Richard J. Barton

Performance comparison of wireless sensor network standard protocols in an aerospace environment: ISA100.11a and ZigBee Pro

Standards-based wireless sensor network (WSN) protocols are promising candidates for spacecraft avionic systems, offering unprecedented instrumentation flexibility and expandability. However, when migrating from wired to wireless data gathering systems, ensuring reliable data transport is a key consideration. In this paper, we conduct a rigorous laboratory analysis of the relative performance of the ZigBee Pro and ISA100.11a protocols in a representative crewed aerospace environment. Since both operate in the 2.4 GHz radio frequency (RF) band shared by systems such as Wi-Fi, they are subject at times to potentially debilitating RF interference. We compare message delivery rates achievable by both under varying levels of 802.11g Wi-Fi traffic. We conclude that while the simpler, more inexpensive ZigBee Pro protocol performs well under moderate levels of interference, the more complex and costly ISA100.11a protocol is needed to ensure reliable data delivery under heavier interference. This paper represents the first published, rigorous analysis of WSN protocols in an aerospace analog environment of which we are aware and the first published head-to-head comparison of ZigBee Pro and ISA100.11a.

Detection, identification, location, and remote sensing using SAW RFID sensor tags

We consider the problem of simultaneous detection, identification, location estimation, and remote sensing for multiple objects in an environment. In particular, we describe the design and performance of a system capable of simultaneously detecting the presence of multiple objects, identifying each object, and acquiring both a low-resolution estimate of location and a high-resolution estimate of temperature for each object based on wireless interrogation of passive surface acoustic wave (SAW) radio-frequency identification (RFID) sensor tags affixed to each object. The system is being studied for application on the lunar surface as well as for terrestrial remote sensing applications such as pre-launch monitoring and testing of spacecraft on the launch pad and monitoring of test facilities. The system utilizes a digitally beam-formed planar receiving antenna array to extend range and provide direction-of-arrival information coupled with an approximate maximum-likelihood signal processing algorithm to provide near-optimal estimation of both range and temperature. We examine the theoretical performance characteristics of the system and compare the theoretical results with results obtained from controlled laboratory experiments.1,2

Unified Communications for Space Inventory Management

To help assure mission success for long-duration exploration activities, NASA is actively pursuing wireless technologies that promote situational awareness and autonomy. Wireless technologies are typically extensible, offer freedom from wire tethers, readily support redundancy, offer potential for decreased wire weight, and can represent dissimilar implementation for increased reliability. In addition, wireless technologies can enable additional situational awareness that otherwise would be infeasible. For example, addition of wired sensors, the need for which might not have been apparent at the outset of a program, night be extremely costly due in part to the necessary routing of cables through the vehicle. RFID, or radio frequency identification, is a wireless technology with the potential for significant savings and increased reliability and safety in space operations. Perhaps the most obvious savings relate to the application of inventory management. A fully automated inventory management system is highly desirable for long-term sustaining operations in space environments. This assertion is evidenced by inventory activities on the International Space Station, which represents the most extensive inventory tracking experience base in the history of space operations. In the short tern, handheld RFID readers offer substantial savings owing to reduced crew time for inventory audits. Over the long term, a combination of improved RFID technology and operational concepts modified to fully utilize the technology should result in space based inventory management that is highly reliable and requires very little crew time. In addition to inventory management, RFID is likely to find space applications in real-time location and tracking systems. These could vary from coarse-resolution RFID portals to the high resolution afforded by ultra-wideband (UWB) RFID. Longer range RFID technologies that leverage passive surface acoustic wave (SAW) devices are being investigated to track assets on a lunar or planetary surface.

Delay tolerant, radio frequency identification (RFID)-enabled sensing

In this paper, we describe a method of providing guaranteed delivery of sensor data gathered at arbitrary times using an only intermittently available radio frequency identification (RFID) transport scheme. This technique provides a passive (e.g., non-powered) interface for a power-constrained embedded device to transport sensor data while overcoming the limitation of infrequent access to an RFID interrogator.

An Overview of the Smart Sensor Inter-agency Reference Testbench (SSIART)

In this paper, we present an overview of a proposed collaboration between the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA), which is designed to facilitate the introduction of commercial-off-the-shelf (COTS) radios for smart-sensing applications into international spaceflight programs and projects. The proposed work will produce test hardware reference designs, test software reference architectures and example implementations, test plans in reference test environments, and test results, all of which will be shared between the agencies and documented for future use by mission planners. The proposed collaborative structure together with all of the anticipated tools and results produced under the effort is collectively referred to as the Smart Sensor Inter-agency Reference Testbench or SSIART. It is intended to provide guidance in technology selection and in increasing the related readiness levels of projects and missions as well as the space industry.

Space Applications of Low-Power Active Wireless Sensor Networks and Passive RFID Tags

The purpose of this chapter is to demonstrate the increasing importance of Wireless Sensor Networks (WSNs) in all aspects of NASA space exploration activities, review several areas of recent development, and examine in some detail two WSN technology areas being explored at NASA Johnson Space Center (JSC). The two technology areas of emphasis are low-power active WSN protocols and architectures and passive wireless Radio-Frequency Identification (RFID) inventory tracking systems. The methodologies and motivations for developing each of these WSN technologies for space application are explored in the chapter, and the current state of the art in each area as well as the anticipated future developments are reviewed. In addition, devices, systems, as well as operational concepts currently under development at JSC are described, and the results of a recent performance evaluation study of alternative low-power active WSN technologies undertaken at JSC are presented and discussed.

Avionics Architectures for Exploration: Wireless Technologies and Human Spaceflight

The authors describe ongoing efforts by the Avionics Architectures for Exploration (AAE) project chartered by NASAs Advanced Exploration Systems (AES) Program to evaluate new avionics architectures and technologies, provide objective comparisons of them, and mature selected technologies for flight and for use by other AES projects. The AAE project team includes members from most NASA centers and from industry. This paper provides an overview of recent AAE efforts, with particular emphasis on the wireless technologies being evaluated under AES to support human spaceflight.