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Defining the BUilding Basic BLocks for a U-Space SEparation Management Service

Periodic Reporting for period 1 - BUBBLES (Defining the BUilding Basic BLocks for a U-Space SEparation Management Service)

Reporting period: 2020-05-01 to 2021-04-30

BUBBLES aims to develop the ConOps for separation management for UAS, using an innovative performance-based approach inspired by the methodology used by EUROCAE to develop the ED 261 (GEN-SUR-SPR) and ED 78A standard, in order to ensure the safe and efficient operation of UAS within SES VLL. To reach this objective, the BUBBLES consortium aims to apply this methodology to a generic VLL airspace. Specifically, BUBBLES methodology starts by identifying the set of possible UAS missions and representing them by a reduced set of generic UAS ConOps detailed enough to cover all envisaged applications but, at the same time, generic enough so that their number does not make infeasible the computation of a global frequency of collisions for the whole volume. After that, a Specific Operations Risk Assessment (SORA) is conducted for each generic UAS ConOps, as well as for pair-wise conflict scenarios for all the possible combinations of UAS ConOps. BUBBLES also develops collision models and trajectory-based AI algorithms to estimate the probability of collision within a set of generic VLL sector types. These algorithms make use of the single UAS ConOps and the estimated traffic density to obtain the frequency of conflicts, while the conditional probability of collision in case of conflict is derived taking into account the results of the pair-wise conflict scenarios analyses. Afterwards, a generic Operational Services and Environment Description (OSED) is defined by the aggregation of the expected ConOps and the available U-space services. Then, the algorithms developed by the project are applied to determine the separation minima needed to guarantee a particular Target Level of Safety (TLS) stated in terms of frequency of collision, taking into account the SORA results. Once the OSED is completed with the applicable separation minima, innovative Operational Performance Assessments (OPA) and Operational Safety Assessments (OSA) based on the MEthoDology for the U-space Safety Assessment (MEDUSA) developed by the CORUS project is performed. Finally, and in line with ED261, BUBBLES also defines the general principles and functionality of tools needed for demonstrating compliance with the performance requirements and outlines methods to compute the various performance metrics. The concepts developed by BUBBLES in the initial OSED will be validated by means of a combination of simulation and test flights coupled with the OPA, OSA and IA, leading first to an updated OSED and a set of initial SPR/INTEROP (after the validation phase I) and then to a consolidated OSED/SPR-INTEROP (after the validation phase II). This iterative process is aligned with the MEDUSA and ED-78A approaches.
During the 1st reporting period, the consortium has formulated a first concept approach for the U-space Separation Management Service that will unleash the uptake of safe and efficient UAS operations within VLL airspace.
The development process carried out by the consortium to reach these results was:
Firstly, based on the expertise of the consortium and the baseline information, an initial concept of operations for the U-space separation management was developed by expanding the preliminary concept described in the project proposal, which includes the capability and operational level descriptions, based on the needs of the identified users. Moreover, a preliminary functional architecture was developed supporting the definition of functional requirements and interfaces. The maturity of the proposed concept was self-assessed leading to an Initial Concept of Operations.
Once the Initial ConOps were defined, the project set out the way to update it to achieve the expected level of maturity (V1). To this end, the following components of the concept were developed:
• A catalogue of generic UAS ConOps, with 9 relevant UAS ConOps representing most of the operations in a U-3 environment; based on them, a set of conflict scenarios were developed and the involved individual flights were addressed using SORA, leading to unmitigated and mitigated risk levels linked to them.
• A risk-based, operation-centric collision model for calculating separation minima, defining the service safety level, stated in terms of a TLS, which is expressed in terms of a collision rate.
• A methodology for automatic computation of separation minima for UAS for strategic conflict resolution. The methodology is based on the use of AI decision-making and Machine Learning (ML) techniques to train models and use their predictions to compute separation minima values in new (although operationally similar) use cases using a Sampled Trajectories and Monte-Carlo approach, guaranteeing the TLS given by the BUBBLES risk model in a computationally efficient way.
• An initial OSED based on the identified conflict scenarios encompassing a total of nine sector types and ten types of traffic (attending to the operational risk), and separation minima for them. The required U-space services in each sector type were also defined. The high-level operational description described in the initial ConOps were formulated as detailed operational requirements.
• During the definition of the OSED, the five first steps of MEDUSA were implemented. After the OSED was completed, the definition of the SPR started by de development of an integrated risk model for Mid Air Collision (MAC) was developed leading to the identification of Safety Criteria (SC). The Safety Assessment began with the identification of hazards that will support the Operational Assessment and Performance Assessments.
The BUBBLES project focuses on formulating and validating a ConOps for a U-space Separation Management Service, which is operation-centric and risk based. It does so, as described above, by adapting the ED (GEN-SUR-SPR) standard to the specific features of the UAS operations. As the research work progresses, the results indicate that it is on track to meet this objective.
Within the field of definition of UAS ConOps, BUBBLES consortium developed nine operational scenarios, covering U1 - U4 phases, detailed enough as to support SORA, but they are mission agnostic. As a contribution, these UAS ConOps describe the operation of pairs of UAS so that the hazard of mid-air collisions between UAS can be taken into account. Moreover, BUBBLES extended the SORA model to obtain a quantitative risk level for each pair of UAS ConOps.
On the other hand, BUBBLES also formulated an innovative risk model in order to guarantee a particular TLS expressed in terms of frequency of collisions. It is based on dividing the collision rate in two components:
Freq(collision) = Freq(conflict) × Prob(collision |conflict)
where Freq(conflict) depends on use-case representative trajectories, while Prob(collision |conflict) is estimated with pairwise analysis. More specifically, Freq(conflict) evaluates the impact of strategic mitigations, while Prob(collision |conflict) evaluates the impact of tactical mitigations. These results served to define a preliminary OSED for separation management in the U-space which had not previously been developed. This OSED will support the application of MEDUSA to derive SPR from a quantitative SC (MEDUSA was always applied using qualitative SCs). These results aim at making the work of Competent Authorities and U-space Service Providers easier and at contributing to increase the safety and efficiency of drone operations in the low-level airspace.