Assembly, Integration & Verification

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Introduction

The Assembly, Integration and Verification (AIV) work package represents one of nine key elements that will make up the SKA1 Telescope. Whereas the other eight elements are tasked with designing key components of the SKA1 Telescope, the AIV element is tasked to perform all necessary planning to integrate these key components into a telescope system that meets the engineering (Level-1) requirements.

The SKA1 (SKA Phase 1) Telescope Reference Baseline consists of SKA1-MID, which will be located in South Africa, and SKA1-LOW, which will be located in Australia. SKA1-MID consists of approximately 200 dishes, of which 64 dishes are from the MeerKAT precursor telescope and the remaining dishes are a new design which is currently in the design phase. SKA1-LOW will consist out of approximately 512 SKA1-LOW Stations, which will include a total of approximately 130,000 individual low-frequency antennas.

The member organisations of the AIV Consortium are SARAO, CSIRO and ASTRON, with SARAO leading the consortium. All three member organisations have significant experience in building radio telescopes, and therefore have a vast amount of integration and verification know-how that is benefitting the AIV work package.

MeerKAT Integration Review

Towards the end of SKA1-MID construction, MeerKAT will be integrated into the SKA1-MID array. In order to ensure that all of the necessary integration planning has been completed and to understand the remaining integration risks, a MeerKAT Integration Review was held in Cape Town from 23–25 October 2018. The scope of the Review included an assessment of the Telescope integration planning work in preparation for System CDR, and the consideration of the programmatic aspects of integrating MeerKAT and SKA in a broader sense. A panel of SKAO and external experts led the review.

The Review Meeting started with a visit to the MeerKAT site, to help orientate the Review Panel. The review itself extended over two days, but a further day was allocated for follow-on meetings to discuss MeerKAT Lessons Learned, to agree the next steps on EMC-related work, and to finalise the post-review actions.

A total of 219 Observations (OARs) were recorded by the Panel, Reviewers and Observers, and a total of 155 Actions were agreed during the review process. The actions span the SKAO, other SKA Partner Institutions and SARAO. Some of the actions are programmatic and will be passed on to the SKA-MeerKAT Programmatic Working Group (SMPWG). The AIV Consortium is responsible for closing out 89 of these actions by January 2019.

Each OAR was discussed at the meeting and the resultant actions were categorised into one of six Action Types:

  1. No further action required
  2. Agreed action to be done as part of closure of the MeerKAT Integration work
  3. Agreed action to be done by the AIV Consortium before AIV CDR
  4. Action required by the SKAO or other Partners
  5. Proposed activity that could be part of Bridging work, detail to be agreed between SKAO/SARAO
  6. Proposed action for the SMPWG, relating to Agreements between SKAO and SARAO.

Figure 1 below shows the total number of agreed actions per Action Type, including the actions agreed before the Review Meeting.

In conclusion, the Panel Report states:

The Panel congratulates the AIV Consortium for their excellent work which has now defined the requirements, design and interfaces of the MeerKAT Integration. Commendable progress was made since the previous review in 2017 despite the small size of the team.

Previous SKA eNews editions that covered the topic of MeerKAT Integration:

Figure 1: OAR Action Types agreed during and after the Review Meeting.

Figure 2: Site visit of MeerKAT Integration Review Panel. From left to right: Donald Gammon (AIV), Craig Smith (INFRA-SA), Tracy Clarke (SEAC), Richard Lord (AIV), Peggy Perley (NRAO), Nico Kriek (SARAO), Matthew Lilley (SKAO), Marco Caiazzo (SKAO), Federico di Vruno (SKAO), Justin Jonas (SARAO), Job Obiebi (SKAO), Rick Perley (NRAO), Andreas van Zyl (SKAO).

AIV Critical Design Review (CDR)

The journey of the AIV Consortium is nearing its end. All required documentation for the AIV CDR was submitted at the end of November 2018. The review meeting itself is scheduled for the first week of March 2019.

This edition of the SKA eNews highlights some of the achievements of the AIV Team.

The Roll-Out Plans

The Roll-Out Plans for SKA1-MID and SKA1-LOW provide the basis for the delivery of products and for the planning of commissioning, integration and verification activities. They have been covered extensively in previous SKA eNews editions:

The manner in which the SKA1 Telescope is rolled-out during construction significantly affects the Observatory’s ability to mitigate risk. Radio Telescopes lend themselves to be rolled-out in stages, which makes it possible to verify the system in stages. It is imperative to identify and rectify problems as early as possible, because it becomes more and more costly and time-consuming to rectify problems further downstream. The development of the Telescope Roll-Out Plans is therefore primarily concerned with risk mitigation.

The Telescope Roll-Out Plans identify five major roll-out stages:

  • Integration Test Facility Qualification Event (ITF QE)
  • Array Assembly 1
  • Array Assembly 2
  • Array Assembly 3
  • Array Assembly 4

Figure 2: Site visit of MeerKAT Integration Review Panel. From left to right: Donald Gammon (AIV), Craig Smith (INFRA-SA), Tracy Clarke (SEAC), Richard Lord (AIV), Peggy Perley (NRAO), Nico Kriek (SARAO), Matthew Lilley (SKAO), Marco Caiazzo (SKAO), Federico di Vruno (SKAO), Justin Jonas (SARAO), Job Obiebi (SKAO), Rick Perley (NRAO), Andreas van Zyl (SKAO).

Verification Requirements

The Verification Requirements provide a high-level description of how each L1 Requirement will be verified. This work also identifies at what level of system integration the verification will be performed (ITF, AA1, AA2, AA3, AA4) and who is responsible for executing the verification. Developing Verification Requirements is an important precursor to developing the I&V Plans and Test Procedures.

Previous SKA eNews editions that described the verification planning work:

Figure 4: Relationships between Data Elements of the Verification Model.

Figure 5: Verification Events aligned within a tree structure.

Integration & Verification Plan

The Integration & Verification Plan for the SKA1-MID and SKA1-LOW Telescopes provides a structured framework in which all commissioning, integration and verification activities will be carried out in a coordinated manner during the Construction Phase. The purpose of this document is to generate a plan that can be used during the Construction Phase to manage these commissioning, integration and verification activities.

The key inputs to the I&V planning process are:

  • Verification Requirements
  • Roll-Out Plan

Pevious SKA eNews editions that covered the development of the I&V Plans:

Figure 6: Example schematic from the SKA1-LOW Integration and Verification Plan.

Figure 7: The schedule of Verification Events and Test Procedures is maintained within MS Project.

Test Procedures

High-level Test Procedures were developed that present a further elaboration of the system’s Verification Requirements, providing more detail with regard to the test setup, test method and pass/fail criteria.

Full traceability is given with regard to:

  • The originating System (Level-1) Requirement
  • The derived Verification Requirement
  • The Test Procedure executing the Verification Requirement

Some Test Procedures show no traceability to System (Level-1) Requirements. These tests are referred to as Commissioning Tests (or System Tests) and are seen to be needed to commission the system, but they do not directly verify a System (Level-1) Requirement.

Previous SKA eNews editions that covered the development of Test Procedures:

Integration Test Facility (ITF)

The ITF is an off-site laboratory environment with an end-to-end line-up of products. The qualification event in the ITF is an important precursor to shipping products to the remote sites. An important lesson that has been learned from the precursor projects is to perform as much as possible of the qualification and verification work off-site, i.e. in an ITF, where it is easier to troubleshoot any issues. A set of system-level design qualification tests will be executed in the ITF, once a representative line-up of prototype and pre-production hardware/firmware/software has been installed and integrated in such a facility. All major products of the signal chain shall be tested within the ITF, and need to successfully pass the ITF Qualification Event, prior to final installation on-site.

Product Hand-Over Process

The hand-over of products to the SKAO is an important quality gate for subsequent commissioning, integration and verification work. In order to minimise I&V issues at system level, it is important to have contractual agreements in place, so that only mature and well-tested products are received for system integration.

Previous SKA eNews editions that covered the Product Hand-Over Process:

Safety Management Plan

A Safety Management Plan was written to provide information and clarity with respect to a healthy and safe working environment during the construction phase of the SKA1 Telescopes for AIV employees, the environment, equipment and installations. This document is an addition to the main/overall SMP (from SKAO) and is specifically AIV work related.

AIV Resource Plans

One of the last documents that was written by the AIV Consortium is the AIV Resource Plan for SKA1-MID and SKA1-LOW. This document identifies the resources that are needed to perform the integration, commissioning and verification activities during construction.

The following resource categories were addressed:

  • Human Resources
  • Support Needs
  • Equipment
  • Facilities

Human Resources make up most of the AIV costs, and therefore this category was the primary focus of this document.

Challenges

Experience with other radio telescopes has consistently shown that the roll-out activities and AIV work scope is often under-estimated, even at component level, and often causes delays in deployment, due to re-engineering and retrofitting of components. This may significantly increase the total cost of the system.

Many issues that are discovered during “downstream” integration and verification are the result of “upstream” neglect. Early in the project, during the design stage, science requirements need to be accurately translated to Element-level requirements, and interfaces between products need to be accurately defined.

Figure 8: V-Diagram, showing top-down design and bottom-up verification.


Report provided by the AIV consortium