What is the name of the Army SIGINT aerial platform that provides COMINT and ELINT capabilities?

The Army SIGINT aerial platform that provides Communications Intelligence (COMINT) and Electronic Intelligence (ELINT) capabilities is known as Guardrail. This system is specifically designed for tactical signals intelligence and utilizes various sensors to intercept and analyze electronic communications and signals. Guardrail can be deployed in various operations to gather critical intelligence, making it a vital asset for the Army's information-gathering efforts.

In this context, while other platforms mentioned have their own unique roles and capabilities, Guardrail is particularly tailored for SIGINT tasks, distinguishing it from options like U-2 Dragon Lady, which is primarily a strategic reconnaissance aircraft, or MQ-1C Gray Eagle, which serves as an unmanned aerial vehicle designed for various missions, including armed reconnaissance. BCCS, on the other hand, refers to a ground-based command and control system, which does not fall into the aerial platform category. Hence, Guardrail stands out as the appropriate answer due to its specific design and functionality in the SIGINT domain.