2.1.1 Accessing a Specific Time Interval Using YODAT

YODAT is a general purpose routine that will access all types of Yohkoh data, together with certain datasets from ground-based observatories. The detailed operation of YODAT is described on page , but here we present a short summary.

After starting YODAT (within IDL) the user must select a BDA file (or files). YODAT reads in the roadmap of the selected file and the user must then decide on which further selection procedure to use. The user can:

1. Use the x options within YODAT to select a time interval using a BCS light curve and read in the data for that time interval - the best channel to use for this is probably channel 3 (Ca XIX). YODAT returns the data and index arrays, and (for the BCS) optionally the dp_sync array.

2. Exit YODAT (using the option), make a selection of a part of the data from the roadmap by constructing an ss vector, and then read this data by re-running YODAT using option . Again, YODAT will return the data and index arrays, and optionally the dp_sync array. This non-YODAT selection can be done in various ways, two are:  
   1. use LIST_BDA to list the mode header information from the roadmap, then find the time interval and use the ss=ss option to produce the ss array that can be used with YODAT.
      IDL> list_bda,roadmap,start_rec,nrec,ss=ss
       
   2. use SELECT_BDA to plot the roadmap light curve of a selected channel and select the period of interest using the cursors. (Note: there is an option to read the data in with select_bda if required).
      IDL> .run select_bda