The on-orbit calibration technology for internal and external parameters of remote sensing camera is the key to guaranteeing the imaging quality and positioning accuracy. Conventional landmark-based methods are not suitable for satellite missions where landmarks do not work nor for the on-orbit autonomous calibration of large remote sensing constellation. Hence, we introduced an on-orbit geometric calibration method based on star sources observation. By adjusting the satellite attitude, the camera and star sensor can simultaneously detect the star sources. Taking the star sources as control points, a high-accuracy “camera-star sensor” joint geometric calibration model integrating the space–time effects and optical imaging is established, which precisely decouples the deviations caused by the relativistic effects, the distortion of internal parameters, and the bias of external parameters. Furthermore, the procedures of the method are designed for on-orbit autonomous calibration. On-orbit experiments were carried out in several satellites, such as Jilin-1 ShiPin07 (JL-1 SP07). The results showed that the accuracy of internal calibration could reach 0.052” and the error of external installation matrix was within ±1.4”. Therefore, the method is attractive for actualizing on-orbit autonomous geometric calibration accurately and complements the conventional methods where the availability of landmarks is hard.

The precise attitude determination and imagery positioning is crucial for remote sensing satellites to accomplish diverse observation missions. However, the complex fluctuations of environmental conditions result in severe and time-variant camera misalignment, which degrades the inertial attitude determination precision of optical payloads greatly and further hinders the improvement of positioning accuracy. Here, we develop a high-accuracy real-time attitude determination and imagery positioning system. With multiple laser sources integrated on the camera focal plane and a retroreflector reflecting the laser into a star tracker, the active optical monitoring path between the camera and the star tracker is constructed and provides the ability to monitor the camera misalignment. Using a dichroic mirror, the star tracker can detect the stars and the laser simultaneously. Then, the camera attitude determination and imagery positioning model based on the “star-laser” joint detection is established, which can precisely monitor the camera misalignment by the laser imaging and determine the inertial camera attitude combining with the star imaging. The ground simulate experiment is conducted and the results demonstrate the accuracy and effectiveness of the proposed method in monitoring the camera misalignment. Therefore, the proposed method provides an innovative idea for high-accuracy positioning.

CubeSats have extensive applications in the realm of remote sensing. However, due to size constraints, attitude determination and control systems (ADCS) often adopt an integrated and densely packed structure. This leads to simple interference in the magnetic field measurements from components like reaction wheels and magnetorquers, resulting in magnetometer failures. Furthermore, the magnetic interference compromises the ability to dump the angular momentum of CubeSats. This leads to attitude control and remote sensing mission failures. To address these challenges, we introduce a dynamics-sensing, magnetic, fault-tolerant attitude control method that achieves attitude control without a priori magnetic field information generated from a magnetometer, restoring the remote sensing capabilities of CubeSats under magnetic failure. The proposed geomagnetic field sensing method, based on the temporal expansion geomagnetic vector calculate algorithm (GVCA), decouples the observation equations in three axes through control segmentation in the time domain to address the singularity issue of the Kalman coefficient matrix. Additionally, the magnetic field vector can be obtained in real time with acceptable computational consumption. Moreover, utilizing this real-time magnetic field information, the fault-tolerant control strategies and multi-mode control laws can progressively restore destabilized CubeSats to their regular states without performance degradation. We conducted numerical simulation experiments to evaluate the effectiveness of our method and system. Beyond the numerical simulations, we also built hardware systems. We designed and implemented a plug-and-play (PnP) ADCS to apply our methodology, further supporting CubeSats’ high-precision remote sensing. Furthermore, with the aid of a space environment simulation platform, we verified the performance of our system and method under conditions simulating the actual space environment. Ground testing demonstrated that our proposed method was able to identify the magnetic field and achieve high-performance attitude control with magnetic field measurement failures. The system’s pointing accuracy was better than 0.02 degrees, and the attitude stability surpassed 0.003 degrees per second.

The star tracker is the most accurate attitude determination device that guarantees the success of a spacecraft mission. On-orbit calibration of star trackers is essential to correct the deviation of geometric parameters caused by fluctuations of space-environment conditions. However, traditional calibration methods are mostly based on parametric models and involve iterative optimization calculations, making it difficult to effectively correct full-field distortion and achieve autonomous on-orbit calibration. Therefore, we developed a full-field numerical on-orbit autonomous calibration method. During the on-orbit stable operation, the satellite drives star trackers to scan and image the star map, while the star trackers continuously accumulate residuals between the measured and theoretical star positions. When stars cover the entire field of view, the refined grid-based numerical calibration model of the distortion residuals is established. Subsequently, the precise correction of the full-field distortion is performed via bilinear interpolation. The proposed method has been validated in SuperView Neo1-03. The mean distortion residuals after calibration are reduced to approximately 0.07 pixels. The attitude determination accuracy can achieve 0.321″(1σ). The method enabled the satellite to become China's commercial optical remote sensing satellite with the highest geolocation accuracy.