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The Centre for Land Warfare Studies (CLAWS), New Delhi, is an independent Think Tank dealing with national
security and conceptual aspects of land warfare, including conventional & sub-conventional conflict and terrorism.
CLAWS conducts research that is futuristic in outlook and policy-oriented in approach.
Website: www.claws.in Contact us: landwarfare@gmail.com
No. 324 January 2022
HAPS: An
Untapped Force
Multiplier
Lieutenant Colonel Vivek Gopal ,
was born in March 1980 & hails from
Punjab. He received his B.Sc
(Electronics) Degree from JNU, Delhi in
the year 2000 after graduating from the
National Defence Academy.
Commissioned in December 2000, he
received his B Tech (Electronics) from
JNU in the year 2007. The officer went
on to complete his M Tech (Electronics
Engineering) from JNU in the year 2011.
A paratrooper, the officer has worked in
varied specialised units in operational
areas. A Certified Project Manager, he is
also a member of various prestigious
organisations. A technology evangelist,
he is pursuing his M Phil in Defence &
Strategic Studies. Presently, he is
posted as ‘Instructor’ at a premier
training establishment.
Abstract
Recently, there has been an increasing focus on
new technology, such as tactical satellites or
high-altitude long-endurance airships, as means
of increasing communication and intelligence
collection capabilities. Similar advances in the
capabilities of medium-altitude and high-altitude
unmanned aerial systems have resulted in their
enhanced role in today’s battlefield. Each of
these vehicles has a unique niche in today’s
military, but the increasing capabilities of each
are beginning to create substantial overlap in
their use.
This brief is an attempt to address how the
potential of ‘High-Altitude Platform Systems
(HAPS) or Pseudo-Satellites’ can be leveraged
for optimal gains in various domains to ultimately assist the war fighter in execution of
Key Points
• HAPS is
an important technology
waiting to be leveraged―presents
multiple use-cases.
• The areas where HAPS scores over
satellites are cost, footprint,
persistence over target area.
• Challenges in terms of station keeping
and envelope material. Trade-
off of
endurance vs payload weight.
•
India need to have an Operationally
Responsive Trans Troposphere
(ORTT) initiative and mandatory
strategy in place to leverage HAPS; it
should also be linked with the Space
domain.
• HAPS should be significantly used for
communication,
ISR, Electronic
Warfare, provision of PNT signal as
an alternate to GPS in degraded
environment.
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operations. In the era of dual-use technology, while HAPS have a prominent role to play in
civil applications, the scope of this paper is restricted to military use cases only. The current
investment in medium altitude, high altitude, and tactical space persistent ISR has been
overshadowed with the use of drones & CubeSats. Although, they have their own inherent
advantages, however, there is a need to address the benefits accrued from using HAPS and
thereafter develop an overlap of capabilities to build in redundancy as well as persistent
coverage of the area of interest.
Introduction
A viable question that arises is the purpose of bringing to fore the requirement of deliberation
on High Altitude Platform Systems (HAPS). Open Source literature on the subject and
aerospace technology oriented manufacturers have often discussed the civil use scenarios
of HAPS. However, with sensor and payload technology growing exponentially,
miniaturisation has ensured that HAPS gets to the top rung among discussions of aerial
platforms to be used operationally by the forces. HAPS are also very lucrative when it comes
to resolving high bandwidth requirements for the forces apart from being an alternative to
costly platforms.
Airships or the Zeppelin1 concept has been used historically for the purpose of scouts and
bombing. However, in 1937, the Hindenburg disaster2 saw the demise of these ‘airships’.
The focus shifted to aircrafts and more reliable aerial platforms (unmanned systems and
drones) for military purposes. Satellites placed in various orbits have been extensively
utilised to cater to the requirements of strategic importance, be it Intelligence Surveillance &
Reconnaissance (ISR) or communications. The scope has also engulfed anti-satellite
weapons to a large extent. Earlier, being the sole domain of a select few nations, the rising
space- faring nations have delved into the use of nanosatellites or CubeSats, extensively
attributed to the lower cost per launch for the latter. The cost to design, maintain and control,
apart from launch costs, forecloses the requirement of satellites as dedicated platforms for
standalone use-cases. Transition from expensive satellites to miniaturised tactical small
satellites has resulted in a change in monitoring the tactical battlespace. Unmanned systems
(drones and UAVs) have also been utilised to meet mission specific requirements with
counter unmanned aerial system (c-UAS) technology playing catching up and forcing its
hand to look for better alternatives. There is hence, an inescapable requirement of HAPS
infield platforms that are economical and meet the mission requirements for a specified
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period. ‘Operationally Responsive Trans Troposphere’ (ORTT) initiatives are mandatory to
tap into this domain for multi-fold gains.
What are HAPS
High-altitude platforms (HAPs) are aircraft positioned above at approx. 20 km altitude, in the
stratosphere, in order to compose a telecommunications network or perform remote sensing,
for civilian or military applications. These aircrafts may be airplanes, airships or balloons,
manned or unmanned.3
Figure 1: Layers of the Atmosphere
Source: Encyclopaedia Britannica/ “Earth’s Atmosphere” Weather.gov.sg, 2021
http://www.weather.gov.sg/learn_atmosphere
Manned or unmanned, HAPS serve as one of the most feasible alternatives to expensive
satcom and ISR activities. The need for HAPS is brought to the fore with use-cases such as
last-mile communication, ability to handle heterogenous data, persistence over an area of
interest as well as aiding in coordinated action by multiple agencies. HAP networks combine
the advantages of terrestrial platforms as well as satellites. There are certain altitude zones
that are selected for the use of HAPS.4
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Figure 2: Wind Speed vs Altitude
Source: Malinowski, Andrzej, and Ryszard Zieliński. “High Altitude Platform — Future of
Infrastructure.” International Journal of Electronics and Telecommunications, 2013
https://doi.org/https://journals.pan.pl/publication/100248
These are generally placed between 17-25 kms generally for reasons of atmospheric
stability. As seen in Figure 2, the wind speed at the altitude of operation is the least as
compared to the effects of the troposphere or the more prominent ‘jet stream’ effects at
lower altitudes. Other dynamic processes which lend HAPS to be operated at a specified
zone of attitude are elucidated using schematic at Figure 3. 28 to 31 GHz and 48 GHz are
the bands which have been found to be most promising for communication purposes.5
However, one has to take into account the propagation losses at these frequencies which
may result in attenuation. The range of communication can always be extended using inter-
platform links that also serves the purpose of catering to outage contingencies. In the paper
by Malinowski, an example of coverage of an area off 200 kms has been shown with a
HAPS at five-degree elevation angle at 21km altitude. Such a coverage with a steerable
imagery payload (skewed angle/ oblique image) or ELINT payload can prove beneficial as a
military use-case.
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Figure 3: Dynamic Atmospheric Profiles
Source: Jamison, Lewis, Geoffrey Sommer, and Isaac R III. 2005. “High-Altitude Airships for the Future Force
Army.” Rand.org. RAND Corporation. October 2, 2005 https://www.rand.org/pubs/technical_reports/TR234.html
HAPS Missions and Payloads
Before we get into the details of various technologies involved, it is important to take
cognizance of missions which can be planned keeping HAPS central to the military use-
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case. This in turn will help to decide the payloads which can be aboard these aerial
platforms.
ISR Role. HALE airships can critically fill the voids which exists at the theatre level for ISR
and communication capabilities. Their role as ‘surrogate satellites’ has also been stressed
upon in the thesis work by Collier.6 Shorter transmission distances and better link budgets
are advantageous, thus making them less susceptible to EW measures. The thesis also
covers their role in terms of having a larger footprint and better role as relays as compared to
terrestrial systems. The deployment of these HALE airships above the jet stream in quasi-
geostationary orbits provide advantages in terms of persistence in observation as well as
communication relays. Better antenna design in terms of flexibility and larger aperture size
can offset the disadvantages due to weight and power. The Integrated Sensor Is the
Structure (ISIS) program of DARPA & HiSentinel powered airship of US Airforce Research
Laboratory makes use of these advantages. The roles of HAPS vary from ISR to
Reconnaissance, Surveillance and Target Acquisition (RSTA), maritime surveillance, missile
warnings, EW, communication broadcast relays. In addition, these may be employed to
provide an alternate to Position Navigation and Timing (PNT) Signals (serve as guidance
beacons).
Airships, as with UAS’s, are vulnerable to advanced enemy air defences. Owing to the
airships’ high-altitude, stationary position, and low radar &thermal cross sections, only the
most advanced air defence platforms will be able to detect and target them.
Figure 4: Ground Coverage Area of a HALE at 65,000 feet
Source: https://doi.org/http://hdl.handle.net/10945/3934
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Figure 5: Ground Coverage Area of a HALE at 65,000 feet in Indian Context
Source: Author’s Own Rendition on Google Earth Platform7
HAPS, as part of ISR, can offer broad area mapping by using variety of payloads— EO/IR
sensors, LIDAR, SAR, multi and hyper spectral imagers. Persistent surveillance over an
area— day and night, can also be achieved by loitering over the area of interest.8 Post-
Strike Damage Assessment (PSDA), Direction of Own Arty Fire (DOOAF) as well as battle
damage assessment can also be undertaken by HAPS.
Communications. Wireless solutions using HAPS involve catering to the requirements of
last-mile connectivity i.e. to provide high throughput data networks without relying on the
traditional terrestrial infrastructure. Another advantage offered is in terms of centralised cell-
reuse that are not dependent on the location of the base stations. Geometry of the HAP
stations will help in exploiting the millimetre wave communications as the shorter slant range
offers enhanced communication bandwidths and lesser attenuation factors in the link
budget.9
‘Flexible and reliable’ re-use patterns will also help in the realisation of better formed
networks which can cater to immediate response to a certain area of interest. Cost will also
be substantially lower than that of a satellite constellation as well as numerous ground
stations as part of the terrestrial network. HAPS are environment friendly as they leave
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behind substantially lower carbon footprint and also platform and payload upgradation can
be done rather easily as compared to satellites.10
If HAPS are considered to be working with LEO satellites, there has to be a synergy among
the space, stratospheric and terrestrial entities to utilise maximum benefit from the integrated
approach of a satellite-HAPS based model. Various models can be thought of with variables
such as inter HAP links, inter satellite links11 , on board processing over HAPS or these
platforms to act as mere relays.
Terrestrial layer comprises user terminals— both fixed & mobile. HAPS or the stratospheric
layer can consist of HAPS without on-board processing. HAPS thus, act as mere relays or
hubs which transfer data at much higher data rates and without any ink budget
disadvantages. The processing component is hosted in satellites and these satellites have
the links established, both, to the respective ground stations as well as to HAPS to cater to
redundancy. There could always be a possibility where inter-HAPS links are established to
realise a truly meshed network. Also, the HAPS ground segment or stations caters to
network management and resource allocation in the regional area covered by HAPS. HAPS
and satellite based protocols will have to be designed to cater to bandwidth requirements as
well ensure smooth handoff procedures to avoid jitter in communications.12
Mobility, extended coverage, payload versatility, frequent takeoffs and landings for
maintenance and upgradation of payloads with favourable pathloss characteristics (with
respect to terrestrial and satellite systems) are the main features which make HAPS
attractive for a variety of applications and services. The paper by Capstick & Grace 13
compares the performance and complexity of two methods of steering an array of aperture
antennas on a high-altitude platform for the provision of broadband fixed wireless access
using cellular type frequency reuse. Another paper 14 describes intelligent beamforming
antenna systems that can be used in the millimetre-wave band for HAPS. One is a Multi-
Beam-Horn (MBH) antenna which provides high-speed transmission, and the other is an
array antenna that digitally controls antenna beams. These antenna systems are designed to
withstand the temperature ranges in the stratosphere (below −60◦C) and atmospheric
pressure which is 1/20 that on Earth. Secure communication may also be extended by use
of quantum cryptography techniques where HAPS may be employed to ‘store entangled
photon source’ to distribute the keys to LEO satellites or other ground stations.
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Optical Communication. There has been significant study in terms of optical
communication using HAPS. In a paper15 by Fidler et al, the components to be used as well
as trials using various waveforms has been studied in detail. It describes how the pointing,
acquisition and tracking of laser terminals on board a HAPS can utilise low divergent beams
for multi gigabits per second transmission of data. Atmospheric impact in terms of scattering,
beam spread and fading has also been covered. It lists out the techniques which may be
utilised to mitigate these effects towards a high throughput. Optical communication for HAPS
has been quoted to be studied under various scenarios, LEO satellites to HAPS & ground to
HAPS & HAPS to HAPS. In all cases, works have been cited by Fidler claiming the increase
in the data rate capacity with LEO links and a range of approximately 500 km radius with the
HAPS at 20 km altitude (devoid of cloud interference and turbulence).
IoT and Network Relays. HAPS are competitors with terrestrial and satellite systems, which
makes them good candidates for next generation communication systems. In addition,
HAPS perform the role of a base station16 that can establish communication with satellite
systems using very tall antennas and can handle the increasing demand of broadband
wireless access. IoT17 presents challenges regarding diversity in nodes, large amounts of
processing data, plethora of communication nodes, routing, security, energy consumed and
coverage. Each challenge has important impacts on the performance of IoT systems.
Communication technology is severely impacted by these challenges. Ground
communication tends to have a very limited coverage (say, a few meters). The
communication between nodes using HAPS will provide much larger coverage, especially
extending internet signals, which are the mainstay of IoT communications. Similar analogy
can also be extended for the Battlefield IoT (BIoT). There is also a case in point where
HAPS may be equipped with IoT based sensors to ensure multi-sensor data capture and
hence, fusion of these technologies.
A hybrid nanosatellite-HAPS model can be suggested where the communication range can
easily be extended. Sensors can utilise the power on board HAPS. Low transmission power
and low latency afforded by HAPS should be exploited in implementing communication and
IoT models. Different satellite/HAP architectures allow multitude of applications, which
makes IoT systems more versatile and scalable. Therefore, the proposed architectures are
Satellite/HAP/HAP/IoT, Satellite/HAP/IoT and HAP/HAP/IoT. Backhaul limitations of the
network architecture can also be mitigated to a large extent by the use of HAPS.18
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Wireless Sensor Networks (WSNs). Similar to the architectures mentioned above for IoT,
study has also been done for WSN models. Mitchell et al. further developed this idea and
proposed two HAP/WSN architectures19 appropriate for vital applications such as monitoring
and security. One architecture bases itself on direct transmission to HAPS, hence reducing
the energy consumed and is less complex. This is suitable for low data rates and large
coverage. The other architecture comprises nodes setup in clusters with no direct
communication between sensor nodes and HAPS. Data transmission and reception is based
through the cluster head and is suited for high data rate application with very low latency
requirements.
A model to connect two heterogenous networks such as satellites and HAPS has also been
studied20 by Raveneau et al. This architecture is called ‘store-carry-and-forward’, which is
based on the Delay Tolerant Networking21 (DTN) technique.
Private Internet Connectivity. While the present-day technology is looking for ways to
extend internet to the last mile, HAPS can come in a big way to support this cause. HAPS
are poised best for the setting up of core networks. They can be used to provide point to
point (bearer) links. In all these respects, the use of HAPS is analogous to that of satellite
and VSATs (Very Small Antenna Terminals). Providing higher bandwidths is where HAPS
can be most gainfully exploited. The armed forces may use the same analogy for setting up
of virtual private networks or VPNs.
Electronic Warfare (EW). Electronic Support(ES) Electronic Attack(EA) roles are most
suited to HAPS as part of EW. MTI, ELINT & COMINT payloads, on board HAPS, can be
invaluable assets. SAR’ payload exhibits coverage for miles into an area of interest— land
based or over the seas, and can definitely augment the capabilities of the surveillance grid.
Alternate PNT Signals. May be used to provide an alternate to work in GPS denied
environments.22 Forces, all over the world, are looking at methods to develop resilient PNT
signals— a fact that has gained momentum after the GNSS jamming has been leveraged at
the core of ‘soft kill’ methods against drones/ UAVs. HAPS may be utilised to provide
navigation signals or set up ‘localised positioning system’ where the UAVS/ drones can use
these ‘beacons’ to navigate safely and complete the assigned mission.
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HAPS Technologies: Challenges Involved
It is pertinent to highlight the challenges involved through the kaleidoscope of relevant
technologies which attributes to making HAPS a relatively low-cost force multiplier.
Control Over Aerial Drift. While fixed wing HAPS still lend themselves to be manoeuvred, it
is the high-altitude balloon (‘blimps’, if we can call them) which will require extensive station
keeping to focus on persistent targeting in view. ‘Station keeping’, thus assumes high
importance— a term largely used with satellites to maintain the orbital parameters,it can also
be extended to HAPS (pseudo satellites).
Although near-space altitude of 65,000-300,000 ft have a stagnant weather, however (i.e.
storm, rain), wind still exists, which is important for HAPS. A paper23 addressing this aspect
brings out the difficulties in maintaining the sway & drift movement of this stratospheric
bodies. HAPS are complex man-made machines and the dynamics of an airship is highly
non-linear, coupled and complex. PID24 based and fuzzy logic based approaches are also
discussed in the paper ultimately leading to future scope of work involving practical tests. An
important set of trials are being undertaken in Germany 25 for managing HAPS using
advanced traffic control to monitor the climb and descent rates, weather based behaviour,
route planning etc. This is one of the foremost programmes which highlights the integration
of HAPS as part of aerospace management.
Envelope Material for Blimps. Lightweight and high strength envelope material is one of
the bottlenecks for the development of stratospheric airships, which directly determines the
long endurance flight performance and loading deformation characteristics of the airship.26
More developments have to be made with respect to the uniaxial & biaxial stress the
material has to undergo while in air. The problem is relatively simplified for fixed wing HAPS;
however, thermodynamics and aerodynamics are the most relevant forces to counter and
adjust the fixed wing solutions.
Payload Size. While aerial coverage, high throughput and persistence over an area of
interest, are major advantages, the payload size is of major concern. A trade-off has to be
reached based on the proposed employment between the weight of the payload and the
endurance envisaged. As part of ISR activities, NATO had initiated a programme called the
‘BalSAR’27 or the ‘Balloon-borne SAR’ for maritime surveillance. The unique advantages
(higher immunity against attack and wider coverage of the ground) offered by HAPS over the
aircrafts and UAVs motivated this programme. Zephyr (Airbus), ISIS (Lockheed Martin) &
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Radar Aerostat (Raytheon) are few HAPS programmes which are costly and have already
been employed for ISR tasks. The BalSAR aims at a balloon that is capable of lifting a heavy
payload of nearly 20 kg weight at an altitude of 30 km with its own telemetry system and
recovery based on parachute system. SAR is implemented as a X-band radar architecture.
The transmitted waveform is generated by a frequency synthesiser (phase locked loop
based). This approach focuses on a compact, low cost and low power consumption solution
that allows for the generation of large bandwidth and high chirp rate waveforms. With the
accelerated advances in MEMS and VLSI, how much the weight of the payload can be
shrunk is only limited by present day technology threshold as also that of the human brain
prowess.
Captive Power Source. A combination of batteries (to power the attitude control, drift
control and health maintenance of the HAPS) and high-grade solar cells (space-grade) are
the ideal technology candidate for HAPS. This will ensure that HAPS stay afloat for months
together. The several metres long wingspan of ‘fixed wing HAPS’ may be utilised to host the
solar panels (Figure 6), while for balloons, the envelope material is a likely deployment area
for solar cells. ‘Zephyr T’, one of the HAPS line-ups from Airbus28 has a weight of 140 kilos
and a wingspan estimated to be much larger than the previous variant ‘Zephyr S’ (25
metres).
Figure 6: Fixed Wing HAPS
Source: https://www.sae.org/news/2018/12/high-altitude-pseudo-satellites-new-battle-for-inner-space-part-i-copy
Majority of technologies involved are common to, both vis satellites and HAPS. However, a
comparison with satellites will help gauge the effectiveness of using HAPS. Satellites suffer
from some major disadvantages like no payload change possible once launched and
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steering the satellite to a brand new orbit (orbital manoeuvrability due to limited fuel on
board).
Questions to be Pondered: HAPS Development Matrix
India is trying to catch up with respect to HAPS development. While there has been news of
indigenous development 29 , any progress is yet to be confirmed.Before delving into the
questions as part of the development matrix, it will be prudent to consider deployment
scenarios as hypothesis which can aid in the process of framing questions.
Scenario 1: Remote Sensing
The aspect of remote sensing may be viewed with two options vis. Standalone HAPS
(SA-HAPS) and Satellite Augmented HAPS (Sat-HAPS). While SA-HAPS will be purely a
HAPS based network, Sat-HAPS can augment the reach of satellite deliverables to the
ground. Various developments have been made in terms of ISR payloads ranging from SAR
to 3D Mapping and affording optical communication payloads. Throughput of 30 Mbits per
second30 has also been demonstrated as part of broadband communication to transmit high
resolution data to ground control. A tally of three scenarios for the use-case of HAPS
involving SAR, MTI and long-range surveillance has been illustrated in Figure 7.31 A
proposed coverage for ISR on the Northern, Western and Eastern borders is reproduced
below with likely HAPS coverage (Figure 8). The system represented can be employed as
SA or as a Sat-HAPS model.
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Figure 7: HAPS’ Potential
Source: https://elib.dlr.de/113651/1/haps4esa_2017_Baumgartner.pdf
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Figure 8: HAPS Coverage on India’s Borders (Suggested Representation - Not to Scale)
Source: Author’s Own Interpretation of the Deployment Scenario
Scenario 2: Control of Assets: Land, Air & Sea Based
Autonomous systems are now becoming synonymous with weapon platforms. HAPS can be
used to cover the area of responsibility entrusted to other platforms as well. An overlap can
ensure high probability of mission accomplishment. The scenario is represented by the
graphic at Figure 9. Loitering munitions as well as controlling a swarm of drones is also
practically possible with such an employment of HAPS.
Figure 9: Control of Assets in a Theatre (Representation Only)
Source: Author’s Own Interpretation & is Merely Suggestive
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Scenario 3: Communication Network Establishment
With growing impetus on private LTE and 5G networks being tried, tested and evaluated by
the forces, HAPS can be leveraged in providing the war fighter with a truly meshed
communication network with inbuilt redundancies.
A range of frequencies has been shortlisted by the WRC for the use of and to accommodate
the growing interest around HAPS. HAPS can use the following frequency bands: (a) 1885 –
1980 MHz, 2010 – 2025 MHz and 2110 – 2170 MHz for base stations in the mobile service
according to RR5.388A and Resolution 221(Rec.WRC-07); (b) 6440 – 6520 MHz and
6560 - 6640 MHz for HAPS gateway links in countries listed in RR5.457 and pursuant to
Resolution 150 (WRC-12); (c) 27.9 – 28.2 GHz and 31 – 31.3 GHz for HAPS in the fixed
service in countries listed in RR5.537A and 5.543A and pursuant to Resolution 145
(Rev.WRC-12); (d) 47.2 – 47.5 GHz and 47.9 – 48.2 GHz for HAPS in the fixed service
pursuant to Resolution 122 (Rev.WRC-07). Also, as per WRC-19, fixed service in the
frequency bands 31-31.3 GHz and 38-39.5 GHz will be identified for worldwide use by
HAPS. They also confirmed the existing worldwide identification for HAPS in the bands
47.2 – 47.5 GHz and 47.9 – 48.2 GHz that are available for worldwide use by
administrations wishing to implement high-altitude platform stations. They agreed to the use
of frequency bands 21.4-22 GHz and 24.25-27.5 GHz by HAPS in the fixed service.32
The communication field is leading the way in development of HAPS for commercial use,
driven by Google and Facebook.33 Their aim is to extend Internet access to those who do
not have it, and HAPS is one of the means to do this. Google’s project is called ‘Project
Skybender’ which uses Solara 50― a solar powered HAPS with a wingspan of 50 m and
manufactured by Titan Aerospace. Facebook’s HAPS ‘Aquila’, made of carbon fibre, has a
wingspan of 42 m and runs on solar power. Its targeted non-stop flight time is three months.
With laser communications from the ground to the HAPS, the HAPS radiates radio waves in
a diameter of approximately 50 kms directly below itself, and the transmission is expected to
be at a single-digit Gbps. ‘Robustness versus Capacity’ are one of the main trade-offs when
it comes to designing a military-grade network. Moreover, these performance indicators are
to be valued against the metrics of constrained resources, limited budget and an ever-
shrinking spectrum. One also has to see the greater reliance of forces as they transition from
being network enabled to network centric in their approaches. The increased attack surface
thereby provided to the adversary imposes further emphasise on the requirement of a robust
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network. John and Vincent in their work34 have suggested a high connectivity network which
ensures that all nodes are connected at all times, hence, providing near-real time information
towards establishing a Global Information Grid (GIG).
Figure 10: Design region for high-connectivity service
Source: IEEE, Milcom Conference, 2010
With the increase in the data rate, the effectiveness to coordinate operations also increases.
A steep gradient is seen in the ‘S’ shaped curve implying a jump in the effectiveness within
the high connectivity region. This region is found to be most suitable for ensuring higher
mission effectiveness as compared to a high capacity service which, although has higher
benefits, but entails a considerable cost penalty when seen in terms of hardware/
infrastructure (marginal cost principle). A ‘dependable capability’ will be more preferred over
‘data quantum’.
Scenario 4: Electronic Warfare
With reference to the use of HAPS in Electronic battles, immense use- case scenarios can
be imagined in ELINT, COMINT as well as limited EA systems. A constellation of HAPS can
work well for direction finding tasks by making a reasonable baseline for interferometry
operations. Persistence over an area can also help in ensuring denied spectrum especially
PNT signals for the adversary. However, high power jammers seem unfeasible onboard
HAPS due to heavy power requirements for the required radiated power.
Scenario 5: Situational Awareness
Battlefield situational awareness afforded by IoT can be greatly enhanced by use of HAPS.35
As shown in Figure 9 earlier, the coverage of HAPS, by establishing fail-safe links can
increase the real time awareness of the war fighter by communication, video and data feed.
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Not all encompassing, however, the five scenarios as mentioned above, pose certain
questions.
• Are we treating Space as a domain with HAPS as an inherent part of it?
• Is the use of HAPS leading to a clear meeting of futuristic requirement of the war
fighter?
• What policy and strategy do we need to adopt? Are DPSUs and private players ready
to contribute? How can Space agencies carry this project forward?
• What are the implications of HAPS as a cost-benefit analysis?
• What shorter term actions should we take to test the efficacy of this platform?
HAPS Implementation Strategy
HAPS’ use is in perfect sync with what should be the ‘Space Modernisation Strategy’. Three
main pillars of this strategy revolves around persistent ISR, high bandwidth and throughput
enabled communication & net-centric operations. HAPS have all the features of coverage,
access and flexibility making it a potent ISR tool. Being in a quasi-stationary orbit allows
better gathering of data while at the same time obviates the requirement of a forward area
footprint. It can almost be launched along with the operation or combat pulse. The
implementation strategy for utilising HAPS will entail points as elaborated further.
• Advanced concept and technological demonstration of HAPS using
prototypes is mandatory. Players such as HAL in India as well as private
players as part of Indian Space Association (ISpA) can pitch in to nurture this
field. Civil, military and academia fusion is mandatory.
• Multi-sensor data fusion (MSDF) is key. Use sensors planned to be used
with HALE UAVs with the advantage that, these are already optimised for
operating at the intended altitude. AWACs, UAVs, Ground telemetry stations,
maritime vessels can all be linked to receive data from HAPS. Battlefield IoT
can also benefit greatly with the use of this trans-troposphere platform.
Locations where HAPS may be utilised, once finalised, ‘should result in them
being used as a theatre asset to begin with’. This later need to proliferate to a
lower operational level asset that is completely under the control of the
commander on ground.
• Mesh HAPS as Part of Algorithmic Warfare. With immense use of HAPS
as a communication platform resulting in meshed networks which are in-built
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with redundancy, a dedicated team (Project MAVEN36) should be established
to look at developing AI based models which can, not only help to control the
platform, but also yield in better software to develop systems to assist the
soldier.
• Inaccessible and difficult terrain can act as test bed for communication
capability testing for HAPS. Unlike the conventional macro Base Stations
(BSs), the envisioned HAPS mounted Super Macro Base Stations (SMBS)
[HAPS-SMBS] not only enhances coverage and capacity, but also supports
data acquisition, computing, caching, and processing in a plethora of
application domains. Compared to UAVs, HAPS systems, which are
inherently quasi-stationary, have a larger footprint, more computational
power, and better LOS communication links. HAPS-SMBS can therefore be
regarded as powerful platforms to enhance connectivity. HAPS-SMBS
systems, however, are not alternatives to terrestrial BSs; instead, they are a
complementary solution for network management and control. The wide
footprint of HAPS systems is ideal for providing greater coverage to high
number of IoT devices each with low-rate links. In addition, IoT devices might
be located in areas where there are no terrestrial network coverage.37
Future of HAPS
According to recommendations provided by Kurt Et Al, HAPS should have a wide footprint of
about 500 km in radius.38 A network of multiple HAPS can extend the coverage to serve the
whole country. For example, a HAPS constellation of 18 nodes is estimated to be sufficient
to cover all of Greece, including all of its islands. HAPS have become an inseparable part of
the new generation of wireless networks. Technology enablers such as free space optics,
LASERS, VLSI, structural and material sciences, avionics and antenna design have resulted
in never seen before changes in communication technology. The cited work 39 has
incorporated the role of reconfigurable intelligent surfaces (RIS) as we graduate towards 6G
as well as Faster Than Nyquist (FTN) signalling.
As has been brought out in this brief, HAPS can provide aerial control over drones and other
UAVs through edge computing and taking the computation load off from these platforms.
Swarms can also be seen within the ambit of its applications. HAPS are also being viewed
as portable data centres for highly dense computer networks.
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One major concern which will need to be addressed is the acceptance of HAPS as part
airspace policy over a country. ICAO regulations 40 will need to be suitably tweaked to
include these platforms. HAPS Alliance (industry based consortium) also works in areas of
aviation and commercialisation to build a strong HAPS ecosystem. In addition, areas of
concern includes the continuous RF/ Optical beam pointing and steering on HAPS platforms
due to its ‘near circle like orbit’ which will cause continuous steering mechanisms to be in
place. Also, the self-healing and self-organising networks as part of the HAPS architecture
need greater research.
Conclusion
Like any new concept (although the concept of HAPS definitely is dated), there is bound to
be skepticism surrounding the topic as more than the strategic value or utility, the concept of
marginal cost and similar economic factors come into the picture. Cost effectiveness is
certainly paramount, however, if HALE airships/ HAPS/ Pseudo satellites can serve as an
alternate means to fill in the gaps in multiple capabilities, it is definitely worth
experimentation.
Sheer vastness of our frontiers, varied terrain and with neighbouring countries displaying
aggressive tendencies, the ‘theatres’ as perceived will fall short of sensors to aid in
maintaining ascendancy as well as prevent strategic and tactical surprises. Proponents of
technology and evangelists alike may brush aside the concept of HAPS’ utilisation. However,
prudence dictates that worthiness of HAPS be further studied based on operational and
strategic requirements.
Stratosphere berthed HAPS can support the tactical / operational commander with real time
information resulting in a responsive OODA loop. This will also accrue benefits of not being
burdened with issues of station keeping etc. while also reducing the logistical and
administrative functions.
With regards to HAPS, there are several issues that need to be addressed. HAPS should not
be seen as the finale in terms of platforms or technologies which will lead to the most robust
of systems or a high-point in technology asymmetries, but should be seen as a stepping
stone towards enhancing the ‘already existing satellite systems’ and complement the
constellations of nanosatellites/ CubeSats that are planned to be placed in orbit for various
roles. Responsiveness of space-based assets will definitely be improved by HAPS as also
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the requirements that emerge out of a surge in activities due to adversarial actions. HAPS
should definitely not be seen as a ‘Maginot line’ in space.
End Notes
1“Zeppelin: Definition, History, Hindenburg, & Facts”, Encyclopædia Britannica, 2021. Available at
https://www.britannica.com/technology/zeppelin. Accessed on 25 December 2021.
2 Ibid.
3 D’Oliveira, Flavio Araripe, Francisco Cristovão Lourenço de Melo, and Tessaleno Campos Devezas, “High-
Altitude Platforms - Present Situation and Technology Trends”, Journal of Aerospace Technology and
Management , 2016. Available at bhttps://doi.org/10.5028/jatm.v8i3.699. Accessed on 25 December 2021.
4 Malinowski, Andrzej, and Ryszard Zieliński. “High Altitude Platform — Future of Infrastructure”, International
Journal of Electronics and Telecommunications, 2013. Available at
https://doi.org/https://journals.pan.pl/publication/100248. Accessed on 25 December 2021.
5 Ibid.
6 Kacala, Jeffrey C, and Corey M Collier. “A Cost-Effectiveness Analysis of Tactical Satellites, High-Altitude Long-
Endurance Airships, and High and Medium Altitude Unmanned Aerial Systems for ISR and Communication
Missions”, Nps.edu, 2017. Available at https://doi.org/http://hdl.handle.net/10945/3934. Accessed on 25
December 2021.
7 Roughly a 320 mile (520-kilometre radius) for a HALE HAPS if kept quasi stationary near Leh.
8 “Unmanned Aerial Systems for Intelligence, Surveillance, Reconnaissance – DSIAC.” Dsiac.org, 2018.
Available at https://dsiac.org/state-of-the-art-reports/unmanned-aerial-systems-for-intelligence-surveillance-
reconnaissance/. Accessed on 28 December 2021.
9 P Pace, G Aloi, F De Rango, E Natalizio, A Molinaro and S Marano, "An integrated satellite-HAP-terrestrial
system architecture: resources allocation and traffic management issues”, 2004 IEEE 59th Vehicular Technology
Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514), 2004, Vol.5, pp. 2872-2875.
10 Ibid.
11 T Tolker Nielsen, JC Guillen, “SILEX: The first European Optical Communication Terminal in Orbit” ESA
bulletin, November 2001.
12 Ibid.
13 MH Capstick, D Grace, High Altitude Platform mm-Wave Aperture Antenna Steering Solutions, 2005, pp. 215–
236.
14 Hiroyuki Tsuji, Masayuki Oodo, Ryu Miura, Mikio Suzuki (2005), “The Development of Intelligent Beamforming
Antenna Systems for Stratospheric Platforms in the Millimeter-Wave Band”, pp. 237–255.
15 Fidler, Franz, Markus Knapek, Joachim Horwath, and Walter R Leeb, “Optical Communications for High-
Altitude Platforms”, IEEE Journal of Selected Topics in Quantum Electronics, 16, no. 5, September 2010.
Available at https://doi.org/10.1109/jstqe.2010.2047382. Accessed on 01 January 2022.
16 Said, Omar, and Amr Tolba. “Performance Evaluation of a Dual Coverage System for Internet of Things
Environments.” Mobile Information Systems 2016, pp. 1–20. Available at https://doi.org/10.1155/2016/3464392.
Accessed on 01 January 2022.
17 IoT or internet of things is a disruptive technology that establishes communication between physical objects in
space, in seas, and on earth. These nodes rely on internet for data transmission. Latency, packet drops,
throughput, energy used, and hand-off are some metrics used to study IoT systems. HAPS can assist in
mitigating the problems associated with each.
18Alsharoa, Ahmad, and Mohamed-Slim Alouini. “Facilitating Satellite-Airborne-Terrestrial Integration for Dynamic
and Infrastructure-Less Networks”, Kaust.edu.sa, 2019. Available at
https://doi.org/http://hdl.handle.net/10754/660722. Accessed on 01 January 2022.
19 Mitchell, Paul Daniel, Jian Qiu, Hengguang Li, and David Grace. “Use of Aerial Platforms for Energy Efficient
Medium Access Control in Wireless Sensor Networks”, Computer Communications, no. 4, March 2010, pp.
500–512. Available at https://doi.org/10.1016/j.comcom.2009.10.015. Accessed on 01 January 2022.
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20 P Raveneau, E Chaput, R Dhaou, E Dubois, P Gélard, and AL Beylot, “Carreau: Carrier Resource access for
mUle, DTN applied to hybrid WSN/satellite system”, Proceedings of the 2013 IEEE 78th Vehicular Technology
Conference (VTC' 13), September 2013.
21 Delay-tolerant networking (DTN) is an approach to computer network architecture that addresses the technical
issues in heterogeneous networks which suffer from low connectivity. Network established in space and mobile
communication in difficult terrain are its examples.
22 N.8.
23 W Zhou, P Wang et al., “Station-keeping Control of an Underactuated Stratospheric Airship” Int. J Fuzzy
System, 2019, pp.715–732. Available at https://doi.org/10.1007/s40815-018-0566-4. Accessed on 04 January
2022.
24 Proportional Integral Derivative (PID) controllers use a control loop feedback mechanism to control process
variables and are the most accurate and stable controller.
25 The OBeLiSk project, “DFS Deutsche Flugsicherung GmbH”, Www.dfs.de, 2020. Available at
https://www.dfs.de/dfs_homepage/en/Press/Press%20releases/2021/11.02.2021.-
%20The%20OBeLiSk%20project%3A%20Optimising%20the%20use%20of%20high-altitude%20pseudo-
satellites%20(HAPS)/. Accessed on 04 January 2022.
26 J Meng Lv et al., “ Mechanical Properties and Strength Criteria of Fabric Membrane for the Stratospheric
Airship Envelope”, Appl Compos Mater , 2017, pp. 77–95. Available at https://doi.org/10.1007/s10443-016-9515-
2. Accessed on 04 January 2022.
27 M Martorella and E Aboutanios, “BalSAR: A stratospheric balloon-borne SAR system and its use for maritime
surveillance”, Available:https://www.cmre.nato.int/msaw-2019-home/msaw2019-papers/1371-msaw2019-
martorella-balsarastrastophericballonbornesarsystemanditsuseformaritimesurveillance/file. Accessed on 07
January 2022.
28 Richard Gardner, “High-Altitude Pseudo Satellites: New Battle for Inner Space, Part I”, Sae.org, 2018.
Available at https://www.sae.org/news/2018/12/high-altitude-pseudo-satellites-new-battle-for-inner-space-part-i-
copy. Accessed on 07 January 2022.
29 Aksheev Thakur, “HAL to Partner with Bengaluru Start-up to Develop HAPS”, The Hans India, 08 July 2021.
Available at https://www.thehansindia.com/news/cities/bengaluru/hal-to-partner-with-bengaluru-start-up-to-
develop-haps-694842. Accessed on 07 January 2022.
30 N.28.
31 Stefan Baumgartner et al., “HAPS: Potentials, Applications and Requirements for Radar Remote Sensing How
to Manage That Advantages for Remote Sensing. Available at
https://elib.dlr.de/113651/1/haps4esa_2017_Baumgartner.pdf. Accessed on 08 January 2022.
32 “WRC-19 Identifies Additional Frequency Bands for High Altitude Platform Station Systems”, Itu.int, 2019.
Available at https://www.itu.int/en/myitu/News/2020/02/03/15/54/WRC19-identifies-additional-frequency-bands-
for-High-Altitude-Platform-Station-systems. Accessed on 07 January 2022.
33 Hideki Kinjo, “Evolution of Micro satellites and High Altitude Pseudo-Satellites (HAPS): Potential for New
Satellite-Based Services”, Global Strategic Studies Institute, 2016. Available at
https://www.mitsui.com/mgssi/en/report/detail/1221520_10744.html.Accessed on 07 January 2022.
34 MC John and WSC Vincent, "Ultra high connectivity military networks”, Military Communications Conference
(MILCOM), 2010, pp. 1011-1018.
35 “Connectivity from the Stratosphere”, Itu.int, 2019. Available at
https://www.itu.int/en/myitu/News/2020/04/24/09/24/Connectivity-from-the-stratosphere. Accessed on 07 January
2022.
36 Deputy Secretary of Defense, “Memorandum – Establishment of AWCFT Project Maven”,
http://www.govexec.com/media/gbc/docs/pdfs_edit/establishment_of_the_ awcft_project_maven.pdf, April 2017.
Accessed on 07 January 2022.
37G Kurt et al., “A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future”,
arXiv.org, 2020. Available at https://arxiv.org/abs/2007.15088.
Accessed on 07 January 2022.
38“Preferred characteristics of systems in the fixed service using high altitude platforms operating in the bands
47.2-47.5 GHz and 47.9-48.2 GHz”, ITU Recommendation, January 2000.
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39 G. Kurt et al., “A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the
Future,” arXiv.org, 2020. Available https://arxiv.org/abs/2007.15088. Accessed on 07 January 2022.
40International Civil Aviation Organization (ICAO) defines two distinct HAPS classes: unmanned free balloons
and the unmanned aircraft. Accordingly, an unmanned free balloon is defined as a non-power driven, unmanned,
lighter-than-air aircraft in free flight, whereas an unmanned aircraft is defined as an aircraft intended to operate
with no pilot on board.
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The views expressed and suggestions made in the article are solely of the author in his personal capacity and do not have any
official endorsement. Attributability of the contents lies purely with author.
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