The Use, Evolution and Lessons Learnt of Deployable Static Solar Array Mechanisms

This paper focuses on the mechanisms incorporated into SSTL's static deployable arrays; namely the sprung-hinges and hold down and release mechanism (HDRM). Combined, the HDRM and hinges form the hold down release system (HDRS). The deployable static solar array HDRS has been successfully used on several missions, first launched upon the DMC-CFESAT spacecraft in 2007 for a U.S. customer (Figure 1), and later used on DMC-UK2 and EXACTVIEW-1 launched in 2009 and 2012, respectively. The simple, robust and low-cost solution HDRS has been evident in allowing missions to satisfy an ever increasing power demand, allowing the solar arrays to increase in size and have a preferable sun angle for increased cell efficiency. The system is now being employed on the first mission out of SSTL's U.S. office (SST-US) on the Orbital Test Bed platform. This paper shall cover details of the original design and development program, problems incurred on latter missions, and evolution of the HDRS for the present Orbital Test Bed mission. Both the original development and recent evolutions have taken place in rapid timescales, to satisfy the high-turnaround of SSTL missions

Breaking the Smallsat Barriers to Sub-50cm Imaging

New cutting-edge imaging sensors can now reduce instrument size and mass, leading to mission cost savings, and bring sub-50cm imaging capability into the realm of small satellites. Whilst aperture is essential to achieving resolution, half-pixel shifted sensor architectures decouple achievable Ground Sampling Distance (GSD) from the native ground projected pixel. This facilitates the deployment of Very High Resolution (VHR) small satellite constellations featuring improved Signal-to-Noise performance and increased area collection rates compared to push-frame systems. A fundamental limitation to the theoretical performance of an optical system is imposed by its aperture diameter; hence, for a given aperture, the aim is to maximize the information content resolved up to this limit. This is achieved by minimizing losses caused by aberrations in the optical system and enhancing platform stability on-orbit. Further information is lost due to aliasing at higher spatial frequencies; however, the recovery of such information is unlocked through the novel sensor technology and processing techniques proposed. Funded under the European Space Agency (ESA) “Investing in Industrial Innovation” (InCubed) program, this paper reports on the build and verification campaign of a sub-50cm capable instrument Proto-Flight Model (PFM), the beneficial properties of half-pixel offset sensors, and the platform supporting such a payload

DarkCarb: An Innovative Approach to Infrared Imaging

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

Business Under the Clouds

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

Synthetic Aperture Radar on a Nanosatellite - is it Possible?

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

Controversies around epithelial–mesenchymal plasticity in cancer metastasis

Experimental evidence accumulated over decades has implicated epithelial–mesenchymal plasticity (EMP), which collectively encompasses epithelial–mesenchymal transition and the reverse process of mesenchymal–epithelial transition, in tumour metastasis, cancer stem cell generation and maintenance, and therapeutic resistance. However, the dynamic nature of EMP processes, the apparent need to reverse mesenchymal changes for the development of macrometastases and the likelihood that only minor cancer cell subpopulations exhibit EMP at any one time have made such evidence difficult to accrue in the clinical setting. In this Perspectives article, we outline the existing preclinical and clinical evidence for EMP and reflect on recent controversies, including the failure of initial lineage-tracing experiments to confirm a major role for EMP in dissemination, and discuss accumulating data suggesting that epithelial features and/or a hybrid epithelial–mesenchymal phenotype are important in metastasis. We also highlight strategies to address the complexities of therapeutically targeting the EMP process that give consideration to its spatially and temporally divergent roles in metastasis, with the view that this will yield a potent and broad class of therapeutic agents.See 'additional link' for access to a free to read version of the article.</p