CubeSats, as small, standardized, and cost-effective satellite platforms, face significant challenges in attitude control due to their limited size, weight, and power constraints. Star tracker, functioning as high-precision attitude determination devices, have become indispensable components for CubeSat missions.
Attitude determination plays a critical role in the success of satellite missions. For instance, Earth observation satellites must precisely point at target regions, communication satellites need to align accurately with ground stations, and scientific experiment satellites require precise orientation toward specific celestial objects. Traditionally, satellites rely on gyroscopes, magnetometers, and sun sensors for attitude determination. However, these devices often fall short in CubeSats due to limitations in accuracy and resource consumption. In contrast, star trackers actively identify star patterns to deliver high-precision attitude data, making them ideal for CubeSat applications.
Star trackers actively capture images of the starry sky and compare them with preloaded star catalogs to determine a satellite’s attitude. Typically, the process involves several key steps: image acquisition, star detection, centroid calculation, star identification, and attitude computation. As a result, star trackers output quaternions, which describe the satellite’s three-dimensional orientation. For CubeSats, star trackers must perform these steps while meeting strict requirements for miniaturization, low power consumption, and high accuracy.
Performance Requirements for CubeSat Star Trackers
To meet the unique demands of CubeSats, star trackers must satisfy several critical criteria:
Size and Weight: Since CubeSats have limited space, star trackers must be extremely compact.
Power Consumption: Given the constrained energy resources of CubeSats, star trackers need to operate with minimal power.
Radiation Tolerance: High-energy radiation in space can disrupt electronic components, so star trackers must undergo rigorous radiation testing.
High Accuracy: Despite limited resources, star trackers must deliver precise attitude data, typically within a range of 10–30 arcseconds.
Several star trackers designed specifically for CubeSats have gained prominence in the market, each offering unique features:
Redwire Star Tracker: Tailored for CubeSats and nanosatellites, this tracker boasts a compact size, low weight, and minimal power consumption, making it ideal for low Earth orbit (LEO) missions. It achieves 10 arcseconds of cross-axis accuracy and 27 arcseconds of boresight accuracy, with a design life exceeding five years.
AAC Clyde Space ST200: Recognized as one of the smallest and lightest star trackers globally, it measures just 29 x 29 x 38.1 mm and weighs 42 grams (excluding the baffle). It offers 30 arcseconds of accuracy for pitch and yaw, with a maximum power consumption of 1W.
CubeSpace CubeStar: This mid-to-high-precision star tracker features a modular design with customizable baffles. It supports “lost-in-space” and tracking modes, with radiation tolerance up to 24 kRad and a lifespan exceeding five years.
TY-Space NST-3: A radiation-hardened, flight-proven nano star tracker, it suits high-dynamic missions and weighs less than 165 grams.
Star trackers have powered numerous successful CubeSat missions, demonstrating their versatility:
Planet Labs Doves: These Earth observation CubeSats employ star trackers to achieve precise pointing for high-resolution imaging.
Spire Global’s LEMUR-2: Designed for weather and maritime tracking, these CubeSats rely on star trackers for high-precision attitude control.
ESA’s OPS-SAT: A 3U CubeSat used to test new technologies, this satellite utilizes star trackers to enable accurate orbital positioning.
These examples highlight how star trackers empower CubeSats to tackle complex tasks, such as high-resolution imaging and scientific observations.
Future Trends in CubeSat Star Trackers
The development of CubeSat star trackers continues to evolve, driven by technological advancements and mission demands:
Further Miniaturization: New star trackers push the boundaries of size and weight reduction. For example, the TY-Space NST-3 weighs only 165 grams.
Higher Accuracy: Advances in sensor technology and algorithms enhance attitude determination precision, with some products achieving sub-arcsecond accuracy.
Integration with Advanced Platforms: Star trackers increasingly integrate with more sophisticated CubeSat platforms, supporting a broader range of mission types.
Artificial Intelligence and Machine Learning: Some star trackers now incorporate AI and machine learning techniques to improve star identification and attitude calculation robustness, particularly in noisy or stray-light conditions.
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TY-Space Technology (Beijing) Ltd. is professional focusing on advanced attitude optical sensors, especially Star Trackers for space industry.
