noise=vis_noise(Tsys,tau,bw,A,eff) Calc E rms uncertainty of a complex visibility due to thermal noise. Output in Jy. This is sqrt(2)*sigma in eqn 6.51 of Ref TMS page 189. The uncertainty in the real or complex part is this times 1/sqrt(2) (see eqn 6.50). Note that the rms map noise is E/sqrt(2*n_b) where n_b is the number of baselines (see eqn 6.62) Tsys - system temperature tau - integration time in seconds bw - bandwidth in Hertz A - Antenna area eff - efficiency factor (correlator and/or aperture) eg: vis_noise(30,140*10*13*60,1e9,pi*0.1^2,0.8)*randnc(size(u))
0001 function noise=vis_noise(Tsys,tau,bw,A,eff) 0002 % noise=vis_noise(Tsys,tau,bw,A,eff) 0003 % 0004 % Calc E rms uncertainty of a complex visibility due to thermal noise. 0005 % Output in Jy. 0006 % This is sqrt(2)*sigma in eqn 6.51 of Ref TMS page 189. 0007 % The uncertainty in the real or complex part is this 0008 % times 1/sqrt(2) (see eqn 6.50). 0009 % Note that the rms map noise is E/sqrt(2*n_b) where n_b is the number 0010 % of baselines (see eqn 6.62) 0011 % 0012 % Tsys - system temperature 0013 % tau - integration time in seconds 0014 % bw - bandwidth in Hertz 0015 % A - Antenna area 0016 % eff - efficiency factor (correlator and/or aperture) 0017 % 0018 % eg: 0019 % vis_noise(30,140*10*13*60,1e9,pi*0.1^2,0.8)*randnc(size(u)) 0020 0021 noise=1e26*2*1.38e-23*Tsys./(sqrt(bw.*tau).*A.*eff);