1. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Cambridge 8th-10th December 2010 Federico Perini 1, Jader Monari 1, Giuseppe Virone 2, Pietro Bolli 3 1 INAF/IRA-Medicina radio telescopes 2 IEIIT/CNR-Politecnico di Torino 3 INAF/Osservatorio Astronomico di Cagliari

2. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors G. Cortes Medellin, “Antenna Noise Temperature Calculations,” SKA Technical Memo Series n° 95 White paper on the antenna sub-systems for the SKA project: P.D. Patel, “Antenna Concepts Consideration for SKA”, part of the SKA memo 91, “An SKA Engineering Overview” by P. Hall Compare different antennas?

3. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors General formulation: where P n (v;  ) represents the antenna radiation pattern and T b (v;  ’  ’), the brightness temperature distribution (here T b (v;  ’))       Direction in the azimuth plane Zenith Horizon Antenna Temperature P n computation is demanded to an external EM Antenna CAD (GRASP, CST,…) whereas T b is evaluated by the Matlab code itself

4. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Two different coordinate reference systems: P n is defined respect to the one related to the antenna itself (z axes = main beam or pointing direction) whereas T b is defined respect to the Earth (z’ = local zenith) To compute the integral we need only one coordinate system, so we need the conversion from one to another: Coordinate reference systems Ground Zenith Circumference at fixed  correspond to several values of 

5. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors The brightness temperature can be split in 2 main contributions: from sky (0° <  ’ < 90°) and from ground (90° <  ’ < 180°) Moreover the contribution from the ground (emission and scattering), is a polarization dependent process: Ground contribution

6. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors The Tb model is the one proposed by [Cortes], which includes the effects of the absorption coefficients of water vapour and oxygen, the CMB and the emission from the galaxy T go and  are function of the observed sky region [Cortes] suggests reasonable values as: T go  e  Zenithal opacity Atmosphere temperature Effect of Earth curvature Brightness Temperature

7. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Tb calculator ftp.ira.inaf.it/pub/outgoing/fperini/

8. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Ta calculator example 1: BEST-1 @ 408MHz

9. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Ta calculator example 2: 32mt VLBI Dish @ 22GHz

10. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors AAlo Vivaldi antenna Vivaldi Antenna, f=450MHz,  2 =3.5 P n resolution ,  (deg) Ta (K)Ta gnd (K)Ta sky (K) Time comp. (min) 2.569.452.417.013 569.151.617.53.5 Pattern at f max =450MHz For BEST-1 Tcomp=150 min, using two different spacing for P n, fine (0.04°) for the main beam and coarse (0.68° ) outside the main beam

11. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors AAlo Vivaldi antenna

12. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors T REC ? 50Ohm75Ohm Trec = TLNA = 30K @ 300K seems reasonable

13. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Aeff/Tsys?

14. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Aeff/Tsys

15. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Double size antenna? (Aeff/Tsys) 2 /(Aeff/Tsys) 1 Freq [MHz] theta=0° (zenith) theta=45° phi=90° theta=45° phi=0° 700.841.120.87 1201.590.821.79 2601.742.970.47 4500.931.831.11 Freq (MHz)Tant 1 [K]Tant 2 [K] 7017851879 120484530 260112105 4506758

16. AAVP Workshop December 2010 TITLEAAVP Workshop December 2010 Aeff/Tsys evaluation for AAlo sensors Future works T b (v;  ’)  T b (v;  ’  ’) Considering the coupling effect Take in account the array factor at station level (antennas positioning) and at full array level (stations positioning) Stronger collaboration with all partners involved in this task Thanks!