At the end of February, the Signal and Data Transport (SADT) Consortium submitted its design for the SKA’s networks to be assessed in a Critical Design Review (CDR). This marked the culmination of over four and a half years of work by the 15 different institutes that make up the Consortium. The core of the design was captured in 19 Detailed Design Documents (DDDs) which detail the various SADT sub-systems, each containing: a detailed solution description; Reliability, Availability and Maintenance (RAMs) modelling; verification plan; consideration of security, safety, maintenance, integration and interoperability; cost estimation; a statement of compliance; recommendations and a development roadmap; and discussion of outstanding issues and work. These DDDs were supported by Interface Control Documents (ICDs), which detail how the SADT sub-systems connect both internally to SADT and to other elements. Additional documents that complemented the DDDs and ICDs were also submitted, including: Engineering Diagrams; Capex and Opex cost estimate documents and spreadsheets; RFI/EMC Analysis; Hazard Analysis; RAMS and Integrated Logistics Support (ILS) report; Risk Register; Master Data Assumptions List; the SADT Compliance Matrix; Requirements Specifications; the element Verification Plan and Cross-Reference Matrix; Construction Plan and Schedule; Operations Plan; Procurement Plan; Project Management Plan and System Engineering Management Plan; Product Breakdown Structure; configuration documents; data lists; Bill of Materials. In total the SADT CDR data pack consisted of 138 formal Deliverable documents supported by an additional 100 Reference documents.
A review panel of external experts and members of the SKA Organisation reviewed the SADT design and raised a total of 1109 comments and issues captured in the Consolidated Observation Action Register (COAR). A review meeting was held between 15-18 May at the SKA HQ to discuss these COAR issues and agree any necessary amendments to the design, with two days dedicated to the synchronization and timing aspects and two days to the network architecture and data transport. The meeting was constructive and conducted in a professional and friendly atmosphere, allowing a collegial interaction between all the panel and consortium members. The panel was impressed by the completeness and robust design of the networks and concluded that the design will satisfy the SKA requirements. The panel’s conclusion was that the detailed design had conditionally passed, contingent on closing out all COAR action items and the panel congratulated the Consortium on their work. We thank the panel for all their work, especially the external experts Gie Han Tan, Vincent Ducret, Tzu-Chiang Shen, Bill Shillue and Pierre Waller, and the observer from the Science and Engineering Advisory Committee, Carole Mundell. A video showing first impressions from the SADT review is available at https://www.youtube.com/watch?v=Y7v9p65zRYs .
Since the review, the Consortium has been working on the actions identified by the panel. These have now all been completed and re-submitted to the SKAO for assessment. The amended document set, with 41 additional documents, will form a baseline for the design and will provide an excellent starting point for the overall System CDR. After the completion of CDR, the Consortium will formally be dissolved, but many of the Consortium members will continue to assist the SKAO during the Bridging Phase, implementing engineering changes that arose after the requirements freeze and addressing issues that are coming to light during the CDRs of other elements.