Modern computers are now far in advance of satellite systems and leveraging of these technologies for space applications could lead to cheaper and more capable spacecraft. Together with NASA AMES?s PhoneSat, the STRaND-1 nanosatellite team has been developing and designing new ways to include smart-phone technologies to the popular CubeSat platform whilst mitigating numerous risks. Surrey Space Centre (SSC) and Surrey Satellite Technology Ltd. (SSTL) have led in qualifying state-of-the-art COTS technologies and capabilities - contributing to numerous low cost satellite missions. The focus of this paper is to answer if 1) modern smart-phone software is compatible for fast and low cost development as required by CubeSats, and 2) if the components utilised are robust to the space environment. The STRaND-1 smart-phone payload software explored in this paper is united using various open-source Linux tools and generic interfaces found in terrestrial systems. A major result from our developments is that many existing software and hardware processes are more than sufficient to provide autonomous and operational payload object-to-object and filebased management solutions. The paper will provide methodologies on the software chains and tools used for the STRaND-1 smartphone computing platform, the hardware built with space qualification results (thermal, thermal vacuum, and TID radiation), and how they can be implemented in future missions.
Barnhart DJ, Vladimirova T, Ellery A, Lappas VJ, Underwood CI, Sweeting MN (2006) Utilising the EyasSAT concept in space systems engineering courses at the University of Surrey, AIAA 57th International Astronautical Congress, IAC 2006 13 pp. 9070-9083
EyasSAT is a revolutionary concept in space systems engineering education. Up until now, space systems engineering has been typically conducted behind the cloak of clean rooms protecting intellectual property by a select few individuals with millions of dollars at stake. To the contrary, EyasSAT has ushered in an opportunity for large numbers of students with varied backgrounds to build, test, and "fly" a satellite in the classroom, at virtually no financial risk. Student teams working in the context of an introductory, engineering, or professional short course are guided through virtually the entire satellite acquisition process. By the end of the course, students have worked through all the significant issues associated with each spacecraft subsystem and have a better understanding how they work in concert as a complete spacecraft system. A background on the EyasSAT development and system description is presented first. The focus of the paper is to report on the integration of EyasSAT into the University of Surrey's key space systems engineering courses: Space Mission Design for second year students and Spacecraft Bus Subsystems for third year students. The use of EyasSAT in other courses and to support student projects will also be discussed, including the first-ever student-built experiment module.
Yu G, Vladimirova T, Sweeting MN (2009) FPGA-based on-board multi/hyperspectral image compression system, Proceedings of International Geoscience and Remote Sensing Symposium 5 pp. V212-V215
Image compression is an important requirement of imaging payloads on board Earth Observation satellites. This paper presents a new on-board real-time compression system, capable of lossless and lossy image compression. A cost-effective lossless image compression scheme, based on the CCSDS recommendation, is proposed and tested with multi/hyperspectral images. An efficient hardware implementation is achieved using FPGA-based acceleration. The hardware accelerator design is optimized by employing novel techniques at algorithmic and logic levels.
Yu G, Vladimirova T, Sweeting MN (2009) Image compression systems on board satellites, ACTA ASTRONAUTICA 64 (9-10) pp. 988-1005 PERGAMON-ELSEVIER SCIENCE LTD
Barnhart DJ, Vladimirova T, Sweeting MN (2009) Satellite Miniaturization Techniques for Space Sensor Networks, J SPACECRAFT ROCKETS 46 (2) pp. 469-472 AMER INST AERONAUT ASTRONAUT
A new dimension of wireless sensor network architecture design is emerging where hundreds to thousands of ultra-light low-cost sensor nodes are required to collectively perform a spectrum of distributed remote sensing missions in hostile conditions, predominantly those encountered in space. Research is underway to investigate the feasibility of fabricating survivable self-powered sensor nodes monolithically with commercially available SiGe BiCMOS technology. This paper presents simulation and test chip results of two novel and essential building blocks: a photovoltaic/solar cell power supply and an environmentally tolerant microprocessor, based on radiation hardening by design and asynchronous logic. ©2008 IEEE.
Cutter MA, Gomes L, Da Silva Curiel A, Davies PE, De Groot Z, Sills LR, Cawthrorne A, Sweeting MN (2011) A new generation of disaster monitoring constellation imagers, 62nd International Astronautical Congress 2011, IAC 2011 3 pp. 2625-2632
Over the last decade, UK-based small satellite manufacturer Surrey Satellite Technology Ltd (SSTL) has developed and launched 6 Medium Resolution Imagers (MRI) on the SSTL-100 platform as part of the Disaster Monitoring Constellation (DMC). Currently, 5 DMC platforms are in operation augmented by platforms providing both high resolution and the MRI, such as the recently launched NigeriaSat 2 high resolution imager. The DMC constellation is operated by the consortium partners and co-ordinated by SSTL's subsidiary company DMC International Imaging Ltd (DMCii). There has been an interest in developing the DMC concept further to address a growing demand for additional capacity and capability. Consequently, two new developments of the MRI are planned for the future to enhance both the platform and the payload and provide the users with better coverage and a wider range of possible applications. The first enhancement has been enabled by platform improvements, particularly in the areas of power generation, data storage and communications. The enhancements allow the MRI to be operated whenever the satellite is flying over land and is called "Earthmapper". Earthmapper, offers full coverage of the Earth's land area in 5 days and opens up the possibility of a constellation of 5 Earthmappers imaging the whole world landmass every day. The second enhancement is a radically new optical design providing similar ground sampling to the current MRI on the SSTL-100 platforms but with significantly increased spectral range. This is an enhanced true colour imager incorporating several channels ranging from the blue to the SWIR that can, in principle, be tuned to the specific customer requirements. These two new developments are discussed below.
Vladimirova T, Bridges CP, Paul JR, Malik SA, Sweeting MN (2010) Space-based wireless sensor networks: Design issues, IEEE Aerospace Conference Proceedings
This paper is concerned with a satellite sensor network, which applies the concept of terrestrial wireless sensor networks to space. 1,2 Constellation design and enabling technologies for picosatellite constellations such as distributed computing and intersatellite communication are discussed. The research, carried out at the Surrey Space Centre, is aimed at space weather missions in low Earth orbit (LEO). Distributed satellite system scenarios based on the flower constellation set are introduced. Communication issues of a space based wireless sensor network (SB-WSN) in reference to the Open Systems Interconnection (OSI) networking scheme are discussed. A system-on-a-chip computing platform and agent middleware for SB-WSNs are presented. The system-on-a-chip architecture centred around the LEON3 soft processor core is aimed at efficient hardware support of collaborative processing in SB-WSNs, providing a number of intellectual property cores such as a hardware accelerated Wi-Fi MAC and transceiver core and a Java co-processor. A new configurable intersatellite communications module for picosatellites is outlined. ©2010 IEEE.
Barnhart DJ, Vladimirova T, Sweeting MN (2006) Satellite-on-a-chip development for future distributed space missions, Proceedings of MNT for Aerospace Applications, CANEUS2006 2006
A new dimension of space mission architectures is emerging where hundreds to thousands of very small satellites will collectively perform missions in a distributed fashion. To support this architecture, high volume production of femto-scale satellites at low cost is required. This paper reviews current and emerging distributed space systems. A conceptual design of SpaceChip, which is a monolithic "satellite-on-a-chip" based on commercial CMOS technology is detailed. Assessment of the SpaceChip design is given and its use in future distributed space missions is discussed. Copyright © 2006 by ASME.
Bellar A, Seba B, Si Mohammed AM, Sweeting MN (2010) Tree axis attitude control using sliding mode for LEO microsatellite, Latest Trends on Systems 1 pp. 181-185
Gao S, Clark K, Unwin M, Zackrisson J, Shiroma WA, Akagi JM, Maynard K, Garner P, Boccia L, Amendola G, Massa G, Underwood C, Brenchley M, Pointer M, Sweeting MN (2009) Antennas for Modern Small Satellites, IEEE ANTENN PROPAG M 51 (4) pp. 40-56 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Modern small satellites (MSS) are revolutionizing the space industry. They can drastically reduce the mission cost, and can make access to space more affordable. The relationship between a modern small satellite and a "conventional" large satellite is similar to that between a modern compact laptop and a "conventional" work-station computer. This paper gives an overview of antenna technologies for applications in modern small satellites. First, an introduction to modern small satellites and their structures is presented. This is followed by a description of technical challenges in the antenna designs for modern small satellites, and the interactions between the antenna and modern small satellites. Specific antennas developed for modern small-satellite applications are then explained and discussed. The future development and a conclusion are presented.
Mohammed AMS, Benyettou M, Boudjemai A, Hashida Y, Sweeting MN (2008) Simulation of microsatellite attitude using Kalman filtering in orbit results, SIMULATION MODELLING PRACTICE AND THEORY 16 (3) pp. 257-277 ELSEVIER SCIENCE BV
Vladimirova T, Fayyaz M, Sweeting MN, Vitanov VI (2010) A novel autonomous low-cost on-board data handling architecture for a pin-point planetary lander, ACTA ASTRONAUTICA 68 (7-8) pp. 811-829 PERGAMON-ELSEVIER SCIENCE LTD
Gao S, Brenchley M, Unwin M, Underwood CI, Clark K, Maynard K, Boland L, Sweeting MN (2008) Antennas for small satellites, Loughborough Antennas and Propagation Conference pp. 66-69
Small low-cost satellites, pioneered at Surrey, are revolutionizing space. This paper gives an overview of antenna technologies for applications in small satellites. First, an introduction to small satellites and their structure is presented. This is followed by a description of the technical challenges of antenna design for small satellites. Various antennas for small satellite applications are illustrated. A conclusion and future work at Surrey Space Centre (SSC) and Surrey Satellite Technology (SSTL) is presented in the end.
Si Mohammed AM, Benyettou M, Chouraqui S, Hashida Y, Sweeting MN (2006) Wheel attitude cancellation thruster torque of LEO microsatellite during orbital maintenance, Journal of Applied Sciences 6 (10) pp. 2245-2250
A cold gas propulsion system is used for orbital maintenance on board microsatellite. Cold gas thrusters are the simplest way of achieving thrust. A microsatellite could be a part of the constellation and to maintain a daily coverage, it will be equipped with a propulsion system for an orbit control. A constellation of several microsatellites could be launched and put at the allocate position in the orbit. To do this, the satellites need few months to be in their final position. A propulsion system is used, among other things, to maintain the satellite at its nominal position. The wheels (reaction/momentum) will be used to dump the thruster disturbances caused by misalignment. This study describes the wheel attitude damping thruster disturbances of Low Earth Orbit (LEO) microsatellite for orbit maintenance with the following points: 1) Attitude dynamics, 2) External disturbances, 3) Magnetic wheel control, 4) Simulation results will be presented to evaluate the performance and design objectives. © 2006 Asian Network for Scientific Information.
Mohammed AMS, Benyettou M, Bentoutou Y, Boudjemai A, Hashida Y, Sweeting MN (2009) Three-axis active control system for gravity gradient stabilised microsatellite, ACTA ASTRONAUTICA 64 (7-8) pp. 796-809 PERGAMON-ELSEVIER SCIENCE LTD
Abderrahmane LH, Benyettou M, Sweeting MN (2006) An S band antenna system used for communication on Earth observation microsatellite, 2006 IEEE Aerospace Conference, Vols 1-9 pp. 1033-1038 IEEE
Mohammed AMS, Boudjemai A, Hashida Y, Cooksley JR, Sweeting MN (2009) Angular Rate Estimator for LEO Microsatellite Application to Future Algerian Microsatellite, RAST 2009: PROCEEDINGS OF THE 4TH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN SPACE TECHNOLOGIES pp. 573-578 IEEE
Barnhart D, Sweeting M (2014) Right-sizing Small Satellites, Proceedings of the 28th Annual AIAA/USU Conference on Small Satellites, 2014
Utah State University
Spacecraft standardization has been a topic of great debate within the space community. This paper intends to be a provocative thought piece asking one fundamental question: ?is there a ?right size? for small satellites?? In order to answer this question, we propose three top-down design factors for the space systems engineering process: spacecraft utility, mission utility, and optimum cost. Spacecraft utility quantitatively measures the capability of a spacecraft, derived from its volume and power properties. Mission utility then measures the aggregate value of a constellation. Optimum cost, which is a function of spacecraft mass and quantity, can be determined by assessing the break-even point. Data from the small satellite community, including USAF Academy FalconSAT and Surrey Satellite Technology Ltd. (SSTL) missions, is presented in support of this discussion, constrained to systems with a mass less than 200 kg. These design factors inform the mission developer in determining the appropriate system architecture. Using these design factors, a notional standardized spacecraft configuration is presented, with a mass of 30 kg and 50 cm cubed volume that optimizes spacecraft utility, mission utility, and cost.
Barnhart DJ, Vladimirova T, Sweeting MN, Stevens KS (2009) Radiation Hardening by Design of Asynchronous Logic for Hostile Environments, IEEE JOURNAL OF SOLID-STATE CIRCUITS 44 (5) pp. 1617-1628 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Bekhti M, Sweeting MN (2010) Temperature effects on satellite power systems performance, ADVANCES IN COMMUNICATIONS, COMPUTERS, SYSTEMS, CIRCUITS AND DEVICES pp. 57-62 WORLD SCIENTIFIC AND ENGINEERING ACAD AND SOC
Sweeting MN, Underwood CI (2011) Small Satellite Engineering and Applications, pp. 575-605
Barnhart DJ, Vladimirova T, Sweeting MN (2007) Very-small-satellite design for distributed space missions, JOURNAL OF SPACECRAFT AND ROCKETS 44 (6) pp. 1294-1306 AMER INST AERONAUTICS ASTRONAUTICS
Vladimirova T, Davies P, Sweeting MN (2006) Reconfigurable computing for micro-satellites, European Space Agency, (Special Publication) ESA SP (630)
This paper presents the results of a research project, which aims to investigate the suitability of advanced technologies to on-board computing. A generic single-chip computing platform for use on-board small spacecraft, which can be reconfigured remotely from the ground station, is proposed. The platform features a highly modular structure, such that it can be quickly and easily customised to produce specific-purpose controllers for data processing, communication and control of different spacecraft subsystems and payload blocks. Two schemes for on-board run-time partial reconfiguration are proposed, which will facilitate adding and updating of peripheral cores remotely (in space). The use of the Common Object Request Broker Architecture (CORBA) for remote reconfiguration of the computing platform over TCP/IP in LEO satellite constellations is detailed.
Cai A, Underwood C, Sweeting MN (2013) Height reduction using mutual coupling for the multimode horn phased array, 2013 7th European Conference on Antennas and Propagation, EuCAP 2013 pp. 3585-3589
A novel approach is presented that demonstrates the advantage of mutual coupling in reducing the height of the multimode horn. It is found that this method can reduce the height by an additional 0.4» for the 3»×3» horn aperture and produce a smaller active element volume for the same gain in isolation and above the 81% efficiency from 8.8 GHz to 10.2 GHz for the infinite array. The mode matching model (infinite array) and Ansoft HFSS simulator (3×3 finite array) are used to demonstrate this feasibility. © 2013 EurAAP.
Boudjemai A, Bouanane MH, Hamed DEB, Mohammed AMS, Hocine R, Sweeting MN, Rojas L (2009) Microsatellite Thermal Modelling, Design Optimisation and Analysis, RAST 2009: PROCEEDINGS OF THE 4TH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN SPACE TECHNOLOGIES pp. 459-470 IEEE
Si Mohammed AM, Boudjemai A, Benyettou M, Hashida Y, Sweeting MN (2008) Yaw phase mode attitude control using Z wheel for LEO microsatellite, WSEAS Transactions on Communications 7 (2) pp. 99-105
A control system is proposed for a low Earth orbit gravity gradient stabilised microsatellite using Z wheel. The microsatellite is 3-axis stabilized using a yaw reaction wheel, with dual redundant 3-axis magnetorquers. Two vector magnetometers and four dual sun sensors are carried in order to determine the full attitude. The attitude was estimated using an Euler angles (small libration version) on based extended Kalman filter (EKF). After the satellite has been detumbled and deploy the gravity gradient boom, in order to have the accurate Nadir pointing we will use the Z zero-bias mode controller. The Z momentum wheel will be damped by the magnetorquers. This paper describes the attitude determination and control system design of LEO microsatellite using Z reaction wheel for yaw phase mode control.
Pacheco E, Sweeting MN, Underwood C, Mackin S (2009) Low-cost hyperspectral instrument for vegetation stress detection using a small satellite platform, Proceedings of AIAA Space 2009 Conference and Exposition
Stress in vegetation causes a small shift of the point of maximum slope in the spectral reflectance between 680nm and 750nm ?the so-called "red-edge" position (REP). This shift has been used as an indication of stress, both in the laboratory and in field measurements. The shift of the REP can be between 3 and 7 nm and is directly related to variations in the chlorophyll content and health condition of the plant and its leaves. The fundamental theory for this research has been the evaluation of the "red-edge" effect as a suitable means for detecting and monitoring vegetation stress using a small-satellite-borne remote sensing instrument as a cost-effective solution to global plant stress monitoring. In this work the design of a low cost instrument that uses the REP is proposed. The paper describes the fundamental theory that supports the design, and explains the main aspects of the proposed low-cost, compact hyperspectral instrument. The instrument is compatible with a small satellite platform and is proposed as a cost-effective solution for vegetation stress monitoring. Towards the instrument design, a radiometric analysis combined with the estimation of the red-edge position under different scenarios have proven to be very useful in the design of a hyperspectral solution for monitoring stress in vegetation. The existing solutions have been proved to be useful, but still have some limitations: the airborne sensors mainly in availability, coverage and cost. Space-borne instruments still need some improvements for this particular application, mainly in the spectral resolution to have sufficient spectral detail to be able to detect stress with greater accuracy.
Mohammed SAM, Benyettou M, Boudjemai A, Chouraqui S, Hashida Y, Sweeting MN (2007) COMSAT 1.0 software aided design for a low earth orbit microsatellite commissioning phase, International Journal of Soft Computing 2 (4) pp. 482-487
In the past several years, a plethora of spacecraft control techniques have been developed that address the challenging attitude tracking, stabilization and disturbance rejection requirements of these missions. One major aspect that has been typically missing in the research area of attitude control development is the experimental validation of the theoretical results. Experimental testing is necessary before control laws can be incorporated in the future generation of spacecraft. Based on this fact, we thought on the implementation of a software design COMSAT 1.0 that has the ability to overcome these difficulties. It includes all the attitude control phases, from the launcher separation i.e., initial attitude acquisition until the accurate nadir attitude pointing. This software uses micro satellites i.e., small satellites as testing models in orbit. We have chosen Alsat-1 the first Algerian micro satellite as a test model. © Medwell Journals, 2007.
Barnhart DJ, Vladimirova T, Sweeting MN, Balthazor RL, Enloe LC, Krause LH, Lawrence TJ, Mcharg MG, Lyke JC, White JJ, Baker AM (2007) Enabling Space Sensor Networks with PCBSat, SSC07-IV-4
26. D. J. Barnhart, T. Vladimirova, M.N. Sweeting, R.L. Balthazor, L.C. Enloe, L.H. Krause, T.J. Lawrence, M.G. Mcharg, J.C. Lyke, J.J. White, A.M. Baker, Enabling Space Sensor Networks with PCBSat ? Proceedings of the 21st Annual Conference on Small Satellites, ref. SSC07-IV-4, August 13-16, 2007, Utah State University, Logan Utah, USA.
Mohammed AMS, Boudjemai A, Hashida Y, Cooksley JR, Sweeting MN (2009) Simulator Development of an Attitude Determination and Control Subsystem for LEO Microsatellite Application to Alsat-1 First Algerian Microsatellite in Orbit, RAST 2009: PROCEEDINGS OF THE 4TH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN SPACE TECHNOLOGIES pp. 567-572 IEEE
Yu G, Vladimirova T, Sweeting M (2008) An efficient on-board lossless compression design for remote sensing image data, International Geoscience and Remote Sensing Symposium (IGARSS) 2 (1) pp. II970-II973
Bekhti M, Sweeting MN (2008) Power system design and in orbit performance of Algeria's first micro satellite Alsat-1, ELECTRIC POWER SYSTEMS RESEARCH 78 (7) pp. 1175-1180 ELSEVIER SCIENCE SA
Egho C, Sweeting MN, Vladimirova T (2012) Acceleration of Karhunen-Loève transform for system-on-chip platforms, Proceedings of the 2012 NASA/ESA Conference on Adaptive Hardware and Systems, AHS 2012 pp. 272-279 IEEE
The use of the Karhunen-Loève Transform (KLT) for spectral decorrelation in compression of hyperspectral satellite images results in improved performance. However, the KLT algorithm consists of sequential processes, which are computationally intensive, such as the Covariance and Eigenvector evaluations, etc. These processes slow down the overall computation of the KLT transform significantly. The acceleration of these processes within the context of limited power and hardware budgets is the main objective of this paper. The computations of each of these processes are investigated thoroughly by breaking them down into primitive arithmetic operations. Subsequently, a comprehensive analysis of these computations is presented to inspect the possibility and feasibility of different acceleration techniques, such as parallelism. The proposed designs are implemented on a System-on-a-Chip platform, which incorporates a 32-bit hardwired microcontroller and a coprocessing unit built within a field programmable gate array fabric. Two novel architectures are proposed offering accelerated processing within a very limited power budget (less than 0.225 Watt). The proposed solution is not only feasible for space applications, but also for different mobile and remote sensing applications. © 2012 IEEE.
Rachedi A, Belkacemi K, Benbouzid AB, Laidi K, Belghoraf A, Sweeting MN (2009) Radiometric pre-Calibration of Alsat-1 Camera, RAST 2009: PROCEEDINGS OF THE 4TH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN SPACE TECHNOLOGIES pp. 361-366 IEEE
Cutter MA, Giwa SC, Graham KL, Hodgson DJ, Mackin S, Sweeting MN, Vanotti M, Regan A (2008) The application of the DMC strategy and experience to provide additional support to a European Global Monitoring system programme, European Space Agency, (Special Publication) ESA SP (660 SP)
Mohammed AMS, Benyettou M, Boudjemai A, Hashida Y, Sweeting MN (2008) Yaw phase mode attitude control using Z wheel modeling for LEO microsatellite, Proceedings of the 11th WSEAS International Conference on Communications, Vol 3 pp. 243-249 WORLD SCIENTIFIC AND ENGINEERING ACAD AND SOC
35. D.J. Barnhart, T. Vladimirova, A.M. Baker and M.N. Sweeting. - Proceedings of
Sweeting M, O'Neill A, Remedios J, Golding B, Lewis A, Srokosz M, Bryden H, Lamb A, Balzter H, Smith G, Tewkesbury A, Taylor JP, Lisk I, Gibbs M, Langford H, Reynard N, Turner S, Wright T, Rosen D, Pilling C, Reeves H, Kerridge D, Loughlin S, MacDonald D, McKenzie, A, Ward R, Colenut A, Briggs S, Ryan B, Gillespie A, Lamb A (2015) Observing the Earth ? Expert views on environmental observation of the UK, DES3757
The Royal Society
Observations of the physical and built environment are of critical importance to the UK, since the environment is directly tied to our national well-being, prosperity and security. Robust observing systems are vital for understanding, managing and forecasting environmental change. It is important that we capitalise on such observations to support decision making in Government with accurate and timely scientific evidence for the greatest public benefit.
Proximity flight systems for rendezvous-and-docking, are traditionally the domain of large, costly institutional
manned missions, which require extremely robust and expensive Guidance Navigation and Control (GNC) solutions.
By developing a low-cost and safety compliant GNC architecture and design methodology, low cost GNC solutions
needed for future missions with proximity flight phases will have reduced development risk, and more rapid
development schedules. This will enable a plethora of on-orbit services to be realised using low cost satellite
technologies, and lower the cost of the services to a point where they can be offered to commercial as well as
institutional entities and thereby dramatically grow the market for on-orbit construction, in-orbit servicing and active
debris removal. It will enable organisations such as SSTL to compete in an area previously exclusive to large
institutional players. The AAReST mission (to be launched in 2018), will demonstrate some key aspects of low cost
close proximity ?co-operative? rendezvous and docking (along with reconfiguration/control of multiple mirror
elements) for future modular telescopes. However this is only a very small scale academic mission demonstration
using cubesat technology, and is limited to very close range demonstrations.
This UK National Space Technology Programme (NSTP-2) project, which is being carried out by SSTL and SSC, is
due to be completed by the end of November 2017 and is co-funded by the UK Space Agency and company R&D. It
is aiming to build on the AAReST ("Autonomous Assembly of a Reconfigurable Space Telescope") mission (where
appropriate), and industrialise existing research, which will culminate in a representative model that can be used to
develop low-cost GNC solutions for many different mission applications that involve proximity activities, such as
formation flying, and rendezvous and docking. The main objectives and scope of this project are the following:
· Definition of a reference mission design (based on a scenario that SSTL considers credible as a realistic
scenario) and mission/system GNC requirements.
· Develop a GNC architectural design for low cost missions applications that involve close proximity
formation flying, rendezvous and docking (RDV&D) - i.e. ?proximity activities?
· Develop a low cost sensor suite suitable for use on proximity missions
· Consider possible regulatory constraints that may apply to the mission
The SSTL/SSC reference mission concept is a
Future Mars exploration missions will have increasingly ambitious goals compared to current rover and lander missions. There will be a need for extremely long distance traverses over shorter periods of time. This will allow more varied and complex scientific tasks to be performed and increase the overall value of the missions. The missions may also include a sample return component, where items collected on the surface will be returned to a cache in order to be returned to Earth, for further study. In order to make these missions feasible, future rover platforms will require increased levels of autonomy, allowing them to operate without heavy reliance on a terrestrial ground station. Being able to autonomously localise the rover is an important element in increasing the rover's capability to independently explore.
This thesis develops a Planetary Monocular Simultaneous Localisation And Mapping (PM-SLAM) system aimed specifically at a planetary exploration context. The system uses a novel modular feature detection and tracking algorithm called hybrid-saliency in order to achieve robust tracking, while maintaining low computational complexity in the SLAM filter. The hybrid saliency technique uses a combination of cognitive inspired saliency features with point-based feature descriptors as input to the SLAM filter. The system was tested on simulated datasets generated using the Planetary, Asteroid and Natural scene Generation Utility (PANGU) as well as two real world datasets which closely approximated images from a planetary environment. The system was shown to provide a higher accuracy of localisation estimate than a state-of-the-art VO system tested on the same data set.
In order to be able to localise the rover absolutely, further techniques are investigated which attempt to determine the rover's position in orbital maps. Orbiter Mask Matching uses point-based features detected by the rover to associate descriptors with large features extracted from orbital imagery and stored in the rover memory prior the mission launch. A proof of concept is evaluated using a PANGU simulated boulder field.
Earth orbiting satellites come in a wide range of shapes and sizes to meet a diverse variety of uses
and applications. Large satellites with masses over 1000kg support high resolution remote sensing of the Earth,
high bandwidth communications services and world-class scientific studies but take lengthy developments and are
costly to build and launch. The advent of commercially available, high-volume and hence low cost microelectronics
has enabled a different approach through miniaturisation. This results in physically far smaller satellites that
dramatically reduces timescales and costs and that are able to provide operational and commercially viable
services. This paper charts the evolution and rise of small satellites from being an early curiosity with limited utility
through to the present where small satellites are a key element of modern space capabilities.
In many types of space mission there is a constant desire for larger and larger instrument apertures, primarily for the purposes of increased resolution or sensitivity. In the Radio Frequency domain, this is currently addressed by antennas that unfold or deploy on-orbit. However, in the optical and infrared domains, this is a significantly more challenging problem, and has up to now either been addressed by simply having large monolithic mirrors (which are fundamentally limited by the volume and mass lifting capacity of any launch vehicle) or by complex ?semi-folding? designs such as the James Webb Space Telescope. An alternative is to consider a fractionated instrument which is launched as a collection of individual smaller elements which are then assembled (or self-assemble) once in space, to form a much larger overall instrument. SSTL has been performing early concept assessment work on such systems for high resolution science observations from high orbits (potentially also for persistent surveillance of Earth). A point design of a 25 m sparse aperture (annular ring) telescope is presented. Key characteristics of 1) multiple small elements launched separately and 2) on-orbit assembly to form a larger instrument are included in the architecture. However, on-orbit assembly brings its own challenges in terms of guidance navigation and control, robotics, docking mechanisms, system control and data handling, optical alignment and stability, and many other elements. The number and type of launchers used, and the technologies and systems used heavily affect the outcome and general cost of the telescope. The paper describes one of the fractionated architecture concepts currently being studied by SSTL, including the key technologies and operational concepts that may be possible in the future.
Vision based object detection is a key feature within planetary rover navigation
which facilitates several functions such as hazard avoidance, localization and path
planning. Most of the current research is based on stereoscopic vision or multiple cameras
strategically placed along the rover chassis that perform one specific function. This
works for large rovers with sufficient processing power, however such resources would
not be very practical for small or micro-rovers.
This thesis aims to extract terrain surface information from a single camera mounted
on a micro-rover such as the Surrey Mobile Autonomy and Robotics Testbed (SMART)
based on minimal computational resources. The terrain surface information can provide
feature inputs to other on-board navigation functions such as the Planetary Monocular
Simultaneous Localisation and Mapping (PM-SLAM) and constellation matching.
The detected terrain surface can also be of scientific interest due of the geometrical
characteristics produced from this research.
This research aims to improve the processing speed of the Guidance Navigation
and Control (GNC) system using low level 2D image processing techniques. The methods
employed result in a faster "perception stage" of the GNC with lower processing
power requirements, creating structural information, shape descriptors and cognitive
segmentation/classification of the rover?s surrounding environment.
Although the initial application of this research is for planetary rovers, the research
outcome is envisaged to be relevant, and hence transferable, to other vehicle navigation
problems used on land, air or under water.
Eckersley S., Saunders C., Gooding D., Sweeting M., Whiting C., Ferris M., Friend J., Forward L., Aglietti G., Nanjangud A., Blacker P., Underwood C., Bridges C., Bianco P. (2018) In-Orbit Assembly of Large Spacecraft Using Small Spacecraft and Innovative Technologies, Proceedings of the 69th International Astronautical Congress (IAC)
International Astronautical Federation (IAF)
The size of any single spacecraft is ultimately limited by the volume and mass constraints of currently available
launchers, even if elaborate deployment techniques are employed. Costs of a single large spacecraft may also be
unfeasible for some applications such as space telescopes, due to the increasing cost and complexity of very large
monolithic components such as polished mirrors.
The capability to assemble in-orbit will be required to address missions with large infrastructures or large
instruments/apertures for the purposes of increased resolution or sensitivity. This can be achieved by launching
multiple smaller spacecraft elements with innovative technologies to assemble (or self-assemble) once in space and
build a larger much fractionated spacecraft than the individual modules launched.
Up until now, in-orbit assembly has been restricted to the domain of very large and expensive missions such as space
stations. However, we are now entering into a new and exciting era of space exploitation, where new mission
applications/markets are on the horizon which will require the ability to assemble large spacecraft in orbit. These
missions will need to be commercially viable and use both innovative technologies and small/micro satellite
approaches, in order to be commercially successful, whilst still being safety compliant. This will enable
organisations such as SSTL, to compete in an area previously exclusive to large commercial players. However, inorbit
assembly brings its own challenges in terms of guidance, navigation and control, robotics, sensors, docking
mechanisms, system control, data handling, optical alignment and stability, lighting, as well as many other elements
including non-technical issues such as regulatory and safety constraints. Nevertheless, small satellites can also be
used to demonstrate and de-risk these technologies.
In line with these future mission trends and challenges, and to prepare for future commercial mission demands, SSTL
has recently been making strides towards developing its overall capability in ?in-orbit assembly in space? using
small satellites and low-cost commercial approaches. This includes studies and collaborations with Surrey Space
Centre (SSC) to investigate the three main potential approaches for in-orbit assembly, i.e. deployable structures,
robotic assembly and modular rendezvous and docking. Furthermore, SSTL is currently developing an innovative
small ~20kg nanosatellite (the ?Target?) as part of the ELSA-d mission which will include various rendezvous and
docking demonstrations. This paper provides an overview and latest results/status of all these exciting recent in-orbit
assembly related activities.
Cannon Paul, Angling Matthew, Barclay Les, Curry Charles, Dyer Clive, Edwards Robert, Greene Graham, Hapgood Michael, Horne Richard, Jackson David, Mitchell Cathryn, Owen John, Richards Andrew, Rogers Christopher, Ryden Keith, Saunders Simon, Sweeting Martin, Tanner Rick, Thomson Alan, Underwood Craig (2013) Extreme space weather: impacts on engineered systems and infrastructure, In: Space Weather - full report
Royal Academy of Engineering
Earth Observation (EO) via remote sensing is rapidly growing in terms of satellite missions, complexity of applications and number of datasets. This situation demands that data has associated with it a quality indicator that describes the compatibility between different sensor data and suitability for particular applications.
This work describes a full end-to-end analysis of the uncertainty at a pixel level of the Top-Of-Atmosphere (TOA) radiance/reflectance factor products. It develops a methodology framework that can be adapted and reproduced by several EO missions to provide TOA radiometric uncertainty. The method is not only described but implemented as a software tool named Radiometric Uncertainty Tool (RUT) using as an example the Sentinel-2 (S2) mission.
The uncertainty methodology starts from a radiometric model, where a set of uncertainty contributors are identified and specified at a pixel level, by reviewing the pre- and post-launch sensor radiometric characterisations. These contributors are assessed using the metadata and quality information associated to the satellite products where possible. As a consequence, the uncertainty contributions are specified for the specific satellite acquisition time, scene and processing. Some of the uncertainty contributions required the use of novel estimation methods that have been specifically applied to the assessment of the uncertainty propagation produced by the image orthorectification and the radiometric impact of the spectral knowledge. The study proposes an uncertainty combination model with an important effort in using the best metrological practices as described in the ?Guide to Expression of Uncertainty in Measurement? (GUM) model. The assumptions in the model have been validated by comparing the results to a Monte Carlo Method (MCM), the correlation among the different uncertainty contributions has been studied, and the impact of simplifications in the combination model has been assessed. As an extension of the work towards its larger application, a methodology has been proposed and implemented to estimate the uncertainty associated to the mean of the pixels in a Region of Interest (ROI). The study considers the correlation of the pixels in the spatial, temporal and spectral dimension. As a result, the TOA radiometric uncertainty estimates can be of direct use for applications as the radiometric validation activities or product spatial binning. Further extension of the uncertainty concepts has resulted in a set of tools, algorithms and methodologies that have been used in order to estimate the radiometric uncertainty achievable for an indicative target sensor through in-flight cross-calibration using a well-calibrated hyperspectral SI-traceable reference sensor with observational characteristics such as TRUTHS (Traceable Radiometry Underpinning Terrestrial and Helio-Studies) mission. This study considers the criticality of the instrumental and observational characteristics on pixel level reflectance factors, within a defined spatial ROI within the target site. It quantifies the main uncertainty contributors in the spectral, spatial, and temporal dimension.
Space telescopes are our ?eyes in the sky? that enable unprecedented
astronomy missions and also permit Earth
observation integral to science and national security. On
account of the increased spatial resolution, spectral coverage,
and signal-to-noise ratio, there is a constant clamour
for larger aperture telescopes by the science and surveillance
communities. This paper addresses a 25 m modular
telescope operating in the visible wavelengths of the electromagnetic
spectrum; such a telescope located at geostationary
Earth orbit would permit 1 m spatial resolution of
a location on Earth. Specifically, it discusses the requirements
and architectural options for a robotic assembly
system, called Robotic Agent for Space Telescope Assembly
(RASTA). Aspects of a first-order design and initial
laboratory test-bed developments are also presented.
Earth Observation via satellite has been successfully used for several decades in many applications. Monitoring climate change is the most challenging one, as it requires highly accurate data to enable detection of small changes in naturally variable signals over different spatial and temporal scales. A measure used in metrology to assess the quality of the data is measurement uncertainty. However, to date, many satellite products still do not have uncertainties, the accuracy requirements are not defined precisely and even calibrations are performed without associated measurement uncertainty budgets. Thus is it often impossible to put an unbiased quality mark to the data that, by default, requires the highest levels of accuracy. This poses the risks of using poor quality data as the input to climate change models.
This research focuses on the \ground truth" measurement methodology called vicarious calibration. This is an independent post-launch satellite calibration technique based on a comparison of satellite readings with ground data and atmospheric modelling. Two test sites were selected as examples, land and ocean, to have uncertainty evaluated for their ground products following the Guide to the Expression of Uncertainty in Measurement (GUM) methodology.
A new radiometric calibration site, Gobabeb in the Namib Desert, was established for radiometric calibration of Top-of-Atmosphere (TOA) radiance/reflectance level 1 (L1) satellite products, and a campaign was conducted to measure the ground's reflectance. All instruments used during the initial characterisation were previously calibrated and characterised in optical laboratories. The in situ uncertainty budget was evaluated and validated by the comparison of the results to an alternative measurement source. The primary input of this research to the scientific community, apart from the new site, is a revised SI traceability chain for the ground reflectance field measurements. Hitherto, the reflectance reference standards used in situ had a calibration that did not match field illumination conditions. Although this problem was known, often it was not addressed or dealt with accurately. This study proposed a new field calibration value for the reflectance standard that combines direct and diffuse components weighted accordingly to the wavelength and atmospheric conditions during the measurement.
The work on the ocean site concentrated on the existing Boueé pour l?acquisition de Séries Optiques á Long Terme (BOUSSOLE) site that is permanently deployed in the Ligurian Sea and provides Bottom of Atmosphere (BOA) water leaving radiance/reflectance level 2 (L2) Ocean Colour System Vicarious Calibration (SVC). This site had a preliminary uncertainty estimated as one generic number for all spectral channels and environmental conditions. A new uncertainty budget was developed by a detailed evaluation of each identified uncertainty component and these were combined by applying the Monte Carlo Method (MCM). As a result, a dynamic uncertainty evaluation for each measurement and the spectral band was produced addressing real measurement conditions and their effects on the quality of the relevant in situ products.