Wireless Compose 2

Another sub-experiment used in Wireless Compose-2 is a smart shirt "SmartTex" specially developed for space applications, which integrates the sensor technology for ballistocardiography measurements from the "BEAT" experiment. This allows BCG measurements to be carried out on an astronaut in order to measure important heart parameters such as relative blood pressure as well as details on the contraction rate and opening/closing times of the heart valves, which are normally only accessible via sonography or computer tomography. The Smartshirt is developed and provided by Hohenstein Laboratories GmbH & Co. KG, which has already been used in the ISS experiment Space-Tex 1 & 2. The ballistocardiography measurement is being carried out in cooperation with the aerospace company DSI Aerospace Technologie GmbH, which is providing the hardware and scientifically monitoring and evaluating the measurements. Medical support for the experiment is provided by the Faculty of Medicine at Bielefeld University.

WICO2 will also provide sensors for light analysis and improved test circuits to collect more detailed information about the light sources. In addition, a localization technology based on IR-UWB will be demonstrated to achieve accuracies below 10 cm to precisely control and navigate free-flying objects and supporting systems such as CIMON followers. Wireless Compose-2 is an updateable and adaptable network, providing an infrastructure for future scientific and medical experiments.

Which technology is used?

The technology used is based on the Impulse Radio - Ultrawideband (IR-UWB). The transmitted pulses spread the signal to be transmitted over a bandwidth of 500 MHz. Compared to a conventional Wireless Sensor Network (WSN) in the 2.45 GHz range, this keeps the spectral power density very low so that other radio-sensitive systems are not disturbed and the system's own communication is also less susceptible to external interference. The technology is also virtually immune to multipath interference, which makes it particularly suitable for applications within enclosed spaces, such as an ISS module. Another feature is the measurement of transit times of the emitted pulses in order to perform a distance measurement. This can then be used to determine the position of several nodes.

Scientific objective

The main scientific objective of the experiment is to provide a flexible and customizable wireless network infrastructure to conduct low-power, lightweight and wireless data transmission experiments on the ISS. For the demonstration, Wireless Compose-2 will conduct several sub-experiments while focusing on the BEAT scientific and medical experiment, which evaluates and demonstrates BCG acquisition and the effects of the space environment on the cardiovascular system. Again, a newly developed smart shirt "SmartTex" will be used to integrate the sensors comfortably on the body.

In addition, Wireless Compose-2 will demonstrate a newly developed IR-UWB hardware to enable precise localization applications and analyze the energy harvesting potential on the ISS.

Die Ziele können wie folgt zusammengefasst werden:

• Betrieb eines drahtlosen Netzwerks zur Sensorüberwachung oder allgemeinen Datenübertragung basierend auf IR-UWB
• Aufzeichnung der Signalqualität des IR-UWB-basierten Netzwerks

• Durchführung des BEAT-Experiments zur Überwachung und Erfassung der BCG-Daten eines Astronauten

  • Signalpegel: Beobachtung der Variation von BCG-Signalen über einen langen Zeitraum im Weltraum
  • Herz: Mapping von BCG-Signalen mit den Herz-Kreislauf-System des Astronauten
  • Anwendungsebene: Machbarkeitsstudie von BCG als Gesundheitsüberwachung für Langzeitmissionen
• Machbarkeit von SmartTex, einem Smart-Shirt mit integrierten Sensoren zur Demonstration eines textilintegrierten Body-Area-Netzwerks unter micro-g
• Demonstration der IR-UWB-Entfernungsmessung, um eine Genauigkeit von weniger als 1 cm zu erreichen
• Untersuchung der Parameter der Lichtquellen zur Verbesserung der Energiegewinnungsfähigkeiten

Da Wireless Compose-2 auch die Möglichkeit von Software-Updates bietet, führt dies zu einer höheren Flexibilität und Anpassungsfähigkeit für zukünftige Anwendungen. Daher wird die Basis-Station von WICO2 nach allen BCG-Sitzungen für die Wiederverwendung in zukünftigen Experimenten auf der ISS verbleiben, die auf der bereitgestellten drahtlosen Netzwerkinfrastruktur beruhen.

The objectives can be summarized as follows:

• Operating a wireless network for sensor monitoring or general data transmission based on IR-UWB
• Recording the signal quality of the IR-UWB-based network
• Conducting the BEAT experiment to monitor and collect the BCG data of an astronaut:

• Signal level: Observation of the variation of BCG signals over a long period of time in space
• Heart: Mapping of BCG signals with the astronaut's cardiovascular system
• Application level: Feasibility study of BCG as health monitoring for long-term mission

• Feasibility of SmartTex, a smart shirt with integrated sensors to demonstrate a textile-integrated body-area network under micro-g
• Demonstration of IR-UWB ranging to achieve less than 1 cm accuracy
• Study of light source parameters to improve energy harvesting capabilities

As Wireless Compose-2 also offers the possibility of software updates, this leads to greater flexibility and adaptability for future applications. Therefore, the base station of WICO2 will remain on the ISS after all BCG sessions for reuse in future experiments that rely on the provided wireless network infrastructure.

Carrying out the experiment

The WICO Experiment hardware consists of 4 wireless modules and a central unit that is supplied with power via USB:

• 2 Anchor-Motes: These units are attached to fixed positions within the Columbus module. They are used to provide ranging measurements and analysis data.
• 1 Energy harvesting mote: This mobile unit contains solar cells and investigates the possibility of generating energy from the Columbus module's internal light sources to power electronic components.
• 1 Comm module and SmartShirt with integrated sensors: The SmartShirt is used for BCG measurement and is connected to the Comm module, which forwards the data to the network.
• 1 Base station: This is the central unit that performs several tasks: Network management, collection of accumulated data and storage of these on an SD card. This is how the scientific data is transmitted to the ground segment. The Base Station is permanently supplied with power via a USB cable.

The experiment consists of 2 operating modes in which different aspects are investigated:

• Normal mode: In normal mode, ranging and energy harvesting analysis data are generated and continuously sent to the base station.
• BCG mode: In BCG mode, a BCG session takes place in which a ballistocardiography measurement is performed on the astronaut. This usually lasts 10 minutes.

Why the ISS?

The ISS was specifically selected as a test environment to demonstrate the capabilities of a WSN for future and post-ISS activities. The evaluation of the experiment will help to analyze potential applications of the technology for unmanned and manned space flights and derive obstacles and limitations for operation in very specific environments comparable to the ISS modules. This includes satellites being developed at the Institute of Space Systems that will benefit from this wireless technology.

The practical BEAT experiment will also collect very important physiological data on human cardiovascular parameters and their changes over a long period of time in zero-g. Thus, the collected data is of high interest, e.g. for further scientific investigations on site, for future health monitoring systems in space and a possible technology transfer in terrestrial applications. This is because ballistocardiographic measurement is not only interesting in the medical or sports-medical field, but can also be used in this form as a constant companion in fitness wristbands and watches, making it suitable for mass use to monitor and retrieve important heart parameters at any time, even in healthy people. By using promising algorithms, sensors can be used that make the product affordable for the end user and could be used as wearables.

In addition, the combination with a smart shirt is also interesting in the medical and sports-medical field, as it provides more precise data to monitor important vital functions that would normally only be possible with expensive devices or measurements such as computer tomography. The network to be used, which is based on ultrawideband and enables the localization of objects, can also be used wherever GPS signals are not received or are disturbed, e.g. in large warehouses, underground mining and other relevant indoor applications, so that there is also great potential for technology transfer here, not only in the aerospace industry.

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