The PACS Observer's manual is intended to support astronomers in the definition of their observations with the PACS instrument. The purpose of this document is to provide relevant information about the PACS instrument on-board Herschel Space Observatory to plan PACS observations in HSpot. The information is mainly targeted to be a general overview of the instrument and its performance, in order to help the astronomer to plan, prepare and execute scientific observations with PACS.

The structure of this observer's manual is as follows: we first describe the instrument (Chapter 2) and its scientific capabilities of the photometer and spectrometer (Chapter 3 & 4), the use of astronomical observation templates (AOTs) to enter PACS observations in HSpot( Chapter 5 & 6) and the manual ends with a description of the pipeline (Chapter 7).

This version is written to support the 2010 Open Time call for Herschel observing proposals by the European Space Agency (ESA).