DVA Series Work Flow P. Dewdney Apr 15, 2010

SPDO DVP Work Flow 2 DVA-1 CPG

SPDO Highest affordable quality: Use best judgement for antenna requirements for which system performance can meet science requirements, when combined with Calibration and Imaging procedures. Includes capability for utilizing all the expected feed packages. Cost projects at the design/specification stage. Example specifications: –Maintainability, Reliability, Manufacturability, Power consumption –RFI protection –Monitor and control facilities –Survivability and longevity –Thermal control of equipment and thermal stability of structure –Calibratrability. These specifications are expected to evolve through the DVA series. –It is very important to get close and consider all of the above the first time. Once the antenna requirements are set, they can be used in acceptance tests for each DVA (in particular DVA-1). Estimate Key Antenna Specifications 3

SPDO After specifications have been set for the prototype antenna, it is constructed according to a prototype construction plan –In the case of DVA-1, the DVA-1 consortium construction plan. –For later prototypes, it is likely to be a specific SKA organization. –Potential industrial involvement for DVA-1. –Almost certain industrial involvement for subsequent members of the series. Subsequent members of the series are expected converge to a production design. Large changes in the design will prevent this convergence. –Fresh start would have to occur. Very important to prepare and preserve all the design and development documentation for each step, so that requirements traceability is maintained. –Including projection of fabrication in larger numbers. Cost projects and tracking. –Critical aspect. Prototype Antenna Construction 4

SPDO DVP Work Flow 5

SPDO Start with formal Acceptance Tests for the prototype in question (e.g. DVA-1). –Verify that the antenna meets the original specifications, would could be in a contract to a commercial organization. Carry out additional tests that can be done with a single antenna or potentially an interferometer for holography measurements. –See presentation on testing. –Antenna will have to be equipped with feeds and receivers.  Type of feed and receiver system will be dependent on level of testing at this stage.  e.g. A “simple” feed and RF system may suffice initially. (not what might be needed for deep testing). First Level Qualification Tests 6

SPDO Start the development of a model that can represent antenna performance as a component of the system. –Parameterized model in which parameters can be derived from observations and/or other data. Model based on a combination of design information and/or observed behaviour of the antenna during testing. –Could be a simple model (e.g. Pointing and rough beamshape), or it could be more complex. Developed in such a way that system simulations can be done to verify as much as possible that the antenna performance is sufficient to achieve system specifications. Question: Can the modelling be done well enough? Develop Performance Model 7

SPDO Antenna has been accepted and the first cut at understanding its behaviour, using first-level tests has been done. Testing continues at a deeper level, starting with a continuation of single dish testing and holography. –See next slide for examples. If it is possible to fully characterize the performance of the dish using these tests, Deep Verification Tests 8

SPDO Primarily a task for calibration and imaging groups, working in close contact with the group actually carrying on the tests. It is expected that this work starts soon after the first antenna models have been put together. The goal is to simulate the performance of the antenna system in an array situation, given the need to solve for dish performance parameters as they change on their “characteristic time scales”. –Examples: –Beam shape stability, including the first few sidelobes (direction dependent complex gains), –Potential effects from far-out sidelobes, –Beam rotation. –Frequency dependent effects in the beam and scattering. This will depend both on the characteristics of the dish optics and on the feed(s). In the modelling it should (may) be possible to separate the effects of the feed and the dish optics. An important question is to determine the optimum processed FoV. System Performance Analysis 9

SPDO DVP Work Flow 10

SPDO Have all the performance requirements been met? Have all of the environmental, field, and other requirements been met? Are all of the requirements traceable through documentation? Are the expected production costs well understood and acceptable? Is there a fully developed Data Package ready for procurement? If not, go around the loop to take appropriate action. Caveat: –There is no claim that we can “prove” that the SKA system can meet all the performance specs (esp. continuum imaging dynamic range), using tests and models as outlined. –In entering a new regime of sensitivity, it is important to be able to characterize the performance of the entire system as much as possible. The antennas and other analog systems are the main performance-determining hardware. OK? 11

SPDO Adjustments to the model –Upon analysis of the data, it is likely that new insights into drivers of the dish behaviour are found and these can be incorporated into the model. Antenna modifications –Improvements may be made by adjustments, replacement of parts, or other changes that do require re-building the dish. –These could be for a variety of reasons, such as changes to make the dish less expensive to manufacture, to maintain, etc. or to improve performance. –Once these changes are made, the dish performance is checked again. New Prototype Design –Once all possible information has been obtained from DVA-1, changes may be (are likely to be) required that mean a new prototype dish is needed, which would be the second in the convergent series. –A start on fabricating DVA-2 should be possible before testing of DVA-1 is complete. –It would be useful to involve industry at this stage, and ensure that all the information needed to provide a contract-ready data-pack is available for this prototype. Additional Iterations 12

SPDO It looks as though the DVA-1 program can produce an antenna that has passed its qualification tests, and carry out first level model development. –To be determined as part of these discussions. CPG: –It should be possible to make considerable progress in setting up a framework for performance simulation. What can we hope to accomplish with DVA-1. 13

SPDO Time Scale 14 Review dates are preliminary. Need to rationalize the work flow and reviews (TBD).

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SPDO Time Scale 16

SPDO Descriptions of competing technologies and statements and justifications of the candidate options to be carried forward First draft requirement specification Context diagram identifying all relevant interfaces (internal and external) First risk register and related mitigation strategies First draft block diagram of the relevant system, element or subsystem First draft requirements traceability matrix/database Strategy and plans for proceeding to the next phase First draft cost, schedule, power estimates Conceptual Design Review 17

SPDO Justification of the selected baseline option to be carried forward Finalised requirement specification First draft interface control documents (internal and external) First draft of the architectural design description document First draft acceptance test plan/procedure Updated risk register and related mitigation strategies Updated requirements traceability matrix/database Strategy and plans for proceeding to the next phase Updated Cost, schedule, power estimates System Requirements Review 18