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As an ICEYE satellite orbits Earth, its transmitted radar signal waveforms focus on a defined area of the surface to create a persistently generated image for up to 25 seconds 鈥� twice as long as competitors. Due to its increased duration in imaging mode, users can better determine the shape of an aircraft's fuselage, wings, or engines, while civilians may recognise narrow objects such as ship outlines and antennae. ICEYE鈥檚 recent 鈥楶eoples鈥� Satellite鈥� operating over Ukraine provides information on damage to civilian infrastructure, and strategic intelligence of benefit to littoral military strategists. It is even possible to provide short 鈥榲ideos鈥� due to imaging persistency over designated 鈥榯argets鈥�, composed of consecutive multiple images acquired during image collection.

ICEYE builds upon established electro-optical data products provided by companies such as Earth-I [6], permitting not just vessel identification but detailed analysis of vessel movement, direction, and speed, which can be cross-correlated against satellite-enabled automatic identification systems (AIS) data layers. The coherency of image data also permits significant improvements in signal/noise assessment. Radar antennae are controlled by software to direct radar beams to specific areas of interest as needed 鈥� similar to current terrestrial, sea and air military phased array radar [7] across sectors 鈥� and provide versatility in imaging modes, ranging from fine resolution to broad views covering tens of thousands of square kilometres. Images can be taken from a wider range of view angles than previously and can better perceive objects through 鈥榞aps鈥� between trees and foliage, which otherwise may be missed.

ICEYE is currently operator of the world鈥檚 largest constellation of SAR satellites, but it will have to work hard to preserve its market lead in a growing yet competitive market for Earth observation, persistent monitoring, and natural catastrophe solutions, increasingly integrated with communications. This area attracts interest from governments for defence and civilian 鈥榙ual-use鈥� for next-generation SAR spacecraft. Potential maritime applications include: ISR [8], illegal migration [9], ice monitoring [10], illegal fishing [11], and illegal goods [12]. Other surveillance roles include detection of threats by satellite imaging, or RF detection, to address anti-terrorism, port and offshore security, autonomous navigation, and land applications. Threats include jamming EMP direct satellite destruction, bomb or kinetic, or laser-based weapons [2] (Figure 2).

Statistics for 2012鈥�2021 (released June 2023) show that in 2021, the US space economy accounted for US $211.6B gross output ($51.1B privately generated) and employed 360,000 private industry jobs [13] (Graph 1).

A substantial number of existing military satellites are also nearing the end of their operational lives, previously with high development and operational costs, and long construction cycles. For example, a global position system (GPS) IIR satellite costs c.US $500M to build and a further $510M to launch [14]. Military planners are exploring a range of cheaper options for modern satellites, including technological upgrades and new launch techniques. Nanosats and other small satellites offer potential solutions if developed quickly, at low cost and in numbers that facilitate not just threat resilience but redundancy against multiple satellite failure, with most of the capabilities of traditional military systems available to civilian users.

The replacement of out-of-date larger satellites with a generation of smaller, more cost-effective solutions using private company platform architectures exploiting similar civilian markets is attractive. If satellites can be replaced rapidly, resilience is increased, which is a key factor for today鈥檚 military planners. Resilience incorporates redundancy with the provision of other linked systems via rapid repopulation of depleted space assets. In 2018, Stephen Hiller, UK Chief Marshall of the RAF, stated, 鈥淭he prospect of cost-effective constellations of small SATS being built, launched and replaced quickly is highly exciting, providing us with the resilience we seek.鈥� [2, 15鈥�16].

Reduced launch requirements have resulted in some 60 nations developing commercially viable space-based sensing and telecommunications capabilities with the functionality of larger satellites but at much reduced cost, while full-sized satellites cost from 拢200M to 拢1B. CubeSats, by comparison, cost well under $1M; Elon Musk, SpaceX CEO, has recently stated that Starship launch costs are now about $200 per kilo [17]. The Defense Advanced Research Projects Agency (DARPA) and the US government are exploring innovative platforms for dedicated military missions, an attractive alternative to current expensive systems and architectures for short tactical missions. Small satellites have lower development and launch costs as well as shorter development and production timelines to provide the latest end-user capability options to civilian areas such as Earth observation and humanitarian monitoring. Future nanosats and CubeSats weighing under 5 kg currently cost 拢300,000鈥�500,000 but may be launched from high altitude jets or balloons rather than traditional rockets, adding to the 2500+ nanosats and 2300+ CubeSats currently in orbit, with over 2,000 more planned in the 2022鈥�2027 timeframe [www.nanosats.eu].

Military demand for commercial satellite imagery is well established. The US Army exploits nanosats with dedicated coverage for multiple users in remote hostile areas. Many countries use this option, as it is possible to purchase satellite photos from commercial operators with 鈥榙ual-use鈥� technology operating in the 鈥榞rey zone鈥�; however, satellites which provide both civilian and military may be seen as legitimate military targets, whose loss would impact civilian users, especially those in remote isolated communities.

Military operational requirements routinely obtain 40鈥�50 cm optical resolution from civilian satellites; such high-resolution cameras are also relevant to earth observation. The value of military imagery depends on system resolution, while the imagery鈥檚 tactical value depends on timelines. In other words, imagery collection and processing in near real-time makes targeting and situational awareness possible. Processing capabilities are fundamental, making them equally relevant to time-constrained humanitarian and emergency applications, such as Coastguard requirements.

Persistency, defined as the ability to provide continuous maritime and littoral surveillance of a chosen area for a required period, is a high requirement for the downstream satellite community; temporal requirements are also important to observe maritime activities. The overall customer opinion is that it is essential to secure timely access to space without necessarily owning the space assets to acquire the required data and generate derived data layers.

Low-cost nanosats have a 2鈥�3-year design expectancy and reliability; they don鈥檛 require redundancy for long-life, nor do they need to survive harsh space weather, as they can be replaced. Nanosats have short, low-cost cycles, providing persistence and resilience in the most rapidly changing space sector. Most military commentators recognise that there is a new nanosat international 鈥榮pace-race鈥� driven by revolutionary and adaptable electronics technologies and new innovative launch providers. Nanosats provide solutions for tactical applications, meeting the stringent requirements of night鈥揹ay operations, persistency, all-weather capabilities, etc., for tactical operations using short timescales. SAR is one possible capability solution for replacing larger satellites. Many market players stress the trend towards smart data analytics, with hybrid optical-SAR, providing tailored information for customers, improving SAR utility and earth observation data simultaneously, derived from combining small high-resolution optical systems with large high-resolution SAR platforms. This architecture will support future commercialisation of civilian space-based very high-resolution SAR, likely in consortia composed of multiple partners.

With ever more satellites in the 1鈥�10 kg category, and the price of high-resolution satellite imagery dropping, remotely gathered images are increasingly used by the UN and NGOs to investigate allegations of human rights and environmental abuse. The commercial availability of high-resolution imagery facilitates investigations of recent dramatic social events, including the destruction of homes in Sudan [18] and Zimbabwe (Figure 3) 摆19鈥�20闭 and the environmental effects of the notorious Rio Tinto gold and copper mine in West Papua [21].

In May 2005, President Mugabe鈥檚 Zimbabwe government began a campaign 鈥� Operation Restore Order 鈥� in which homes were systematically demolished. Images were taken after the estimated 6,190 residents of Porta Farm were driven from their homes. Gathering information in such places is dangerous; journalists were killed trying to approach the Rio Tinto mine, and aid workers were targeted as they flew into remote areas in Sudan. Satellite imagery means we can observe what is happening in such areas without risking lives unnecessarily.

One ongoing problem is the reporting of accurate locations, often confused in reports. However, once a place has been located, NGO analysts aim to acquire a set of 鈥榖efore and after images鈥�, which they compare for evidence [22]. However, in response to urgent humanitarian abuse claims in remote areas, this isn鈥檛 always possible and takes no account of the skies being cloudy above. The requirement for highly detailed satellite imagery that is globally available 24/7/365 has driven satellite data providers to reassess the ways in which they conduct their operations. Although optical sensors provide satellite imagery today with typically 50 cm resolution, they are limited to daylight hours and may be restricted by poor weather, smoke and battlefield obscurants.

The preferred tactical solution is imaging radar, operating under darkness and despite challenging battlefield or environmental conditions. The potential commercial market is significant, with 30 proposed satellite radar sensors planned for launch, as imaging radar can create images of ships, vehicles, and aircraft, and may be mounted on platforms such as aircraft or satellites. Current commercial drivers look to provide increasing improvements in resolution and component size, with better foliage penetration, improved strip, scan and spotlight modes, and rapid data products from imagery acquisition to delivery. Existing large SAR system manufacturers have a head-start in experience over small startup companies, but significant cost reduction will require a shift in operational mindset. Small startup companies can move faster due to their small but agile business structures and project pipelines to potentially outcompete larger market players such as Airbus.

If a vehicle convoy drives over a dirt track at night, ground can be compacted by several millimetres, so its path is seen with SAR, which can also detect changes due to water, mineral, oil or gas extraction. China has entered the strategic vehicle monitoring SAR market with Gaofen-3, a three-tonne C-band SAR satellite officially for natural disaster monitoring, working in conjunction with the Chinese High-resolution Electro Optical System (CHEOS) network, providing near real-time imaging data to government agencies with 12 modes and 1m resolution [23]. But such large Chinese SAR systems are some way off from becoming small, easily deployed tactical systems. However, this will change as SAR is a strong growth market area, particularly for maritime persistent stare and satellite imagery.

The next generation of military grade tactical nanosatellites offers possible provision of 鈥榩erishable鈥� information for civilian and UN observation activities; certainly, Darfur in Sudan would have benefitted from this technology. Today there are few areas of the globe beyond the long reach of such satellites, whether electro-optical or radar, combined with international law. But information must be acted on in a timely fashion, otherwise it remains just highly 鈥榩erishable鈥� information. From a UK commercial perspective, there are many questions that need answers, such as 鈥榟ow is space data used today in multiple markets?鈥�, or 鈥榟ow could the UK use its industry to contribute to global needs and understanding?鈥�, or finding what scientific research data gaps exist in the market for space maritime data.

Multilayer 鈥榙ual-use鈥� surveillance emphasises passive RF detection from space, maritime AI target detection and identification, hyperspectral imagery and SAR, utilising vessel detection methods for both cooperative and uncooperative vessels. Some large companies will likely incorporate all these methods into a mission architecture composed of high Low Earth Orbit (LEO) and low LEO elements, e.g., high LEO passive Radio Frequency (RF), with low LEO active RF and low LEO hyperspectral. Low LEO provides opportunities for small SAR systems. Multi-layer maritime surveillance constellations provide opportunities for global coverage, while low LEO provides repeated ground track patterns coverage, useful to the UK鈥檚 larger waters鈥� border security monitoring. There are potential applications for active and passive payloads, and competitive players in space-based maritime domain awareness; companies like Space X, Blue Origin and Virgin Galactic made up 80% of the US Space economy in 2021 [24].

Although the US government has increased military spending, today鈥檚 space economy encompasses not only space platforms, but large earth facilities, hardware, software, devices reliant on space such as GPS-enabled mobile phones, space training courses and education. With growing international space competition, the US government spent over $40B in 2017 compared with $2B by Russia, with most of the top private space companies based in the US, e.g., Boeing and Space X, who publish twice as many papers as China. However, China鈥檚 national priority is to overtake the US in terms of space by 2045, confidently asserted with the recent launch of its Tiangong space station [25], and aims to put people on the moon and Mars; Asian rival India is also expanding its space economy with some recent 140 space-tech startups.

Even relatively small countries have joined the growing list of actors; for instance, C么te d'Ivoire has planned its first launch, YAM-SAT-CI 01, for late 2024鈥�2025 to provide earth observation data for issues from deforestation to national security, in a collaboration between private and public sectors, supporting environmental monitoring, agriculture, disaster response detecting illegal activities [26]. This launch sits within the context of significant African space economy growth, reaching $22.64B US by 2026, and 15 African nations now have functioning space programmes, with over 100 other satellites planned to launch by 2026.

On the high-end military satellite side, Lockheed Martin (LM), as part of its commitment to launch three satellites to advance Joint All-Domain Operations, has announced that its Pony Express 2 (PE2) mission, intended to showcase how space can enhance combined Joint All Domain Command and Control (JADC2), and is ready to launch [27]. PE2 uses a pair of small satellites integrating four LM payloads on two 12U Terran Orbital Renegade-class space vehicles, building upon Pony Express 1, which set the benchmark for a new era of space-based computing, enabling artificial intelligence with data analytics, cloud networking and advanced satellite communications on its experimental nanosatellite payload. PE2 will provide tactical communications systems, a Ka-band crosslink and mesh network, precision relative ranging and time synchronisation with a high-end CPU-processor to demonstrate enhanced connectivity, autonomous capability, mission flexibility, agile operations and AI application to autonomously monitor space craft telemetry with prediction diagnostics of potential failures faster and more accurately than humans, and the ability to proactively address these problems.

The overall development opportunities of nanosatellites are very good, having strong military support, and also providing broad 鈥榙ual-use鈥� capabilities. Rapid advances in technology and launchers means launch costs and timescales are still falling while capabilities are increasing, promising rapid deployment and constellation replacement, with new and old companies competing stiffly to win contracts, and many nations accessing space for military and civilian activities for the first time, while others are accessing space capabilities without owning the space assets and the inherent risks that such ownership creates.