Fractal Resampling      Introducing innovative technologies        in support of mission operationsThe Case Study – On-boa...
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Fractal Resampling: Enhancing Observability on Ground for the same or even less bandwidth


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On-board observability depends on the sampling rate used to perform on-board measurements. The fractal resampling technique allows high sampling on board while sending very little data that can account for the most interesting information. This separation between data and information allows gaining on-board observability while reducing bandwidth requirements. The fractal resampling technique is currently used to enable data plotting for online applications.

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Fractal Resampling: Enhancing Observability on Ground for the same or even less bandwidth

  1. 1. Fractal Resampling Introducing innovative technologies in support of mission operationsThe Case Study – On-board observabilitydepends on the sampling rate used toperform on-board measurements. It iscommon practice to increase the samplingrate in order to capture short lived events. Venus Express Thrusters’ Temperature. Left: original time series with 10003However, in some cases the sampling rate samples; right: fractal resampled version allowing 1% error with 356cannot be increased to satisfactory levels samples.due to bandwidth limitations. It is a common error to equate data with looking at a silhouette of a mountain in a 2d information. This misconception results on plane it reminds a time-series.The Solution – The Fractal Resampling the belief that a lot of data is needed to havetechnique allows high sampling on-board a lot of information. We make a clear Although DrMUST has been designed withwhile sending very few data that account distinction between data and information that the goal of supporting anomaly investigation; allows to retain almost all information with it can also be used to perform system orfor the most interesting information. This much less data. We define both concepts in subsystem characterization. This processseparation between data and information the housekeeping telemetry context: helps engineers in identifying potential areasallows to gain on-board observability while  Data: measurements performed by of concern when operating the spacecraft in sensors or instruments, usually at a different modes.reducing bandwidth requirements. Fractal periodic sampling rate.Resampling works by accepting a small  Information: subset of data needed to gain The applications of the Fractal Resamplingconfigurable error. The resulting knowledge or make decisions technique are the following:resampled time series guarantees that the  Better Observability: currently, For many practical spacecraft operations housekeeping telemetry come in packetserror made is not bigger than the scenarios the noise associated to a given sampled at regular intervals. In order toconfigured one at any given point. measurement does not bring extra capture short-lived events, sometimes a knowledge and will not change any decision; parameter or packet needs to be sampledCurrent Status – Fractal resampling has therefore the noise could be removed safely and down-linked at very high frequencybeen prototyped to demonstrate its without information loss. even if most of the samples would not be relevant. However, this high sampling ratefeasibility. At the moment it is being used The Fractal Resampling reduces the amount is limited by the available bandwidth. Theas a lossy compression technique to of data while keeping almost the same fractal-inspired resampling allowsenable web plotting clients. The ESA information. It works by removing the points obtaining better observability with muchPatent Group has decided to protect that do not provide additional information but less samples. This translates in having contribute to the amount of data that needs to higher-fidelity information on ground. TheFractal Resampling by filing a patent be transferred. It needs at input what is the benefits are twofold: better observabilityapplication in the European Patent Office. maximum allowed error. For instance, in the and reduced bandwidth requirements. figure above, the maximum allowed error is  Lossy Compression: Finding the optimalProject Team – Developed for the ESA 0.42 degrees Celsius. This means that when sampling of a time series guaranteeing aAdvanced Mission Concepts and connecting the remaining points (after maximum error results most of the times in resampling) with straight lines, the error at an important reduction in the number ofTechnologies Office by Black Hat S.L., any of the missing points is guaranteed to be samples. In this sense, the FractalSpain, and Solenix GmbH, Switzerland. less than or equal to 0.42 degrees Celsius. Resampling can be seen as a lossy compression technique. The advantage asESA/ESOC, Darmstadt, Germany The Fractal Resampling technique is inspired compared with other lossy compressionAdvanced Mission Concepts and Technologies Office by the method that some simulators and techniques is that the maximum error canContact: Alessandro DonatiE-mail: video games use to randomly generate be guaranteed.Tel: +49 6151 90 2574 terrain, in either 3d or 2d planes. When  Others: noise removal, storage reduction