LOFAR Technical Issues
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LOFAR Technical Issues M.A. Brentjens ASTRON, Dwingeloo, The Netherlands 2019-05-20 Windmills: time line 2018 Raad van State dismissed all appeals 2018 spring manufacturer selected: Nordex NOW Development detailed measurement procedure 2019 summer windturbine RFI assessment 2020 H1 start construction 2020 Dec wind farm operational Windmills: covenant EM interference reduction Consequence < 35 dB No permission to build 35 dB ≤ improvement < 40 dB 56–62× 12 h idle 40 dB ≤ improvement < 50 dB Reduced idle time to be negoti- ated improvement ≥ 50 dB No restrictions • Astron must find 7 dB additional improvement in signal processing. (WMM project) • Agentschap Telecom establishes method to measure improvement in cooperation with Astron and wind farm developers. Being adapted to LOFAR • In case of conflict: binding arbitration. • Neither party will claim damage due to wind farm or lack thereof. RS509 RS508 RS407 RS406 Solar parks RS409 Planned solar parks near the LOFAR core 52.96 Nieuw-Buinen RS503 Paardetangendijk Buinerveen 52.94 Nieuw-Buinen HooghwegHooghweg Energy Energy Buinen Buinen Nieuw-Buinen Nieuw-Buinen 52.92 Daalkampen 52.90 RS305 Westdorp Latitude [deg] RS306 Westdorp Exloo 52.88 RS106 Valthermond M2883 Valthermond M3006 52.86 RS205 6.75 6.80 6.85 6.90 6.95 Longitude [deg] RS307 RS310 RS208 RS210 Other Spectrum Management • 52–54 MHz range: no amateur digital broadband allowed • 70–74 MHz range transferred from military to radio astronomy • Prevented bat-based transmitters at 150 MHz • Special liaison to government for coordination of clean energy initiatives (solar PV, wind, LED (street)lighting, . ) and LOFAR: Ilse van der Waaij. Data inspection: goals and status • ML for data inspection “Goal: automatic “operator email” suggestion” • HDF5 MS summary • Full complex dynamic spectra • 1000s plots: cluster first • Browser to explore clusters DAB+ spurious: spectrum Ger de Bruyn BREAKING! DAB spurious understood! BREAKING! DAB spurious understood! • PAGER = DITHERING SIGNAL! • P2000 only on when transmitting • KPN ERMES pager system decommissioned AT SAME TIME DAB+ rollout ended • Just a happy accident. • Possible solutions: I inject artificial dither I insert (and later remove) artificial delays I insert analogue DAB-suppression filter LOfar BEams: LOBEs David Prinsloo “The primary objective of the LOBEs project is to derive, implement, and commission beam models for all low- and high-band antenna elements within the international LOFAR telescope.” Phase I LOfar BEams: LOBEs David Prinsloo “The primary objective of the LOBEs project is to derive, implement, and commission beam models for all low- and high-band antenna elements within the international LOFAR telescope.” Phase II • Actual simulation of all antenna’s in the ILT • Implementation of new LOFAR beam library based on database of simulated element beams • Full-band verification of this library using 24-h cross-calibration of several flux density calibrators at all their azimuths and elevations LOBEs: Altair-FEKO sims David Prinsloo Total power spectroscopy: main problems Mean spectral power (PPF) 1.0 0.8 0.6 Power 0.4 0.2 0.0 0 200 400 600 800 1000 Channel • Station subband bandpass correction on Cobalt insufficient for narrowband work • Core not coherent, particularly in LBA Total power spectroscopy: cobalt vs BG/P Subband bandpass correction versions FFT of subband bandpass correction versions 1.0 Cobalt 64 ch 1.04 Cobalt 256 ch BG/P 0.8 1.02 0.6 1.00 0.4 Normalized power Normalized power 0.98 0.2 Cobalt 64 ch 0.96 Cobalt 256 ch BG/P 0.0 0 50 100 150 200 250 0 20 40 60 80 100 120 Channel Fourier mode Total power spectroscopy: core coherence • Reasonable in HBA • Horrific in LBA • New LBA (and HBA) core cal solutions by Tied Array Beam holography • More permanent solution: replace clock distribution by WhiteRabbit technology: CSYLOPHON project Tied Array Holography: HBA pre cal Tied Array Holography: LBA pre cal Tied Array Holography: LBA post cal Summary • Windmills: clarity this fall • Solar parks: covenants being signed • Data inspection: new tools available internally at ASTRON • DAB spurious: understood and solution underway for DUPPLO • Beams: Phase I modelling underway • Tied array spectroscopy: LBA beams solved, bandpass not yet.