Orbital debris impacts on spacecraft are an emerging threat to space missions due to the exponential increase in the number of satellites orbiting the Earth. Debris characteristics (size, material, velocity, etc.) are not well known for the size range of 10 mm or less that is undetectable using Earth telescopes or radar observation. The objective of this research was to determine wether a concept designed to detect impact of particles in the similar to 1 to 5 mm range, find the location of the impact, and characterize the impacting projectile (velocity, size, angle, density), is feasible. The paper describes the design, fabrication, and tests performed on "witness plates" (the concept) made of two parallel layers of additively manufactured aluminum and instrumented with sixteen gages, eight on each layer. Laboratory experiments have shown that the waves can be recorded and properly interpreted to find location of impact, sound speed in the plate, and to estimate impact velocity. It was shown analytically that the amplitude of the first strain wave that propagates from the impact point is expected to decay as 1/r. This was observed as well in the signals recorded in the experiments. CTH computations were performed during the pre-test design phase and the post-test analysis phase. In fact, the numerical simulations have been key and pervasive in this research effort as they provided invaluable insight for the initial design and the correct interpretation of signal anomalies seen during the tests. Additionally, the computations confirmed the 1/r law derived analytically, i.e. that the assumptions for the derivation were justified. The main conclusions of the research are that, for a normal impact, the 1/r law for front gages can be easily used to determine the diameter of the impactor. It is possible that the back gages could be used to determine the density of the impactor as well. Finally, it was shown that oblique impacts generate an expected assymetry in the signals recorded. Though this aspect should be investigated further, the assymetry is probably uniquely related to the impact angle, which could provide the angle information.

This paper describes the development and qualification of spaceflight hardware which serves as the core of a mesh network from a geostationary (GEO) orbit. The design builds upon our heritage for a high-performance single board computer (HP-SBC). Instead of a single radiation hardened Field Programmable Gate Array (FPGA), the HP-SBC uses a commercial multi-die FPGA, which greatly expands the quantity of logic cells available for firmware and also provides radiation mitigation strategies such as internal configuration scrubbing. The signal processing power of the modern commercial FPGAs is an absolute necessity and outweighs the added radiation susceptibility. Each of the four receive channels was shown to process 153 Mbps for a composite uplink and downlink rate of 1.2 Gbps. The four receive channels have 80 MHz bandwidth and are capable of demodulating 36 continuous carriers each, or they can be operated in a time division multiplexed (TDM) format depending on the firmware implementation. The system maintained Network Clock Reference (NCR) stability better than 1 part in 10 billion during an endurance test. The thermal management system was shown to dissipate loads reaching 250 Watts without issue.

Operating spacecraft in Earth orbit is an increasingly important element in nearly all business segments of the U.S. and most world economies. It is essential for national defense, communications, and remote monitoring of the Earth and the Universe around us. As our dependency on these assets exponentially grows, many Earth orbits are becoming more populated. Commercial and government entities are deploying proliferated ‘mega-constellations” of hundreds or even thousands of spacecraft. The number of spacecraft, especially in low Earth orbit, has resulted in increased risks from these vehicle's orbital debris or collisions. The unknown, and potentially significant risks posed by space debris are a major concern to both commercial and government spacecraft operators. While agencies track these spacecraft and the larger pieces of debris on a regular basis, it is limited by both the size of the debris and the quantity of objects. Objects <5cm are difficult, if not impossible, to track from Earth. The small size and large volume of such debris requires statistical risk characterization with respect to orbit, rather than tracking the individual objects. Accurate modeling requires accurate in-situ data sampling. The distribution of space debris is anticipated to increase exponentially over time, thereby requiring persistent surveillance to understand and update the magnitude of the danger. Technologies that provide in-situ characterization of the Micrometeoroid and Orbital Debris (MMOD) environment are not currently available. Southwest Research Institute® (SwRI®) is developing technology to detect, localize, and characterize MMOD impacts on spacecraft. The technology employs an array of sensitive sensors mounted to spacecraft structures. On-board processing use signals from these sensors to detect and characterize the impacts. The resulting data supports estimating the size and frequency distribution of impacts in the spacecraft's orbit, monitoring changes in this distribution over time, and even enable a rapid mitigation response to protect the vehicle or alert other vehicles within the constellation. Reliably detect and charactering spacecraft impacts allows the rejection of a vast majority of nominal spacecraft structural “noise,” in order to reduce the computational burden and data demands. The onboard processor derives information about the size of a detected impactor by analyzing the magnitude and spectral content of impact data. It also monitors differences in the arrival time of signals at the spatially distributed sensors, which provide the location of the impact and its velocity. This paper describes SwRI's ongoing efforts to develop the MMOD detection and characterization capability. It addresses the electronics design for sampling and processing sensor signals; developing processing algorithms to detect, localize, and characterize impacts; design considerations for distribution of the sensor network; testing and simulations to develop training data; and system level design considerations for applying this technology.

Abstract SwRI is developing a technology that will enable detection and characterization of micrometeoroid orbital debris (MMOD) while on-orbit. The technology includes an instrumented aluminum panel that can be installed on a satellite and, with the appropriate sensor and software suite, is able to detect and characterize impacts during the mission. The stress waves produced by the impact on the panel will be selected on-board by the software, treated, and sent to the ground for further analysis. The selection process will be directed by an algorithm that will be developed based on the experimental campaign and stress wave theory. CTH computer simulations in 2D and 3D were performed to study the viability and design the technology. Fully instrumented witness panels are being tested (August 2022) under hypervelocity impact using SwRI’s 0.17 in caliber two-stage light-gas gun. The small-scale panels were placed in the target tank to be impacted multiple times at velocities up to 6 km/s by a 3-mm al6061-T6 sphere. As expected, the strain magnitude depends on the distance to the impact point and, in general, decreases with distance.

Many astronomical observations require extended image exposures in order to improve signal to noise ratio and to provide adequate data for quantitative analysis of image contents. Maintaining accurate pointing of a telescope over the desired observation time is challenging. We consider the problem of correcting for changes in the field of view by dividing the overall observation into a series of image frames, analyzing the individual frames to estimate the changes in the field of view between frames, and performing a corrected accumulation of image frames to form the final observation. We present an automated image tracking algorithm tailored for execution on resource-constrained platforms. We show the results of extensive algorithm performance characterization studies. Finally we describe an implementation of the algorithm for a radiation-tolerant FPGA.

We present a new implementation of an image alignment and de-blurring algorithm for astronomical observations with photon-counting imagers. The algorithm substantially corrects the effects of observatory attitude changes over long observations and enables the reconstruction of images with superior resolution to those generated without alignment processing. The performance of the algorithm is quantified via simulations of a realistic observation scenario. We formulate a novel, computationally efficient implementation of the alignment algorithm that enables its use for applications with large image sizes and limited computational hardware. Such computational efficiency is critical for spaceflight applications where extreme environments limit the availability of computational hardware to components several generations behind the state of the art. We present an implementation of a Verilog realization of the alignment algorithm which is suitable for execution on a space-qualified Field Programmable Gate Array.

Recent advances in artificial intelligence (AI) and machine learning (ML) have revolutionized many fields. ML has many potential applications in the space domain. Next generation space instruments are producing data at rates that exceed the capabilities of current spacecraft to store or transmit to ground stations. Deployment of ML algorithms onboard future spacecraft could perform processing of sensor data as it is gathered, reducing data volume and providing a dramatic increase in throughput of meaningful data. ML techniques may also be used to enhance the autonomy of space missions. However ML techniques have not yet been widely deployed in space environments, primarily due to limitations on the computational capabilities of spaceflight hardware. The need to verify that high-performance computational hardware can reliably operate in this environment delays the adoption of these technologies. Nevertheless, the availability of advanced processing capabilities onboard spacecraft is increasing. These platforms may not provide the processing power of terrestrial equivalents, but they do provide the resources necessary for deploying real-time execution of ML algorithms. In this paper, we present results exploring the implementation of ML techniques on computationally-constrained, high-reliability spacecraft hardware. We show two ML algorithms utilizing deep learning techniques which illustrate the utility of these approaches for space applications. We describe implementation considerations when tailoring these algorithms for execution on computationally-constrained hardware and present a workflow for performing these optimizations. We also present initial results on characterizing the trade space between algorithm accuracy, throughput, and reliability on a variety of hardware platforms with current and anticipated paths to spaceflight.

Previous space-based assets have combined visible, near-infrared, shortwave-infrared, midwave-infrared, and longwave-infrared imagers into one “exquisite” instrument. Despite the quality of the data coming from these exquisite instruments, they have severe limitations regarding mass production, cost, and calibration complexities. Mass-produced, flexible small co-registered electro-optical/infrared space-based telescopes eliminate many of these limitations inherent in exquisite assets. For instance, our small electro-optical/infrared telescopes are considerably lower in size, weight, power, and cost; have many of their critical components commercially available; utilize heritage space-flight detector electronics and software; can be rapidly mass produced; considers the need for minimizing assembly, integration, and test in order to expedite delivery times; inherently includes an accelerated responsiveness (e.g. detectors, filters, and/or even telescopes can be readily changed to accommodate changes in mission objectives or advances in technology) of about an update every two-years. This approach becomes a disruptive game changer, particularly when implemented across a large number of SmallSats and using cross communications that provide each SmallSat with distribute high performance computing. This paper presents the Pleiades concept, preliminary performance estimates, discusses co-registration and suggests a path towards industrialization of this novel concept for multi-spectral, space-based imagery.

This paper presents a mathematical model for a cognitive communication network applicable to satellite communications with ground stations. The model employs abstract elements to describe a communications network, allowing the approach to be applied to a wide range of real-world communications systems and problems. The model includes representation of communications paths, spacecraft capabilities, time-varying demand for data transfer, changes in visibility due to satellite motion, time-varying availability of channels, and regulatory constraints on the use of radio communication bands. These model elements permit the detailed description of the structure and constraints of a communications problem. The model establishes a formal definition for a communication schedule which assigns communications resources to specific communicators at specific times. The model also formalizes constraints on the interactions between communicators, establishing the definition of a valid schedule in which communications conflicts do not occur and the definition of a good schedule in which communications resources are used efficiently. The paper also presents a dynamic reasoning methodology which uses the model to allocate communications resources in response to changing network conditions and communications loads. Implementation of the reasoning process using Answer Set Programming is demonstrated, providing illustration of the practicality of the approach. The application of the model and methodology to an example satellite communication network is presented. Using this approach significantly improved performance with respect to static resource allocation is demonstrated.

We present a design framework and software tools which support the development of high performance, high capacity data storage hardware systems employing flash memory technology. This framework facilitates the design of data storage systems which provide multiple terabits of storage and access and retrieval rates of several gigabits per second. This methodology supports the design of data storage systems with widely varying functional requirements by enabling rapid exploration of the design space, providing automatic validation of functional correctness, and providing accurate quantitative predictions of performance. We present two case studies demonstrating the flexibility and scope of this approach, and describe progress toward the implementation of a prototype data storage system designed using the framework.

CubeSats are highly accessible as Earth orbiting platforms due to their low costs of development and launch when compared to traditional small satellites. This accessibility, combined with a commensurately short development timeline, can be attributed to the use of commercial-off-the-shelf (COTS) technology. However, COTS components typically have limited inherent resilience to the space environment. As such, CubeSat usage has largely been limited to experiments or applications where high availability is not required. Several technologies are enablers for increased CubeSat performance in the environment of space. Dependable Multiprocessor (DM) technology has demonstrated the capability for high system availability and reliability with COTS processors in a space environment. DM opens many possibilities for high performance, low cost processing in space, supporting technologies such as advanced software defined radios (SDR). SDR technology allows for on-orbit reconfigurability of data management, protocols, multiple access methods, waveforms, and data protection. This paper explores how these enabling technologies hold promise for increasing the availability and capability of CubeSats, allowing CubeSats to be used in advanced applications often associated with military and commercial operations.

The ongoing development of avionics to support the Spectral Imaging of the Coronal Environment (SPICE) Electronics Box (SEB) program as part of the European Space Agency's (ESA) Solar Orbiter mission has resulted in the development of an Image Processing Field Programmable Gate Array (FPGA) (IPF). The IPF is a single FPGA containing functions to communicate with a Front End Electronics (FEE) assembly/extreme ultraviolet camera, to apply data corrections on incoming pixels, and to compress the final image product for transmission to the ground. The IPF is used as part of a larger science "observation" campaign envisaged as a series of "studies" that are scheduled using a macro execution engine maintained by the Flight Software (FSW). A macro is a lookup table (LUT) stored in memory which contains a series of SPICE commands with relative time tags for each, which determines when each command is executed. This paper discusses the design and architecture of the IPF and associated controlling software employed to meet the various engineering and science requirements of the SPICE instrument.

We present progress toward the formulation of a mathematical model for a cognitive communication network with applications to satellite systems. Our model employs abstract concepts including communicators, communications channels, and demand for capacity. These model elements may be tailored to represent a wide variety of practical communication scenarios. We present a dynamic automated reasoning methodology which uses the model to find communication resource allocations for specific scenarios that are superior to static scheduling approaches. This reasoning process resolves resource dependencies, enforces communication policies, and learns from previous communication attempts. We have implemented this reasoning process using Answer Set Prolog and used it to plan communications for a constellation of 8 satellites and 3 ground stations. The example demonstrates performance improvement over a static scheduling approach and shows how solutions can be found with reasonable computational effort.

We have developed Representation and Implementation of Temporal Event Sequences (RITES), a domain specific programming language which enables users to precisely specify how software and firmware execute with respect to real time on embedded systems hardware. Precise timing of software and firmware operations is critical to many functions within a space system, including coordination of hardware components, scheduling of spacecraft resources, and execution of communications protocols. RITES provides a highly expressive and precise mechanism to specify when software and firmware operations occur. The programming languages commonly used to develop the software and firmware for space systems (i.e. C, C++, and Verilog) do not have a built-in semantic concept of time. In contrast, RITES allows the specification of scheduled behaviors to be made and modified using concepts natural to the scheduling problem and with a compact, intuitive syntax. RITES components coordinate the activities and temporal behavior of other modules within the system rather than encapsulating complete system behavior. The RITES language is supported by a family of code generators that produce executable implementations of RITES programs. Code generators translate RITES programs to C functions for execution as software on sequential processors and to Verilog hardware description language (HDL) modules for execution within Field Programmable Gate Arrays (FPGAs). Additional code generators produce HDL implementations with error tolerance features allowing execution on FPGAs susceptible to single event effects (SEEs) in environments with significant radiation. Specifically, RITES modules may be automatically implemented as Verilog with local or distributed triple modular redundancy (TMR). We provide several examples of the implementation of precision timed behavior at various timing granularities, including clock-by-clock control of a digital signal processing (DSP) core within an FPGA for efficient execution of signal processing applications, implementation of a time division multiple access (TDMA) radio communications protocol, and a detailed study of the configuration and control of an external image compression ASIC.

Southwest Research Institute® (SwRI®) has developed a wireless transceiver that incorporates a flexible and extensible design and implementation strategy, enabling deployment of the radio to numerous roles for space missions. The transceiver was architected such that the software and the hardware could be quickly repurposed based on mission need. The software is written in ANSI standard and object oriented C++, facilitating modularity and functional reuse. The control and processing hardware is reprogrammable, allowing for the same hardware to be used in numerous applications. Although the radio frequency hardware is inherently narrow band in its conversion architecture, careful consideration to the implementation allows for quick, low cost rework to migrate between frequency bands and bandwidths. While the transceiver was originally intended for CubeSat telemetry, tracking, and command, it has now been extended in design for micro-satellite space-ground communication at S-band, micro-satellite inter-satellite crosslink communication at S-band, and small-satellite inter-satellite crosslink at Ka-band. An example of rapid repurposing of the transceiver from a Ka-band crosslink to an S-band crosslink shows the benefits of modularity and hardware/software that is architected for extensibility.

Southwest Research Institute® (SwRI®) has designed a wireless transceiver to provide inter-satellite communications as part of the Defense Advanced Research Projects Agency (DARPA) System F6 program. System F6 (Future, Fast, Flexible, Fractionated, Free-Flying Spacecraft United by Information Exchange) seeks to demonstrate the feasibility and benefits of a satellite architecture wherein the functionality of a traditional “monolithic” spacecraft is delivered by a cluster of wirelessly-interconnected modules capable of sharing their resources and utilizing resources found elsewhere in the cluster. SwRI's System F6 Wireless Inter-module Communication System (F6WICS) provides the data link and physical layers of the network stack that are specifically designed to meet the needs of fractionated space missions. F6WICS provides deterministic, real-time media access mechanisms that make efficient use of limited communications bandwidth over a wide range of spacecraft separation distances and network populations. The data link protocol is highly robust to module failure. The physical layer waveform provides robust communication, precision time transfer throughout the network, and continuous estimation of distance between spacecraft for use in navigation. The views expressed are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government. Distribution Statement “A”: Approved for Public Release, Distribution Unlimited.

Executing various combinations of external locating techniques provides many benefits over tracking and locating systems based on radar or GPS. These embedded radio positioning applications are built on a common set of functional capabilities. Development of a specific positioning system involves selection of a subset of these capabilities and implementation into a physical form that meets the size, weight and power requirements of the application while meeting cost, schedule and risk constraints. In this paper we present the design of a timing and communications engine, which is a highly configurable resource for radio positioning applications. We also present an analysis of the design trades in implementing this functionality in a field programmable gate array (FPGA) or as an application-specific integrated circuit (ASIC).

We present an algorithm and real time implementation for rapid code phase synchronization to direct sequence spread spectrum signals. The synchronization algorithm utilizes a complex matched filter to achieve code synchronization without sequential search over code phases, significantly reducing synchronization time. The algorithm is implemented on a Xilinx Spartan FPGA and is highly tailored to exploit the integrated signal processing resources on that device. Real time performance was demonstrated using less than one fourth of the device resources. Synchronization can be achieved with a latency of one code cycle and zero synchronization overhead in the signal.

In this paper we present a model-based approach for designing quality of service adaptive applications. We have developed a prototype distributed QoS modeling environment (DQME) that captures important elements of dynamic QoS adaptation at the model level. This modeling environment is designed independent of and can be integrated with, specific application domains to capture their QoS features and adaptation strategies. It combines the domain-specific modeling capability of the generic modeling environment with the QoS adaptation mechanisms of the quality objects middleware framework. DQME captures both the QoS and the functional concerns of distributed real-time embedded systems, and provides clear separation of these two. Integrated code-synthesis tools facilitate code generation and model refinement. We present a signal analyzer case study to demonstrate the use of the DQME modeling tool in real world applications.