SPECTRUM data file can either be FITS files or VOTables. Saada models spectra as objects with both position and dispersion range. The dispersion range (min and max values + unit) is requested by the VO SSA service. Flux vaues are not stored into the DB but just keywords.
Extension Selection : By default Saada will consider the first
TABLE extension (first table for VOTables) as the spectrum to load. The field Extension to Load can nevertheless specify which extension must be loaded. This extension must be given either by number (e.g. #1 or by name. The selected extension can be drag and dropped from the data sample window.
- Spectral Coordinate
The Spectral Coordinate requires to give both unit and column name. The given column is supposed to contain the channel number. If no unit is given, the unit associate to the column will be taken. If the SaadaDB has a global spectral unit but no unit can be found, the spectral range won’t be computed at collection level. These spectrum won’t be accessible with SSAP. The Spectral Coordinate fields can either be set with a table column name or with constant values in "’" (e.g. ’0.2 12’
About unit conversion : The data loader attempts to convert the spectral range of the data file into a range expressed in the global unit defined at SaadaDB creation time. Some conversion formulas include the speed of the light (freq -> wl -> Energy). Saada code always relies on the vacuum seed of light. The administrator must take care with data sensible to this parameter.last update 2008-10-30