The rapid development of open source software has gradually changed the pattern of software development in the world. As a leader in the field of space exploration, NASA released the 2017-2018 software catalog in March 2017, and opened a series of space related projects, including design simulation tools, application software and code base used for many years, most of which can be used free of charge, such as CCSDS CFDP file transfer protocol, a standard tool for exchanging large files with spacecraft. In the past, the research focused on the policy and mechanism of the transformation of NASA's technological achievements. From the technical point of view, this paper studies the open-source software of NASA, secondary development practice, and considers the development of open-source technology for software definition satellite technology, which has certain reference significance for solving the problem of satellite intelligence.
One
1.1 technology transfer plan
Since 1964, NASA, which has been leading the world with cutting-edge science and technology, has established a long-term mechanism for space technology to serve the people's livelihood through the establishment of technology transfer plan, and published a spinoff report every year. So far, more than 2000 technologies have been successfully transferred to civilian areas. While fulfilling the motto of "we strive to move to a new height and discover the unknown for human well-being", NASA's technology transfer program has enabled many small and medium-sized enterprises to use NASA's scientific research achievements for entrepreneurship, and new fields have been widely used. The technology transfer program set up by NASA in the space field has become a high-tech achievements transformation mechanism with good operation and outstanding benefits, accelerating the transformation of scientific and technological achievements.
1.21.2 progress and purpose of open source
As part of the technology transfer plan, NASA has released a large number of open-source software and tools for space projects on its official website. At present, there are 1072 available program software, covering 15 aspects such as project management, data and image processing, power system, spacecraft design and integration tools, and autonomous system, as shown in Figure 1. These codes are from 11 R & D centers and institutions such as NASA Ames, JPL, Jonhson and Armstrong. NASA's approach has two purposes. On the one hand, it hopes to improve code quality, accelerate development, and gain more suggestions for project improvement through open source community peer review. On the other hand, it aims to maximize the visibility and impact of NASA research, and transfer technology to enterprises and individuals for the development of the latest technology in new fields.
Figure 1 Software catalog classification
Fig.1 NASA Open Source Software Category
Two
2.1Livingstone2（L2）
Livingstone 2 [2-3], developed by NASA Ames center, is a model-based fault diagnosis and recovery engine. It aims to make complex systems, such as spacecraft, continuously autonomously and intelligently realize the self perception, diagnosis and response to abnormal state of system state, especially in the face of hardware failure or unknown events, with the least human intervention.
Through the establishment of a set of multi-level qualitative logic models, through the comparison of model prediction data and sensor measured data to detect and diagnose system faults, to achieve the tracking system status, and according to the different status of the proposed instructions to achieve continued operation of the system, the principle is shown in Figure 2. L2 has been implemented and applied in several test beds, including the X34 propulsion system and the international space station. At the same time, it has also carried out flight tests on the earth observation satellite 1 (EO-1).
Figure 2 L2 diagnosis principle
Fig.2 NASA L2 Diagnosis Principle
2.2trick spacecraft simulation environment
The trick spacecraft simulation environment [4] is developed by NASA Johnson Space Center, which enables users to establish simulation applications for various stages of spacecraft development, including early design, performance index evaluation, flight software development and testing, dynamic analysis of flight process, closed-loop testing of software and hardware. The purpose is to provide a common simulation capability, so that experts in various fields can focus on the model in specific fields, rather than the application of simulation functions such as task sequencing, data storage, etc. But the software is only available to US citizens. Figure 3 shows the advanced simulation function flow of trick Monte Carlo, which allows users to repeatedly simulate and continuously optimize different inputs.
Figure 3 Monte Carlo function flow of trick
Fig.3 Trick Monte Carlo Advanced Simulation Capability Flow
2.3Open MCT[5]
Open MCT (open mission control technologies) is the next generation of mission control framework with data visualization, which can be used on the desktop and mobile end respectively. It is developed by NASA Ames center and used for spacecraft mission analysis, operation control and planning. As a general and open basic platform, users can carry out secondary development on the basis of open MCT, and develop mission planning, control, data analysis and other applications for different spacecraft. See Figure 4 for the system effect diagram.
Figure 4 open MCT system effect
Fig.4 Open MCT General View
Three
3.1 system introduction
The system is used to monitor the health status of satellite platform, including but not limited to CPU temperature, GPU temperature, CPU utilization, RAM utilization, Rom utilization, attitude measurement parameters (such as acceleration sensor XYZ, magnetometer XYZ, etc.) and other information, and the health status information (soh: state of Health) is packaged in CCSDS packet format and sent to the ground station system through the radio frequency link to display information in chart form.
3.2 system architecture
The system uses raspberry PI + PC to build the verification prototype system, RPI as the satellite terminal, runs Linux system and flight control system software, application software SOH, PC as the ground terminal, runs Linux system and ground station software, and connects through WiFi wireless link. After the system runs, it can perform telemetry and remote control function. The system architecture is as follows:
Figure 5 system architecture
Fig.5 System architecture
3.3 system achievements
The system integrates the technical advantages of open source software, and makes customized improvement based on the requirements. After three months of testing, the software works normally, the system runs stably, and the simple health monitoring function is realized. In the next step, more components can be integrated through the bus to develop corresponding functional software, which is rich and perfect. Ground system operation diagram, see Figure 6
Figure 6 ground system operation diagram
Fig.6 Ground System View
Four
4.1 thinking about open source software in aerospace field
In the field of aerospace software, NASA has developed various application software, code base and tools from spacecraft simulation, design tools, onboard software, ground mission control, structural material design tools, etc. The motivation of open source on the official website is to hope that the use of peers in the open source community can improve the quality of software. To some extent, the use of these codes, especially the secondary development, will make enterprises with weak technical strength rely on NASA's basic level codes and affect their ability of independent innovation.
The importance of space software to space assets is self-evident, especially the basic core software. In terms of operating system, VxWorks is still the mainstream choice of most domestic aerospace projects. It is worth thinking about the open source research of operating system. On the other hand, the common system of artificial intelligence technology is Linux. Many machine learning algorithms are developed based on Linux. The development of satellite intelligence is to choose the open-source route, to gather intelligence, or to absorb mature intelligence algorithms in traditional fields. This is also a research direction worthy of discussion.
4.2 open source will be an important technology driver for commercial aerospace enterprises
Open source software has the characteristics of openness, sharing, freedom and so on. Enterprises can avoid building wheels repeatedly. With the least human, material and financial resources, they can quickly build a system. Based on the open source software, it can be customized flexibly. Through the power of the community, the software is more stable and more secure, and security vulnerabilities can be found and repaired in time. Android is a very successful example After being released in the form of open source in 2007, the camp showed explosive growth and became the mobile operating system with the largest share [6].
The pursuit of more stability, security and reliability makes the cost of aerospace software development and testing higher. Due to the pursuit of high reliability and great responsibility, the development of software has been slower than the development of Internet software industry. The development of commercial aerospace, combined with open source technology, is expected to change this situation in terms of software quality and cost.
Some codes of NASA's open source project software are updated iteratively every day, which improves the quality of the software and further reduces the risk of application in aerospace projects, which is of great significance for the development of software definition satellite technology.
References
[1] NASA Open Source Software［EB/OL］http://code.nasa.gov.
[2] LivingStone2［EB/OL］https://github.com/nasa.
[3] Chen Zhizuo, Liu xingzhao, LV Gaohuan. Livingstone for spacecraft propulsion system fault diagnosis [J]. Journal of Terahertz Science and electronic information, 2013, 11 (5): 770-774
CHEN Zhi-zuo，LIU Xing-zhao，LV Gao-huan. Fault diagnosis of spacecraft propulsion system by using Livingstone [J]. Journal of Terahertz Science and Electronic Information Technology，2013，11（5）：770-774.
[4] Trick [EB/OL] https://www.nasa.gov/centers/ames/research.
[5] Open MCT [EB/OL] https://github.com/nasa/openmct.
[6] https://www.idc.com/promo/smartphone-market-share
This paper is reprinted from the 2018 software definition satellite Summit Forum, the original title of NASA open source software practice and thinking
》By Kang Hailong, fan Yanan and Li Bin
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