Chapter 34
GHRS Instrument
Overview

In This Chapter...

GHRS History / 34-2
Instrument Description / 34-3
Operating Modes and Data Types / 34-11
Documentation and References / 34-12

The Goddard High Resolution Spectrograph (GHRS) was designed by the GHRS Investigation Definition Team (IDT) consisting of J. Brandt (Principal Investigator), E. Beaver, A. Boggess, K. Carpenter, D. Ebbets, S. Heap, J. Hutchings, M. Jura, D. Leckrone, J. Linsky, S. Maran, B. Savage, A. Smith, L. Trafton, F. Walter, and R. Weymann. The instrument was built by Goddard Space Flight Center and prime subcontractor Ball Aerospace. The instrument is described in Brandt, J.C., et al., 1994, "The Goddard High Resolution Spectrograph: Instrument, Goals, and Science Results," PASP, 106, 890.

You are probably someone who wishes to study archival data from the GHRS since most General Observers (GOs) have completed their data analysis by now. Archival Researchers (ARs) face several problems-only some of which the original observer experienced:

Determining if any GHRS observations in the archive are likely to be useful for your purposes. To understand the basic properties of the GHRS, you may wish to refer to the GHRS Instrument Handbook version 6 because that document was written to guide people writing the detailed proposals that led to the observations that are in the archive. This HST Data Handbook includes many portions of the instrument handbook that are useful for archival research.
Retrieving appropriate observations and other data files needed to calibrate them. Data retrieval and the use of StarView are discussed in Chapter 1 (Volume 1).
Understanding how those observations were planned and obtained, and assessing overall data quality. Again, the GHRS Instrument Handbook best explains how and why observations were taken, although most archival users will find this handbook sufficient. Data assessment for the GHRS is discussed in Chapter 35.
Recalibrating those observations using the best available knowledge of the instrument. This is the major focus of this handbook.
Analyzing the observations to extract useful observational quantities. Most of the discussion here is on data reduction, but some aspects of analysis are covered as well. Of course data reduction is what you must do before you get to the interesting work, which is extracting useful astrophysical information from your data. Reading manuals about the data reduction process is seldom more entertaining than the reduction itself. Our goal in this handbook is to save you a lot of wasted time and effort by helping you to do the reduction job right the first time.
This section follows the basic outline of all of the chapters of this handbook. This first GHRS chapter (Chapter 34) describes the instrument, its general use, and important sources of additional information. Chapter 35 describes the data formats and data assessment-methods for determining whether the target was successfully acquired and the overall quality of the data. Chapter 36 describes the calibration process and how results can be improved. Chapter 37 describes error sources and uncertainty-topics intertwined with calibration. Chapter 38 concludes the GHRS part of this manual and describes various topics related to data analysis.
Although the GHRS was retired as an active instrument, STScI continues to provide analysis support for GHRS data. GHRS questions should be sent via E-mail to: help@stsci.edu. Any updates to GHRS documentation and calibration will be summarized in the HST Spectrographs Space Telescope Analysis Newsletter (STAN).

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Chapter 34 GHRS InstrumentOverview

In This Chapter...

Chapter 34
GHRS Instrument
Overview