturn's moon computer architecture. The processor stack has a serial Titan. NASA has identified aerial vehicles as a strategic board interface to the navigation sensors, a PWM board for new technology for Solar System exploration [2, 3, 4], and reading pulsewidth modulated signals from the human emphasized the development of advanced autonomy safety pilot and generating PWM signals based upon control technologies as a high priority area for the operation of surface commands from the avionics software, and an IEEE aerial probes. The dense atmospheres at Titan and Venus 1394 board for sending commands to, and reading image enable the use of buoyant robotic vehicles (aerobots) that data from, the navigation and science cameras. Wireless can be either self-propelled (airships) or wind-driven serial modems provide data/control telemetry links between (balloons). These vehicles can provide extensive, low- the aerobot and the ground station, and additional video altitude geographical coverage over multi-month time scales transmitters on the aerobot provide downlinks of video with minimal consumption of scarce onboard electrical imagery to the ground station. The safety pilot can always power [5, 6]. Airships have the scientific advantage of being reassert “pilot override” control over the aerobot. able to fly to specific locations, while balloons are simpler 2 The navigation sensors currently consist of an IMU (angular rates, linear accelerations), a compass and inclinometer (yaw, roll and pitch angles), and a DGPS (for absolute 3D position). The vision sensors include