Shooting the bird: word gets around that is, if the communication channels are available, open and online. Satellite communication links are vital to today's warfighter, and even more so on the tactical level. Pointing an antenna at a satellite and shooting voice, data and video back and forth has become an integral ingredient of the communications prescription for success.
This requires a copious supply of bandwidth, which can realistically only be provided, or in reality, enhanced, by a tactical satellite communication capability.
Many of the legacy satellite communication systems are in the SHF X (around 7.9 to 8.4 GHz) and Ku - band (German: Kurz - unten, or just - under) at 10.9 to 14.5 GHz) frequencies, but systems are increasingly being provided in the higher - capacity EHF Ka-band (Kurz - above - 27.5 to 31 GHz).
On the practical side, the lower frequencies provide better connectivity through rain and foliage (and mitigate 'snow fade', which can alter the focal point of the dish), while higher frequencies have narrower beamwidths requiring precise pointing and tracking algorithms, but are more jam resistant and offer increased throughput.
Nevertheless, the real drivers in frequency usage are availability and capacity, as bandwidth demand constantly outstrips the supply of military satellite capacity at both X - and Ka - bands. Commercial Ka - band satellite providers have traditionally filled this gap (for a premium price of course), and therefore, as mentioned above, military terminals are increasingly being developed with a Ka - band option.
No Longer Gapfiller
The Wideband Global Satcom (WGS) system, a programme driven by the US Department of Defense and its Australian counterpart, augments the Ka - band overload with more than ten - times the bandwidth (2.1 to 3.6 Gbps per bird) of current Defense Satellite Communication System (DSCS III) satellites, which are now past their ten - year design life (although a few are still operational).
The WGS, initially designated Wideband Gapfiller Satellite system, provides round--the - clock broadband service to tactical warfighters and some fixed - user sites. Boeing Satellite Systems is contract prime, thus far responsible for building the seven satellites (contract to begin production of the seventh bird was awarded on 23 August 2010), each of which were projected to carry a $ 300 million price tag. This latest award to Boeing included options for production of up to six satellites (for a projected total of thirteen).
The WGS satellites use reconfigurable antennas and digital channelisers and can tailor coverage over an area that requires enhanced X - and Ka - band connectivity. The WGS design provides 19 independent coverage areas through eight steer - able and shape - able X - band beams and ten Ka - band independently steerable diplex antennas.
Tactical satcom terminals cover a wide range of mobility and portability options. Some of the most recent developments have centred on the provision of the mobile connectivity capability of satcom - on - the - move (SOTM), which can provide greater capability in terms of weight and power than portable and man - packable terminals, while still offering tactical flexibility. However, the latter remain the only solution for dismounted or heli - borne troops.
SOTM entails affixing a satellite radome to the roof of a vehicle in order that the actual antenna (inside the radome) can track the bird whilst the vehicle is in motion. This exercise is even more complicated than it sounds.
One of the first considerations is whether or not to dedicate a vehicle to a command and control role, therefore requiring the SOTM option.
Another issue to consider is the space constraints on the vehicle roof. Front - line vehicles that need an SOTM capability usually have slat (or bar) armour, an overhead weapon mount, often an active protection system, lighting and other antennas vying for space. Installing a satcom antenna that must have a clear view to chase a satellite is virtually impossible.
As mentioned above, antenna profile is an important factor in an SOTM system, as the characteristic radome covering a conventional gimballed parabolic dish singles out a command vehicle as a high - value target. This can be overcome by using a low - profile antenna but with this could result in decreased performance. Opinions differ on which is preferable, and both solutions have their champions.
The radar must physically move in at least one axis to follow the satellite - the other axis could be steered electronically. This is why a radome must at least provide room for some sort of antenna movement inside.
In the United States the US Army Warfighter Information Network - Tactical (Win - T) programme, with General Dynamics C4 Systems and Lockheed Martin as joint prime contractors, includes the SOTM - equipped Humvee - mounted Soldier Network Extension (SNE) node, which uses a 17 - inch gimballed antenna developed by General Dynamics Satcom Technologies. This is part of Increment 2 of the Win - T programme, which is now in low - rate initial production.
General Dynamics C4 Systems has developed a Dismounted SNE (DSNE), which is man transportable and aimed at the heli - borne infantry company. The satcom element is a 96 - cm Warrior Small Man - portable Terminal (SMT) Ku - band satcom system from the GD Satcom Technologies Warrior product line, and which is capable of transmitting data rates greater than four Mbps and receiving data at 18 Mbps. Ka - and X - band options are also available.
The DSNE has an embedded modem and uses GD Satcom Technologies' Smartsat technology, which includes a software - defined controller as well as a positioner that enables rapid auto acquisition of the satellite. The terminal can be set - up in less than five minutes, it has a total weight of 40 kg and can either be packaged as a single transit case or in two manpacks.
In late 2010, General Dynamics C4 Systems was also showcasing a proof-of-concept At - the - Quick - Halt (ATQH) terminal that can operate in X -, Ku - or Ka - band and leverages the company's SOTM technology with a 'smart' positioning pedestal. It will eventually be available in 43,50.8,61 and 76 - cm - diameter reflectors and was designed for installation on a range of vehicles but can also be dismounted.
The terminal has an acquisition time of 63 seconds, achieved by way of its electronics remaining operational while the vehicle is moving, thus making the pointing solution immediately available when the vehicle stops.
Other terminals from the GD Satcom Technologies Warrior range are also used by the US Marine Corps for its Support Wide Area Network (Swan), notably the X - and Ku - band 120 and 180 terminals that are manportable in transit cases, with 1.2 - and 1.8 - metre dishes respectively.
The Rockwell Collins subsidiary Swe - Dish produces a family of small form factor cots terminals using its Communicase technology. These are field terminals with dish sizes varying from less than one meter to two metres which are quick to set up and can be reconfigured from one band to another in the field. A typical example is the IPT Suitcase (AN/USC - 68), which is in the Swan as the Swan Mini. Swe - Dish terminals are also in use with Nato forces, the Indian military and in other Asian countries.
Rockwell Collins has also developed two SOTM terminals. One system, produced since 2005 in co - operation with Saab, has a four-axis pedestal with a 98 - cm dish and has a throughput of up to 20 Mbps on the move. In the other, Rockwell has integrated low - profile electronically steered antennas from Raysat into its Ku - band mSat Mobilink range, which are designed to have a small electronic footprint and be easily transferable from one vehicle to another. The US Army procured a number of these in early 2009 for fitting to Mraps in Iraq.
Rockwell Collins also produces the misat - X, a lightweight, rucksack - size terminal with a 46 - cm dish and up to 1.5 Mbps throughput with X -, Ka - and Ku - band options. This is in operational use with the US Joint Special Operations Command.
ITT'S Global Network On the Move - Active Distribution (Gnomad), launched in 2010, also uses a Ravsat antenna, which measures 114 x 89 cm with a height of 17.8 cm. Gnomad at launch was a Ku - band only system but is expected to provide Ku/X and Ku/Ka - band options by the end of 2011. The system can receive at a data rate of two Mbps and transmit at 512 kbps, while the host vehicle is travelling at speeds claimed to be in excess of 60 mph. Connection to Sincgars or a similar combat net radio network adds a Bios capability to these nets. Intended as a gap - filler for the US Army until the arrival of Win - T, Gnomad was designed to meet urgent operational needs statements raised by a number of US Army divisions, following operational usage in Iraq.
For hand - neid connectivity over a 400-km range. ITTs RO tactical radio pro vides on - the - rnove (and on - the - boots), over - the - horizon communication through the Iridium low - earth orbiting satellite constellation - which, in fact, allows complete pole - to - pole access anywhere in the world.
The RO Radio (see article leading photo) has proven to be a successful solution for forces deployed to Iraq and Afghanistan, this in view of it using the Distributed Tactical Communications System architecture to access the Iridium constellation. ITT has reported supplying more than 6000 RO Radios to the US military to date.
A similar solution has been developed by Elbit Systems Land and C4I - Tadiran with the MSR 2000 system. This is a SOTM Kuband solution that consists of a low - profile antenna and a Burst Mode Frequency Division Multiple Access (BM - FDMA) satcom very small aperture (Vsat) modem.
The antenna, which is designed to be fitted to a range of vehicles, weighs twelve kilos and is 20 cm high. It has a single radiating passive aperture for both transmit and receive bands and is a hybrid, scanning mechanically in elevation and azimuth and electronically for polarisation. The antenna scans continually through 360[degrees] in azimuth, at 45[degrees]/sec; elevation scanning is from 10[degrees] to 80[degrees]. In mid - 2010 it was reported that the Israel Defense Force (IDF) had ordered a number of systems for installation on armoured personnel carriers as well as on Humvees.
Thales developed a hybrid electronic and mechanical X - band SOTM terminal as a private venture which has since been procured as part of the French urgent operational requirement Vehicules de commandEment Nomades commUniquant par Satellite (Venus) to act as part of the ground segment of the Syracuse III programme.
The antenna consists of an active flat phased array with two mechanical axes, giving an effective three-axis stabilised system. Five terminals have now been deployed to Afghanistan, probably on the command variant of the Vehicule Blinde de Combat d'nfanterie (VBCI).
Thales has also supplied tactical terminals for the ground segment of the United Arab Emirates' Ka-band Yahsat programme. The range includes a Ka-band variant of the X/Ku-band Talisman portable terminal, also in use with Syracuse III, which weighs a total of 46 kg (excluding batteries) with a 46-cm dish. It consists of the dish antenna unit, the modem and an Operator Terminal Unit using a Panasonic Toughbook tablet computer. Also included is an SOTM station with a gimballed dish, very similar to those developed for the Win-T programme.
Selex Communications (now belex Elsag) has supplied tactical ground terminals for British forces for Skvnet in the form of the multi-band Talon family. Developed from the original Talon model, which could be carried in four cases, the Talon II is 85 kg lighter than its predecessor and provides a bandwidth of two Mbps operating on the X-band and eight Mbps in the Ku-band. The mini-Talon can operate at C-, X-, Ku-and Ka-bands, packs into three cases, has a one-metre dish and can be deployed by a single operator.
The most recent addition to the family is the Talon-Lite, which was launched at DSEi in 2009. Like its siblings, it is a cots-based product, and is capable of four Mbps in the X-band. It has a one-metre dish, can be packed into two cases and can be assembled by a single operator in five minutes.
It BeGAN with a Wave
Broadcast Global Area Networks (Bgan) are satellite - based systems that bring telephony to satcom terminals, mobile phones and PDAs. Gatehouse, from Denmark, has recently fine - tuned its new software - defined Bgan wave form (an SDR version of the Inmarsat Bgan wave form) and demonstrated its operational flexibility at Satellite 2011, where the company sent calls to attendee's mobile phones and PDAs through an ersatz Bgan terminal running the SDR Bgan waveform. Gatehouse's SDR Bgan wave form currently offers up to 492 kbps of data and 384 kbps of streaming capability anywhere in the world, due to its connection with Inmarsat and the satellite constellation it provides.
In almost direct contrast with information mentioned in Armada's Tactical Radios Compendium distributed with our last issue (4/2011), satcom systems are becoming the sine qua non communications propagative for today's battlefield. With WGS and other satellite launches, the lack-of-bandwidth problem may diminish to manageable levels.
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|Author:||Keggler, Johnny; Jameson, Hugh|
|Date:||Oct 1, 2011|
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