Minimize Eu:CROPIS

Eu:CROPIS (Euglena and Combined Regenerative Organic-food Production in Space)

Spacecraft     Launch    Experiment Complement    Ground Segment    References

Eu:CROPIS is an Earth-orbiting minisatellite of DLR (German Aerospace Center) with the objective to study food production in space in support of future long-duration manned space missions (life sciences). The main payloads are two greenhouses, each maintained as a pressurized closed loop system, simulating the environmental conditions of the Moon or of Mars. Numerous cameras and sensors on board will observe the growth of vegetables (tomatoes) in space. The mission was proposed by the DLR Institute of Aerospace Medicine in Cologne and the Cell Biology Division of the University of Erlangen. Eu:CROPIS is the name of both, the mission as well as the primary payload 1 (payload 1comprises 2 greenhouses, referred to as compartment 1 and compartment 2) on-board the DLR Compact Satellite bus. A mission duration of 18 months is foreseen. 1)

Seeking to simulate the different levels of gravity on Mars and the Moon, engineers at the DLR Institute of Space Systems and the DLR Institute of Composite Structures and Adaptive Systems are developing and building a 250 kg minisatellite, designed to rotate around its longitudinal axis while orbiting Earth at an altitude of about 600 km. In doing so, it will replicate lunar gravity, that is 0.16 times that of Earth, or 0.38 times – the gravity on Mars – depending on the rotational speed. The first of the two greenhouses will operate under lunar conditions over the first six months, while the second greenhouse will operate in a Martian environment for the following six months. During the entire period, the two greenhouses will be fitted in a pressure container made of carbon-fiber composite materials, built to maintain a constant internal pressure of one bar. 2) 3) 4) 5)

Scientific objectives: A problem in human space flight is the processing of urine. Water is the only component that is recycled so far. All dissolved substances such as urea and salts are extracted from the urine and then disposed. In the future however, the urine of habitat residents could be used in a closed system to grow fruits and vegetables after proper conversion. Eu:CROPIS shall prove this concept under varying gravity conditions. Two life support systems within the satellite will be combined for producing biomass out of urine. The used biological systems are: a nitrifying trickle filter system being a nitrogen source and the single-celled algae Euglena Gracilis as oxygen producing element. The algae also protect the whole system against high level of ammonia, which can occur during a low nitrification process.

Euglena uses gravity and light as hints to reach and stay in regions of the water column optimal for photosynthesis and growth. It has been established as a model organism for studying gravity perception of single cells and was subject to several experiments in space. The trickle filter system is made of lava rock, which is used as a habitat for a variety of microorganisms such as bacteria, fungi and protozoa. The high degree of adaptability of this system with respect to organismic diversity allows the use for the degradation and detoxification of various substances passing through the filter tube. As higher plant system small tomatoes (Micro-Tina) will be used for biomass production.

The scientific goal is a seed to seed experiment under gravity levels as on the lunar surface (0.16 g) as well as on the surface of Mars (0.38 g). During each six months lasting experimentation, ion concentrations in the water based flow will be measured by ion chromatography and molecular biological analysis will be performed with Euglena cells. The Eu:CROPIS long term experiment will serve the purpose of feasibility and technology demonstration in the field of combined biological life support systems and gravitational biological research on a compact satellite system.

Eu:CROPIS carries also secondary experiments:

• PowerCells in Space: Payload 2, the experiment is to measure photosynthesis in algae (NASA/AMES).

• RAMIS (Radiation Measurements in Space): The Payload 3 goal is to collect data on long-term exposure to cosmic radiation over the course of the space flight (DLR)

• SCORE: Payload 4 is a technology demonstrator for next generation on-board computing in hardware and software. SCORE was developed by the DLR Institute of Space Systems. SCORE is complemented by a set of three digital cameras that are commanded via SCORE.

The satellite mission was initiated by DLR Programmdirektion Weltraum with overall mission responsibility by DLR/RY (Bremen). Similarly to the BIRD mission, DLR shows its ability to design, develop and operate a satellite completely on its own. The scientific part of the mission is under supervision of DLR Institute of Aerospace Medicine and the University of Erlangen. The ground segment consists of DLR Space Operations with the ground station Weilheim and GSOC as control center.

 

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Figure 1: Artist's rendition of tomato cultivation in a controlled environment for lunar and Mars habitats (image credit: DLR)

 


 

Spacecraft:

The 250 kg spin stabilized minisatellite is being designed and built by the DLR Institute for Space Systems (Bremen) and will be operated by GSOC (German Space Operations Center). Payload 1 and Payload 2 demand different levels of gravity for their experiments, which is realized at different positions within the cylinder. The satellite contains four gyroscopes, two magnetometers and three magnetic torque rods with a maximum magnetic moment of 30 Am2 for attitude control. A single-frequency Phoenix GPS receiver will be used , it has heritage from the missions PRISMA and PROBA-2.

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Figure 2: Artist's rendition of the deployed Eu:CROPIS minisatellite. The deployed configuration has a width of 2.88 m. An S-band antenna is seen in the center of the top plate (image credit: DLR)

EPS (Electrical Power Subsystem): A Li-ion battery and four solar panels provide bus power during sunlight and eclipse operations. The solar arrays are aligned with the satellite z-axis providing 520 W of power on average per orbit.

The satellite is spinning about the principal axis, which is pointed to the sun and will be nearly identical with the spacecraft z-axis. The cylinder body has a diameter of 1.0 m and a length of 1.13 m. The spacecraft mass is about 250 kg.

The on-board software uses the RTEMS (Real-Time Executive for Multiprocessor System) operating system and is composed of the C&DH (Command and Data-Handling) software, the attitude and orbit control software and the on-board navigation software. The C&DH software was newly developed at the Institute of Space Systems, the other software components have heritage from the DLR TET-1 mission.

RF communications: Two S-band antennae ensure stable communication with the ground. One antenna is placed in the center of the top plate; the other one in the center of the bottom plate.

FCP (Flight Control Procedures): Mission operations for Eu:CROPIS are based on FCP that will be validated on the Flight Model (FM) or partially on the Engineering Model (EM). A basic set of flight control procedures for the satellite bus are defined by the spacecraft manufacturer during the EM and FM integration process. For this purpose, the software ProToS (Procedure Tool Suite) is used, which has been developed at GSOC as part of the GSOC-2020 Research and Development agenda. Its purpose is to support creation and execution of Satellite Test and Flight Control Procedures and to provide an automation framework for complex operational scenarios. ProToS has heritage from the EDRS-A mission control software. 6)

The execution of procedures requires a connection to the external interface service of the mission control system GECCOS (GSOC Enhanced Command- and Control System for Operating Spacecrafts). GECCOS, based on SCOS-2000 (Spacecraft Control & Operation System-2000) release 3.1 of ESA, is the new MCS (Mission Control System) of GSOC in 2014. 7)

The execution of procedures require a connection to the external interface service of the mission control system GECCOS at GSOC. After procedure execution and telemetry evaluation ProToS generates a comprehensive execution report - a helpful feature during AIT (Integration and Test). ProToS is therefore a valuable extension of the Central Checkout System, but it also helps to reduce the effort on the operations side, as procedures can be easily imported into the procedure database at GSOC via the generic MOIS (Manufacturing and Operations Information System) XML format.

 

Launch: A launch of Eu:CROPIS as a secondary payload on a SHERPA rideshare mission of the service provider Spaceflight Inc. (Seattle WA) is scheduled for Q4 2017 on a Falcon-9 v1.2 vehicle of SpaceX. The launch site is VAFB, CA, USA. 8) 9)

Orbit: Sun-synchronous orbit, altitude of ~600 km, inclination of ~97.5º.

The shared payloads on this flight are:

• ORS-6 (Operationally Responsive Space-6) with the demonstration payload COWVR (Compact Ocean Wind Vector Radiometer), a minisatellite (~300 kg) mission of the DoD ORS Office.

• EU:CROPIS, a minisatellite (250 kg) of DLR (German Aerospace Center).

• STPSat-5 (Space Test Program Satellite-5) of the USAF.

• BlackSky Global-1 to -4 of BlackSky Global, Seattle, WA, USA.

• HawkEye Pathfinder 1-3 mission

• Iceye (Helsinki, Finland) SAR (Synthetic Aperture Radar) nanosatellite mission.

• NEXTSat-1, a multi-purpose microsatellite mission of KAIST, Korea.

• SkySat missions of Terra Bella. Mountain View, CA, USA.

 


 

Experiment complement: (Payload 1, Payload 2, RAMIS, SCORE)

Once Eu:CROPIS and its scientific payload have reached space, the first stage in the mission will be to activate the greenhouse (Payload 1) that will simulate a lunar environment. During this phase, the satellite will be controlled at DLR/GSOC, while the greenhouse will receive its commands from the DLR/MUSC (Microgravity User Support Center) in Cologne. The trickle filter, with its ravenous inhabitants, will be operated by the DLR Institute of Aerospace Medicine, and the Friedrich-Alexander-Universität of Erlangen-Nürnberg will contribute the euglena.

The second greenhouse(Payload 2) with Martian gravity will be activated six months later: by then, the microorganisms, tomato seeds and euglena will have been exposed to cosmic radiation for six months – the equivalent to a flight to Mars. The DLR Institute of Aerospace Medicine will measure the radiation exposure inside and outside the satellite throughout the entire mission.

 

Payload 1 - EU:CROPIS

The Payload 1 contains a filter column, which is filled with small lava rocks, the CROP (Combined Regenerative Organic-food Production) filter. The function of the CROP filter is the conversion of ammonia from synthetic urine into nitrate by means of different bacteria living on and in the lava rocks. The filter has a volume of about 600 mL. Driven by pumps, the water circulates through the Payload 1 and the filter column. From time to time small amounts of synthetic urine are injected into the system by means of a small pump. The liquid is then transferred into a water storage tank, which contains the Euglena. Ammonia formed by oxidation and bacterial degradation is absorbed by the Euglena and thus a detoxification is achieved. The illumination of the plants is performed by three LED-arrays. Each LED unit contains also two cameras to take images of the plants from the top. The air in the greenhouse is vented through a chamber with a heat exchanger, which is cooled by direct contact to the base plate of the payload compartment. Condensed water is passively driven back into the water tank.

During the mission, tomato seeds will germinate and produce small cosmic tomatoes under the watchful eye of 16 cameras. Key helpers that enable this growth will also be transported into space: first, an entire colony of microorganisms inhabiting a trickle filter will convert synthetic urine into easily digestible fertilizers for the tomatoes. Second, the single-cell organism Euglena will also be on board to protect the hermetic system from excessive ammonia and to deliver oxygen. LED (Light-Emitting Diode) light will be used to provide the day/night rhythm that the Euglena and tomato seed require. A pressure tank will replicate the Earth's atmosphere.

"Ultimately, we are simulating and testing greenhouses that could be assembled inside a lunar or Martian habitat to provide the crew with a local source of fresh food. The system would do this by managing the controlled conversion of waste into fertilizer," says DLR biologist Jens Hauslage, head of the scientific part of the mission. In a lunar habitat, for instance, the Payload 1 (greenhouse) would be located in the astronauts' 'home' in a simulated Earth atmosphere. Urine would be one of the waste products the astronauts would produce in abundance. Here, the plants would have to adapt to reduced gravity conditions – the gravitational pull on the Moon is approximately one sixth of what it is on Earth, and on Mars it is around one third.

Turning waste into fertilizer – under controlled conditions: "A compost heap used for recycling purposes would not be controllable on a space station or in a habitat, which is why we use our trickle filter CROP. It fulfils the same function as normal soil, but is controllable." This is why the lava stones fitted in the trickle filter will initially be 'infected' with dried soil before Eu:CROPIS is sent off on its journey. This inoculation will allow a variety of organisms to settle in the porous, expansive surface of the lava stone, which they will use as a habitat. Once it reaches space, synthetic urine mixed with water will be trickled on the habitat every two to three days, triggering a true competition for food between these microorganisms. Here, nitrite is used to convert the harmful ammonia into nitrate, which is then added to the tomato seeds as fertilizer.

 

Payload 2 - PowerCell Payload

DLR (German Aerospace Center) invited NASA/ARC (Ames Research Center), Moffett Field, CA, to participate in their Euglena & Combined Regenerative Organic-food Production In Space (Eu:CROPIS) mission. The PowerCell Project is managed by Ames Research Center and leverages experience gained from prior flight experiments aboard multiple small- satellite space biology missions, the Space Shuttle, and the ISS (International Space Station). 10) 11) 12)

Vision: To derive the greatest benefit from long- term human space exploration, we must learn to utilize resources found ‘on site' (or in situ) to reduce or eliminate reliance on resupply missions from Earth. On Earth, we rely on "primary producer" organisms, both plants and microbes, to transform basic resources like sunlight, water, and atmospheric gases (carbon dioxide, nitrogen) to provide the foods, or basic energy bundles, for "consumer" organisms (like us). Cyanobacteria and algae are two types of microbial primary producers capable of transforming solar energy, carbon dioxide, and water into carbohydrates, such as sugars, through the process of photosynthesis.

Using the tools of genetic engineering, synthetic biology will let us design specific PowerCell mini-ecologies that leverage the capabilities of selected microbes to perform useful tasks even as they cooperate with one another. Each PowerCell ecology will be customized for performance in a unique setting, taking advantage of in situ materials and energy sources to generate, on-demand, useful products that satisfy specific needs of long-term human presence away from Earth.

Using the tools of genetic engineering, synthetic biology will let us design specific PowerCell mini-ecologies that leverage the capabilities of selected microbes to perform useful tasks even as they cooperate with one another. Each PowerCell ecology will be customized for performance in a unique setting, taking advantage of in situ materials and energy sources to generate, on-demand, useful products that satisfy specific needs of long-term human presence away from Earth.

The PowerCell experiment began with a concept developed by the Brown-Stanford 2011 International Genetically Engineered Machine (iGEM) team: What if we could co-culture photosynthetic microbes to produce nutrients to feed other cells naturally productive or bioengineered for specific tasks such as chemical, material or food production for use off planet? Cyanobacteria are photosynthetic (converting CO2 to sugars) and many are diazotrophic (converting atmospheric N2 into biologically usable forms of nitrogen).

However, they are difficult to engineer. The solution was to make a cyanobacterial strain excel at producing and secreting extra photosynthate, allowing it to feed a second organism that is more easily modified to produce a range of products for use in space or on non-terrestrial bodies. For this purpose, Anabaena spp. 7120 was engineered to continuously secrete sucrose into its environment, resulting in the development of the Anabaena PCS1, or "PowerCell", strain during the course of the summer 2011 session of iGEM. For a flight production organism, Bacillus subtilis 168 and similar strains are ideal candidates, possessing flight heritage, exceptional hardiness, and a well-cataloged history of genetic modification.

The 2013 Stanford-Brown iGEM team prototyped a protein-based sucrose sensor for B. subtilis that indicated that PowerCell worked by producing a fluorescent protein when B. subtilis metabolized sucrose. From the iGEM "proof-of-principles" we developed a full-mission concept and began lab tests for payload development. Presented here is a description of the lab-based developmental work as we prepare for flight.

PowerCell payload on the EU:CROPIS mission: This platform will be ideal to test another question raised in the original iGEM concept: "Will there be a significant change to synthetic biology operations due to gravity?" If we are to use synthetic biology in space, we must understand how variable gravitational forces affect the insertion of new genes through transformation and their subsequent function. The satellite will establish artificial gravity by rotating about its axis, providing payloads onboard with reduced gravity that includes the lunar-to-martian range. The PowerCell payload on the Eu:CROPIS mission will investigate how different artificial gravity levels affect bacterial cell growth, genetic transformation, and exogenous protein production. In this manner the PowerCell mission will take the first steps in transitioning lab-based synthetic biology into a space exploration tool at-destination while demonstrating the practicality of its hardware for smallsat applications.

Table 1: Some background on the original PowerCell development (Ref. 11)

PowerCell Spaceflight Payload: In its first flight, the PowerCell Payload will investigate the performance of month microbial mini-ecologies containing both photosynthetic microbes and consumer organisms. Photosynthetic cyanobacteria will produce the carbohydrate sucrose (table sugar), which will feed Bacillus subtilis, a robust bacterium commonly found in soil and the gut.

As its mini-ecologies are exposed to several levels of artificially generated gravity, the PowerCell concept will be evaluated for compatibility with non-terrestrial environments. A rotating spacecraft will provide gravity similar to the moon for six months, and Mars for an additional six months. The results will be compared to a series of identical experiments on Earth.

In each gravity regime a payload fluidic system will deliver nutrients to 48 microwells integrated into a microfluidic carrier or "card". Each microwell houses a PowerCell mini-ecology in dried form suitable for many months of stasis. The temperature is stabilized as the dried organisms hydrate and 4 miniature LEDs provide white light to initiate photosynthesis. Periodically, a sequence of optical measurements is made by the other 3 LEDs—violet, cyan, and red—plus a dedicated photodetector to monitor the growth and composition of each well's ecosystem.

Trends and changes in the data will tell us how well the primary producer—the cyanobacterium Anabaena—generates sucrose to support the growth of B.subtilis—the consumer—at the current gravity level. In addition to producing sucrose through photosynthesis, Anabaena can "fix" dissolved nitrogen gas to generate plant-fertilizing nitrogen compounds, a key trait of this particular PowerCell ecology.

A second objective of the PowerCell Payload is to conduct synthetic biology remotely in outer space. The basic technique for introducing genetic material into a living cell, "transformation", involves the transfer across a cell's encasing membrane of molecules carrying genetic information. The PowerCell Payload will examine if and how reduced gravity levels impact transformation processes.

Instrumentation:

The PowerCell hardware is an improved version of hardware flown on PharmaSat, a previous biological payload designed and built by NASA/ARC. The PharmaSat mission, launched May 19, 2009 from NASA's Wallops Flight Facility, was a successful 96 hour test of the effect of antifungals on yeast growth in microgravity.

The PowerCell hardware consists of two hermetically sealed enclosures (each ~21 x 29 x 8 cm and 4.3 kg) as depicted by the solid model in Figure 3, which will be integrated onto the compact satellite. Each enclosure contains two separate and identical payload modules with a 48-segment 3-color optical density or absorbance measurement system, grow light system, microfluidic system for nutrient delivery and waste flushing, plus thermal control and internal environmental sensing including temperature, pressure, humidity, and acceleration. The fluidic card design allows for multiple experimental conditions at each gravity regime in each of the four rows of the card's 4 x12 array of experiment wells through independent fluid delivery. Each of the twelve wells within each row could in principle be loaded with a different sample, although the scientific requirements for replication translate into two to three experimental parameters per row. The optics system measures growth via LED light absorbance at several wavelengths and allows for photosynthetic growth.

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Figure 3: PowerCell enclosure hardware (image credit: NASA/ARC)

Fluidic card: Each payload module has a self-contained fluidics system consisting of a reagent container assembly, a valve manifold for pumping fluids, the experiment card that receives the fluids, and a waste manifold/bag. The payload experiments are carried out within the experiment card. Each row is served by a separate fluid delivery line, allowing for four different fluidic protocols to be carried out within a single module. The wells are self-contained experimental samples, with 0.20 µm filters on the inlet and outlet to sterilize fluids and isolate organisms. The valve manifold uses four spring-and-solenoid valves for receiving reagents, and five magnetically latched solenoid valves for the outlets. The five outlets translate to each of the four rows of the experiment card plus an outlet to the waste manifold. The card is composed of sandwiched layers of poly(methylmethacrylate) ("acrylic") for the well sides with a clear gas-permeable 50 µm polystyrene capping layer to allow gas exchange. Fluidic cards were produced by ALine Inc (Rancho Dominguez, CA).

Optical measurement system: The PowerCell payload measures OD (Optical Density) of the microfluidics wells at 3 wavelengths using a LED-based optical system. After rehydration with growth media, the B. subtilis grow within the sample wells and experiment progress is assessed by OD. As depicted in Figure 4, each well is aligned with its own AMS-TAOS light-to-frequency detector and set of three measurement LEDs with wavelength peaks at 430, 515 and 636 nm. The LEDs shine light through the well path and TAOS detectors measure the amount of transmitted light. Light is scattered (blocked) by cells (depicted by green and blue ovals) and the difference in transmittance over time used to measure growth. The 636 nm LEDs are useful for measuring cell growth, while comparison of 636 nm LED absorbance to the 515 nm and 430 nm LED absorbance can be used for measuring colorimetric assays. Although they are not part of our current experiment plan, the included broad-spectrum growth LEDs can also be used to facilitate the growth of cyanobacteria or other small photosynthetic organisms.

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Figure 4: Individual well cross section (image credit: NASA/ARC)

Electrical: The PowerCell payload electronics are based on those of PharmaSat. Numerous improvements have been made to the design, and the newer, more miniaturized electronics used in the PowerCell payload allow for greater capability with a lower part count and smaller size. The electronics consist of a single Master printed circuit board (PCB) that interfaces to DLR's compact satellite bus and regulates power and communication, plus LED, Detector, and Valve Manifold PCBs for each experiment. To facilitate reuse on future missions, experiment electronics were designed to be compatible with a standard 2U CubeSat payload form factor supported by a 1U bus, or to interface with a master power/communications unit for use in a larger satellite as in the case of PowerCell's flight.

Software: The PowerCell system software was designed de novo with several advanced features built into the software architecture to allow significant configurability, fault tolerance, and the re-use of code for future biological payload systems. Rather than implementing a hard-coded experiment sequence in the software, a flexible onboard experiment "script" system was incorporated to allow arbitrary experiment sequences to be uploaded from the ground and then executed onboard. A complementary ground tool was developed for the generation of these experiment scripts. One of the advantages of this method is that as the desired experiment sequence was modified during the course of testing, the changes were isolated to the script and not the actual code – this dramatically reduced the amount of software modification during the test phase of the mission. There is also nothing that precludes the upload of a new experiment script during on-orbit operations in the event that a last-minute change is needed or desired.

Because the PowerCell electronics system largely consists of off-the-shelf components which are not radiation hardened, significant effort was made to mitigate single-event upsets in the software. Data redundancy, a multiple voting scheme, and memory scrubbing were some of the techniques used for this purpose. Other implemented features such as an onboard scheduler, bootloader, performance reporter, and a suite of complementary ground/operations software tools helped to increase the robustness of the system.

Payload science experiment overview:

Organism selection: Two microbes were considered for launch aboard PowerCell: the cyanobacterium Anabaena spp. 7120-PCS1 "PowerCell" and the common soil bacterium Bacillus subtilis 168. The ability to withstand long periods of dry storage drove organism selection, as launch constraints require the organisms to survive dark, dry, room-temperature storage for up to 2.5 years without careful temperature regulation prior to rehydration. Initial work focused on different methods of room-temperature stasis for these organisms. Bacillus subtilis has maintained 45% survival after one year of our simulated conditions. The Anabaena spp. 7120-PCS1 is the original concept organism genetically engineered by the 2011 Brown-Stanford iGEM team. Anabaena spp. 7120-PCS1 was dubbed "PowerCell" for the genetic modification that made it leak sucrose into its environment. Unfortunately, PCS1 is not naturally capable of forming the thick-walled dormant akinetes as other members of the genus do. Cells rarely survived longer than two weeks under the environmental constraints of the PowerCell payload. Because the requirement for long-term stasis was not being met, we were unable to fly living Anabaena spp. 7120-PCS1 on Eu:CROPIS.

Other organisms were considered for potential experiments, including Escherichia coli K12 as a production organism because of its widespread use in synthetic biology, and Anabaena cylindrica as a PowerCell as it does form akinetes. However, neither reliably survived beyond one month of storage during stasis testing, eliminating them from the final flight plans.

Cell Growth: Although numerous experiments have investigated the effects of microgravity on organism growth, there are no experiments to date on growth along a gravitational gradient below 1 RCF (Relative Centrifugal Force) as we intend to conduct. We will observe cell growth at 4 gravity regimes: 1.0 (on the ground), 0.52, 0.22, and 0.014 x RCF. These growth curves, which should provide information on low-gravity growth, will be conducted with B. subtilis strains 168 and 1A976 using a rich culture medium commonly used in lab experiments, Lysogeny Broth (LB), and Anabaena extract as growth medium serving the role of PowerCell.

Genetic transformation: As synthetic biology operations rely on our ability to insert new genetic circuits and systems into production organisms, we need to assess the behavior of genetic transformation in destination gravity regimes for the use and maintenance of genetically engineered organisms during missions. Normally lab-based protocols would use electroporation, a method where an electric field is applied to cells to temporarily increase membrane permeability, or heat shock. Neither approach is feasible during the Eu:CROPIS mission. The transformation of chemically-competent cells requires multiple fast freeze-thaw steps and relies on fragile cells. With this in mind, we sought a simple method of transforming hardy cells within a standard production organism. For this we evaluated two isothermal one-step transformation methods for use in B. subtilis and E. coli. B. subtilis is naturally competent and adjustment of the procedure developed by Zhang and Zhang with B. subtilis 1A976 led to a simple one-step process of transformation. For E. coli, polyethylene-glycol (PEG)-based transformation methods proved capable of transforming cells by mixing the cells and DNA with growth medium containing 10% w/v PEG. While E. coli was not ultimately selected due to its poor performance during our stasis experiments, this result led to viable methods for future missions with similar limitations.

Protein production: Since gene activation is known to change over time in space, a concern for synthetic biology is whether or not the activity of inserted gene(s) will also shift. By introducing an exogenous protein, β-glucuronidase, and two native promoters of characterized gene transcription strength, we will understand if the gene activation shift caused by lowered gravity significantly affects our ability to use unicellular organisms as production organisms as predicted by terrestrial lab-based experiments. We will examine the ability of B. subtilis to produce β-glucuronidase by growing cells in the presence of the X-gluc colorimetric assay. The X-gluc assay functions when β-glucuronidase cleaves X-gluc ((5-bromo-4-chloro-3-indolyl-beta-D-glucuronic acid, cyclohexylammonium salt), forming a blue precipitate that our LED system can measure. We will compare the β-glucuronidase expression by the pVeg promoter – a highly expressed constitutive promoter – and the pLiaG promoter – a constitutive promoter repressed by cell stress.

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Figure 5: Schematic view of the PowerCell concept (image credit: NASA/ARC)

In summary, the PowerCell Payload hardware has the potential to be the starting point for an easy-to-use automated experimental system in satellite and other payloads. The microfluidic design allows for the sterile and independent addition of reagents, while the software's drag-and-drop scripting system allows for researchers with no programming experience to create automated experiments. The optical system has shown sensitivity comparable to benchtop spectrometers and its LED wavelengths can be selected to accommodate different experimental conditions.

The PowerCell payload will address simple but important questions for the future of synthetic biology in space. By evaluating the role (variable) gravity plays in microbe viability and growth, it will inform us of the scope of applicable environments for genetically engineered bacteria to be used as an enabling technology. Understanding the subtle impact of gravity on the efficiency of characterized genetic parts like promoters can provide an approximation of how more complex genetic systems developed on Earth will respond to the stresses of new celestial bodies. Even confirming that genetic competency occurs to a degree similar to terrestrial operations allows better prediction of how genetic engineering operations might function in mission environments and be used as a dynamic tool for future development in non-terrestrial environments.

Synthetic biology has already shown enormous potential on Earth to create new medical technologies, materials, and fuels. The renewable nature of synthetic biology and life's own capacity for self-replication and resource utilization indicates great potential for its use in human space exploration. By translating these technologies to use in space, we are making the first steps to drastically reduce the cost and risk of manned space missions, especially on long-term operations. The first steps in testing its use are to re-create the conditions it might face in a mission environment and here we focus on the reduced gravitational force, bringing us closer to implementing synthetic biology as an enabling technology for space exploration.

 

Payload 3 - RAMIS (Radiation Measurements In Space)

The DLR experiment RAMIS will use a radiation detector to collect data on long-term exposure to cosmic radiation over the course of the space flight. The radiation field in space presents a limiting factor for the long-term deployment of astronauts and every other biological system – whether it is plants, animals, or microorganisms. This is why DLR radiation biologists will measure the radiation field on the outer shell and inside the satellite. The data will be used as a basis for further development of radiation field models, also to register the radiation dose to which the symbiotic community will be exposed during its flight on board Eu:CROPIS.

The goal of the RAMIS experiment is to measure cosmic radiation with energy deposition ranging from minimal ionizing protons up to relativistic iron nuclei. The radiation detector principle uses two silicon detectors, each with an active area of 0.5 cm2 and 300 µm thickness that are arranged in a telescope configuration.

RAMIS instrument: 13)

- Size: 140 x 140 x 35 mm3

- Mass: 540 g

- Power consumption: 3 W – 4 W (depending on input voltage)

- Power supply: 12 V (M1), 28 V (M2)

- Internal data storage: 2

- Data rate: 10 MB / day

- TM/TC interface: RS-485.

 

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Figure 6: Photo of the radiation detector RAMIS (image credit: DLR)

 

Payload 4 - SCORE (SCalable On-boaRd computing)

No description available!!!

 


 

Ground Segment

The ground systems in place for command generation, telemetry processing and visualization rely mostly on tools that have been used before in other mission. This approach minimizes the development costs and training effort for the operations team.

Operations concept: The Eu:CROPIS payload has a number of autonomous functions like thermal control loops. Cyclic activities as lighting cycles and the taking of pictures and measurements are also initiated autonomously and do not require commands from ground on a daily basis. All other payload activities e.g. the start of an experiment or configuration changes are commanded on request from the PI (Principal Investigator). The request is made online through a web form, where the procedures and uplink modalities are specified. For all necessary functions flight control procedures are available at the control center. If the procedure requires parameter input from the PI or is to be executed time-tagged, the missing values are transmitted to GSOC through a defined format and interface, checked for consistency and merged with the procedure. This is an automatic process that takes a couple of minutes, but does not require manual interaction. Most procedures do not have configurable parameters though (so-called ready-procedures), and are already available in the MCS (Mission Control System). The spacecraft operator sends the procedure after approval has been given from the Flight Director in the web form. The PI is then able to remotely follow the execution process from the real-time telemetry shown in a tool provided by GSOC. The process of recommendation handling and the TM/TC interfaces between external users and GSOC are shown in Figure 7 (Ref. 3).

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Figure 7: On request from the PI flight control procedures are sent to the satellite. Parameter values for procedures are transmitted via XML files, which are processed automatically (image credit: DLR)

The close cooperation between the space segment and ground segment teams has contributed to a cost reduction of the mission operation and preparation. The experience and heritage within the ground segment could be considered in an early stage of the C&DH software design. The efficiency of data storage and retrieval for example will profit from the mission planning tools at GSOC in use for the FireBird mission.

Hence, Service 11 and Service 15 of the ECSS PUS (Packet Utilization Standard) were implemented in the C&DH software. A special case in this matter is the downlink of image files taken inside the greenhouse, and whose sizes exceed the maximum size of a single telemetry source packet. It was decided to transfer greenhouse images via PUS Service 13, the dedicated service for the transmission of large data. For this purpose minor enhancements had to be made in turn on the ground segment side to guarantee the maximum scientific return.

During the LEOP (Launch and Early Orbit Phase) the satellite will be controlled and monitored at GSOC. The LEOP ground station network guarantees a high number of contacts to the satellite, and allows for a quick response to on-board events and the transmission of critical procedures. It will consist of the following antenna sites:

- Weilheim (WHM) of DLR

- Svalbard (SGS) of KSAT

- St. Hubert (SHB) of CSA

- Saskatoon (SKT) of CSA

- O'Higgins (OHG) of DLR.

After separation from the launcher, the satellite will autonomously perform the initialization sequence. It will power the nominal side of hardware, i.e. the OBC (On-Board Computer) will start the on-board software and activate the AOCS system. The S-band transmitter will be switched on 30 minutes after separation because of a requirement from the launcher. The first step in the attitude control and acquisition sequence is to decrease the tip-off rates from the launcher. Following, the satellite z-axis is pointed perpendicular to the sun direction in order to allow for an illumination of the undeployed solar panels, which are still fixed around the curved area of the cylinder. A rotation around the z-axis is established at 1 rotation per minute (rpm), which is why this configuration is also referred to as "BBQ-attitude". The four panels are illuminated one after another and a stable thermal condition is generated.

For routine operations on-board capabilities are employed to facilitate operations and to take care of back-ground tasks. These are time distribution, data collection and downlink, parameter monitoring, thermal and attitude control as well as FDIR (Fault Detection, Isolation and Recovery). Monitoring and control of the satellite including replay of recorded data will be conducted via the S-band uplink and downlink channels. The contacts between the control center and the satellite will primarily be used for the uplink of procedures to update the mission timeline, and for dumping of housekeeping and science data. Four ground station contacts per day will be scheduled in the routine phase to dump a total volume of 120 MB ±15% comprising of:

- 80 MB for Payload 1

- 10 MB for Payload 2

- 10 MB for Payload 3

- 10 MB for Payload 4

- 10 MB for S/C bus.

EuCROPIS_Auto0

Figure 8: Exchange of data products in the routine phase. Science data and platform housekeeping telemetry are available on the GSOC SFTP (Secure File Transfer Protocol) server not later than 45 minutes after the contact. Additional products like the orbit determination are also provided (image credit: DLR/GSOC)

 


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2) "Eu:CROPIS – Growing tomatoes in space," DLR, April 24, 2014, URL: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10080/150_read-10095/#/gallery/14438

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7) C. Stangl, B. Lotko, M.P. Geyer, M. Oswald, A. Braun, "GECCOS – the new Monitoring and Control System at DLR-GSOC for Space Operations, based on SCOS-2000," SpaceOps 2014, 13th International Conference on Space Operations, Pasadena, CA, USA, May 5-9, 2014, paper: AIAA 2014-1602

8) "DLR Signs Launch Services Agreement with Spaceflight Inc.," Spaceflight Inc., July 8, 2014, URL: http://www.parabolicarc.com/2014/07/08/dlr-signs-launch-services-agreement-spaceflight/

9) United States commercial ELV launch manifest, January 26, 2017, URL: http://www.sworld.com.au/steven/space/uscom-man.txt

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11) Griffin McCutcheon, Ryan Kent, Ivan Paulino-Lima, Evlyn Pless, Antonio Ricco, Edward Mazmanian, Steven Hu, Bruce White, Dzung Hoang, Elizabeth Hyde, Earl Daley, Greenfiled Trinh, Brett Pugh, Eric Tapio, Karolyn Ronzano, Charles Scott Richey, Lynn J. Rothschild, "PowerCell Payload on Eu:CROPIS - Measuring Synthetic Biology in Space," Proceedings of the 30th Annual AIAA/USU SmallSat Conference, Logan UT, USA, August 6-11, 2016, paper: SSC16-XI-04, URL: http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3405&context=smallsat

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13) Thomas Berger, "Future experiments onboard the ISS and beyond," 20th WRMISS (Workshopp on Radiation Monitoring for the International Space Station) , September 8-15, 2015, Cologne, Germany,URL: http://wrmiss.org/workshops/twentieth/Berger_EuCPAD.pdf
 


The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).

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