Flight Software Development Research Articles

Research on Optimization and Performance Improvement of UAV Embedded Flight Control System Based On C Language

With the rapid development of electronic information technology, the performance of embedded microcontroller is constantly improved, and the software of UAV flight control system is also developing in the direction of multi-function and multi-task. Traditional flight control software is usually written in C language, resulting in its scalability and modular design is limited. In view of the relatively consistent core content of the flight control system software, object-oriented thought and component technology are introduced to carry out modular design and implementation of the core part, improve the scalability and flexibility of the system, and facilitate the rapid addition of new functions. Based on the analysis of the shortcomings of the existing flight control software design, this paper proposes to use C++ language to componentize the driver code, design each submodule in the form of classes, and build the overall software framework according to the dependence relationship of the software level. Through component technology, the design and implementation of the driving component are completed, and the design principle of the driving component is discussed, and the implementation process of the component is explained in detail through the concrete code, and the derivation relationship between the components is analyzed. The subscription-release communication mechanism based on component relationship is designed, the communication interface between modules is standardized, and the independence of each module of flight control software is improved. Based on the driver component, the design and implementation of each task thread are completed, the data interaction and synchronization relationship between the task threads are discussed in detail, and the implementation details and execution process of the task thread are analyzed in combination with specific components. The relationship between the driver component and the task is sorted out, the integration of flight control software is completed, and the expansibility of the driver component and the independence of the task thread are analyzed. Through functional tests, including mission execution efficiency, cycle delay, and the effectiveness of the inertial navigation module, and test flights on the quadrotor platform, the results show that the optimized flight control software has significantly improved in performance and stability. The research and optimization in this paper not only enhance the scalability and modularization design of UAV flight control system, but also provide a valuable reference for the development of flight control software in the future.

Design, development and testing of flight software for EIRSAT-1: a university-class CubeSat enabling astronomical research

The capabilities of CubeSats have grown significantly since the first of these small satellites was launched in the early 2000s. These capabilities enable a wide range of mission profiles, with CubeSats emerging as viable platforms for certain space-based astronomical research applications. The Educational Irish Research Satellite (EIRSAT-1) is a CubeSat being developed as part of the European Space Agency’s Fly Your Satellite! program. In addition to its educational aims, the mission is driven by several scientific and technological goals, including goals related to a novel gamma-ray instrument for the detection of bright transient astrophysical sources, such as gamma-ray bursts. This work provides a detailed description of the software development life-cycle for EIRSAT-1, addressing the design, development and testing of robust flight software, aspects of payload interfacing, and risk mitigation. The described design-to-testing approach was implemented to establish, prior to launch, that EIRSAT-1 can perform its intended mission. Constraints and challenges typically experienced by CubeSat teams, which can impact the likelihood of mission success, are considered throughout this work, and lessons learned are discussed. The aim of this work is to highlight the advanced capabilities of CubeSats while providing a useful resource for teams implementing their own flight software.

Bench satellite development and testing

This paper discusses the development of a satellite-like system to bridge the gap between satellite development and satellite flight missions. The solution takes the form of a bench satellite, BenchSat, that can emulate satellite capabilities and interactions in a controlled environment on the ground. BenchSat utilises surrounding facilities, particularly an air bearing facility and an existing ground station, to produce a realistic test environment for satellite development. The air bearing facility entails a cart with pressurised gas which pushes the cart on a flat surface, creating a low-friction, space like environment. BenchSat comprises an electrical power subsystem, a radio communication subsystem, and an onboard computer subsystem. These systems are created to be a good representation of equivalent flight models and can serve as an initial step in the future development of each of these subsystems. A final experiment was conducted using an integrated BenchSat connected to an air bearing carrier cart. The ground station was used to give commands to the BenchSat to use its thrusters to translate and rotate the carrier cart. This creates a realistic interface to perform satellite rendezvous experiments. It is further extended to interface with a satellite simulator for Hardware-In-Loop testing and flight software development.

Flight Software Development for a CubeSat Application

This article presents a development of a CubeSat mission software running on an STM32-based on-board computer (OBC). This was conducted under the Canadian CubeSat Project, initiated by the Canadian Space Agency in 2018 to support the development of 15 CubeSats across Canada. The proposed mission software has a multilayered architecture and is divided into five layers from a low layer dedicated to the peripherals to the top layer dedicated to the Mission Applications. The CubeSat protocol (CSP) is used at the communication layer for easing connectivity between subsystems and to communicate with the ground segment. The mission software running on the OBC is built to meet many requirements defined for this satellite, such as version control, classifications, margins, etc. The CubeSat will be able to accomplish two scientific missions related to the study of space weather once the satellite is put into orbit from the International Space Station. An overview of the software running on the OBC is presented, written in C Language, and includes the implementation of the CSP. FreeRTOS used as an operating system for the OBC is also presented. A Command Line Interface was designed for testing purposes to ensure software efficiency and some results are discussed in this article. The flight software consists of three main tasks and subtasks. Of the 1024 kB of flash memory, only 240 kB was used which represents less than 20% of the total memory. The CPU load is 34% for normal, manual, and maintenance modes and 16% for failure modes.

Advanced Statistical Methods in Spacecraft Flight Software Cost Estimation: Bayesian Regression and Nonlinear Principal Components Analysis to Support System Engineering in the Early Project Lifecycle

AbstractThis paper provides an overview of the new features and model updates in the upcoming release of the NASA Analogy Software Cost Tool (ASCoT). ASCoT, hosted within the Online NASA Space Estimation Tools (ONSET) on the One NASA Cost Engineering (ONCE) Database, is a web‐based tool that provides a suite of estimation tools to support early lifecycle NASA flight software cost analysis. In addition to the traditional parametric flight software costing method CO‐COMO II, ASCoT contains a Bayesian linear regression to predict total flight software development cost as a function of total spacecraft cost, as well as four analogic methods: k‐Nearest Neighbors (kNN) and Clustering models to predict Effort (in work‐months) and total source lines of code (SLOC). These methods are designed to work primarily with system‐level inputs such as mission type (orbiter, lander, etc.), mission destination (Earth, Inner Planetary, etc.), and the number of instruments and deployables. Nonlinear principal components analysis (NLPCA) is performed to find the principal features of the data composed of both categorical and numerical variables and is necessary prior to defining our analogic methods. Sensitivity analyses and in‐ and out‐of‐sample model performance results are presented for the Bayesian CER and the analogic models.

Flight Software Development, Migration, and Testing in Desktop and Embedded Environments

This paper investigates different strategies for end-to-end flight software development that support having both desktop and embedded environments while minimizing the existing gap between them, in order to facilitate reiteration back and forth of the flight application. For desktop prototyping, the use of Python as a user-facing language wrapping C/C++ algorithm source code is considered. The Basilisk software testbed is presented as a specific incarnation of this desktop development proposal. For embedded development and testing, two different approaches are reviewed and demonstrated: the use of NASA’s core Flight System, which is a well-known middleware layer, and the use of MicroPython, which is a new, lean, and efficient implementation of the Python 3 programming language optimized to run on constrained environments. The migration flow of flight algorithms from the Basilisk desktop environment into each of the considered embeddable targets is described and numerical results from embedded testing are shown. While the Basilisk–core Flight System strategy is explained through the experience of its use in an actual mission, the Basilisk-MicroPython strategy is proposed as a promising and novel strategy that is still under investigation.

A Highly Modular Software Framework for Reducing Software Development Time of Nanosatellites

The standardization of the physical aspects of nanosatellites (also known as CubeSats) and their wide adoption in academia and industry has made the mass production and availability of off-the-shelf components possible. While this has led to a significant reduction in satellite development time, the fact remains that a considerable amount of mission development time and effort continues to be spent on flight software development. The CubeSat’s agile development environment makes it challenging to utilize the advantages of existing software frameworks. Such an adoption is not straightforward due to the added complexity characterized by a steep learning curve. A well-designed flight software architecture mitigates possible sources of failure and increases mission success rate while maintaining moderate complexity. This paper presents a novel approach to a flight software framework developed specifically for nanosatellites. The software framework is characterized by simplicity, reliability, modularity, portability, and real-time capability. The main features of the proposed framework include providing a standardized and explicit skeleton for each module to simplify their construction, offering standardized interfaces for all modules to simplify communication, and providing a collection of ready-to-use common services open for further enhancement by CubeSat software developers. The framework efficiency was demonstrated through a software developed for the MeznSat mission that was successfully launched into Low Earth Orbit in September 2020. The proposed software framework proved to simplify software development for the application developer while significantly enhancing software modularity.

Reusable and Reliable Flight-Control Software for a Fail-Safe and Cost-Efficient Cubesat Mission: Design and Implementation

While there is no rigorous framework to develop nanosatellites flight software, this manuscript aimed to explore and establish processes to design a reliable and reusable flight software architecture for cost-efficient student Cubesat missions such as Masat-1. Masat-1 is a 1Unit CubeSat, developed using a systems engineering approach, off-the-shelf components and open-source software tools. It was our aim to use it as a test-bed platform and as an initial reference for Cubesat flight software development in Morocco. The command and data handling system chosen for Masat-1 is a system-on-module-embedded computer running freeRTOS. A real-time operating system was used in order to simplify the real-time onboard management. To ensure software design reliability, modularity, reusability and extensibility, our solution follows a layered service oriented architectural pattern, and it is based on a finite state machine in the application layer to execute the mission functionalities in a deterministic manner. Moreover, a client-server model was elected to ensure the inter-process communication and resources access while using uniform APIs to enhance cross-platform data exchange. A hierarchical fault tolerance architecture was also implemented after a systematic assessment of the Masat-1 mission risks using reliability block diagrams (RBDs) and functional failure mode, effect and criticality analysis (FMECA).

Applying analytical and empirical schedulability analysis techniques to a real spacecraft flight software

Software schedulability analysis is a crucial aspect for real-time software system verification. This paper presents a combined approach of analytical and empirical techniques for measuring task execution times and verifying the timing constraints of flight software (FSW) applications in real space projects. The proposed methodology is based on the following two main steps. Firstly, we perform an analytical verification via the response time analysis (RTA) in order to show that all the hard deadlines defined for time-critical SW tasks are met. In particular, the worst-case execution times (WCETs) of such SW tasks are measured via static code analysis. Secondly, we analyse the activities that are executed in the context of less time-critical tasks via a more empirical argumentation. The CPU load for the whole running FSW is measured in significant and time-consuming operational scenarios with the aim of proving that the CPU load requirements are fulfilled. Such approach has been applied to an industrial-sized spacecraft FSW and points out the importance of focusing on this topic in the early phases of the FSW development.

English

English

Software Reliability Analysis of NASA Space Flight Software: A Practical Experience.

In this paper, we present the software reliability analysis of the flight software of a recently launched space mission. For our analysis, we use the defect reports collected during the flight software development. We find that this software was developed in multiple releases, each release spanning across all software life-cycle phases. We also find that the software releases were developed and tested for four different hardware platforms, spanning from off-the-shelf or emulation hardware to actual flight hardware. For releases that exhibit reliability growth or decay, we fit Software Reliability Growth Models (SRGM); otherwise we fit a distribution function. We find that most releases exhibit reliability growth, with Log-Logistic (NHPP) and S-Shaped (NHPP) as the best-fit SRGMs. For the releases that experience reliability decay, we investigate the causes for the same. We find that such releases were the first software releases to be tested on a new hardware platform, and hence they encountered major hardware integration issues. Also such releases seem to have been developed under time pressure in order to start testing on the new hardware platform sooner. Such releases exhibit poor reliability growth, and hence exhibit high predicted failure rate. Other problems include hardware specification changes and delivery delays from vendors. Thus, our analysis provides critical insights and inputs to the management to improve the software development process. As NASA has moved towards a product line engineering for its flight software development, software for future space missions will be developed in a similar manner and hence the analysis results for this mission can be considered as a baseline for future flight software missions.

Gravity Probe B data system description

The Gravity Probe B data system, developed, integrated, and tested by Lockheed Missiles & Space Company, and later Lockheed Martin Corporation, included flight and ground command, control, and communications software. The development was greatly facilitated, conceptually and by the transfer of key personnel, through Lockheed’s earlier flight and ground test software development for the Hubble Space Telescope (HST). Key design challenges included the tight mission timeline (17 months, 9 days of on-orbit operation), the need to tune the system once on-orbit, and limited 2 Kbps real-time data rates and ground asset availability. The result was a completely integrated space vehicle and Stanford mission operations center, which successfully collected and archived 97% of the ‘guide star valid’ data to support the science analysis. Lessons learned and incorporated from the HST flight software development and on-orbit support experience, and Lockheed’s independent research and development effort, will be discussed.

Flight Control Software: Mistakes Made and Lessons Learned

Aerospace or flight control systems software development follows a rigorous process according to the RTCA DO-178B standard, yet software errors still occur. A review of the mistakes found during flight control test activities spanning 23 years reveals that the same mistakes tend to recur repeatedly. Moreover, we haven't yet learned everything about the mistakes that can be made in flight controls; new mistakes continue to pop up.

Google Earth를 이용한 비행정보 시각화 시스템의 구현

본 논문은 항공기의 비행정보를 효과적으로 시각화하기 위하여 Google Earth를 이용한 시스템 구현에 대해 기술한다. 이 시스템은 Google Earth 에서 제공하는 상세한 위성 영상 정보를 이용하기 위하여 COM API 를 이용하였다. 제안하는 시스템은 항공기의 다양한 장치에서 얻어진 비행정보를 OpenGL을 이용하여 각종 계기판에 표시하고 실제 비행모습을 가시화하기 위하여 Google Earth Map에 연동하여 표시하였다. 본 연구결과는 비행평가 및 개선에 이용될 수 있고 향후, 비행소프트웨어 개발에 적용될 수 있다. This paper presents implementation of a system for effective visualizing flight information of aircraft using Google Earth. This system in order to use a detailed satellite image which provide from Google Earth used COM API. This system appeared the various flight information of the aircraft in the instrument panel using OpenGL and the aircraft flight condition is visible in the Google Earth Map. This research result used to flight evaluation and improvement. In future will be able to apply to flight software development.

Experiences in Improving Flight Software Development Processes

In 2001, the Jet Propulsion Laboratory (JPL) initiated a software process improvement effort. In 2004, JPL began the Multimission System Architecture Platform (MSAP) project and designated it as part of this effort. In 2007, JPL's Engineering and Science Directorate, which controls the MSAP project's technical development, achieved CMMI Staged Maturity Level 3.1 This article describes the impacts of the CMMI rating and the JPL process improvement effort on the MSAP project's software engineering and assurance organizations.

Formal Validation of Realtime Middleware

Distributed terrestrial computer systems employ middleware software to provide communications abstractions and reduce software interface complexity. Embedded applications are adopting the same approaches, but must make provisions to ensure that hard real-time temporal performance can be maintained. This thesis presents the development and validation of a middleware system tailored to spacecraft flight software development. OurmiddlewarerunsontheGeneralizedFlightOperationsProcessingSimulator(GFLOPS) and is called the GFLOPS Rapid Real-time Development Environment (GRRDE). GRRDE provides publish-subscribe communication services between software components. These services help to reduce the complexity of managing software interfaces. The hard real-time performance of these services has been verified with General Timed Automata modelling demonstrating the usefulness of formal analysis techniques for flight software applications.

Developing safety critical software for an unmanned aerial vehicle situational awareness tool

In this paper, we describe our application of the SPARK programming language to the development of flight control software for an Unmanned Aerial Vehicle (UAV). The SPARK language was used during a senior-level software engineering course at the US Air Force Academy. This paper uses the year-long project from this course as an example application of SPARK. The process we used to build an interface between C++ and Ada is discussed along with our experiences with using SPARK.

Fast model updates and simulation for efficient flight control software design

The development, verification, and validation of flight control software for aircraft is characterized by high demands on accuracy, reliability and efficiency. Such processes cover all stages from first simulations to final flight test. The respective environment is described here on the basis of the experimental aircraft X-31A. Besides the applied hard- and software, special emphasis is given to simulation models and their updates, being marked by two new approaches: the use of nearly identical simulation software during the whole development and verification process and update of integrated simulation models due to special flight tests by means of global model system identification.

High-Fidelity Simulation for Spacecraft Autonomy Development

To maximize the profitability of modern satellites, designers must invest their spacecraft with both capability and reliability. On-board, autonomous software holds the promise of greatly enhancing spacecraft abilities, yet software glitches have been directly to blame for recent, highly publicized failures. This paper presents the flight- software development framework created for the Generalized FLight Operations Processing Simulator (GFLOPS) testbed. Based upon a robust, commercial, real- time operating system, the methodology applies principles of object-oriented design to separate sub-system software functions into protected, quasi-independent modules. The flight software modules are coupled to simulation modules, which provide high-fidelity, real-time, representations of system hardware and dynamics. The GFLOPS approach provides tools and a methodology suitable for rapid flight software development. Since the basic implementation of the framework does not rely on any advanced techniques such as autonomy, it can be used in both conservative and aggressive engineering programs. Focus applications include an MIT-designed formation flying experiment (SPHERES) and a U.S. Air Force- funded distributed satellite mission (TechSat 21). continued on page 52

The deep space 1 extended mission

The primary mission of Deep Space 1 (DS1), the first flight of the New Millennium program, completed successfully in September 1999, having exceeded its objectives of testing new, high-risk technologies important for future space and Earth science missions. DS1 is now in its extended mission, with plans to take advantage of the advanced technologies, including solar electric propulsion, to conduct an encounter with comet 19P/Borrelly in September 2001. During the extended mission, the spacecraft's commercial star tracker failed; this critical loss prevented the spacecraft from achieving three-axis attitude control or knowledge. A two-phase approach to recovering the mission was undertaken. The first involved devising a new method of pointing the high-gain antenna to Earth using the radio signal received at the Deep Space Network as an indicator of spacecraft attitude. The second was the development of new flight software that allowed the spacecraft to return to three-axis operation without substantial ground assistance. The principal new feature of this software is the use of the science camera as an attitude sensor. The differences between the science camera and the star tracker have important implications not only for the design of the new software but also for the methods of operating the spacecraft and conducting the mission. The ambitious rescue was fully successful, and the extended mission is back on track.