Crew time in a space greenhouse using data from analog missions and Veggie.

Crew time requirements for human space exploration missions is as critical as mass, energy, and volume requirements. However, it has only been sporadically recorded in past analog and space missions for plant cultivation. In this retrospective study on crew time data collected in various analog facilities and on the Veggie hardware on ISS, we propose a methodology for efficient categorizing and reporting of crew time in space plant growth systems. Crew time is difficult to capture in operational environments, and this study intends to harmonize these efforts among different locations. This article also provides a current database for required crew time in several plant growth hardware and facilities, on the ISS, and on Earth. These data could serve mission planners as a baseline to establish standardized activities and extrapolate crew time needed to operate future plant growth units. Finally, we discuss how crew time needed for plant cultivation will change in future exploration missions, based on choices made for plant species, watering systems, level of automation, and use of virtual assistants, among others. Crew time will need to be accounted for as a decisive factor to design future space greenhouse modules.

Crew time and workload in the EDEN ISS greenhouse in Antarctica.

The goal of the EDEN ISS project is to research technologies for future greenhouses as a substantial part of planetary surface habitats. In this paper, we investigate crew time and workload needed to operate the space analogue EDEN ISS greenhouse on-site and remotely from the Mission Control Center. Within the almost three years of operation in Antarctica, different vegetable crops were cultivated, which yielded an edible biomass of 646 kg during the experiment phase 2018 and 2019. Operating in such a remote environment, analogue to future planetary missions, both greenhouse systems and remote support capabilities must be carefully developed and assessed to guarantee a reliable and efficient workflow. The investigation of crew time and workload is crucial to optimize processes within the operation of the greenhouse. For the Antarctic winter seasons, 2019 and 2020, as well as the summer season 2019/2020, the workload of the EDEN ISS greenhouse operators was assessed using the NASA Task Load Index. In addition, crew time was measured for the winter season 2019. The participants consisted of on-site operators, who worked inside the EDEN ISS greenhouse in Antarctica and the DLR remote support team, who worked in the Mission Control Center at the DLR Institute of Space Systems in Bremen (Germany). The crew time results show that crew time for the whole experiment phase 2019 required by the on-site operator team 2019 is approximately four times higher than the crew time of the corresponding remote support team without considering planning activities for the next mission. The total crew time for the experiment phase 2019 amounts to 694.5 CM-h or 6.31 CM-h/kg. With the measurements of the experiment phase 2019 it was possible to develop a methodology for crew time categorization for the remote support activities, which facilitates the analysis and increases the comparability of crew time values. In addition, the development of weekly and monthly crew time demand over the experiment phase is presented. The workload investigations indicate that the highest workload is perceived by the remote support team 2019 + 2020, followed by the summer maintenance team 2019/2020. The on-site operator team 2019 and on-site operator team 2020 showed the lowest values. The values presented in this paper indicate the need to minimize crew time as well as workload demands of the operators involved in the operation of future planetary surface greenhouses.

Biomass Production of the EDEN ISS Space Greenhouse in Antarctica During the 2018 Experiment Phase.

The EDEN ISS greenhouse is a space-analog test facility near the German Neumayer III station in Antarctica. The facility is part of the project of the same name and was designed and built starting from March 2015 and eventually deployed in Antarctica in January 2018. The nominal operation of the greenhouse started on February 7th and continued until the 20th of November. The purpose of the facility is to enable multidisciplinary research on topics related to future plant cultivation on human space exploration missions. Research on food quality and safety, plant health monitoring, microbiology, system validation, human factors and horticultural sciences was conducted. Part of the latter is the determination of the biomass production of the different crops. The data on this topic is presented in this paper. During the first season 26 different crops were grown on the 12.5 m2 cultivation area of the greenhouse. A large number of crops were grown continuously throughout the 9 months of operation, but there were also crops that were only grown a few times for test purposes. The focus of this season was on growing lettuce, leafy greens and fresh vegetables. In total more than 268 kg of edible biomass was produced by the EDEN ISS greenhouse facility in 2018. Most of the harvest was cucumbers (67 kg), lettuces (56 kg), leafy greens (49 kg), and tomatoes (50 kg) complemented with smaller amounts of herbs (12 kg), radish (8 kg), and kohlrabi (19 kg). The environmental set points for the crops were 330-600 µmol/(m2*s) LED light, 21°C, ∼65% relative humidity, 1000 ppm and the photoperiod was 17 h per day. The overall yearly productivity of the EDEN ISS greenhouse in 2018 was 27.4 kg/m2, which is equal to 0.075 kg/(m2*d). This paper shows in detail the data on edible and inedible biomass production of each crop grown in the EDEN ISS greenhouse in Antarctica during the 2018 season.

Microbial Monitoring in the EDEN ISS Greenhouse, a Mobile Test Facility in Antarctica.

The EDEN ISS greenhouse, integrated in two joined containers, is a confined mobile test facility in Antarctica for the development and optimization of new plant cultivation techniques for future space programs. The EDEN ISS greenhouse was used successfully from February to November 2018 for fresh food production for the overwintering crew at the Antarctic Neumayer III station. During the 9 months of operation, samples from the different plants, from the nutrition solution of the aeroponic planting system, and from diverse surfaces within the three different compartments of the container were taken [future exploration greenhouse (FEG), service section (SS), and cold porch (CP)]. Quantity as well as diversity of microorganisms was examined by cultivation. In case of the plant samples, microbial quantities were in a range from 102 to 104 colony forming units per gram plant material. Compared to plants purchased from a German grocery, the produce hosted orders of magnitude more microorganisms than the EDEN ISS plants. The EDEN ISS plant samples contained mainly fungi and a few bacteria. No classical food associated pathogenic microorganism, like Escherichia and Salmonella, could be found. Probably due to the used cultivation approach, Archaea were not found in the samples. The bioburden in the nutrition solutions increased constantly over time but never reached critical values like 102-103 cfu per 100 mL in irrigation water as it is stated, e.g., for commercial European plant productions. The surface samples revealed high differences in the microbial burden between the greenhouse part of the container and the SS and CP part. However, the numbers of organisms (bacteria and fungi) found in the planted greenhouse were still not critical. The microbial loaded surfaces showed strong temporal as well as spatial fluctuations. In samples of the nutrition solution and the surface, the amount of bacteria exceeded the amount of fungi by many times. For identification, 16S rRNA gene sequencing was performed for the isolated prokaryotic organisms. Phylogenetic analyses revealed that the most abundant bacterial phyla were Firmicutes and Actinobacteria. These phyla include plant- and human-associated bacterial species. In general, it could be shown that it is possible to produce edible fresh food in a remote environment and this food is safe for consumption from a microbiological point of view.

The Plant Health Monitoring System of the EDEN ISS Space Greenhouse in Antarctica During the 2018 Experiment Phase.

The EDEN ISS project has the objective to test key technologies and processes for higher plant cultivation with a focus on their application to long duration spaceflight. A mobile plant production facility was designed and constructed by an international consortium and deployed to the German Antarctic Neumayer Station III. Future astronaut crews, even if well-trained and provided with detailed procedures, cannot be expected to have the competencies needed to deal with all situations that will arise during a mission. Future space crews, as they are today, will be supported by expert backrooms on the ground. For future space-based greenhouses, monitoring the crops and the plant growth system increases system reliability and decreases the crew time required to maintain them. The EDEN ISS greenhouse incorporates a Plant Health Monitoring System to provide remote support for plant status assessment and early detection of plant stress or disease. The EDEN ISS greenhouse has the capability to automatically capture and distribute images from its suite of 32 high-definition color cameras. Collected images are transferred over a satellite link to the EDEN ISS Mission Control Center in Bremen and to project participants worldwide. Upon reception, automatic processing software analyzes the images for anomalies, evaluates crop performance, and predicts the days remaining until harvest of each crop tray. If anomalies or sub-optimal performance is detected, the image analysis system generates automatic warnings to the agronomist team who then discuss, communicate, or implement countermeasure options. A select number of Dual Wavelength Spectral Imagers have also been integrated into the facility for plant health monitoring to detect potential plant stress before it can be seen on the images taken by the high-definition color cameras. These imagers and processing approaches are derived from traditional space-based imaging techniques but permit new discoveries to be made in a facility like the EDEN ISS greenhouse in which, essentially, every photon of input and output can be controlled and studied. This paper presents a description of the EDEN ISS Plant Health Monitoring System, basic image analyses, and a summary of the results from the initial year of Antarctic operations.