I am wondering what the outcome of this Dissemination Trial will be. It
could have a big impact on the attitude to the provision of high resolution
data, but on the other hand, commercial considerations may prevail. Let me
explain what I mean.

Early weather satellites (Tiros series) were polar orbiters, and carried
their own means of dissemination with them, largely because there was (and
is) no reasonable alternative for such satellites. The main data channel was
HRPT, but for the benefit of people without the resources to install a full
HRPT ground station, a low resolution signal was also produced and
transmitted using the APT channel, which could be received by a relatively
low cost receiving setup. (I am writing here about the situation when the
Tiros series was designed.) When a geostationary weather satellite was
designed, this same principle was carried through, in the GVAR and WEFAX
channels, and WEFAX was sensibly designed to be similar enough to APT that
much of the same equipment could be reused. Of course, in the case of the
GOES and Meteosat geostationary satellites, alternative means of
dissemination could have been used, but the authorities responsible for
these satellites decided to keep control of the whole thing and added
bent-pipe transponders to them which served as the dissemination channels.
The important thing to note here is that the high resolution channel carries
a much higher cost penalty for the user than the low resolution one,
although the differential has reduced a lot since the early days.

What the serendipitous loss of the SSPA on MSG-1 has showed is that this
high vs. low resolution differential is now meaningless from the technical
viewpoint of the communications channel. It is just as easy to disseminate
files containing HR data as LR data over the TV satellite channels now being
used for the trial. From this viewpoint, LR data, that is data whose
resolution has been artificially reduced so that it can be transmitted over
a lower bandwidth and hence lower cost channel, is quite unnecessary and
could be dispensed with.

This conclusion is reached from the viewpoint of the communications, but
there are also commercial aspects to be considered. From the Eumetsat
viewpoint, HR data is probably more valuable than LR data, and users may be
prepared to pay more for it - if this is believed to be the case, the
distinction between HR and LR data may be continued, even though the
original technical reason for the difference has vanished.

Will MSG-2 have an SSPA allotted to the job of data dissemination? Will the
SSPA be omitted or used as a backup for the really important jobs of
satellite control, telemetry and sensor downlinks? Is the TV satellite
dissemination approach the next generation, or will it be quietly dropped
after MSG-1 as it potentially upsets the charging basis for the data?

Alan Sewards
email: alan.sewards@computer.org
web site: http://asewards.free.fr

This conclusion is reached from the viewpoint of the

communications, but there are also commercial aspects to be
considered. From the Eumetsat viewpoint, HR data is probably more
valuable than LR data, and users may be prepared to pay more for it -
if this is believed to be the case, the distinction between HR and
LR data may be continued, even though the original technical reason
for the difference has vanished.

.. and for people taking data over the Internet, bandwidth will
still be a major consideration! Don't forget that LRIT data is
supposed to be available that way, although it's gone quiet on that
front.

Will MSG-2 have an SSPA allotted to the job of data dissemination?

Will the SSPA be omitted or used as a backup for the really
important jobs of satellite control, telemetry and sensor downlinks?
Is the TV satellite dissemination approach the next generation, or
will it be quietly dropped after MSG-1 as it potentially upsets the
charging basis for the data?

.. my guess? They will carry on with the DVB approach, assuming it
is proved to be sucessful, and the current problems can be ironed
out. I suspect the latter is just learning how to make the most of
a new system. Once the eTokens are in place, data access and
charging can be just the same as the existing (direct from Meteosat
7) system. It will be interesting to see if the Americans and
Japanese follow suit. John Tellick has spoken about this at the
recent meetings, so I guess he will have some input!

Cheers,
David

In a message dated 12-10-03 19:38:35 GMT Daylight Time,
alan.sewards@computer.org writes:

Will MSG-2 have an SSPA allotted to the job of data dissemination? Will the
SSPA be omitted or used as a backup for the really important jobs of
satellite control, telemetry and sensor downlinks? Is the TV satellite
dissemination approach the next generation, or will it be quietly dropped
after MSG-1 as it potentially upsets the charging basis for the data?

Alan,

You make some very valid points in your e-mail and your thought are shared by
many, I'm sure, including myself.

Could I please jump in and say, for the time being, that I feel we should be
wary
about discussing this matter till we have some 'real' information as to what
the
future holds?

Yes, the demise of MSG-1's SSPA's have (or could have) put a whole new
dimension
on how meteorological data is disseminated.
Actually, this is not a new idea, the CGMS considered this some years ago.
That is, meteological data dissemination via commercial satellites.

I am aware of the possible dissemination situation regarding MSG-1, 2 and 3
but
this is not official.
I feel it safe to say however EUMETCast (via hot bird) will be with us for
several
years yet.

I wonder if I might be allowed to take your concerns up with EUMETSAT and get

a response before we all throw in our penn'orth.

Regards,
John Tellick.

In a message dated 13-10-03 11:06:55 GMT Daylight Time,
douglas@dsdeans.freeserve.co.uk writes:

just let me add something already
confirmed by Eumestat.
They have stated that the future has still to be considered but that the
current DVB arrangement will continue at least until they have a full
operational set-up with proven, fully working satellites. They have defined
that as MSG-3 operational and MSG-2 in standby.

Douglas,

That has indeed been my understanding for some time now and I, personally,
think that this will be the case.

However I have raised these matters - future dissemination and data policy,
with
EUMETSAT and have been informed that a definite answer cannot yet be given.
The future of EUMETCast is on the agenda for several upcoming delegate body
meetings.

But I have been told MSG-2, 3 and 4 the SSPAs will be modified and the
missions
will be run as planned, this includes L-band dissemination.

We need to remember that EUMETSAT is governed by the EUMETSAT Council
so, dare I say, what EUMETSAT would like to do may not necessarily be agreed
by the members of the EUMETSAT Council.

The next EUMETSAT Council meeting is in November so I hope there will be some
good news to follow.

Regards,
John.