Space V Airborne ISR – or Mix and Match

Hawkeye 360 Cluster 2 satellite (HawkEye 360) As of early 2021, U.S. contractor HawkEye 360 had launched two constellations of RF emitter detecting CubeSats. Shown here are the three vehicles that made-up the company’s second constellation which was launched on 24 January 2021

Owning satellite based ISR for military use is still an exclusive ‘club’, but airborne ISR still provides that most countries need.

Until relatively recently, satellite-based intelligence, surveillance and reconnaissance (ISR) was restricted to an exclusive club that was made-up of the world’s technological and military ‘superpowers’. Here, security considerations, enormous cost and the sheer difficulty in placing something like a 19.5 metre long KH series imaging satellite in orbit ensured the exclusivity of the ‘club’. For those able to capitalise on the technology, the rewards were (and are) enormous, with an American Lockheed KH-11 Kennen/Crystal system being postulated as having a six centimetre ground sampling distance from an altitude of 155 miles (250 kilometres). Again, orbiting satellites have been relatively invulnerable to attack (although America, China and Russia have all looked at anti-satellite technology over time), offer global coverage and total persistence until orbital decay sets in when their power and fuel supplies are exhausted. In this latter context, it is interesting that America’s Space Shuttle was developed partly as a re-usable ‘service station’ to keep the country’s in-orbit fleet of imaging and signals intelligence (SIGINT) satellites operational for as long as possible.

For those countries outside this ‘charmed circle’, air vehicles offer a much more affordable means of collecting ISR data. As much as anything, this has been driven by developments in sensor and business aircraft technology that today enable aircraft such as Textron Aviation’s King Air turboprops or Gulfstream ‘bisjets’ to carry sensor suites that can include surveillance radar, electro-optical (EO) and infra-red (IR) imagers and signals collection equipment in a unified whole. Again, advances in communications technology allow such platforms to deliver real-time data to remote control/analysis/dissemination centres using high capacity line-of-sight and/or satellite links. To such manned platforms, we can now add unmanned aerial vehicles (UAV) that can range in size from hand-launched to behemoths such as the Northrop Grumman Global Hawk. Not only do these provide the whole gamut of sensor types (with carriage being dependent only on available space and power) but also at the highest end of the scale, persistence measured in days. However, those behind the technology seem to be on the cusp of creating operationally viable high altitude pseudo satellites (HAPS) that are capable of lifting a variety of payloads (including imagers) to very high altitudes for very long periods of time. By way of example (and because it is one of the few HAPS that have been described in other than general details), the Prismatic/BAE PHASA-35 vehicle is designed for surveillance, communications, remote sensing and environmental science applications and is specified for operations at altitudes of between 55,000 feet – 70,000 feet (16,700m-21,300m) for up to a year at a time at latitudes of up to 35 degrees. Power is provided by a configurable GaAs solar array and Li-ion battery packs and the air vehicle can accommodate a 15kg (33lb) mass payload. Here, 300-1,000 Watts of continuous DC power is offered. Again, PHASA-35 requires no dedicated launch and recovery facilities, with launch being ‘automatic assisted’ and recovery being ‘automatic glide’. PHASA-35 made its first flight on 17 February 2020 and as of late January 2021, flight trials in the US were planned. Overall, co-developer BAE bills that type as being a “persistent and affordable alternative to satellites” that is “combined with the flexibility of an aircraft”.

Vehicles such as PHASA-35 are not the only alternative to dedicated ISR satellites, with commercial imaging satellites such as NASA’s Landsat series and the European Space Agency’s (ESA) Satellite pour l’Observation de la Terre (SPOT) family providing ‘entry level’ experience of satellite surveillance. The first generation SPOT 1 satellite was launched during 1972, with (by way of example) the 1998 vintage SPOT 4 vehicle (which reached the end of its useful life in June 2013) orbiting the Earth every 101 minutes at a height of 516 miles (832km) along a near-polar, sun-synchronous path. Again, the satellite re-visited the same spot on the Earth’s surface every 26 days, offered high-resolution visible and IR resolution of between 32-65ft (10-20m) and over a swath of 60x60km (37×37 miles). In the latest SPOT 6 and 7 vehicles, the ESA claims a resolution of between 5-19ft (1.5-6m) over a 60km (37 mile) swath from an altitude of 431 miles (694km).

An artist’s impression of the Prismatic/BAE Systems PHASA-35.

For its part, the NASA/US Geological Survey Landsat programme began during 1972 and in its Landsat 9 incarnation, is equipped with the multispectral Operational Land Imager 2 and Thermal Infra-red Sensor 2 instruments, orbits at an altitude of 438 miles (705km), covers the Earth every 16 days, generates more than 700 images per day, has a 114 mile (185km) swath and a pixel resolution of 98ft (30m). While neither SPOT or Landsat were intended for anything other than environmental surveillance, both deliver high-quality imagery and accurate geolocation, with Landsat in particular contributing to a portal that is available to anyone with a laptop or personal computer and which offers a level of resolution that is good enough to identify the types of aircraft on airfields that have been imaged. This said, such imagery, while interesting as background open-source material, in no way meets requirements for, say, real-time, targeting grade material. This said, the market for commercially generated ‘pay for view’ satellite derived data is said by one contractor to already stand at about $5 billion per year, with a customer base that includes defence agencies, shipping companies, environmental groups and the World Health Organisation (WHO) amongst others.

A screen shot of a Landsat image of the American city of Boston that was captured from a personal computer application and which shows something of the detail such images can show.

Signals Collection

A most interesting aspect of this ‘pay for service’ concept is its evolution into radio frequency (RF) signals collection based on constellations of CubeSats. Defined as vehicles that range in size from less than 0.1kg (0.2lb) (Femtosats) to 1,000kg (2,204lb) (Minisats), CubeSats can easily be packaged in multiples aboard a single launch vehicle, can be ‘piggybacked’ on the launches of larger payloads and are cheap (when compared with traditional satellite technology) and quick to build. Exemplars in the field are American contractor HawkEye 360 and the Luxembourg-based Kleos Space, with the former having gained U.S. Federal Communications Commission authority to launch up to 80 satellites over a 15 year period in order to maintain a constellation of 15 operational spacecraft.

To date, HawkEye 360 has launched six satellites, with the second constellation of three being deployed from a SpaceX Falcon 9 launcher (via a Spaceflight Sherpa-FX orbital transfer vehicle) on 24 January 2021. Functionally, the current generation of HawkEye 360 satellites incorporate software defined radios that cover the 144 MHz to 15 GHz frequency band and employ the time and frequency difference-of-arrival techniques to geo-locate emitters with 95 percent probability of success. Again, potential targets are listed as including very high frequency (VHF) marine communications, ultra high frequency (UHF) push-to-talk radios, L-band mobile satellite devices, X- and S-band marine radars, Automatic Identification System (AIS) transponder and emergency radio beacons. Alongside the satellites themselves, HawkEye 360 has also created a portfolio of data analytics products that include RF emitter identification and geolocation (RFGeo), the identification and tracking of maritime emitters of interest (SEAker) and signal density mapping of selected frequency bands in a specified region (RFMosaic). HawkEye 360 also released a commercial RF analysis platform (Mission Space) that aggregates the portfolio of data products into an intuitive application to better visualise and interpret RF data to achieve actionable insights.

“Our growing constellation is a breakthrough for space-based commercial ISR. Customers have shown an insatiable appetite for more RF data and insights, and the launch of Cluster 2 allows us to meet that demand. As we continue with our three additional planned launches this year, our collection capacity and speed of delivery will scale rapidly,” said HawkEye 360 CEO John Serafini.

For its part, Kleos Space launched its first cluster of four satellites aboard India’s Polar Satellite Launch Vehicle C49 which lifted off from that country’s Satish Dhawan Space Centre on 7 November 2020. Placed in a 37 degree inclined orbit, the constellation had been successfully commissioned by the end of the month and was so positioned as to be able to collect data from areas such as the Strait of Hormuz, the South China Sea, East and West Africa, the Sea of Japan and along Australia’s northern coast. Designed to provide ‘RF reconnaissance data as a service’, the Kleos constellation (like its HawkEye 360 counterpart) uses software defined radio technology that are initially targeted at emitters in the VHF band, with geolocation being by means of the time difference-of-arrival process. The emergence of contractors such as HawkEye 360 and Kleos Space means that potential customers now have access to both commercially-based ‘pay to view’ imaging and RF collection satellites with which to meet some or all of their surveillance requirements.

Airborne ISR

While space-based ISR may becoming more accessible, the provision of ISR capabilities for most countries remains vested in air vehicles (be they manned, unmanned or of the aerostat type) and SIGINT equipment deployed by army/para-military units and aboard ships. Airborne ISR remains a very popular choice as it increases line-of-sight coverage, is flexible in terms of deployment, employs (for the most part) man-in-the-loop modes of operation, is difficult for an enemy to predict when surveillance is likely to take place (the predictability of orbital mechanics being a particular Achilles Heel of ISR satellites), is not weather dependent (visible light satellite imaging cannot see through or avoid cloud cover) and is much more affordable. Again, pre-wiring a number of aircraft to take cross-decked equipment keeps costs down even more (fewer expensive sensors to procure) while ensuring that the capability is rarely ‘grounded’ due to airframe failure. Further benefit can be obtained from the use of the newest generation of corporate aircraft where intercontinental range is possible with the latest ‘bizjets’, pre-used airframes are widely available for cost effective conversion, a sufficiently large power/space envelope is provided to accommodate suites of sensors and their operators and the use of basically civil airframes means that it is possible to outsource airframe and engine maintenance to existing, type-rated civil contractors.

By way of illustration, the widely-used King Air 350 turboprop business aircraft is a good example. At the time of writing, ISR King Airs were probably one of the most widely used military/para military airborne ISR platforms in the world, with a typical high-end sensor suite carried by such aircraft being illustrated by the French Customs Service’s (Douane Française) fleet of six King Air 350ERs. Here, each aircraft is fitted with an AIS application, a tactical datalink, a 30-410MHz DF-430 direction-finder, an IR/ultra-violet scanner, an 8-10GHz Ocean Master 400 maritime surveillance radar, a 9,375MHz centre frequency side-looking airborne radar, a SAFIRE III HD EO/IR imager and a SAMSARA 200 mission management system. Again, many such fits add some form of SIGINT capability, with the whole offering a unified package that can be used for a wide variety of tasks including border patrol, anti-piracy patrol, counter insurgency operations, illegal immigration monitoring, anti-drugs patrol and environmental monitoring. While not wholly military in nature, paramilitary capabilities of the kinds described are becoming increasingly important in an increasingly unstable world.

Textron Aviation’s King Air 350 business aircraft is one of the world’s most popular airframes for conversion into specialised airborne ISR platforms. Shown here is a King Air 350ER ISR aircraft that was produced by Swiss contractor Corporate Aircraft for an un-named North African customer. As such, F-WTAI has been fitted with an X-band Gabbiano T200 surveillance radar, an EO imager, an AIS application and Leonardo ATOS control system application

While air vehicles are a good fit for the ISR collection role, their biggest downside is their vulnerability in contested airspace which, in large part, restricts them to benign environments and/or stand-off operations if opposition is likely. The potential cost (financial and political) of losing manned ISR aircraft has obviously been a major driver in the rise of UAVs for surveillance. If a UAV is lost, it is not catastrophic and the ‘throw away’ (used advisedly!) nature of the technology means that it can penetrate areas that would be otherwise closed off. As hinted at earlier, UAVs can range from hand-launched examples that are fitted with a simple EO imager and a downlink to increasingly more sophisticated platforms that can (like their manned counterparts) carry suites of sensors. An example here is Israel Aerospace Industry’s (IAI) widely used Heron medium altitude long endurance (MALE) that can be outfitted with up to six payloads drawn from a range that includes high frequency/VHF/UHF communications intelligence receivers (including an anti-GSM telephone capability), electronic support measures equipment, laser range-finders/designators, EO/IR imagers and synthetic aperture/moving target indication radar, with the whole being backed-up by line-of-sight and satellite communications links. Again, Heron is advertised as having a beyond line-of-sight range of better than a 621 miles (1,000km), a service ceiling of better than 35,000ft (10,668m) and an endurance of up to 45 hours.

Looking for all the world like a model aeroplane, the 1.02m wingspan AeroVironment Wasp UAV is hand-launched, is equipped with a Mantis i22 EO/IR payload and has a range of over three miles (5km). Overall UAVs (as opposed to commercially available hobby drones) can range in size and capability from nano-drones through Wasp-sized vehicles to multi-sensor platforms such as the Global Hawk which has a wingspan that is similar to that of a Boeing 737 airliner.

What then (if anything) does the foregoing tell us about the relationship and relative merits of airborne and space-based ISR? The main take-aways would seem to be that the two are complementary, that the use of high-end satellite surveillance will remain a very exclusive club and that the new generation of ‘pay for view’ satellite capabilities will find increasing niche acceptance. Perhaps the paradigm for the increasingly vital field of ISR is that the future is ‘mix and match’, with end users defining their needs and taking advantage of a range of options with which to meet them. Such a future might see a judicious mix of ‘pay for view’ satellite services, manned ISR aircraft and surveillance UAVs, with the mix having the facility to be reasonably rapidly re-configured to meet specific objectives as the arise.

by Martin Streetly