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Sun observations with prototype tile

Sun observations with prototype tile. Test carried out at ASTRON spring 2008 (Mark Ruiter, Erik van der Waal, et al.) ‏ Analysis in Meudon (Olofsson, Torchinsky et al.) ‏ Will mention other related activities at end. Encouraging « first light » results with prototype EMBRACE tile.

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Sun observations with prototype tile

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  1. Sun observationswith prototype tile Test carried out at ASTRON spring 2008 (Mark Ruiter, Erik van der Waal, et al.)‏ Analysis in Meudon (Olofsson, Torchinsky et al.)‏ Will mention other related activities at end Encouraging « first light » results with prototype EMBRACE tile Henrik OlofssonGEPI, Observatoire de Paris

  2. Between 15/4 and 15/5, quasi-continuous 24h coverage • Pointed south, elevation~45° but « manual » tracking attempted too • No beam forming, bore-sight only • Spectral range 827-927 MHz, passband filter applied

  3. SnapshotPowervsfreq. Bandpass Sun Mean powervstime(2 x 24h)‏

  4. Limitations • Vertical beam position not known in detail ↔ X dB pointing loss • Tsys not known à priori • Not a standard spectrometer • Some details of test uncertain • ...but not too important, zeroth order results here

  5. Analysis • Verify beam size / 1d side lobe pattern • System temperature (single dish equivalent) • Sensitivity / baseline stability vs time • Integration time & effective spectral resolution

  6. Beam size • Simple approach: measure time between half power points = 90 mins • Assume source size << beam size • Sun angular speed is .25 °/min. • ⇒ HPBW ≈ 22.6° • Compare theo. dish beam:θ3db = 1.2 ✕ λ / D ≈ 21.9° (D=1.1m,λ=35cm)‏

  7. Beam pattern • Not really feasible, have to disentangle many effects:- Phased array ⇒ 2d beam pattern- System artifacts (diurnal, transients,...)- Galactic plane- RFI

  8. System temperature • Use Sun as hot-load measurement:Tsys = Tcal✕Ssky / (Scal -Ssky)‏ • Here: Tcal = Tsun✕ ηbf ✕ ηmb • ηmb not known, assume range 0.5-1.0 • ηbf from θ3db and θsun

  9. Tsun at 35cm ? Brightnesstemperaturevs wavelength[cm] Avignon et al. 1975, Solar Physics, 45, 141 Zirin et al. 1993, ApJ, 370, 779 ⇒ Tsys ≈ 150-300 K ⇒ Tsun ≈ 105 K

  10. Sensitivity & (spectral) baseline TRMS = 20.5✕ Tsys / ( τ ✕ Δf )0.5 therefore, in theory log(Ťrms) α - log(τ) NB!Real integrationtime / spectrumis a few μs(not 90s)‏

  11. Spectral resolution • True effective resolution vs channel spacingstd[Tsys✕ (Son-Soff) / Soff] = 20.5 ✕ Tsys / ( τ ✕ Δf )0.5 • So product of int.time and f.res. can be determined from uncalibrated measurement • Exact figure for integration time will yield f.res. but TBD ... if at all since it is • ...not that important for now, spectrometer dependent and so on

  12. RFI NB! Different freq.

  13. Other activities Weak line spectroscopy experiment around λ=23,36 cm- recent Effelsberg observations- RFI pretty bad but not hopeless Test in progress of final design As for astronomical testing,can we do more than Sun, Cas A, Cyg A, gal.HI? Also satellites but not many at 0.5-1 GHz.Isotropic transmitter preferred for Aeff estimate. Progress in data readout/format, and telescopeuser interface

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