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NASA NTRS2003

An Internet Protocol-Based Software System for Real-Time, Closed-Loop, Multi-Spacecraft Mission Simulation Applications

The paper will provide an overview of the web-based distributed simulation software system developed for end-to-end, multi-spacecraft mission design, analysis, and test at the NASA Goddard Space Flight Center (GSFC). This software system was developed for an internal research and development (IR&D) activity at GSFC called the Distributed Space Systems (DSS) Distributed Synthesis Environment (DSE). The long-term goal of the DSS-DSE is to integrate existing GSFC stand-alone test beds, models, and simulation systems to create a "hands on", end-to-end simulation environment for mission design, trade studies and simulations. The short-term goal of the DSE was therefore to develop the system architecture, and then to prototype the core software simulation capability based on a distributed computing approach, with demonstrations of some key capabilities by the end of Fiscal Year 2002 (FY02). To achieve the DSS-DSE IR&D objective, the team adopted a reference model and mission upon which FY02 capabilities were developed. The software was prototyped according to the reference model, and demonstrations were conducted for the reference mission to validate interfaces, concepts, etc. The reference model, illustrated in Fig. 1, included both space and ground elements, with functional capabilities such as spacecraft dynamics and control, science data collection, space-to-space and space-to-ground communications, mission operations, science operations, and data processing, archival and distribution addressed.

Davis, George↗

NASA NTRS2012

Spacecraft Avionics Software Development Then and Now: Different but the Same

NASA has always been in the business of balancing new technologies and techniques to achieve human space travel objectives. NASA s historic Software Production Facility (SPF) was developed to serve complex avionics software solutions during an era dominated by mainframes, tape drives, and lower level programming languages. These systems have proven themselves resilient enough to serve the Shuttle Orbiter Avionics life cycle for decades. The SPF and its predecessor the Software Development Lab (SDL) at NASA s Johnson Space Center (JSC) hosted flight software (FSW) engineering, development, simulation, and test. It was active from the beginning of Shuttle Orbiter development in 1972 through the end of the shuttle program in the summer of 2011 almost 40 years. NASA s Kedalion engineering analysis lab is on the forefront of validating and using many contemporary avionics HW/SW development and integration techniques, which represent new paradigms to NASA s heritage culture in avionics software engineering. Kedalion has validated many of the Orion project s HW/SW engineering techniques borrowed from the adjacent commercial aircraft avionics environment, inserting new techniques and skills into the Multi-Purpose Crew Vehicle (MPCV) Orion program. Using contemporary agile techniques, COTS products, early rapid prototyping, in-house expertise and tools, and customer collaboration, NASA has adopted a cost effective paradigm that is currently serving Orion effectively. This paper will explore and contrast differences in technology employed over the years of NASA s space program, due largely to technological advances in hardware and software systems, while acknowledging that the basic software engineering and integration paradigms share many similarities.

Mangieri, Mark L.↗

NASA NTRS2016

Future Standardization of Space Telecommunications Radio System with Core Flight System

NASA Glenn Research Center (GRC) is integrating the NASA Space Telecommunications Radio System (STRS) Standard with the Core Flight System (cFS), an avionics software operating environment. The STRS standard provides a common, consistent framework to develop, qualify, operate and maintain complex, reconfigurable and reprogrammable radio systems. The cFS is a flexible, open architecture that features a plugand- play software executive called the Core Flight Executive (cFE), a reusable library of software components for flight and space missions and an integrated tool suite. Together, STRS and cFS create a development environment that allows for STRS compliant applications to reference the STRS application programmer interfaces (APIs) that use the cFS infrastructure. These APIs are used to standardize the communication protocols on NASAs space SDRs. The cFS-STRS Operating Environment (OE) is a portable cFS library, which adds the ability to run STRS applications on existing cFS platforms. The purpose of this paper is to discuss the cFS-STRS OE prototype, preliminary experimental results performed using the Advanced Space Radio Platform (ASRP), the GRC S‑ band Ground Station and the SCaN (Space Communication and Navigation) Testbed currently flying onboard the International Space Station (ISS). Additionally, this paper presents a demonstration of the Consultative Committee for Space Data Systems (CCSDS) Spacecraft Onboard Interface Services (SOIS) using electronic data sheets (EDS) inside cFE. This configuration allows for the data sheets to specify binary formats for data exchange between STRS applications. The integration of STRS with cFS leverages mission-proven platform functions and mitigates barriers to integration with future missions. This reduces flight software development time and the costs of software-defined radio (SDR) platforms. Furthermore, the combined benefits of STRS standardization with the flexibility of cFS provide an effective, reliable and modular framework to minimize software development efforts for spaceflight missions.

space communications↗

NASA NTRS2018

The Utilization Profiles of the CCSDS Unified Space Link Protocol (USLP)

The purpose of this paper is to identify the utilization profiles for interfacing the Data Protocol Sublayer using the Unified Space Link Protocols (USLP) (reference 1) with the space link coding procedures as specified in the CCSDS Coding & Synchronization Blue Books (references 2 through 5), used in both telecommand and telemetry applications. This paper describes how the USLP Protocol utilizes the coding and synchronization sublayer to support: a. Direct to Earth (DTE) telemetry links for engineering and science data b. Direct to Earth (DTE) telemetry links for very high rate science data c. Direct from Earth (DFE) command, sequencing and flight software loads d. Space to Space Links (Proximity) utilized by orbiters for data exchange to/from surface bound assets. The CCSDS has divided the functions of the Data Link Layer into two sublayers: the Data Link Protocol Sublayer (DLP-SL) and the Coding and Synchronization Sublayer (CS-SL). The Data Link Protocol Sublayer (DLP-SL) interfaces to the users, accepting the data that is to be transported, on the sending side of the link, and delivering that data on the receiving end. The Transfer Frame is the data unit that is transferred across the Data Link Protocol Sublayer and the Coding and Synchronization Sublayer boundary. The Coding and Synchronization Sublayer (CS-SL) provides the encoding, randomization, and frame synchronization functions that prepares the USLP Transfer Frame for transport across the space link. The CS-SL is divided into 2 processes: 1) The Frame Interface Processes (FIP) performs the interface functions required to prepare the data for delivery to the Coding/Decoding Process (CDP). This process includes prepending a Frame Start Marker to the provided frame, when management has designated that the frame is not to be aligned to the codeblock or when there is no block code used. 2) The Coding/Decoding Process (CDP) performs the forward error correction processes that are used to optimize the performance of the link and minimize the error rate. The CDP creates the symbol stream that is delivered to the Physical Layer. The transfer of the USLP transfer frames across different types of space links is the focus of this paper. The Protocol Data Unit (PDU) that is passed in both directions between the Data Link Protocol Sublayer (DLP-SL) and Coding and Synchronization Sublayer (CS-SL) is the transfer frame. The USLP frame structure provides flexibility that can be constrained by the functions utilized within the CS-SL that prepare the transfer frame for transit. For example, the USLP transfer frame contains a length field that enables the frame to be of variable length but CS-SL under certain conditions may constrain the frame to be fixed in length. This paper describes 5 operational modes available for use by the Data Link Layer to provide data exchange across the USLP space link. These modes are different because different operational requirements apply to vastly different types of space links and thus the communications implementation requirements differ. The environmental issues include the power or energy available, the distance between the end points of the link, the complexity of the equipment available at those end points, the atmospheric conditions and radiometric frequency selection. The CS-SL utilizes different forward error correcting codes supported by specific operational modes to configure the data for transit. This paper describes all of the operational modes in a series of data models which decompose the functionality between the Data Link Protocol Sublayer and the Coding and Synchronization sublayer. The operational modes described are: 1. Uncoded Mode: has been used for short links that contain significant available power to provide an acceptable frame error rate. The frames in this mode can be variable in length and typically use an error detection algorithm (i.e., CRC) to determine if there are errors in the received frame. 2. Convolutional Only Mode: is currently the prime forward error correction coding used for the proximity links. The frames in this mode can be variable in length and typically use an error detection algorithm (i.e., CRC) to determine if there are errors in the received frame. 3. Variable Length Frame Aligned to Variable Length Codeblock (TC): is used for Direct from Earth links were power levels are high and the simple, least complex code i.e., the BCH code is used. This mode has been in use since the early 1970s. The BCH code is a short code and the decoder is easy to implement. 4. Fixed Length Frame Aligned to Fixed Length Codeblock (AOS/TM): was introduced when the concatenated Convolutional and Reed-Solomon Code was formulated to provide significant reduction in link data error rate and the ability to determine if there was an error in the decoded codeblock. The frame is aligned to the codeblock so that there is a one to one relationship of frame errors to codeblock errors without additional error detection coding being added. This mode requires the protocol frames to be the exact size of the message portion of the codeblock. 5. Frames Unaligned to Fixed Length Codeblocks (Currently used for very high rates and space to space links): This mode is currently used for missions that have a very high data rate that can be controlled adaptively as the environment changes and as the next generation operating mode for the proximity link. This mode from a coded data stream point of view is exactly like that described in 4. above, except that the frame need not be aligned to the codeblock. There is no requirement on frame length when using this mode. Thus when using USLP it can be used to support links that require short or long frames. There is also no mandatory requirement that frames cannot be separated by idle data reducing the tight data rate connection requirements between the data link protocol sublayer and the coding & synchronization sublayer. In conclusion, how these operational modes can be put to use in mission operational scenarios is described for Direct from Earth links (DFE), Direct to Earth links (DTE), and Proximity links.

Greenberg, E.↗

NASA NTRS1982

Preliminary design of flight hardware for two-phase fluid research

This study defined the preliminary designs of flight software for the Space Shuttle Orbiter for three two-phase fluid research experiments: (1) liquid reorientation - to study the motion of liquid in tanks subjected to small accelerations; (2) pool boiling - to study low-gravity boiling from horizontal cylinders; and (3) flow boiling - to study low-gravity forced flow boiling heat transfer and flow phenomena in a heated horizontal tube. The study consisted of eight major tasks: reassessment of the existing experiment designs, assessment of the Spacelab facility approach, assessment of the individual carry-on approach, selection of the preferred approach, preliminary design of flight hardware, safety analysis, preparation of a development plan, estimates of detailed design, fabrication and ground testing costs. The most cost effective design approach for the experiments is individual carry-ons in the Orbiter middeck. The experiments were designed to fit into one or two middeck lockers. Development schedules for the detailed design, fabrication and ground testing ranged from 15 1/2 to 18 months. Minimum costs (in 1981 dollars) ranged from $463K for the liquid reorientation experiment to $998K for the pool boiling experiment.

Hustvedt, D. C.↗

NASA NTRS1989

Implementation of a production Ada project: The GRODY study

The use of the Ada language and design methodologies that encourage full use of its capabilities have a strong impact on all phases of the software development project life cycle. At the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC), the Software Engineering Laboratory (SEL) conducted an experiment in parallel development of two flight dynamics systems in FORTRAN and Ada. The differences observed during the implementation, unit testing, and integration phases of the two projects are described and the lessons learned during the implementation phase of the Ada development are outlined. Included are recommendations for future Ada development projects.

Godfrey, Sara↗

NASA NTRS2017

Colloid Microthruster Flight Performance Results from Space Technology 7 Disturbance Reduction System

Space Technology 7 Disturbance Reduction System (ST7-DRS) is a NASA technology demonstration payload as part of the ESA LISA Pathfinder (LPF) mission, which launched on December 3, 2015. The ST7-DRS payload includes colloid microthrusters as part of a drag-free dynamic control system (DCS) hosted on an integrated avionics unit (IAU) with spacecraft attitude and test mass position provided by the LPF spacecraft computer and the highly sensitive gravitational reference sensor (GRS) as part of the LISA Technology Package (LTP). The objective of the DRS was to validate two technologies: colloid micro-Newton thrusters (CMNT) to provide low-noise control capability of the spacecraft, and drag-free flight control. The CMNT were developed by Busek Co., Inc., in a partnership with NASA Jet Propulsion Laboratory (JPL), and the DCS algorithms and flight software were developed at NASA Goddard Space Flight Center (GSFC). ST7-DRS demonstrated drag-free operation with 10nmHz level precision spacecraft position control along the primary axis of the LTP using eight CMNTs that provided 5-30 N each with 0.1 N precision. The DCS and CMNTs performed as required and as expected from ground test results, meeting all Level 1 requirements based on on-orbit data and analysis. DRS microthrusters operated for 2400 hours in flight during commissioning activities, a 90-day experiment and the extended mission. This mission represents the first validated demonstration of electrospray thrusters in space, providing precision spacecraft control and drag-free operation in a flight environment with applications to future gravitational wave observatories like LISA.

Ziemer, John↗

NASA NTRS2016

SEXTANT X-Ray Pulsar Navigation Demonstration: Flight System and Test Results

The Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) is a technology demonstration enhancement to the Neutron-star Interior Composition Explorer (NICER) mission. NICER is a NASA Explorer Mission of Opportunity that will be hosted on the International Space Station (ISS). SEXTANT will, for the first time, demonstrate real-time, on-board X-ray Pulsar Navigation (XNAV), a significant milestone in the quest to establish a GPS-like navigation capability available throughout our Solar System and beyond. This paper gives an overview of the SEXTANT system architecture and describes progress prior to environmental testing of the NICER flight instrument. It provides descriptions and development status of the SEXTANT flight software and ground system, as well as detailed description and results from the flight software functional and performance testing within the highfidelity Goddard Space Flight Center (GSFC) X-ray Navigation Laboratory Testbed (GXLT) software and hardware simulation environment. Hardware-in-the-loop simulation results are presented, using the engineering model of the NICER timing electronics and the GXLT pulsar simulator-the GXLT precisely controls NASA GSFC's unique Modulated X-ray Source to produce X-rays that make the NICER detector electronics appear as if they were aboard the ISS viewing a sequence of millisecond pulsars.

SEXTANT↗

NASA NTRS2018

Hybridized Agile Software Development of Flight Control Team Tools for International Space Station's Payload Operations Integration Center

Ground systems operations at the National Aeronautics and Space Administration's (NASA) Payload Operations and Integration Center (POIC) at Marshall Space Flight Center (MSFC) recently increased via a High Operations Tempo (HOT) initiative, in order to support more science activities with a fourth crew member on the International Space Station (ISS). The Flight Control Team's (FCT) need to support this increasing pace of payload science operations was the impetus for creating a series of new tools. While their need was clear, the full scope and user experience for each tool was not as well-understood, thus establishing a fixed set of initial requirements was not feasible. A hybridized Agile Software Development (ASD) paradigm was created to take advantage of this uncertainty, plan for it, permit the exploration of novel concepts, and also facilitate a rapid and flexible response to inevitably changing requirements. The POIC's hybridized ASD approach places preeminent focus on providing customer value through the delivery of high quality, customer-focused solutions in short timeframes. This has been successfully achieved through creating unprecedented modes of cooperation and collaboration between operations and software development teams, frequent user evaluations of the software with well-defined feedback mechanisms, increased human factors involvement, and a dedication to successful outcomes by the whole of the POIC. Since space science operations and software development are not typically so closely linked, this paper discusses an approach that offers an optimal way to provide an increased return on investment and a faster time-to-completion than traditional software development paradigms, while aiming at delivering high quality products and customer-driven value.

Albers, Cerese M.↗

NASA NTRS2021

On-Board Model Based Fault Diagnosis for CubeSat Attitude Control Subsystem: Flight Data Results

Self-sufficient, robotic spacecraft require estimates of their hardware health state in order to project future system state and plan actions toward achieving mission goals. In this paper, we report on integration of a Model-Based Fault Diagnosis (MBFD) model and reasoning engine into flight software leveraging the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) mission, including test results against captured flight data using the ASTERIA system testbed. Our effort integrated the Model-based Off-Nominal State Identification and Detection (MONSID) model-based reasoning system, developed by Okean Solutions, into ASTERIA flight software using the F Prime software framework. The MONSID engine was supplied with a model of the Blue Canyon Technologies XACT attitude control system (ACS) and tested against flight data and seeded fault tests. While we were unable to conduct an on-board experiment due to the premature loss of ASTERIA, our effort proved the feasibility of on-board model-based fault management, demonstrating reliable and accurate diagnosis using captured data, and further supporting a closed-loop spacecraft autonomy demonstration including autonomous navigation in off-nominal conditions.

Prather, Maurice↗

NASA NTRS1974

HAL/S programmer's guide

The structure and symbology of the HAL/S programming language are described; this language is to be used among the flight software for the space shuttle project. The data declaration, input/output statements, and replace statements are also discussed.

Newbold, P. M.↗

NASA NTRS1976

A microprocessor-controlled CCD star tracker

The STELLAR (Star Tracker for Economical Long Life Attitude Reference) utilizes an image sensing Charge-Coupled Device (CCD) operating under microprocessor control. This approach results in a new type of high-accuracy star tracker which can be adapted to a wide variety of different space flight applications through software changes only. The STELLAR determines two-axis star positions by computing the element and the interelement interpolated centroid positions of the star images. As many as 10 stars may be tracked simultaneously, providing significantly increased stability and accuracy. A detailed description of the STELLAR is presented along with measurements of system performance obtained from an operating breadboard model.

Salomon, P. M.↗

NASA NTRS1993

Computing in space: Issues and answers

Future plans for space exploration call for scientific instruments whose data is increasingly voluminous, far exceeding constraints set by telemetry rates, and therefore, an increased role for spaceborne computing. Three issues that greatly influence the realization of spaceborne computing systems are addressed. The first involves the identification of those research problems which are unique to space computing. Resources must be expended on these problems if efforts are to add value to, and have impact on, the technology of computing in space. The second addresses the transfer of new technology from the research laboratory to use in space. What can be done to expedite this process and shrink the technology gap that separates Earth and space based systems must be assessed. The third issue involves the user's point of view of what is required of new space computing systems. That is, what are the driving forces that most influence customers' decisions to use or not use new technology? Issues of design environment for spaceborne computers, tools for modeling and evaluation of flight systems, and validation of space flight hardware and software are also discussed.

Davidson, John M.↗

NASA NTRS1999

Assurance of COTS Boards for Space Flight

Space Flight hardware and software designers are increasingly turning to Commercial-Off-the-Shelf (COTS) products in hopes of meeting the demands imposed on them by projects with short development cycle times. The Technology Validation Assurance (TVA) team at NASA GSFC has embarked on applying a method for inserting COTS hardware into the Spartan 251 spacecraft. This method includes Procurement, Characterization, Ruggedization/Remediation and Verification Testing process steps which are intended to increase the user's confidence in the hardware's ability to function in the intended application for the required duration. As this method is refined with use, it has the potential for becoming a benchmark for industry-wide use of COTS in high reliability systems.

Plante Jeannette↗

NASA NTRS1998

Assurance of COTS Boards for Space Flight

Space Flight hardware and software designers are increasingly turning to Commercial-Off-the-Shelf (COTS) products in hopes of meeting the demands imposed on them by projects with short development cycle times. The Technology Validation Assurance (TVA) team at NASA GSFC has embarked on applying a method for inserting COTS hardware into the Spartan 251 spacecraft. This method includes Procurement, Characterization, Ruggedization/Remediation and Verification Testing process steps which are intended to increase the uses confidence in the hardware's ability to function in the intended application for the required duration. As this method is refined with use, it has the potential for becoming a benchmark for industry-wide use of COTS in high reliability systems.

Plante, Jeannette↗

NASA NTRS1997

Managing Satellites

Integral Systems, Inc.'s EPOCH 2000 forms the core of NASA's Near Earth Asteroid Rendezvous (NEAR) mission's command and control center. EPOCH 2000, which allows ground operators to monitor and control satellites over a wide area network, owes part of its heritage from work completed to support Goddard Space Flight Center. The software automates telemetry processing, commanding, anomaly detection, and archiving collected data. The NEAR spacecraft, launched in February 1996, will rendezvous in early 1999 and orbit the Asteroid Eros for a year. Integral Systems also provided Low Earth Orbit Autonomous Ground Terminals (LEO-Ts) to NASA. The LEO-T is designed to make it easier and less expensive for principal investigators to obtain telemetry, tracking and control services for their science missions. The company products have supported well over 70 satellite missions aimed at scientific research, meteorology, or communications applications.

Source record↗

NASA NTRS2017

Description of the GMAO OSSE for Weather Analysis Software Package: Version 3

The Global Modeling and Assimilation Office (GMAO) at the NASA Goddard Space Flight Center has developed software and products for conducting observing system simulation experiments (OSSEs) for weather analysis applications. Such applications include estimations of potential effects of new observing instruments or data assimilation techniques on improving weather analysis and forecasts. The GMAO software creates simulated observations from nature run (NR) data sets and adds simulated errors to those observations. The algorithms employed are much more sophisticated, adding a much greater degree of realism, compared with OSSE systems currently available elsewhere. The algorithms employed, software designs, and validation procedures are described in this document. Instructions for using the software are also provided.

OSSE↗

NASA NTRS2018

Increasing Flight Software Reuse with OpenSatKit

In January 2015 the NASA Goddard Space Flight Center (GSFC) released the Core Flight System (cFS) as open source under the NASA Open Source Agreement (NOSA) license. The cFS is based on flight software (FSW) developed for 12 spacecraft spanning nearly two decades of effort and it can provide about a third of the FSW functionality for a low-earth orbiting scientific spacecraft. The cFS is a FSW framework that is portable, configurable, and extendable using a product line deployment model. However, the components are maintained separately so the user must configure, integrate, and deploy them as a cohesive functional system. This can be very challenging especially for organizations such as universities building cubesats that have minimal experience developing FSW. Supporting universities was one of the primary motivators for releasing the cFS under NOSA. This paper describes the OpenSatKit that was developed to address the cFS deployment challenges and to serve as a cFS training platform for new users. It provides a fully functional out-of-the box software system that includes NASA's cFS, Ball Aerospaceâ€"TM"s command and control system COSMOS, and a NASA dynamic simulator called 42. The kit is freely available since all of the components have been released as open source. The kit runs on a Linux platform, includes 8 cFS applications, several kit-specific applications, and built in demos illustrating how to use key application features. It also includes the software necessary to port the cFS to a Raspberry Pi and instructions for configuring COSMOS to communicate with the target. All of the demos and test scripts can be rerun unchanged with the cFS running on the Raspberry Pi. The cFS uses a 3-tiered layered architecture including a platform abstraction layer, a Core Flight Executive (cFE) middle layer, and an application layer. Similar to smart phones, the cFS application layer is the key architectural feature for userâ€"TM"s to extend the FSW functionality to meet their mission-specific requirements. The platform abstraction layer and the cFE layers go a step further than smart phones by providing a platform-agnostic Application Programmer Interface (API) that allows applications to run unchanged on different platforms. OpenSatKit can serve two significant architectural roles that will further help the adoption of the cFS and help create a community of users that can share assets. First, the kit is being enhanced to automate the integration of applications with the goal of creating a virtual cFS 'App Store'. Second, a platform certification test suite can be developed that would allow users to verify the port of the cFS to a new platform. This paper will describe the current state of these efforts and future plans.

McComas, David↗