Search Results (443)

Rollable solar panels can increase the available photovoltaic area of CubeSats, but their flexible structure requires a flexible sensor for monitoring surface temperature during operation. In this study, an Ag-based flexible resistance temperature detector (RTD) was fabricated by electrohydrodynamic (EHD) inkjet printing for the rollable solar panel of the 3U CubeSat INHA RoSAT. The sensor was formed on a polyimide (PI) substrate and protected with a PI coating. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to assess the imidization, residual solvent removal, and thermal stability of the coating. The sensor was then evaluated through an eight-cycle thermal cycling test from −25 to 125 °C, tailored with reference to MIL-STD-1540. The coating, heat-treated up to 250 °C, showed clear imide formation and no notable mass loss below 500 °C. During thermal cycling, the sensor exhibited stable resistance behavior with a drift rate of 0.032%/h. The derived calibration equation yielded a mean absolute error of 1.44 °C, while the temperature coefficient of resistance and hysteresis were 0.269%/°C and 1.2% of full-scale output (FSO), respectively. These results support the feasibility of the sensor for integration with rollable solar panels and future on-orbit temperature estimation. Full article

Hydrogen peroxide (H₂O₂) is a promising green propellant for CubeSat propulsion and is compatible with both monopropellant and hybrid propulsion systems. This study investigates the application of silver-coated Triply Periodic Minimal Surface (TPMS) structures as catalyst supports for H₂O₂ monopropellant micro-thrusters and as architected fuel-grain geometries in a hybrid thruster. Four TPMS catalyst architectures Primitive, Gyroid, Diamond, and IWP were fabricated by metal additive manufacturing, coated with silver through electroplating, and experimentally compared with silver pellet and silver-coated mesh catalyst beds. Under the investigated monopropellant operating conditions, the TPMS catalyst beds generally exhibited higher steady-state chamber temperatures than the pellet catalyst and comparable temperatures to the mesh catalyst. Exhaust visualization indicated a transition toward a predominantly gaseous exhaust flow, while characteristic-velocity analysis gave an experimental-to-theoretical c* ratio of 85% for the monopropellant test, although this value is affected by heat loss, nozzle losses, flow losses, and measurement uncertainties. Post-test inspection further showed differences in the spatial distribution of visible surface changes among the catalyst configurations, providing qualitative evidence of differences in catalyst condition. For the hybrid-thruster experiments, the selected TPMS catalyst configuration was subsequently used to investigate five ABS fuel-port geometries, including straight-port, multi-port, and Gyroid TPMS designs. Under constant oxidizer mass-flow conditions, the average fuel regression rate decreased with increasing initial burning surface area. A geometry correction factor based on the ratio of the straight-port burning surface area to that of the corresponding geometry reduced the mean absolute prediction error of the classical regression-rate correlation from an average of 209% to 15%. These results demonstrate that architected TPMS geometry influences the measured thermal, flow, and surface-utilization characteristics of H₂O₂ catalyst beds, while fuel-port geometry strongly affects the average regression behavior of hybrid fuel grains. The findings provide an experimental basis for further development of geometry-controlled catalyst beds and hybrid fuel grains for small-satellite propulsion applications. Full article

Small-satellite mission design requires joint consideration of trajectory geometry, launch conditions, propulsion capacity, spacecraft mass, and operational lifetime. This study presents an integrated preliminary-design workflow combining Lambert-grid exploration, cascade filtering, and differential-evolution refinement, followed by encounter and spacecraft screening. The workflow is illustrated using Earth–Venus–Mars–Earth, Earth–Moon–Earth–Moon, and Earth–Venus–Earth–Vesta mission contexts. Launch-provided injection is separated from onboard manoeuvre requirements, and the optimization objective is identified as an energy-and-encounter-matching surrogate. An analytical assessment of 20 spacecraft–propulsion configurations shows that increasing the assumed total correction allowance from $0.10$ to $0.40\mathrm{km}{\mathrm{s}}^{-1}$ reduces capacity-compliant configurations from 18 to 15. For a fixed 1538-day benchmark, increasing the assumed 3.5-year microsatellite lifetime by approximately 20.3% removes its lifetime-only exclusion. A 5 kg Nano R3 configuration requires approximately 16.50 days of ideal powered operation to deliver $100\mathrm{m}{\mathrm{s}}^{-1}$, illustrating the distinction between propellant capacity and manoeuvre-time feasibility. The results show that the candidate configuration set depends materially on the adopted screening assumptions. The framework uses patched-conic dynamics and ideal propulsion screening; independent trajectory reconstruction, stochastic robustness assessment, and finite-thrust verification remain outstanding. Full article

An Earth-observation CubeSat cannot downlink every scene, so what to send must be decided in orbit, yet existing onboard systems either fix their priority logic before launch or make it reprogrammable through a heavy encoder an operator cannot inspect. This work presents a mission-programmable triage system whose contribution is architectural: sixteen spectral–textural Sentinel-2 features feed a classifier-agnostic decision layer mapping each patch to four land-cover classes and driving two orbit-reconfigurable modes with no retraining. A 68-parameter logistic classifier, 68 bytes in int8 within a 150 kB executable, reaches Cohen’s κ = 0.838, 0.887 agreement, and 0.849 macro-F1 with the SCL labelling; as the SCL also supplies the labels, this is agreement with the scheme, cross-checked against an independent product (ESRI/IO, κ = 0.78). Mode A ranks scenes against an eight-byte target, cutting downlink by up to 77.7%. Mode B emits a few-hundred-byte alert reaching 88.6% precision against Hansen Global Forest Change at 28.8% recall, falling below chance on diffuse loss (Mekong–Laos) and alerting on 1.78% of sub-zones across six low-prevalence controls. At 27 s and 37 J of incremental energy per scene on a commercial ARM64 proxy, this interpretable, byte-scale decision layer turns the downlink into a selective, verifiable instrument. Full article

Wildfire detection and characterization from space critically depend on accurate thermal infrared measurements across a wide dynamic range. OroraTech’s SAFIRE payloads feature mid-wave infrared (MWIR) and long-wave infrared (LWIR) bands optimized for this purpose, yet the volume and power constraints of many CubeSat platforms preclude the use of onboard calibration sources. This reflects a broader limitation of current Earth observation systems: the absence of robust calibration and validation methodologies at high brightness temperatures relevant to active fires. We evaluate the potential of using thermophysical models (TPMs) of the Moon as a vicarious calibration reference for calibration transfer between instruments. The Moon reaches surface temperatures of up to 400 K, offering a stable target in the thermal domain that is visible from many different orbits. Previous research has established the use of TPMs for Moon observations in the infrared; however, uncertainties in surface properties remain, particularly in the mid-wave infrared. We investigate these effects using SAFIRE observations of the lunar surface acquired over a wide range of lunar phase angles (from waxing $-81.5°$ to waning +122.2°). We constrain the TPMs using observations from the Sentinel-3 Sea and Land Surface Temperature Radiometer (SLSTR) fire channels and uncover a 5.2% inter-sensor disagreement in the MWIR between Sentinel-3A and Sentinel-3B at high brightness temperatures, corresponding to ∼2.2 K at 400 K. Applying the same methodology to observations of our SAFIRE payloads bounds the calibration transfer error at 5.8% in the MWIR and 4.2% in the LWIR for lunar phase angles within ±45°. These results establish lunar vicarious calibration as a viable approach in the thermal domain for high-temperature applications, providing a pathway toward improved fire radiative power retrievals and enhanced global wildfire monitoring. Full article

This paper presents the mission concept and design of a low-cost stratospheric balloon payload developed for the measurement of gamma rays, X-rays, and atmospheric radiation. The payload integrates multiple sensors, including a NaI(Tl) scintillation detector coupled to a photomultiplier tube, a Geiger counter for total radiation counting, and a BME280 environmental sensor for temperature, pressure, and humidity measurements. A Raspberry Pi Zero is used as the central data acquisition and control unit, enabling real-time logging and processing of sensor data. Positioning and tracking are achieved through GPS modules, including a SIM-based tracker for telemetry and payload recovery. Additional instrumentation such as visible and infrared cameras provides contextual imaging of atmospheric conditions during flight. The system is designed to be lightweight, power-efficient, and modular to meet the constraints of a high-altitude balloon. The configuration evaluated in this study is a laboratory engineering prototype intended to establish functional integration and preliminary spectral performance. It has not yet undergone mechanical vibration, shock, low-pressure, or low-temperature qualification; consequently, flight robustness is not claimed in the present work. Laboratory calibration experiments using a multi-channel analyser were conducted to characterize the spectral response of the radiation detectors and validate measurement capabilities. The resulting spectra were compared with reference data to confirm detector performance. The payload architecture enables simultaneous acquisition of radiation, environmental, and positional data throughout ascent. Balloon-borne measurements therefore can capture a transition from ground-dominated gamma radiation to a regime increasingly governed by cosmic interactions in the atmosphere. The laboratory results establish the functional feasibility of the integrated acquisition architecture and provide a foundation for a mechanically secured and environmentally qualified high-altitude balloon payload and a potential CubeSat mission after passing vibrational and thermal analysis. Full article

Severe conditions in hard-to-reach regions, where terrestrial networks are limited, make data backhaul from these areas challenging. In this context, advances in the Space-IoT have created new opportunities for data collection and monitoring using LEO satellites. To address this issue, this paper presents an orbit-aware S&F architecture for data collection from an intelligent ground terminal located in remote areas using a 3U CubeSat orbiting at 500 km altitude in a Sun-synchronous orbit. The designed ground terminal integrates an ESP32 microcontroller and a 433 MHz LoRa module and is enhanced with an embedded satellite pass prediction, Doppler pre-correction, and an adaptive LoRa strategy. The CubeSat utilizes a TOTEM SDR receiver, onboard data buffering, and an S-band downlink with variable coding for throughput enhancement. The orbital model for satellite prediction is validated using Ansys STK software version 12, while UHF and S-band links are evaluated using time-varying link-budget analysis. The adaptive transmission is compared with fixed configurations in terms of usable contact time and data delivered per pass. Results indicate that the proposed system demonstrates the feasibility of a Store-and-Forward mission co-design that combines precise orbit prediction, Doppler compensation, and adaptive transmission for future Space-IoT applications. Full article

This work addresses the design and fabrication considerations of sub-terahertz narrow-band resonators for high performance and low-cost manufacturability. The intended application of these resonators is to realize narrow-band filtering for passive millimeter-wave sounding of upper tropospheric humidity using the 380 GHz water vapor absorption line. Various narrow-band filter designs and manufacturing processes have been considered. The inductive iris waveguide design was chosen for manufacturing. This design yields a resonator response and reliably achieves a bandwidth narrower than 3 percent around 376 GHz. This design and the fabrication technique validate the use of lower-order filter and resonator structures to achieve narrow bandwidths. The experimental results are presented and compared with other recently fabricated filters above 200 GHz. Full article

This work presents a modular, sensor-aware, end-to-end simulation framework for optical camera communication (OCC). The framework combines modified Monte Carlo ray tracing with pixel-level camera modeling, including optical blur, shutter timing, noise, digitization, and modulation-aware signal processing. It produces physically consistent synthetic images from simulated optical propagation and enables communication performance to be estimated through image-domain signal-to-noise ratio (SNR) and theoretical bit-error-rate (BER) calculations. The simulator is applied to intra-satellite optical links as a representative case study involving confined three-dimensional geometries, line-of-sight (LOS) visibility, partial occlusion, and rolling-shutter image formation. Experimental validation under LOS conditions shows good agreement in the dominant spatial-temporal characteristics of rolling-shutter imagery, with a structural similarity index measure (SSIM) of approximately $0.80$. Simulated SNR values range from approximately $20.5$ to $22.6$ dB, compared with measured values between $20.8$ and $24.4$ dB. No bit errors are observed in the experimental sequences, corresponding to finite-length BER upper confidence bounds, while the BER values derived from the simulated images are theoretical estimates obtained from the image-domain SNR under ideal receiver assumptions. Additional simulations using a detailed 12U CubeSat model demonstrate the capability to assess emitter–receiver placement and partial geometric occlusion, including cases in which the visible portion of the source remains sufficient for bitstream decoding. By jointly modeling optical propagation, camera acquisition, and communication metrics, the proposed framework supports early-stage OCC system analysis and configuration trade-offs without requiring immediate hardware implementation. The approach is applicable to other OCC scenarios in which spatial image formation and sensor dynamics influence communication performance. Full article

Spacecraft and launch-vehicle structures require lightweight multipoint monitoring under combined mechanical, thermal, and environmental loads. This study presents an analytical fiber Bragg grating (FBG) sensor-network workflow integrating reference-grating temperature compensation, regional strain assessment, opposite-surface curvature sensing, wavelength-division-multiplexing allocation, and strain-to-shape reconstruction. The deterministic compensation case is used only as a self-consistency check, whereas practical robustness is assessed through 10,000 Monte Carlo trials incorporating packaged-coefficient mismatch, temperature nonuniformity, wavelength noise, strain-transfer variation, drift, and calibration uncertainty. The calibrated estimator achieved a median strain mean absolute error of 1.73 με and a 95th-percentile error of 4.22 με. The defined finite-element benchmarks produced a maximum engine-mount truss strain of 456.2 με under the defined loads and a median full-field panel-reconstruction normalized root-mean-square error of 1.29% for 18 sensing locations with 2 με noise. Conservative WDM analysis yielded 54, 13, and 16 channels for three operating envelopes, and the prescribed random-vibration spectrum produced 6.78 g_rms. These results demonstrate a reproducible numerical proof of concept and define practical limits for compensation, spectral allocation, curvature interpretation, and inverse reconstruction; they do not constitute experimental validation or flight qualification. Full article

This perspective consolidates recent advances that position plasma and metamaterials as a unified metasystem for next-generation space micropropulsion systems. The need for new approaches arises because advanced small form-factor satellites and propulsion systems face physical and technological limits of conventional methods, including restricted scalability, limited electromagnetic control, and insufficient efficiency for complex and long-duration missions. These causes motivate the implementation of concepts based on metamaterials, plasma-based subsystems used in unconventional ways, and engineered ionized media. The paper integrates three complementary domains: plasma-enabled fabrication of complex metamaterials, engineered plasma–metamaterial interaction for controlled electromagnetic environments, and structured plasmas functioning as metamaterials with tunable effective properties. Emerging examples include metasurface-assisted waveguides for compact plasma sources, plasma-induced transparency platforms, machine learning-optimized metamaterial absorbers, and inverse-designed plasma metamaterials. Advances in plasma-based additive manufacturing and hierarchical material synthesis further expand the design space for multifunctional architectures, enabling adaptive, efficient and miniaturized propulsion concepts for CubeSat-class and small-satellite systems. Full article

Anomaly signals in the Attitude Determination and Control System (ADCS) of nanosatellites can significantly degrade mission performance, especially in the absence of robust Fault Detection, Isolation, and Recovery (FDIR) mechanisms. Thus, traditional threshold-based approaches, while portable and compact, may overlook subtle faults, whereby abnormal sensor signals or current spikes within the threshold may compromise the operation of the entire ADCS as a subsystem. Furthermore, the lack of interpretable detection methods further limits the development of reliable machine learning (ML) FDIR solutions. To address these limitations, this work presents a wavelet-based anomaly detection framework that introduces a two-stage hybrid architecture combining a lightweight Convolutional Neural Network (CNN) for anomaly detection with logistic regression for fault classification, both based on discrete wavelet transform (DWT) detail coefficients extracted from sensor and actuator data. The framework was validated using a statistics-based anomaly dataset for a 1U CubeSat ADCS simulated in MATLAB, in which anomalies are introduced at the component level with controlled variations in magnitude, frequency, and waveform, ensuring 99% statistical significance. Additionally, to demonstrate operational feasibility, constraints for onboard implementation were considered by executing the proposed framework in a Processor-in-the-Loop (PIL) environment. For benchmarking, lightweight detection and classification algorithms were compared, including Out-Of-Limit (OOL) and compact machine learning approaches. Finally, to identify the framework’s limitations and trace faulty events to physical phenomena, Gradient-weighted Class Activation Mapping (Grad-CAM), SHapley Additive exPlanations (SHAP), and impurity analysis were performed on the proposed algorithms as primary interpretability tools. Consequently, the results demonstrate accurate anomaly detection and identification to support both autonomous FDIR actions and ground operator decision-making. The proposed validation framework and dataset provide a reproducible basis for advancing anomaly detection onboard nanosatellites. Full article

This paper presents the design and numerical assessment of a compact short-wave infrared (SWIR) optical payload for a CubeSat nanosatellite platform. The proposed payload is intended to provide sequential imaging in selected SWIR bands using a revolver filter wheel while accommodating a long-focal-length optical system within a limited 3U volume. The optical layout is based on a modified Maksutov configuration with an effective focal length of approximately 550 mm and an aperture of 84 mm. The system is designed to achieve a ground sampling distance (GSD) of ≤15 m at an orbital altitude of 500–550 km. For sequential imaging in different regions of the SWIR range, filters with central wavelengths of 1.24, 1.6, 1.9, and 2.1 μm are used together with an additional broadband window. The optical performance was evaluated using spot diagrams and modulation transfer function (MTF) analysis for the selected spectral bands. A preliminary thermo-optical sensitivity assessment was also performed over the temperature range from −20 °C to +40 °C by considering temperature-induced changes in axial distances between optical elements and surface curvatures caused by material expansion. The results indicate that the MTF at the detector Nyquist frequency of 33 lp/mm remains above the selected threshold of 0.1 for the considered spectral bands and uniform temperature states. The proposed configuration demonstrates the feasibility of implementing a compact long-focal-length SWIR payload with filter-wheel-based band selection for CubeSat missions, while maintaining the required calculated image quality within the considered design-stage assumptions. Full article

Onboard artificial intelligence (AI) is increasingly limited less by raw processor availability than by spacecraft-level integration constraints. Modern commercial edge-AI processors can provide orders of magnitude more inference capability than traditional spacecraft processors and, when normalized by spacecraft mass, CubeSat-class platforms can exhibit a very high compute density. This paper introduces compute density, expressed as operations per kilogram and paired with operations per watt, as a practical systems metric for comparing onboard AI capabilities across spacecraft classes. A representative 6U CubeSat case study is used to show that Jetson-class and space-adapted edge processors can enable computer vision, data triage, change detection, and autonomy workloads that were previously impractical on small spacecraft. However, compute density alone is incomplete: useful onboard AI capability is constrained by available power, thermal rejection, radiation tolerance, duty cycle, memory and data movement, and downlink strategy. This paper concludes that future AI spacecraft should be architected through compute power thermal communications co-optimization rather than by selecting the highest peak tera-operations-per-second (TOPS) processor. Full article

University CubeSat programs are often conducted under severe constraints in budget, personnel, schedule, and knowledge continuity, while still requiring sufficient verification to support mission success. This paper presents the verification, testing, on-orbit operation, and anomaly analysis of COSMIC, a 3U university CubeSat developed by Yonsei University in less than eleven months from project kickoff to launch. COSMIC adopted a protoflight model approach, prioritized commercial off-the-shelf components with flight heritage and prior laboratory experience, and concentrated limited resources on subsystem, FlatSat, system-level, environmental, communication, and scenario-based testing. The test program is reviewed against the subsequent on-orbit results to identify which verification activities contributed to anomaly prevention, fault isolation, and recovery. The results show that system-level integration testing, thermal vacuum cycle testing, and scenario testing were particularly effective in revealing interface, software, and deployment-related issues before launch and in supporting early orbit recovery. However, the mission also exposed limitations in recovery-logic verification, long-duration software testing, communication robustness, and independent reset paths. Based on these findings, practical recommendations are derived for resource-constrained university CubeSat teams seeking to tailor verification activities without simply reducing test rigor. Full article