Configuration optimization of photogrammetry system based on spectral radius for on-orbit measurement

Non-contact optical measurement is a potential approach to on-orbit vibration measurement for flexible appendages, providing dynamic information for spacecraft control system. Binocular photogrammetry system is a practical configuration to achieve this measurement. In this paper, optimization approach and strategy for configuration parameters of this system are raised. Measurement matrix is specially defined to obtain the objective function for the optimization. Successive linear programming algorithm is used for optimization iteration. Transient responses of flexible appendages calculated by finite element model and corresponding images generated by OpenGL help to achieve this simulation-based optimization. The feasibility and effectiveness of the optimization are verified both by numerical study and experiment. Error analysis of the optimal system reveals great improvement in accuracy and robustness after optimization. This optimization is a promising approach to designing the configuration of binocular photogrammetry system and helping to achieve reliable on-orbit dynamic measurement results.

A Submillimeter-Level Relative Navigation Technology for Spacecraft Formation Flying in Highly Elliptical Orbit

Spacecraft formation flying (SFF) in highly elliptical orbit (HEO) has attracted a great deal of attention in many space exploration applications, while precise guidance, navigation, and control (GNC) technology—especially precise ranging—are the basis of success for such SFF missions. In this paper, we introduce a novel K-band microwave ranging (MWR) equipment for the on-orbit verification of submillimeter-level precise ranging technology in future HEO SFF missions. The ranging technique is a synchronous dual one-way ranging (DOWR) microwave phase accumulation system, which achieved a ranging accuracy of tens of microns in the laboratory environment. The detailed design and development process of the MWR equipment are provided, ranging error sources are analyzed, and relative orbit dynamic models for HEO formation scenes are given with real perturbations considered. Moreover, an adaptive Kalman filter algorithm is introduced for SFF relative navigation design, incorporating process noise uncertainty. The performance of SFF relative navigation while using MWR is tested in a hardware-in-the-loop (HIL) simulation system within a high-precision six degrees of freedom (6-DOF) moving platform. The final range estimation errors from MWR using the adaptive filter were less than 35 μm and 8.5 μm/s for range rate, demonstrating the promising accuracy for future HEO formation mission applications.

An On-Orbit Dynamic Calibration Method for an MHD Micro-Angular Vibration Sensor Using a Laser Interferometer

The magnetohydrodynamic (MHD) micro-angular vibration sensor is a significant component of the MHD Inertial Reference Unit (MIRU) and measures micro-amplitude and wide frequency angular vibration. The MHD micro-angular vibration sensor must be calibrated in orbit since the ground calibration parameters may change after lift-off. An on-orbit dynamic calibration method for the MHD micro-angular vibration sensor is proposed to calibrate the complex sensitivity of the sensor in high frequency. An absolute calibration method that combines a homodyne laser interferometer and an angular retroreflector was developed. The sinusoidal approximation method was applied, and the calibration system was established and tested using a manufactured MHD sensor. Furthermore, the measurement principle and installation errors were analyzed, including the eccentric installation error of the retroreflector, the tilt installation error of the retroreflector, and the optical path tilt error. This method can be realized within a rotation range of ± 3 ∘ and effectively avoid the installation error caused by mechanical errors. The results indicate that the calibratable angular vibration frequency range is 25–800 Hz, and the angular velocity range is 0 . 076 –7590 mrad/s. The expanded uncertainties of the sensitivity amplitude and phase shift of the calibration system for the MHD micro-angular sensor are 0 . 04 % and 1 . 2 ∘ ( k = 2 ) .

Cycle Slip Detection and Repair for Dual-Frequency LEO Satellite GPS Carrier Phase Observations with Orbit Dynamic Model Information

Cycle slip detection and repair are crucial for precise GPS-derived orbit determination of the low-Earth orbit (LEO) satellites. We present a new approach to detect and repair cycle slips for dual-frequency LEO satellite GPS observations. According to Newton’s equation of motion, the second-order time difference of the LEO satellite’s position (STP) is only related to the sampling interval and the satellite’s acceleration, which can be precisely obtained from the known orbit dynamic models. Then, several kinds of second-order time-difference geometry-free (STG) phase combinations, taking full advantage of the correlation between the satellite orbit variations and the dynamic model, with different level of ionospheric residuals, are proposed and adopted together to detect and fix cycle slips. The STG approach is tested with some LEO satellite GPS datasets. Results show that it is an effective cycle slip detection and repair method for LEO satellite GPS observations. This method also has some important features. Firstly, the STG combination is almost independent of the pseudorange. Secondly, this method is effective for LEO satellites, even in real-time application. Thirdly, this method is suitable for ground-based GPS receivers if we know the acceleration of the receivers.

Circular Orbit Target Capture Using Space Tether-Net System

The space tether-net system for on-orbit capture is proposed in this paper. In order to research the dynamic behaviors during system deployment, both free and nonfree deployment dynamics in circular orbit are developed; the system motion with respect to Local Vertical and Local Horizontal frame is also researched with analysis and simulation. The results show that in the case of free deployment, the capture net follows curve trajectories due to the relative orbit dynamic perturbation, and the initial deployment velocities are planned by state transformation equations for static and floating target captures; in the case of non-free deployment, the system undergoes an altitude libration along the Local Vertical, and the analytical solutions that describe the attitude libration are obtained by using variable separation and integration. Finally, the dynamics of postdeployment system is also proved marginally stable if the critical initial conditions are satisfied.

Analysis of Filtering Methods for Satellite Autonomous Orbit Determination Using Celestial and Geomagnetic Measurement

Satellite autonomous orbit determination (OD) is a complex process using filtering method to integrate observation and orbit dynamic equations effectively and estimate the position and velocity of a satellite. Therefore, the filtering method plays an important role in autonomous orbit determination accuracy and time consumption. Extended Kalman filter (EKF), unscented Kalman filter (UKF), and unscented particle filter (UPF) are three widely used filtering methods in satellite autonomous OD, owing to the nonlinearity of satellite orbit dynamic model. The performance of the system based on these three methods is analyzed under different conditions. Simulations show that, under the same condition, the UPF provides the highest OD accuracy but requires the highest computation burden. Conclusions drawn by this study are useful in the design and analysis of autonomous orbit determination system of satellites.