De or het robotmissie?

The correct Dutch article is:

de robotmissie

Rule Words ending in -tie and -sie: almost always de. See the rule

How to use robotmissie

the robotmissiede robotmissie
this robotmissiedeze robotmissie
that robotmissiedie robotmissie
our robotmissieonze robotmissie
your robotmissiejouw robotmissie
every robotmissieelke robotmissie
which robotmissie?welke robotmissie?
a big robotmissie / the big robotmissieeen grote robotmissie, de grote robotmissie