Wireless Instrumentation System Experiment

This article describes the design details of a Wireless Instrumentation System that was experimented in ISRO’s recent Human in Space Project (HSP) Pad Abort Test (PAT) mission in piggy-back mode. The system consists of a few Wireless Sensor Nodes (WSNs) that acquire parameter data and a Wireless Base Station that collects these over an IEEE 802.15.4 compatible single-hop RF link and forward it to the telemetry subsystem. The circuit configuration, communication link and protocol as well as the measurement plan as adopted for HSP-PAT flight test are described to bring out the scalability of the architecture. The performance of the system in HSP-PAT mission is discussed in detail by way of PFA analysis results. All the parameters monitored through the system, including inertial ones such as acceleration and rotation were compared with reference data obtained from functional Telemetry Telecommand and Power and Navigation Guidance and Control chains and showed normal signatures. Maintaining an uninterrupted wireless communication channel in a hostile and crowded chamber like the Crew Module for all the nodes has called for a robust Medium Access Control (MAC) layer based on the industry-popular IEEE802.15.4 RF PHY. The requirement of such a robust MAC layer is established when the radio frequency links outage encountered in one of the WSN links during the interval of high vehicle dynamics is seen to be taken care of by the diverse link of the same node. A future roadmap towards self-powered wireless sensors is also outlined.