Development and demonstration of a Modular Astrobiological Experiments (MAEx) payload for autonomous biological monitoring in Low Earth Orbit (LEO)

Technical Summary: Development and Demonstration of a Modular Astrobiological Experiments (MAEx) Payload

Problem Statement
Spaceflight environments impose unique physicochemical constraints on biological systems, including microgravity, ionizing radiation, altered fluid transport, and confined habitats. While terrestrial analogs (e.g., clinostats, rotating wall vessels) attempt to simulate microgravity, they fail to eliminate gravity vectors entirely and cannot replicate the combined effects of space stressors, such as chronic low-dose radiation and the absence of buoyancy-driven convection. These limitations lead to discrepancies in observed microbial growth, gene expression, and protein aggregation compared to actual orbital conditions. Consequently, there is a critical need for compact, autonomous experimental platforms capable of operating within the strict volume, power, and thermal constraints of Low Earth Orbit (LEO) to validate biological responses and support the development of robust life-support systems for long-duration missions.

Methodology
The authors present the design, development, and ground-based validation of the Modular Astrobiology Experiment (MAEx), a 3U CubeSat-compatible payload (30 × 10 × 10 cm³, ~2.7 kg) engineered for autonomous multimodal biological characterization.

• Payload Architecture: The system is built around a Raspberry Pi 3 B+ controller and comprises four primary subsystems: power distribution, control/data handling, housekeeping, and three integrated analytical modules. The structure utilizes Al 6061 alloy for rigidity and polycarbonate for biochambers, with localized aluminum shielding and multilayer insulation (MLI) for thermal and radiation protection.
• Analytical Modules:
  1. Imaging: A dual-camera system (Raspberry Pi Camera Module 3 Wide) with LED illumination monitors microbial growth dynamics and spatial heterogeneity within biochambers.
  2. Spectroscopy: A custom optical system employs UV (365 nm) and red (630 nm) LEDs coupled with specific photodiodes to measure optical density (OD600) for growth and NADH autofluorescence (Ex/Em: 340/460 nm) for metabolic activity. It also monitors protein aggregation via turbidity.
  3. Electrochemistry: A custom four-channel potentiostat (based on a modified JUAMI design) enables three-electrode measurements (working, counter, reference) to monitor extracellular electron transfer (EET) and redox activity.
• Biological Models: The payload was validated using three representative systems:
  • Shewanella oneidensis MR-1 (facultative anaerobe) for studying metabolism and EET.
  • Ustilago maydis FB1 (radiation-resistant fungus) for stress adaptation.
  • Human γD-crystallin protein for investigating aggregation kinetics under microgravity-relevant conditions.
• Validation: Ground-based experiments were conducted to calibrate the imaging field of view, characterize LED/photodiode temperature dependencies, and validate the potentiostat using ferri/ferrocyanide redox couples. Biological growth kinetics, metabolic fluorescence, and electrochemical currents were measured to establish baseline performance.

Key Contributions

• Modular Multimodal Integration: MAEx uniquely integrates optical (imaging, absorption, fluorescence), electrochemical, and environmental sensing within a single 3U flight-compatible architecture, allowing simultaneous monitoring of cellular proliferation, metabolic state, and molecular assembly.
• Autonomous Control System: The payload features a cyclic execution scheme (30-minute cycles) managed by the onboard computer, enabling autonomous data acquisition, timestamp synchronization, and thermal regulation (25–30°C) without ground intervention.
• Custom Electrochemical Capability: Unlike previous spaceflight payloads that primarily measured bulk electrical output, MAEx incorporates a programmable three-electrode potentiostat capable of applying defined potentials and performing techniques like cyclic voltammetry and chronoamperometry to interrogate mechanistic EET processes.
• Ground-Based Validation Framework: The study establishes a rigorous calibration protocol for optical and electrochemical sensors under controlled laboratory conditions, addressing thermal drift and signal stability to ensure reliable data interpretation in space.

Results

• Structural and Thermal Robustness: Finite element modal analysis identified the payload's dominant natural frequency at 218.72 Hz, well above the host spacecraft's range (70–90 Hz), indicating resistance to launch-induced resonance. Thermal simulations predicted an orbital temperature range of -80°C to -10°C, guiding the design of active thermal regulation.
• Sensor Performance:
  • Imaging: Dual-camera configuration successfully mitigated fisheye distortion, providing clear temporal visualization of microbial growth.
  • Spectroscopy: Calibration revealed that detector output was primarily temperature-dependent rather than voltage-dependent. The system successfully resolved differences in optical absorption between protein samples and controls.
  • Electrochemistry: The potentiostat successfully generated characteristic cyclic voltammograms for the Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ redox couple (midpoint potential ~0.28 V), confirming the functionality of the current sensing and voltage control architecture.
• Biological Validation:
  • Microbial Growth: Imaging and spectroscopy yielded consistent growth curves for S. oneidensis and U. maydis, with calculated doubling times of 12.6 h and 32.9 h (imaging) and 8.9 h and 10.3 h (spectroscopy), respectively.
  • Metabolic Activity: NADH fluorescence measurements showed a peak during exponential growth followed by a decline in the stationary phase, correlating with metabolic activity.
  • Electrochemical Activity: S. oneidensis cultures exhibited a characteristic temporal increase in anodic current density (reaching ~1.2–1.3 A/m²), distinct from abiotic controls, confirming the detection of microbial EET.
  • Protein Aggregation: γD-crystallin samples displayed a sigmoidal increase in absorbance at 340 nm over 30 days, consistent with nucleation-dependent aggregation kinetics, while controls remained stable.

Significance
The paper positions MAEx as a scalable, adaptable framework for integrating multimodal biosensing with autonomous experimental control, representing a Technology Readiness Level (TRL) 4 ground-validated demonstration. The authors claim that this work addresses three central challenges for next-generation space biology: (1) developing modular payload architectures compatible with strict spacecraft constraints; (2) establishing ground-based validation protocols to predict biological responses in space; and (3) identifying model systems relevant to stress resilience and bioregenerative life support. By linking engineering design with biological function across cellular and molecular scales, MAEx aims to inform the deployment of efficient, flight-ready bioregenerative systems for long-duration human exploration beyond Earth orbit. The study emphasizes that while the current work is a ground demonstration, the platform is designed to support future in-orbit investigations into how biological function and biomolecular integrity are shaped by spaceflight conditions.