= Solution
The <wavelength> corresponds to about $15\,\mathrm{GHz}$, in the low-frequency decrement part of the <thermal Sunyaev-Zeldovich effect>. Hot cluster <electrons> inverse-Compton scatter CMB <photons>. In the Rayleigh-Jeans limit,
$$
\frac{\Delta T}{T_{\rm CMB}}\simeq-2y,\qquad
y=\int n_e\sigma_T\frac{k_BT_e}{m_ec^2}\,dl.
$$
The signal probes integrated <electron> <pressure>. Short baselines give sensitivity to extended arcminute-scale cluster structure, while the primary field covers the cluster and surrounding sky. The array's several-arcminute resolution suits many such structures; it is not equally well matched to every cluster size.
Simultaneous cross-correlations reject uncorrelated receiver <noise> and provide spatial information; compact radio sources can be constrained with the relatively longer baselines and separated from extended structure. Broad <frequency> coverage helps sensitivity provided channel smearing is controlled. Correlated atmospheric emission, <calibration> error, primordial CMB fluctuations and radio-source contamination remain relevant. The lack of zero and very short spacings also <means> that total integrated cluster <flux> requires a model or complementary data. An interferometer is therefore useful for the spatially resolved decrement, rather than automatically measuring every cluster's full <pressure> integral.
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