History of Ulterior Observation

Ulterior Observation is a Legendary Stasis Machine Gun (heavy slot) from The Edge of Fate, a 600 RPM Aggressive Frame, functionally like Pro Memoria from The Final Shape (per search summary of a guide). The PvE dream roll is Subsistence with Killing Tally; PvP picks are Moving Target and Dynamic Sway Reduction.

Acquisition

Dropped by enemies and chests on Kepler (in-game source: "Exploring Kepler"), or targeted through Focused Decoding at the Altar of Relativity using Fated Ciphers and Phaseglass Refractions (Game Rant). Like all Kepler weapons it carries the "Exhaustive Research" origin trait, which loads micro-missiles when aiming at enemies. Sources do not mention a craftable pattern or Adept version.