Last updated: 27/07/2011 | 23:24 |  

Unmanned Aircraft Systems

Eli Dotan describes the application of various unmanned aircraft systems (UAS) technologies for securing land borders, and argues the sensor package can be as important as the platform

There can be little doubt that securing land borders has always presented a substantial challenge to most nations. The challenge derives mainly from the size and space of the area to be secured. Short, well-fortified land borders such as Gibraltar are relatively easy to secure, yet almost any border exceeding 50km can become a serious problem, purely due to the limits of surveillance and physical presence. These have often been technically and effectively addressed but usually at huge cost, such as with the inner German border of the Cold War. In Israel’s case, fortifications and obstacles have proven effective where border defence is concerned. Nevertheless, physical barriers can only slow the determined infiltrator if he or she is left un-detected to tackle the obstacle.

Surveillance is usually the key to effective border security, and nowadays unmanned aircraft systems (UAS) are perceived as having a major application in this area. The UAS can be used as the main component of an overall system-level solution to protect the border. It is an instrument, and is a highly effective one if correctly matched to the specific task required. What must be determined is the criteria which defines the most effective selection of a UAS to address the problem. Much of what is known about the use of UAS derives from military operations, yet border surveillance involves distinct challenges that provide an important and relevant change of context.

Borders themselves are not a problem in theory. Their physical nature is what largely defines the problem, however, which stands apart from social, political or economic conditions which people pursue to cross them illegally. Illegal crossing usually means remaining undetected during all phases of the attempt, and usually for a period after a successful crossing. Detecting illegal crossings will not stop the crossing, but it is the first step in doing so. The first challenge is therefore to provide effective surveillance deep beyond the actual “fence line” into the foreign territory. This is mostly and largely overlooked as part of the solution.

There are major legal considerations relevant to operating UAS in close proximity to foreign airspace, just as there is with any aircraft. It is usually not acceptable for an aircraft to cross the border, and the suspicion of aircraft engaging in military surveillance, not associated with border control also has to be considered with regard to its impact on foreign relations. So the first question that must asked is – “can this border be better secured using a UAS?” If you already have effective land-based surveillance of the far side of the border, and that surveillance has the necessary levels of redundancy and reactivity, then UAS may well represent an expensive and unnecessary diversion. If, however, you have a long, sparsely-populated border that represents little impediment to drug smugglers, terrorists and refugees, then this will almost certainly be an area where a UAS can and should be the answer.

A major mistake made during most UAS requisitions is to specify platform performance and not operational needs and sensor performance. A UAS is merely a means of transporting a specific sensor package and a communications system to a point in time and space. Moreover, the sensor package is usually a far higher cost item than the aircraft carrying it, and it usually requires significant training and support. This is not to suggest that the platform is unimportant. In military applications it is usually sufficient to understand the resolution of the sensor as a function of altitude above the target. This is permissible because there is usually little restriction in positioning the platform directly above the target. When it comes to border surveillance, however, the sensor package needs the ability to observe several kilometres across the border, in order to detect suspicious movement with sufficient warning. Slant-range performance of sensor packages is a major concern for border surveillance for this exact reason. It is equally important to be able to do the same on the home side of the border because, while flying the border line, it should be possible to detect both suspicious approaches as well as those who have successfully crossed, but can now be intercepted by ground units. Slant range also vastly increases the search area accomplished by each sensor pass.

Generally speaking, the higher the performance possessed by the payload, the heavier it will be. The heavier it is, the larger the platform needed to position and sustain it. Thus, having an overly capable sensor pack can be just as bad as one that lacks capability. The fact that 99 per cent of border security targets are human beings on foot simplifies the requirement, in comparison to the range of activities the military has to address. The ability to track humans on foot and possibly within vehicles is of major importance to the intelligence operations which aim to disrupt smuggler or terrorists’ networks. The UAS’s ability to do this undetected cannot be overstated. Day/night capability is an obvious and possibly vital requirement to support a 24/7 presence. Sensor performance across the majority of environmental and meteorological conditions prevailing on the relevant border must be factored into the payload selection. The integration of payload and platform, data-link to the ground control station (GCS) is thus a subject of great importance; the selection of a systems’ provider who deeply understand all these sub-systems is essential. In this regard, systems such as Elbit’s LASSO (Large Area Scanning System) provide a unique capability across the range of detection measures required. Operational it is likely to become the benchmark standard for such a capability with the Israeli Defence Force (IDF).

As mentioned, platforms are not un-important, but the primary requirement will usually be to the sensor pack specified according to the mission. Many UAS developed for military missions have a wide range of launch and recovery options required by military operations. Border surveillance UAS should normally be operated from a fixed base. This can greatly simplify planning and operations, as well as lowering the cost of operation. The desired, safest and lowest cost method of UAS TOL is automatic take-off and landing, for which the operating surface should ideally be located far from controlled airspace and be dedicated to UAS use. Indeed, TOL from a facility employing a mix of manned and unmanned aircraft may be more difficult, although it is possible. 

Another important factor is speed and endurance. Strong winds can hamper UAS operations to some degree, so the platform needs to be large and powerful enough to address extant wind conditions in the area of operation. Speed is also important in addressing the effectiveness of search repetition rate. This is what separates a UAS platform from a ground-tethered aero-sat balloon. The UAS scanning along a certain border line has to take into account that any area must be revisited at regular intervals to avoid long periods of no-search during which time people could seek to cross the border. As a human on foot can easily move at 3-5kph, there is a reasonable chance they might escape detection unless the UAS can aim to detect humans on foot a few kilometres from either side of the border. The platform’s speed is also important when it is required to support ground units in a search, once a successful crossing has been detected by whatever means. Again, speed and ability to get on station quickly and effectively, and then re-deploy back to the task, is important, as is the ability to stay airborne for an effective period of time. That may be for 15 hours or more.

These requirements pretty much exclude small, low-cost tactical UAS from consideration, and strongly suggest platforms such as Elbit’s Hermes 450 or Hermes 900. Arguably, the higher performance UAS are capable of a presence or persistence that one could not reasonably expect from a fixed wing aircraft or helicopter. That persistence and endurance across a wide variety of weather conditions is the clear advantage that a UAS brings over manned platforms. For longer missions, UAS staff can be easily replaced with the next shift.

The larger platforms can also accommodate more than one sensor package, so understanding the overall systems approach from the outset is critical. You may want to have two or three UAS patrolling a section of the border, so command and control is best accomplished by jointly controlled systems where UAS operators are located in the same ground station and can switch control of platforms and sensor packs between them as situations unfold. Successfully controlling more than one UAS, each of which may have two sensor packages gathering different types of data, requires a good deal of expertise and specialised equipment. This is an approach pioneered by Elbit Systems and it has become particularly relevant when employing systems such as LASSO or any mix of sensor packs.      
           
UAS will therefore provide an effective solution to certain border surveillance problems only when properly used as part of system-level approach. A detailed understanding of both the advantage and limitations of the UAS approach are therefore required. This means understanding both the performance of the platform and the sensor as being equally important, and based on a solid understanding of what you need the system to do. A company that can provide a range of payloads and platforms as a systems house is usually the best choice in this regard, as well as one with the relevant experience of certification processes and having addressed similar challenges. UAS border surveillance will almost certainly require a bespoke solution that will require a very wide range of UAS expertise, so single or double platform providers are unlikely to able to address the requirement effectively. A systems approach based on deep understanding and experience is the path most likely to provide a valid, robust and cost-effective solution. 

Eli Dotan, is Senior Business Development Director at Elbit Systems’ UAS Division. He joined Elbit Systems in 1992 and has held various senior system engineering and business development positions relating to UAS. Prior to that, Mr. Dotan led the development of large-scale C4I systems.