Invocon on the International Space Station
Currently, Invocon has three systems in operation on the International Space Station (ISS): Internal Wireless Instrumentation System (IWIS™),External Wireless Instrumentation System (EWIS™), and Micro-gravity Measurement Apparatus (MMA).
IWIS was deployed by astronauts inside the partially completed ISS to collect data on the impulse response of the structure. This data is used to verify the structural integrity of the ISS on orbit. It will also be used to update models predicting the modal response of the ISS. Complete understanding of the resonant modes of the structure will allow effective planning of the re-boost and Reaction Control System (RCS) firing sequences when the Shuttle is docked with the Station. Since this data will change as the Station is assembled, it is important to keep this data current with each addition to the Station. The wireless nature of the data acquisition network minimizes the time necessary for deployment and recovery of the system. Further, some of the RCS test firings must occur when all airlocks between modules are closed. A wired system would not have the flexibility needed to accommodate mission changes and data acquisition windows of opportunity.
The first element of EWIS was deployed by the STS-115 crew as part of the installation of the P3/P4 truss. EWIS was developed as a system for acquiring vibration data from the truss structure to monitor the health of the truss components. The single EWIS Remote Sensor Unit (RSU) attached to the truss is currently collecting vibration data. This vibration data will be downloaded when the EWIS Network Control Unit (NCU) is installed during a future mission.
In 2008 the Japan Aerospace Exploration Agency (JAXA) will launch a module for the ISS that will contain another permanent Invocon system: Micro-gravity Measurement Apparatus (MMA). This system is designed to constantly monitor micro-vibrations in the Station that could adversely affect zero-g experiments. MMA Qual hardware was delivered in September, 2002. Flight Hardware is scheduled for delivery the first quarter of 2003.