Not that I'm skillful enough to make an emulator, but I've tried years ago to find technical documents on the Honeywell HDC-402 used in Voyager and Viking (it's also apparently not related to the DDP-516 or 316 AFAIK.) There's SOME information[1], but not enough to make an emulator from what I've found.

Aside from the lack of schematics or listings, there was the problem of the assembler being incomplete!

"One problem Lander software developers had was that no adequate assembler was ever written for the computer, perhaps because of the changing nature of the instruction set.(110) Patches had to be hand-coded in octal, with many jumps to unused memory space because of the lack of an assembler with relocatable addressing." p.174 on Viking, which used the same computer

[1]https://ntrs.nasa.gov/api/citations/19880069935/downloads/19... (page 174 onwards)