Field of view for near-field aperture synthesis imaging

TL;DR

This paper demonstrates that under paraxial conditions, standard aperture synthesis imaging techniques can be applied to objects larger than the traditional near-field limit, enabling high-resolution imaging of large near-field objects like satellites.

Contribution

It extends near-field aperture synthesis imaging capabilities by showing larger fields of view are possible without precise object range information.

Findings

Standard interferometric techniques can image larger objects in the near field.

Self-calibration and phase-closure methods enable near-field refocusing.

The field of view for satellite imaging from the ground can be significantly increased.

Abstract

Aperture synthesis techniques are increasingly being employed to provide high angular resolution images in situations where the object of interest is in the near field of the interferometric array. Previous work has showed that an aperture synthesis array can be refocused on an object in the near field of an array, provided that the object is smaller than the effective Fresnel zone size corresponding to the array-object range. We show here that, under paraxial conditions, standard interferometric techniques can be used to image objects which are substantially larger than this limit. We also note that interferometric self-calibration and phase-closure image reconstruction techniques can be used to achieve near-field refocussing without requiring accurate object range information. We use our results to show that the field of view for high-resolution aperture synthesis imaging of geosynchronous satellites from the ground can be considerably larger than the largest satellites in Earth orbit.