Sensors onboard satellites (e.g., cameras, gyroscopes, temperature sensors) are the core of "mission data collection" and "system health monitoring." The OBC must support sensor data acquisition, processing, and transmission. Therefore, clarifying sensor types and requirements is a prerequisite for OBC selection — the OBC’s interfaces, computing power, and memory must be accurately matched to the sensor configuration.
Satellite sensors can be classified into three categories based on "functional positioning," each imposing different requirements on the OBC:
"Mission-critical sensors" directly serve the satellite’s core mission. Their types depend on the mission goals, and they have the highest requirements for the OBC’s "interface speed" and "computing power":
- Typical Sensor Types:
- EO satellites: High-resolution cameras (e.g., 1m-resolution optical cameras, Synthetic Aperture Radar/SAR);
- Military satellites: Electromagnetic (EM) detectors, spectrum analyzers;
- Scientific experiment satellites: Particle detectors, magnetic field sensors.
- Requirements for OBC:
- Interfaces: Must support high-speed interfaces (e.g., SpaceWire, Camera Link) to match the sensor’s high data output rate (e.g., high-resolution cameras can reach hundreds of Mbps);
- Computing Power: Must have real-time data processing capabilities (e.g., SAR data imaging, optical image compression) to avoid data accumulation;
- Memory: Static memory must be sufficiently large to store raw data collected by sensors (e.g., SAR satellites can generate tens of GB of data per orbit).
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"System health sensors" monitor the satellite’s "physical status" to ensure the normal operation of all subsystems. They have high requirements for the OBC’s "interface diversity" and "real-time performance":
- Typical Sensor Types:
- Power monitoring: Voltage sensors, current sensors (monitoring the status of solar cells and storage batteries);
- Environment monitoring: Temperature sensors, humidity sensors (monitoring the satellite’s internal cabin temperature and OBC component temperature);
- Structural monitoring: Vibration sensors, strain sensors (detecting structural damage caused by launch or on-orbit operation).
- Requirements for OBC:
- Interfaces: Must support basic interfaces (e.g., I2C, SPI, UART) to adapt to various low-speed sensors;
- Real-time Performance: Must collect sensor data periodically (e.g., every 100ms) to promptly detect abnormalities (e.g., sudden voltage drops, excessive temperature);
- Data Storage: Must store "system health logs" in static memory to facilitate ground stations in analyzing satellite status and troubleshooting faults.
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"Navigation and positioning sensors" determine the satellite’s "position" and "attitude," with high requirements for the OBC’s "data accuracy" and "low-latency processing":
- Typical Sensor Types:
- Attitude sensors: Gyroscopes, accelerometers (measuring angular velocity and linear acceleration to calculate attitude angles);
- Position sensors: GPS receivers (civilian satellites), Beidou receivers (Chinese satellites), star trackers (high-precision attitude measurement with an error ≤ 0.1 arcsecond).
- Requirements for OBC:
- Interfaces: Must support dedicated interfaces (e.g., SPI/UART for GPS, SpaceWire for star trackers);
- Computing Power: Must have low-latency data processing capabilities (e.g., converting gyroscope data into attitude control commands with latency ≤ 10ms);
- Accuracy: Must support sensor data "noise suppression" algorithms (e.g., Kalman filtering) to improve positioning and attitude measurement accuracy.
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Before selecting an OBC, follow these steps to ensure compatibility with sensors:
- List all sensors’ "type, data rate, interface type, and data volume";
- Calculate the sensors’ requirements for the OBC: "interface needs" (e.g., 1 SpaceWire, 3 I2C), "computing power needs" (e.g., real-time processing of 100Mbps data), and "memory needs" (e.g., storing 20GB of health logs);
- When selecting an OBC, verify that its interface quantity, computing power, and memory cover the above requirements;
- Request suppliers to provide an "OBC-sensor compatibility test report" to ensure normal data acquisition and processing after actual connection.
In summary, sensor requirements are the "source of demand" for OBC selection. The OBC must be designed around the sensors’ interface, data volume, and processing needs to ensure the satellite’s mission objectives and system health monitoring are achieved.
- Term Consistency: Maintains uniformity in aerospace and sensor terminology (e.g., "Star sensor" → "star trackers" (industry standard), "Kalman filtering" → "Kalman filtering", interfaces like I2C/SPI/SpaceWire retain original abbreviations);
- Precision of Technical Indicators: Accurately translates quantitative parameters (e.g., "1 meter resolution" → "1m-resolution", "≤0.1 arcsecond" → "≤0.1 arcsecond", "Hundreds of Mbps" → "hundreds of Mbps") to meet technical documentation standards;
- Sentence Structure Optimization: Breaks down complex Chinese sentences into fluent English structures (e.g., combining parallel clauses with "and" or relative pronouns) while preserving logical relationships;
- Contextual Adaptation: Adjusts expressions for international readability (e.g., "Beidou receiver" → "Beidou receivers" with a parenthetical note "Chinese satellites" for clarity) without losing cultural/technical specificity.
