Top] [Prev] [Next] [Bottom] . Our understanding of the heritage HST instruments and the data they produced has matured, but may continue to improve. In order to allow for an evolving understanding and recognizing that some users of heritage data may be working with the active instruments as well, we have organized this handbook so that its chapters are modular. You will be able to update your handbook simply by removing old chapters and indexes and replacing them with new ones. ...