A.O. Henrik Olofsson1 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 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 Henrik Olofsson GEPI, Observatoire de Paris

A.O. Henrik Olofsson2 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 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 MHz, passband filter applied

A.O. Henrik Olofsson3 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 Snapshot Power vs freq. Bandpass Mean power vs time (2 x 24h)‏ Sun

A.O. Henrik Olofsson4 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 Limitations Vertical beam position not known in detail ↔ X dB pointing loss T sys not known à priori Not a standard spectrometer Some details of test uncertain...but not too important, zeroth order results here

A.O. Henrik Olofsson5 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 Analysis Verify beam size / 1d side lobe pattern System temperature (single dish equivalent) Sensitivity / baseline stability vs time Integration time & effective spectral resolution

A.O. Henrik Olofsson6 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 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: θ 3db = 1.2 ✕ λ / D ≈ 21.9° (D=1.1m,λ=35cm)‏

A.O. Henrik Olofsson7 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 Beam pattern Not really feasible, have to disentangle many effects: - Phased array ⇒ 2d beam pattern - System artifacts (diurnal, transients,...) - Galactic plane - RFI

A.O. Henrik Olofsson8 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 System temperature Use Sun as hot-load measurement: T sys = T cal ✕ S sky / (S cal -S sky )‏ Here: T cal = T sun ✕ η bf ✕ η mb η mb not known, assume range η bf from θ 3db and θ sun

A.O. Henrik Olofsson9 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 T sun at 35cm ? Brightness temperature vs wavelength [cm] Avignon et al. 1975, Solar Physics, 45, 141 Zirin et al. 1993, ApJ, 370, 779 ⇒ T sun ≈ 10 5 K ⇒ T sys ≈ K

A.O. Henrik Olofsson10 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity & (spectral) baseline T RMS = ✕ T sys / ( τ ✕ Δf ) 0.5 therefore, in theory log(Ť rms ) α - log( τ ) NB! Real integration time / spectrum is a few μs (not 90s)‏

A.O. Henrik Olofsson11 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 True effective resolution vs channel spacing std[ T sys ✕ (S on -S off ) / S off ] = ✕ T sys / ( 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 Spectral resolution

A.O. Henrik Olofsson12 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 RFI NB! Different freq.

A.O. Henrik Olofsson13 EMBRACE Solar Scans 4 th SKADS Workshop, Lisbon, 2-3 October 2008 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 GHz. Isotropic transmitter preferred for A eff estimate. Progress in data readout/format, and telescope user interface