The PHT Handbook is one in a series of five1.1 documents that explain the operations of the Infrared Space Observatory (ISO) and its four instruments, the data received from the instruments and the processing carried out on the data. Volume I gives an overview of the entire ISO mission and it explains the operations of the ISO satellite while the remaining four explain the individual instruments (CAM, LWS, PHT and SWS). The PHT document is intended to provide all information necessary to understand the offered ISOPHOT standard data products, as processed by version 10 of the Off-Line Processing (OLP) system, retrievable from the Legacy ISO Data Archive (IDA) at:
Besides OLP10 software processing steps and product specific details, background information is provided about the ISOPHOT instrument itself, its observational modes and all aspects of calibration.
Although it tries to contain as completely as possible ISOPHOT related information, it should be stressed that this manual is not intended to support interactive data analysis. For specific algorithms to process and improve the results interactively we refer to the ISOPHOT Interactive Analysis Users Manual, [9] and to the ISOPHOT instrument page:
https://www.cosmos.esa.int/web/iso 
ISO Explanatory Library
PHT.
This volume of the ISO Handbook serves as the reference for both the processing as well as the correct interpretation of ISOPHOT data as available from the ISO Data Archive.