Comsats in turn come in two different types
Low Earth Orbiting (LEO) are
of the same class that will be used for future systems intended
to bring Global hand-held phones
that fit into the back pocket and work just like a 'portable'
'mobile phone'. Though
scheduled for availability in 1998, they may not be working until
the first decade of the next century.28
There is also a Packet data system by LEO
satellite, with the satellite
acting as a world roaming mailman beaming messages up and down
as it passes. The system is very cheap to run and was invented
for the benefit of aid agencies with low budgets.
There is information about this in the appendix,(see SatelLife
and VITA). We will come back to LEO systems later, but for now
let's get on with Geostationary systems.
Since then however, many more land based users have started to
use the system, so the terms Land Earth Station (LES)
can be used instead of CES and Mobile Earth Station (MES)
instead of SES. Do not be confused if you see these words, they
are exactly the same thing as before, but by another name. The
only difference is that SESs tend to be physically larger and
are intended for permanent installation on board a ship. The other
difference is that ships tend to wallow about while the call is
in progress, so the antenna dish (protected by a
egg shaped radome) needs to have a complex and expensive
tracking system to keep it pointing at the
satellite as the ship rolls and pitches around, and as it changes
course.
Most new MES's tend to be fitted inside briefcases and have disassembled
antennas. this is why they are much cheaper and smaller, though
their function is the same. It is taken for granted that an MES
user will not move the dish once it has been assembled, therefore
a tracking system is not required. Most also have removable antennas,
which gives highly desirable flexibility. You can put the antenna
outside, and make your call inside in the dry and warm.
The INMARSAT system utilizes four geostationary satellites and
about 80 land earth stations dotted around the world and operated
by various Telecomms companies. The British CES is 'Goonhilly'
and is operated by BT. The MES (our kit in the field)
links up to the satellite, then down to the LES and then into
the normal Phone, data, fax or TELEX system.
One awkward thing is that someone calling the MES has to dial
a code for the correct satellite first,
so the MES operators need to let everyone know which one his dish
is pointing at. This is important because in many places in the
world, such as Africa, two satellites are in view
and either could be used. The choice will depend on where most
of the calls from the MES are intended. The MES operator will
consult his operating manual for this information,
then inform all potential callers of the dialling code change
to reach him. However there are some LES stations which try both
just in case, ask your LES if in doubt. Another drawback is that
the system won't work at all above about 70 degrees north or south.
However since this is above the arctic and antarctic circles,
you are unlikely to be working there without expert guidance and
special equipment.
* NOTE
By far the biggest problems are not technical, but political.
Some countries ban the use of any land mobile satellite
equipment on their territory, or take up to 7 weeks to grant a
licence, charging up to hundreds of USD per year
for a licence for one terminal. That is a worst case scenario,
usually it is much better than that, and the rules vary from country
to country and day to day. The good news is that they may
make an exception for Emergency
relief and disaster mitigation units, in which case a fast track
method must be employed. (See Licensing Chapter 5.) There is
more information in the appendix.
There are 4 completely different System Technologies for INMARSAT
at the moment, (though INMARSAT are working on another more advanced
LEO version also, under the name ICO, (formally INMARSAT-P), to
be introduced around the year 1998). The existing
system technologies in 1996 are:-
This one has all the 'bells and whistles'. It can handle telephone
calls, by direct dial in and out, and the calls
are always of very good quality. The lines are so clear that the
channels can also be used to send Data via a modem
or if you have the high speed data option,(so it can support Electronic
Mailing), or FAX. Built in circuits in the MES makes
the terminal output look just like a phone line,
so anything that can connect to a phone line will just plug straight
into the INMARSAT-A with no modifications needed.
It can also connect into a switchboard and be available to many users via a field telephone system. INMARSAT-A supports Full Duplex TELEX (this means a two way conversation could be held by TELEX).29 It is reliable and easy to use. The latest equipment also enables the sending of full motion video (though not in real time) and good quality colour stills, with the installed 56/64 Kb/s high speed data option via ISDN. As a security precaution against unauthorised use, most terminals offer systems such as separate passwords required for each authorised user, with separate logging for each one.
The older equipment is quite big and heavy, being the size of one or sometimes two large suitcases and weighing about 30kg. Newer models weigh about 18kg, not including auxiliaries and generator.
It needs mains power (or a generator or inverter which are also big and heavy) and it can't be used on the move.
It is also the most expensive system. A typical unit may cost
about 20,000 US Dollars or more for the High speed data options
and calls cost about USD 6-8 per minute peak, USD4-5 off peak.
( see appendix for details)
Most manufacturers have discontinued development on standard-A now, so it is likely to be left behind in the technology race in the future, though they will continue to support the existing models for many years hence.30
This is the digital replacement for INMARSAT-A. It can do all
the things that INMARSAT-A does, Phone, Data,
FAX, TELEX, but at much lower call charges.
This is achieved by more efficient use of the satellite and power.
It can also provide high speed data links
by ISDN services, but as these are more interesting
to broadcasters and industrial users, because of their having
higher budgets, I will not talk about them much more. However
I am watching with great interest.
There are many different manufacturers in this field and INMARSAT-C
related products continue to be developed and will continue to
be improved upon for the foreseeable future. The system is very
reliable and much loved by professionals everywhere. For example
it is used by the UNDHA, MSF, Red Cross and dozens of others.
Unlike most other system satellite systems (except standard-M),
it can also be used on the move,
such as if fitted to a Land Rover, if non-directional antennas
are used. There are also many models looking like a briefcase
with the antenna built in to the lid.31
Text messages can be prepared off line by a Personal
Lap Top Computer with
all the huge advantages that users of PC will be familiar with
as regards word processing. Power requirements can typically be
met by batteries such as vehicle batteries.
The equipment is usually very tough and highly reliable.
The latest application is for a remote version of CC:mail, a popular
electronic mailing system. By use of the system, a person with
an electronic mail account can continue to communicate from his
account even from a remote location.
It is the cheapest satellite system costing around USD 5,000 per
unit and calls costing about USD 2-3 per average message. Automatic
Notification of delivery of message
costs about 20c. Importantly, it uses little power and can run
off batteries for days.
It is a little harder to learn to use, and doubly so for any person
not computer literate as a laptop PC
is usually the terminal. Those familiar with word
processors will find it similar to use, only you press transmit
instead of print when you are ready to send.
The whole system is only as reliable as your 'lap top' or terminal.
The Standard-C gear is very tough but less so the drives
in the laptop, you must purchase only the most trusted model or
the system will not work, anyone who travels with 'lap tops'
regularly will know what I mean. Good training
and thorough preparation is a 'must'.
The same applies to power, you must keep the batteries
charged in your PC, and budget your power wisely. Only experience
will teach you the tricks you will need before you feel confident
with your Lap Top PC. You must avoid the temptation to play games
on your lap top in the boring evenings.
When in TELEX mode it does not sport full duplex
'chat back and forth' operation but can only send a message and
then wait for a reply. This is called the 'Store and Forward'
method.
INMARSAT-M is a direct dial in and out phone
service via PSTN. Its designers wanted it to be the
nearest thing to a mobile phone possible with geo stationary satellites,
so its very easy to use and easy to teach. The cost of calls on
standard-M is about half that of standard-A, at around USD 5.00
per minute or lower. The MES terminals are fairly compact by comparison
with INMARSAT-A, or -B, being about briefcase sized and weighing
about 10kg as opposed to the suitcase size and 20kg for standard-A.
Some later versions will be able to work from a moving vehicle.
It is also able to send and receive FAX by the use of
optional special circuits built in, a special separate socket
and a separate phone number is then allocated to the fax socket
on the terminal. By the middle of 95, it is expected to support
DATA at the rate of 2.4Kb/s.
Some INMARSAT-M terminals can also be powered by their
own internal batteries for 8hrs on standby
and 1hr talk time. Being a new service many manufactures are still
making them better and better yet, so we can expect quite exciting
things from standard-M until it is superseded by the future LEO
systems after the turn of the century. There has now been a few
years experience with the system at time of writing, UNHCR and
Red Cross are examples of organisations using the equipment and
are reported to be very pleased with its reliability, some 7,500
were in use in by 1995.
The only thing against is the initial cost of the equipment, which
will sell for around USD 15,000 plus tax. It is still subject
to the same political problems as all
other satellite systems, namely that the equipment may be banned
or a very large customs duty be required. However the situation
is better than for INMARSAT-A because of the lower emitted power
from the unit. However it is rather slow in FAX mode, taking four
times longer than standard A to send the same page and therefore
costing twice as much.
=REPORT=REPORT=
One big problem for operators
using this equipment is that it is the victim of its own success.
It is so easy to use and gives such clear lines that a user can
be seduced into dropping into a relaxed telephone style and taking
10 mins to say something that could be said in 3. When you get
your first bill from one of these you could wish that you hired
a team of Trappist monks. Three weeks of using one standard-A
terminal in Zaire for the Rwandan operation cost the UNDHA CHF
29,800. Data or FAX modes are much more cost efficient than voice
so they must be encouraged. As in all things, training and discipline
pay off in the long run.
With the advent of Electronic Mailing, Internet and the
World Wide Web, there is more and more interest in data over the
Inmarsat system. Standard-A can support ordinary modems without
modification but only certain models seem to work well, you must
ask someone experienced before you choose your model. The others
systems also offer data services but there are special complications
that you must know about. My research on this topic is ongoing
at the time of writing and so I have given a summary in the Appendix
about my findings so far. At the moment you need good advice and
support for serious use.
This is a rather exciting system whereby a trucking company manager,
for example, can have an electronic map of the world in his personal
computer, showing the position of all
of his trucks and giving information about their status e.g. what
they are loaded with. A further facility is that the manager is
able to type a message into his computer, and have that message
go immediately to one or all of his fleet.
However this is not a separate new network as such but is a clever
combination of GPS ( Global Positioning System
) to give the truck's position and INMARSAT-C
to transmit the position and other data about the load to the
management centre and to dispatch orders to the driver from the
management centre, the data being processed separately by software
running in the company's own P.Cs.
It seems that the Air Traffic control Authorities
are interested in this technology to supplement radar surveillance.
The air version will be known as Automatic Dependent Surveillance
(ADS). Traffic controllers
are very, very cautious people, so if they are considering it,
then this is a measure of it's state of maturity.
Regional systems are usually implemented by only one satellite
rather than several. Furthermore, the antennae on the satellite
beam the energy into one area on the ground, known as the 'footprint'
or 'zone'. Regional systems don't offer global coverage but rather
only in the area inside the footprint. Each footprint can be very
large, encompassing a whole country or economic group, for example.
In the American Mobile Satellite Corporation
version, one zone covers the whole of the East coast two further
zones cover the midwest, while another the West coast of the USA.
In that system, several zones are connected together to offer
system coverage of the whole of North and Central America.
The charges for regional service are usually very much lower than
for global systems, by half as much, So as long as you are sure
that you will be working in the covered area, a Regional system
may prove to be the most economical. It is thought that many new
systems will emerge, so it is worth while checking the situation
in your region frequently.
Very few people doubt that the LEOs are by far the
most important development in disaster Telecommunications in
the near future. The very successful introduction of the 'mobile
phone' systems all over the world have stimulated
a demand for personal communications which is as unquenchable
as it is profitable for the operators of these systems.
Normal mobile phone systems have the problem that they are provided
by ground based 'Base Stations'. These need
to be carrying at least 8 calls at a time in order to be economical,
yet their range is limited to about 35km, so they are usually
only provided in urban areas. Satellite systems have the disadvantage
that they need bulky and usually fixed antenna systems to make
them work, so this makes them hardly 'handy' and certainly not
'portable'.
The solution is to bring the satellites much lower to the ground
(300 km) and so able to be contacted with a more convenient antenna
suitable for mounting on a hand held 'phone. The problem is that
1) you need far more satellites to do this as each can now 'see'
a smaller area. 2) they move much faster across the sky and so
loose contact with the user after a few minutes, thus requiring
'handover' systems not unlike those used in mobile
phone systems.
The different operators who have so far declared themselves (Iridium,
ICO, Globalstar and Odyssey)
each have different systems technologies for solving these problems,
and need anything from 12 to 84 satellites to achieve global coverage.
At the moment I don't know which of them will be the most successful
and the technical differences are mostly of interest only to techno-buffs.
One thing I do know is that if they work as well as promised,
and cost as little to operate as promised, then they could make
everything else obsolete overnight! It is an open secret that
the big Mobile phone makers, Motorola, Nokia
and Ericsson are all spending a lot of money on
developing 'dual standard' phones designed
to work on the new LEO systems. The idea is that the phone will
act as a normal mobile phone in an area where
the system is provided. However it will automatically switch
to the satellite system if either you have strayed out of the
area where the system is provided, or if the normal system is
out of order, for example because it has been destroyed by a disaster.
To add to the attraction of this very convenient personal communicator,
all of the operators promise high speed data applications
for their systems. There will also be built in position finding
in the phones so that you won't need to carry a separate GPS
receiver. You will have Phone, message pager,
Data terminal and GPS in one hand held unit,
all of which could be immune to damage from a disaster no matter
of what scale.
The problems facing the new systems are that each is a very ambitious
new technology, so progress with bringing their products to market
may not be as rapid as they are forecast now. Each has pledged
to start launching in 1998, which would put a strain on the world
space launcher industry even assuming no
hitches at all.
Coverage may also be a problem in that signals may be too marginal
to work inside buildings at all. It may be that you would have
to be outside, with a clear view of the sky, to make a call. There
could be severe hitches with data transmission at first as the
air interface will be much more variable.
By far the biggest problem may be political. A government may
see the system circling overhead as piracy or even
technological imperialism. Persons could make calls from a countries
sovereign territory without needing any government provided facilities,
without asking and without paying a penny to the national purse.
There are enormous diplomatic and political problems for the operators
of the LEO systems to resolve. Probably for quite a while, there
may be countries where use of these phones is prohibited or very
large licence fees may apply. In fact a situation exactly the
same as applies to the INMARSAT system now.
These are the promises and the problems, we will have to wait
and see if it will be delivered. In any case a full service is
unlikely to be working until around or after 2000-2010.
It seems that most of the space operators are concentrating on
fax, data and conventional telephony applications for their terminals.
However there are some limitations with conventional telephony
which we need to be aware of.
By phone, you can only talk to one person at a time. In the case
of a large scale disaster, you may need to share information and
ideas with as many as 10 persons at a time. If you had a three
minute message to send to 10 persons, this will take you half
an hour, presuming no hitches at all. This will cost you USD150
on call charges and use up a lot of your time that you need to
spend on more important things. Even a conference call
is not the answer as you will not be able to talk to 10 mobiles
at once, and in any case you will be charged air time for each
mobile, the bill could still be huge!
This is why such authorities as fire brigades don't use mobile
phones even though they could afford them.
With open channel systems, when one
station speaks, all the others hear also, so that information
is passed around in real time. When a station is now called for
comment, he will not need a briefing as he has been getting a
rolling briefing the whole time. This means that important officers
can be out in the field putting their experience to use instead
of sitting in a briefing room reacting to old news and smiling
at the media.
In the past this was done by VHF repeater networks
which were sadly, very short range. Around 50 KM was normal. But
now this type of service is available by satellite with a resulting
much larger range.
It seems to me that if all NGO's shared the same
global satellite system which offered both data/phone and also
this dispatch service, then co-ordination would be much easier.
Units could join and un-join groups as they need
in order to work together better. Also in dispatcher systems,
there is no charge for air time of the satellite,
rather a fixed monthly charge for activation of this service.
This would keep the costs under strict control while removing
monetary barriers to the more extensive use of these systems.
This is my private view, but I acknowledge that many people
I respect have different views.
28Estimates vary from 1998 to 2010.
29However it is wise not to use the direct telex mode because it is very expensive to hold a conversation this way, with people thinking and then typing the answer. Better to send a message then go off line and wait for a response.
30INMARSAT promises to support Standard-A until at least 2005.
31These days the term transportable means man carryable but not intended to be operated while carried in the hand.