On the Detection of Transiting Broadband Targets in Noise of Uncertain Level

The fact that the signal received from a transiting object first rises and then falls in intensity can be used to detect the presence of such an object even though the signal emitted by the object and the background noise are otherwise indistinguishable. If the strength of the background noise is not known, detectability is reduced by the uncertainty in the noise level; however, means can be incorporated in the detector to estimate the noise level. If this is done, and if the background noise can be assumed to be stationary, then the effect of the noise uncertainty can be made as small as desired. In practice, the background noise is not stationary, and therefore the improvement in detectability that can be realized by estimating the noise level depends on the length of time that the noise can be assumed to be essentially stationary.