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CHAPTER 1: Introduction

GHRS Instrument Handbook


Both tasks may seem daunting at first because any versatile instrument has many options. But for what most people want to do most of the time there are defaults that apply, and the GHRS is, in fact, very easy to use. Once you know that what you want to do falls within the bounds of conventional uses of the spectrograph, you can have some confidence that your observations will be obtained in the form you originally desired. Or you can at least get a sense that what you are proposing is truly unusual and may push the limits of the instrument.

This Handbook exists as a basic reference manual for the Goddard High Resolution Spectrograph (GHRS), and describes its properties and operation. This Handbook is revised and reissued approximately once each year. This version is written for observers wishing to propose to use the GHRS in HST's Cycle 6, and it supersedes all previous versions. The GHRS is expected to be withdrawn from HST at the end of Cycle 6, so that this is the last opportunity to propose to use the instrument. This is also probably the last version of the Instrument Handbook that will be issued.

No HST document stands alone in providing complete information because each fills a particular need. The Call for Proposals, for example, describes the proposal submission process and provides a summary of the observatory and its instruments. The Phase II Proposal Instructions give detailed instructions for providing STScI with the specifications that translate your program into commands that HST executes. The instrument handbooks supplement both documents by providing the technical details of instrument performance and operation. The HST Data Handbookdescribes how software takes the raw data from the telescope and transforms it into a reduced and calibrated form for your further analysis and interpretation, and how you can duplicate those steps.

The GHRS is now a mature instrument and so we can predict what many observers will need. This Handbook is designed around the needs of the majority of users, so that essential information is concentrated in a few sections. Full details must also be given, of course, and they are provided in a reference section. We have also tried to provide the information you need to decide when your observations deviate from the "normal" and involve special aspects.

No handbook of this kind can be complete and error-free until the instrument itself is obsolete. We have, of course, edited it thoroughly, but if significant revisions are called for they will be announced via the GHRS Home Page on the World Wide Web, as with other HST news items (the URL is given at the end of this chapter). Please consult with us if you have questions; the means of contact are provided just after the title page.

This Handbook
Changes Since the Previous Version
Where to Find Information, Changes, Errata, etc.