The SWIFT BAT Software Guide Version 6.3 30 ... - HEASARC - Nasa

Chapter 4
Introduction to BAT Analysis
4.1 Introduction
This chapter contains a discussion of the basics of coded mask analysis, differences from direct
imaging systems, and useful science information about the BAT, like the coordinate system and
units.
4.2 Coded Apertures: Basic Concepts
The BAT instrument has a coded aperture. The basic premise of a coded aperture is quite different
from normal imaging optics, primarily because there are no focussing optics. All of the “optical”
elements of a coded aperture are passive, involving the casting shadows from the aperture (mask)
onto an imaging sensor.
Figure 4.1: Basic BAT imaging scheme. A gamma-ray source illuminates the coded aperture
(mask), and casts a shadow onto a position sensitive detector.
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