Mirage is a powerful standalone java tool developed at Bell Labs for analysis of multidimensional data. It uses its own file format for input.
TOPCAT can write tables out in the input format which Mirage uses, so that you can prepare tables in TOPCAT and write them out for subsequent use by Mirage. If you select 'Mirage' as the format in the Save Table dialogue a file will be written in this format.
It is possible in principle to launch Mirage directly from within TOPCAT. In order for this to work the Mirage classes must be on your classpath (the Mirage jar file should appear as a colon-separated entry in your CLASSPATH environment variable in Unix) when TOPCAT is run. Mirage will run on the table currently visible in the table browser, i.e. with any column or data changes or row subsetting you have applied in effect.
There is a bug in Mirage which means this does not always work - sometimes Mirage starts up with no data loaded into it. In this case you will have to save the data to disk in mirage format and start up Mirage separately and load the data in using the New Dataset item in Mirage's Console menu.
Note that when Mirage has been launched from TOPCAT, exiting Mirage or closing its window will exit TOPCAT as well.