This chapter discusses the files in which MSG stores its data. These files adopt the HDF5 data format, a platform-neutral binary storage format with advanced features such as transparent decompression.
There are five types of MSG data files, distinguished by their differing content:
specint files store spectroscopic intensity data for a single combination of photospheric parameters.
photint files store photometric intensity data for a single combination of photospheric parameters.
specgrid files store spectroscopic intensity data over a grid of photospheric parameters.
photgrid files store photometric intensity data over a grid of photospheric parameters.
passband files store passband response functions, used to convert spectroscopic intensities into corresponding photometric intensities.
For a detailed description of each file type, refer to the Data Schema chapter.
MSG ships with a limited set of data files in the
$MSG_DIR/data subdirectory, sufficient to enable the
passbands/pb-Generic-Johnson.*-Vega.h5are passband files for the U, B and V filters of the Johnson photometric system.
To import an existing spectroscopic grid into MSG, first convert the individual spectra into corresponding specint files. MSG provides a number of tools to assist with this conversion; see the Grid Tools appendix for further details.
The next step is to create a manifest (named, say,
manifest.txt) listing all the specint files
composing the grid. This is a simple text file with each line naming
one file; for instance:
specint-0001.h5 specint-0002.h5 specint-0003.h5
Then, run the specint_to_specgrid tool to create a specgrid file:
$MSG_DIR/bin/specint_to_specgrid manifest.txt specgrid.h5
$MSG_DIR/bin/specgrid_to_photgrid specgrid.h5 passband.h5 photgrid.h5
passband.h5 is the name of the passband
file to use. Note that it’s not always necessary to create a
photgrid file, as MSG can convolve with passbands on the
fly (as discussed in the Photometric Colors section).