Submarine communications is an area where the US Navy retains
an undisputed supremacy in support of her strategic submarine
fleets. Now new information made public, makes this area one
of the prominent spheres of Indo–United States
technical
and military cooperation.
Through the decades the Indian Navy was perhaps the pioneer
among the Services in strategic thinking and anticipated its
value as a potential key component of
India’s
emerging, albeit closely guarded nuclear-doctrine. It was
apparent from the outset that nuclear-powered ballistic
missile armed submarines (SSBN) would constitute the most
reliable element among assured retaliatory nuclear-strike
platforms, for their inherent “stealth” attributes, for being
mobile, submerged and out of reach of most electromagnetic
frequency bands for detection. A similar view was forcefully
held by the legendary Russian Admiral of the Fleet Sergey
Georgyevich Gorshkov, and knowing his personal influence on
the Indian Navy’s strategic thinking and formulation, this was
hardly surprising.
Presently, decades later not only an Indian Navy SSBN in the
shape of Advanced Technology Vessel (ATV) is gradually taking
shape, as an interim measure, if few more or less reliable yet
radical media reports are to be believed, the strategic and
perhaps the nuclear-punch is being incorporated in
conventional-powered hunter-killer submarines (SSK) in the
shape of specific BrahMos supersonic cruise missiles. The
potential is also inherent in possible Indo-Israeli
developments in missile technology, especially in areas of
Inertial Navigation Systems (INS) and terminal guidance. Yet
to be really effective in the strategic sense, the submarines
in the area of situational awareness, remain inherently weak
because of their “isolationist nature” and need to be
contacted and commanded by National Command Authority (NCA),
to issue launch orders, the absence of which cripples the
formidable strategic platform and renders it impotent.
No wonder the Indian Navy attached high priority to submarine
communications even decades ago and subsequently anticipated
the importance of Very Low Frequency (VLF) underwater
transmissions instantaneously. As part of an ambitious naval
modernisation program, during the mid-1980s the Indian Navy
had constructed a VLF broadcasting station in Tamil Nadu.
Although not publicly declared, it was reported that the
United
States, the undisputed leader of submarine communications
actively collaborated in the project, which was completed in
September 1986. This facility needs to be viewed as an
“initial step” in the quest of development of underwater Very
Low Frequency/Extremely Low Frequency (VLF/ELF) and laser
communications for effective coordination of the submarines
with the Indian NCA.
The operational VLF facility is used by the Indian Navy to
communicate with its SSK fleet of Russian Kilo Class and
German Type 1500, with trailing communication buoys at
periscope depth of 10 to 20-metres. After the nuclear-powered
ATV become operational, the VLF facility will permit Indian
National Command Authority to issue launch orders to the
submerged ATVs at periscope depth. VLF waves propagate to
almost a quarter of the globe away and are generally immune to
atmospheric disturbances caused by nuclear detonations.
Extremely Low Frequency (ELF) waves on the other hand can
penetrate to depths of 100-metres but a huge overland
infrastructure needs to be built up with at least 80-km long
antennae. In this context, as far back as 1986, researchers
from the Defense Electronics Applications Laboratory, Dehra
Dun, after reviewing the effects of nuclear radiation and
EMP on
VLF/ELF communication systems,, concluded that "ELF radio
communication was the only reliable means which could
withstand the effects of a nuclear holocaust and was least
disturbed by the EMP generated by nuclear explosion".
Subsequently classified research and development in these
areas was carried out by National Institute of Oceanography,
Goa, Indian Institutes of Technology (IITs) Madras and
Bangalore, and Defense Electronics Applications Laboratory,
Dehra Dun –– although the system in principle relies on fixed
terrestrial infrastructure and thus was vulnerable to enemy
strikes.
However on the negative side, the small bandwidth of VLF
transmission limits the rate of transmission of data, usually
allowing only the operation of slow Teletype messages.
Moreover the large terrestrial and static VLF/ELF facility
would be vulnerable to enemy strikes as even if the facilities
are shifted deep underground in “hardened” shelters, the vital
and critical communication antennae would have to be located
above ground and would remain vulnerable.
Thus Indian Navy is left with no other option but to develop,
ideally with
United States
assistance, an airborne VLF transmitter similar to the United
States Navy (USN) “Take Charge & Move Out” (TACAMO) to ensure
survivability of its VLF facility and thus retaining the
critical sub-surface nuclear-punch. For TACAMO missions the
USN initially utilised the EC-130A/Q Hercules platforms with a
powerful 200-KW transmitter providing the VLF transmissions
through a 10-km long trailing wire antennae with a drogue
parachute at the end. During transmission the aircraft
maintained a flight-profile in a continuous tight circle,
which resulted in over 70-percent of the wire hanging straight
down and acting as a relatively efficient vertical antenna.
The undisputed lead of
United States
in the area of VLF TACAMO technology is forcefully represented
by the present Electro Magnetic Pulse (EMP) hardened E-6
Mercury airborne platform of the United States TACAMO
Communications System providing survivable communication links
between the United States NCA and Strategic Forces. A
derivative of the classic commercial Boeing 707, in-flight
refueling facility ensures E-6 mission ranges of over
6000-nautical miles and endurance of up to 72-hours, thanks to
four economical CFM-56-2A-2 high bypass ratio fan/jet engines
with thrust reversers.
A further enhancement in the form of E-6B fulfils both TACAMO
and Airborne National Command Post (ABNCP) missions by
incorporating a subset of United States Strategic Command (USSTRATCOMM)
EC-135 ABNCP equipment into the E-6 platform along with battle
staff positions as determined by USSTRATCOMM (J36). The result
is a formidable dual-mission aircraft capable of fulfilling
either the E-6A mission or the airborne strategic command post
mission (“Looking Glass”?) and is equipped with an Airborne
Launch Control System (ALCS) capable of launching United
States ICBMs. With at least a pair of E-6 always airborne the
mobility and flexibility of E-6B provides a survivable
Command, Control and Communications (C3) force management for
the United States NCA via multiple frequency-band
communications, an aspect the Indian Navy should emulate at
least in principle and policy to ensure survival of its
hitherto limited strategic arsenal.
Meanwhile in a series of technological breakthroughs
attention has shifted to laser based underwater
communications. There is an optical window in the blue-green
part of the laser spectrum, which enables transmission to
penetrate the ocean to substantial distances to depths of
500–700-meters. Power requirements are considerable and the
system at least presently cannot be installed in artificial
satellites. Thus as a tactical improvisation the laser is made
ground based, preferably mobile, in perfect conjunction with a
space based mirror with adaptive optics being used to produce
a cohesive beam. Significantly, data transfer rate will be
with “unrestricted speed” somewhat 300 times greater than ELF
system. Laser communications will assume priority significance
if they become capable of down-linking satellite imagery of
enemy ballistic missile deployment and launch, in friendly
submerged submarines to ensure assured retaliatory strike.
In
India by the early 1980's work proceeded on laser
communication links from the air and ground in a joint project
at the Ocean Engineering Centre and the Laser Communication
Laboratory, IIT Madras so that by 1985 an experimental
facility for measuring the attenuating effects of the ocean
surface on laser beam penetration was already in operation. It
was concluded "that (hindrance by) ocean waves were not a
serious drawback in a laser communication link, as long as the
laser had sufficient power to penetrate the atmosphere twice
and penetrate ocean water for a distance up to several
hundreds meters". Measured values of attenuation coefficients,
for ocean waters collected from the
Arabian Sea and the
Bay of Bengal, were presented in due course with the region of
minimum attenuation for pure particle-free sea water, were
found to be 450–500-nm.
No wonder,
United States
assistance in this sphere will prove to be decisive as the
effective combination of nuclear submarines and underwater VLF/ELF
and laser communications will make our sea based nuclear
deterrent optimally effective and serve as an assured
deterrence in any “emerging Nuclear Scenario”.
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