SATCOMMS 1

Today, in 2007, life without satellites would seem very strange, we rely upon them so much. NASA programmes, Television, Telephone, Communications/I.T., Navigation, Portable Personal GPS, Defence, Environments and lots of other things which affect our lives use satellites at some point in their path from transmission to reception. Software programmes are readily available in which one can track every satellite in the sky including military satellites specifically SKYNET: I run one of these called "STS Plus" on my home computer.

If you have read the PRE WW1 Pages on this site [1900-1913] you will know that the early pioneers of W/T were not aware of the ionosphere. They concentrated much of their effort in designing transmitter and receivers to operate over relatively short distances [as compared with distances achieved when the ionosphere was known about and used] in the LF and MF bands, occasionally spilling over into what we call the HF band {1.5 to 24 MHz}, into frequencies up to and including 2MHz only. Thus, by and large, they were using ground waves. Time moved on bringing new ideas, new theories and new knowledge which opened up the full spectrum of frequencies below the ionosphere on a global basis. The frequency expansion encompassed radio waves which would penetrate the earths surface [VLF] through to radio waves which were lost for ever, in and beyond the reaches of the ionosphere namely V/UHF.

It took many more decades and countless millions of pounds Sterling for designers to realise that notwithstanding their brilliant engineering concepts of solid state technology, crystal filers, wideband amplifiers, synthesisers, frequency standards, Wattage leaving the aerial etc etc, they would never surmount the inherent and lasting problems given by the ionosphere even with devices like the Chirpsounder. Apart from the daily and yearly changing conditions apparent throughout the full heights of the ionosphere [from top to bottom] there would always be ionospheric storms, sporadic outages, sun spots, selective fading and the like, which would in some way or another affect our communication circuits IF, that is, the frequencies in use had an interaction with the ionosphere. Frequencies in the VLF, LF, V and UHF spectrums were not affected because they were ground waves or direct line of sight waves {space waves}, but all HF, and thus long haul circuits, were affected. The break through [quite literally] came when scientists realised if a frequency was high enough it would travel straight through the ionosphere and not be affected by it. If they could effect a situation of having terrestrial communications equipment and communications equipment in 'space' far beyond the upper reaches of the ionosphere, they could create a new artificial ionosphere height/level, which would return their signals to earth. This is what they did and the satellite system was born.

They launched satellites into space carrying receivers and transmitters with batteries charged by solar panels surrounding the belly of the satellite. Note that RX and TX are plural. A satellite receives the up-coming transmission from the earth station [terra firma or afloat] converts it to a new frequency, and transmits that as the down-going leg of the circuit back to earth. It has a second receiver which receives telemetry from the earth station monitoring its position, so that if it drifts out of its position, a radio transmission from earth can momentarily switch on a small rocket which will propel the satellite back into position. Finally, so that earth stations can find it, the satellite transmits down a beacon which is used to lock the earth aerial tracking system to the satellite. It gets its power to perform these functions from the sun and its solar panels. When it is denied the sun, the satellite batteries run the show. To complete the picture, they chose frequencies up in the 7-8 GigaHertz band, a group of frequencies never used previously by the W/T Branch.

The introduction of SATCOMS into the Royal Navy at sea caused great excitement. Two complete outfits were manufactured and each could be crane lifted onto a ship requiring the minimum of ships support. These first units had a large communications capacity with a 6-foot single visible aerial [it was not housed inside a radome] sat on top of a Satellite Communications Control Office [SCCO], the office being high and central in the ships upper deck superstructure. It was mounted centrally to get the best possible 360˚ coverage with as few nulls as possible. The SCCO was manned full time by a WE [Weapons Electrical] rating, and the only sign that SATCOMS were fitted as far as the W/T office was concerned, was that extra distribution panels, BID's and TP's were fitted in the RWA bays and two small indicator boxes as shown in this picture.

approached a hazard {ships superstructure} the bleeper would start and very soon afterwards the transmitter would be automatically cut off, even though, if your weren't careful, your autohead [with its page copy from from the BID660] would continue sending the signal. Normally, the autohead {6S6} would be manually stopped in time and the operator would press the mute bleeper button. When the aerial was clear of an obstruction, the AMBER light would be extinguished and the operator would then press the push to reset button, watching for the YELLOW 'Transmitter On' lamp to illuminate. It was a most frustrating system especially when a particularly long signal was nearing the end of its transmission when the system crashed, involving a complete re-run of that message. SKYNET 5 was only fitted onto large vessels and regularly the ships used were the Ark Royal, the Hermes, the Intrepid and the Fearless who took it in turn each to have one of the two operational sets. The rest of the Fleet went without.

The navy's first system was called SKYNET 5 and this file will tell you a little more of the system SKYNET V.pdf. It kept that name for a long period and it wasn't until a new and smaller system was mooted, that it became known officially as UK/SSC 001. The prime British Military satellite was called SKYNET, and it was a geo-stationary satellite placed high above Kenya and the City of Nairobi. Its footprint covered a large part of the earth and the fixed stations were a single 40-foot aerial {20kW} at Oakhanger in Hampshire UK, two 40-foot dish aerials {each 20kW} in Cyprus {one head looking west and the other east}, with earth portable stations in Hong Kong and Gan, each with a single 6-foot {5 kW} aerial. The navy, had these two 6-foot mobile/portable aerials {5 kW} and the army also had a mobile/portable {5 kW} outfit, deployed as necessary.

The picture above indicates how the two 40-foot dishes in Cyprus worked to connect the West with the East.

The geostationary position of the SKYNET satellite turning in the same direction and at the same speed as mother earth..

This picture shows a NATO Satellite orbiting the earth with a 3˚ angle up above the equator producing the footprint above, which, is where one might expect it to be being NATO ! A picture below applies the footprint to a Mercator map of the earth.

Now have a look at this picture again. Below we have added the footprint of SKYNET outlining it in red with the satellite proper smack in the middle of our footprint.. It was a most generous footprint covering that part of the world where Britain still had many interests. It also covered some of the NATO [as was then] areas but when we operated in that theatre, we used either the US or the NATO satellites especially when we went State Side.

Now we ask you! Do you believe in sod's law? Guess where our 1982 enemy is. Yes, youv'e got it, right outside our bloody footprint, so our reliance upon SATCOMS [and ships full of non-Morse Code readers] puts us in a mess, doesn't it? It wasn't that our boffins got things wrong, the footprint, as we have said is truly generous, but that our enemy was in the wrong place at the wrong time.....so to speak. Anyway to the rescue came our good friends the Americans. They had a system called DSCS [Defence Satellite Communication System] which involved a series of satellites [plural] orbiting the earth, each having its own alternating footprint and each doing an automatic hand-over to the next satellite following behind. Thus there was a continuity of communication, and since these footprint covered deep down the South Atlantic and on into Antarctica, we were able to maintain that most critical communications from the Commander Task Force [CTF] back to Whitehall. This picture shows you the pole to pole footprints of the Atlantic and the Indian Ocean US DSCS satellites. We would have to be very uncharitable not to acknowledge that the Americans 'saved our bacon' when we were 'hoisted by our own petard'.

A typical high power satellite was in the region of 100 Watts, and this had not only to travel 36000 kM down to earth weakening all the time, but the power had to be shared between those circuits using the satellite. Ten users, each getting 10 Watts at source [if lucky], resulted in a very poor signal for SGT's [Satellite Ground Terminals] and the measure of efficiency, apart from the RF system {TWT - Travelling Wave Tubes] was the sheer size of the dish. A 40-foot dish collected a large amount of radio waves whilst a 6 foot dish didn't, so it was not uncommon for a SGT to order users to back-off with their up link power which was directly proportional to the power in the down link. Each of these satellites [NATO, SKYNET and DSCS] had two gateways, one known as the 20MHz Access and the other, the 2MHz Access. A ship could operate in either Access, but the norm was for all SGT to Access through the 20MHz area and all mobiles and smaller heads, through the 2MHz area. Here are just two examples.

and

In the picture above taken from a Northern Wedding Complan, you can see the two British Units, the Intrepid with her SKYNET 5 fit and the Blake with a SCOT 1 fit. Both were carrying FLAGS and thus both were considered high capacity ships: hence a slice of the NATO 20MHz Access.

Although we haven't yet started SCOT [Small Communications Terminal], since we are discussing GATEWAYS here is a typical 2MHz Gateway spectrum picture.

Here is an overview of a typical military satellite system

and what a satellite system is designed to achieve in the overall Command scheme of things

We said earlier that SKYNET 5 was a high capacity Satellite System it having two modes of operation. MODE 1 could accommodate 1 secure voice channel, 3 x 75 Baud Traffic Channels and 1 x 50 Baud Engineering Channel, or, in MODE 2, 6 x 100 Baud Traffic Channels plus 3 x 75 Baud Traffic Channels plus 1 x 50 Baud Engineering Channel. It could not have coped with that capacity were it not for its 6-foot dish. The following drawing is of Hermes' fit and shows graphically the system and management thereof. Note that the drawing is showing you four separate areas in the ship with the lift-on SCCO over to the right. In this picture there is a very interesting sequence of events which had never been used to that time and I suspect not since with the advent of SCOT. The ships RWA equipment sited in the MCO, performs as normal giving out of the BID660 an encrypted 1kHz Space. However, this does not go to a TTVF[T] to be converted to Two Tone [Space and Mark] but is re-converted back, by the TT14 sited in the SCCO to normal low level teleprinter voltage {6-0-6V DC} which is used to modulate the SKYNET 5 SHF Transmitter to produce an 85Hz shift at 75 Bauds [the speed of the MCO RWA 6S6 autohead] ready for offering up to the FDME Equipment one of the channels shown in the drawing above. A second and identical transmit channel is shown entering the FDME Equipment. The RATT transmitting picture is completed by the Conventional teleprinter and its TT12 in the SCCO adding its unclassified 50 Baud engineering signal to the 2MHz access as a dedicated channel. The overall transmission path is completed by adding the on-line covered voice circuit coming from either the RSP or the LSP. The BID 820 with the KG13 act as the crypto stream followed by a Line Modulator which prepares the extremely wideband signal ready for RF modulation and multiplexing. In each case, the receiver back path does the same but in reverse with the traffic channels going on to the MCO, the speech channels to the LSP and the engineering terminating in the SCCO manned by WE ratings. Notice [bottom right] the AF baseband which is shown as 300 to 5000Hz instead of the usual SSB technique of 300 to 3300 Hz.

This is the 'hot line' to the P.M., [if necessary] and the type of system used during the 1982 crisis down south.

UK/SSC 001 was a wonderful system and had great potential. As a single aerial system it was flawed and had the Admiralty added a second head, possibly under radomes, large flag ships, where there was enough space to fit this kit, would have benefited greatly. As it was they developed a very much smaller system with two 3-foot heads [in radomes] but with a very restrictive capacity and no options of voice, at least as first configured. It was given the name SCOT which everybody used [Small COmmunications Terminal] but its official name was UK/SSC 002 [1], the start of a series of small satellite terminals. Incidentally, I was partly involved with Hermes with her Skynet 5 fit and knew first hand the system. Not too long afterwards I was back at sea in the cruiser Tiger with a SCOT so any comparisons I make are tempered with first hand experience of both systems.

The first and obvious change was that it had two aerials set in such a position that at least one of the aerial could see a satellite - except when most needed in the Falklands until that is, the Americans stepped in. There follows some pictures of a single aerial without its radome, aerials as fitted into ships [typical examples], the aerial fit with the SEC [Satellite Engineering Cabin] - unmanned] and the aerial technology,

This is a picture of the cruiser HMS TIGER, at the time I served in her in 1977/8.

Almost immediately above the pennant number of C20 [painted on the port side below the superstructure] are the two radomes [which look rather like electric light bulbs] within which are the port and starboard 3-foot dish aerials feeding the SCOT system. The following picture zooms in on that area.

and the following two pictures show how it worked to basic block diagram level.

The aerial cables had of course to follow the tracking of the aerial and would therefore wind-up in one direction and attempt to unwind in the other. This unit, placed strategically on the bridge and in other important positions, had lamps sequences which illuminated. When the lamps were illuminated it told the Command which way the aerial cable was wrapping and therefore which helm to use to unwrap the cable. The aerial had a ± 270˚ training capability. The elevation was set by hand on information received from the MCO. It didn't change much from day to day.

The indicator arm showed the azimuth of the aerial and whether the transmitter was on or off - important for RADHAZ, especially if a HELO was in the hover in the immediate vicinity of one of the aerials.

That was the next big difference in that the SCCO had become a small SEC [Satellite Engineering Cabin] and it was not manned on a continuous basis, but used when defects needed to be rectified. Because of this, the main control panel was sited in the MCO and became a piece of equipment which some of the radio operators operated. Thus there was a highly visible presence that satellite system was embarked, and yes, it came with extra bays, distribution panels, BID's and TP's. This file shows the SCOT control cabinet. SCOT 1[1].pdf

In the early days of SCOT, SKYNET 5 ran as a parallel programme. The fitting programme was similar to SKYNET 5 in that a crane berth was required and the whole thing was lowered onboard and bolted into place - so for the same reason, it could be taken off and given to another ship. The majority of ships were FFBNW [fitted for but not with] so the whole idea was flexibility, and if a FFBNW ship was assigned a SCOT, whilst it was being fitted, the crew got their PJT [pre joining training] package at that time. Everything worked well, except, as I say, with a much smaller system than the big ships had been used to. At least we didn't have to suffer 'wooding' which made the previously mentioned system crash whenever the single SKYNET 5 aerial was about to 'blister the upper deck paint work' ! On the big 7 months deployments in the 1960's and 1970's when a flagship of cruiser size {when at all possible} would take a group of seven or eight ships to the Far East for exercises and to show the Flag, only the flagship and Captain 'F' would have SCOT fitted. During Group 6 deployment in 1977/78 [which covered the Silver Jubilee] Tiger, the flagship, was fitted and Cleopatra, under the command of a Captain Royal Navy. This worked well when the group was together, because Tiger was running a Task Group Broadcast [receiving messages from Whitehall via satellite for all ships and passing them on via local W/T circuits] and ships in company had no worries about not being able to receive HF RATT Broadcasts, which was a problem - Cleopatra was also using SCOT. However, when individual ships were sent off to show the Flag in small ports losing touch with the flagship all was not well, indeed, Cleopatra took herself plus one other vessel and went off for two months to Japanese waters, and there her SCOT failed. It remained out of action until she returned to the pack. The hapless Cleopatra, and for that matter the Tiger too because we were helpless thousands of miles away down in Sydney NSW and couldn't help, survived by going 'cap-in-hand' to the Americans. The days of Singapore, Hong Kong, Ceylon West, Mauritius, Cape, were long gone, and whilst the Americans were still active in Subic Bay [Philippines] and supporting dear old Cleopatra, their days were numbered too because of civil mutterings [too much rent was being asked for the base]: finally, a massive earthquake which made the base unusable, made the leaving decision for them and they up'ed and left.

This event, if nothing else made everybody aware, certainly in Group 6, that SATCOMS were the future, although then again, we knew that the days of the Royal Navy going here, there and hither were also over, so did long haul communications really matter?

Other SATCOM System are now employed in the Royal Navy and the UHF Frequency spectrum is used with up links usually in the range of 295-320 MHz and down links 240-280 MHz. Submarines and other vessels can use this system for both secure voice and low bit data channels.

INMARSAT is used quite extensively by the Royal Navy and all RFA's are fitted plus 'specialist' warships.

SCOT specifications were issued as follows, and as always, things got better as more 'goodies were added'. See SSC 002.pdf and SSC 003.pdf.