Baseline redundancy and radiometric sensitivity: a critical review

When computing the radiometric resolution of an interferometric radiometer the correlation among the errors of different baselines is usually assumed negligible. ln this way: a) the radiometric sensitivity turns out to be pixel independent (except for antenna pattern effects), and b) the error of the average of P redundant baselines is reduced by a factor of (P)1/2. While this may be the case in radioastronomy applications, for an on-board instrument where all the baselines are measured at the same time interval the errors will actually be correlated. This has two effects: a) The radiometric resolution changes from pixel to pixel and b) the radiometric resolution improvement introduced by redundance is reduced as compared with the case of independent errors. In this paper this correlation is computed and the results obtained are applied, first, to a fully redundant (all possible baselines are actually measured) filled linear array to analyze the actual radiometric improvement, and, next, to the same array without redundance to investigate the dependence of sensitivity on pixel information.