Bailet, Gilles

Beeley, James

McInnes, Colin R.

Timmons, Thomas

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Solar System Swarm Probes: An Earth-based Technology DemonstratorT. Timmons (t.timmons.1@research.gla.ac.uk), G. Bailet, J. Beeley and C.R. McInnesJames Watt School of Engineering, University of Glasgow, Scotland, UK. G12 8QQAs a precursor to future interplanetary probe applications, terrestrialfemto-probes (mass < 100 g) could be deployed from host satellites in lowEarth orbit to provide in-situ measurements at inaccessible locations, such asonto polar ice sheets or into mid-ocean weather systems, augmentingsimultaneous in-orbit remotely sensed data for Earth observation. This wouldprovide a means of de-risking future interplanetary applications, whiledelivering enhanced terrestrial science returns in the near-term.This strategy would be a low-cost, high-risk precursor to subsequentinterplanetary orbiters hosting femto-probe swarms as secondary payloads. Ifcandidate secondary payloads like this were firstly demonstrated throughEarth-based mission applications, this could provide a pathway to utilization insimilar or related applications on deep space missions, such as to Europa forsurface science, or to Titan for atmospheric science and oceanography.ConclusionsAbstractMission ScenarioReferencesSimulationThomas Timmons acknowledges the support of an EPSRC studentship(EP/R513222/1). This work was supported by a Royal Academy of EngineeringChair in Emerging Technologies (Colin McInnes).Acknowledgements[1] Hu, Z. et al (2019), “Development of a 10g Femto-satellite with ActiveAttitude Control,” Reinventing Space Conference, Belfast, 2019.[2] Schoolcraft, J. et al (2016), MarCO: Interplanetary Mission Development ona CubeSat Scale, AIAA SpaceOps Conference, Daejon, Korea, 2016.[3] Bailet, G., “Radiation and ablation studies for in-flight validation,” Ph.D.thesis, University of Paris-Saclay, 2019.[4] ALE Co. Ltd, “World's first man-made shooting star satellite”, https://star-ale.com/en/technology/The analysis of this exciting mission concept demonstrates not only thepotential for femto-probe swarms to augment remote orbiter data with in-situ, distributed simultaneous sensor points. Not only could this technologyenhance for Earth based applications, but also assist in exploring harshinterplanetary environments in the future.We have shown that in-situ sensing can be achieved on Earth for globalcoverage within 12 hours with as few as 4 polar orbiters using a femto-probeswarm based deployment concept, or within 2 hours with up to 30 orbiters,with a concept that could augment existing remote-sensing satellitetechnologies.Future work will investigate ejection methodologies and enhanced thermalprotection systems for femto-probes deployed at high velocity.Figure 1: University of Glasgow Femto-spacecraftWe model the potential entry, descent and landing trajectories of a femto-probe swarm deployed from one such satellite carrier in a circular polar orbitof 400 km altitude using a three-degree-of-freedom EDL code [3]. We vary theejection velocity from the carrier between 200-400 m/s, in all directions belowthe local horizon of the carrier. This order of magnitude of ejection impulsewould be possible via magnetic rail gun ejection methods [4].To assess the landing capabilities with this ejection velocity range, weperform a sensitivity analysis for a swarm ejected on a polar orbit to find thespread of reachable landing targets. As shown in Fig 2., this covers between100-140° of latitude and 2.2-6° of longitude for an ejection Δv between 200-400 m/s. This shows relative achievable coordinates, where the relativelatitude upon impact is between 45-180° ahead of the deployment latitude.An equivalent dispersion concentrated over different regions can be achievedby delaying the deployment.With an orbital period of 92 minutes at 400 km altitude, continuous globalcoverage with a Δv=400 m/s is possible with a worst-case response time of132 minutes (1 orbital period plus maximum EDL time) using 30 carrierspositioned equally along 30 orbital planes spaced 6° in longitude apart. For300 m/s and 200 m/s ejections this increases to 45 and 82 carriers spaced 4°and 2.2° in longitude apart. Maximum EDL time corresponds to the maximumattainable longitude per orbit for each Δv.Due to the rotation of the Earth (at this altitude approximately 23° perorbit), as few as 4 satellites could enable full coverage of Earth within 12 hoursif deployed with a Δv=400 m/s. Equivalently, 6 or 11 carriers spaced 4° or 2.2°apart for a Δv of 300 m/s or 200 m/s could achieve the same.Figure 3 shows the worst-case response time between deployment andlanding as a function of the number of satellite carriers for the swarm in orbitfor a polar constellation. This is shown for the three Δv values modelled. Pastthe line of continuous global coverage for each Δv, multiple satellites sharingone orbital plane can reduce the response time further to (T/n + 40) minutes,where T is the orbital period and n is the number of carriers spaced equally onthe same orbital plane.Figure 2: Femto-probe Swarm Landing CapabilitiesFigure 3: Femto-probe Response Time Vs. No. of CarriersIn the scenario considered, ChipSat femto-probes [1] (approx. 3 cm x 3 cm,10 g, Fig. 1) are contained within CubeSat sized deployers in circular polarorbits of 400 km altitude. Deployers either be standalone or attached ontolarger satellites. Equipped with micro-electro-mechanical-sensor (MEMS)suites, PCB-based probes can be rapidly produced at low cost. In a shift awayfrom traditional approaches, a swarm of these tiny sensor nodes could operatewith a large degree of redundancy, where individual probes are considereddisposable, and only a small fraction need to survive surface impact andextreme entry and descent conditions for mission success.A CubeSat carrier would be comparable terms of size and mass withprevious secondary payloads on previous interplanetary missions, such as theMarCO CubeSats [2]. Carriers would deploy a swarm of up to 100 probes whendesired to escape LEO and reenter the atmosphere, de-orbiting to remoteterrestrial locations and gathering distributed in-situ measurements. Indescent, and upon landing, the femto-probes form an ad-hoc wireless sensornetwork, relaying sensor data between femto-probes and their deployingCubeSat while in line-of-sight.Front Back

Solar System Swarm Probes: An Earth-based Technology Demonstrator

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Solar System Swarm Probes: An Earth-based Technology Demonstrator

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