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Lunar Communications Pathfinder is planned to enable small and large satellites and landers to carry out data intensive missions around the moon, without the need for complex and costly on-board communication equipment and access to global ground networks. From the middle of this decade there are expected to be 5 to 15 active space missions on or around the moon, generating several GBytes of data per day. Lunar Communications Pathfinder is a commercial initiative with ESA and NASA as anchor tenants. The 300kg class small spacecraft is currently in manufacture for launch in 2025, and is aimed at alleviating pressure on the Deep Space Network. It will provide a commercial high speed communications service that will enable landers, orbiters, and even CubeSats to operate around the moon without requiring direct line of sight with the Earth. A small user terminal is in development as part of the service package, and a mission builder tool has been made available for planning purposes for prospective users. LCP provides a high speed intersatellite link back to Earth for a planned 8 year mission. The system is planned to be extended further with additional spacecraft, opening up the potential to provide a more comprehensive communications and navigation service. Building on LCP, the ESA Moonlight initiative has contracted a study phase in order to develop the plans for the full constellation service beyond this initial spacecraft. LCP demonstrates how small satellites can provide innovative commercial services, and enable the ability for other small satellites and landers to carry out data intensive missions. This paper will detail the spacecraft, the system design trades, and how the service is expected to evolve.

DarkCarb is a pioneering Earth observation (EO) satellite, under development at SSTL, designed to acquire high resolution Mid Wave Infrared (MWIR) imagery and video from low Earth orbit. The mission will set a precedent in IR performance from a small and capable satellite platform while maintaining the SSTL cost effective approach thereby enabling a spacecraft price which makes building constellations, capable of delivering rapid re-visit and wide area coverage, an attractive and worthwhile commercial investment. The DarkCarb satellite features an innovative low mass and volume MWIR imager which, when combined with the implementation of novel image enhancement algorithms, will achieve high quality 3.5m GSD imagery. The instrument is assembled using COTS devices and components fabricated using standard industry processes, optimised for production and rapid delivery of multiple instruments to meet constellation needs. The high spatial resolution DarkCarb MWIR imagery will deliver provides several key and complementary differentiators to visible imagery and therefore has the potential to become a high value data product for the EO market. MWIR imagery provides the capability to differentiate between objects and surfaces of different temperature and emissivity. As the detectable signal is only dependent on the temperature of the scene, DarkCarb also has the ability to extend imaging opportunities into the night. The video capability allows information on highly dynamic features in scenes to be provided and will be of key interest for applications relating to human activity. The DarkCarb mission is therefore a highly innovative development which has the potential to seriously disrupt the status quo of the commercial satellite imagery market by providing affordable high quality and high resolution MWIR data which will address a range of applications. With the DarkCarb Imager currently in production this paper will showcase the development to date with initial results from recent airborne flight trials and further explain the details of the unique payload which has been designed to meet the market need for responsive delivery at the right price.

Satellite constellations for Earth Observation almost invariably use duplicates of the same satellites to provide higher temporal resolution or greater coverage. The value of Big Data applications often depend on the fusing of different sensor information. If instead constellation satellites are equipped with a variety of sensors, these can be configured to provide more complex data products. Flexibility and in orbit rearrangement can create a range of systems that can be configured on-demand to address a range of new applications. Small satellites and sensor capability have only recently advanced far enough to make such a systems financially viable. Key challenges in such systems are optimising the composition of the constellation with different sensors or capabilities in addressing different applications, and developing methods for fusing non-contemporaneous information to build capabilities that can only be achieved through a distributed system.

Astrophysicists demand larger (mirror diameter > 10m) space optical telescopes to investigate more distant events that happened during the very early period of the universe, for example formations of the earliest stars. The deployable telescope design like James Webb Space Telescope that has a 6.5m diameter primary mirror has already reached the capacity limits of the existing launch vehicles. Therefore, the space industry has been considering using robotic technologies to build future optical reflecting three-mirror structured space telescopes in orbit from smaller components. One of the design paradigms is to use a high-DOF manipulator on a free-flying platform to build the optical telescope in orbit. This approach requires high precision and accuracy in the robotic manipulation GNC system that has several challenges yet to be addressed: 1. Orbital environmental parameters that affect sensing and perception; 2. Limitations in robotic hardware, trajectory planning algorithms and controllers. To investigate these problems for in-orbit manipulation, the UK national hub on future AI and robotics for space (FAIR-SPACE) at the Surrey Space Centre (SSC) has been developing a ground-based hardware-in-the-loop (HIL) robotic demonstrator to simulate in-orbit manipulation. The key elements of the demonstrator are two 6-DOF manipulators and a re-configurable sensor system. One of the manipulators with a > 3-DOF gripping mechanism represents the assembly manipulator on a spacecraft whose orbital dynamics, kinematics, and environmental disturbances and uncertainties are propagated in a computer. The other 6-DOF manipulator with a torque/force sensor is used as a gravity offoad mechanism to carry the space telescope mirror segment. The relative motions between the service/manipulation arm and the mirror segment are computed and then executed by the second arm. The sensor system provides visual feedback of the end-effector and uses computer vision and AI to estimate the pose and position of the mirror segment respectively. The demonstrator aims to verify and validate the manipulator assembly approach for future large space optical telescopes against ground truth and benchmarks. This paper explains the motivation behind developing this testbed and introduces the current hardware setup of the testbed and its key features.

Imaging at night time, or under the clouds has been the preserve of large powerful satellites until recent years, and now technological advances have finally made it possible to miniaturise Synthetic Aperture Radar missions in an affordable way. The NovaSAR-S spacecraft leverages a common small satellite bus coupled with a radar payload focused on a specific range of promising commercial applications. Through the inclusion of a novel wide-swath mode, and Automatic Identification of Ship receiver, a range of maritime applications are enabled. An innovative funding model was used in order to finance the mission, with a number of geographically spaced users each having fractional ownership of the spacecraft and payload tasking rights. The spacecraft can therefore look to individual owner-operators as their own spacecraft. NovaSAR-1 was launched in late 2018 and first results of this S-band SAR spacecraft with AIS ship detection are provided.

Over the next two decades, unprecedented astronomy missions could be enabled by space telescopes larger than the James Webb Space Telescope. Commercially, large aperture space-based imaging systems will enable a new generation of Earth Observation missions for both science and surveillance programs. However, launching and operating such large telescopes in the extreme space environment poses practical challenges. One of the key design challenges is that very large mirrors (i.e. apertures larger than 3m) cannot be monolithically manufactured and, instead, a segmented design must be utilized to achieve primary mirror sizes of up to 100m. Even if such large primary mirrors could be made, it is impossible to stow them in the fairings of current and planned launch vehicles, e.g., SpaceX’s Starship reportedly has a 9m fairing diameter. Though deployment of a segmented telescope via a folded-wing design (as done with the James Webb Space Telescope) is one approach to overcoming this volumetric challenge, it is considered unfeasible for large apertures such as the 25m telescope considered in this study. Parallel studies conducted by NASA indicate that robotic on-orbit assembly (OOA) of these observatories offers the possibility, surprisingly, of reduced cost and risk for smaller telescopes rather than deploying them from single launch vehicles but this is not proven. Thus, OOA of large aperture astronomical and Earth Observation telescopes is of particular interest to various space agencies and commercial entities. In a new partnership with Surrey Satellite Technology Limited and Airbus Defence and Space, the Surrey Space Centre is developing the capability for autonomous robotic OOA of large aperture segmented telescopes. This paper presents the concept of operation and mission analysis for OOA of a 25m aperture telescope operating in the visible waveband of the electromagnetic spectrum; telescopes of this size will be of much value as it would permit 1m spatial resolution of a location on Earth from geostationary orbit. Further, the conceptual evaluation of robotically assembling 2m and 5m telescopes will be addressed; these missions are envisaged as essential technology demonstration precursors to the 25m imaging system.

The implementation of a viable Synthetic Aperture Radar (SAR) mission using small satellites faces significant technological and financial challenges, and this paper evaluates how small such a spacecraft could be made whilst still fulfilling a useful mission. SAR offers a range of complementary capabilities alongside other Earth Observation systems with various unique features, but developing such spacecraft has traditionally been expensive and technologically challenging. It is only in the most recent years that small satellite SAR missions have been implemented and operated, and this paper examines the state of the art and the challenges. Furthermore the opportunities of how small SAR satellites can help realise new Earth Observation capabilities not available on existing traditional SAR satellites are described using examples of missions under development or reference design missions.

Earth Observation systems traditionally have followed the flagship mission approach. Surveillance missions carry large instruments, and focus on data quality and data volume to justify their investment. Earth science missions carry multiple instruments instead, and address a wide range of applications in order to justify their cost. Yet the “Big Data” value of these missions is often minimal, because the data sets cannot provide the temporal resolution *and* spatial resolution demanded by the majority of applications in trade, traffic, energy, disasters and even in providing useful information regarding slower phenomena like forestry and agriculture. Today it has become possible to do better than that, by utilising low cost small satellites in constellations with frequent global coverage. So far few small satellite Earth Observation constellations have been realised, but the parallel developments which have taken place in Cloud storage and Cloud computing have made it possible for EO data to be processed and distributed to worldwide users with diverse and different interests. When coupled with higher temporal resolution data from constellations this starts addressing specific opportunities. This paper focuses on the data richness that can be provided through small satellite constellations, and in particular focus on the OptiSAR and UrtheDaily constellations which aim to fuse optical, radar, video and global daily coverage of the Earth’s landmass. This, coupled with novel distribution and processing methods, will change the paradigm in how end users interact with Earth Observation data sets and the information that can be extracted automatically.

Launched in July 2015, the DMC3 constellation was designed with a “smallsat mentality” and represents the coming of age of small satellites for Earth Observation, offering performance that until a few years ago could only be found in satellites costing ten or twenty times more. The low cost of the individual satellites made it possible to deploy a constellation of 3 spacecraft, for daily global access, without any compromises in performance, at a fraction of the price of equivalent single EO satellites. The constellation started generating data 10 days after launch and has been in regular operation since the last quarter of 2015 and some results are presented in this paper. On the same launch as DMC3, SSTL deployed a prototype “video from space” satellite. Designed and built in under 8 months, Carbonite-1 demonstrated the use of very fast, low cost techniques to design and build satellites for “super-constellations”. In this paper, results from Carbonite-1 are presented and we undertake a discussion on the merits of DMC3 versus Carbonite-1 and what they offer to the EO community. We also discuss the future evolution of the DMC3 spacecraft design (the SSTL-300 S1) as well as the future plans for Carbonite.

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.

The manufacture of the NigeriaSat-2 spacecraft was completed in 2010, and was successfully launched in August 2011. This is a state-of-the-art small satellite Earth observation mission including several innovations not previously seen on small spacecraft, which will provide high duty cycle imaging of the Earth in high resolution. It will be used by the Nigerian government for mapping and to monitor a number of environmental issues within the country. The key requirements of this mission are to provide high volume mapping data, coupled with highly accurate image targeting and geolocation, and sufficient agility to enable a wide range of complex operational modes. This paper focuses on the challenges associated with designing a spacecraft system that can meet these requirements on a satellite with a mass of less than 270kg. The paper will describe how the stereo, mosaic and other imaging modes can be employed using the agility of the spacecraft. Inertia calibration and on-board navigation techniques used to give the required targeting accuracy are discussed, and the interaction between the attitude control system and the mechanical design is detailed. The payload isolation system used to ensure image quality and geolocation performance is also described. An overview of the final test and launch campaign, and first in-orbit results from the satellite commissioning are provided.

Small satellites are playing an increasing role in addressing applications in Earth Observation for scientific, civil and military applications. With all optical systems, this leads to some obvious limitations to the time of day targets can be imaged, which geographic latitudes can be covered, and to a dependency on cloud cover. For some applications this limits the utility of space systems unless low-light and through-cloud imaging information can be obtained in a timely fashion by other cost-effective means. Typically, space based radar systems are significantly more complex, more expensive, and data is more difficult to utilise than equivalent optical systems. Existing radar satellite systems therefore predominantly address scientific and military needs, leaving room for smallsat systems that address commercial needs, maritime security, and disaster monitoring. Advances in new technologies now have permitted a step performance improvement in radar systems, which will now be implemented in the NovaSAR mission which is under construction at SSTL. Gallium Nitride RF transistors enable high efficiency power amplifiers to be employed, reducing the power demand from solar panels, thus enabling a smaller radar satellite to be constructed. System innovations are also included to facilitate satellite operation in constellations, and in orbits other than the traditional dawn-dusk orbits. The spacecraft will also include an operational mode to operate in a maritime detection mode instead of imaging mode. In November 2011 the UK government announced that they are investing in the first satellite in a NovaSAR radar constellation, allowing the construction of the first 400kg satellite to commence to be ready for launch in 2014. This paper will provide details on the satellite and payload design trades, results from airborne trials of the payload, and provides an overview of the planned mission applications.

This paper will summarise the results of a hyperspectral imaging mission that has now completed more than five years in orbit and is providing a wealth of data to Users across the world. The mission has demonstrated, fairly conclusively, that such sophisticated payloads can be implemented successfully on a small satellite platform. The instrument being flown is the Compact High Resolution Imaging Spectrometer (CHRIS) developed within the Optical Payload Group (OPG) of Surrey Satellite Technology Ltd. The instrument is flying on PROBA, a small agile satellite, which was launched in October 2001. The platform provides pointing in both across-track and along-track directions, for target acquisition and multi-angle observations, particularly for measurement of the Bi-directional Reflectance Distribution Function (BRDF) properties of selected targets. The instrument covers a spectral range from 400nm to 1050nm, at £11nm resolution with a spatial sampling interval at perigee of 17m and programmable band sets. The swath width imaged is 13km at perigee. Observations requests for the science mission are selected, prioritised and scheduled into feasible observations on a daily basis. The Mission continues to operate successfully even in its sixth year and demonstrates the success of the mission and the utility of the platform and instrument.