Group for Earth Observation

The Independent Amateur Quarterly Publication for
Earth Observation and Weather Satellite Enthusiasts

Number 18
June 2008

Inside this issue . . .
Ed Murashie presents
part 3 of his series on
GOES LRIT. This time, Eddetails the LRIT structure
and processing, amply
illustrated with helpful
flowcharts.
Interference has always
been a bugbear for thelegions of APT enthusiasts.
Alan Sewards provides an
update to his seminal
article on the subject,detailing the causes andproviding illustrations toassist recognition of thelikely source.
The cover image at left
depicts a spectacular sandand dust storm that swept
across eastern Europe last
March. A team of GEO
observers followed its
progress and helped to
produce our illustrated
report on the event.
Douglas Deans presents thefirst of his new-style
columns devoted toproblems readers experience
with their computer
systems.
There are also articles
dealing with MODIS
imagery, the Russian Buran
shuttle, an update on theAral Sea and much more ...

Keep up with the latest
WXsat News every Month
Radio and Communications Monitoring Monthly (ISSN
1749-7809) aims to be the magazine of choice for all
serious radio enthusiasts and to serve all the
specialist areas of the hobby. ‘I am pleased to saythat all our regular columns provide more information
than any current or former alternative’, commented
Editor Kevin Nice.
The magazine provides a regular 4-page Weather
Satellite column, Satellites' View, by Lawrence Harris.
Radio and Communications Monitoring Monthly isavailable from most good newsagents as well as
direct from its publishers.
Subscriptions are available world-wide.
For more information contact Nice One PublishingLtd,
Tel: +44 (0)1202 862690 or visit the website.

www.monitoringmonthly.co.uk

MANAGEMENT TEAM
Public RelationsT

he eye-catching satellite image on the front cover of this issue depicts an
exceptional dust storm that transported huge quantities of sand from theeastern Sahara desert, over the Mediterranean Sea, and deep into eastern
Europe. Several readers made reports, both from satellite imagery and theground, and these form the basis of our article on page 33.
he GEO Survey we asked you to participate in last issue has been a total flop
thus far. By mid-April only 11 readers has bothered to respond. Suffice it to
say that the GEO Management Team is bitterly disappointed at this show ofapathy from the readership. You can read more on page 3 explaining why GEO
requires your input. The survey remains open for GEO Quarterly readers atT

http://www.geo-web.org.uk/survey08.html

Ed Murashie’s series on LRIT has already engendered interest and his latest
offering appears on page 17, where he gets to grips with the structure of the
LRIT transmissions and describes the software he has developed to decode thesignals. Ed is keen to hear from fellow enthusiasts interested in developing LRIT
systems.
espite the popularity of EUMETCast, good old-fashioned APT remains one of
the mainstays of our hobby. The downside is, of course, that the VHF NOAA
transmissions are prone to interference. Some years ago, Alan Sewards compiled
a seminal report on identifying and dealing with interference, and this used to beavailable on the EUMETSAT website. This version is no longer available, but
Alan has kindly updated his article for GEO readers (page 25).
inally, apologies to the two dozen or so readers whose copies of
GEO Quarterly 17 contained missing and duplicated pages. All have been
provided with replacement copies. We hope this has not spoiled your enjoymentof the issue. This was a production issue outwith GEO’s control.

D
F

Francis Bell,
Coturnix House, Rake Lane,
Milford, Godalming,
Surrey GU8 5AB
England.
Tel:
01483 416 897
email:
francis@geo-web.org.uk

General Information
John Tellick
email:
info@geo-web.org.uk

GEO Quarterly Editor
Les Hamilton,
8 Deeside Place
Aberdeen AB15 7PW
Scotland, UK.
email:
geoeditor@geo-web.org.uk

Membership and Subscriptions
David Anderson,
35 Sycamore Road,
East Leake,
Loughborough LE12 6PP
England, UK.
email:
members@geo-web.org.uk
Tel:01509 820 067
Fax:
01509 559 015

Meteorological Consultant
Peter Wakelin
email:
meteo@geo-web.org.uk

Technical Consultant (hardware)David Simmons
email:
tech@geo-web.org.uk

Webmaster and Website Matters
Ray Godden
e-mail: ray-geo@lescharriols.eu

Education Coordinator
David Painteremail:
education@geo-web.org.uk

Contents
GEO Report
Dismal Response to On-Line Survey
Satellite Imagery in GEO Quarterly
Australia in APT
The Current Weather Satellite Scene
Satellite Direct readout Conference - 2008
Receive APT on the Apple iMac with WxToImg
GeoSatSignal Animation Update
A Shopkeeper’s Tale (GEO Shop Update)
MTSAT-1R Images on EUMETCast
Zoom in on the Earth with MODIS
Report from the UK Space Conference
EUMETSAT ‘Satellite Images of the Month’
GOES LRIT - Part 3: Software

GEO Shop Manager

Francis BellGEO Editor
Les Hamilton
David Donnelly
Laurence Holderness
NOAA
Fred van den Bosch
Terence Smith
Clive Finnis
David Taylor
Les Hamilton
Francis Bell, John Tellick
David Lee
Ed Murashie

2
3
4
4
6
7
7
8
9
9
11
15
16
17

GEO Shop Page
NOAA Satellite Predictions for the UK and Western Europe
Helplines and Internet Discussion Groups
Copy Deadline for September issue
GEO Membership Renewal Form

i
ii
iii
iii
iv

Earth Observation NewsInterference to APT Satellite Reception
ForumsSatellite Communication Systems’ Link Budgets
Aral Sea Update
Saharan Dust Sweeps across Eastern Europe
Bolshaya Ipelka
Buran - the forgotten Soviet Space Shuttle
GPS in Weather Satellite Stations
Cover and Full Page Satellite Image details
Pigeons in my Meteosat Dish
Computer Corner
In Tray - Reader’s Letter

23
25
28
30
32
33
36
37
38
39
39
40
43

Peter Wakelin
Alan Sewards
Fred van den Bosch
Alan Sewards
Les Hamilton
Compiled from GEO Members’ Accounts
Les Hamilton
John Tellick
Rob Denton
Anthony Lowe
Douglas Deans

Clive Finnis
email:
shop@geo-web.org.uk

International LiaisonPeter Green‘Hollowtree’
Eggesford
Devon EX18 7QX
Tel:
01769 580 700
email:
international@geo-web.org.uk
Nigel Evansemail:
nigel@geo-web.org.uk

Publisher
The Group for Earth Observation Ltd
The Group for Earth Observation Limited is acompany in England and Wales limited byguarantee and not having share capital.
Company number 4975597.
The registered office is Coturnix House,
Rake Lane, Milford, Godalming, Surrey
GU8 5AB England.

Printing
Advent Print Group,
19 East Portway Industrial Estate,
Andover,
Hampshire SP10 3LU.

Responsibility
Every effort is made to ensure that thetechnical and constructional articles
published in this Quarterly are correct.
However, the ultimate responsibility is withthe reader to ensure the safety of
constructions and for any interfacing withother equipment. GEO cannot accept liability
for shortcomings in any published design or
any constructions carried out by members orother third parties.

Copyright GEO © 2008
The contents of this Quarterly remain theintellectual property of the Group for Earth
Observation Ltd. and its contributors.
Copying of text or images, either from theprinted Quarterly or from any electronicallystored source, is forbidden without
permission from the GEO Quarterly Editor.

GEO Quarterly No 18

Group for Earth Observation

June 2008

Francis BellMy usual welcome to new members of
our group and of course thanks tothose established members who haverenewed their membership. We doneed a strong membership base, notonly for financial reasons (because wehave no other source of income otherthan our members subscriptions) but
because we need a substantial numberof talented people in order to interact
with those national and international
agencies who are responsible for Earthobservation and the subsequent data
dissemination. With these objectives
in mind, please do not forget yourrenewal when it becomes due.
It’s GEO management policy to attend
conferences and meeting where wethink it is beneficial to both theorganisers and to GEO. There is areport on page 15 about GEO’s
presence at the UK Space Conference
held in Godalming, Surrey.

Snow Thwarts GEO

University of the Third Age

Disappointingly, GEO missed theSpring radio and computer rally at
Kempton. Apologies to everyone. Threeof us were ready to attend, with carsloaded, when it started to snow heavily
at about 8.00 am and radio reports
indicated traffic problems on some of
the main roads. It was a disappointing
decision, although correct at the time,
as we decided not to go. I hope we will
be at their Autumn rally.

Last year, I gave a talk to the local
branch of the University of the Third
Age (U3A). I guess it was well received
because I was asked for another talkthis year. As usual, I try for live
weather satellite reception, which does
require planning and resources, but isworthwhile because live images do
generate interest. Keen not to offer arerun of last year, I invited Storm
Dunlop to show his images of ‘Weather
from Above and Below‘, photographs ofclouds and meteorological phenomena
taken from the ground in combination
with images received from weather
satellites. Storm, who you may
remember is the author of many bookson the weather and clouds, readily
agreed, and his presentation was wellreceived by the 35 members present.
GEO’s live display and literature
handouts also created worthwhileinterest. Thanks also to John Tellick
who came and supervised technicalmatters for us.

Our Leicester symposium will be overby the time this Quarterly is
circulated. At the symposium I always
publish our accounts and haveavailable an up-to-date statement ofmembership numbers. For those notattending, the figures areapproximately• Money in bank £13,500• Cost of a Quarterly publicationand its distribution £2,400 per
issue• Total membership is about 530,
three quarters in the UK.
I hope most of the above comments
have been positive and forward
looking. However, there aredisappointments.

The GEO Stand at the Space Conference

Looking at the coming months I notice
there is an International Astronautical
Conference taking place in Glasgow
from September 29/October 3, 2008.
Perhaps some of our Scottish members
would be willing to attend andrepresent the interests of GEO together
with some display. See
www.iac2008.co.uk

A very high priority for us must be the
NOAA Direct Readout Conference in
Miami next December (see page 7).
GEO must interact with NOAA if weare to keep abreast with developments
within their programmes; also NOAA
may wish to know about the usergroup which GEO represents. I havebeen to the equivalent of thisconference twice before.
[Francis and Nadine Bell are planning
to attend this conference to represent
GEO and illustrate the talents andactivities of our organisation—Ed]

2

The lack of feedback and involvementfrom many members to the website
questionnaire—which took a lot ofeffort to design and establish—has only
generated a trickle of replies (readmore on page 3) and raises thequestion: ’Why bother running GEO?’The GEO Management Team are fullycommitted to the organisation but I
also know that for some, their timecommitment is at saturation level.
These are issues which will be
discussed at Leicester.

Storm Dunlop speaking at the U3A

www.geo-web.org.uk

If GEO are invited to the AMSAT-UK
colloquium scheduled for July 25-27,
2008,we will do our best to attend. In
the past we have put on live
demonstrations of weather satellite
reception and given talks in theirlecture stream. Our last issue showed
incorrect dates for this event.
The dates shown above are correct. I
hope this error did not inconvenienceanybody.
EUMETCast Matters
At home here, I continue to experimentas I expect most of us do. Hearing astory that there was reduced signal
strength coming from EUMETCast/Hot Bird-6, I immediately deployed
my smallest dish, measuring about 40
cm in diameter, but still received avery strong signal: so if there was a dip
in the signal strength I missed it.
Experiments continue on other aspectsof reception; I keep getting missing
segments and don’t know why. Well it
will keep me occupied and an excuse
for neglecting the garden.
Hampshire Brownies
Together with the local amateur radio
club, GEO provided a small
demonstration to a Brownie group in
Hampshire. Once a year the Brownies
have a ‘Thinking Day on the Air’ which

June 2008

Group for Earth Observation

GEO Quarterly No 18

involves live amateur radio contacts and the use of theInternet. Even at a very young age these Brownies did takean interest in the live images of the Earth which were also
on show.

From the Editor
One of the first items you would have read after opening
your March 2008 copy of GEO Quarterly was a request to
help GEO, and your editor in particular, by completing our
on-line survey. Rather than write a tirade of invective todescribe the outcome, I’ll let the figures speak forthemselves.
Only 11 readers, at the most, 2% of of the GEO
membership, took the opportunity to make a return

This photograph shows from left to right Francis Bell, Tansey,
Hannah, Lucy, Jessamy and District Commissioner Louise.

While there is never the expectation of a 100% response,
this dismal effort is a real slap in the face for GEO’s
Management Team, and particularly myself, as we strive toprovide you with relevant articles on topics of interest toyou.
As editor, I put in between 150 and 200 manhours on every issue of GEO Quarterly; I hardly
think it is an imposition to ask readers toreciprocate by spending five minutes or so of theirtime completing our on-line survey!

My thanks to those members
who took an interest in the
March Quarterly Question,
which asked whether any partof mainland Iceland was within
the Arctic Circle. The answer is
no. The most northerly point in
Iceland is Hraunhafnartangi
which is 3 km short of latitude
66 degrees 32 minutes north.
However, the Arctic Circle does
cut through the offshore islandof Grimsay.
Of course I asked the question
because the answer was likely
to be marginal: that is just 3 km
short of the Arctic Circle.
My thanks to the following
members who submitted acorrect answer: Rob Denton(Bulgaria), Colin Cox (England),Aime De Grysé (Belgium), Erick
Thirkell (Scotland), Mike Bragg(New Zealand) and Andreas
Lubnow (Germany).
The June Question
The current Quarterly Question
was prompted by my reading
the British National Space
Centre’s (BNSC) recent
publication Space:UK, issue 23,
which contains a short article
about the Earth’s atmosphere,
and where it stops and space
begins. Most of us are used toliving in our atmosphere with apressure of about 100 kPa. Thispressure reduces steadily withaltitude above the Earth’s

surface, and the question is:‘When does atmosphericpressure become zero, or,
putting it another way, where
does space start’.
This rather indistinct boundaryis called the thermopause andis defined as the distance fromthe Earth where any particle
present is just as likely to drift
off into deep space as it is tostay associated with the Earth.
This boundary is likely to vary alittle according to solar activity
so I will happily accept plus orminus 10% of the reference
answer. I will use as thereference answer the figure
published in Space:UK, where afigure, in kilometres above theEarth’s surface, is quoted. I
expect many other space
related reference books will
quote a similar figure.
A clue to the answer:
surprisingly the International
Space Station would not qualify
for being in space with respect
to the thermopause althoughgeostationary satellites would
qualify as being in space. Whatabout polar orbiting weather
satellites? Decide for yourself!
Please email answers toFrancis Bell at
francis@geo-web.org.uk

Why do we need your input?
The face of weather satellite imaging has altered radicallysince GEO first appeared on the scene in 2003. For thosewith plenty leisure time, EUMETCast provides for their every
need: non-stop Meteosat animations; geostationary images
from around the globe; NOAA HRPT images of the UK andEurope; plus planet-wide imagery from Metop-A. And
GEO Quarterly has dealt with all these matters at
considerable depth over the years.
But, as Laurence Holderness’s piece on page 6 illustrates,
not everyone fits into this category. There are readers who
are uncomfortable downloading this tidal wave of data into
their PCs. We have to cater for those with less demanding
requirements too, specifically to retain our current
members, but, even more importantly, to encourage new,younger enthusiasts to the fold. A recent survey carried out
by our Dutch counterparts, Werkgroep Kunstmanen (where
over 30% replied to their survey) showed one worrying
feature—they had only five members younger than 50 yearsof age. Judging by those who have attended GEO Symposia
over the years, it is probably a similar story in the UK.
In order to tailor GEO Quarterly to the needs of themembership as a whole, we really do need to know
•
•
•
•
•

What type of satellite data you are receiving
Which types of article you enjoy most in GEO Quarterly
The types of topics you wish to see in GEO Quarterly
What improvements you would like to see within GEO
Comments you have concerning GEO, the Quarterly or the
GEO website• How can we make our hobby more accessible to newcomers?
Please type the following URL into your web browser andspend just a few minutes completing our survey form

http://www.geo-web.org.uk/survey08.html
Note that, as this is a survey for magazine readers only,
there is no link to the survey form from our website’s home
page. And of course, any reader who wishes to make a more
extensive reply/comment, is welcome to e-mail the editor, as
Laurence has already done.

www.geo-web.org.uk

3

GEO Quarterly No 18

Group for Earth Observation

June 2008

Les Hamilton

Although the response to the GEO
Survey has so far been totally
underwhelming, there was one tellingcomment from Peter Bartlett that reallycaught my eye:
“In the March 2008 edition I havenoticed the majority of the satellite
images you use are professional rather
than those captured by members. I
assume this to be because these images
cover the topic in question; or is it you
are not receiving members images.”Peter has a point, and is correct on
both counts.
Images covering a Topic
Despite having a membership in excess
of 500, the vast majority of GEO
members contribute absolutely nothing
to the Quarterly. The outcome is thatan inordinate proportion of the articles
that you read in the pages of thispublication are penned by myself: andhere’s the rub—I do not possess a
EUMETCast system; therefore I have no
direct access to the wealth of MSG,NOAA and Metop-A imagery that thisprovides. My ‘live’ satellite activities are
confined to APT. When I write a piece
for the Quarterly, I always try toillustrate it with the best possible
images—which means MODIS images
from NASA and HRPT images from the
NOAA CLASS Archive. There is the odd
exception, such as Eric Dean’s image
that was used in the December ‘Aral
Sea’ article, but as the Aral is out ofrange of my APT system, most of theimages were sourced elsewhere.
Images submitted by Readers
One of the greatest disappointments I
have experienced throughout GEO’s
existence has been the apparent
unwillingness of the readership toshare their images through the pagesof the Quarterly.
The number of readers who do makean effort to send in images from time
to time can be counted on the fingers
of one hand! You can check this byreference to the image credits that
regularly appear in the Quarterly.
GEO has hundreds of members who
download—probably—terabytes (i.e.
virtual bucketloads) of images from
Meteosat, the NOAAs and Metop4

annually, via EUMETCast. It reallywould be uplifting to receive images ofinteresting areas and cloud phenomena
from you.
Guidelines for Images
Anticipating a minor flood of images for
the September issue of GEO Quarterly,
here are a few simple guidelines as towhat we require.
‘Dont’s• Don’t send in full-disc Earth MSG
images or extended (15 minute or
greater) strips from NOAA-18 orMetop. If these are reproduced in
the Quarterly, they will look no
more impressive than APT images.
• Don’t send images defaced withtext, brightly coloured country
outlines or latitude/longitude
gridding. Satellites do not image
these.
• Don’t process your images ingarish bright green tones thatmake them resemble maps from aschool atlas.
‘Do’s
In the 21st century we need to takeadvantage of the superb 1-kilometre
imagery available from the currently
operating Earth observation satellites.
• Be selective. Look for small regionsthat show interesting features,
either of land or cloud, whenviewed at the full 1-km resolution
available.
• Select high-resolution segmentsthat illustrate a region of theplanet with an interesting story
behind it: and add a few lines ofdescriptive text for our readers.
• Send images either inmonochrome, or processed withcolour that look as nearly natural
as possible
Note: astronaut photographs from orbit
clearly show that land features on
Earth are generally brown, not green.
Exceptions
There are, of course, occasions where
overlays of various kinds areappropriate, as on page 8, where an
article deals with an analytical aspectof satellite imagery. But on stand-alone
images, please consider them taboo.

www.geo-web.org.uk

So come on! Any reader could findtheir images displayed in GEO
Quarterly—even on the front cover. All
it requires is a little effort and asharing mentality.
Finally
Just days after compiling this page, I
received an email from David Donnelly,offering to send GEO Quarterly images
from his new location in Australia.
This is what we need more of! Part ofDavid’s e-mail, and the informative text
he sent with the image, appear below.

Australia in APTDavid Donnelly
I am a keen reader of GEO Quarterly
and have been a subscriber since you
first began publication. I have recently
moved from New Zealand to Alice
Springs in central Australia and now
have my APT system working here.
I have been receiving some impressive
images at this location and waswondering if you would be interested inany southern hemisphere images that I
have recently received? Thanks for aninteresting magazine.
_____________The APT image opposite was received
during a NOAA 18 pass on April 20
this year from my home in Alice
Springs. It was received on a homebuilt RX-2 receiver using a homebrew
QFH aerial then processed using
WXSat software.
Timor is clearly visible in the top left
corner of the image. Papua-New
Guinea is the Island obscured by cloudat the top right.
The lake, partially covered by cloud at
the upper left of the continent, is Lake
Argyle. Whilst it appears relatively
insignificant this lake is the largest
man-made lake in Australia and covers
an average area of 1000 km2,
equivalent to 18 times the size of
Sydney harbour.This lake was createdby a dam on the Ord river and has
supplied hydro-electricity andirrigation water to the region since theearly 1970s.

GEO Quarterly No 18

Group for Earth Observation

June 2008

Laurence Holderness - GW0CCO

Following completion of GEO’s on-line
survey, I thought that certain matters could
be usefully expanded upon, hence thiswrite-up. My thoughts are intended as
constructive criticism on GEO and theweather satellite scene as a whole.
Both my wife and I enjoy reading GEO
Quarterly and the various articles therein,and consider it to be an excellent
magazine. Pictures and articles are
excellent. However, since the launching of
the MSG series of satellites, we both feelthat the content has now become much
more technical. Also, many articles have afair amount of computer programming inthem. This I am sure is putting people off
joining the group. Let me try to explain in
my own way.
I understand that satellites in the MSG
series are much more technically advanced
units, and as such, more sophisticatedequipment and software are required toview the downloaded data. However, I am
sure that many of ‘older school’ of weather
satellite enthusiasts cannot understand it
all, especially those in some of the lessdeveloped countries.
With the early VHF APT satellites it waseasy to get started for a small outlay, andone had the excitement of receiving
pictures up to four times per day. A very
low specification computer was suitable forthe job, producing good images, while thesoftware was simple to use. A receiver
could even be built from a kit and aerials
could be home-made.
Now we have gone to the other extreme
whereby two PCs are recommended, bothwith high spec’s. The receiver is normally acard inserted into the PC, while the aerial
system consists of a dish, amplifiers and
LNBs. Then there is the need to obtainlicenses, etc. On top of this there appears
to be a great deal of initial setting-up, withlots of various software packages required
to obtain the finished pictures.
From various articles in GEO Quarterly,
there also appears that a lot ofprogramming is required to make things
work as required. There also appears to be
far too much data to manipulate just to
obtain an image from the newer current
systems. This necessitates a large storage
area and also file management systems
etc, which many of use do not want to haveto deal with.

6

OK, I know that you can now receive
pictures all day long, but a lot of thepleasure was the reception of pictures frompolar orbiting satellites actually passing
overhead a number of times each day. With
all day reception this anticipation of arrival
no longer exists!
Whether this is all necessary, I cannot say;but I am sure that it puts lots of people off
even trying. While I am very good with myhands and at using a range of computer
programs, I find that programming leaves
me dead. As such I am not interested in it. I
was never able to get into a position tolearn programming, possibly because I was
too old when I first started using computers.
No doubt many others were/are in a similar
position and feel the same way as I do.
What we want is a simple system thatwill work without a lot of fuss.
I am sure that many of the original
members were happy with the basic APT
reception and now find that that they cannot
afford the equipment required for thecurrent systems. Neither do they have theexpertise or time that appears to benecessary to get the final picture. Also
many are younger persons who have family
responsibilities that must come first, andcannot spare the time to learn tomanipulate the various intricate software
programs needed to get that final picture.
I feel that those who do are really dedicatedto the hobby, and may have a lot ofprogramming experience, possibly from anearly age, through their employment,
making it all relatively easy for them.
As in many hobbies, there are those whowant everything to be just perfect, andwhile we admire them for that dedication,
we cannot all each that level. Unfortunately,
there does not appear to be any one locally(in Pembrokeshire) with up-to-dateknowledge of the current systems. While
David Taylor and others are very happy toanswer people’s questions, this cannot takethe place of hands on experience. One ofthe problems of living in the far West ofWales.
Many, I am sure, just want a simple system
similar to those used for APT, and are quite
happy to just receive pictures every few
hours or so with a minimum of self activity.
Good basic instructions to set up such asystem, using just one PC and theminimum of software etc. would be much

www.geo-web.org.uk

appreciated—and might well bring fresh
members into the GEO fold.
I did think that MetOp would be the answer,using a fixed QFH or turnstile antenna
receive VHF with LRIT, especially when thecurrent NOAAs close down. However, I see
from your web site, that this function of
MetOp has died and will not be available
until possibly 2012. Oh well—that’ssatellites for you!
So what now? What we want is something
new, which is inexpensive to purchase andwith easy-to-use software, as an alternative
to the MSG satellites. However, theproblem is this: ‘Is there anything in thepipeline to fill this gap?’ If there is then you
may well have an increase in GEO
membership, especially if the content wereto cater for this type of operation. At the
moment APT seems to be virtually ignored
and on it’s way out.
I fear that if there are only the MSG type ofsatellites, then membership will drop,
especially as older members pass on, as
there will not be the younger members to fill
their places.
Conclusion
Sorry if I have seemed to have rattled on abit, but these are my thoughts and also
those of a few friends who, while interested
in APT, are not prepared to go the whole
way with the MSG systems.
It is also a fact that many other clubs andconcerns, have similar problems. Oldermembers appear to carry all the burden of
running the club with very few younger
members. Family ties and money often
dictate when and if someone will join aclub; and of course, a club with no younger
members has no one to guarantee
continuity into the future. I hope that thiswill not be the case with GEO, so what wewant is some way to encourage youngsters
to join.
Editor’s Comments
Interestingly, and probably surprisingly tothe large band of dedicated MSGEUMETCast enthusiasts within GEO, I tend
to share many of Laurence Holderness’
concerns about the way weather satellite
imaging is currently going.
I am interested in weather satellite imagery,but not in 24/7 reception or creating
animations of MSG imagery around theclock. I consider myself to be highlyJune 2008

Group for Earth Observation

computer literate; I write computer programs inseveral languages. But at no time have I evenvaguely considered setting up an MSG system of
my own. Having read in the various Internet
forums of the problems so many members haveexperienced setting up their MSG systems,
particularly with the software, I am just notinterested in the hassle. I have far better things to
do than spend even more of my life wrestling withproblems on my PC and downloading a torrent ofsatellite imagery! What I need to whet myenthusiasm would be a software package that
simply ‘runs out of the box’.
If a seasoned computer user like myself
feel this way, just consider how acomplete newcomer to the hobby feels
when confronted with the contorted andinvolved procedures required to equip
onself for EUMETCast reception: thehardware, software, licensing etc.
I neither want nor require images every
15 minutes. I’ve seen animations—and they areindeed captivating: but I don’t need them. As
Laurence states, individual images several hours
apart are sufficient for many people. And ofcourse, EUMETSAT does provide the free‘essential data’ from MSG every six hours, forwhich no license, nor a hardware key for thecomputer, are required.
Is a simplified, entry-level means ofgetting started with MSG-EUMETCastrequired, one that anyone with a PC canachieve without having to download
gigabytes of files per day; one that simply
deposits a few desired images in a folder
on the hard drive without any userintervention (other than running thesoftware).
The Challenge
So here is my challenge.
• Is it possible to produce a piece of softwarethat will, exclusively, receive and process
this 6-hourly MSG data, leaving only the jpeg
images on the host computer?
• Such software should accept and process
only a restricted set of MSG channels, say
one visible and two infrared—just sufficientfor creating simple colour composite imagery
as currently with the NOAA satellites.
• The software should have a minimal set ofoperations, perhaps restricted to selection of
HRIT or LRIT, and which of the threeallowed channels is required.
• It should be possible to run the software at,say, 11.45, just leave it to collect the desired
images (provided the appropriate dishantenna, LNB and DVB receiver card are
installed) and know that you can switch it off
again once the images are ‘in the bag’.
I have little doubt that such an innovation would
attract newcomers to our hobby as never before.
And of course, once hooked by the images,
doubtless a goodly proportion would, in time,
aspire to the full package.
Readers’ Views
What do GEO Readers think? Please add to thedebate by emailing your thoughts and comments
to the editor at
geoeditor@geo-web.org.uk

Call for Papers
NOAA’s 2008 Satellite Direct
Readout Conference, December 812, 2008, Miami, Florida
The 2008 Satellite Direct Readout
Conference is the 8th Conference
organised and supported by NOAA
to provide information regarding thedirect readout from meteorologicaland environmental satellites andprepare users for upcomingchanges to both satellite series. The
goal and expectation is for strong
international collaboration. Past
conferences have attracted
audiences from 30 to 40 countries.
The conference will consist of
speaker presentations, poster
sessions, exhibitors, and many
opportunities for user feedback.

GEO Quarterly No 18

conference on both current andfuture geostationary and polarsatellites. This includes topics
pertaining to instruments, products
and applications. Of special interest
are posters describing examples ofthe link between research andoperations (or between operations
and research).
Please send your abstracts
electronically via email to
nesdis.dro.conference@noaa.gov

http://directreadout.noaa.gov/miami08/

Please indicate your preference foran oral presentation or a poster.
NOAA conference personnel will
choose the format most suitable toshowcase your work. Posters will begiven maximum exposure, with
ample time for presenter andaudience interaction. Abstracts
must be no more than one page inlength, in 12 point Times New
Roman font.

Abstracts and corresponding
posters are solicited for thisDeadline for abstracts is July 1,
2008.

More information can be found at
the conference website at:Fred van den Bosch
Since the beginning of 2008 I have
had a new ‘toy’: an Apple iMac G5.
Primarily for image processing, I
have also tried it for polar satellite
reception. WxToImg [1], the program
I use, also has a Mac version, so I
played a bit with it. The present
version (2.8.12) has a couple ofadvantages. For me, the mostimportant is that you can choose
one of the six templates for easily
generating a web-page and thenupload it to your website [2], all fully
automatically.
One of the problems I noticed waswith the Mac soundcard. You can
only switch from the default‘Microphone’ to ‘Line-In’ by using
the system preferences.
The only hint I got after posts onsome Mac-forums was to use
Automator, a program to automate
tasks, but it was not really user-

www.geo-web.org.uk

friendly—so I decided to make up
something in AppleScript, as usual,not bothered by any knowledge ofit. After a lot of Googling and cutand-pasting I now have somethingthat works. You can download itfrom my website [3].
Any questions you wish to ask
about it can be posted on myforum [4].
References
1 WxtoImg
http://www.wxtoimg.com/
2 Fred van den Bosch,
http://www.fredvandenbosch.nl/
satellites_polar.html
and follow the links to ‘Europa’ and‘Enhancements’.
3 Fred van den Bosch,
http://www.fredvandenbosch.nl/
downloads_General_files.html
4 http://tech.groups.yahoo.com/
group/POVIM-Software/

7

GEO Quarterly No 18

Group for Earth Observation

June 2008

Terence Smith

A number of minor points have
cropped up whilst I have been fiddlingwith programs since the New Year.
1 If you have two or more animation
files in the same directory, fordisplay in Irfanview, then (ifconfigured for this) it is possible
to switch between them using theleft/right cursor keys; otherwise,using these will advance or backup the frames.
2 Should you have problems with
I-view locking up when set to loop
an animation, or failing to update
every 15 minutes as scheduled,then one can reset the schedulethat opens I-view to an intervalslightly longer than the time taken
for your animation to run
through, e.g., 1 or 2 minutes. The
program should then update andremain looping more reliably.

Figure 1 - A frame from a GOES-12 overlay animation created in GSS

It may be that high specification
computers and fast networks will
not suffer this problem; but if
yours does, then the above might
be a useful work-around.
3 With Windows XP, the Task Tab
window, opened when clicking‘Properties’ for a given task in the
Windows Task Scheduler, shows
the check box to enable theschedule, and a further check box
immediately above which, whenticked, makes the schedule ‘Run
only when logged on’. Whenenabled, this obviates therequirement for password entry
when setting up the task. The
schedule will then run withoutthat requirement (I believe fromlimited testing).
This check box is NOT available in
Windows 2000, but is present
with Vista, although the latter
O.S.’s scheduler is only available
to the administrator’s account.
Vista’s Task Scheduler has beensomewhat hidden away and its“front” much altered; it is now to
be found under Administrative
Tools within the Control Panel.
Finally, David Taylor has kindly
modified a test version of GSS topermit the animation of Multi-sensor

8

Figure 2 - A frame from an MPE overlay animation created with GSS

Precipitation Estimate (MPE) grib files,
making it now possible to create an
overlaid animation of that imagery
without recourse to saving andrenaming the Grib files as Jpeg—asshown on my web page. This may
appeal only to quirky characters suchas yours truly, but you never know.

www.geo-web.org.uk

Figure 1 shows an overlain image of
GOES-12 IR while figure 2 is an
example of an MPE overlay. Both these
may be viewed as full animations on
my website at
http://rifleman.org.uk/mslp.htm

June 2008

Group for Earth Observation

GEO Quarterly No 18

Clive Finnis
Credit crunch, sub-prime, Northern
Rock—what a turbulent world there’s
been in the financial markets lately!
Luckily, absolutely nothing to do withweather satellites, I hear you say. We
can all be engrossed in the fantastic
images we receive, secure in theknowledge that all these crises in theworld stock markets do not affect ourhobby.

prices, in particular the popular R2FX
and R2ZX APT receivers that we sourcefrom Germany. We have also been
faced with increases in UK postal rates
and smaller price rises in APTantennas and the EUMETCast
equipment—LNBs, dishes and Sat
meters—although fortunately thesehave been more modest than the euro
exchange rate problem.

Sadly, wrong!

As recently publicised on the GEOSubscribers group, we are
implementing these price changes from
the May 1, so they will already be inplace by the time you read thisQuarterly (please see the Shop page,
opposite). We always endeavour toprovide the keenest prices to members
and if we see any opportunities toreduce prices in the future we willcertainly do so.

The GEO Shop buys items from all over
the world and has to make purchases
using euros or US dollars. Whereas thelatter has stayed relatively constant to
the UK pound, the euro has moved
dramatically over the last few months,
from an exchange rate of around 1.50:1
to 1.25:1 euros to the pound. Thismeans that everything we buy in euros
is now approximately 20% more
expensive. With the narrow ‘profit’
margins that we work to in the ‘Shop’,
we are now on the point of selling someitems at a loss. This is not somethingthat is sensible in any business, andwith GEO’s fragile finances we musttake some action to counter this.
Thus we have, unfortunately, been
forced to the decision to increase some

The DVBWorld DVB-S USB-2 Box
Now for some great news for the evergrowing number of EUMETCast
enthusiasts. No longer do you need toopen up your PC and risk damaging it
or invalidating its guarantee if you
want to receive the newer Metop data.
We have imported, direct from the Far
East manufacturer, a new DVB-S box
with a USB 2.0 hi-speed interface for

EUMETCast reception—and the evenbetter news is that these are at a
terrific price! This replaces the older
USB 1.0 box which we used to sell forabout twice the price. This new box canhandle all the image data which
EUMETCast sends, including both thegeostationary and polar orbiter data,
both from the regional NOAA-17 and
NOAA-18 coverage and the world-wide
Metop coverage—all at a stunning 1km
resolution. If you are suffering missing
segments with your existing setup, thisbox could be worthwhile upgrade.
The current EUMETCast receiver is the
SkyStar II PCI card which sells (tomembers in the UK) for £59.50. But, by
buying direct from the Far East inbulk, we are offering the new DVB-S
USB2102 USB2.0 receiver for just£55.00. Of course it’s just plug-andplay with no need to open up your PC,
and it’s ideal for use on your portable
PC too. With very similar internals as
the Dexatek I-Tek Sphere DVB-S box
which David Taylor described in thelast GEO Quarterly.
The DVBWorld DVB-S USB2102 is instock in the GEO Shop now. Be sure toorder yours without delay.

David Taylor
Readers may be interested to learn of the new format MTSAT-1R
data which started hourly distribution over EUMETCast on March 4.
It is slightly higher resolution than before, 2752 pixels square insteadof 2288 pixels square.
The visible channel is now being sent with a linear transfer
characteristic, rather than the former near square-root law, providing
better potential cloud detail. EUMETSAT have also added a mid-IR
channel to the EUMETCast stream (illustration on right).
For those who do not have EUMETCast, FY-2C, FY-2C andMTSAT-1R data are all available over the Internet in HDF files(which can be quite large, 200-300 MB) from the China Satellite
Data Service Center (CSDSC). There is a beta update to
GeoSatSignal to handle this data (registration is required).
http://satellite.cma.gov.cn/eng/index.do

September’s GEO Quarterly will feature an in-depth article on thegeostationary imagery available from CSDSC [editor.]

www.geo-web.org.uk

9

June 2008

Group for Earth Observation

GEO Quarterly No 18

Les Hamilton
The four years since GEO Quarterly
first started dropping through readers’letter-boxes have been witness toperhaps the greatest-ever advances inweather satellite imagery. During thisperiod, the development of the
EUMETCast DVB dissemination service
has brought end-users a rich variety of
one-kilometre resolution imagery:geostationary images from Meteosats-8
and -9, polar AVHRR images from theAmerican NOAA satellites plus full
Earth AVHRR images fromEUMETSAT’s own Metop-A satellite. All
these arrive direct from the Hot Bird-6
relay satellite into users’ computerswith minimum effort. But isn’t it all
becoming ever so mundane: the samematerial day after day after day ...

these carry MODIS, the Moderate
Imaging Spectro-Radiometer, which
images the Earth at ground resolutionof up to 250 metres. Between them,
Terra and Aqua provide some 300 true
colour images of Earth every day. The
image of Scotland was acquired by
Terra’s MODIS on February 19 thisyear, during that memorable spell ofhigh pressure that brought crystalclear skies by day and sharp frosts
overnight.

There is an alternative, offering fourtimes the ground resolution. Just lookat the colour image of Scotland on theprevious page. It’s absolutely stunning:
yet the limitations of the A4 page meanthat what you see here is still only
displayed at 33% of its full resolution.
This is a 250 metre/pixel, true-color
MODIS image from NASA’s Terra EOS
satellite—and hundreds of such images
are available, free of charge, almost
every day of the year, to anyone withan Internet connection!

The MODIS instrument provides highradiometric sensitivity in 36 spectral
bands spanning 400 to 1400 nanometres (nm) from the visible andinfrared regions of the spectrum.
Band 1 (520-670 nm) and band-2(841-876 nm) are imaged at a nominal
resolution of 250 m at nadir: theirprimary use is the delineation ofland/cloud boundaries. Additionally,
five of the remaining bands offer 500 m
resolution while the remainder resolve
at 1 km. The satellites orbit at 705 km
to achieve a 2330 km swath andprovide global coverage every one totwo days.
The first MODIS Flight Instrument was
launched aboard the Terra spacecrafton December 18, 1999 and the second
followed on Aqua on May 4, 2002.
Obtaining MODIS Images
Both Terra and Aqua possess state-ofthe-art direct broadcast facilities but
these are out of reach of the amateur.
Data from MODIS is broadcast
continuously at 8.2125 GHz in the Xband. There is no receiving equipment
for the amateur, who would also
require to find space for an enormous
steerable dish antenna as well as ameans of handling over 150 gigabytes
of data per orbit!

NASA’s Earth Observation System
Although the public consciousness
primarily associates NASA with Space
Exploration, the Space Shuttle and theInternational Space Station, theadministration has been studying ourhome planet ever since its inception in1958.
In 1991 NASA launched its Earth
Science Enterprise, a comprehensive
program to study the Earth as anenvironmental system, with specificreference to observations of theatmosphere, oceans, land, snow andice, and how these interact with one
another to influence climate andweather. Key to this enterprise is aseries of three Earth-observing
satellites, Terra, Aqua and Aura, which
between them carry instruments thatimage the planet in a wide spectrum of
wavelengths [1,2,3,4]. The first two of

A section from this image isreproduced below at full resolution toillustrate just how much detail can be
resolved.

So where do these spectacular images
come from? Just direct your Internet
Browser to the MODIS Rapid Response
System website at
http://rapidfire.sci.gsfc.nasa.gov/

Figure 1
The image segment above is reproduced at thefull 250 metre resolution available from MODIS
imagery. The scene was taken from the image on
the preceding page and shows part of the island ofSkye, with the islands of Rum and Eigg to its
south and the Applecross peninsula to its north. To
appreciate the scale, Rum, at lower left, measures
just 13 kilometres from west to east.

www.geo-web.org.uk

and click ‘Real-Time’ on the banner at
the top of the page. This connects you
with the ‘Near-Real-Time Level-2
Browse’ page. Be patient as it may takea few seconds to load, specially in theevenings, when upward of 300
thumbnail images need time to load.
Part of this page appears at the top of
page 12, and illustrates the layout. At
top left are two clickable ground-track
maps, one each for Terra and Aqua, tohelp you to quickly identify when each11

GEO Quarterly No 18

Group for Earth Observation

satellite passes over an area of interest. Beneath appear up
to 150 thumbnail images for each satellite: clicking a
thumbnail displays a 2-km resolution version of the image
while to the right of each thumbnail is a list of clickablelinks for additional resolutions up to the maximum of 250
m/pixel. The 250 m images are delivered in JPEG format
and average around 8 MB in size. Images are generally
provided at 5 minute intervals along the satellites’ orbits
though there are gaps from time to time. But if the region
you require has not been imaged from Terra, it will generally
be available from Aqua.

June 2008

combined. Each point on the Earth's surface appears in two
adjacent swaths, a phenomenon sometimes referred to as
the ‘bow-tie’ effect.
Removing Irregularities from MODIS Images
To produce MODIS images that are as free from blemishes
as possible it is necessary to
1 smooth out the ‘bow-tie’ artifacts, and2 correct for geometric perspective.
Both operations can be achieved through software. The
smoothing is accomplished using a program called
SmoothMODIS which I have developed during the past year;
geometric correction is achieved via the latest version ofDavid Taylor’s CorrectGeometry software.
A segment from a 250 m/pixel MODIS image displaying partof the coastline of Australia in the vicinity of Adelaide
demonstrates how the software works. Figure 3 comes fromnear the right-hand edge of the original MODIS image.
Though only reproduced at 25% of its original size,
unwanted artifacts are evident aplenty, jagged andduplicated cloud and land boundaries in particular.
Following treatment with SmoothMODIS (figure 4), virtually
all trace of this problem has disappeared though a glance at
an atlas will immediately reveal a gross distortion of theoverall scene. In particular, Kangaroo Island, which is inreality more than twice as wide as it is ‘high’, appears
almost circular! Passing the smoothed image throughCorrectGeometry resulted in figure 5, where the features now
resemble reality.
SmoothMODIS
SmoothModis is available as a setup file fromhttp://myweb.tiscali.co.uk/wxsatellite/software.htm

Figure 2 - Part of the Near-Real-Time Level-2 MODIS Browse page

Distortions in MODIS Images
Although the MODIS Rapid Response Team regularly
displays a geometrically rectified ‘Image of the Day’, the nearreal-time images that you download clearly suffer bycomparison. These images are displayed as scanned by
MODIS, without correction for geometric distortion (a featurethat will be understood by readers familiar with NOAAAVHRR imagery). In addition, they also exhibit intrusive
banding towards the margins, where adjacent strips in theimage overlap and display duplicated data.
MODIS builds up its images as a series of narrow strips,
known as swaths, 2300 kilometres in longitude by 10 km in
latitude: each image is formed by splicing many such
swaths together. Immediately beneath a satellite theseswaths abut together perfectly but towards the ends of eachswath the fit deteriorates. This is the result of the same trickof perspective that you would observe when standing on a
bridge over a railway track: the impression that the rails are
becoming closer together with distance (although their
spacing, of course, actually remains constant).
The same is true of each MODIS swath, where the required
ground details are ‘pinched together’ at the extremities by
the perspective effect. Consequently, unwanted additional
details from the adjacent swaths become included and theimage shows ‘double-vision’ artifacts when the swaths are

12

The program should be completely intuitive. Just load a
MODIS image, select <Image → Process> from the menu bar,and observe for about 10 seconds as the image smooths infront of your very eyes. By default, SmoothMODIS saves
smoothed images in BMP format, necessary if they are to beprocessed further in CorrectGeometry. However, if the regionof interest comes from the central part of the image, andcorrection is not considered necessary, there is an option tosave in JPEG format. SmoothMODIS only processes 250 m
and 500 m MODIS images, most of which will smoothcorrectly by default. For dealing with the occasional ‘rogue’
MODIS image, a Help file guides you through additional
program features.
CorrectGeometry
Some years ago, David Taylor produced CorrectGeometry torectify geometric distortions in NOAA HRPT images. He has
now upgraded this software to correct MODIS images also.
You can download CorrectGeometry by visiting
http://www.satsignal/eu

then following the link to HRPT Reader under the ‘Satellite
Tools’ section. You will find a link to download
CorrectGeometry at the foot of this page.
Note: You must use SmoothMODIS before using
CorrectGeometry.
Acknowledgement
All images accompanying this article courtesy of MODIS
Rapid Response Project at NASA/GSFC.
References
1
2
3
4

Terra - http://terra.nasa.gov/About/Aqua - http://aqua.nasa.gov/
Aura - http://aura.gsfc.nasa.gov/
EOS - http://eospso.gsfc.nasa.gov/

www.geo-web.org.uk

June 2008

Group for Earth Observation

Figure 3 - Section from an original, uncorrected near real-time MODIS image

GEO Quarterly No 18

Figure 4 - The same MODIS image after use of the SmoothMODIS software

Figure 5 - The same smoothed image following geometric correction by David Taylor’s CorrectGeometry program

www.geo-web.org.uk

13

14

June 2008

General Report by Francis BellGEO was invited by the organisers of the2008 UK Space Conference to attend andprovide an exhibition stand. This we did,with Francis Bell and John Tellick providing
a stand demonstrating live satellite
reception on all three days. Live MSG
reception was displayed on two separate
systems and in addition we displayed
recorded APT and HRPT on two further
systems. In addition we displayed boards
showing examples of GEO’s activities andprints of weather satellite images.
We are grateful to EUMETSAT, who sent
us many technical leaflets and high quality
poster sized images taken by theirsatellites. All this, together with GEO’s own
material, was available to the conferencedelegates and visitors and by the end of
the conference, little was left!

Group for Earth Observationand the Future’ but must admit that I cameaway rather disheartened over what I had
heard both on ‘Education’ and ‘The Future’.
Ask anyone in the street what they think
about the UK Space Industry and theanswer you generally get is: ‘What spaceindustry?’
I grew up with Sputnik, the ‘space race’ andMoon landings at a time when Britain wasbuilding and launching its own rockets: witha whole industry structure of experts andcapability. Those days have long gone, andyet, Britain is currently a world leader inseveral aspects of space technology, a factthat is just not promoted or celebrated tothe public, unlike the situation in Franceand Germany. Many delegates seemedunhappy with this.

Overall, it was certainly interesting to meetsome of those people who both influenceand enact UK space activities.
Lecture Report by John Tellick
This Conference allowed GEO the
opportunity to rub shoulders with bothprofessionals in the space field andeducationists. This allows us to keep up todate and promote the educational value ofour hobby. I attended several of thelectures and discussions on ‘Space, Policy

Space is an expensive business and one
which a single country cannot go alone.
With its export control restriction policy(over technology), it appears that it’s
getting more and more difficult for the US
to co-operate internationally on space
projects.

ESA astronaut Hans Schlegel works on the
Columbus lab during the STS-122 mission
Image: NASA

Considering the delegate list and theorganisations present, the conference
certainly had a high profile. Among those inattendance were Space Science Leicester
University, Surrey Satellite Technology Ltd,EDAS Astrium, British National Space
Centre, Open University, UKSEDS,
European Space Agency, Space Education
Council. Most of these organisations visitedthe GEO stand during the three days.
As well as dealing with national andinternational space policy, the conference
had a distinct educational dimension withschool groups attending on different days.
There was a competition for rocket
launching—unfortunately not fully tested on
the day because of poor weather. There
was also a competition for schools todesign a very small satellite, perhaps
earning the opportunity to have the winning
design professionally built. Several of theseschool groups visited the GEO stand andwere given a brief presentation about ouractivities and the scope for home receptionof weather satellites. GEO also attracted
the attention of the media and we spentsome time talking to and being recorded bya television team.

GEO Quarterly No 18

There was concern over the militarisationof space as well as manned space
activities beyond the ISS. There was also a
big question mark over the future of ISS
operations once the Space Shuttle ceases
flying, currently planned for 2010.
With the recent addition of two newlaboratory modules, zero gravity medical
and product research aboard the ISS are
about to expand considerably. But owing to
the delays caused by the two Shuttle
disasters though, the ISS will only be twothirds built by 2010, after which there will
be no ‘space lifting capacity’ available
comparable with the current Shuttles. And,of course, crews have to get there andback!

The International Space Station’s robotic
Canadarm2 moves ESA’s Columbus laboratoryfrom its stowage position in Space Shuttle Atlantis’
payload bay to the starboard side of the Harmony
module.
Image: NASA

Secondly, many delegates thought that notenough money was being spent on
space/science promotion or education. Thisis having a profound effect on the numberof engineers, graduates and scientists
going into the industry—our lead in several
fields could be at risk. Contrast that toChina and India, where vast amounts ofmoney are being poured into space/scienceeducation. The feeling was these twocountries would be the next great ‘spacenations.’

www.geo-web.org.uk

A Shuttle replacement—if it ever
happens—is very many years away; so, toan interested ‘member of the public,’ itlooked to me that there were morequestions than answers regarding thefuture of space in the west.
The Columbus Laboratory
The Columbus laboratory is ESA’s biggest
single contribution to the International
Space Station. Inside Columbus’ 4.5metre diameter cylindrical module are 75
cubic metres of space containing an entire
suite of science laboratories. These are
equipped with flexible research facilities
that offer extensive science capabilities
where Earth-based researchers, together
with the ISS crew, will be able to conduct
thousands of experiments in life sciences,materials science and fluid physics in theweightlessness of orbit.

15

David Lee
I don’t know if GEO Quarterly readers
are already aware of the EUMETSAT
web page ‘Image of the Month’. Visit
http://www.eumetsat.int/

and browse following Home → Image
Gallery →Satellite Images of the Month on
the top-of-page page banner (see above).

This page gives access to a wide rangeof satellite images, and has been
designed to promote EUMETSAT
satellite images, products and services,
as well as being an on-line journal forsatellite imagery and a self-training
tool.

Descriptive text by Jochen Kerkmann (EUMETSAT)

Each example image carries a
description of a meteorological event
and an interpretation of satellite
images, often with animations. I
thought readers could find theeducational aspect of these pages
useful to their hobby. The particular
example illustrated on this page relatesa satellite image with photographs
taken from the ground.

To view the original image, browse to
the ‘Satellite Images of the Month’
page, click the link to enter the image
gallery, and browse to the thumbnail
for ‘07 September 2007’.
Jochen Kerkmann, Satellite
Meteorologist Training Officer, is themain organiser of these pages.
(jochen.kerkmann@eumetsat.int)

RGB composite Meteosat-9 image (Vis 3.8, IR 3.9, IR 10.8) from 15:00 UT on September 7, 2007

The images on this page show a high-level
mountain wave cloud seen from bothsatellite (above) and the ground (below,left). As seen from both images, the wave
cloud had a very sharp border on its
northern (inflow) side, while the southernborder was more gradual and thin.
Optically, on its northern side, the cloud
was thick and dark, and formed of small ice
particles, as indicated by the highreflectance (about 10%) in the IR3.9
channel. This high reflectance gives thecloud an orange colour in the RGB
composite when compared with the highlevel ice clouds farther to the east over
Croatia (which were composed from large
ice particles, giving a dark red colour).
The wave cloud remained stationary over a
period from about 09:00 to 16:30 UT (ascan be seen from the time lapse movie
available for download from the web page)then slowly dissolved in the evening hours

16

www.geo-web.org.uk

as can be seen in the photograph below.
(Credit: J. Kerkmann).

Left: View from the ground at 14:30 UT
Above: View from the ground at 17:45 UT

June 2008

Group for Earth Observation

GEO Quarterly No 18

Ed Murashie - emurashie@att.net

The weather satellite field has become an international arena.
The Coordination Group for Meteorological Satellites (CGMS),
the informal international group that started meeting
annually in 1972, has the goal of coordinating the world's
meteorological systems. CGMS members include the satellite
operators, such as NOAA, EUMETSAT, JMA; development
agencies, such as NASA, ESA, CNES; and the World
Meteorological Organisation (WMO). The WMO, founded in
1950, became a special agency to the United Nations in
1951.
‘The vision of WMO is to provide world leadership inexpertise and international cooperation in weather,climate, hydrology and water resources and related
environmental issues and thereby contribute to the safety
and well-being of people throughout the world and to theeconomic benefit of all nations.’
WMO is a member of the CGMS, to ensure that the weather
satellite systems meet the needs of the WMO to fulfil theirgoals. One of CGMS' first projects was the standardisation of
WEFAX; one of its more recent projects is the standardisationof digital transmissions, including LRIT.
CGMS developed the LRIT Global Specification [1] around amodel with multiple layers that describes the processing at
each layer. The model is generally consistent with theConsultative Committee for Space Data System (CCSDS) andthe International Standards Organisation (ISO) Open
Systems Interconnect (OSI) reference model. Using themodel makes LRIT very 'packetised'. At first I thought thisrather complicated what had originally seemed to be an easy
task—especially after working with GVAR data. Once I
understood the model, and how data flows through thedifferent organisations on its way to the satellite, it makes alittle more sense.
Just remember: We are dealing with large picture and data
files, each assigned a priority, splitting them into smaller
segments so they can be multiplexed together then finallybroadcasting them down a single radio channel. All of thishappens through NOAA processing domains located at two
different NOAA locations, Suitland Maryland (domains 1-4)
and Wallops Island, Virginia (domain 5).
I will first describe the 7-layer model from the transmission
point of view for the GOES satellite, followed by an
explanation from the reception point of view. I know thissounds redundant but it makes the complicated processeasier to understand, at least for me. Others may want tojust read one or the other process.
The implementation of the 7-layer model varies from one
satellite system to another because each country seemed tointerpret the CGMS standard differently. Also, the standard
leaves some aspects, like encryption, error checking andcompression methods, up to the satellite operator. NOAA's
interpretation can found on their website [2].

The Transmission Point of View
The Application Layer is the generation of the user data andcan be a picture, environmental data or a text file. The
Presentation Layer converts the data into LRIT files like thetest files on the NOAA website [3]. Earth pictures are split
vertically into five LRIT files, so that if any one file is lost,
the whole image is not. An example of an LRIT file isgos11chnVS01rgnFDseg001res04dat275000630709.lrit
This is a GOES-11 visible channel, full disk image, segment(file) No.1 and N/S resolution of 4 km. It was transmitted on
day 275 of the year at 00:06 UT. The LRIT file structure
consists of a primary header containing the file type, total
length of all headers and the data length. This primaryheader is followed by optional headers containing items likethe file name, image structure, image navigation, timestamp, etc. The picture data follows the final header and is
structured as pixels across and lines down the image. Eachpixel is one byte which can represent any one of 256 shadesof gray.
The Session Layer encrypts and compresses the data. GOES
data is not encrypted but its images are compressed using alossless proprietary Rice compression technique. NOAA has
obtained rights to the decompression algorithm and has
supplied a DLL software library for users. The initialtransmission priority is assigned at the Session Layer.
The Transport Layer assigns 11-bit Application Process
Identifier (APID) numbers, adds a transport header, andthen splits the file into 1-8190 byte TP_SDUs. The APID
number tells the decoding process which application thisdata belongs to. The transport header contains a file counter(to track lost blocks) and a file length field. The TP_SDU
length is equal to the length of one compressed picture line.
TP_SDU then has a 6-byte header added ahead of it and a
16-bit checksum after it to form a CP_PDU data packet. The
6-byte header contains the version, type, APID number,sequence number and packet length. The sequence number
indicates whether the block is the first, continuation or last
block of an LRIT file.
The sole function of the Network Layer is to convert the
APID number into a virtual channel ID (VCID) number. The
final CADU data packet contains only a 6-bit field, whichaccommodates 63 different product types, one being adummy fill type. So LRIT can only simultaneously transmit
62 products, belonging to 62 APIDs.
The Data Link Layer is a busy one. It splits or packs leftover portions of CP_PDU packets into fixed 884-byte
packets. A 16-bit header is added to the packet, forming an
M_PDU packet. The header specifies the starting position ofa new CP_PDU packet in the M_PDU packet. The Data Link
layer then generates the Reed Solomon check characters andadds another header forming the CVCDU packet. This
header contains the version number, the spacecraft ID, the
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Figure 1 - The LRIT Transmission Encoding Process

CVCDU packets are transmitted with a VCID of 63. The
Data Link Layer then exclusive ORs the CVCDU data with apseudo random number (PN) sequence. The randomisation
ensures that there are no long strings of 1's or 0's thatwould cause the receiver demodulator to drift to a DC level.
Finally, the randomised CVCDU packets have a 32-bit sync
pattern of ‘1ACFFC1D’ added to the beginning of the data tohelp in the receiver decoding process.
The Physical Layer performs base to -rate Viterbi error
encoding, adding one extra check bit for each data bit. The
NRZ-L signal then Bi-Phase Shift Keys (BPSK) the 1691 MHz
carrier.
The Application Layer is handled by NOAA domains 1 and 2
and the Presentation Layer is performed in NOAA processing
Domain 3. Domain 4 handles the Session Layer, theTransport Layer, the Network Layer and half of the Data
Link Layer. Domain 5 handles the other half of the Data
Link Layer and the Physical Layer. The users are Domain 6.
The entire LRIT Transmission encoding process is shown
schematically in figure 1.

18

The Reception Point of View
Since the Physical Layer involves the demodulation process
and Viterbi error decoding process, the 293833 symbol per
second data stream is, firstly, BPSK demodulated. Next thedata stream is error decoded using the -rate Viterbi
decoding method. This means that one error correction data
bit is sent for every image data bit. More can be found about
the Viterbi process on the Internet at Wikipedia or the many
published error-correction and detection books. The outputof the Physical Layer is a randomised bit stream. The
Comstream CM701 satellite modem [4], described in the lastarticle, was chosen to implement the Physical Layer because
it performs both BPSK demodulation and Viterbi decoding.
The Data Link Layer is composed of two sublayers; theVirtual Channel Access (VCA) layer and the Virtual Channel
Link Control (VCLC) layer. The input to the VCA layer is therandomised bit-stream from the Physical Layer. The first job
is to look for and extract the 32-bit block sync characters,‘1ACFFC1D’ hex. These sync characters signify the start ofeach 1024-byte CADU block. Next the VCA layer
derandomises the data stream by exclusive OR-ing the
CADU data with the output of a PN generator, forming a

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then the CP_PDU data is the beginningof a new transport file. A file is opened
and the transport header is processed.
The transport header will indicate if
Rice compression is used and if so, thedata is decompressed. The
decompression process is the Session
Layer. The data (minus the transport
header) is saved to the new file. If thesequence flag is ‘0’, then the CP_PDU
data is continuation data for atransport file. The program checks if afile has been opened, decompresses thedata if required and then saves thedata to the open transport file. If thesequence flag is ‘2’, then the CP_PDU
data is the last block of data for atransport file. The program checks if afile has been opened, decompresses thedata if required, saves the data andcloses the transport file. The output of
the Session Layer is a LRIT file.

CVCDU block. The Xilinx board
described in the previous article
implements the data Link Layer up to
this point. From this point forward the
Personal Computer implements theremaining layers. The next step is toperform Reed-Solomon block error
correction using the 128 bytes of ReedSolomon data on the previous 892
bytes. The Viterbi decoding process isrequired, but the Reed-Solomon
decoding process can be skipped if
there is a sufficiently high signal tonoise ratio. My system uses a six footdish and therefore the Reed-Solomon
data is discarded with no perceptible
noise, forming a VCDU block. The
VCDU block of 892 data bytes containa 6-byte header which contains theversion number, the spacecraft ID, thevirtual channel ID (VCID) and theblock counter. If the virtual channel ID
is 63, then the block is just a fillpacket between transmissions, and theentire block can be discarded. If it is
not a fill packet, the 6 header bytes are
discarded forming a 886-byte M_PDU
data packet which is the output of the
VCA sublayer and the input to the
VCLC sublayer.
You may ask what a virtual channel is.
This gets back to the idea of having aflexible data format that can handle
several sources of data: pictures, DCS
data, etc, all at the same time bymultitasking or multiplexing the data
sources together. As data products are
generated and ready to be transmitted,
they are assigned Application Process
Identifier (APID) numbers. The VCDU
header contains 6 bits for a virtualchannel ID (VCID) which is enough for
62 different products and the fill block
designation. When a VCID is not being
used and there is a new APID
available, it is assigned the VCID
number.
Now the process of demuxing the databack into LRIT files begins. VCDU data
is decoded into M_PDU blocks which
are decoded into a CP_PDU block andis equal to one image line. Multiple
CP_PDU blocks form an LRIT file,which is 1/5 of an LRIT image.
The M_PDU header is processed todetermine if there are one or more
M_SDU blocks contained in theremaining M_PDU block. The header
contains a pointer to the beginning of
the next M_SDU block within the
M_PDU block. If the header is 2047
then all of the M_PDU data belongs toa previous M_SDU block. If the header
is 883 or less, then data up to thepointer is saved with the previous
M_SDU block and the data starting at
the pointer is saved in a new M_SDU
block. One or more new M_SDU blocks
may exist in the M_PDU block.
Multiple M_SDUs make up a CP_PDU
block and one CP_PDU block contains

GEO Quarterly No 18

The Presentation Layer is displaying
the LRIT files using my LRITdisplay
program or XRIT2PIC5 written by Rob
Alblas [5].
NOAA provides the source code for an
excellent display program, but I
haven’t been able to find anyone with aBorland Builder compiler to generate ityet (any offers?).

Figure 2 - Overall LRIT capture program

The LRIT Software
The source code and PC executables
for the FPGA, the LRITcapture programand LRITdisplay programs are locatedon my website [6].

one image line. The CP_PDU block is
the output of the Data Link Layer.

Information on the FTDI USB drivers
can be found on their website [7].

The Network Layer determines which
LRIT file the CP_PDU block belongs tosince the data from various data
sources is multiplexed. This is done byusing the VCID identifier as an index
into an array of open files in which the
CP_PDU data is stored.

The FPGA code was developed with the
Xilinx Webpack free compiler that canbe downloaded from the Xilinx
website [8].

The Transport Layer decodes the
CP_PDU header to determine thesequence flag. If the sequence flag is‘3’, then the CP_PDU is one complete
transport file. A transport file is a LRIT
file plus a transport header. A file isopened, the CP_PDU data (minus thetransport file header) is saved and thefile is closed. If the sequence flag is ‘1’,

The LRITcapture application was
written in C++ since the required Ricelibrary was written in C++ and wascompiled using Microsoft Visual
Studio.NET 2003.
The LRITdisplay application was
written in Visual Basic. Visual Basic
was used in this instance due to its
ease in manipulating graphics images.
Compilation was effected using theMicrosoft Visual Basic 2005 Express

Figure 3 - Screenshot showing the various types of files being received out of order due to demuxing

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Figure 4
The CADU block
process routine

Edition that can be downloaded free from theMicrosoft website [9].
I want to emphasise that I am not a programmer.
I am an electronic engineer who programs enoughto test my hardware. I learned C++ to write thiscode! I want to thank Tracy Lenocker, Ed Alcaraz,
Charles Martinez and Jer Dubois for teaching me
the fine art of C++ and Visual Basic programming.
The code works but is no-frills and thus is easier tofollow.
I highly encourage others to use the code in any way
they see fit. Please visit my website and contact me if
you have any questions or suggestions.
Future Articles
Future articles will include the use of the LRIT
hardware to receive the NOAA HRPT and GOESGVAR data streams. Also, the use of a different
satellite modem and a more readily available FPGA
board.
The LRITcapture program was written using thefollowing flowcharts. These flowcharts were used todevelop the LRIT capture program and may help in
the uinderstanding of the decoding process.
References
1 http://www.wmo.ch/pages/prog/sat/documents/CGMS-03_HRIT-LRIT_v2-6.pdf
2 http://noaasis.noaa.gov/
LRIT/system_specs.htm
3 http://noaasis.noaa.gov/LRIT/testing.htm
4 The Comtech CDM-IP 300L modem has
been found to work also.

20

5 http://www.alblas.demon.nl/
wsat/software/soft_msg.html
5 http://www.alblas.demon.nl/
wsat/software/soft_msg.html
6 http://home.att.net/~emurashie/
7 http://www.xilinx.com/
support/download/index.htm

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8 http://www.ftdichip.com/Drivers/D2XX.htm
9 http://www.microsoft.com/express/vb/

The author can be contacted atemurashie@att.net

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GEO Quarterly No 18

Figure 5
The M_PDU block
process routine

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Figure 6
The CP_PDU block
process routine

Postscript
Larry Gouliard KA9GCI and Mike Kimzey have contacted me concerning
this project, and Larry and I are currently working on duplicating the
LRIT system. I asked Larry to review this article, and here’s what he had
to say:“I must say that I learned a lot from my reading of your article. I
found your information much easier to digest than the myriad of
information available on the various NOAA websites. I believe
the information you presented, along with your circuitry, willallow amateur wx satellite users to duplicate your work, which
provides an inexpensive method to receive LRIT. An inexpensive
LRIT system has been sorely lacking in the amateur wx satellite
community, especially for those of us who have been missing
GOES WEFAX.”

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GEO Quarterly No 18

Peter Wakelin
Earth Imaged from Moon Orbit
An image of Earth taken by the high-definition TV camera
on board the Japanese spacecraft Kaguya whilst on its way
to the moon appeared in the December, 2007 issue of GEO
Quarterly. Now, in a rare alignment opportunity, it has
imaged Earth again from its low (100 km) orbit around themoon. The HDTV camera, specially developed for space use
by NHK, the Japan Broadcasting Corporation, captured theimage below, on April 6, when the moon was about
380,000 km from Earth. NHK processed the image for JAXA,
the Japan Aerospace Exploration Agency.

Wilkins Ice Shelf, Antarctica
Image: NASA/GSFC

Larsen-B in 2002, which disappeared in the space of five
weeks. The Prince Gustav Channel, Larsen Inlet, Larsen-A,
Wordie, Muller and the Jones Ice Shelf collapses also
underscore the marked, recent warming in this region of
Antarctica.

Earth imaged from the Moon
Image: © JAXA/NHK

Wilkins Ice Shelf Disintegrates
Satellite imagery from the National Snow and Ice Data
Center at the University of Colorado at Boulder reveals thatthe 13,680 square kilometre Wilkins ice shelf on thesouthwest of the Antarctic Peninsula began to disintegrate
on February 28 when a 41 x 2.5 km iceberg fell away fromthe ice shelf’s southwestern front, triggering a runaway
disintegration of 405 square kilometres of the interior. A
narrow beam of intact ice, just 6 km wide, was protecting
the remaining shelf from further breakup as of March 23.
As ice shelves are floating, their disintegration and melting
does not cause any direct rise in sea level although manysuch shelves hold back glaciers which, if unleashed, would
contribute to the rise in global sea levels.
Several other ice shelves in this region have collapsed in thelast thirty years, the most spectacular of which was

NPP Delayed Again
A contractor’s slow development of a critical new sensor forthe precursor mission for the National Polar-Orbiting
Environmental Satellite System (NPOESS) has further
delayed the launch of the
NPOESS Preparatory Project(NPP). The sensor involved isthe Visible Infrared Imager
Radiometer Suite (VIIRS), a new
high-performance imager for the
next-generation NOAA polarorbiting weather satellites.
It was in May, 1994 that a US
Presidential Decision directed
Artist’s impression of NPP
the US Departments ofImage: NASA
Commerce and Defense toconverge their separate polar-orbiting environmental satellite
programmes into a single entity to serve both military andcivilian needs. The outcome of discussions was thatwww.geo-web.org.uk

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NPOESS and the first spacecraft was expected to beavailable for launch ‘toward the middle to latter half of thenext decade’. As the projected launch date slipped and it
was thought possible that the remaining current generationof polar-orbiters would not last until NPOESS was
operational, the NPOESS Preparatory Project was born withan anticipated launch date of October, 2006. The NASAlaunch schedule now (late April) gives June 2010 as thelaunch date for NPP and the first NPOESS craft is notexpected to be launched before 2013.
Envisat Observes Regionally Elevated CO2 from Manmade Emissions
Scientists at the Institute of Environmental Physics (IUP) at
the University of Bremen in Germany, using data from the
SCIAMACHY instrument on ESA’s environmental satellite,
Envisat, have, for the first time, detected regionally elevatedatmospheric carbon dioxide levels originating from manmade emissions.

June 2008

The two-year extension will include 60 additional orbits ofSaturn and more flybys of its exotic moons. These will
include 26 flybys of Titan, seven of Enceladus and one eachof Dione, Rhea and Helene. The high priority given to
Enceladus stems from earlier findings from Cassini that leadscientists to think that liquid water may lie just beneath thesurface of this tiny moon. Geysers of water-ice have been
observed jetting from the surface of Enceladus and, becauseof the moon’s weak gravity, they feed particles into Saturn’sring system. The largest moon, Titan has many similarities
to Earth and may now be similar to what Earth was likebefore life evolved.
Massive Iceberg Breakup Observed
The huge A53A iceberg broke off the Larsen Ice Shelf, on theeastern side of the Antarctic Peninsula, in April, 2005 andhas now broken up after reaching the warmer waters east of
the island of South Georgia in the South Atlantic Ocean.

Regionally elevated carbon dioxide (CO2) levels
Image: IUP, DLR and ESA

Dr Michael Buchwitz and his colleagues used SCIAMACHY
data from 2003 to 2005 to detect the relatively weakatmospheric CO2 signal arising from man-made emissions
and found a plume of elevated CO2 levels extending fromFrankfurt, Germany to Amsterdam in the Netherlands, as
shown by the darker shades in the diagram.
‘The natural CO2 fluxes between the atmosphere and theEarth’s surface are typically much larger than the CO2
fluxes arising from man-made CO2 emissions, making
the detection of regional anthropogenic CO2 emission
signals quite difficult,’ Dr Buchwitz explained. ‘This does
not mean, however, that the anthropogenic fluxes are ofminor importance. In fact, the opposite is true because
the man-made fluxes are only going in one direction
whereas the natural fluxes operate in both directions,taking up CO2 when plants grow but releasing it again
later when the plants decay. This results in higher
atmospheric CO2 concentrations in the first half of theyear followed by lower CO2 during the second half of theyear with a minimum around August. That we are able
to detect regionally elevated CO2 over Europe shows thehigh quality of the SCIAMACHY CO2 measurements.’
More details on this, and useful weblinks, can be found at:
http://www.esa.int/esaCP/SEMZHVM5NDF_index_1.html

NASA Extends Cassini’s Grand Tour of Saturn
More than 10 years following launch and four years after
entering orbit around the ringed planet, Saturn, the Cassini
spacecraft is in good health and still has sufficient
propellant remaining for several more years of operation.
Due to end in July, 2008, NASA has extended theinternational Cassini-Huygens mission by two years.

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Iceberg A-53A following breakup in the South Atlantic ocean
Image: C-CORE, ESA

A huge north-south fissure through the ‘berg was spotted on
March 1 by C-CORE, the Canadian ice-tracking service,while studying satellite images collected from the Advanced
Synthetic Aperture Radar onboard Envisat. This indicatedthat the ‘berg was likely to split and, just three days later,
the Medium Resolution Imaging Spectrometer (MERIS) on
Envisat captured this image confirming the breakup. Partsof South Georgia are free of cloud and can be seen at thebottom of the image.
SAR-Lupe 4 Launched
Germany’s fourth SAR-Lupe radar satellite was launched bya Russian Kosmos-3M vehicle from the northerncosmodrome at Plesetsk, Russia on March 27 into a sunsynchronous near-circular orbit. Like the three previous
ones launched since December, 2006, this satellite orbits
just below 500 km altitude. The fifth and final SAR-Lupe isscheduled for launch later this year. ‘Lupe’ is the German
word for magnifying lens.
The X-band synthetic aperture radar (SAR) has a 3 m
diameter antenna and is capable of resolving targets tobetter than one metre. The satellites were developed by theGerman aeronautics company OHB-System but the cores of
the SAR sensors were provided by Thales Alenia Space.
Spacecraft control and data retrieval and analysis arecarried out at the ground station at the Zentrum fürNachrichtenwesen der Bundeswehr in Gelsdorf, Germany.

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Alan Sewards
Ten years ago, Alan Sewards compiled a seminal article detailingthe various sources of interference that frequently bedevilled APT
and Wefax weather satellite images. For many years, Alan’s article
appeared on the EUMETSAT website. As ever more hobbyists takeup APT imaging for the first time and queries about interference
appear on weather satellite Internet Forums, Alan has kindly
updated his article for GEO readers.
Introduction
You have splashed out for that 137MHz wxsat receiver, softwareand some sort of aerial, hooked them all together, and waited forthe first pass of one of the NOAA weather satellites. When it
appears, you are very excited at the thought that you have picked
up a remote sensing signal from a spacecraft, in real time, and are
actually seeing the surface of the Earth.
After a while, you will very likely notice that the images you receive
are impaired in one way or another. If you have bought the various
parts of your system from well-known vendors, it is unlikely that
there will be anything wrong with the receiving chain; the cause of
the impairments is most likely to be interference.

Figure 1 - Typical pager interference

Interference can arise from three main sources• transmissions on or near the spacecraft frequency fromterrestrial or space sources,• emissions from your computer system,• power line interference.
This article is aimed at explaining the sources of the various
interference, showing how to recognise them, and suggesting waysof mitigating or eliminating the effects.
Things have moved on since this article first appeared 10 years
ago and I felt that an update would be useful. In some ways the
update is premature, as APT is giving way to new digital formats(HRIT and LRIT), but as there are still weather satellites using the
APT signal format, there will be users who will find the article
useful. LRIT in particular has not made much impression on thereceiving market as few affordable systems have appeared. For
myself, I have embraced the excellent EUMETCast service, whichhas provided me with huge amounts of superb data, with noworries about interference!

Figure 2 - CRT monitor interference

Causes of Interference
PagersInterference from terrestrial transmissions was rare until the late
1990s, when the craze for pagers took off and the countryside
became liberally sprinkled with high power transmitters operating
within a few megahertz of the frequencies used by the NOAA Tirostype satellites for their APT signals. These transmitters haveeffective radiated powers of 10 - 50 watts, and may be located inyour neighbourhood. In my case, there were two transmitterssituated at 500 and 800 metres distance respectively, with ERPs of
30 W and 120 W. Although these transmissions are on lawfully
allotted frequencies and the bandwidth and power are (supposed
to be) strictly controlled, they are close enough in frequency to thesatellite signal for the RF selectivity of the weather satellite (wxsat)
receiver to experience problems. If the pager signal is strong
enough it overloads the RF stages or the mixer of the receiver andbreakthrough of the pager signal on to the satellite frequency towhich the receiver is tuned. Those wxsat APT receivers designed

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before the pager revolution tend not to have adequate RF
selectivity and ability to handle strong interfering signals: more
recent designs are much better in this respect.
Computers
Computers can produce interference in several ways. Most obvious
is the general hash produced by all the fast edges of the clocks
and other waveforms in the computer. This is often very bad in the
shortwave frequency band. Stable signals from the master clocksof the CPU and the bus, and their harmonics, can also be found.
However, for many people these do not seem to cause significant
problems with APT reception, probably because the hash is fairly
well attenuated by the time we get to 137 MHz, and the harmonics
of the clocks do not fall on the frequencies of interest. Others,
however, do experience strong interference, and sometimes resort
to recording the satellite audio on a tape recorder and turning thecomputer off. 14400 bps modems have a strange quirk in that mostof them seem to generate a strong signal on 137.62 MHz, the
NOAA-17 APT frequency, but such modems are rare these days.
The other major culprit is the CRT monitor, which can radiatestrong RF interference over a wide band, modulated at the refreshrate, even though it may be labelled ‘low emission’. In these daysof flat screen LCD monitors, this problem will likely be going away.
Power Lines
Power line interference is often a mystery, as it comes and goes ina seemingly random manner and its source may be quite distant.
In general, it is caused by a poor contact somewhere on an
outdoor overhead power line. The contact may be intentional, suchas two cables spliced together, or unintentional, such as a piece ofwire like a coat hanger hooked over the line. High voltage
insulators can produce corona discharges under certain conditions,such as dirt on them or dampness. The poor contact causes
arcing, which generates the RF spectrum, which is modulated at
50 or 60 Hz depending on which continent you live in. Winds, rain,
fog and snow can all have an effect on power line interference,sometimes increasing it dramatically and at other times reducing it,
depending on the type of faulty connection. One feature of certain
types of power line interference is that it tends to build up slowly
over a period of months or longer as an insulator or joint on a line
degrades. Power line interference on an APT image is very similar
in appearance to the interference caused by a computer monitor.

Figure 4 - Antenna problem

Figure 5 - GOES Co-channel interference

Co-channel Interference from another Satellite
There are two types of co-channel interference, that seen on
GOES WEFAX and Meteosat signals is the result of using a
receiving antenna with too wide a beamwidth or excessively highside-lobes. Such an antenna receives not only the signal from thedesired satellite (say, GOES 10), but also the signal from anothersatellite located at a different longitude. As all GOES and (Ibelieve) Meteosat geostationary weather satellites radiate on 1691
MHz, this results in a beat pattern on the images, often called
herringbone interference. This effect could also occur with the
NOAA TIROS satellites, except that the Spacecraft Control Center
takes care to turn off the transmitter of one of the satellites if theirorbits coincide. Co-channel interference from terrestrial transmitters
is rare, because of frequency allocation regulations. More recently
another source of co-channel interference has appeared, with the
deployment of the Orbcomm satellite constellations. These digital
data communications satellites are also in low-earth orbits (LEO)
but not in the same planes as the polar orbiting NOAA and METOP
satellites. But their frequency allocations are in the 137 MHz bandand the frequencies used are very close, so interference is
occasionally experienced.
Illustrated Interference Examples
Figure1 shows a typical case of pager interference. It ischaracterised by bars of interference lasting tens of seconds, andwithin the bar can be seen blank periods and periods with dottedlines. These correspond to the tones, intervals and data (andsometimes voice) of the pager burst. Like most interference,
pagers have worse effects at low angles of elevation of the satellite
where the signal is weakest, so they are usually seen at the
beginning and end of passes. Because the interference is the26

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Figure 6 - Orbcomm satellite interferenceJune 2008

result of a non-linear process in thereceiver, it is often highly specific to one of
the weather satellite frequencies: in mycase 137.62 MHz is much more affected
than 137.50 MHz.
Figure 2 illustrates the effect of CRT
monitor interference. This shows up as
diagonal bars across the image and, likethe pagers, is worst at the beginning andend of passes. By counting the number ofbars across the image and doubling it (toallow for the fact that the image widthcorresponds to 0.5 seconds), you obtain thefrequency. In the example shown there are
44 bars, which translates into a rate of
88 Hz. The monitor vertical scan rate issupposed to be 85 Hz: near enough!

Group for Earth Observation

signal which was about 40° in azimuth
away from GOES 8. Four-foot dishes also
fall into this category.
Figure 6 (thanks to Alain Nierveze) showsinterference experienced from an Orbcomm
satellite when receiving NOAA-17. The
Orbcomm satellites use 137.56 and137.6625 MHz, very close to the NOAA
frequency of 137.62 MHz, and uses data
frequencies of 57.6 kHz in bursts, one ofwhich can be seen in the upper left handcorner of the image. It is interesting to notethat the interference burst is almost
perfectly synchronised with the NOAA-17
APT scan, giving rise to the straight lines
running down the screen.
Curing the InterferencePower line interference (Figure 3) also
looks just like this, except that each halfcycle of the a.c. generates a bar; so there
will be twice as many bars as the line
frequency.
Modem interference is rather more subtle.
As noted, many 14400 bps modems seemto generate a signal at 137.62 MHz and not
at the other frequencies used by weather
satellites. This signal is fairly stable and cochannel, and it affects the image in two
ways. By interfering with the satellite signal
it tends to prevent receiver lock-up,
delaying acquisition and collection of theimage. During collection, it shows up as afaint herringbone pattern or streaky pattern
all over the image. I have not observed thistype of interference with other types ofmodem: in particular 2400 bps, 33.6 kbps,
and V92.
General computer interference is similar tonoise: it can be heard aurally from thereceiver as noise and tends to raise thereceiver noise floor, delaying signal
synchronisation and shortening the passduration. You can check if you have it bylistening to the audio output of the receiverand turning the computer off.
Problems are sometimes encountered withantennas which appear to be due tointerference but are not. Figure 4 illustrates
this, with a portion of an image which has apager bar but also a noise bar. In this case,the antenna in use was an experimental
one (a quadrifilar) possessing a null in thereception pattern which gave rise to thenoise bar. It also had a more rapid drop in
signal strength at low elevations than isnormal. This type of problem can berecognised by the fact that the signal fades
smoothly into noise and then back out of it.
Figure 5 shows a GOES 8 image exhibiting
co-channel interference from GOES 10.
Although GOES 10 was not operational at
the time the picture was taken, its 1691
MHz transmitter had been turned on towarm the spacecraft during the eclipse
season, with the results shown. My antenna
was a 44 element yagi, which had enoughgain to receive the WEFAX signal, but notenough directivity to exclude the GOES 10

PagersMuch has been written on the problem ofpager interference. It would take up toomuch space to repeat it all here, so I will
give a short summary. As the problem is in
the receiver, and due to overload of thereceiver’s early stages, it helps to reducethe interfering signal if this can be done
without reducing too much of the wanted
satellite signal. For example, antenna
preamplifiers are good for the system noise
factor, but amplify the already very large
pager signal by 30 dB or more. Removing
the preamp can often effect a significant
reduction in interference, if not a cure. You
may then want to replace the co-axial cableconnecting the antenna to the receiver witha low-loss variety such as Belden 9913.
Make sure you select double screened
cable, as this helps avoid pick up of various
types of interference, such as computer
emissions, on the feeder.
If the interference persists after taking thesesteps, the addition of a helical filter before
the receiver may help. In my case, a threestage custom helical filter was built whichgave 1.1 dB of loss to the wanted
frequencies while attenuating the unwanted
pager signals by 57 dB and 26 dB.
(Fortunately, the pagers were on 140.16
and 141.40 MHz.) If your pagers are withina few hundred kHz, as some are in the UK,
the filter will not be able to help you. Allother simple types of filter, such as tuned
stubs, have inadequate Q to discriminate
between the wanted and unwanted signals.
Computer
It is difficult to offer advice with computerinterference, as it is invariably picked up by
the antenna (or feed coax), and is therefore
very sensitive to relative location andorientation. Moving the computer aroundthe room to find a quiet spot is one solution.
If the receiver is connected to the PC via ascreened cable, check that the cable is ofgood quality with well attached connectors.
Looping the cable through ferrite rings canprevent interference being transmitted
along the outer conductor. Checking theconnectors on the co-axial cable from theantenna to the receiver can also pay off, if
there is poor contact to the outer screening.

GEO Quarterly No 18

Some 14400 baud modems can be turned
off by issuing the command ‘ATS24=1’ in aterminal window—this sets the internal
timer to turn the modem off after 1 second.
(This command is meant for use withbattery operated modems but thecommands have been carried through into
desktop modems in some cases). You will
have to repeat the command if the phonerings! If this does not work with yourmodem, removing or replacing it withanother type seems to be the only cure.
The monitor should be kept well away fromthe feed cable between the antenna andthe receiver. Changing the relativeorientation of the monitor, the cable run andreceiver may also do the trick. The monitor
can be turned off during passes if a quiet
location cannot be found. The energysaving mode can be used for this if desired.
I would note here that my old monitor(SVGA, circa 1990) did not produce any
interference, but my newer one (1995, with‘low emission’), does produce a lot, as
Figure 2 shows.
If all else fails, resorting to recording thesignal on a tape recorder for later playback
into the computer is one approach whichenables the computer to be switched off
during satellite passes.
Power Lines
This type of interference, once identified,has to be handled through the owners of
the power lines concerned. At least in thecontinent I lived in (N. America), mostauthorities are aware of the potential for
problems and are sympathetic to doing
something about it provided you candemonstrate to them that it is a power line
problem. To do this you must exclude allother possibilities and, by counting thenumber of bars, get a strong indication thatthe interference is at power line frequency.
If the interference varies with weather, log
the severity and the weather conditions,
keeping copies of the imagery you get ineach case. To the expert from the powercompany, a statement that the interferenceis worse when the wind is blowing, or better
when it is raining, contains much useful
information about the likely cause of the
problem. When I suffered power line
interference the culprit turned out to be
3300 volt insulators on a pole about
500 metres away. The same pole also
carried 11 kV and 33 kV lines, and I had a
275 kV line about 300 metres away. The
expert tracked down the source of the
problem within an hour or so and fixed it
the same day.
Co-channel Interference
These days, this type of interference with
APT signals is almost exclusively a problem
with Orbcomm as the Meteosat and GOES
geostationary satellites have long since
discontinued the dissemination of Wefax.
There is little or nothing that can be done
about co-channel interference as thesatellites are using allotted frequencies andcontinued from page 43 ...

www.geo-web.org.uk

27

GEO Quarterly No 18

Group for Earth Observation

June 2008

Fred van den Bosch

GeneralBelow is described a program that can check a maximum of
15 Yahoo forums for new messages. As soon as a newmessage is posted, an announcement will pop up on yourcomputer screen (figure 1).
BackgroundIn 2003, Arne van Belle [1] wrote of the appearance of a newphenomenon: the Internet mailing list. I, and undoubtedly
many others, registered with one or more forums as a resultof this article. Nowadays there is a wide choice [2] and [3]within our sphere of interest. The great advantage is thatmany people may already have experienced the problems
which you yourself encounter and searching on a forum canfrequently produces a solution. If not, then asking thequestion on a forum nearly always guarantees a direct
response, frequently with the solution.
I am a member of a reasonable number of forums and enjoy
checking for new additions each day and set up a number offavourites in Internet Explorer to access them. But could it
be done more simply, without me having to do anything
myself (my well-known idleness)? Then I recalled that I had
written a piece of coding for my POVIM alert programmethat made a number of checks on Internet sites for thepresence of data. To check for new postings on a forum
would be even easier as only the date and time of the mostrecent mail need be examined. Once this had become clear,
the program was written in no time at all!
However, only the Yahoo forums can be examined in thismanner as they all have, as it happens, the same structure.
On other forums the matter is frequently subdivided inseveral subjects, so would require a separate piece of coding
for each forum

Figure 1 - The POVIM Forums screen

and download POVIM Forums, then unzip it into an
appropriate folder. Run Forums.exe, and after a short pause,a window appears (figure 1) with a number of forums listed
on it. When run the first time, the program shows theforums which I myself have added. A maximum of 15
forums can be inserted.

Buttons• Show all: All forums with new messages are shown (Beware:
the default browser must be open)• Refresh: all forums are again checked and a status bar
indicates the progress. In the case of problems, the refreshbuttons themselves cannot occur be used. The other tests
work, however.
• Minimise: sends the program to the system tray.
• Cancel: closes the program• Refresh

You can add your own selections by means of copy andpaste (or Ctrl-C and Ctrl-V). Forums can be removed bydeleting a field. The order is not important.

Future developments
I am always interested in comments on my programs.
Questions can be asked on my forum:

Visit
http://www.fredvandenbosch.nl/ downloads.html

As soon as a new message appears on a forum it will beshown in the window on a red background. Because thesoftware must check all the forum entries after starting up,
there is a short delay before the screen appears.
Program Features
In the ‘Check’ panel are two fields to complete:• Every x minutes controls how frequently the program checks
the status of the forums.
• Start minimised, If ticked, minimises the program directly tothe system tray; otherwise the program window remains
visible.

28

http://tech.groups.yahoo.com/group/POVIM-Software/

References
1 Mailing lists:
Hoe Werkt Dat
Arne van BelleDe Kunstmaan, October 2003, p.103
2 Discussion groups on the Internet:
Redactioneel
De Kunstmaan, December 2006, p.159
3 Fred van den Bosch
http://www.fredvandenbosch.nl/links.html

www.geo-web.org.uk

GEO Quarterly No 18

Group for Earth Observation

June 2008

Alan Sewards
Introduction
Many of the people who have constructed
MSG systems using the EUMETCast
broadcasts from the Hot Bird-6 satellite
have looked, at one time or another, at theS/N (signal to noise) ratio and BER (biterror rate) data provided by the SkyStar
software. Some have observed that thisdata exhibits quite large changes from time
to time, sometimes accompanied by loss ofimagery. It is the purpose of this article totake a look at the link budget that defines
the level of the various signals in a satellite
communications system, why they are what
they are, and why, sometimes, the levels
change in an unplanned way.
My original plan was to start with agraphical construction showing the groundstations of the link together with thesatellite, with the equations governing eachpart in the appropriate place. I thenintended to use the link budget for the
EUMETCast service as an example anddiscuss it in detail. I requested a copy ofthe link budget through OPS, and wasrather surprised to receive a very polite
reply saying they could not supply one
because the link budget was regarded by
T-Systems, providers of the link, as
proprietary. I can only suppose that was theresult of the emergency action that had tobe taken to get EUMETCast in place when
the downlink transmitter of Meteosat 8(MSG-1) failed shortly after launch.
Certainly, in my own experiences, the linkbudget was the result of a cooperative
effort between the link provider and theuser or customer. In any event, I had to rethink the concept, and in doing so, I
concluded that if the T-Systems link had togo, the equations might as well follow it. As
a result, this article is couched in more orless general terms, although I have tried touse concrete values wherever possible.
Elements of the Communications LinkA satellite communications system consistsof an uplink, a satellite, and a downlink,
together with associated ground stations.
From the user’s viewpoint, most of theaction occurs in the downlink, and it is on
this that we will concentrate; but the uplinkneeds to be understood as certain of theobservable effects occur on it.
At the uplink, a ground station produces asignal that is transmitted up to a satellite
via an antenna that usually tracks thesatellite, although for satellites ingeostationary orbit this is not strictly

30

necessary. At the satellite, an antennaoriented towards the Earth receives thissignal and feeds it into the transponder,
which, despite its name, is functionally an
amplifier. At the transponder output, theamplified signal is fed into another antennathat radiates it back to Earth, towards theuser. The user employs a ground stationconsisting of an antenna and receiver torecover the signal.
UplinkThe uplink usually involves only a single
ground station, so cost is not critical andthe design of the ground station can be
optimised to reduce costs in other parts ofthe system—such as the satellite or theuser stations, of which there may bethousands. In particular, the ground station
can employ a powerful transmitter and big
antenna to ease the requirements at thesatellite for a receiving antenna andreceiver. The goal is to get a noise-freesignal into the input of the transponder.
Depending on the design of thetransponder, there may be a need for finecontrol of the transmitted signal.
Satellite
The satellite requires a receiving antenna tocollect the uplinked signals. As there may
be many transponders on the satellite (24 is
a common number) covering a number ofdifferent frequencies, the antenna isnormally associated with microwave
plumbing (multiplexer/demultiplexer) which
separates the various frequencies andpasses them to the appropriate
transponders.
The transponder consists of a microwave
amplifier (formerly a travelling wave tube
but nowadays usually a solid-state
amplifier) which amplifies the signal to thelevel required for retransmission towards
the Earth (power levels range from watts tohundreds of watts). The amplified signal
then goes in another microwave multiplexer
to combine signals for radiation from thevarious transmit antennas. The satellite
may have a number of downlink antennas
providing beams for coverage of particularcountries or zones, and transponders must
be able to be connected to any of theantennas that might be needed, taking
account of redundancy, to cope with inservice failures.
Finally, the transponders may operate insaturated mode or linear mode. If the

www.geo-web.org.uk

transponder is carrying a single carrier,such as an analogue TV signal, and themodulation type is constant envelope (suchas FM), it may be operated in saturated
mode where the amplifier is driven into
saturation. This simplifies uplink power
control and has the incidental advantagethat variations in uplink signal are largely
suppressed. However, if the transponder
carries multiple carriers (as does the one
carrying the EUMETCast signals), it must
be operated in linear mode to avoid
problems with intermodulation and power
sharing between the various carriers. In thismode the amplifier simply amplifies theuplink signal and any variations in it arefaithfully reproduced at the output.
Downlink
The transponder output is at a power level
adequate to transmit the signal to the user
stations on Earth and is fed into thetransmit antenna which contributes its gain.
The combined effective radiated power isusually specified in terms of dBW, andcontour maps are produced showing thevariation of the power across the coveragearea. An example can be found at
http://www.eutelsat.com/satellites/
13ehb6_popd.html

which shows that the Hot Bird-6 satellite
has an effective isotropic radiated power(EIRP) of 53 dBW at the peak of theantenna beam (that is 200,000 watts).
The radiated signal is attenuated by thefree-space radiation loss (square law), plus
any atmospheric or ionospheric losses andarrives at the user ground station antenna
as a power flux density that is interceptedby the antenna. The signal appearing in theantenna feed is proportional to the flux andthe antenna aperture, and is passed to thereceiver, together with any noise inherent in
the process. Noise is produced by thereceiver front-end amplifier and the antenna
itself, plus any received by the antennafrom space or the Earth or the path throughthe atmosphere.
In a typical user ground station, the noiselevel is determined by the LNB (low-noise
downconverter block). This item, consistingof a horn antenna (the feed horn) and adownconverter for a block of frequencies, islocated at the focus of the dish. The feedhorn is linearly polarised and is rotated in
its holder to obtain the desired polarisation.
Note here that the horizontal or vertical

June 2008

Group for Earth Observation

polarisations specified for the various
channels are only horizontal or vertical at
the LNB for a satellite at the same longitude
as the user. At other longitudes it isnecessary to skew the feed horn to match
the polarisation of the incoming signal.
Overall, the sensitivity of the ground station
depends on the ratio G/T of the antenna(G=antenna gain, T=effective temperatureof the antenna).
Putting all the numbers into the equations
shows what the resulting signal to noise
ratio should be. This figure can then becompared with the specified signal to noise
ratio required for the bit-error ratenecessary for the channel. If it is greater,
the difference is referred to as the margin. It
is available for temporary reductions insignal strength caused by rain, or otherlosses such as misalignment. If the marginis zero or negative, the channel is on theverge of not working, and the slightest
signal variation could result in the bit error
rate rising above the specified value.
User Ground Station Requirements
An obvious additional point is that thereceive antenna should be accurately
pointed at the satellite. This is less easy toachieve than it seems. If the geostationary
satellite is well maintained in its allotted
station and has virtually no orbital
inclination, it appears to stay in the same
spot in the sky all the time. If these
conditions are not met, particularly in termsof inclination, the satellite appears to movein the sky in a figure-of-eight once per day.
If you line up your dish using signal
strength when the satellite is at the top or
bottom of its ‘8’, the signal will be lower
than it should be most of the time. Happily,
the 1 dB beamwidth of a 1 metre dish isabout 1°, and as commercial satellites are
kept to much closer tolerances than that,one should not see even 1 dB variation due
to this effect. In practice, the simple methodof finding the satellite by moving the dish inelevation and azimuth for a maximum, andthen fixing it there, works tolerably well.
Tightening the bolts usually throws thesetting off, so check that this does not

happen. Even taking all precautions, it isprobable that, if instruments are not used,
the antenna could misaligned to the extent
that 1-2 dB of possible gain is not realised if
the loss due to incorrect polarisation skew
is added. Another problem can arise if yourlocation is on the extreme edge of thecoverage area of the satellite, where thesatellite motion could carry your location
down the skirts of the satellite downlink
beam—this has been known to happen with
the Sky system for viewers in Portugal. Sobeg, borrow, or lease some instruments
when you align your dish, or at least use
the built-in software indications.
Link Impairments
What can go wrong and cause reductionsin the expected signal strength? Starting at
the user’s receive antenna, there arevarious possible mechanical problems with
the LNB and cable/connectors. These are
fairly obvious and won’t be discussed
further here except to say that they should
be checked first in the case of any
problems—loss of signal is often traced to apoorly installed connector on the cable to
the LNB or corrosion due to water ingress
into the connector.
The most serious and common cause of
temporary signal reduction is rain. Rainstrongly attenuates Ku band signals
depending on the amount of water in thepath between the satellite and the receiving
antenna. The intensity of the rain and thethickness of the belt of rain in the path are
the important factors. Rain rates of up to
one millimetre per hour exhibit little effect,
while 10 mm/hr and greater causes serious
fades of up to 10 dB (or more). As noted in
the discussion above, heavy rain also
increases the noise level at the antenna,
further reducing the signal to noise ratio.
Trees and their foliage are also potential
absorbers of the microwave signal. This
fact is often forgotten if the tree was barewhen the antenna was installed. This is aproblem that will increase with time as thetree grows. Trees also increase thereceived noise level as the antenna is

GEO Quarterly No 18

looking at something at ambient
temperature instead of cold free space. And
leaves can retain rainwater long after theshower has finished.
Twice a year, for a period extending over anumber of days, the sun will pass directly inthe line-of-sight of the antenna. As the sun
is very hot, it radiates a strong noise that
degrades the received signal-to-noise-ratio
and shows up as a fade. This only lasts fora few minutes: the time taken for the sun totransit the antenna beamwidth of a few
degrees.
At the satellite itself, it is rare for anything tohappen that affects the downlink signal. The
spacecraft is carefully controlled in attitude
to ensure that it stays in its allotted ‘slot’
and that its orbital inclination is kept within
the permitted value. However, periodic
adjustments to the orbit are required toachieve this, and these are done by use of
the on-board thrusters or the operation ofgyros. Such manoeuvres change theattitude of the satellite and this hasconsequential effects on the beams of thedownlink antennas. Depending on where in
the beam a ground station is located, there
may be an appreciable effect on the signal
strength, or little or no effect. It is likely thatmost of the small unexplained variations insignal strength observed by users of the
EUMETCast service arise from this cause.
At the uplink, provision of redundant criticalequipment ensures reliable operation withthe sole exception of rain. Rain has thesame effect on the uplink signal as it doeson the downlink, and heavy rain can result
in deep fades in uplink signals whichappear as deep fades in the received
downlink signal at the user terminal. This is
all the more puzzling to the user as there
may not be a cloud in the sky at his
location! In theory, it would be possible forthe uplink station to compensate for an
uplink fade by controlling the uplink power,
but this would not be attempted for atransponder carrying a multiplicity ofseparate signals nor for situations where
the signal was varying rapidly in time.

GEO Readers’ Internet Survey
Readers who have been subscribers since our Launch Issue four years ago may
recall we included a survey form with that Quarterly. Although we did publish
a sample of the replies, it proved physically impossible to take everyone’s views
on board.
GEO would now like to offer its subscribers the opportunity to voice theiropinions on the Group and to help shape its future. To this end, we haveplaced a new Survey Form on our website, which we would very much like you
to complete.
www.geo-web.org.uk/survey08.html

A summary of the results will be published in the Quarterly later in the year.

www.geo-web.org.uk

31

GEO Quarterly No 18

Group for Earth Observation

June 2008

Les Hamilton

As reported in GEO Quarterly No 16 [1],the first phase of the project to restore
the northern Small Aral Sea—throughimproved water management on the
Syr Darya river and completion of the
Kokaral Dam across the Berg Strait—
was proving much more effective than
had ever been imagined. The image
below, acquired by the Advanced
Visible and Near Infrared Radiometer(AVNIR-2) aboard JAXA’s ALOS
(Advanced Land-Observing Satellite) on
October 10, 2006, clearly shows the
Kokaral Dam. The ground resolution on
this image is a staggering 10 metres!
The 13km-long Kokaral Dam forms awide V-shape in the centre of thescene. The lock in the middle of thedam shows up clearly, as does thewhite spray of water flowing through it
towards the Large Aral Sea. The Syr
Darya river can be seen entering theNorth Aral Sea a short distance east of
the dam.
The Kokaral dam was originallydesigned to raise the water level of theNorth Aral Sea from 38 m to 42 m
above sea level. At the present time,
the waters of the North Aral Sea havealready risen very close to the top of
the dam.
Consequences of the rising sea level
have included more frequent rains in
Aralsk and a generally quieter climate
with fewer sandstorms. In addition,
fish and wildfowl have returned as thewater level recovered. Fishermen are

returning to the city and are planning
to revive the fishing industry bystocking the sea with millions of young
fish and reintroducing the sturgeon.
The second-stage of the $126 million
project is planned to commence in2009. This will include construction of
a second dam, 20 kilometres in length,
to raise the level of the North Aral Sea
even more, plus a canal 46 m above
sea level (higher than the new dam),which will extend directly from the Syr
Darya River to bring water to theharbour in Aralsk once more.
Reference
1 Aral Sea - Les Hamilton - GEOQ 16, p 25.

CreditThe Kokaral dam separating the North and South Aral seas
Image: JAXA

32

www.geo-web.org.uk

Image: JAXA (Japanese Aerospace Exploration Agency)

June 2008

Group for Earth Observation

GEO Quarterly No 18

Compiled by Les Hamilton from reports by

Rob Denton, Nigel Heasman, Alan Sewards, Dave Kitchenham and John Wills
Throughout two days during March thisyear, a plume of dust blew from theeastern Sahara desert across theMediterranean Sea, passing over Cyprus,
eastern Europe and a large part of theBlack Sea. The phenomenon was first
captured by the MODIS instrument flying
aboard NASA’s Terra Earth Observation
Satellite on March 23, which acquired thescene presented at the far right ofpage 35, showing the dust plume justbrushing the western tip of Cyprus thendog-legging east over Turkey and thesouthern Black Sea.
A day later, the Aqua satellite acquired thebeautiful image you saw on our front
cover, which now shows the translucent
plume of dust and sand completely
enveloping Cyprus. The image on page 35
was created by combining the 08:20 and
08:25 UT images, downloaded from the
MODIS Rapid Response website, thenprocessing them with SmoothMODIS andCorrectGeometry as explained on page 11,
before finally splicing them together in
Photoshop.
Image: MODIS Rapid Response Team at NASA/GSFC

Several GEO Quarterly readers observed
the event through their satellite images:
along with others living in proximity to thepath of the dust cloud, they maintained an
informative dialogue on the GEO
Subscribers Internet forum until it
dispersed. Their collective observations
form the basis of this report.
Day 1 - March 23
The first sign of anything unusual in theoffing came from Rob Denton in Bulgaria,
who reported ‘an interesting cloud cover at
the moment’ during the early morning on
March 23. Although the sky was
unbelievably dark for daytime and there
was no rain falling, it seemed to beinterfering with GPS signals. The
temperature was a cool 11°C although it
felt much colder.
Nigel Heasman was monitoring events from
northern Cyprus through both APT and
MSG-2 and noted that the cloud mass wasshowing an ‘incredibly well defined westernedge’. A Meteosat-9 animation showed it

developing over north Africa and moving
northeast, carrying a lot of sand with it.
Nigel provided the false colour MSG imageat the top of page 35 (figure 3). Although it
looked as though it should have been
producing lots of rain, there was none.
Shortly before midday, Rob set off walking
his dog and was soon overtaken by theadvancing western edge of the cloud.
Strangely, there was absolutely no wind at
all at ground level as the cloud passed
over. Almost instantly, the temperature roseby 5°C, and continued to increase, somuch so that he returned home sweating.
After needing the heating on indoors
earlier, it was now a case of opening thedoor to allow the warm 20°C Saharan air
in. The sky was now visible with a highaltitude haze due to the sand and dust.

Day 2 - March 24
It remained extremely hazy next morning in
Cyprus but no sand or dust had comedown. Satellite images showed that the
dust continued to blow northward fromAfrica. Temperatures has increased
throughout the night and it was already
22.6°C by 10 am local time!
Synoptic Details
The synoptic chart below relates tomidnight at the conclusion of March 23,
which shows high pressure over the regionof the suction channel.

Alan Sewards entered the debate, noting
the remarkable extent of this ‘sandstorm’.
By mid-afternoon, the cloud mass extended
almost 2000 km, and the suction channelover the African coast, from where the sandwas being drawn, was about 200 km wide.
‘There must be a lot of sand sitting up
there waiting to come down with the rain’.
The Meteosat HRV images were showing agreat deal of detail in the suction channel;
one could even see dust plumes being
kicked up by the wind as the front moved
across the ground.
In Cyprus, the sky was becoming
increasingly hazy as sunset approachedthough the sand had yet to fall to ground.
Interestingly, the humidity increased while
the temperature remained almost constant,even two hours after sunset. And
completely still at ground level.
Facts and Figures
After spending some time making adetailed analysis of MSG images, Alan
discovered that, at 1500 UT, the cloud topsof the main mass of cloud were at atemperature of -66°C, which meant thatthey were high-altitude clouds, probably
between 12,000 and 15,000 metres. At thesame time, the temperature of the sandclouds (while still over the Sahara), were at
0°C or less, indicating that they had
already been lifted to around 3,000 metres.

www.geo-web.org.uk

Figure 1
The sea-level pressure chartat 00:00 UT on March 24
Chart created with Digital Atmosphere Equinox

Alan noted that the dense black cloud
ignored the presence of this high pressure
and just sailed over it, strongly suggestingthat it was associated with the jet stream.
Looking back to imagery dating from thestart of the phenomenon, in southern
Tunisia at around 12:00 UT on March 22,
some strands of typical jet stream cloud
travelling from SW to NE were evident.
Quite suddenly, within the space of anhour, these became mixed up with asandstorm and the sand began to track NE.
The intensity rapidly increased until thecloud took on the appearance of figure 2.
So, it looked as though the ‘black cloud’was a jet stream cloud which had somehow
become laden with sand; but how the sandgot up from ground level to thestratosphere, and why it kept rising until the33

GEO Quarterly No 18

Group for Earth Observation

June 2008

Figure 2
The cloud and dust plume, imaged at 06:30 UT on March 23 by Alan Sewards
Image © EUMETSAT 2008

source was cut off, is a mystery. But Rob’s
observation that there was no wind beneaththe cloud certainly seems to tie in with it
being a jet stream cloud.
Around 15:00 UT, with the temperature in
Bulgaria an incredible 25.6°C (for March),and snow forecast for the following day,Rob at last found his car dusted with
Saharan sand So spectacular was the dust
cloud that it made the television news in
Bulgaria (though not the weather forecasts),
and the Sofia News Agency reported ‘brownrain’ falling over the city of Sliven, where it‘covered buildings and car windscreens’
and left brown blotches all over the ground.

significantly (figure 5), yet only an hourlater, as the dust cloud receded eastward,
the sky became a deep, clear blue
figure 6). Following this dramatic clearance,
the wind suddenly picked up from a mere
5 km/h to around 30 km/h while thetemperature fell from 20°C to 15°C—and it
suddenly felt quite cool. The dark layer ofdust was topped by white cumulus which
made it stand out very well (figure 6).
Dave confirmed that the dust cleared
eastwards very suddenly around noon andseemed to have a distinct boundary edge.
Temperatures dropped to a moreseasonable 22°C. No rain fell throughout
the event.

In northern Cyprus, however, Nigel reported
only a little, very fine, brown sand, hardly
enough to bother with, and absolutely norain! Meanwhile, Dave Kitchenham, amember from southwest Cyprus, reported
that he had experienced an unseasonably
warm night with an overnight low of 20°C.
The morning had dawned very hazy butwith an otherwise clear sky and a lightcoating of brown dust on everything.

Cyprus’ Coptic Winds
John Wills, submitted figure 2, a NOAA-18
APT image acquired around 11:00 UT on
March 25 from his location in southern
Cyprus. The dust storm had been hanging
over Cyprus for several days but, on the
25th, a Coptic Wind sprang up and started
to clear the dust away from the island.

The Aftermath - March 25
Nigel photographed the scene as the dust
cloud passed overhead and finally cleared
his location (see satellite image on front
cover). Before the clearance, a strong
sand-induced haze had reduced visibility

For several days before the 25th we had
experienced hazy sunshine due to the dust,
and temperatures well above seasonal
average. The morning of the 25th began
similarly hazy, and very warm, but by latemorning a strong westerly wind wasdeveloping, which gained strength, clearing

34

www.geo-web.org.uk

the atmosphere and lowering thetemperature to the seasonal norm. This
Coptic Wind lasted for approximately threedays .
According to reports in the Cyprus
newspapers, the frequency of dust storms
is on the increase. Whereas a few years
ago Cyprus could expect two or three dust
storms a year, they have now increased to
10-16 per year.
During this particular storm, dust levels
reached three times the EU recommended
level of 50 micrograms per cubic metre. It
was further reported that cardiovascularincidents have risen by 10% during theseincreasingly frequent Saharan dust storms .
The Coptic Winds are a series of thirteen
winds that occur throughout the year in
Cyprus and each has a name.They havebeen known since antiquity and almost
always arrive plus or minus 24 hours of
their predicted date.
One—called ‘Hawa’—was predicted toarrive on March 25, and did so on time; it’sname means the wind gale. The previous
Coptic Wind, due on March 20, was ‘El
Shams El Kebira’, which means Big Sun
Gale. The next one is ‘Khamseen Winds’,
the Sand Laden Wind, due on April 29.

Figure 3
False colour image of the dust cloud
Image: Nigel Heasman

Figure 4
A false colour NOAA-18 APT image fromsouthern Cyprus showing the dust cloudat 11:00 UT on March 25
Image: John Wills

Figure 5
The dust arrives, causing thick haze that almost
obscured a mountain just 10 kilometres distant.
Photograph: Nigel Heasman

Figure 6
The dust cloud departs, topped by fluffy
white cumulus cloud.
Photograph: Nigel Heasman

GEO Quarterly No 18

Group for Earth Observation

June 2008

Les Hamilton
Early this year, Robert Moore initiateda discussion on the GEO-Subscribers
Internet forum regarding a prominent
feature seen in images of Russia’s
Kamchatka Peninsula. ‘A clear circular
object with incised contours’, thefeature had the appearance of a large
volcano situated at 56.6°N 157.2°E.
The location is circled on the NOAA-17
image below, acquired on January 19.

A Landsat image dating from 1972
Image: NASA

Image: NOAA CLASS Archive

The structure is a massive early
Pleistocene shield volcano called
Bolshaya Ipelka. Located on an eastwest tectonic line, this large volcanic
caldera, surrounded by a ring-shaped
ridge with steep inner walls and rocky
outer slopes, comprises the remains ofa great volcano that has been
extensively eroded by glaciers. It is thelargest volcanic structure in southern
Kamchatka.
Detail of the massif’s radiating ridges
is revealed in the 1972 Landsat imageat the top of this page and in the
superb astronaut image taken from theISS in 2002.

36

Snow capped Bolshaya Ipelka, imaged from the ISS in 2002
Image ISS004-E-11691 courtesy of the Image Science and Analysis Laboratory
at NASA Johnson Space Center (http://eol.jsc.nasa.gov/).

www.geo-web.org.uk

June 2008

Group for Earth Observation

GEO Quarterly No 18

John Tellick
I’m sure we are all aware that Russia has a successful spaceindustry, a spin off from the Soviet era: several European satellites
have been launched on their rockets, and Russian supply vessels
help to service the ISS. But I wonder how many remember or knowof the Soviet space shuttle?
German TV news programmes on April 7 showed what was clearlya ’space shuttle’ being transported down the river Rhine, on a
massive barge, for a 385 mile journey from Rotterdam to theTechnik Museum in Speyer, SW Germany. This was a relic fromthe Soviet era, the Buran space shuttle, the tail having been
removed to clear low bridges during transit. Having forgotten about
this craft, I did a little research.
Development of Buran began in the early 1970s as a response the
US Shuttle programme. It seems Soviet engineers favoured asmaller lighter vehicle but the military pushed for a direct copy of
the Shuttle in order to maintain ‘super-power parity.’ The
construction of the Buran shuttles began in 1980 with the first fullscale vehicle rolled-out in 1984. Sub-orbital test flights had takenplace during 1983 using a scale model.

The Buran Shuttle

The Buran 1.01 launch on
an Energia booster.

I seem to remember quite a bit of publicity about the craft and one
was impressively on display atop a Soviet Antonov 225 aircraft(specially built to transport the Buran, and still the largest aircraft in
the world) at the 38th Paris International Airshow at Le Bourget inJune 1989.

Buran being carried down the Rhine to Speyer

other craft were, apparently, fitted with jet engines in order to test
their handling in the atmosphere and sub-orbital flight.
Of course, this was the era of the Mir space station, and a shuttle
would have been a great asset in servicing it. It has to be said that
the Soviets did an amazing job building Mir without a shuttle.
I think it’s correct to say there were many problems with the Buranand the project was cancelled in 1993. On May 12, 2002, a hanger
collapsed due to poor maintenance, killing eight people anddestroying a Buran shuttle, which is thought to have been the 1.01
that actually orbited the Earth. Also destroyed was a mock-up of
the Energia booster rocket.
Buran atop a Soviet Antonov 225

Several craft and/or prototypes were built but only one was everlaunched into space: Buran 1.01, from Baikonur, on a speciallydesigned Energia rocket, on November 15, 1988. It was unmannedand orbited the Earth twice in 206 minutes before making a
successful automated landing back at Baikonur, despite windy
conditions, on a specially constructed shuttle runway. Some of the

A new hall has been built at the Technik Museum Speyer to house
the Buran shuttle. Their many other exhibits include a Soviet
Concordski, a French Concorde and a jumbo jet. Dare I suggestthat the Buran suffered a similar demise to the ‘Concordski’—theTupolev 144.
Acknowledgements
Wikipedia
www.russianspaceweb.com
Technik Museum Speyer - www.technik-museum.de

www.geo-web.org.uk

37

GEO Quarterly No 18

Group for Earth Observation

Robert Denton - LZ/G4YRZ

e-mail: g4yrz@wxsat.org

GPS in my weather station I hear you say? This is what
sparked me to write this article after one comment by amember on the GEO-Subscribers group on the Internet:‘surely they don’t still use that!’ Well I certainly do—and I
know of many others who do. It’s not as antiquated as you
think. My PC clock is never more than half a second inerror, which results in perfect overlays on my images. GPS
will also serve well in the upcoming lightning display project
I’m planning, where synchronisation is important whensharing information with other stations for triangulation
purposes.
In order to receive accurately aligned overlays on weather
satellite images, your PC clock must be accurate and the
Keplerian data you use must be up to date. I have read
numerous messages from members of Internet bulletinboards stating that their system was not working properly.
Many blame the software and it’s creators, when all theyneed to do is keep accurate time on their PC. Many of us
were ignorant of the fact (myself included) that if a PC clockis inaccurate the software will simply not work as intended.
That’s why much of the weather satellite software includes afacility to keep time, change coordinates for those who
operate from different locations, and keep Keplerianelements up to date.
I have been experimenting a little with GPS (Global
Positioning System), which is basically a group of at least 24
Medium Earth Orbit (MEO) satellites placed around theglobe, originally for military purposes, to give accurate
position, time and speed. The combined GPS
receiver/antenna that I use is shown in the page masthead.
It measures about 6.0 x 4.5 cm and cost only £20 on ebay(£10 for the unit from USA and £10 post, packing andinsurance.
Many of us can also use another method for synchronising
our PCs—the atomic time signal from Anthorn in Cumbria
on (MSF 60 kHz), formerly at Rugby, and Frankfurt,
Germany (DCF 77 kHz), which can also be linked to yourPC; but as I see it, GPS is the cheap and easy way to go,units with receivers and antennas combined now costingfrom around £20 new.
A GPS receiver can also serve another purpose. If you have a
laptop, Palm Pilot or even certain mobile phones, you can
use the GPS just like a standard car GPS system. I know! I

tried it and it works. You can have great fun, fox-hunting,playing guessing games, fun for the whole family. A GPS
system for £20! Wow! I wonder how many of you will betrying this now? Have I got your attention yet?
What we are really concerned with here is weather satellite
applications, so I will use examples in the software I use andhow to apply it.
One piece of software I use for APT reception is APTdecoder
written by Patrik Tast of Finland. I use this mainly because
it’s free and it meets the needs of my APT station, providing
excellent results completely
automatically. Figure 1 shows
the ground station screen,
which opens when you selectSettings/Ground station. When
you click on the GPS logo, theGPS screen appears (figure 2).
On the GPS screen, first click
Setup device to reveal the GPS
Setup screen. Now click theport arrow to select the port
your gps device is connected
to. If you don’t know which
port to select, right click
My Computer-PropertiesFigure 2
Hardware-Device ManagerPorts, where you will be shown which port you are using.
Then click Find GPS device: the software automaticallysearches for it and the data starts rolling in showing yourlatitude, longitude and altitude. Enter your station details,
then click Add followed by OK to save. You can also update
your station info and add more stations using the add,
select and update icons. There is also a button forsynchronising the time. I’m well impressed.
Another instance where I use GPS is with my registeredversion of David Taylor’s satellite tracking software WXtrack.
(The GPS option does not apply to the unregistered version).
On the Setup tab, click the Edit button in the ‘My location
details’ panel and in the edit box that appears (figure 3) edit
your location details. Click on Setup GPS Port to open
another edit box (figure 4), where you can enter the COM

Figure 138

June 2008

Figure 3

www.geo-web.org.uk

June 2008

Group for Earth Observation

GEO Quarterly No 18

Cover and Full Page Images
Front CoverThis image of a major Saharan dust storm blowing
across Cyprus was captured by the MODIS flight
instrument aboard NASA;s Aqua satellite. You canread eye-witness reports of this event in an article
starting on page 36.
Image: MODIS Rapid Response Project at NASA/GSFC

Inside Front CoverDavid Taylor spotted this fascinating double
depression off the Pacific coast of Canada, datingfrom February 23, 2008, on a GAC composite image
produced on his AVHRR Reader software.

Figure 4

port settings etc. These settings vary with systems but I found theuniversal settings which work for me are: Baud Rate 4800, data Bits
8, Stop bits 1, Parity None, Flow None. You don’t have to know what
this means (I don’t) but these settings work on all my weather satellite
software. Once the details are entered, simply click Read GPS Dataand your coordinates are automatically displayed on the screen. This
saves trying to work out your location and entering all the details
manually.
I’m certainly not an expert on GPS: in fact I’m just learning by
experimenting. I am also running a Trimble GPS system here. If there
is sufficient interest I will write an article on that. It really sings anddances and I got mine for free from a friend. It can also be used with
Google Earth and other software.
So, to round off, next time you hear ‘GPS’ remember: this is a system
which can greatly help you in your weather satellite applications forvery little outlay. It is not as outdated as some may think. In fact,
another GPS satellite was recently launched!

Pigeons in my Meteosat Dish
Anthony LoweEver since David Taylor showed us an image of birds on his X-dipole,several other readers have followed suit. But my bird image is a little
different.
Following Meteosat-7’s final image I intended to get the ladders out
and take the dish down—but I still haven’t got round to this and thedish remains in situ.
I have had problems over poor reception due to nearby conifers, andlast summer my next door neighbour promised to have them cut
back. On Friday March 14, I came home and found, to my surprise,that the conifers had been reduced by some six feet. Once again it has
been a pleasure to receive images from the far Atlantic.
But there was one snag: the trees had been cut down during nestingtime, and two wood pigeons had been made homeless. Normally, my X
dipole was their usual perch but for the next 48 hours they were
nowhere to be seen—until I eventually spotted them perched on top of
the old Meteosat dish. Shortly after I noticed they where collecting
twigs to build a new nest. As the photograph on the inside back coverillustrates, they have now built a new family home directly behind thedish, and there is now a youngster among them. I’ve never been a'feathered' bird watcher before but on this occasion I have stuck a
webcam to the inside of a window from where they can easily beobserved.
So I now have another excuse not to climb any ladders!

www.geo-web.org.uk

Inside Back Cover
Top: This splendid March 5 Metop-A image was
acquired by Alan Banks, and shows northwest USA
and western Canada in the grip of winter. The loop of
the Columbia River and the Cascades volcanoes,
Mounts Rainier, Adams and St Helens in Washington
State show up particularly well.
Image © EUMETSAT 2008

Lower Left:
Anthony Lowe sent in this photograph showing two
wood pigeons actually nesting in a disused Meteosat
wefax dish. At the time of writing, the first chicks had
hatched.
Lower Right:
Nick Bird sent this photograph of a crow perched on
his turnstile antenna to Francis Bell, who forwarded it
to the Quarterly.
Back Cover
Jean-Louis Fenasse sent us a superb false colour
NOAA-18 HRPT image that he acquired from the
12:46-13:01 pass on February 25, 2008, from his
location near Nice in the south of France. Reception
lasted an amazing 14 minutes 56 seconds andstretched deep into the Sahara. The northern part ofthe image is reproduced. Reception was achieved
using WinHRPT software while the false colour
processing was done using David Taylor’s HRPT
Reader.
Page 14This remarkable image of the Antarctic Peninsula,completely free of cloud, was captured by Terra’s
MODIS instrument on February 26, 2008.
Image: MODIS Rapid Response Project at NASA/GSFC

Page 29
Mike Stevens downloaded this fine Metop-A image
providing amazingly cloud-free views of Patagonia,
Tierra del Fuego, the Falkland Islands and theAntarctic Peninsula on March 3, 2008.
Image © EUMETSAT 2008

Page 40
This beautiful image from Metop-A, stretching from
Hudson Bay to Georgia, shows North America beset
by ice and snow. Mike Stevens received it on
February 28 this year, via EUMETCast.
Image © EUMETSAT 2008

Page 44
Mike Stevens downloaded this fine Metop-A image
showing an interesting cloud formation over the Gulfof Aden at 06:13 UT on February 26, 2008.
Image © EUMETSAT 200839

June 2008

Group for Earth Observation

GEO Quarterly No 18

Douglas Deans – dsdeans@tiscali.co.uk
Welcome to this new look column
which has been renamed to betterreflect the change in content. As wasannounced in the previous GEO
Quarterly, the Software Library has
now been discontinued. The readily
available and inexpensive access to
the Internet by Broadband now
means that the simple, immediateand no-cost route for the latest
software is by download. This has
been reflected in the huge drop in
demand for CDs over the past few
years. My thanks to all those who
supported the library.
Following my request to themembership for comments on mysuggestion of including a small Q andA section on computers/software, theresponses I have received have all beenvery positive. My thanks to all those
who took the trouble to contact me. So
starting this issue, I propose toinclude, on an experimental basis, afew questions and answers relating tocomputer issues. I would welcome
feedback both on the content andpresentation. Perhaps a few
introductory words of explanation
concerning this new part of my column
would be beneficial.
GEO Quarterly is not, of course, acomputer magazine: there are plenty of
those available to purchase elsewhere.
However, we cannot ignore the fact
that, to fully enjoy our hobby, the useof computers is essential. I offer ahelpline service, along with others, to
GEO members (see centrefold iii for
details) and I have found that theresolution of some problems is
exacerbated by an inability to carry out
certain basic computer operations.
Again, as I said in my last column, thisis not a criticism but a factualcomment. My intention, therefore, is tofield questions and answers that are
most relevant and helpful to our
specific hobby; I will also be dealing
with issues most commonly
encountered during helpline
discussions.
Undoubtedly some readers will findcertain questions very basic but
nevertheless they are the ones thathave created problems. Let me also
make it very clear that, whilst I

consider myself to be computer
literate, I am no expert and certainly
there will be readers who may see
better or alternative solutions to someof the matters raised. It also has to beremembered that often there may be
several ways of getting the same resultin a computer operation; the best
method may not necessarily be thequickest but the one with which you
are most comfortable.
I will also continue to report on any
software updates as and when I spot
them and provide readers with therelevant links for download of thelatest information and software.
As David Taylor has produced such alarge suite of satellite-related software,
which is regularly updated, and as
many of the questions do relate to thissoftware, I intend to list the latest
versions of his programs in each issue.
Computer Q and A
There are two issues I would like toaddress this quarter, both relating to
the need to view the contents of yourhard drive.
I often find that I have to ask a caller
to open a particular file within a folder.
However, a file is defined not just by
its name but the extension that
follows—that is the bit after the fullstop. So a file called Douglas.jpg isquite different from one called
Douglas.txt (the first would be animage file and the second a text file).
By default, Windows XP and Vista bothhide these file extensions. So if the two
above files were sitting in the same
folder they would both show as
Douglas. This can make identificationdifficult and demonstrates the need to
be able to view file extensions. Thiscan be easily remedied.
To show file extensions on XP• Open Control Panel• Select Folder Options• Select the View tab• In Advanced settings, untick ‘Hide
extensions for known file types’
To show file extensions on Vista :• Open Control Panel• Select Folder Options (see mycomments below)
www.geo-web.org.uk• Select the view tab• In Advanced settings, untick ‘Hide
extensions for known file types’
Just a comment about the Control
Panel in Vista. There are two viewing
options for this, comprising Control
Panel Home and Classic View.
Personally, I find Classic View much
simpler to use, and far easier forfinding specific headings as each has

Software Updates
APT Decoder v 2.0.5.81 (15th March 2008)
There have been a number of updates to thisexcellent program from Patrik Tast. Let me
remind you that this software, which is free,
can be used to record and decode APTtransmissions and has a host of other very
useful features. Updates and fixes include:• Fixing an exception when the R2FX
receiver was tuned from the tuner window• Added a detailed process list to theprocess window• Users can define how many days to keep
the same log in the General settings Webtab• Daily log options.
• Modified NOAA 17 channel parser
To learn more about this program and to
download the latest update please visit
http://www.poes-weather.com/
and follow the relevant links.

David Taylor’s programs
The latest releases at the time of writing were
ATOVS Reader
AVHRR Manager
DWDSAT HRPT Viewer
GeoSatSignal
GRIB Viewer
GroundMap
HDF Viewer
HRPT Reader
Kepler Manager
MapToGeo
Metop Manager
MSG Animator
MSG Data Manager
PassControl
SatSignal
Sea-Ice & Viewer
Wxtrack

v 1.1.2
v 1.5.0
v 1.0.4
v 6.1.2
v 2.1.6
v 2.0.6
v 1.2.0
v 2.7.2
v 1.2.8
v 1.1.4
v 1.2.2v 2.5.18
v 2.5.18
v 3.1.0
v 5.1.0
v 1.3.4
v 3.6.8

To learn more about this program and to
download the latest update please go to :http://www.satsignal.eu

41

GEO Quarterly No 18

Group for Earth Observation

The Control Panel Classic View where each option has its own icon

The Control Panel Home screen where options are hidden behind folder icons

42

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June 2008

June 2008

its own icon. Control Panel Home isbroken down into groups and it can bedifficult to find a topic within a group.
For example ‘Folder Options’ is in the‘Appearance and Personalisation’group: but you can’t see that until you
actually open it (see images at left).
You may waste time checking othergroups before you find it.
Another important issue is being able
to look at the content of your hard
drive so that you can checkfolders/files. There are several ways todo this.
Checking Folders/Files in Windows XP
The best way here is to use Windows
Explorer (do not confuse this with
Internet Explorer). This is afundamental application within
Windows which shows you how yourcomputer is organised and makes
looking at folders and files verystraightforward.
To open Windows Explorer, go to theStart button then follow All programs →Accessories and it is listed there. A
shortcut for this is extremely timesaving and can simply be done by
dragging and dropping on the desktop.
It is also possible to simply click
My Computer and then select yourhard drive. However, whilst this does
show the full contents of your drive, itdoes not include other drives such as
DVD writers etc., which are shown in
the Explorer option.
Checking Folders/Files in VistaThe simple way to do this is to click
the Widows Start button and selectComputer (or use the desktop icon).
Click on your hard drive reference(example Local Disc (C:)) and drag it on
to the Desktop as a shortcut. You now
have an immediate way to bring up awindow showing the hard drive
contents as well as other drives,
network information etc. Note thatwhen you select Computer from theStart button, you can in fact drag thaton to the desktop (if it is not alreadythere) as a shortcut but I find this lessuseful as the C: drive contents are notimmediately displayed as they are withthe previous method described.
It is also possible to do this using
Windows Explorer which can be foundfrom the Windows Start button andfollowing All programs → Accessories →Windows Explorer. Again, a shortcut
can be placed on the Desktop for quick
access. The Explorer method also has
the disadvantage that the C: drive is
not opened immediately on the display.
There is a way to do this but that is foranother day.
This article has looked at two very
fundamental issues. In future columns
I hope to also include some moreadvanced options.

Group for Earth Observation

EUMETCast Without RAMdisk
Well, as promised, here is my letter
regarding the working conditions of mysystem which did cause some
controversy at the time. However, it’s
been over one year since the separate
USB hard drive was placed into
operation and I have to say it has
worked perfectly with no overheating or
failures of any kind. And the picturesof course have been stunning.
Ever striving to achieve the best results
possible, I am now in the process ofmodifying the complete system to havea dedicated Metop PC but it has notbeen without its problems. Whilst in
the process of setting up, my Acer
laptop failed big-time. I was planningon a three-computer system, so thishas now come to a standstill while
waiting to have it repaired.
At the moment I am using a low
specification ASUS PC as the receiving
unit and networking with the EMachine which does all the decoding,with excellent results. The Lacie hard
drive is still in the system for back up
and file and picture storage.

GEO Quarterly No 18

SatScape Problem
Having recently had a glitch with my
SatScape program, I thought that othermembers may have had the sameproblem and have not worked out what
was the cause.
I recently started up SatScape v 1.87
on my PC running Windows 98, only tofind that part-way through start-up anerror message came up: ‘An illegal
action has taken place.’ The program
promptly closed down. I then tried toopen the software on my Windows XP
Home PC, only for another error
message to appear: ‘Wx tracking error.’
Again, the program closed down.
I tried reloading v1.87 from CD, but
again, still the same error messages. I
then downloaded SatScape from theInternet, which was SatScape v 2.02.
Once loaded, this version perfectly on
both PCs.

Well that’s it for the moment. I will let
you know when I can restart myexperiment again. It will all depend on
what happens with the laptop andwhether it is powerful enough to be
used as part of the new system. In themeantime thanks to everyone for yourhelp and advice. Best wishes and a
happy weather watch from Portland.

The following morning, having hadtime to think about the subject, I
deleted SatScape v 2.02 from theWindows 98 PC and reloaded SatScapev 1.87, which now worked perfectly!
The reason for my problem was thatthe day before was the February 29;
clearly, Satscape v 1.87 did notrecognise that date.
Oh yes! Why go back to version1.87?
Just personal preference, as I do not
like the menu start-up window always
being active on v 2.02 whereas, with
v 1.87, pressing F3 takes you to thenext window and closes the start-up
one.

Mike Stevens (G4CFZ), Portland, Dorset.

Laurence Holderness, Pembrokeshire... continued from page 27

APT receiving antennas are (or try to be)omnidirectional. Fortunately, the orbits of
the Orbcomm and NOAA satellites are
sufficiently different that the interference isrelatively rare.
Conclusion
This brief article has attempted to describe
several commonly encountered types ofinterference that may be experienced byamateurs receiving weather satellite
transmissions. As with many problems ofthis type, every case tends to be different,
because of the different locations, receiver
types, feeder cables and antennas in use.

www.geo-web.org.uk

Because of this, a certain amount of try-itand-see experimentation is called for if theapproaches described in the article do notwork straight off. Good luck!
The author of this article is willing to offer
advice on the subject of interference.
Please emailalan.sewards@free.fr

If you can attach a small image to theemail, preferably in jpg format, which shows
the problem, together with a description ofyour receiving system, this will greatly help
the diagnosis.

43