Dish

Dish_blue

In the past few months, the Dish Consortium has completed the management hand over from CSIRO, Australia to JLRAT, China. The new Dish Consortium Lead, Wang Feng (JLRAT), and the Management Forum are now administering and serving the Dish Consortium towards its milestones.

While this path is conceivably rough, after months of coordination the Dish schedule was subsequently baselined on the 24th October and an ECP was issued to update the Dish Consortium Milestones. Currently the schedule is being updated and evaluated in real time. No schedule slip has occurred to the critical path since this ECP.

In fact, the progress in the Dish elements is promising and inspiring.

The Local Monitoring and Control (LMC) has undergone a period of change in organisation since August 2017 and is now led by INAF. Meanwhile, the activities have been focused on the software development for the Dish and, in particular, in the finalisation of the internal interfaces documents and test. An important step has been the “early integration test”, of which the integration with the Single Pixel Feed (SPF) and Receiver systems have been successfully concluded with identified actions. This exercise should be significant risk mitigation for future Dish system integration. The Test Readiness Review (TRR) for the LMC is planned in December 2017, and the team is fully involved in the preparation of the documents.

Having concluded the detailed design review (DDR) in September, the band 1 team is currently in final process to complete their qualification model. The band 1 feed is completely at ambient temperature and at the heart of their performance is a pair of very impressive Low Noise Amplifiers (LNA) designed by Low Noise Factory in Sweden as shown below. The following pictures show the current band 1 design and also the results of most recent measurement in preparation for their TRR. This review will be the signal commencement of their formal qualification test phase. Preparations are underway for the shipment of the Band 1 feed to South Africa for RFI qualification testing and follow up test on MeerKAT antenna.

Figure 1 (left). Band 1 input match measurement. Figure 2 (right). Band 1 S parameters.

Figure 3 (left). Band 1 LNA picture. Figure 4 (right). Band 1 LNA gain and noise.

The Band 2 SPF TRR has been successfully concluded and approved. SPF Band 2 and services team of EMSS Antennas have almost accomplished the setup of the qualification testing, followed by measurements of receiver noise temperature and resulting telescope receiving sensitivity (for ideal reflectors) as a function of zenith angle and frequency. The average sensitivity over frequency and tipping angle from zenith up to 30° above the horizon is above 10.9 m2/K for both polarisations, well above the 7.1 m2/K specification. Some other tests such as RFI testing and water spray testing are also in process for the preparation of the first critical design review (CDR) planned on 6th -7th December in Stellenbosch, South Africa.

Figure 5 (left). Band 2 indexer integration mock-up. Figure 6 (right). Band 2 noise temperature.

The Band 345 team is in process to refine their preliminary design. Since achieving a partial pass of their preliminary design review (PDR) in July, the team has been continuing with investigations of the vacuum and cold plumbing design. Additional lab tests have been performed to mitigate the key risks that were highlighted at the PDR and all documents have been updated, waiting for the delta PDR in January 2018.

Figure 7 (left). Band 345 turbo pump connections. Figure 8 (right). Band 345 turbo pump testing.

The Band 123 Receiver is closing out the Delta DDR. One major issue is holding up the closure of this baseline, namely the loss in array coherence when changing to Band 3. This issue is being discussed between the consortium and the SKAO to find a resolution while the team is continuing with the construction of the Qualification Model. The Band 5 Receiver is tied to the Band 5 SPF development. All documents are completed and are waiting for the delta PDR. Meanwhile, Dish Fibre Network (DFN) is now in the process of ordering the parts that will be needed for the pre-qualification and later installation on the SKA-MPI.

The Dish Structure (DS) team has been concentrating on further detail design of the two SKA Dish Prototypes. Manufacturing of major components in China, Germany and Italy has been starting and is progressing very well. The Dish Structure team has established a successful cooperation between the members from China (JLRAT), Germany (MTM), Italy (SAM) and South Africa (ITC & SKA SA office). This proven cooperation was underlined by the Dish Structure Group Ceremony held in Mainz Germany in the summer of 2017. The SKA-P Dish Structure ceremony in China will be held in the first quarter of 2018.

Figure 9. Dish Structure Group Signing Ceremony in Germany

The feed indexer has been further improved with more delicate layout, leading to the major progress on cables and the hoses routing on the feed indexer. Preparation of the Feed Indexer TRR on 30th November is almost accomplished, of which the outcomes will conduct the FAT test in Italy and China. The first SKA-P Feed Indexer will be ready for air-shipment to the integration Center in China before Christmas

Figure 10 (left). Final 3D Design Feed Indexer displaying Maintenance Access. Figure 11 (right). Feed Indexer SKA-P in Production © SAM, Italy

The servo designs of cabinets, actuators, servo sensors, encoder I/O units are about to be finalised. The azimuth driving system, encoder units, most of the sensors and all cables have been delivered to the servo integration facility in Germany. Most of the DS EMI/RFI testing will be conducted in MT Mechatronics and the Max Planck Institute in Bonn. The First concepts for EMI/RFI testing of the complete system have been discussed and the DS EMI TRR is planned for early next year.

Figure 12 (left). Azimuth Motors for SKA-P and SKA-MPI. Figure 13 (right). Azimuth and Elevation EMI I/O Units for SKA-P

The intensive manufacturing is in progress in China. The total 132 main reflector panels for two dishes have rolled off the production line. For now, 67 percent of these high-accuracy panels have been measured, showing 100 percent of acceptability. The sub-reflector moulds have been accomplished and the sub-reflector panels are being fabricated, of which the central segment shows very promising surface accuracy. The main structures of pedestal have undergone the heat treatment, waiting for the final machining, painting and assembly.

Figure 14 (left). Alistair McPherson, Deputy Director General & Head of Project, SKAO, visited the factory of CETC54 on 2nd Nov, when the 100th main-reflector panel finished. Figure 15 (right). Main reflector panel surface accuracy measurement

Figure 16 (left). The turnhead waiting for heat treatment. Figure 17 (right). The pedestal part after heat treatment

In September, with the financial support and manpower resource from CETC54, a filming team from SKAO came to JLRAT to record the manufacture of SKA dish prototype. After 5 days of effort, 40 hours of filming and 1000 kilometres of travelling, an amazing 2’30” teaser film has been produced. The film will be available shortly on the SKA YouTube channel. Stay tuned!

Figure 18. Wang Feng being interviewed for the SKAO produced dish prototype film

Figure 19. The team celebrating the filming at CETC54.

Figure 20. Screenshots from the film

With several TRRs about to come and fully prepared element design reviews, the Dish Consortium is heading towards the hardware tests and the Dish CDR steadily. Although the unexpected difficulties can actually be foreseen, there are more and more hardware, testing and results emerging from the endeavours, which gives the Dish Consortium confidence and inspiration.


Report provided by the DISH consortium