For a full description of the Yohkoh database and all the different data structures, see the File Control Document.
Each file is logically divided into the following six sections. Some files will not use all the sections described below, but all will have a Pointer and File Header Section.
The program which reads the file learns from the Pointer Section how to read the rest of the file and where to go to get certain data.
The File Header Section provides information on what data are contained in the file, generally the extent of the time covered by the contents.
The Quasi-Static Section of the file contains index information that does not vary during the course of an orbit, or varies slowly.
The Index and Data section contains `data sets'. A data set is a single image for SXT, single spectrum for BCS, a single major frame of data for HXT, and two major frames of data for WBS (it takes two major frames for a complete set of WBS data). For each data set there is an index which describes the date and time that the data were taken, the mode and position of the instrument's peripherals (e.g., filters, HV), and information on temperature and gain information.
The Optional Data Section is only used by the BCS data (BDA) files and the spacecraft attitude (ADA) files. The BDA files hold the `DP_SYNC' information, which is information that is coming down every major frame. Since the BCS spectra are asynchronous to the major frames, it is stored separately. The ADA file holds the full 2048 point HXA scans.
The Roadmap Section allows a user to access a brief summary of the contents of the file and to perform searches on that summary to select what data should be extracted.