SPF SUB-ELEMENT QUALIFICATION PLANska-sdp.org/sites/default/files/attachments/ska...Document No.: Revision: Date: SKA-TEL-DSH-0000117 2A 2019-02-28 Author: I. P. Theron, et al. Page

Name Designation Affiliation Signature and Date

Compiled by:

I. P. Theron SPF Lead EMSS

Antennas

Approved by:

T. Küsel SE: Dish

Consortium SKA-SA

SPF SUB-ELEMENT QUALIFICATION PLAN

Document Number........................................................................ SKA-TEL-DSH-0000117 Revision ......................................................................................................................... 2A Author ................................................................................................... I. P. Theron, et al. Date ................................................................................................................. 2019-02-28 Status ......................................................................................................................... Draft

Document No.: Revision: Date:

SKA-TEL-DSH-0000117 2A 2019-02-28

Author: I. P. Theron, et al. Page 2 of 35

DOCUMENT HISTORY Revision Date of Issue Engineering Change

Number

Comments

A 2016-09-16 - First draft release for internal review

B 2016-09-30 - Draft released for DDR

1 2016-11-30 Released with DDR feedback

1A 2017-05-05 Draft prepared for band 1 delta DDR

1B 2017-06-09 Draft prepared for band 5 PDR

1C 2017-08-26 Draft prepared for internal review after incorporating

changes from band 1 delta DDR and updating to SPF

requirements revision 5.

2 2017-09-08 CN0036 Released for band 1 DDR closure

2A 2019-02-28 Draft prepared for Band 345 DDR

DOCUMENT SOFTWARE Package Version Filename

Wordprocessor MsWord Word 2016 SKA-TEL-DSH-0000117_Rev2A_SPFQualPlan.docx

Block diagrams

Other

ORGANISATION DETAILS Name SKA Organisation

Registered Address Jodrell Bank Observatory

Lower Withington

Macclesfield

Cheshire

SK11 9DL

United Kingdom

Registered in England & Wales

Company Number: 07881918

Fax. +44 (0)161 306 9600

Website www.skatelescope.org


SKA-TEL-DSH-0000117 2A 2019-02-28


TABLE OF CONTENTS

LIST OF ABBREVIATIONS ................................................................................. 5

1 INTRODUCTION........................................................................................ 6

1.1 Purpose of the Document ....................................................................................................... 6

1.2 Scope of the Document .......................................................................................................... 6

2 REFERENCES ............................................................................................. 7

2.1 Applicable Documents ............................................................................................................ 7

2.2 Reference Documents ............................................................................................................. 7

3 TERMINOLOGY ......................................................................................... 8

3.1 Verification .............................................................................................................................. 8

3.2 Qualification ............................................................................................................................ 8

3.3 Acceptance Verification .......................................................................................................... 8

4 SPF SUB-ELEMENT OVERVIEW .................................................................. 8

5 SPF SUB-ELEMENT DEVELOPMENT OVERVIEW ....................................... 11

6 SPF SUB-ELEMENT DEVELOPMENT AND QUALIFICATION PROCESS ......... 12

6.1 SPF Sub-Element Hardware Development and Testing ........................................................ 12

6.2 SPF Sub-Element Software Development and Testing ......................................................... 12

6.3 SPF Sub-Element Integration and Standalone Qualification................................................. 13

6.4 SPF Sub-Element Early Integration with Other Sub-Elements .............................................. 13

6.5 SPF Sub-Element Site Integration and Testing ...................................................................... 14

6.6 Implications of Cold Head Replacement ............................................................................... 14

7 SPF SUB-ELEMENT VERIFICATION REQUIREMENTS ................................. 15

7.1 Requirements, Verification and Qualification Events ........................................................... 15

7.2 Verification Requirements Description ................................................................................. 20

7.2.1 SPF.V1: Network Analyser Test .................................................................................... 20

7.2.2 SPF.V2: Noise Test ........................................................................................................ 20

7.2.3 SPF.V3: Linearity Test ................................................................................................... 21

7.2.4 SPF.V4: Gain Stability Test............................................................................................ 21

7.2.5 SPF.V5: Phase Stability Test ......................................................................................... 22

7.2.6 SPF.V6: Survival Levels Test ......................................................................................... 22

7.2.7 SPF.V7: Calibration Noise Stability Test ....................................................................... 22

7.2.8 SPF.V8: Calibration Noise Switching Test ..................................................................... 22

7.2.9 SPF.V9: CAM Test ......................................................................................................... 23

7.2.10 SPF.V10: Environmental Test ....................................................................................... 23

7.2.11 SPF.V11: Induced Vibration Test .................................................................................. 24


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7.2.12 SPF.V12: SPF RFI Test ................................................................................................... 24

7.2.13 SPF.V13: SPF Electrical Interface Test .......................................................................... 25

7.2.14 SPF.AV1: EM Beam Analysis ......................................................................................... 26

7.2.15 SPF.AV2: Pointing Error Analysis .................................................................................. 26

7.2.16 SPF.AV3: Coupler Tolerance Analysis ........................................................................... 26

7.2.17 SPF.AV4: RAM Analysis ................................................................................................ 26

7.2.18 SPF.AV5: Heat Analysis ................................................................................................. 26

8 SPF SUB-ELEMENT QUALIFICATION EVENTS ............................................ 27

8.1 Functional Qualification Event .............................................................................................. 27

8.2 Environmental Qualification Event ....................................................................................... 29

8.3 RFI Qualification Event .......................................................................................................... 31

8.4 Interface Qualification Event ................................................................................................ 31

8.5 Inspection and Demonstration Qualification Event .............................................................. 31

9 SPF SUB-ELEMENT TEST DOCUMENTATION ............................................ 32

10 SPF SUB-ELEMENT QUALIFICATION PROJECT PLAN .............................. 33

11 QUALIFICATION RISK MANAGEMENT .................................................. 35

LIST OF FIGURES

Figure 1: SPF context diagram. ............................................................................................................... 9

Figure 2: SPF sub-element PBS. ............................................................................................................ 10

Figure 3: SPF sub-element development diagram. ............................................................................... 11

Figure 4: Estimated current measurement sensitivity using a shielded anechoic chamber. ............... 25

Figure 5: Configuration of the band 1 network analyser tests. ............................................................ 28

Figure 6: Configuration of the band 2 noise and network analyser tests. ............................................ 29

Figure 7: Configuration for the band 1 thermal tests. .......................................................................... 30

Figure 8: Configuration for the band 2 thermal tests. .......................................................................... 30

LIST OF TABLES

Table 1: Allocation of requirements to be verified by testing .............................................................. 15

Table 2: Requirements requiring verification by analysis ..................................................................... 18

Table 3: Qualification events ................................................................................................................ 27

Table 4: Proposed test documentation ................................................................................................ 32

Table 5: Expected durations of qualification tasks ............................................................................... 33

Table 6: Major SPF qualification risks ................................................................................................... 35


SKA-TEL-DSH-0000117 2A 2019-02-28


LIST OF ABBREVIATIONS

CDR ............................... Critical Design Review

CoBL ............................. Concept Baseline

CoDR ............................. Concept Design Review

CSCI .............................. Computer Software Configuration Item

DBL ............................... Design Baseline

DDR ............................... Detail Design Review

DSH ............................... Dish Element

ECP ............................... Engineering Change Proposal

EM ................................. Electromagnetic

ICD ................................ Interface Control Document

LMC .............................. Local Monitoring and Control

LNA ............................... Low noise amplifier

OMT .............................. Ortho-mode transducer

PDR ............................... Preliminary Design Review

QBL ............................... Qualification Baseline

QTR ............................... Qualification Test Report

RFI ................................. Radio frequency interference

SKA ............................... Square Kilometre Array

SKAO ............................ SKA Project Office

SKADC .......................... SKA Dish Consortium

SDD ............................... Software Design Document

SPF ............................... Single Pixel Feeds

SPFC ............................. SPF Controller

SRS ............................... Software Requirement Specification


SKA-TEL-DSH-0000117 2A 2019-02-28


1 INTRODUCTION

1.1 Purpose of the Document

This document describes the qualification plan for the SPF sub-element. It should be noted that while this document describes the qualification plan that is be executed at some future date, this revision of this document has been updated after bands 1, 2 and the vacuum system has been qualified. More detail can be found in those qualification documents.

1.2 Scope of the Document

This document only covers the high-level qualification plans for the performance requirements of the SPF sub-element. This includes the feed packages as well as the services, namely the SPF controller, SPF vacuum services and SPF helium services.

Detailed qualification test procedures will be developed after the detail design review for each of the components. This plan describes the detail for full qualification, but some of the tests prescribed here may be replaced by verification due to similarity with MeerKAT. This will be done in conjunction with the DSH system engineers.

The SPF controller software will be updated as the requirements and state machines of each of the three SPF bands are finalised. This will thus be qualified in phases.


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2 REFERENCES

2.1 Applicable Documents

The following documents are applicable to the extent stated herein. In the event of conflict between the contents of the applicable documents and this document, the applicable documents shall take precedence.

[AD1] A. Peens-Hough, et. al., “Single Pixel Feed (SPF) Requirements Specification”, SKA-TEL-DSH-0000012, Rev 5, 2017-06-01.

[AD2] G. Smit, et. al., “Data Exchange Interface between the Dish LMC and SPF Controller”, SKA-TEL-DSH-0000055, Rev. 2, 2018-02-01.

2.2 Reference Documents

The following documents are referenced in this document. In the event of conflict between the contents of the referenced documents and this document, this document shall take precedence.

[RD1] Bhushan Billade, “SPF Band 1 Feed Package Development Specification”, SKA-TEL-DSH-0000081, Rev. 1, 2017-08-24.

[RD2] Jean Kotzé, et. al., “SPF Band 2 Feed Package Development Specification”, SKA-TEL-DSH-0000083, Rev. 1, 2016-11-30.

[RD3] P.C. van Niekerk, “Single Pixel Feed Controller Development Specification”, SKA-TEL-DSH-0000087, Rev. 2, 2018-08-10.

[RD4] A. Krebs, “Single Pixel Feed Helium Services Development Specification”, SKA-TEL-DSH-0000089, Rev. 1, 2016-11-30.

[RD5] L.D. McNally, “Single Pixel Feed Vacuum Services Development Specification”, SKA-TEL-DSH-0000091, Rev. 1, 2016-11-30.

[RD6] P.C. van Niekerk, “Single Pixel Feed Controller Software Requirements Specification”, SKA-TEL-DSH-0000104, Rev. 4, 2018-09-05.

[RD7] P.C. van Niekerk, “Single Pixel Feed Controller Software Design Document”, SKA-TEL-DSH-0000105, Rev. 4, 2018-10-12.

[RD8] R. Blatch, “DSH EMI Control Plan”, 301-000000-011, Rev. 1, 2016-02-20.

[RD9] G. Smit and G. J. van der Merwe, “Level 2 and Level 3 EMI/EMC Requirements for SKA1 Dish Related to SKA EMI/EMC Standard”, SKA-TEL-DSH-0000076, Rev 4, 2017-02-23.

[RD10] T. Küsel, “SKA1 dishes consortium system engineering management plan”, SKA-TEL.DSH.SE-NRF-MP-001, Rev. 1, 2013-06-05.

[RD11] P.C. van Niekerk, “SPF controller to SPF band 345 data exchange ICD”, SKA-TEL-DSH-0000095, Rev. 1, 2018-09-05.

[RD12] Gottlieb van der Merwe, “SKA1 Dish Qualification Model (SDQM) Integration and Verification Plan (I&VP)”, 301-000000-007, Rev 2 Draft.

[RD13] Andy Born, “SPF Band 345 Feed Package Development Specification”, SKA-TEL-DSH-0000085, Rev. 1, 2018-09-25.


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3 TERMINOLOGY

3.1 Verification

This is the process of confirming, through the provision of objective evidence, that specified requirements are fulfilled.

3.2 Qualification

Qualification is the process of verifying that a specific design definition (part number) fulfils all its requirements, typically by testing a pre-production model. In some instances, requirements for performance under extreme conditions cannot be verified by testing, and qualification and verification will be done by analysis. Qualification is required before commencing with production to ensure that the risk of producing non-compliant items is sufficiently low. A qualification programme is of particular importance if a large number of units will be produced with a long-expected service capability. Qualification testing is typically a comprehensive test of all specifications, including environmental testing. Due to the vigour of some of these tests, e.g. shock and vibration testing, qualification units may not be fit for use in the final system. The qualification tests should also ensure that the production process is sound, and that all subsequently produced items will also meet specifications. For this reason, a limited set of qualification tests may have to be repeated for the first few production items that are produced from the production line.

3.3 Acceptance Verification

Acceptance verification is performed on all production items to ensure that they are built according to the design, and that the quality of the production process is under control. Because the design is already qualified, the acceptance testing is typically a subset of the qualification tests.

4 SPF SUB-ELEMENT OVERVIEW

The SPF sub-element is primarily responsible for converting the EM signals focussed by the reflectors to RF signals that can be digitised. It must amplify these signals while adding minimal additional noise or RFI and allow injection of calibration noise signals. The frequency range is covered in six bands (bands 1, 2 ,3, 4, 5a and 5b) [AD1]. The entire band 1 feed package is at ambient temperature. The band 2 feed package uses an ambient temperature horn, and cryogenic OMT and LNAs. Bands 3, 4, 5a and 5b share a cryostat and are collectively referred to as the “band 345 feed package”. Both the band 5 feed horns will also be cooled. The band 345 cryostat also provides provision for a future, as yet not fully specified, band 6 feed. Since only band 5 (that is 5a and 5b) will be populated during the initial phase of SKA1, detailed qualification plans of the band 3, 4, and 6 feedhorns and RF chains are not presented here, although it is likely that they will require very similar procedures to those required for bands 5a and 5b, or band 2 if they make use of external ambient temperature horns with an accessible waveguide input port. Qualification plans for these bands will be provided once they reach DDR.

The feed packages are located on the dish structure feed indexer and are thus exposed to the ambient environment. Each feed package is covered with an individual environmental/sun shield – mostly to reduce solar heating, but also to provide some protection against direct rain.

The two cryogenic feed packages employ Gifford McMahon (GM) cryocoolers requiring high pressure helium. The SPF helium service consists of a single compressor mounted above the turnhead, a helium refill system, as well as supply and return lines to the distribution manifolds on the feed indexer. A future upgrade may allow control of the compressor speed and the speed of one or both cold heads to reduce the power consumption.


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The cryogenic components inside the cryostat are thermally insulated by high vacuum. A vacuum pump will be permanently installed on the indexer of each dish. The pump is only operational while cooling down a feed package; during operations, the vacuum is maintained by the cryo-pumping associated with the GM cryocooler. An additional turbo-pump is attached directly to the band 345 cryostat. This pump is only operational while cooling down the feed package.

The SPF controller is responsible for control and monitoring of the individual feed packages and the helium and vacuum systems, and to provide an interface to the local monitoring and control (LMC) sub-system. Is it located inside the RFI shielded cabinet inside the pedestal and uses slow serial communication over fibre with the different SPF components.

The SPF sub-element interfaces only with other components of the dish element, hence all external interfaces are internal to the SKADC. Figure 1 and Figure 2 show the SPF context diagram and SPF sub-element PBS respectively, and Figure 3 gives the SPF sub-element development diagram.

Figure 1: SPF context diagram.


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Figure 2: SPF sub-element PBS.


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5 SPF SUB-ELEMENT DEVELOPMENT OVERVIEW

Figure 3: SPF sub-element development diagram.

Preliminary Design Phase

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(SP

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Requirements Baseline

SPF

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(DSH

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SPF Req Spec Rev3(MAY16)

2014 2015 2016 2017

Concept Definition Preliminary Design

2018

Prototype Models

Concept Design Phase

STAGE 1 STAGE 2

Build Phase

Qualification Models (QM)

DSH CoDR (JUN14)

SPF Inputs CoDR

CoBL

Major Component Qualification Reports

Preliminary Design

Detailed Design, Specifications and ICDs

Build QMDetailed Design

Build QMDetailed Design

Internal Interface Test SW

External Interface Test SW (LMC Simulator)

B2 Software Dev,Qualify & Release

SPF DD Rev4SPF External ICDSPF Qual. Plan

DBL

Major Component DesignSPF Internal ICDsMajor Component Qualification Plans

QBL

Integration and Qualification testing of pre-production Dish

QTRManufacturing

Datapack

DSH CDR(TBD)

SPF B2

SPF Controller

SPF B1

SPF B345 (B5 populated)+ He system

Build QMDetailed Design, Specifications and ICDsSPF Vacuum

2019

Requirements Definition phase

DS PDR (APR16)

Detailed Design Phase

B1&B2 DDR (2-4NOV16)

Detailed Design Build QM

Build QM

Qualification Phase

Detailed Design for Band 2 Build QM (Temporary Compressor)SPF Helium (B2)

B2 CDR (2-4NOV17)

B1 CDR (18-19SEP18)

B5 CDR (?19)

Qualify

Qualify

Qualify

B5 Software Development, Qualify and Release

Qualify

B1 Software Dev,Qualify & Release

Qualify

B5 DDR(26-27MAR19)

DSH PDR (FEB16)

B1&B2 PDR (FEB16)

Detail Design

DSH pre-DDR (NOV18)

Qual. Procedures

Qual. Procedure


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6 SPF SUB-ELEMENT DEVELOPMENT AND QUALIFICATION PROCESS

6.1 SPF Sub-Element Hardware Development and Testing

The individual feed packages will be developed according to their specifications, i.e. [RD1] for band 1, [RD2] for band 2 and [RD13] for bands 3, 4, 5a and 5b. Although provision for a future band 6 feed is provided in the overall band 345 feed package design, a formal development specification for this band is not yet available. During qualification, all requirements will be verified according to detailed qualification test procedures that will be developed in cooperation with the dish element system engineering team after the detail design review. This document provides an overview of the performance tests that will be included in these detailed qualification test procedures. The service components are mostly COTS components and will be verified according to their specifications (SPF controller hardware [RD3]; helium [RD4]; and vacuum [RD5]) as indicated in this document.

6.2 SPF Sub-Element Software Development and Testing

The SPF sub-element has both application software development on the SPF controller (SPFC) and firmware development on the feed package controller and the helium compressor controller. The firmware development of feed packages is described in the respective design documents.

The SPFC software requirements are specified in the SPFC Software Requirement Specification [RD6]. The SPFC SRS details the functional and non-functional requirements of the SPFC CSCI. The software architecture is given and discussed in the SPFC software design document [RD7] on a functional level, identifying the software modules needed to accomplish the tasks of the SPFC SRS. The lower level software modules, e.g. software libraries or proprietary software modules, will not have formal documentation and the software source code will detail the design and serve as the documentation.

The low-level coding blocks will be developed in Linux by making use of the Eclipse IDE. The development language has been chosen to be C++, mainly due to its object-oriented capabilities. The standard Linux GCC compiler will be cross-compiled for the ARM platform and used to compile the source code. The Quantum Leaps QM graphic modelling tool will be used to define the state machines running in the SPFC CSCI. This generates C++ source code based on the graphical representation of state machines defines in it. The source code makes use of the Quantum Leaps QP framework to orchestrate state machine execution and communication between different state machines. No other tools are currently envisaged.

The code blocks of the SPFC CSCI will be tested as far as practically possible by means of unit testing. It is envisaged that software test simulators will be developed and matured during the different phases of development as needed, and where testing is the most critical.

Hardware integration will start at the very beginning of software development to ensure that fundamental software modules are stable on their intended hardware platform. The SPFC development environment is already established based on the MeerKAT work, which enables the early adoption of hardware integration. The SPFC will run on Linux on an ARM platform, and the hardware already exists, which enables basic software modules to be tested directly on the hardware platform. In the case where low-level detailed debugging is needed, a development board for the ARM architecture is available to perform low-level integration tests.

Integration tests will mainly consist of communication tests between the different subsystems. Software simulators will mostly be used to generate scenarios, monitor system parameters and control individual system functions. These tests will not be documented as they will be covered in the software test description for higher functional tests.

Higher system level functional tests will be performed by making use of a formal software test description. The results will be detailed in a software test report. The higher-level software tests will be aided by simulator hardware and software which will be detailed in the software test description.


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6.3 SPF Sub-Element Integration and Standalone Qualification

The stand-alone qualification of the SPF components will form the bulk of the qualification tests as minimal formal SPF level integration tests are required. The SPF controller is required to operate all the feed packages as well as the helium compressor and vacuum pump. It will therefore be informally integrated on a continuous basis. Similarly, the band 2 and band 345 feed packages need the helium compressor and vacuum pump for normal operation, so this integration will also be tested on a continuous basis. Since identical SPF controllers running the same operating software are used to operate the band 1, 2 and 345 feed packages, no combined integration of these are required before installation on the dish.

During on-dish operation, the noise diode is fired by the SPF receiver (via the optical fibre connector). Since the SPF receiver is not available during laboratory testing, the feed package controller can also directly turn the noise diode on, but on a much coarser time resolution.

To achieve optimum sensitivity for the noise and self-generated RFI measurements, the band 2 feed package will use a cold waveguide load as input. The band 1, 5a and 5b feeds will need to use cold sky for the noise measurement and accept that the self-generated RFI measurements will be less sensitive.

Qualification of the SPF components will require access to the following measurement facilities (see Section 8 for proposals of actual test facilities):

• Thermal chamber.

• Vibration table.

• Induced vibration analysis.

• Hail test facility (feed package radomes only).

• Shielded anechoic chamber and/or reverberation chamber.

EMI testing requires the use of custom spectrometer equipment, e.g. a real-time spectrum analyser and post-processing software. Test equipment will be kept in calibration. Custom test equipment will be verified from time to time. See Section 8 and Section 10 for more detail on the custom-built test equipment.

6.4 SPF Sub-Element Early Integration with Other Sub-Elements

The SPF sub-element has power and mechanical interfaces with the dish structure, RF signal and noise diode control interfaces with the SPF receiver, and a monitor and control interface with the LMC. Since the dish structures will only be complete on site, no early integration of the mechanical interfaces will be done. The power interfaces will be checked by measuring power levels and verifying connector types. The RF signal interfaces can only be tested on site as it is not practical to duplicate the cold sky input in a laboratory environment. The noise diode control interface will be verified by inspection of the data pack.

Partial laboratory-based RF signal chain events for each receive band are planned by DSH AIV. These will involve laboratory integration of a number of sub-elements (e.g. SPF, SPFRx and LMC depending on the band in question), as early risk reduction activities. These events [RD12] will be planned, co-ordinated and contracted by DSH AIV, but the SPF contractors will support the activities.

The interfaces with the LMC will be tested by running LMC software on the controlling PCs while doing stand-alone tests of the band 1, band 2 and band 345 feed packages. Thus there are three integration events: “band 1 & LMC integration”, “band 2 and LMC Integration” and “band 345 and LMC Integration”. These events would make use of feed package hardware simulators to exercise all the sensor combinations that the SPFC can report to the LMC as defined in [AD2].


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6.5 SPF Sub-Element Site Integration and Testing

Due to the sensitive nature of the SPF sub-element components, these should only be installed once the dish structure integration is complete. In addition, since the feed packages and helium compressor must be started from the LMC, the LMC and fibre network should be installed before the SPF components. The exception here is that the helium lines and vacuum pipes may be installed in parallel with the fibre installation. During installation, the LMC must provide either an operator or a port into the SPF controller to allow control of the SPF system. While not a requirement, it could help with sub-element site acceptance testing if the SPF receiver is available.

The installation should follow more or less the following sequence:

• Check that the dish structure, LMC and dish fibre network installations are completed.

• Install the helium lines and vacuum pipes. This step can be done in parallel with the first.

• Install the helium compressor and connect to the helium lines.

• Install the vacuum pump and connect to the vacuum pipes.

• Install the feed packages.

• Test that the LMC – SPF controller interface is functional.

• Cool down the band 2 feed package to cryogenic temperatures and verify that the cryostat sensors are nominal.

• Cool down the band 345 feed package to cryogenic temperatures and verify that the cryostat sensors are nominal.

• Measure the common mode currents as an indication of RFI issues due to installation errors. This step can be compromised by other RFI issues on site.

• Turn the noise diode on each feed package on and off. The output power can be measured with either the SPF receiver or a hand-held spectrum analyser. This test confirms that the RF signal path is still intact after transport to the Karoo.

• Additional measurements, such as system noise temperature, near-in beam patterns, calibration noise levels, etc. will be done during element integration. These tests do not form part of the SPF site acceptance.

A detailed installation manual will be compiled after integrating the SPF sub-element on the first SKA prototype dish.

6.6 Implications of Cold Head Replacement

The SKAO currently plans to negotiate the cryogenic supplier during the procurement process. The final cold head selection may be influenced more by fair return during procurement than technical merit. The band 2 design currently supports only the CoolStar 2/9 cold head and it will only be qualified for this unit. It would be relatively simple to modify the mechanical design to use the SHI 202 cold head. The valve drive motors on these two cold heads require quite different excitations, but this can be accommodated by changing PCBs and power components in the feed package controller. The band 345 cryostat currently supports only a Coolstar 6/30 cold head and will only be qualified for this unit. It is likely that significant re-design would be required if the cold head for this package was changed.

It should also be noted that changing either of the cold heads will materially affect the entire qualification. The noise performance, linearity and input/output match can be expected to be similar if the temperatures in the cryostat are similar and the RF survival is relatively independent of the cold head. All stability tests, mechanical / vibration tests, thermal cycles / soak tests, environmental tests and RFI measurements would need to be repeated.


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7 SPF SUB-ELEMENT VERIFICATION REQUIREMENTS

The method to be used to verify compliance to each of the requirements for the SPF Sub-Element is defined in the SPF sub-element requirements specification matrix [AD1]. Table 1 below lists the requirements to be tested during qualification, and assigns a high-level description, or “verification requirement” to each. Table 2 lists the requirements that will be verified by analysis. R.SPF.P.20 “SPF Band x frequency range” shall be considered to be satisfied if all performance requirements are met as explicitly tested at the specified frequency band edges as well as at frequencies nominally at the centres of the bands. The verification process is described in [RD10].

7.1 Requirements, Verification and Qualification Events

Table 1: Allocation of requirements to be verified by testing

# Requirement name Verification requirement1 Verification

Event1

Component

ID Name B1 B2 B345 SPFC He Vac

R.SPF.P.24 Intrinsic cross polarisation SPF.V1 SPF network analyser test (Uses SPF.AV1)2

QEx.1 x x x

R.SPF.P.1.1 SPF band 1 feed sensitivity SPF.V2 Noise test (Uses SPF.AV1) QE1.1, QE1.5 x

R.SPF.P.1.2 SPF band 2 feed sensitivity SPF.V2 Noise test (Uses SPF.AV1) QE2.1, QE2.5 x

R.SPF.P.1.3 SPF band 3 feed sensitivity SPF.V2 Noise test (Uses SPF.AV1) x

R.SPF.P.1.4 SPF band 4 feed sensitivity SPF.V2 Noise test (Uses SPF.AV1) x

R.SPF.P.1.5 SPF band 5a feed sensitivity SPF.V2 Noise test (Uses SPF.AV1) QE5a.1, QE5a.5 x

R.SPF.P.1.6 SPF band 5b feed sensitivity SPF.V2 Noise test (Uses SPF.AV1) QE5b.1, QE5b.5 x

R.SPF.P.3 Output power spectral flatness SPF.V1 Network analyser test (Uses SPF.AV1) Noise Test (For bands 5a, 5b)

QEx.1 x x x

R.SPF.P.4 Output return loss SPF.V1 Network analyser test QEx.1, QEx.5 x x x

R.SPF.P.5 Nominal input and gain SPF.V1 Network analyser test QEx.1, QEx.5 x x x

1 See Section 7.2 for the verification requirements and Section 8 for the list of qualification events 2 Some requirements will be qualified using both measurement and analysis. Verification requirements SPF.AVx refers to analysis.


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Event1

Component


R.SPF.P.6 Input 3rd order Intercept SPF.V3 Linearity test QEx.1 x x x

R.SPF.P.25 SPF Input 2nd Order Intercept SPF.V3 Linearity test QE1.1 x

R.SPF.P.8 Gain stability (fluctuations) SPF.V4 Gain stability test QEx.1 x x x

R.SPF.P.9 Phase stability p-p SPF.V5 Phase stability test QEx.1 x x x

R.SPF.P.10 Phase stability RMS SPF.V5 Phase stability test QEx.3 x x x

R.SPF.P.19.1 Survival input levels - band 1 SPF.V6 Survival levels test QE1.1 x

R.SPF.P.19.2 Survival input levels - band 2 SPF.V6 Survival levels test QE2.1 x

R.SPF.P.19.3 Survival input levels - band 3 - 5 SPF.V6 Survival levels test QE5a.1, QE5b.1 x

R.SPF.CIC.3 Noise Calibration level SPF.V2 Noise test QEx.1, QEx.5 x x x

R.SPF.P.16 Calibration noise stability SPF.V7 Calibration noise stability test QEx.1 x x x

R.SPF.P.18 Calibration noise switching response time SPF.V8 Calibration noise switching test QEx.1 x x x

R.SPF.CCC.1 SPF configure SPF.V9 CAM test QEs.7 x

R.SPF.M.1 SPF alarm information SPF.V9 CAM test QEs.7 x

R.SPF.M.2 SPF alarm latency SPF.V9 CAM test QEs.7 x

R.SPF.M.4 SPF capability reporting SPF.V9 CAM test QEs.7 x

R.SPF.M.5 SPF report alarms SPF.V9 CAM test QEs.7 x

R.SPF.M.6 SPF report events SPF.V9 CAM test QEs.7 x

R.SPF.M.7 SPF report failures SPF.V9 CAM test QEs.7 x

R.SPF.M.8 SPF report logs SPF.V9 CAM test QEs.7 x

R.SPF.M.9 SPF report predicted failures SPF.V9 CAM test QEs.7 x

R.SPF.M.10 SPF report sensors SPF.V9 CAM test QEs.7 x

R.SPF.M.11 SPF report states & modes SPF.V9 CAM test QEs.7 x

R.SPF.M.12 SPF report SW&FW versions SPF.V9 CAM test QEs.7 x

R.SPF.M.13 SPF reporting on missing components SPF.V9 CAM test QEs.7 x


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Event1

Component


R.SPF.M.14 SPF structure of reporting SPF.V9 CAM test QEs.7 x

R.SPF.M.15 SPF_LMC monitoring data rate SPF.V9 CAM test QEs.7 x

R.SPF.CCC.2 SPF configure LMC_SPF interface SPF.V9 CAM test QEs.7 x

R.SPF.CCC.3 SPF_LMC interface protocol SPF.V9 CAM test QEs.7 x

R.SPF.CCC.4 SPF_LMC interface self-description SPF.V9 CAM test QEs.7 x

R.SPF.CCC.5 SPF estimate power consumption SPF.V9 CAM test QEs.7 x

R.SPF.ED.2 SPF durability SPF.V10 Environmental test QEx.3 x x x x x x

R.SPF.ED.3 SPF endurance SPF.V10 Environmental test QEx.3 x x x x x x

R.SPF.ED.4 SPF operation SPF.V10 Environmental test QEx.3 x x x x x x

R.SPF.ED.5 SPF survival SPF.V10 Environmental test QEx.3 x x x x x x

R.SPF.ED.6 SPF induced vibration and shock SPF.V11 Induced vibration test QEx.2 x x x x x x

R.SPF.ED.7 SPF vibration and shock susceptibility SPF.V10 Environmental test QEx.2 x x x x x x

R.SPF.RFI.1 Maximum allowed radiation levels for SPF components on the indexer

SPF.V12 SPF RFI test QEx.4 x x x x

R.SPF.RFI.2 Maximum allowed radiation levels for SPF components on the turnhead

SPF.V12 SPF RFI test QEx.4 x

R.SPF.RFI.3 Maximum allowed radiation levels for SPF components inside the EMI Shielded Cabinet


R.SPF.RFI.4 Maximum allowed pulsed radiation levels for SPF components on the indexer

SPF.V12 SPF RFI test QEx.4 x x x x

R.SPF.RFI.5 Maximum allowed pulsed radiation levels for SPF components on the turnhead


R.SPF.RFI.7 Maximum allowed conducted EMI levels for SPF components

SPF.V12 SPF RFI test QEx.4 x x x

R.SPF.RFI.8 EMC standards to be used by SPF for Electromagnetic emissions and susceptibility


R.SPF.LPS.1 SPF galvanic connection - Equipment mounted on the indexer and turnhead

SPF.V13 SPF electrical interface test QEx.6 x x x x x


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Event1

Component


R.SPF.LPS.2 SPF galvanic connection - Equipment mounted inside the EMI shielded cabinet

SPF.V13 SPF electrical interface test QEx.6 x

R.SPF.PW.1 SPF power consumption SPF.V13 SPF electrical interface test QEx.6 x x x x x x

R.SPF.PW.3 SPF total harmonic distortion SPF.V13 SPF electrical interface test QEx.6 x x x x x x

R.SPF.PW.4 SPF phase imbalance SPF.V13 SPF electrical interface test QEx.6 x x x x x x

Table 2: Requirements requiring verification by analysis

# Requirement name Verification requirement Verification

Event

Component


R.M.P.6 SKA1-mid intrinsic cross polarization SPF.AV1 EM beam analysis x x x

R.SPF.P.1.1 SPF band 1 feed sensitivity SPF.AV1 EM beam analysis x





R.SPF.P.2.1 SPF band 1 variation of feed sensitivity SPF.AV1 EM beam analysis x




R.SPF.P.2.5 SPF band 5a variation of feed sensitivity SPF.AV1 EM beam analysis x

R.SPF.P.2.6 SPF band 5b variation of feed sensitivity SPF.AV1 EM beam analysis x

R.SPF.P.7 Beam smoothness SPF.AV1 EM beam analysis x x x

R.SPF.P.11 Far-out sidelobe extent SPF.AV1 EM beam analysis x x x

R.SPF.P.12 Far-out sidelobe peak SPF.AV1 EM beam analysis x x x


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# Requirement name Verification requirement Verification

Event

Component


R.SPF.P.13 Contribution to pointing error - degraded SPF.AV2 Pointing error analysis x x x

R.SPF.P.21 Contribution to pointing error - best SPF.AV2 Pointing error analysis x x x

R.SPF.CIC.1 Calibration noise phase imbalance SPF.AV3 Coupler tolerance analysis x x x

R.SPF.P.17 SPF calibration noise phase imbalance stability SPF.AV3 Coupler tolerance analysis x x x

R.SPF.LRA.1 SPF deployed Lifetime SPF.AV4 RAM analysis x x x x x x

R.SPF.LRA.2 SPF MMDT SPF.AV4 RAM analysis x x x x x x

R.SPF.LRA.3 SPF MTBM SPF.AV4 RAM analysis x x x x x x

R.SPF.LSE.3 SPF self-test SPF.AV4 RAM analysis x x x x x x

R.SPF.LSE.4 SPF test equipment calibration interval SPF.AV4 RAM analysis x x x x x x

R.SPF.LSF.1 SPF support facilities analysis SPF.AV4 RAM analysis x x x x x x

R.SPF.PW.5 SPF induced heat loads SPF.AV5 Heat/power analysis x


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7.2 Verification Requirements Description

7.2.1 SPF.V1: Network Analyser Test

For band 2 (and likely band 3), these tests will be done using custom waveguide adapters which are capable of connecting to the input of the feed package. These adapters will also be required for the linearity test, the gain and phase stability tests, as well as the survival input level test.

For band 1 the gain flatness and cross-polarisation will be measured in an anechoic chamber using a linear transmit antenna. This requires a linear input antenna and a mechanism to rotate it very accurately through 90°. The gain level will be measured for the RF chain before integrating it with the horn by injecting the signal directly into the LNA input port.

• Cross polarisation is measured by injecting the signal into the orthogonal port and measuring the transmission to the applicable output port. The signal path gain is removed by normalising the result with the transmission from the co-polarised input port.

For system cross-polarisation, the feed package coupling is added to the beam cross-polarisation as calculated in SPF.AV1.

• The transmission between the input and output ports will be measured using a network analyser. If applicable, the gain of the feed package will be obtained by de-embedding the contribution of the waveguide adapter.

The expected output power spectrum will be determined by multiplying the measured feed package gain with the system temperature calculated in SPF.AV1.

• The output return loss at the output ports will be measured directly using a network analyser.

For bands 5a and 5b (and likely bands 4 and 6), the cross-polarisation will be measured in an anechoic chamber using a linearly polarised transmit antenna which is capable of being rotated accurately in angle. A vector network analyser will be connected with one port on the transmit antenna and the other to the feed package RF output. These measurements of the feed cross-polarisation serve as input to the system cross-polarisation as calculated in SPF.AV1.

The RF gain and passband flatness will be measured using a vector network analyser connected directly to the LNA input port and the feed package RF output. This will require by-passing the OMT-to-LNA connector cable and using a spare cryostat RF feedthrough to introduce the input signal. The overall gain of the system will be obtained by de-embedding the contribution of the additional test cables.

The output return loss will be measured directly using a vector network analyser connected to the feed package RF output port.

7.2.2 SPF.V2: Noise Test

The feed package equivalent noise temperature is measured with the Y-factor technique using precisely calibrated “hot” and “cold” input levels. Depending on the band of operation, the loads may take different forms, e.g.

o Cold sky as “cold” load and an ambient temperature absorber as “hot” load.

o A cryogenically cooled waveguide to coaxial cable transition with an attenuator on the coaxial input to provide the “cold” load and a calibrated noise source to provide the “hot” load.

o Cryogenic and ambient temperature absorbers as “cold” and “hot” loads respectively.


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The feed package noise temperature is measured as follows:

• The feed package noise temperature is measured with the (feed package) noise diode off. Note that this is referenced to the hot/cold load reference plane.

The feed package noise temperature is then measured with the (feed package) noise diode on. The “noise diode off” noise temperature measured in the previous step is subtracted from this value to determine the (feed package) noise diode contribution. Note that using a waveguide load will slightly alter the ripple in this measurement. Hence, this provides accurate confirmation of the level of the noise, but will not provide a “gold standard” measurement that can be used on the dish.

The band 5a and 5b sensitivities will be measured using a hot/cold load (Y-factor) technique using cold sky as the “cold” load and room temperature absorber as the “hot” load. The feed package will be mounted outdoors with the feeds pointing to the zenith and the RF output connected to a spectrum analyser. This will require a support frame to hold the complete feed package in a vertical position. Frequency resolved power measurements will be taken with the feed both pointed at the sky and then blocked by ambient temperature absorber. The noise diode will be fired in both of the hot and cold states to provide additional calibration information. The spectrum analyser measurements in the cold state also serve as measurement of the output power spectral flatness.

In all cases, the system noise is determined by adding the feed package noise to the antenna temperature calculated in SPF.AV1. Since the noise performance is dominated by the LNA’s, the typical and worst-case performance shall be summarised with the qualification evidence.

7.2.3 SPF.V3: Linearity Test

The 3rd order intercept measurement will be performed by inputting two closely spaced (in frequency) CW signals of identical powers Pin into the input of the feed package. For bands 1, 5a, 5b (and likely bands 4 and 6), the signals will be injected directly into the LNAs in a signal chain level test. For band 2 (and likely 3), the signal will be injected with waveguide adapters.

o The frequencies are f1 and f2 and equally spaced about the nominal frequency f0.

o The SPF output power will be measured at frequencies 2f1 - f2, f1, f2 and 2f2 - f1 respectively.

o The third order intercept points 𝐼𝐼𝑃3 = 𝑃𝑖𝑛 +𝑃0−𝑃03

2 will be calculated for Po = Pout f1 & Po3 =

Pout 2f1-f2 and Po = Pout f2 & Po3 = Pout 2f2-f1.

o The above measurements will be performed over combinations of input power Pin and frequency f0.

For band 1 the 2nd order intercept measurement will be performed in a similar way.

7.2.4 SPF.V4: Gain Stability Test

For band 2 (and likely 3), a CW signal will be coupled into the feed package by means of the custom waveguide adapter. For band 1 the signal will be injected into the integrated coupler port on the LNA as the RF chain must be integrated with the horn to get representative thermal behaviour. For bands 5a and 5b (and likely 4 and 6) the signal will be injected via the noise injection port in the feedhorn.

o The feed package output power will be measured at the required sampling time intervals by means of, e.g. a spectrum analyser operating in zero-span mode.

o Calculate the sets of RMS values.

o The above measurements will be performed over combinations of input power and frequency.

o The measurements will be evaluated in a statistical sense.


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Since the short-term gain stability is dominated by the LNAs, the typical and worst-case performance shall be summarised with the qualification evidence.

Long term stability is assessed under SPF.V10: Environmental Test.

7.2.5 SPF.V5: Phase Stability Test

The transmission will be measured with a network analyser in the same configuration as for SPF.V4 above:

o For the absolute phase stability S21 versus frequency will be repeatedly measured at the required time intervals for the duration of the measurement. For each frequency point, the maximum peak-to-peak phase over the total measurement time will be calculated.

o For the RMS phase stability measurement, the required sample period may be too small to measure S21 over frequency. It will then be necessary to perform rapid, single-frequency S21 measurements over the measurement period, and the entire measurement will have to be repeated at multiple frequencies across the band. The RMS phase stability will be calculated at each frequency after removing a linear fit to the phase over the measurement period. The measurements will be evaluated in a statistical sense.

Long term stability is assessed under SPF.V10: Environmental Test.

7.2.6 SPF.V6: Survival Levels Test

The key performance characteristics, namely feed package input noise temperature and feed package gain will be measured before and after this test is carried out to ensure that these are not permanently degraded. During this period, the feed package power shall be cycled as little as possible. The required RF power level (for specified frequencies and durations) will be applied to the feed package input during normal operation, either by means of the custom waveguide adapter or the tests will be done on component level.

During this test, the output power will be monitored as an additional verification of R.SPF.P.22.

7.2.7 SPF.V7: Calibration Noise Stability Test

The temperature coefficient of the calibration source (including the noise diode, excitation circuit and coupling network) will be determined over a wide temperature range. A time series of physical temperatures of the calibration source will be recorded during the environmental test. The series of physical temperature as well as the temperature coefficients will be combined to calculate a series of output noise power points, from which the standard deviation can be calculated.

7.2.8 SPF.V8: Calibration Noise Switching Test

The noise source switching will be tested on component level only (and not after integration into the feed package). Note that only the switching is tested here whereas the noise level will be tested in the integrated system as part of the noise test in Section 7.2.2 (SPF.V2). In the short time intervals that must be measured to verify adherence to the jitter specification, the variation of the noise power is very large, even over the large detector bandwidth. For this reason, the noise source will be tested using the drive signal of the noise diode as a proxy for the noise power, as follows:


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o A low frequency (≈100 Hz) square wave is applied to the noise source via optical fibre as follows: signal generator – Cu to fibre convertor – optical fibre – fibre to Cu convertor – noise source circuit.

o For the noise module under test, the signal generator waveform and the load voltage are displayed on an oscilloscope. The load voltage is that over the current-limiting resistor/noise diode combination.

o The oscilloscope is triggered with respect to the switching waveform and the hold function used to display the spread of the load waveforms.

o The RMS jitter is estimated from the oscilloscope at approximately 50% of the maximum voltage level.

o The rise and fall times are also measured from the same oscilloscope trace. The 100% rise and fall times are measured since the 50% rise times require knowledge of the noise power versus voltage curve. This is a more stringent test than that using the 50% values.

7.2.9 SPF.V9: CAM Test

This test is applicable to the SPFC only, but it would need to be validated while connected to each of the three feed packages (band 1, band 2 and band 345). While connected to the band 2 or band 345 feed packages, it will also be connected to the helium and vacuum services. The SPFC will be connected to a PC running the qualified LMC software and using an LMC interface. The individual requirements will be verified by sending queries from the PC to the SPFC. Failures or missing components will be induced in the hardware of the feed package and/or associated vacuum and helium services.

7.2.10 SPF.V10: Environmental Test

For these tests, key performance characteristics, namely SPF input noise temperature and SPF gain will be measured at a nominal ambient temperature before and after these tests are carried out to ensure that these are not permanently degraded. The SPF components will remain powered on and active during the temperature cycles3 and all sensors monitored during normal operations shall be monitored and recorded.

• Durability and survival will be tested by exposing the SPF components to minimum and maximum temperatures for long enough to allow the component to reach equilibrium temperature.

• For all the other conditions, SPF equipment will (individually or together) be subjected to the relevant types of operating conditions (temperature only) while monitoring the signal path temperatures. The ranges of these temperatures will be used together with thermal coefficients of the individual components in order to determine whether the system will perform as appropriate for the conditions.

• Thermal coefficients of individual components will be determined either at component level, or from theory or published material.

• For the verification methods to be used for other non-temperature related environmental requirements, the verification will be done according to the standardised DSH environmental tests. Verification by analysis will be used wherever appropriate.

3 For the extreme low temperature soak, the electronics will be switched off as this is the worst case scenario.


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7.2.11 SPF.V11: Induced Vibration Test

The vibration of the feed package, vacuum pump or helium compressor will be validated by similarity to MeerKAT through measurement of similar type of equipment used by MeerKAT and mounted on a MeerKAT dish.

7.2.12 SPF.V12: SPF RFI Test

The radiated RFI tests will be performed in either a screened anechoic chamber – as was done for MeerKAT – or a reverberation chamber – which would be investigated. For spectral line RFI of components at the focus, it is impossible to reach the required sensitivity in a screened anechoic chamber – see below. Continuum RFI will be difficult to distinguish from background noise and drifts in receiver chain gain, unless the RFI is very large. The RFI measurement will thus be post-processed solely for spectral line RFI.

Measurement of pulsed RFI is likely to be problematic within a reverberation chamber due to smearing of the pulse transients over time and missing of pulses due to instantaneous position of the mode stirrers.

Due to the impracticality of testing for emissions up to 20 GHz, the maximum measurement frequency of an SPF component will be determined based on identification of signal frequencies observed with shielding enclosures open. This identification measurement will be performed with low sensitivity but over a wide band – to at least the maximum frequency of the band, five times the maximum frequency of any active components and such that there are no spikes in the top 2/3 of the frequency range.

It is not feasible to measure the shielding effectiveness of the small RFI shielding cavities used in the feed packages. However, it can be assumed that the shielding of these cavities will be at least as good as that of larger enclosures using the same filters and RFI gaskets. Thus, some of the SPF components may be measured in an “open” state and the 100 dB shielding effectiveness of typical large cavities with comparable RFI components used to determine the actual levels. This would allow validating the requirement, but components that fail this test may still be within specification as the shielding of the small cavities is likely to be better than that of a larger cavity. It would then, however, be very difficult to determine conclusively whether they achieve the specification or not.

Self-induced RFI testing will be conducted in-band only, with the feed package inside a screened environment and seeing a “cold” load, e.g. the cold load of the test fixture used to measure the noise. For bands 5a and 5b, a similar test will be conducted using a liquid nitrogen temperature cold load.

Figure 4 shows the sensitivity of the spectral line RFI measurements as done for the MeerKAT receiver (feed package in SKA terminology) – labelled “Current sensitivity” – relative to the SKA specification. This measurement used a 7σ detection on the difference spectrum (between adjacent frequency channels) to identify spectral line RFI and did not quite reach the MeerKAT requirement. It is, however, the best one can do in an anechoic chamber. In principle, one can integrate for longer to reduce the noise variation and thus the effective noise floor of the measurement, but then the systematic stability effects of the measurement equipment start to impact the measurement.


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Figure 4: Estimated current measurement sensitivity using a shielded anechoic chamber.

In this set-up, the frequency range of 50 MHz – 1.7 GHz is covered in three bands by separate receive antennas positioned in turn at 1 m from the part of the DUT which contains the RFI generating components. The antenna being used is followed by a (low cost) LNA with an input noise temperature of around 220 K. Since the chamber is already at 300 K, there is little to be gained by reducing this further. The measurement was done using a custom-built million-channel spectrometer with 810 Hz resolution bandwidth, using integration times of 300 s for the 50 – 200 MHz band, 5000 s for the 200 – 1000 MHz band, and 1000 – 1700 MHz band. The sensitivities shown above are for 7σ significance and isotropic radiation. They include the negative effects of using a wider (than 256 Hz) resolution bandwidth and of taking difference patterns, but exclude the (worst case 3 dB) effect of an RFI signal falling precisely between bins. The sensitivity can be improved by about 5 dB if the resolution bandwidth is reduced to 256 Hz, but such a system is not currently available. The sensitivity can be further improved by reducing the measurement bandwidth, provided it is still larger than the RFI bandwidth (which may be very narrow). The RFI bandwidth will be determined by measuring the system with the RFI shielding opened. It should also be noted that at this stage it is unknown what the measurement sensitivity in band 5 is likely to be – using a liquid nitrogen load (as opposed to a cryogenically cooled waveguide load) will increase the system temperature and reduce the sensitivity.

The possibility of performing this measurement in a reverberation chamber to improve sensitivity will be investigated. Finally, the dish consortium RFI requirements, standards and measurement techniques are currently being finalised. These will be incorporated into the final test procedures. As a starting point, the plan described above is broadly aligned with the provisions outlined in [RD8] and [RD9].

7.2.13 SPF.V13: SPF Electrical Interface Test

Galvanic connections between the chassis of the feed package / vacuum pump / helium compressor and a representative earthing strap will be measured using a (low impedance) resistance meter.

Measure power consumption and harmonic distortion during the temperature cycles of the SPF environmental test. SPF phase imbalance will be measured for the 3-phase SPF components, namely the vacuum pump and helium compressor.


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7.2.14 SPF.AV1: EM Beam Analysis

The two-dimensional dish pattern is determined as a function of frequency from EM analysis. For bands 1 and 2, this requires a full wave analysis. At these frequencies one can trust the simulation, especially when it comes to antenna beam patters. The losses can also be estimated to great accuracy. For the higher frequency bands, high frequency analysis may be used. This analysis shall employ the un-distorted nominal optics as defined for the SPF-EM interface and shall consider the positional tolerances defined in the SPF-DSH interfaces. The beam is used in a number of verification steps:

• The calculated cross-polarised components are used in SPF.V1 to determine the system cross-polarisation.

• The beam pattern is convolved with the surrounding brightness temperature (including both sky and ground temperatures) to determine the antenna noise as a function of elevation angle. This is added to the feed package noise contribution to determine the system temperature. In addition, the beam gain is used to determine the aperture efficiency. This can then be combined with the system temperature to determine the feed sensitivity. The feed sensitivity requirement is verified over the specified range of elevation angles.

• The second, variation in efficiency, requirement is verified by considering the feed over all elevation angles.

• The beam is rotated around the optical axis to determine the beam smoothness.

• The far-out side-lobes are determined directly from the beam patterns.

7.2.15 SPF.AV2: Pointing Error Analysis

The maximum allowed feed offset is determined by calculating the beam pointing error from an EM analysis with the feed in an offset position.

The deformation of the feed and mount must then be shown by FEM and thermal analysis to remain within these limits under the load cases for the appropriate environmental conditions.

7.2.16 SPF.AV3: Coupler Tolerance Analysis

Determine the maximum phase imbalance of the calibration noise by analysis of the possible path length variations and EM modelling of the coupler. Also determine the maximum this could vary over time / temperature.

7.2.17 SPF.AV4: RAM Analysis

An FMECA analysis will be executed on all applicable SPF components.

7.2.18 SPF.AV5: Heat Analysis

Determine the maximum heat loads by analysis using the measurements from SPF.V13 for the SPFC.


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8 SPF SUB-ELEMENT QUALIFICATION EVENTS

The qualification events (see Table 3) are named QE1.x for the band 1 tests, QE2.x for the band 2 tests, QE5.x for tests at the band 345 feed package level and QE5a.x and QE5b.x for tests specific to the individual bands. QEs.x indicates services tests. Note that no performance events are allocated to the services components – these will be implicitly included in the performance tests of the feed packages.

Table 3: Qualification events

Qualification event Band 1 Band 2 Band 5 Services

Baseline performance tests QE1.1 QE2.1 QE5a.1 QE5b.1

Vibration tests (transport conditions) QE1.2 QE2.2 QE5.2 QEs.2

Thermal chamber tests (survival as well as operational) QE1.3 QE2.3 QE5.3 QEs.3

RFI tests QE1.4 QE2.4 QE5.4 QEs.4

Repeated performance tests QE1.5 QE2.5 QE5a.5 QE5b.5

Mechanical and electrical interface tests QE1.6 QE2.6 QE5.6 QEs.6

CAM interface test QEs.7

Inspection and demonstration tests QE1.8 QE2.8 QE5.8 QEs.8

8.1 Functional Qualification Event

The SPF feed package qualification testing will be broken up into the following phases, in order of execution:

• Initial qualification tests, including feed package critical performance tests – QE1.1, QE2.1, QE5a.1, QE5b.1.

• RF survivability tests – part of QE1.1, QE2.1, QE5a.1, QE5b.1 but after the performance baseline.

• Remaining qualification tests including the feed package critical performance tests repeated after survivability testing – QE1.5, QE2.5, QE5a.5, QE5b.5.

Feed package critical performance tests are those that must be performed to verify that the feed package meets its critical performance requirements. These tests are performed prior to the survivability tests and have to be repeated subsequent to the survivability tests to ensure that there has been no permanent degradation of feed package performance. They comprise the SPF noise test and the SPF network analyser test (but exclude the 3rd order intercept point).

Survivability tests are the set of imposed conditions which must be survived without causing permanent performance degradation. These are the SPF survival input (RF) levels included here and the exposure to temperature extremes and vibration (SPF environmental tests).

The vacuum pump performance will have to be verified by pumping down an SPF or similar volume under the appropriate temperature extremes. The helium compressor will be qualified based on its specified operational temperature and on tests in which the ventilation vents are partially blocked to increase the temperature of the air flowing to the heat exchangers.


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For the band 1 feed, the required special test equipment includes a pure polarised precision rotatable transmit antenna for cross polarisation measurement and hot load for the stability tests. The receiver noise of band 1 will be measured on a MeerKAT antenna using sky as cold load and absorber placed in front of the horn as ambient load. This implies that band 1 qualification can only be completed after shipping the feed to South Africa. For the band 2 feed, the required special test equipment includes a custom cryogenic noise test fixture for noise measurements and a custom waveguide adaptor for network analyser, stability, RF survival and linearity measurements. For the band 5a and 5b noise measurements the special equipment required is a support frame to hold the feed package in a vertical position outdoors (this test will be done on the roof of the Oxford Physics building). For the cross-polarisation tests a standard anechoic chamber test facility with a transmit antenna covering the band 5 frequencies is required. The standard test configurations for the noise performance tests are shown in Figure 5 (band 1) and Figure 6 (band 2).

SPF Controller

Feed package controller

Ambient load

RF measurement equipment

Feed package Under test

RFI shielded tent

Temperature monitor

Computer with control and

measurement software

Fibre

RF cables

Figure 5: Configuration of the band 1 network analyser tests.


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Figure 6: Configuration of the band 2 noise and network analyser tests.

8.2 Environmental Qualification Event

For band 2 and services the vibration requirements – QE2.2 and QEs.2 – will be done based on similarity with MeerKAT. All thermal tests will be done in the Rheinmetall-Denel Munitions (RDM) thermal chamber – QE2.3 and QEs.3. The band 1 tests will both be done at RUAG in Sweden – QE1.2 and QE1.3. The band 345 feed package tests – QE5.2 and QE5.3 – will be done using facilities at Oxford Physics and STFC labs. Special test equipment includes a shaker table, vibration measurement equipment and a thermal chamber. The test configuration for the thermal tests is shown in Figure 7 (band 1) and Figure 8 (band 2). RF performance tests will be performed before and after these environmental tests to ensure that there is no degradation in performance.

The thermal tests include soaking the equipment at maximum storage conditions temperature in the off state for survival testing as well as exposing it to the prescribed rate of temperature change while monitoring the platform temperatures. The RF stabilities will be calculated afterwards by combining the measured temperatures of the active platforms with the temperature coefficients of the components. For the storage tests the equipment should be packaged, but it can be assumed that the conditions could last long enough for the package to reach thermal equilibrium hence the tests are done on the unpackaged components. Vibration survival tests are done on the packaged equipment.


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Figure 7: Configuration for the band 1 thermal tests.

Figure 8: Configuration for the band 2 thermal tests.

SPF Controller

Feed package controller

Ambient load

RF measurement equipment

Feed package Under test

Thermal Chamber

Temperature monitor

Computer with control and

measurement software

Fibre

RF cables


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8.3 RFI Qualification Event

The radiated RFI tests (continuous and pulsed) of the band 2 feed package and services components will be carried out in the SKA-SA Pinelands reverberation chamber and/or the SANSA shielded anechoic chamber – QE2.4 and QEs.4. The band 1 and 345 feed package RFI tests will be done in similar facilities at RUAG in Sweden and Oxford Physics respectively – QE1.4 and QE5.4. The currently available equipment might limit the accuracy of these tests, in which case the feed packages will be shipped to South Africa and tested together with the band 2 feed package.

To save time, as many of the SPF devices as is practical will be measured together. This likely to be possible with the EMI culprits on the indexer as well as the EMI culprits on the turnhead or pedestal since their permissible radiation levels are similar. It is likely that the SPF controller will need to be measured separately since it has much higher permissible radiation levels.

The dish integration will take place on the MeerKAT site and all SPF components and installation equipment need to adhere to the MeerKAT site RFI policy. Radiated RFI tests of the SPF components will include both the qualification tests as well as the standard SKA-SA tests required to verify conformance to the SARAS regulations. For on-site installation/testing, the only powered equipment required is the high lift platforms/cranes, dish LMC, SPF receivers and a hand-held spectrum analyser. It should be possible to use approved lifting equipment and spectrum analyser models.

The conducted EMI tests will be carried out in a screened environment as described in Section 7.2.12. Special test equipment includes a real-time spectrum analyser and associated analysis software.

An independent third party shall be identified to ensure the RFI Qualification Events are performed to the best possible level. The SKA-SA RFI team has been provisionally identified for this role.

8.4 Interface Qualification Event

The interface qualification event is done after completing all other tests as some of the test outcomes may require minor rework of the data pack. First – QE1.6, QE2.6, QE5.6 and QEs.6 – all mechanical and electrical interfaces will be verified by inspection of the equipment and the data pack.

In addition, the interface between the SPFC and LMC will be demonstrated – QEs.7 – by connecting the SPFC to a PC running the qualified LMC software and to mechanical simulators that can mimic all the sensor values returned from the feed packages. The LMC GUI will then be used to monitor and control the SPFC while setting the values on the feed package simulators. This test will test the complete LMC SPFC interface.

8.5 Inspection and Demonstration Qualification Event

This event – QE1.8, QE2.8, QE5.8 and QEs.8 – will include all requirements that are to be validated by inspection of either the manufactured hardware or supplier documentation or a combination thereof. Where applicable, inspection certificates will be provided. This will be the final event as it requires the completed data packs.


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9 SPF SUB-ELEMENT TEST DOCUMENTATION

Table 4 lists the test procedures and reports for the major SPF components. Each of these reports may reference LRU level documents.

Table 4: Proposed test documentation

Major Component Proposed document

SPF band 1 SPF Band 1 Qualification Test Procedure

SPF Band 1 Qualification Test Report





SPF controller SPF Controller Qualification Test Procedure

SPF Controller Qualification Test Report

SPF helium services SPF Helium Services Qualification Test Procedure

SPF Helium Services Qualification Test Report

SPF vacuum services SPF Vacuum Services Qualification Test Procedure

SPF Vacuum Services Qualification Test Report


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10 SPF SUB-ELEMENT QUALIFICATION PROJECT PLAN

Table 5 lists the expected durations of the different SPF qualification tasks. A project plan based on these estimates will be compiled later. Note that the qualification test procedures can be developed in parallel with the manufacturing of the prototypes, and that manufacturing of dedicated test equipment can start once the basic test requirements are determined. Note also that some of the hardware tests, e.g. RFI qualification of the vacuum system and feed packages can be done together or separately.

The final development of the test equipment can only be done after the basic test procedures have been agreed. The services tests will mostly be done in conjunction with the band 2 tests.

Table 5: Expected durations of qualification tasks

Task Duration (weeks)

Time

(man days)

Test procedure development

Band 1 test procedure 10 60



Services test procedure 2 10

Development of band 2 test equipment

Waveguide to coaxial cable transition EM design 10 30

Waveguide to coaxial cable transition and cold load cryostat mechanical design

5 25

Waveguide adapter and cold load manufacturing and calibration 16 40

Test control software 10 48

Band 1 qualification tests

Pre-endurance performance tests 2 20

Vibration tests 1 3

Temperature cycling 3 24

Hail test (horn radome only) 1 3

Post-endurance performance tests 1 10



Vibration tests 1 3




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Task Duration (weeks)

Time

(man days)



Vibration tests 1 3


Hail test (horn radome only) 1 3


RFI tests

Develop RFI test procedure and obtain measurement equipment 2 10

Radiated RFI tests in a reverb chamber 2 15

Pulsed RFI testing in an anechoic chamber 1 10

Self-generated RFI tests (separately for each band) 1 5

Reports

Data analysis and documentation of the band 1 qualification 5 50



Document the services qualification 2 20


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11 QUALIFICATION RISK MANAGEMENT

The risks in the SPF system are more related to schedule and resources than performance. Hence there are not many risks that require early testing. Table 6 lists the major risks regarding SPF qualification.

Table 6: Major SPF qualification risks

Risk Description Mitigation

Band 1 noise

Ambient band 1 system noise may not be as expected.

Do early measurements on a prototype feed as well as tipping curve measurements on DVA-1.

Update after DDR: These tests showed very good correlation (within 1 K in the absence of RFI) with the predicted values. Thus this risk is now sufficiently low.

Band 2 waveguide load

Initial expectation was to use an OMT with coaxial loads submerged in liquid nitrogen as waveguide load and defer the cryostat waveguide load development to production. More detailed planning has indicated that this would compromise both the self-generated RFI measurement sensitivity and the receiver noise accuracy.

Try to obtain resources to develop the cryostat waveguide load now.

Update after DDR: Resources are not available now, but very sensitive tests can be done over a part of the band using the MeerKAT cryostat load.

Band 2 cold head

The SKAO has create a “cryogenic systems” work package that is supposed to go out on open tender during procurement. Switching cold heads would, however, render all thermal, shock and vibration tests invalid. This affects the majority of the band 2 qualification.

Is it possible to make the cold head selection before qualification? This is complicated by the fact that the selection is likely to be a political procurement issue more than a technical selection.

Post DDR update: The cost of re-qualification will be part of the procurement cost and thus factored into account.

Band 345 cold head

The SKAO has create a “cryogenic systems” work package that is supposed to go out on open tender during procurement. Switching cold heads would, however, render all thermal, shock and vibration tests invalid. This affects the majority of the band 345 qualification and will require significant re-design of the cryostat design.

If open tender results in a change of cryogenic supplier, the cost of re-design of the Band 345 feed package and re-qualification would need to be part of the procurement cost and thus factored into account.