Unattended ground sensor

Unattended Ground Sensor (UGS) are generally seen as military devices that can provide surveillance of ground areas, sending alerts back by telemetry. Some of the earliest versions were deployed in the Vietnam War. . During Vietnam, these did not provide the functionality desired of the McNamara Line and Operation Igloo White. They have improved considerably, but still complement a humans on the ground and do not always replace them.

In the US, many of the Igloo White technology came from Sandia National Laboratories, who subsequently designed the Mini Intrusion Detection System (MIDS) family, and the US Marine Corps' AN/GSQ-261 Tactical Remote Sensor System (TRSS). Another major US Army initiative was the Remotely Monitored Battlefield Sensor System (REMBASS), which it upgraded to Improved REMBASS (IREMBASS), and now is considering REMBASS II. The REMBASS generations, for example, increasingly intertwine interconnections of infrared MASINT, Magnetic MASINT, seismic MASINT, and acoustic MASINT

Commonwealth and NATO
The UK and Australia also are interested in UGS. Thales Defence Communications, a division of French Thales and formerly Racal builds the Covert Local Area Sensor System for Intruder Classification (CLASSIC) for use in 35 countries, including 12 NATO members. Australia adopted the CLASSIC 2000 version, which, in turn, becomes part of the Australian Ninox system, which also includes Textron Systems’ Terrain Commander surveillance system. CLASSIC has two kinds of sensors: Optical Acoustic Satcom Integrated Sensor (OASIS) and Air Deliverable Acoustic Sensor (ADAS), as well as television cameras, thermal imagers, and low-light cameras.

ADAS sensors were in a US program, Army Rapid Force Projection Initiative advanced concept technology demonstration (ACTD), using OASIS acoustic sensors and central processing, but not the electro-optical component. ADAS sensors are emplaced in clusters of 3 or 4, for increased detection capability and for triangulation. Textron says that the ADAS acoustic sensors can track fixed-wing aircraft, helicopters, and UAVs as well as traditional ground threats.

ACTD added Remote Miniature Weather Station (RMWS), from System Innovations. These RMWS measure temperature, humidity, wind direction and speed, visibility and barometric pressure, which can then be sent over commercial or military satellite links.

Urban environments
UGS are especially challenging in urban areas, where there is a great deal more background energy and a need to separate important measurements from them. Acoustic sensors will need to distinguish vehicles and aircraft from footsteps (unless personnel detection is a goal), and things such as construction blasting. They will need to discriminate among simultaneous targets. Infrared imaging, for the urban environment, will need smaller pixels. If either the targets or the sensor is moving, micro-electromechanical accelerometers will be needed.

Restructuring of the United States Army
As part of the Restructuring of the United States Army, new generations are being deployed in the Scout/Cavalry/Reconnaissance, Surveillance and Target Acquisition Squadrons of Brigade Combat Teams, both in a general tactical version and one specific to urban combat.

Future Combat Systems
UGS, in the cancelled Future Combat Systems of the U.S. Army, were intended to replace the improved REMBASS (I-REMBASS) systems now in use, which employ a mixture of electro-optical, magnetic, vibration/seismic, and acoustic sensors. Some of the technology will continue in development or deployment.

The new generation come in Tactical (T-UGS) and Urban (U-UGS) versions. They add Chemical, Radiological, Nuclear, and early warning.