A Sikorsky MH-67 Pave Mare under ECS camouflage. Shown in white are the outlines of the chopper in ECS mode.
Electronic Conceal System or ECS is a form of active camouflage using Black Technology that provides near total concealment from RADAR and other electromagnetic forms of detection (including the naked human eye). ECS has been shown to be used on arm slaves, helicopters and other military vehicles for covert operations.
Initial systems are said to have had limited capabilities that only masked millimeter wavelength microwaves and later, infrared signatures. More recent systems are more powerful, and are capable of masking signatures in the visual range of the electromagnetic spectrum. The system works by utilizing a rapidly oscillating laser screen to project some sort of distortion around the concealed object. Specific details are not described, but has shown adaptability to sudden and violent changes in ambient conditions and the ability to see out from within the concealment, making the system suitable for combat deployment. The view from within an ECS field is washed out and tinged in violet and red.
The technology requires a significant power input and significant size, and thus deployment was limited by the power-plant of craft the ECS is to be mounted to. It is assumed that shorter wavelength (such as the visual range) is more complex and requires more power. It is noted that an ECS capable of invisible mode operation (masking visual spectrum signatures) is also capable of operating in a more limited mode, such as only masking its radar signature. Its immense power requirements make the use of the system while making combat maneuvers impossible on Arm Slaves. Human sized ECS units are also not yet possible without a suitable power source and miniaturization.
In the world of Full Metal Panic, the B-2 Bomber was never developed. Instead, the B-1 Bomber was deployed with the ECS. This is designated as the B-1C. This places the development of the ECS after 1975 and before the early 1980s. As such, passive stealth technology is a largely forgotten technology.
The ECS is not impervious. Its weaknesses include its inability to mask UV spectrum emissions. A high output ECS also ionizes the air, emitting ozone. Insects, and birds attracted to insects gather around an active ECS from the UV signature. Dogs have been observed avoiding an active ECS from its ozone smell. Additionally, it is specifically stated that the ECS is useless in rain (presumably interfering with the laser or failing to mask the water accumulating on the hull) . Recent developments in countermeasures include the ECCS (Electronic Conceal Counter System) designed to detect ECS signatures.