Chapter 1: Introduction 1.1 About this Document 1.2 What’s New This Cycle 1.3 Resources, Documentation and Tools 1.3.1 Phase I “Roadmap” 1.3.2 Cycle 21 Announcement Web Page 1.3.3 Cycle 21 Call for Proposals 1.3.4 Instrument Handbooks 1.3.5 The Astronomer’s Proposal Tool (APT) and the Aladin Sky Atlas 1.3.6 Exposure Time Calculators (ETCs) 1.3.7 HST Data Archive 1.3.8 Data Reduction and Calibration 1.4 STScI Help Desk