REQUIREMENTS TRACEABILITY

Transcription

1 REQUIREMETS TRACEABILIT Document number... WP R-001 Revision... B Author... K. Cloete Date Status... Approved for release ame Designation Affiliation Date Signature Submitted by: K. Cloete System Engineer SPDO Co Authors and contributors:. Roddis, D. Hall, B. Adams, G. Hovey, D. Liebenberg, J. Jonas Approved for release as part of SKA System CoDR documents: P. Dewdney Project Engineer SPDO

2 DOCUMET HISTOR Revision Date Of Issue Engineering Change umber Comments A First draft release for internal review B Minor text and grammar changes following review. Approved for release as part of system CoDR documents. DOCUMET SOFTWARE Package Version Filename Wordprocessor MsWord Word 2007 WP R-001-B_ReqTrace TABLE OF COTETS 1 TRACIG OF REQUIREMETS Introduction Way Forward... 3 LIST OF ABBREVIATIOS SKA... Square Kilometre Array SPDO... SKA Program Development Office Page 2 of 9

3 1 Tracing of Requirements 1.1 Introduction To ensure that all the requirements collected from stakeholders and other sources have been captured and been translated into technical requirements, the requirements have to be traced back to the source. To accomplish this, a variety of tools and techniques have been developed. However, to illustrate the principle a manual process has been followed in tracing the science requirements from the SKA System Requirements Specification (document WP SRS-001) to the Design Reference Mission (v0.4). The result is shown in the table below. Ideally all the requirements in the System Requirements Specification must be traceable to a particular source whether it is a table, a document, minutes, or other sources. Due to the fact that the work on capturing the entire spectrum of requirements, including the in depth analysis of the Design Reference Mission, is still in progress, the System Requirements Specification is not complete and it is therefore not expected that all the requirements will be traceable. This can clearly be seen in the table with quite a few requirements not being traceable to a source. It must be re-iterated that the table is presented to establish and illustrate the principle of requirements traceability. The in-depth review and sign-off of the requirements traceability matrix will be done at the next system design review, the System Requirements Review. 1.2 Way Forward Requirements traceability provides a very clear view of the source of requirements. What it does not show is whether the sources are complete and whether the analysis of the information and data within these sources are complete. This is the subject of one of the tasks within the next system phase of the project and it is expected that the number and detail of requirements will grow significantly. At this point the table shows only one level of traceability. As the project moves forward the levels will be extended with requirements being traced from the Design Reference Mission, to the System Requirement Specification, to the element level Requirement Specification etc. It will therefore become quite complex and the utilisation of a dedicated requirements traceability tool will be considered. It will be expected that requirements traceability will be performed at each level of the project. Eventually all the levels will be combined to provide a comprehensive picture and overview of requirements and their origins. Changes to requirements will also be tracked to ensure traceability back to reasons and motivations for these changes Page 3 of 9

4 SS_REQ_1: Electromagnetic frequency range. SKA shall be able to measure electromagnetic radiation in a frequency range from 70 MHz to 10 GHz. C2p4.4 C3p4.1 C4p4.3 C5p4.3 C6p4.3 C7p4.1 C8p4.1 C9p4.1 C10p4.1.2 C10p4.2.2 C11p4.1 C12p4.1 C13p4.1.2 C13p4.2.3 C15p4.3 Frequency Frequency Frequency Frequency GHz GHz GHz GHz GHz GHz GHz 3 10 GHz 1 3 GHz GHz GHz GHz GHz GHz GHz SS_REQ_2: Instantaneous bandwidth. SKA shall have an instantaneous bandwidth, cf. Figure 3, of: 500 MHz for the range 70 MHz 600 MHz (TBV) C4p4 Instantaneous band width 500 MHz C5p4.4 Bandwidth 500 MHz 1 GHz for the range 600 MHz 10 GHz (TBV) C10p4 Frequency bandwidth > 500 Mhz Fractional instantaneous bandwidth: 1 C1p4.1 Fractional Instantaneous Bandwidth SS_REQ_3: Frequency band positioning. It shall be possible to position this band anywhere within the operating frequency band, with a positioning accuracy as specified in SS_REQ_29, 30, 31. The instantaneous observable frequency band is a contiguous band selected from the total frequency range. SS_REQ_4: Band selection resolution. The resolution with which the 500 MHz and 1 GHz bands can be selected shall be TBD or less. ~ Page 4 of 9

5 SS_REQ_5: Polarization frequency equality. It shall not be possible to select different digitized bands for the two polarizations of a single dish/antenna/array. SS_REQ_6: Sub-band bandwidth. The sub-band bandwidth after station level beamforming shall be less than TBD Hz. SS_REQ_7: DSP signal processing capacity. The digital processing capacity shall be sufficient to process all sub-bands (Q: and beams, and polarizations, or should there be exchangeability). SS_REQ_8: Beam sub-band and channel phase relations. The phase relations between the sub-bands and channels within a beam shall be known to such a level that wider bands and corresponding time series can be reconstructed from sub-bands and/or channels. SS_REQ_9: Spectral resolution. SKA shall offer a spectral resolution in each polarization for science processing of (cf. Figure 4) 2 khz to 100 khz in the band 70 MHz 300 MHz (TBV) 2 khz to 2 MHz in the band 300 MHz 3 GHz (TBV) 50 and 100 khz in the band 3 10 GHz (TBV) SS_REQ_10: Sub-band and channel phase relations. The signal processing performed on each sub-band shall leave the relative phases of sub-bands and spectral channels intact or predictable. C1p4.4 Spectral Resolution Sufficient to mitigate bandwidth smearing SS_REQ_11: Spectral dynamic range. SKA shall have a spectral dynamic range of [1]: 38 db in the band 150 MHz 450 MHz (TBV) C11p4.3 Spectral dynamic range 38 db 62 db in the band 450 MHz 1.4 GHz (TBV) C7p4.5 Spectral dynamic range 62 (54+8) db Page 5 of 9

6 SS_REQ_12: Sensitivity. The SKA shall have a sensitivity of (cf. Figure 5): in the frequency range 70 MHz - 3 GHz (TBV) C6p4.1 C7p4.2 C8p4.2 C10p4.1.1 C13p4.1.1 C13p4.2.2 Aeff/Tsys Aeff/Tsys Aeff/Tsys Aeff/Tsys Aeff /Tsys Aeff /Tsys > > > 2000 > 5000 > in the frequency range 3-10 GHz (TBV) C3p4.3 Sensitivity > 4000 SS_REQ_13: Survey speed. The SKA survey speed requirement is (cf. Figure 6): o requirement for the range MHz (TBV) C9p4.2 Aeff /Tsys (at 10 GHz) > E8 for the frequency range MHz (TBV) C11p4.4 Survey Speed ~ E8 for the range MHz- (TBV) C4p4.2 Survey speed E10 for the range 460 MHz 1.4 GHz (TBV) C11p4.4 C12p4.2 Survey Speed Survey speed ~ > E8 for the range GHz (TBV) C2p4.3 C5p4.2 C4p4.2 Survey speed Survey speed Survey speed <10E5 for the range above 3 GHz (TBV) C2p4.3 Survey speed 1000 SS_REQ_14: Baseline. The SKA minimum baseline requirement is (cf. Figure 7): 20 km for the range MHz (TBV) C8p4.4 Maximum baseline 20 km 5000 km for the range 150 MHz 8 GHz (TBV) C2p4.1 baseline >3000 km C15p4.1 Maximum Baseline > 3000 km 50 km for the range 8-10 GHz (TBV) C3p4.4 Maximum baseline km Page 6 of 9

7 SS_REQ_15: Main beam stability. The magnitude and phase variations of any SKA compound beam over a 12 hours period at any point of its half-power contour shall be less than 1% (TBV) relative to the beam peak. SS_REQ_16: Temporal resolution. Time sampling at: TBD SS_REQ_17: Spatial side-lobe stability. Spatial side lobes should be stable to within TBD. SS_REQ_18: Beam former weight update rate. Changing the beam former weights shall be possible every 60 seconds (TBV) in the case of scheduled switching sequences. SS_REQ_19: Beam former weight ad-hoc update response time. Changing the beam former weights shall be possible within 60 seconds in case of changes due to manual interaction or changes in schedule. SS_REQ_20: Beam-switching downtime flagging. Observation data (specify: both uv(w)-data and tied array beams) acquired during a change of beam direction shall be flagged. SS_REQ_21: Beam polarization stability. The polarization properties of the station and/or FPA compound beams should be stable enough to allow their calibration to better than 0.5% (TBV) with external calibration measurements no more than once per hour (TBV). SS_REQ_22: Stokes parameters. SKA shall provide visibility data in all four Stokes parameters. C5p4.7 Polarization purity C3p2 Observational Summary SS_REQ_23: Instrumental polarisation. The instrumental polarisation, after calibration, shall be less than 0.5% of the total intensity. (TBV) C4p4.7 C5p4.7 Polarisation purity Polarization purity SS_REQ_24: Transient RFI detection. The post station level processing shall detect and flag invalid data. C8p4.3 Frequency resolution Page 7 of 9

8 SS_REQ_26: Instantaneous field of view. SKA shall have a field of view of at least 278 deg2 (1000 arc minutes, science case 14) for the maximum possible frequency range for science case 12 in the DRM, and 20 deg2 for science case5. For the other science cases there are no explicit FOV requirements. A derived FOV number can be obtained by combining the highest survey sensitivity requirements and the highest sensitivity requirements, cf. Figure 8. This derived number, however, is not a requirement. SS_REQ_27: Field of view imaging. It shall be possible to image the entire field of view SS_REQ_28: Imaging dynamic range. SKA shall be able to provide an imaging dynamic range for continuum imaging (thermal noise imaging to classical (micro Jansky (Jy)) confusion limits) of at least: no specification for the band MHz C12p4.4 Polarization 74 db for the frequency band 300 MHz 3 GHz C2p4.6 Imaging dynamic range 42 db C4p4.8 Dynamic range 60 db C5p4.8 Dynamic range 50 db C6p4.5 Imaging dynamic range 74 db 42 db for the band 3-8 GHz C2p4.6 Imaging dynamic range 42 db SS_REQ_29: Dish beam absolute pointing accuracy. The pointing accuracy of the dish beams is: TBD SS_REQ_30: AA beam absolute pointing accuracy. The pointing accuracy of the AA beams is: TBD SS_REQ_31: FPA compound beam absolute pointing accuracy. The pointing accuracy of the PAF compound beams is: TBD SS_REQ_32: Dish beam pointing estimation accuracy. The pointing estimation accuracy of the dish beams is: TBD Page 8 of 9

9 SS_REQ_33: AA beam pointing estimation accuracy. The pointing estimation accuracy of the AA beams is: TBD SS_REQ_34: FPA compound beam pointing estimation accuracy. The pointing estimation accuracy of the FPA compound beams is: TBD SS_REQ_35 to SS_REQ_ Page 9 of 9