We don't know why this would be referenced in DTM custom code, but it was... It was always an internal object that contained information about the tools in use by the DTM property. As an example, here's a snap of _satellite.tools from a sample DTM property.
sample view of _satellite.tools object
What were "Tools" in DTM are "Extensions" in Launch. Launch exposes information about the installed extensions via
_satellite.container.extensions. Just for parity, below is a sample snap of this object.
sample view of _satellite._container.extensions object
(as of 8/19) _satellite.container.* is still marked as unstable. If you need to reference the data in it, do so with caution. Stability is coming soon.