What next? Rewilding as a radical future for the British countryside

Rewilding is an optimistic environmental agenda to reverse the loss of biodiversity and reconnect society with nature. This chapter explores Britain’s ecological history, back to the Last Interglacial before the arrival of modern humans, when the climate was similar to today, to analyse how conservationists can learn from the past to rewild the ecosystems of the present and prepare for an uncertain future. Because there is no single point in history that should or could be recreated, rewilding focuses on re-establishing naturally dynamic ecological processes that, through an appropriate sequence of species reintroductions, attempts to move the ecosystem towards a more appropriately biodiverse and functional state. A state that is self-sustaining in the present climate, and that projected for the near future. Specifically, this chapter explores a rewilding solution to conservation challenges associated with over-grazing, limited germination niche availability, and river dynamics: the reintroduction of wolves, wild boar, and beaver respectively. This sequence of reintroductions is suggested to be complimentary, each altering ecosystem dynamics to facilitate the return of the next. Evidence indicates wolves will reduce deer abundance and re-distribute browsing intensity promoting tree regeneration, particularly in riparian areas, increasing woodland availability to the more habitat-dependent wild boar and beaver. An important message behind rewilding is that a rich biodiversity with all guilds well represented, including the ones that polarize public opinion, such as large predators, are important components of ecosystem service rich and self-sustaining ecosystems, particularly in core areas

Parametric CubeSat flight simulation architecture

This paper presents the architecture of a system of models that provides realistic simulation of the dynamic, in-orbit behaviour of a CubeSat. Time-dependent relationships between sub-systems and between the satellite and external nodes (ground stations and celestial bodies) are captured through numerical analysis of a multi-disciplinary set of state variables including position, attitude, stored energy, stored data and system temperature. Model-Based Systems Engineering and parametric modelling techniques are employed throughout to help visualise the models and ensure flexibility and expandability. Operational mode states are also incorporated within the design, allowing the systems engineer to assess flight behaviour over a range of mission scenarios. Finally, both long and short term dynamics are captured using a coupled-model philosophy; described as Lifetime and Operations models. An example mission is analysed and preliminary results are presented as an illustration of early capabilities

It's hip to be square : The CubeSat revolution

With the launch of the UK’s first commercial CubeSat, UKube-1, on the horizon, Malcolm Macdonald and Christopher Lowe look at what the future holds for this standardised spacecraft platform

Through-life modelling of nano-satellite power system dynamics

This paper presents a multi-fidelity approach to finding optimal, mission-specific power system configurations for CubeSats. The methodology begins with propagation of the orbit elements over the mission lifetime, via a continuous-time model, accounting for orbital perturbations (drag, solar radiation and non-spherical geo-potential). Analytical sizing of the power system is then achieved at discrete long-term intervals, to account for the effects of variations in environmental conditions over the mission life. This sizing is based on worst case power demand and provides inputs to a numerical assessment of the in-flight energy collection for each potential solar array deployment configuration. Finally, two objective functions (minimum deviation about the orbit average power and maximum average power over the entire mission) are satisfied to identify the configurations most suitable for the specific mission requirement. Most Nano-satellites are designed with relatively simple, static-models only and tend to be over-engineered as a result, often leading to a power-limited system. The approach described here aims to reduce the uncertainty in energy collection during flight and provide a robust approach to finding the optimal solution for a given set of mission requirements

Resource considerate data routing through satellite networks

In many envisaged satellite-based networks, such as constellations or federations, there often exists a desire to reduce data latency, increase delivered data volume, or simply exploit unused resources. A strategy is presented that achieves efficient routing of data, in a store-carry-forward fashion, through satellite networks that exhibit delay- and disruption-tolerant network characteristics. This network-layer protocol, termed Spae, exploits information about the schedule of future contacts between network nodes, because satellite motion is deterministic, along with the capacity of these contacts to route data in such a way as to avoid significant overcommitment of data along a resource limited journey. Results from simulations of a federated satellite system indicate consistent benefit in terms of network performance over other, less-sophisticated, conventional methods, and comparable performance to a packet-optimal, full-knowledge approach

Building resilience by connecting the dots

Satellites typically operate in isolation from their orbiting neighbours, leaving them susceptible to even the most minor of failures. Loss of a payload, radio or critical supporting sub-system could render the platform useless, an unfavourable situation for mission stakeholders. There is however a partial solution through the addition of inter-satellite networking, which offers not only value in terms of general performance, but added resilience to failure in the form of degraded operations. While a traditional platform exhibits two fundamental states: operational (which includes the collection and dissemination of data) and failed, a network-capable platform (i.e. one with an inter-satellite communication capability) exhibits six states, each reached through a unique combination of sub-system failures. The result of this added resilience is a reduction in the likelihood of the satellite reaching a fully-failed state, at the burden of higher financial cost and complexity