What is the nomenclature for the direct fire sight?

The correct nomenclature for the direct fire sight is M137A2. This model is used specifically with field artillery systems, providing improved targeting accuracy during direct fire operations. It is designed to assist artillery crews in engaging targets at a shorter range with precision, which is crucial in combat scenarios where indirect fire is not feasible.

The other options do not represent the correct nomenclature for the direct fire sight. The M1A2 is associated with tank weapon systems, while the M90A3 designates a different artillery equipment component. Meanwhile, the M137A1 is a previous version of the direct fire sight that has since been replaced by the M137A2, which includes upgrades for enhanced performance.