To demonstrate in an operational environment offline antenna arraying between Cebreros and Malarg?e with timely delivery of science products (within one day from signal reception at receiving antennas) with 40MHz acquisition bandwidth and 2 or 4-bits signal amplitude quantisation (per complex component), suitable for data rates up to 10Mbps with turbo 1/4 or 20Mbps with turbo 1/2, when using GMSK BT=0.5 or filtered O-QPSK. Optionally to demonstrate the same operational capability with a pair of ground stations from ESA and NASA sites (e.g. Cebreros and Robledo, or New Norcia and Canberra, or Malarg?e and Goldstone).

During its science phase EnVision will use ESTRACK antennas located at the three ESA deep space sites in New Norcia (Western Australia), Cebreros (Spain) and Malarg?e (Argentina), and optionally the DSN antennas located at the NASA sites of Canberra (Australia), Robledo (Spain) and Goldstone (United States of America). In order to increase the flexibility in the selection of the ground stations, or alternatively to increase the data volume, offline arraying between distant antennas is proposed during overlapping visibility slots. In particular the activity focuses on visibility overlap between Cebreros and Malarg?e, which offer the greatest potential. During such time slots the data rate can be increased by around a factor two with respect to the reception from a single antenna. Offline arraying implies a significant delay between reception of the signal at the antennas and delivery of the final products to the user, as well as a channel bandwidth limitation, both due to the need to record and transfer digital raw samples between remote locations across the wide area network. Whereas a significant delay can be acceptable for science data, it is not tolerable for satellite housekeeping data. For the above reason offline arraying is only proposed for Ka-Band downlink which will be devoted to transmission of science data only.There are essentially two main use cases in this proposal: in the first, the arraying passes are defined in order to ensure that the same aggregate effective tracking time (out of planetary occultations) is achieved with arraying as in the case of no-arraying. The interest in the arraying option is justified in this case by the fact that the data volume is still compliant with the mission requirements, and at the same time the transmission time is reduced. This is the use case that introduces flexibility in the selection of ESTRACK stations and, by reducing the duration of the transmission to Earth (normally ?stolen? to the production of science data), is beneficial to spacecraft and payload operations. In the second use case the transmission time is left unchanged with respect to the no-arraying baseline, with the simple aim of increasing the data rate and therefore the data volume.The activity is structured according to the following tasks1. System requirements review and consolidation: the driving system (level 0) requirements applicable to the activity have been established in [RD-1] which is attached to this proposal, based on the EnVision Science Operations Reference Scenario, and can be summarized in the capability of combining two data streams, representing 40MHz wide signals, at a processing speed of around 1.6 Tbits per hour, allowing to comply with an overall latency in the delivery of science products of up to one day, including the data transfer through the wide area network, and with small combining loss due to adoption of Full Spectrum Combining (FSC). For data rates exceeding the above bandwidth, alternative scenarios may be conceived where Symbol Stream Combining (SSC) or Complex Stream Combining (CSC) or Baseband Combining (BC) are used instead of FSC. Additional system requirements will be defined related to the operability (integration in ESTRACK operations including monitor and control aspects) and availability of the arraying combining function. Furthermore the capacity, latency and availability requirements to be posed to the wide area network services will be expressed (to be used for costing), and scalability requirements will be formulated, related to the possibility of combining more than two antennas, as well as to the potential use of the arraying/combiner in quasi real time, when arraying collocated terminals. The output of this tasks is a set of level 1 requirements to be used for the subsequent phases of the activity.2. System design: starting from the level 1 system requirements, and based on the previous bread-board implementation (TRP activity T212-052GS), the system architecture of the arraying/combiner will be defined, executing key trade off, primarily about the selection of the combining method (FSC, SSC, CSC, BC), selection of either hardware/firmware or software implementation for the core processing tasks, as well as inclusion of demodulation/decoding tasks vs. RF or basband interface with existing modems. Furthermore the use of processing over the Cloud will be explored. Inputs and output interfaces will be defined. Key algorithms will be reviewed from the previous TRP activity and scrutinized for performance enhancement, in particular identifying any need for code parallelization. The validity of the system design will be confirmed by simulations addressing the key performance aspects. The output of this tasks will be a complete system design subject to ESA critical review and approval. 3. Breadboard implementation: this task will include all required hardware procurement and firmware/software development, as defined in the previous task. The implementation will be confined to a non redundant bread-board arraying/combiner, however compliant with the key identified functional and performance requirements. In parallel with the breadboard arraying/combiner, an array data generator will be implemented, able to produce simulated data streams with different scenarios in terms of data rate, modulation, coding, focused on EnVision as well as on flying Ka-Band mission (e.g. BepiColombo).4. Testing and validation: the testing will proceed incrementally, by addressing individual components, internal interfaces, external interfaces and overall system. At every layer, functional and performance tests will be performed to verify full compliance with the requirements. The system tests will be performed first by using the array data generator, then by tests executed in ESOC ground segment facilities (GSRF), and finally with a flying spacecraft. In particular, for the final test session, it is envisaged to use BepiColombo Ka-Band passes, however retaining the full signal acquisition setup suitable for EnvVision (and oversized for BepiColombo), and optionally to aim at the inclusion of a temporary wide area setup compatible with EnVision needs. RD-1 Offline arraying for EnVision, OPS-GS/2756/ML, 27/7/2020