<p>Mixed-criticality (MC) systems must guarantee safety for high-criticality tasks under pessimistic assumptions while still delivering useful service from low-criticality tasks. The traditional Vestal approach does this by discarding all low criticality tasks after a mode switch, which is easier to certify but lacks functionality. The imprecise mixed criticality (IMC) approach alleviates this problem by dividing each low criticality task into mandatory and optional components, thus allowing graceful degradation. Although the IMC approach has been analyzed thoroughly for priority-driven scheduling algorithms such as EDF-VD, its combination with time-triggered (TT) scheduling has not been investigated, although there is a great industrial need for deterministic and certifiable execution. This paper proposes the first TT scheduling algorithm (TTA) for IMC systems. Our method constructs two static tables that guarantee all deadlines of high-criticality and mandatory low-criticality jobs under worst-case execution, while opportunistically accommodating optional work. We present correctness proofs, schedulability conditions, and a comprehensive evaluation on synthetic workloads. Results demonstrate that the proposed algorithm preserves determinism, achieves graceful degradation, and significantly outperforms EDF-IMC and existing baseline algorithms in terms of schedulability and robustness.</p>