April 6, 2022:
In early 2022 Israel put its first Sky Dew aerostat (aerodynamic unpowered blimp) system into service along its northern border, to detect Iranian air attacks using low, slow UAVs equipped with explosives and a GPS guidance system programmed to head for specific targets. Sky Dew carries radars and other sensors to monitor large land areas for low, slow intruders. Another Sky Dew may be installed in the south, along the Gaza border, where the threat is less but may get worse because the Sunni Arab Hamas that rules Gaza is once against a recipient of Iranian military and economic aid.
Sky Dew specifications were not revealed, apparently because it uses new sensors that can detect a lot more threats at greater distances and lower altitudes and speeds than previous systems could. Iran has been developing new aerial threats designed to get past many current air defense radars so not letting Iran know exactly what Sky Dew is capable of will give Iran a more difficult time evading it.
Sky Dew is not the first Israeli aerostat system. In 2005 an Israeli firm introduced a smaller aerostat system; the ELM 2083 that was a substitute, in performance, to an American AWACS (Air Warning and Control) aircraft. This aerostat was designed to spot aircraft up to 500 kilometers distant and at low and medium altitudes. Unlike Sky Dew, ELM 2083 was less effective at detecting very low and slow threats. ELM was purchased by Israel, India and Singapore.
Modern aerostat systems have been around since the 1980s and have proliferated as more compact, lightweight and powerful sensors became available. Aerostat systems use a 100-250 foot long, helium filled, unmanned blimp equipped with radar and other sensors. The larger of these blimps are more than twice the size as the more familiar advertising blimps. An aerostat is designed to always turn into the wind and stay in the same place. An aerostat is unpowered, and secured by a cable that can keep the aerostat in position at its maximum altitude of 4,700 meters (15,000 feet). At that altitude, a large aerostat can carry a two-ton payload. The cable also supplies power, which means the blimp can stay up for about 30 days at a time before it has to be brought down for maintenance on its radars. Often, two radars are carried. One is for surveillance; the other is a precision track and illumination radar (PTIR). The surveillance radar provides long-range coverage (400 kilometers or more), while the PTIR, which is a steerable system capable of tracking multiple targets, can focus on items of interest. Current aerostats carry a larger array of more capable sensors.
Aerostat systems cost varies from under $10 million, to over $100 million each, depending on the size of the aerostat and the capabilities of the radar and other sensors. Aerostats work. Kuwait had one in 1990, and the ground radar spotted the Iraqis as soon as they crossed the border. The U.S. uses dozens of aerostat systems in Iraq and Afghanistan to guard bases.
One example of the new generation of sensors for aerostats and UAVS is the U.S. Army Starlite radar, which has been in use for over a decade. The AN/ZPY-1 Starlite lightweight radar weighs 29.5 kg (65 pounds), occupies 34 cc (1.2 cubic feet), uses 750 watts of power, and costs about $2.3 million each. Starlite can deliver photo quality black and white images of what is down there, in any weather. The army has developed software that enables the Starlite images to be transmitted to existing army video terminals and automatically appear on electronic versions of standard army maps. Starlite is used in combination with vidcams and heat sensors (infrared or thermal). The Starlite software enables the operator to quickly, or automatically, point a video camera at anything the Starlite can see.
The Starlite was originally designed for use in the army's 1.5-ton MQ-1C Sky Warrior UAV. While UAVs get more publicity, the army has found that its aerostats and tall towers also make good use of Starlite and do it a lot cheaper; under $1,000 an hour, mostly for maintenance, repairs, and personnel to monitor the sensors, and stay airborne nearly all the time. Compare this to Sky Warrior or Predator, which costs $6,000 an hour to fly. The stationary Starlites just need a way to keep an eye on a large area; like chunks of the Syrian, Iranian, or Pakistani border or the area surrounding a base 24/7.
Starlite thus became another component of the PTDS (Persistent Threat Detection Systems) that are mounted in the aerostats or towers. PTDS was developed because of the fighting in Iraq and Afghanistan. In 2004 the U.S. Army sent 22 aerostat systems to Iraq and Afghanistan. The most common model of aerostats float at about 330 meters (a thousand feet), tethered by a cable that provides power and communications to the day and night cameras, or Starlite radar, up there. The big problem was ground fire from rifles and machine-guns. Hostile gunmen liked using the aerostats as targets. Rifle fire would not destroy the aerostats but did cause them to be brought down more frequently for repairs. Normally the aerostats can stay up for 30 days at a time but the bullet damage repairs have some of them coming down every few days. The PTDS surveillance systems mounted on tall steel towers also suffer gunfire damage but rarely any that disables the equipment.
The first army aerostats went to Iraq to help defend offshore oil facilities from attack by terrorist speedboats. Those early systems used a 75 meter (233 foot) long, helium filled, unmanned aerostat equipped with radar and other sensors. The U.S. Navy operated aerostat systems from ships to spot small boats over a large area around the vessel. Larger aerostats, like JLENS, were originally designed to detect cruise missiles and were soon replaced by smaller and cheaper aerostat systems currently in use.
Israel worked with American aerostat developers and equipment suppliers to develop Sky Dew.