Array Signal Processing: What are snapshots in Direction of Arrival estimation? I do have an overview of basic radar signal processing chain [Data cube, 3 stages of FFT, Range, Range-Doppler map, coherent/non-coherent integration, coarse DoA etc.]. 

I am now trying to understand an advanced DoA estimation technique-MUSIC and one of the road blocks is the snapshot concept. Nearly every paper retrieved from google assumes an prior understanding of snapshots and am yet to find one that tells me what exactly is it.

So, what are snapshots in DoA estimation?
A snapshot is simply a data capture (sample window) of ADC samples from all receivers, that we know holds all the information to resolve what we need (distance and/or direction) given the various dimensions involved (transmit pulse length, nearest possible target distance, farthest possible distance, maximum array dimension, and the echo wavelet length). This defines the delay (from start of transmit time) of the window and the length of the window. The literature refers to a "snapshot" because many systems can repeatedly take snapshots to integrate-out noise, etc., but other cheaper systems can't.