PoS(SKADS 2009)059 W S T SKA SKADS C 2009 S.A. Torchinsky, A. van Ardenne, T. van den Brink-Havinga, A.J.J. van Es, A.J. Faulkner (eds.) 4-6 November 2009, Ch ˆ ateau de Limelette, Belgium Some results from the BEST demonstrator ⋆ S. Montebugnoli 1 , F. Perini 1 , G. Bianchi 1 , P. Bolli 2 , G. Pupillo 3 , G. Naldi 4 , M. Schiaffino 1 , and J. Monari 1 1 I.N.A.F. - I.R.A, Via Fiorentina, 3508/B 40059 Medicina, Italy email: s.montebugnoli@ira.inaf.it, f.perini@ira.inaf.it, g.bianchi@ira.inaf.it, mschiaffino@med.ira.inaf.it, j.monari@ira.inaf.it 2 INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy email: pbolli@ca.astro.it 3 INAF-Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025, Pino Torinese (TO), Italy email: g.pupillo@med.ira.inaf.it 4 Universit` a degli Studi di Bologna, Dipartimento di Astronomia, Via Ranzani 1, 40127 Bologna, Italy email: gnaldi@med.ira.inaf.it Abstract. In this contribution a collection of significant results from the BEST (Basic Element for SKA Training). demonstrator, based on cylindrical concentrators, is reported. Both technological deliverables and preliminary observation tests are available for further works and investigation on low frequency array. 1. Introduction A 1400 m 2 test bed, based on existing cylindrical concentrators of the Northern Cross array, has been prepared in the frame of the FP-6 SKADS program. Due to the velocity, programmabil- ity of the data acquisition system and the collecting area, the BEST prototype allowed to perform some beamforming activ- ities and several preliminary astronomical tests. Since a lot of very strong RFIs were present into the new 400-416 MHz op- erational band, a very valuable check of the dynamic range in both the analogue and digital dominions were possible. 2. Evaluation of the antenna noise temperature With BEST-1, the first in time SKADS technological demon- strator, based on the re-instrumentation of a single N/S cylindri- cal reflector of the Northern Cross radio telescope, we checked on the field the antenna temperature distribution calculation proposed by the International SKA Project Office, as a guide- line to compare all the SKA antenna sensors (Bolli et al. 2008). The simulated antenna temperature, T ant (see Eq. 1), was ob- tained through an ad hoc Fortran code, which integrated the proposed brightness temperature distribution T b (Cortes 2007), with the BEST-1 power pattern P n , obtained through GRASP simulations (see Fig. 1). T ant (ν; Θ 0 , Φ 0 , Δ 0 ) = P n (ν; θ, φ)T b (ν; θ ′ ,φ ′ ) sin θdθdφ P n (ν; θ, φ) sin θdθdφ (1) The calculations were done at the BEST-1 central frequency (ν = 408 MHz) and for various antenna pointing directions (Θ 0 , Φ 0 , Δ 0 ). In particular, since the Northern Cross is a transit telescope, we considered only the pointing in the co-elevation plane, from Θ 0 = 0 ◦ , which represent the pointing towards the ⋆ This work was supported by the European Commission Framework Program 6, Project SKADS, Square Kilometre Array Design Studies (SKADS), contract no 011938. Fig. 1: Co-polar 2D BEST-1 main beam in elevation over azimuth plane zenith direction, to Θ 0 = 80 ◦ (see Fig. 2). The three curves are related to the contributions coming from the ground (θ ′ > 90 ◦ , dashed curve), and from the sky (θ ′ ≤ 90 ◦ , solid curve). Finally, the dash-dot line shows the total antenna temperature, which is the sum of the previous two contributions. In order to ver- ify these numerical results, some experimental measurements were performed. The system noise temperature of BEST-1 (4 RX of a single N/S cylinder, summed together in order to ob- tain a single beam) was measured by detected transits of some strong calibrators (Cas-A and Virgo-A). Actually, the measure- ments allowed us to get the A eff /T sys figure. Hence, in order to determine T sys , the effective area was evaluated as the prod- uct of the geometrical area and the antenna’s efficiency. This last parameter was determined through the GRASP numerical