Dish

Dish_blue

In the past few months, all of the Dish’s sub-element teams have been busy with the qualification tests and review preparations. The mechanical alignment of SKA-P was completed in June in China; the second prototype dish, SKA-MPI, recently arrived in South Africa; and the SPF Band2 and Band1 have also been installed on MeerKAT Dish #21.

Together with the system engineering team, the SPF team is working on the integration testing and the SPF Band1 CDR. The SPF Band5 has been continuing with the tests of the cryostat system as well as the detailed design and review process. The receiver team has also undergone the challenge of design alteration and with progress being reported. The qualification model tests of LMC are almost completed and DFN has started the hardware procurement process.

With so many milestones taking place especially for the completion of various qualification models, the system engineering (SE) team has been endeavoring towards the test readiness review (TRR). Together with the sub element teams, the SE team has successfully closed out the Dish Structure TRR, SPF Band1 TRR and LMC TRR. The SE team has also been preparing and coordinating with the CDR meeting of SPF Band1 and LMC in the near future.

According to the updated schedule, a new ECP has been reported to SKAO for review, with most of the hardware having gone through the fabrication & assembly, shipment & clearance, RFI test and qualification tests during this period. Meanwhile, the schedule has been monitored and reported back to SKAO, with the Dish Consortium now preparing the cost for the next round update.

Finally the signing of the extension of Dish consortium agreement was completed in April with the Dish Consortium marching towards the CDR firmly and steadily.

Dish Structure

After the SKA prototype dish inauguration ceremony on 6th Feb, the dish structure team has been carrying on with the assembly of the two prototype dishes and verification in parallel. For the first SKA prototype dish, known as SKA-P, the mechanical alignment was completed in China in June. The photogrammetry measurement of the main reflector, sub-reflector surface accuracies and the positions between main reflector, sub-reflector and feed show promising results. The JLRAT team has been working further on SKA-P to support this verification including the antenna performance tests in Ku Band, Band A, and preliminary observation at L Band, shown in Figure 1.

Figure 1 Installation of L Band on SKA P for preliminary observation

The second SKA prototype dish, known as SKA-MPI, is fully funded by the Max Planck Society (MPG) and managed by MT Mechatronics. The SKA-MPI is being installed at the MeerKAT site in South Africa, adjoining the KAT-7 and MeerKAT core. After being handed over to the Dish AIV team, SKA-MPI will be fully integrated with SPF Band1 and Band2 packages for the Dish system level test and the verification for Dish CDR.

With the arrival of the SKA-MPI on site in June, the engineering teams from JLRAT and MTM have been working on the construction of the main structure, shown in Figure 2. The servo components were shipped to the Houwteq RFI test facility in South Africa by air and sea. Those components are now being tested as a whole servo system at Houwteq for RFI certification and then will be shipped to site for installation, as shown in Figure 3.

Figure 2 SKA-MPI construction on site

Figure 3 EMI testing of Servo system at Houwteq

The Indexer team has finished the integration verification and finalized the interface with the SPF package. The indexer main structure is on its way to South Africa, and the team has also been working on the EMI design of encoder IO unit. This had been shipped to MPG for RFI test and then was shipped to the site in South Africa.

Due to the strict RFI requirements of the SKA Dish and MeerKAT site, the dish structure team has completed an additional RFI TRR before the shipment of SKA-MPI. The modifications of EMI design and RFI tests within the components level were completed in Germany, China, Italy and South Africa.

The dish structure team is foreseen to meet again at the site in South Africa to finish the installation of SKA-MPI. Currently they have been working on the preparation of the dish structure TRR.

Meanwhile, SKAO has made the proposal to fund the holography test on SKA-P. The work is being led by the CSIRO engineering team and supported by JLRAT, to accelerate the verification process of Dish.

Local Monitor and Control

The LMC team has closed the LMC software and hardware TRR. So far the States and Modes documents have been updated to the 3rd version. Along with the software development, the manual and automated qualification tests are ongoing. The hardware is now available and the team is busy with the preparation of their CDR documents, to be submitted by the end of July.

Single Pixel Feed

SPF Band1

After closing out the TRR in March, The SPF Band1 team has been working on the two qualification models. The RFI and environmental test in Sweden was completed in June and the qualification test has been carrying on at the OSO. Another qualification model has been shipped to South Africa. After the successful RFI certification, the SPF Band1 was installed on MeerKAT Dish #21, as shown in Figure 4 and Figure 5. The SPF Band1 team has been working together with SPF Band2 team and on the SPF Band1 test and Band 1&2 integration. The SPF Band1 CDR has been scheduled in September, with the documentation and meeting preparations on track.

Figure 4 SPF Band1 B2B RFI testing

Figure 5 SPF Band1 mounting on the MeerKAT Dish #21

SPF Band2

The Band2 feed was successfully installed and tested on a MeerKAT dish in May. This was the first SKA SPF being tested on site and also the first SKA feed having a test jig during APR as shown in the Figure 6.

Figure 6 SPF Band2 mounting on the MeerKAT Dish #21

During the SPF Band2 MeerKAT integration test, a Band2 V-channel output power graph was produced, as is illustrated in Figure 7. The graph shows a number of frequency sweeps with the antenna pointed at the south celestial pole. The resolution bandwidth is 1MHz. The higher powered lines include 10% of Tsys calibration noise.

Figure 7 SPF Band2 on sky test V-channel output power

SPF Band5

The SPF Band5 delta PDR was successfully closed at the end of June. To close the delta PDR, SPF Band5 team has decided that; the Band5a and 5b feeds will be cooled to 70K; with the Turbo-pump RFI being measured, 80dB of shielding being required; and the baseline of cold-head will be the Oxford cryo-system 6/30. All these are documented in the updated PDR design document.

The assembly and test of thermal plumbing for prototype B345 has been completed, shown in Figure 8 and Figure 9. This will verify the thermal distribution system for the complete 5-feed system.

Figure 8 SPF Band 345 Bench tests on heater circuits

Figure 9 SPF Band 345 MLI around bus-bars1

CETC54 is working on the new Band5a and 5b OMTs, which will now include all the required mounting features for fixing into the cryostat. SPF Band5 team has started the electromagnetic modeling to verify window sizing following the feeds cooling design. The detailed design of cryostat qualification model has continued with the final decision of delta PDR, as shown in Figure 10 and Figure 11.

Figure 10 SPF Band345 Assembly in Cryostat

Figure 11 SPF Band345 20K cooling straps

Controller, Vacuum and Helium compressor

SPFC Tango issues were resolved after a visit by Lorenzo Pivetta (SKAO). The challenges resolved included memory leaks and unreliability of connections with feeds and test software (LMC interface). SPFC software was successfully utilized during the on-sky testing of the Band1 and Band2 feeds on the MeerKAT dish.

Since the findings of the Band2 and services CDR, testing with alternative vacuum pumps has been ongoing. In addition, design work continued on the helium service and the compressors which may be used. These included the baseline MeerKAT Trillium, SHI and OCS compressors, with a custom modified FA-40 compressor for qualification having been received, shown in Figure 12. The first examples of the new Oxford helium compressor have also been reviewed. The assembly with compressor control module from EMSS and the factory tests have also been completed. Two units have been delivered to Oxford University in June, as shown in Figure 13.

Figure 12 SHI Helium Compressor and parts

Figure 13 OCS Compressor

Receiver

Multiple components of Band123 have been undergoing redesign to address the coherence issue, requiring increased effort with more resources necessary to mitigate delays. An Assistant Project Manager and two additional team members have been added to SPF Receiver (SPFRx) team to refine project schedule and support the design.

SPFRx-CSP-SKAO coherence workshop held in Penticton revealed the need to deploy additional ADC devices dedicated to all sampling frequencies. FPGA platform changed from Xilinx Ultrascale board to Intel/Altera Talon board and it is recommended to address increased I/O needs.

The new design of Band 123 ADC board based on ADC12DJ3200/4000 to resolve the coherence issue has been finished, as shown in Figure 14. It has the advantages of half the physical size, reduced number of data lanes, reduced power consumption and a flatter frequency response. The Fabrication of the new Band 123 ADC board was completed in July and is waiting for functional testing, shown in Figure 15.

Figure 14 3D rendered image of the new ADC board we developed to resolve the coherence issue of B123

Figure 15 Finished printed circuit which is currently undergoing assembly by pick and place

The RXS123 mechanical update for the fabric-ability has been completed. The redesign of RXS123 is ongoing to hold two dual polarization ADC boards and associated support circuits, as shown in Figure 16.

Figure 16 Mechanical redesign of RXS123 indexer enclosure for holding two ADC boards as required to solve the coherency issue

The receiver team has finished the redesign of SCP Talon1 board for compatibility with SPFRX and the EMI data acquisition and processing software design for Ettus USRP. The integrated RF chain for bands123 has been fully tested, as shown in Figure 17

Figure 17 Finished and fully tested integrated RF chain for bands 123

The receiver team is now working on the FPGA firmware porting from Xilinx to Intel/Altera Talon platform and the SPFRx-LMC Tango software porting from BeagleBone SBC to Talon’s on board linux host. The progress of the designs have been collected during the preparation of SPFRx Band123 delta DDR2 documents.


Report provided by the DISH consortium