DETECTION AND SUB-PIXEL LOCALIZATION OF DIM POINT OBJECTS

Detection of dim point objects plays an important role in many imaging applications such as early warning systems, surveillance, astronomy, and microscopy. In satellite imaging, natural phenomena, such as clouds, can confound object detection methods. We propose an object detection method that uses spatial, spectral, and temporal information to reject detections that are not consistent with a moving object and achieve a high probability of detection with a low false alarm rate. We propose another method for dim object detection using convolutional neural networks (CNN). The method augments a conventional space-based detection processing chain with a lightweight CNN to improve detection performance. For evaluation of the performance of our proposed methods,

we used a set of curated satellite images and generated receiver operating characteristics (ROC).

Most satellite images have adequate spatial resolution and signal-to-noise ratio (SNR) for the detection and localization of common large objects, such as buildings. In many applications, the spatial resolution of the imaging system is not enough to localize a point object or two closely-spaced objects (CSOs) that are described by only a few pixels (or less than one pixel). A low signal-to-noise ratio (SNR) increases the difficulty such as when the objects are dim. We describe a method to estimate the objects’ amplitudes and spatial locations with sub-pixel accuracy using non-linear optimization and information from multiple spectral bands. We also propose a machine

learning method that minimizes a cost function derived from the maximum likelihood estimation of the observed image to determine an object’s sub-pixel spatial location and amplitude. We derive the Cramer-Rao Lower Bound and compare the proposed estimators’ variance with this bound.