Recently the U.S. Air Force successfully tested a new MS-177 sensor system for its RQ-4B Global Hawk UAV. The new sensor system is an MSI (multi-spectral imaging) type and the third generation of space satellite quality radar/optical sensors for the 13-ton RQ-4B UAV. This is a large, jet powered UAV that entered service in 2006. The initial satellite quality sensor system installed in 2008 was the Raytheon ISS (Integrated Sensor System). This was superseded by EISS (Enhanced ISS) in 2017 and as of 2021 the MS-177 is available as well. Each generation of sensors has performance that matched what was being used in surveillance satellites, which are becoming smaller and lighter as a result of the new sensor systems. The RQ-4B and satellite sensors included AESA SAR (synthetic aperture radar) as well as electro-optical and infrared (heat) sensors.
These sensors can provide real-time video as well as photos and images in several different forms. That’s because multi-spectral sensors can detect different types of vegetation or the composition of the surfaces below. The SAR provides photo-like 3-D images of small objects in any weather and at night. There are also SIGINT (Signals Intelligence) modules as well as defensive systems like a radar-warning system and jammers to protect against SAMs (surface to air missiles). All the imagery and other sensor data collected by a RQ-4B is transmitted via satellite to the ground, and can easily be put onto an Internet connection. In effect, the RQ-4B is like having a reconnaissance-satellite overhead all the time but also one that can circle in the sky and provide persistent surveillance, something a satellite cannot provide. One reason for the greater detail provided by MS-177 compared to heavier equipment in satellites is that the satellites are 400-500 kilometers from the surface while the RQ-4B operates at 20 kilometers from the surface.
The RQ-4B has a wingspan of 42.3 meters (131 feet) and 15.5 meters (48 feet) long), which is ten percent larger than the A model, and can carry an additional two tons of equipment. The B version also has a new generator that produces 150 percent more electrical power. The B version is a lot more reliable and can fly missions that last up to 30 hours. When used in survey mode the RQ-4B sensors can operate in spot collection mode and cover nearly 2,000 two square-kilometer spots a day to survey the samples of terrain below for composition and vegetation coverage of a large area, or in wide-area search mode that records a ten-kilometer wide strips over a large area, covering about 100,000 square-kilometers (38,000 square miles) a day. The latest sensor upgrades allow for individual buildings, vehicles or ships to be seen in greater detail (resolution) even if the land vehicles are hidden in forests. Type of aircraft, vehicles and ships can be identified.
The first three RQ-4Bs entered service in 2006. There followed upgrades known as Block 20, 30 and 40. The Global Hawk is the size of a commuter airliner (like the Embraer ERJ 145), but costs nearly twice as much. Global Hawk can be equipped with much more powerful, and expensive, sensors than smaller UAVs. These more than double the cost of the UAV. These spy satellite quality sensors (especially AESA radar) are usually worth the expense, because they enable the UAV, flying at over 60,000 feet, to get a sharp picture of all the territory it can see from that altitude, identify objects as small as 30 centimeters (one foot) in diameter with the first two generations of sensors, and is even more capable with the MS-177.