Spacecraft Test Research Articles

Problems of irradiance characteristics measurement of solar simulators for ground spacecraft tests

The reliability of both spacecraft as a whole and of their systems is confirmed at the stage of complex ground-based experimental tests, including complex thermal vacuum tests. The thermal state of the test object in thermal vacuum chambers is obtaining, in particular, using a solar simulator. Radiometers based on silicon photoelectric converters are most often used to control the irradiance of a solar simulator under conditions of thermal vacuum tests. At the same time, an analysis of the features of silicon photoelectric converters shows that their direct measurement with the accuracy required for ground-based tests of spacecraft is impossible; their output is nonlinear, depends on the received spectrum, their own temperature and has long-term instability. The achieved measurement accuracy directly depends on the number and accuracy of the tools used and the methods of the necessary correction, of which the mismatch correction between the solar simulator spectrum and the solar spectrum is the most difficult and laborious. At the same time, spectrally nonselective heat flux radiometers are free from the above disadvantages. In the course of the experiment we carried out, the significant dependence of the accuracy of measuring the irradiance with radiometers based on silicon photoelectric converters on the received spectrum was confirmed. The conclusion is made that direct measurement by heat flux radiometers of the irradiance of the solar simulator is most justified under the conditions of thermal vacuum tests.

Reducing operational costs of thermal vacuum testing of spacecraft via gaseous nitrogen thermal conditioning technology

Many new thermal vacuum testing programs for ground testing of spacecraft require ensuring high accuracy temperature regime in a wide temperature range. Thermal vacuum tests are notable for significant material costs. Therefore, the requirement to reduce operating costs, including those associated with ensuring the temperature regime, is not less relevant. This explains the increased interest in promising energy-efficient technologies, one of which is based on the thermal conditioning of gaseous nitrogen. Systems with gaseous nitrogen thermal conditioning units have an optimal combination of operational and technical characteristics and, compared to systems where liquid nitrogen is poured into cryogenic screens, have lower consumption of liquid nitrogen and electrical energy, especially in stabilized temperature regime. The risk of contamination of the thermal vacuum chamber and the test object due to leaks of the liquid coolant is eliminated. Due to the fact that the properties of nitrogen quite accurately correspond to the ideal gas law, modeling of such systems is relatively simple, and the characteristics are predictable and stable. The article provides a brief analysis of the characteristics of gaseous nitrogen thermal conditioning units of two leading foreign manufacturers and the results of the practical application of four foreign manufactured thermal conditioning units with different characteristics in a typical thermal vacuum chamber. We considered the main directions of improving the characteristics of thermal conditioning units by foreign manufacturers. The conclusion is made about the high efficiency and economic feasibility of gaseous nitrogen thermal conditioning technology in most cases of thermal vacuum testing.

A Method of On-line Monitoring for Vibration Table Bearings Based on VMD

Aiming at the problems that the bearing inside the sliding table of the shaker used for the dynamic test of spacecraft cannot be observed and the failure cannot be known at the initial stage, an online prediction method for bearing failure is proposed. In this paper, the acceleration sensor is selected as the monitoring medium of bearing motion state response, and the VMD (variational mode decomposition) is used as the analysis method of bearing acceleration response data to calculate the harmonic components of the bearing except the fundamental wave. Through the calculation results, the failure bearing can be intuitively interpreted.

Simulation design method of free boundary simulator for high precision spacecraft on orbit

The reproduction of on-orbit free boundary is one of the key technologies for highly accurate ground micro-vibration test of high precision optical spacecraft. This paper focuses on the simulation design method of the free boundary simulator based on finite element method (FEM). The preliminary design is modeled by one-dimensional spring elements, which is effective to optimize the critical design parameters. Then the detailed design model is established to verify the capability of strength, the stability and the modal performance of the free boundary simulator. The actual simulator is manufactured according to the simulation design. And the test of the actual simulator indicates that, the simulation results match well with the experimental results. The development of the free boundary simulator of spacecraft can be instructed effectively by the simulation method in this paper.

The research on Power Supply Array Intelligent Management Technology for Spacecraft Thermal Test

The thermal test of spacecraft has a large demand for the program-controlled power supply, which was configured as array. In this paper, the intelligent management technology of program-controlled power supply is researched. Base on the analysis of the history fault type of power supply, the fault detection technology of power supply is studied. Then, combined with the technology of power supply redundancy switching, an on-line switching device is designed. Through the verification experimental, the experimental results show that the system can quickly realize the detection and positioning of the fault power supply, and can finish the online switching of the fault power supply to the backup power within the second-level time. The research of intelligent management technology enhances the management efficiency of the large scale power supply array, and improves the operational reliability of the spacecraft thermal test.

Research on risk control method of Spacecraft AIT process based on PFTA

In this article, the Process Fault Tree Analysis (PFTA) method is researched, which is about to the risk management of spacecraft Assembly Integration and Test (AIT) process. The method of how to identify the top event and bottom event of Spacecraft AIT process risk and the method of how to assess the risk severity of the bottom event is introduced. The model of risk control matrix is established. From the responsibilities, tools, methods, monitor and other dimensions about the post roles involved of the AIT process, how to establish a risk management system based on the identification, assessment, analysis and control of the whole AIT process is researched. In this risk management system, through technology subject, quantitative topic, process improve, Quality Control (QC) subjects, implementation of product assurance elements, writing Standard Operating procedure (SOP), maintaining system documents, combing knowledge and operation taboo items and other method is used.

Experimental Study of Spacecraft Pose Estimation Algorithm Using Vision-based Sensor

This paper presents a vision-based relative pose estimation algorithm and its validation through both numerical and hardware experiments. The algorithm and the hardware system were simultaneously designed considering actual experimental conditions. Two estimation techniques were utilized to estimate relative pose; one was a nonlinear least square method for initial estimation, and the other was an extended Kalman Filter for subsequent on-line estimation. A measurement model of the vision sensor and equations of motion including nonlinear perturbations were utilized in the estimation process. Numerical simulations were performed and analyzed for both the autonomous docking and formation flying scenarios. A configuration of LED-based beacons was designed to avoid measurement singularity, and its structural information was implemented in the estimation algorithm. The proposed algorithm was verified again in the experimental environment by using the Autonomous Spacecraft Test Environment for Rendezvous In proXimity (ASTERIX) facility. Additionally, a laser distance meter was added to the estimation algorithm to improve the relative position estimation accuracy. Throughout this study, the performance required for autonomous docking could be presented by confirming the change in estimation accuracy with respect to the level of measurement error. In addition, hardware experiments confirmed the effectiveness of the suggested algorithm and its applicability to actual tasks in the real world.

Modeling and dynamic environment analysis technology for spacecraft

Spacecraft sustains complex and severe vibrations and acoustic environments during flight. Predicting the resulting structures, including numerical predictions of fluctuating pressure, updating models and random vibration and acoustic analysis, plays an important role during the design, manufacture and ground testing of spacecraft. In this paper, Monotony Integrative Large Eddy Simulation (MILES) is introduced to predict the fluctuating pressure of the fairing. The exact flow structures of the fairing wall surface under different Mach numbers are obtained, then a spacecraft model is constructed using the finite element method (FEM). According to the modal test data, the model is updated by the penalty method. On this basis, the random vibration and acoustic responses of the fairing and satellite are analyzed by different methods. The simulated results agree well with the experimental ones, which shows the validity of the modeling and dynamic environment analysis technology. This information can better support test planning, defining test conditions and designing optimal structures.

An Evaluation Strategy of Spacecraft Test Case Adequacy Based on Mutation Testing

As typical safety-critical system, the trustworthiness of spacecraft has become a widespread concern. The evaluation of trustworthiness depends on the execution of spacecraft test cases, of which the adequacy is of great importance for the spacecraft to conduct effective assessment of trustworthiness. This paper focuses on the evaluation of the adequacy of spacecraft test cases based on mutation testing technique. Mutation testing theory is extended to spacecraft testing, and mapping between spacecraft faults and mutation operators is constructed. A virtual spacecraft testing platform is developed, on which the spacecraft fault injection strategy is given and test cases generated by IPOG algorithms are evaluated by adequacy, verifying the effectiveness of the proposed strategy.

SPIRET: An Innovative Technique for Random Vibration Testing Of Large Spacecraft

Abstract System Point Input Random Excitation Testing (SPIRET) was developed as an alternative to both system level acoustics and base-shake random vibration testing of large spacecraft. The goal of SPIRET was to obtain an enhanced workmanship test of the spacecraft, prior to launch, by inducing a higher, more uniform dynamic acceleration response throughout the integrated system. The underlying SPIRET concept is to utilize the spacecraft modal characteristics to amplify the shaker input force and produce a high acceleration response throughout the flexible structure. SPIRET utilized commercial off-the-shelf vibration equipment coupled with satellite specific Mechanical Aerospace Ground Equipment (MAGE). Random vibration control was achieved using inline load cells and a Force Spectral Density (FSD) input spectrum which effectively provided both feedback control of the shaker and force limiting during the vibration test. SPIRET effectiveness was verified using a hi-fidelity spacecraft simulator which was previously used for structural and acoustic testing. This enabled direct comparison of SPIRET response accelerations to acoustic response accelerations at common spacecraft locations. In general, SPIRET produced higher dynamic loading throughout the spacecraft than did acoustic testing at Protoqual (PQ) levels over the tested frequency range of 5Hz to 500 Hz. This resulted in a more thorough workmanship screen of the spacecraft prior to launch. The benefits of SPIRET extend beyond the technical goal of achieving an enhanced system workmanship test. Significant schedule and cost savings were realized since the test was conducted within the spacecraft final assembly facility which enabled parallel vehicle processing activities and shared personnel resources. SPIRET has been successfully used as the final integrated spacecraft level dynamic test at Lockheed Martin Denver since 2001.

The Simulation of Molecular Return Flux in Thermal Vacuum Test of Spacecraft

In process of thermal vacuum test of spacecraft, the molecular contamination can have severe effects on performance and reliability of optical payload. In this article, we analyzed the contamination transport mechanism, simplified boundary conditions and input parameters based on physical understanding. We employed the Direct Simulation Monte-Carlo method to simulate the return flux of molecular contamination scattered by residual gas molecules in thermal vacuum tests of solar array and whole satellite. The results of simulation show that the return flux cannot be ignored, and its highest value would be 0.004. This would help the contamination control of spacecraft design, manufacture, test, and on-orbit operation.

Cooperative Relative Navigation for Space Rendezvous and Proximity Operations using Controlled Active Vision

This work aims to solve the problem of relative navigation for space rendezvous and proximity operations using a monocular camera in a numerically efficient manner. It is assumed that the target spacecraft has a special pattern to aid the task of relative pose estimation, and that the chaser spacecraft uses a monocular camera as the primary visual sensor. In this sense, the problem falls under the category of cooperative relative navigation in orbit. While existing systems for cooperative localization with fiducial markers allow full six‐degrees‐of‐freedom pose estimation, the majority of them are not suitable for in‐space cooperative navigation (especially when involving a small‐size chaser spacecraft), due to their computational cost. Moreover, most existing fiducial‐based localization methods are designed for ground‐based applications with limited range (e.g., ground robotics, augmented reality), and their performance deteriorates under large‐scale changes, such as those encountered in space applications. Using an adaptive visual algorithm, we propose an accurate and numerically efficient approach for real‐time vision‐based relative navigation, especially designed for space robotics applications. The proposed method achieves low computational cost and high accuracy and robustness via the following innovations: first, an adaptive visual pattern detection scheme based on the estimated relative pose is proposed, which improves both the efficiency of detection and the accuracy of pose estimates; second, a parametric blob detector called Box‐LoG is used, which is computationally efficient; and third, a fast and robust algorithm is introduced, which jointly solves the data association and pose estimation problems. In addition to having an accuracy comparable to state‐of‐the‐art cooperative localization algorithms, our method demonstrates a significant improvement in speed and robustness for scenarios with large range changes. A vision‐based closed‐loop experiment using the Autonomous Spacecraft Testing of Robotic Operations in Space (ASTROS) testbed demonstrates the performance benefits of the proposed approach.

A New Feature Points Reconstruction Method in Spacecraft Vision Navigation

The important applications of monocular vision navigation in aerospace are spacecraft ground calibration tests and spacecraft relative navigation. Regardless of the attitude calibration for ground turntable or the relative navigation between two spacecraft, it usually requires four noncollinear feature points to achieve attitude estimation. In this paper, a vision navigation system based on the least feature points is designed to deal with fault or unidentifiable feature points. An iterative algorithm based on the feature point reconstruction is proposed for the system. Simulation results show that the attitude calculation of the designed vision navigation system could converge quickly, which improves the robustness of the vision navigation of spacecraft.

1P2-V05 群ロボットを用いた宇宙用展開構造物の下方支持型地上試験装置の開発

The prototype tests of spacecraft which have deployable structures are one of the important stage. When performing the prototype tests, spacecraft require space environment. However, the effect of gravity interferes with every structure on the earth, but in space the effect of gravity is ineffective. State of zero gravity is required to do the prototype test of spacecraft. In this study, we propose a prototype test system for variable flexible spacecraft by using multi mobile robots with decentralized autonomous control system. The main purpose of this system is to create a state of zero gravity as well as possible. All the robot is autonomously controlled by using force control. All the robot provide force in opposite direction to gravity. The validity of the system is verified by the simple hardware model.

SSETO—Small Satellite for Exoplanetary Transit Observation

SSETO is the result of a phase-A study in context of the small satellite program of the University of Stuttgart that demonstrates the capability of a university institute to build a small satellite with a budget of 5million Euro. The satellite will be capable of observing exoplanets in a Neptune–Earth scale and obtaining data of interstellar dust. Due to a system failure of NASA׳s Kepler mission, there is currently (October 2013) a lack of satellites searching for exoplanets. This paper details the design of subsystems and payload, as well as the required test tasks in accordance with the mission profile at a conceptional level. The costs for standard spacecraft testing and integration tasks are included, but not those of launch, ground support, operations and engineer working hours.

Research on the Testbed Framework of Spacecraft

Aiming at the characters and requirements of spacecraft design, simulation and test, The test-bed framework was studied in this paper. The framework architecture employ the Data Distribute Service (DDS) to provide communications abstractions and reduce software interface complexity. The time management strategy was studied to keep synchronic of all components. The CAN bus interface was designed to integrate the CAN bus components. The framework will allow rapid-prototyping of high-fidelity simulations of spacecraft during their early project phases, and help reduce the effort, time and expanse to evaluate the performance.

Development of multi-degree-of-freedom microvibration emulator for efficient jitter test of spacecraft

A number of components and payload systems installed in satellites are found to be exposed to various disturbance sources, such as the reaction wheel assembly, the control moment gyro, coolers, and others. Low damping in space causes continuous microvibration that degrades the performance of various payload systems; this is customarily called jitter problem in spacecraft community. Various isolation systems have been developed to improve the performance of the optical payloads under the microvibration environments. During the spacecraft development process, an experimental validation of jitter effects (either controlled or not) on the performance of optical payloads using all the flight model components is not often conducted due to the scheduling issue or the product assurance activities. The disturbance characteristics of a prototype or an engineering model of the disturbance source such as reaction wheel assembly are significantly different from their flight model counterparts. Therefore, in order to facilitate jitter test as well as the performance evaluations of an isolator during the satellite development process, this article proposes a microvibration emulator that generates the real disturbance spectrums of flight models. The development procedure for the reaction wheel assembly emulator is described. Prototype single-axis and three-axis microvibration emulators are demonstrated, and the performances are evaluated by means of disturbance characteristics similar to those of the reaction wheel assembly.

3C14 Development of a gravity compensation system for the prototype test of spacecraft by using mobile type multi robots(The 12th International Conference on Motion and Vibration Control)

In this study, we propose a prototype test system for variable flexible spacecraft by using multi mobile robots. The system is designed for gravity compensation of the prototype model of spacecraft which has deployable membrance structures or flexible structures. The system is composed of multi robots. The robot is controlled by the force control to support the structures as well as the decentralized autonomous control. The validity of the proposed system is verified by hardware experiments.

Study on Real-time Task Scheduling Policy for Automated Testing of Spacecraft

Spacecraft testing is an important phase of developing a spacecraft. As the test task requests in spacecraft testing have dynamic, real-time and resource constraints characteristics, it need further research on requests scheduling policy. Based on the EDF scheduling model, this study apprehends the dynamic, real timing and communicating resource limitation in automated testing of application-level device gateway in spacecraft subsystem in its design of a multiple-factor based PRI ascertain method and put forward a scheduling policy of multithreading under resource limitation. Test results show that this policy better assures scheduling effect with effectivescheduling of each parallel testing task under different task densities.

The study of spacecraft parallel testing

For the purpose of avoiding interference between each parallel testing tasks in a spacecraft, this paper analyzes the testing process by dividing it into testing atoms, and makes the parameter set as the basic unit for each testing atom resource allocation so as to avoid interference. By means of modeling the parallel testing and with the object of minimizing the total testing time, it puts forward the parallel spacecraft testing task scheduling algorithm on basis of improved particle swarm optimization. The experimental results verify that this method can be efficiently applied in spacecraft parallel testing optimal scheduling.