ICES-2020-51 Mapping CO2 Concentrations Within A Spaceflight Analog Environment Tristan C. Endsley1, Theodore J. Steiner, III2, Forrest E. Meyen3, Kevin R. Duda4 The Charles Stark Draper Laboratory, Cambridge, MA, 02139 USA Marcum L. Reagan5 NASA Johnson Space Center, Houston, TX, 77058, USA Carbon dioxide (CO2) levels onboard the International Space Station (ISS) have been reported to be as high as 10 times greater than ambient levels in a terrestrial environment, which can harm crew performance and productivity. NASA’s personal CO2 monitor provides ISS astronauts with the ability to monitor the CO2 levels, temperature, and humidity via a body-worn system; however, it lacks localization to determine where the sensor measurements were taken. A CO2 sensor was integrated with the Draper Wearable Kinematic System (WKS)— a self-contained, wearable, and hand-portable system for real-time navigation state estimation. The system was demonstrated operationally within the NASA Extreme Environments Mission Operations (NEEMO) mission 23. The NEEMO missions are conducted in the Aquarius Reef Base underwater research facility, located 19 m below sea level off the coast of Florida. This Earth-based spaceflight analog environment creates a realistic platform through which to examine human performance and simulate operations that are representative of living and working in space. The WKS – assembled primarily from commercial-off-the-shelf equipment – analyzes the monocular vision and inertial measurement unit data to generate a real-time navigation state estimation utilizing the Draper smoothing and mapping with inertial state estimation (SAMWISE) algorithm. The WKS+CO2 sensor system tracked crew position, velocity, and orientation while mapping CO2 concentrations within the underwater habitat as a function of time during normal daily crew activities. The results of that testing are discussed, and challenges associated with data collection in this underwater environment are summarized. This capability can provide astronauts, flight directors, and ground support personnel with a better understanding of environmental conditions to improve task efficiency, crew productivity, and appropriate cycle times and operations of the environmental control and life support systems (ECLSS) onboard the ISS. Nomenclature CO2. = Carbon Dioxide COTS = Components Off The Shelf ISS = International Space Station WKS = Wearable Kinematics System MCA = Major Constituent Analyzer ECLSS = Environmental control and life support systems 1 Senior Human Systems Engineer, Human Systems and Visualization Group, Systems Engineering Directorate, 555 Technology Square Cambridge, MA 02139. 2 Principal Member of the Technical Staff, Perception and Localization Group. 555 Technology Square Cambridge, MA 02139. 3 Senior Space Systems Engineer, Space & Mission Critical Systems, 555 Technology Square Cambridge, MA 02139. 4 Principle Space Systems Engineer, Group Lead, Space & Mission Critical Systems, 555 Technology Square Cambridge, MA 02139. 5 NEEMO Mission Commander, Exploration Mission Planning Office, NASA Johnson Space Center, Houston, TX, 77058. Copyright © 2020 The Charles Stark Draper Laboratory, Inc. EKF = Extended Kalman Filter MSCKF = Multi-State Constrained Kalman Filter SAMWISE= Smoothing and mapping with inertial state estimation NHV = Net Habitable Volume NEEMO = NASA’s Extreme Environment Mission Operations USOS = United States On-orbit Segment EVA = Extravehicular activity IVA = Intravehicular Activity IMU = Inertial Measurement Unit GPS = Global Positioning System FLA = DARPA’s Fast lightweight Autonomy 6-DOF = 6 degree-of-freedom I. Introduction levated CO2 levels within the ISS environment are a potential source of acute headaches, dizziness and high blood 1 E pressure, among other serious symptoms . While CO2 expiration is a natural part of the human breathing process (humans generate CO2 at a rate of 0.9-1.2 kg per day), build up and retainment of CO2 gases within the ISS 2 environment can lead to crew performance and productivity degradations . Additionally, CO2 accumulates non- uniformly within the habitable ISS environment, with CO2 concentrations averaging 0.5±0.2% (2.3-5.3 mm Hg) versus terrestrial levels of 0.03% by volume (0.23 mm Hg)3,2. Large variations in the experienced 7-day averages have ranged from 3.39 mm Hg to a peak of 4.50 mm Hg 3,1. Described by James et al. (2010), “…at times and in certain locations CO2 levels can go well above the levels measured by the MCA [Major Constituent Analyzer]. If crewmembers are working in a location with suboptimal airflow, then local concentrations at the breathing zone can be somewhat higher than the module average”2. 4 The NASA Personal CO2 Monitor is capable of quantifying CO2 levels up to 5% by volume. It has already successfully demonstrated the identification of CO2 fluctuations in the ISS habitat environment. The NASA WEAR lab used the device to identify a non-homogeneous dispersion of CO2 gases, which were found to develop high concentration pockets in the ISS. There is, however, no location data associated with these measurements. Despite being able to record nearly continuous measurements of the carbon dioxide in the ISS atmosphere, there is no data to determine where the measurement was taken. Other systems like the Major Constituent Analyzer (MCA)—a mass spectrometer integrated into the ISS— which is primarily used in the United States On-orbit Segment (USOS), only collects data at multiple fixed points in the 5 habitable cabin volume . While this allows highly accurate and continuous measurements of CO2 in the ISS to be collected, the “MCA…can only measure gas constituency at fixed points which are plumbed for sample taking”5 This leaves a void in the ability to map the complete CO2 environment of the ISS to inform operation and cycle times of the onboard Environmental control and life support systems (ECLSS) appropriately. The habitable volume of the ISS 3 5 (790 m ) does not generate uniform dispersion of CO2, leading to high concentrations within some parts of the environment. Other types of platforms, such as those that are affixed to the ISS surface structure are equipped to detect the boundary conditions of the habitation environment, however the lack of convection in space will mean that interior environments are not adequately monitored. Measurement and localization of CO2 concentration is necessary to understand how gases collect and disperse in microgravity and is essential to ensure safety in long-duration space habitats. Our research demonstrates the ability to provide a time-based location associated with each CO2 measurement via a CO2 sensor integrated with Draper’s vision+inertial navigation system—the Wearable Kinematics System (WKS)6,7. The WKS is a generic Figure 1: The Draper Wearable location solution that can be used with many sensors and many Kinematics System 2 International Conference on Environmental Systems investigations. In this paper, we demonstrate the use of the Draper wearable kinematic system (WKS) for the localized detection of CO2 in the NEEMO Aquarius Reef Base Habitat environment, as a proof of concept for the utilization of such technology for the detection of gases and other environmental elements within the ISS habitat (and other environments). II. Background The WKS collects critical data on crew position, orientation, and navigation states within a microgravity environment6,7. As a personalized position and state estimation unit, the WKS can capture critical data on crew activities over time and can quantify crew use of space for the context of informing habitat usage without the use of GPS or affixed structures. The Draper vision + inertial navigation device is a generic technology that provides location and orientation information to any sensor or system integrated with it. This study augments the platform through the integration of a CO2 sensor. A. The Draper Wearable Kinematics System The Draper Wearable Kinematic System (WKS) is a wearable device that estimates the wearer’s position and attitude in dynamic, GPS-denied environments. Draper algorithms calculate position estimates by incorporating measurements from an Inertial Measurement Unit (IMU) and a camera that both reside inside the WKS unit. Vision+inertial navigation systems are a versatile and flexible approach for metric navigation and map building for a variety of GPS-denied applications, such as small air vehicles operating indoors, or personal body-worn navigation systems. These systems, at their core, include a 6 degree-of-freedom (6-DOF) IMU, imaging system, and may also include a baro- altimeter pressure/height sensor. (For operations in Figure 2: Demonstration of WKS Location the ISS microgravity environment, a baro-altimeter tracking on the ISS mock up will not provide useful information). Our previous work6 utilized a Multi-State Constrained Kalman Filter (MSCKF), a vision-aided inertial navigation algorithm proposed by A. Mourikis, et al8-10. In the MSCKF, the vision and IMU measurements are integrated into a single Extended Kalman Filter (EKF) as opposed to a hierarchical or cascaded filter approach. Several key advantages of the algorithm are that it handles nonlinear visual measurements better than the standard EKF, it is a consistent linearized estimator where navigation uncertainty is accurately represented, the sliding window filter approach allows multi-rate sensor data, and it estimates the camera intrinsic and camera-to-IMU extrinsic calibrations online and therefore