Space Telescope Science Institute
COS Data Handbook 2.00
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COS Data Handbook > Introduction > Handbook Structure

Handbook Structure
The COS Data Handbook is organized in five chapters, which discuss the following topics:
Chapter 1:COS Overview provides a brief overview of the instrument and its operational capabilities.
Chapter 2:COS Data Files describes the contents of COS data files, the meanings of selected header keywords, and the relationship of the data products to the original Phase II proposal.
Chapter 3:COS Calibration describes how the calibration pipeline processes observations, the content of COS reference files used during calibration and how to run the calibration pipeline locally.
Chapter 4:COS Error Sources describes the sources of uncertainty and limiting accuracies of COS data. COS observers should read this chapter to acquaint themselves with the limitations of the data that may remain after pipeline calibration.
Chapter 5:COS Data Analysis describes certain IRAF/PyRAF/STSDAS tasks, and other software packages useful for optimizing data products and analyzing the data. In particular, it discusses software tools that can be applied to specific types of data and data formats. It describes how to analyze target acquisitions and guide star tracking. It provides descriptions of different kinds of data and gives detailed instructions on how to work with them; specifically: extracted spectra, and TIME-TAG data.
There are some important pieces of general information about HST data, the HST Archive, and the IRAF and STSDAS analysis software that are not specific to the COS, and which are therefore not discussed in the COS specific section. Users are referred to a companion volume, Introduction to HST Data Handbooks. In particular, Chapter 1, Chapter 2 and Chapter 3 of the Introduction to HST Data Handbooks describe how to retrieve and read HST data, HST file formats, and the basics of the STSDAS software package. Chapter 4 offers an IRAF primer. Chapter 5 describes HST file name conventions and exposure “associations”. Chapter 6 describes HST Observation Logs. Additional help with HST data is always available via email to the STScI Help Desk at
Because COS is a relatively new instrument, our characterizations of it are still changing. Consequently, readers are advised to consult the COS Web pages ( for the latest updates.

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