ds9 [L1 ] is an astronomical image display program writen at the Smithsonian Astrophysical Observatory.
It's written in tcl of course. The widget set used is SAOTk [L2 ] (Papers: [L3 ] [L4 ])
It also stands for Deep Space 9.
The High Energy Astrophysics Division of SAO has a preocupation with things Star Trek. Our second generation image display was named TNG and the third is ds9.