Group for Earth Observation

The Independent Amateur Quarterly Publication for

Number 2

Earth Observation and Weather Satellite Enthusiasts

May/June 2004

Inside this issue . . .
Create a Radio Horizon
Table for your Location
Bill Johnston explains ...
David Taylor reports fromDarmstadt as MSG finallygoes operational
John Coppens details how
to decode the NOAA APT
satellites under Linux(and Windows) using
WXtoImg
Utilising satellite-TV
co-axial cable in yourweather satellite station
Van Karman Cloud
Vortices: Where and why
do these amazing cloud
phenomena occur?
Is planet Earth slowly
committing suicide?
Francis Bell debates theissues ...
The MSG EUMETcast
reception system - John
Tellick explains ...
The Indian Space
Programme - part 2. Morefascinating insights fromPeter Wakelin
and much more ...

NASA’s Terra satellite acquired what is believed to be the first ever direct observation of a cyclone in the South Atlantic Ocean
on March 26, 2004. This Moderate Resolution Imaging Spectroradiometer (MODIS) image shows the storm off southeast Brazil.
Image: Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

A blue halo of phytoplankton curls around the Falkland Islands in this amazing true-color Aqua MODIS image from January 26, 2004.
Image: Jacques Descloitres - MODIS Land Rapid Response Team, NASA GSFC.

GEO is led by
Francis Bell
Clive Finnis
Les HamiltonPeter WakelinWelcome to the second issue of the GEO Quarterly. Our thanks
to all of you who applied for a copy of our Launch Issueearlier this year, and specially to everyone who contacted us
with supportive comments.

Nigel Evans
Ray Godden
John Tellick

CONTACT INFORMATION

B

Public Relations and Education
Francis Bell,
Coturnix House,
Rake Lane,
Milford,Godalming,
Surrey GU8 5AB
EnglandTel:(01483) 416 897
e-mail: 100523.1037@compuserve.com

T

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

y the time you read this, the first GEO Symposium will havetaken place at the National Space Centre in Leicester. Lookup the GEO website (http://www.geo-web.org.uk) to viewphotographs taken on the day. A full illustrated report on the
Symposium will be published in GEO Q3.

his quarter, we have several interesting contributions fromoverseas readers. Bill Johnston explains how to compile aRadio Horizon Table to help make the most of those low
elevation satellite passes; Fred van der Bosch details an
improved technique for integrating satellite images into
Digital Atmosphere; John Coppens describes how Linux
users can decode NOAA APT using WxtoImg while Arne van
Belle extols the virtues of satellite-TV coaxial cable.

There are also regular submissions from stalwarts Francis Bell,who has some controversial ideas on global warming andclimate change, and Peter Wakelin, who continues on thetheme of the Indian Space Programme.

We do hope there is something to everyone’s taste in thisissue—now turn the page and enjoy your copy of GEO Q2.

Contents
GEO News
The Indian Space Programme - part 2
Meteosat-8 Operational Imagery on the WWW
Earth Imaging News
Using WXtoImg Images in Digital Atmosphere
Coming in the Next Issue ...
‘MSG Goes Operational’ Event
Moonlight Sonata . . . in sea
Using Satellite TV co-axial Cable
New Download Address for WXSAT Software
MSG EUMETcast Reception
Cyclone Gafilo Swamps Madagascar
View from the Other SideSouth Sandwich Island Cloud Wakes
Death of a Planet by Autotrophic Suicide
Measuring Evaporation
A Radio Horizon Table
Copy Deadline for GEO Q3
Weather Satellites and their Frequencies
WXtoImg - APT under Linux and Windows
Receiving Weather Satellites in Belgium
European Publications on-line
Visit the GEO Website
Cover Colour Images
Software Showcase
The Weekend the World’s Weather Went Crazy
In Tray - Readers’ Letters and Queries
Why are south Atlantic Hurricanes so Rare?
Von Kármán Cloud Vortices

Articles and Images for Publication
Les Hamilton,
8 Deeside Place
Aberdeen AB15 7PW
Scotland, UKe-mail: editor@geo-web.org.uk
Membership and Subscriptions
Nigel Evans,‘Eventail’, 7 Gloster Ropewalk, Aycliffe,
Dover CT17 9ES
England, UKe-mail: members@geo-web.org.uk
Meteorological Consultant
Peter Wakelin
e-mail: meteo@geo-web.org.uk

Publisher

Francis BellPeter WakelinPeter Wakelin
Fred van den BoschDavid Taylor
Francis Bell
Arne van BelleJohn Tellick
Arthur Andrews
NASA
Francis Bell
Cedric Roberts
Bill Johnston
John Coppens
François Verstraelen
Simon Kennedy

Douglas Deans
Gerry BergPeter Wakelin
Les Hamilton

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46

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 4975595.
The registered office is Coturnix House, Rake
Lane, Milford, Godalming, Surrey GU8 5AB
Printing
Toptown Printers, Vicarage Lawn,
Barnstaple, Devon EX32 7BN.
Responsibility for Constructional
Projects and Software
Every effort is made to ensure that the technicaland constructional articles published in thisQuarterly are correct. However, the ultimate
responsibility is with the reader to ensure thesafety of constructions and for any interfacingwith other equipment. GEO cannot accept
liability for shortcomings in any published designor any constructions carried out by members orother third parties.
Copyright GEO © 2004
The contents of this Quarterly remain theintellectual property of the Group for Earth
Observation Ltd. and its contributors. Copying oftext or images, either from the printed Quarterly
or from any electronically stored source, isforbidden without permission from the editor.

GEO Quarterly No 2Group for Earth Observation

May/June 2004

Francis BellIn writing this introduction my first task is clear andpredictable. It is to express my admiration for the teamwho, in such a short space of time between GEO's
conception and its first publication, have done so muchplanning and used so much of their precious time forthe benefit of potential members. Included in there
should also be thanks to those who contributed text
copy, data and images for the launch issue of GEO Q1:
without such contributions we would have little topublish.

Feedback
From the feedback we have received it would be
difficult to judge GEO Q1 as anything other than avery great success. At the time of writing, hundreds ofour publications have been distributed and thestatistics indicate that about 38 % have gone overseas,
the rest of course within the UK.
The feedback we have received has been complimentary and encouraged us to continue with the future
programme of the new group. GEO's editor has told methat he already has plans for GEO Q3. Copy alreadyexists, and we hope to include a report about our
Leicester meeting at the National Space Centre on 1st
May 2004. This will be followed by GEO Q4, with areport about our anticipated activities at the AMSATUK colloquium in Guildford at the end of July 2004.

Joining GEO
If you have not yet joined GEO, please do. The groupdoes need to be financially viable from its
membership's subscriptions because GEO has nocommercial support. Indeed, as a matter of policy, we
have decided to be independent of any commercial
support. Advertising of course will be accepted in due
course. The very modest £12 a year must be the bestvalue-for-money subscription anybody interested in anamateur, technical or educational matter can spend.

1. Our group must continue with a high profile forthe benefits of the membership. We should
represent the interests of direct-readout amateurs
and educational users to national andinternational bodies. The UK Meteorological
Office, EUMETSAT, NOAA, WMO, Ofcom andothers must remain a priority for us. The
achievements
thatmembersof
GEO's
management have already established should not
be underrated. If it had not been for thiscommitment in the past our access to our hobby
would not be as attractive as it is today. This work
must continue.
2. GEO needs to service the needs and interests of
those individuals and institutions alreadyfamiliar with weather satellites. We need to keep
up to date with a changing technology, fromWEFAX analog to digital, with the associatedhigh-speed data processing that goes with it.
3. We need to service the needs of absolutebeginners. The commonest comment I receive
either on paper or email is: ‘How do I/we getstarted with weather satellite reception.’ GEO
must support these people. To raise expectations
for potential members and then fail to service thisdemand would be unkind.
4. It has been very striking since GEO was featured
in the Times Educational Supplement (March
2004), that there is a demand from a wide
spectrum of schools for information about getting
started with weather satellites. Again the ‘How do
I do that’, request? Of these enquiries, about athird have come from geographers, a third fromscientists and the rest from educational advisors
and head teachers.

SupportSchools and Education

Werkgroep Kunstmanen, the user group based in the
Netherlands, have been very supportive of GEO and a
special thanks must go to them. Some of them arecoming to Leicester. Likewise, thanks for the support
we have received from Australia and the USA, plus
many other countries.

It would be of great benefit to schools if a practicing
teacher accepted an advisory role within GEO for
education. Firstly to deal with how to get started thensubsequently to address the benefits within educationof following such a strategy. Live weather satellite
reception is not a solution looking for a problem tosolve; rather, it can broaden the perspective andopportunities within the existing curricula.

Other Issues
There are of course issues which our new GEO
organisation must face. We are pleased to addressthese. From my perspective four spring readily to
mind.
Page 2I am a retired science teacher myself and I know thebenefits of these activities in schools, but time
constraints prevent me from taking on this role withinwww.geo-web.org.uk

May/June 2004

Group for Earth Observation

GEO. This is an invitation for someone to take on a rolesuch as this. Somebody go for this please! Some
educational news or pages in our quarterly publication
would be welcome.

Administrative Structure
Some potential GEO members have asked about theadministrative structure of our new organisation. The
response is easy. A decision was taken by GEO's
management group to form the company Group for
Earth Observation Limited. This is a company inEngland and Wales, limited by guarantee but having
no shares. The framework for this company was
professionally written and describes in broad terms
GEO's interests in weather satellites and then, very
specifically, how the company is to be run.
Although running our group generates someadministration, it does impose a discipline andstructure which are in the public domain. A request toCompanies House in Cardiff will give access to all thefine details for anybody anxious to read them. GEO
will ensure that members have access to thesestructural details, perhaps published on a CD-ROM, as
the pages in our Quarterly are just too precious for aroutine text which is in the public domain anyway.
It may be worth noting that most major groups, forexample the RSGB, use the administrative structure of
a company limited by guarantee. Our corporate
structure allows GEO to make any day-to-day rules it
deems fit for running our organisation. In due course
these must be formulated, put to the membership andpublished. A single sheet of A4 paper should be all thatis needed for this task. Hopefully, these additional
working rules will be adopted but, in the meantime,
there is the absolute security within the existing
company legal framework.

In this Issue
In this information-packed Quarterly I hope we haveprovided something for everyone, with a wide range ofarticles from both home and overseas.
I am particularly pleased to note that my plea for
information on the absence of hurricanes in the south
Atlantic Ocean has been answered so definitively byPeter Wakelin in his article on page 45. I am also
astounded to realise that, since I wrote my piece, Earthobserving satellites have only newly imaged what isbelieved to be the first ever example of a cyclone in thatpart of the world—see the upper image on the inside
front cover.
Other offerings include a fascinating piece from Bill
Johnston of New Mexico on how he has derived a radio
horizon table for his station (page 31). This is createdas an EXCEL spreadsheet, and allows him to judge
how best to tackle one of his favourite weather satellite
activities—imaging from ultra low-elevation satellite
passes.
Taking a totally new direction, John Coppens explains
how readers who make use of the Linux operating
system can also enjoy the hobby of weather satellite
imaging; from neighbouring Brazil, Raul Teixeira of
the Ceará State Department of Meteorology has
submitted examples of the imagery produced at his
station (page 29) while Arthur Andrews returns withhis regular column.

And Finally ...
Again our thanks must go to our editor and the rest of
the management team for launching and now placing
in orbit this GEO Quarterly publication.

NOAA Satellite Predictions

GEO Symposium 2004
The Leicester symposium will be almost concurrent
with this issue of GEO Q2. If you have the time, pleasecome to Leicester. You can register on the day, atthe venue. Just turn up at the National Space Centre,
central Leicester. If not you can read about Leicester in
GEO Q3.

AMSAT-UK Colloquium
We are planning to attend AMSAT-UK's meeting in
Guildford in late July 2004. AMSAT members aremainly interested in amateur radio satellites. I havebeen a member for many years but there is an overlapof interests between AMSAT and GEO. It is hoped that
GEO will be able to offer three days of live weather
satellite reception during AMSAT's meeting and alsooffer some lectures and demonstrations within theirprogramme. The dates are July 30 to August 1, 2004.
Please see our web site for the latest details.

GEO Quarterly No 2

for the UK
With such a packed issue this quarter, we regret that
we do not have the space for a page of weather satellite
pass predictions. As most enthusiasts now generate
their own data using computer software, we hope you
will not be overly inconvenienced. But do let us know if
you have strong feelings on the matter.
For readers who do require a printed page of NOAA
pass predictions, these can be downloaded, as an
Acrobat PDF document, from the following address:
http://myweb.tiscali.co.uk/les.hamilton/predict.htm

As always, do let us know how you feel about this issue.
If there turns out to be a major demand to have thesepredictions printed in the Quarterly, we will do ourvery best to meet your needs.

www.geo-web.org.uk

Page 3

GEO Quarterly No 2Group for Earth Observation

May/June 2004

Peter Wakelin
Early Rocket Development
India’s first rockets were very modest affairs aimed atsending a small payload high into the atmosphere andwere quite incapable of attaining sufficient speed toreach orbit. The first instrumented sounding rocket
was launched from the Thumba range, nearThiruvananthapuram, in the far south of India, on
November 21, 1963.
Within 10 years, after gaining much experience inusing these simple single-stage solid-fuelled rockets,
the programme to develop a multi-stage vehicle
capable of launching a small satellite was started.
Appropriately called SLV-3 (Satellite Launch Vehicle),
the rocket stood 22 m high,weighed 17,000 kg when fully
fuelled and could put a 40 kg
payload into low Earth orbit if
launched eastwards to takeadvantage of the Earth’s
rotational speed of about 1500
km/hour at the latitude ofIndia. The first launch took
place on August 10, 1979 and,
although lift-off was successful,a jammed valve in the secondAn SLV3 rocket
pictured on its
stage control system prevented
launch-pad
the Rohini Technology Payload
reaching orbit.
The next three SLV-3 launches successfully placed
Indian-built satellites into orbit between 1980 and1983 and India became the seventh nation to launch its
own satellite after the USSR, USA, France, Japan,
China, and the UK. During this period, development of
an augmented SLV (ASLV), capable of launching a
150 kg payload, was taking place. It weighed 39,000 kg
and was almost 24 m high and the first launch attempt
was made on March 24, 1987. It was unsuccessful, as
was the second attempt some 15 months later, andboth Indian payloads, together with a German remotesensing payload on the second flight, were destroyed.
This setback resulted in a four-year gap in launches
whilst the problems were investigated and eventually
overcome. Success came on May 20, 1992 when a 107
kg payload was successfully orbited. The SLV-3 andthe ASLV were experimental vehicles intended to aid
the design and construction of a more powerful rocket
capable of launching a significant payload into the sunsynchronous orbit required for Earth observation
satellites. This orbit requires an inclination to the
Page 4eastward equatorial directionof about 98 degrees so, in thiscase, the low latitude of India is
a disadvantage as the Earth’s
rotational speed becomes ahindrance rather than a help.
The Polar Satellite Launch
Vehicle (PSLV) made its firstlaunch attempt in 1993.

Early Indian Satellites
The very first satellite was
Aryabhata, which provided
technological experience inbuilding and operating asatellite system. It was
launched by the USSR in 1979
A model of anas it would be another 15 years
ASLV3 rocket
before India could launch sucha massive (360 kg) payload. With remote sensing seen
as an important goal, the second satellite, named
Bhaskara after the 7th century Indian astronomer
Bhaskar Acharya, carried television and microwave
imagers for remote sensing experiments. It was also
launched by the USSR, as was a second very similar
spacecraft in 1981.
Four small Rohini satellites, eachwith a mass of about 35 kg, werebuilt primarily to measure theperformance of the SLV-3 vehicle
carrying them into orbit but thelast two to be launched also
incorporated simple equipment
for remote sensing studies. As
mentioned above, the first one
failed to orbit but the others weresuccessful.

A Rohini satellite

The name INSAT (Indian National Satellite) is likely
to be more familiar to readers. However, despite thename, the four in the first series (INSATs 1A, B, C andD) were neither built in India nor launched from India.
They were large, 1300 kg, 3-axis stabilised, combined
meteorological and communications satellites
purchased from the USA and launched between 1982
and 1990 into geostationary transfer orbits; 1A and 1D
by US Delta rockets, 1B by the Space Shuttle
Challenger and 1C by a European Ariane-4 rocket from
French Guiana. They then reached geostationary orbit
using their own power. INSAT 1A and 1C operated forless than two years but the other two were long-lived.

www.geo-web.org.uk

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

Indian satellite designers and builders were not idle
during the period when the INSAT 1 spacecraft werebeing purchased from, and launched by, foreign
nations. Work was proceeding steadily on theconstruction of a series of remote sensing satellites tooperate in low sun-synchronous orbits. As some ofthese would be ready for launch before India’s PSLV
was available, launch services were purchased fromthe USSR for three of the first series of IRS (Indian
Remote Sensing) satellites.

The Satish Dhawan Space Centre,
named after the late Professor Satish
Dhawan who was Chairman of ISRO
from 1972 to 1984, is situated at
Sriharikota on the east coast some
100 km north of Chennai (Madras). It
is India’s ‘Cape Canaveral’ from
where all of the nation’s satellite
launches have taken place. A second
launch pad has now been constructed.

IRS 1A and 1B were identical craft and carried two
types of camera known as Linear Self Scanning
Sensors (LISS 1 and LISS 2). LISS 1 has a spatial
resolution of 72 metres with a ground swath width of
148 km. LISS 2 comprises two separate sensors with aresolution of 36 metres mounted in such a way as toprovide a composite swath of 147 km. Both LISS 1 and
LISS 2 operate in four spectral bands covering thevisible and near infrared region. IRS 1A was launchedon a Vostok rocket from Baykonur, in Kazakhstan, on
March 17, 1988 and IRS 1B followed from the samelaunch pad in August 1991.

The Space Applications Centre wasestablished in 1972 at Ahmedabad
when several units within ISRO weremerged. As the Indian space programme is very much applicationsdriven, the bulk of development workon satellites is carried out here. The
Centre carried out early communications experiments like the Satellite
Instructional Television Experiment(SITE) and developed the payloads ofthe INSAT spacecraft (except for the
first four which were purchased fromthe USA) and all the remote sensing
satellites. In addition to developing
hardware, the Centre processes hugeamounts of data from satellites.

Further advances in satellite and launch vehicle
development took place in the 1990s and they will be
the subject of part three of this series.

ISRO Centres
The Indian Space Research Organisation wasestablished in 1969, initially within the Department ofAtomic Energy, but was transferred to the newly
formed Department of Space in June 1972. Most of theearly development work took place at Thumba but,over time as the industry expanded, centres were set
up across the entire country and many thousands ofnew, highly skilled jobs were created. A brief
description of a few of the major Centres follows.

A view of the VSCC
campusThe Vikram Sarabhai Space Centre (VSCC) is locatedin Thiruvananthapuram and is the lead centre forrocket and launch vehicle projects. Research anddevelopment activities cover avionics, aeronautics,
materials and mechanical engineering, solid
propulsion systems and propellants. All of India’s
launch vehicles were developed there. VSCC also
operates an ammonium perchlorate (oxidiser)
experimental plant at Aluva, some 250 km to thenorth.

The polarsatellite launchvehicle (PSLV)The ISRO Satellite Centre (ISAC) at Bangalore iswhere satellite’s power, control and telecommunications systems are developed and where
spacecraft assembly and testing take place.
The SLV-3 and ASLV rocket engines used solid fuelbut the Liquid Propulsion Systems Centre wasestablished at Thiruvananthapuram to develop liquidfuelled rocket motors for the PSLV and later launchvehicles. The control systems for the SLV-3 and ASLV
were also developed there. Rocket motor test facilities
are located nearby at Mahenragiri.
ISRO, over the years, established a comprehensive
network of ground stations to provide telemetry,tracking and command (TTC) support to satellite andlaunch vehicle missions. These facilities are grouped
under ISRO Telemetry, Tracking and Command
Network (ISTRAC) with its headquarters at
Bangalore. ISTRAC has TTC ground stations at
Bangalore, Lucknow, Sriharikota, Thiruvananthapuram,Port Blair (Andaman Islands), Brunei, Biak
(Indonesia), Bearslake (Russia) and Mauritius.

Acknowledgements.
I am indebted to ISRO and the National Remote
Sensing Agency for making so much information
available on their websites:www.geo-web.org.uk

http://www.isro.org
http://www.nrsa.gov.in

Page 5

GEO Quarterly No 2Group for Earth Observation

May/June 2004

The first of EUMETSAT’s Meteosat Second Generation
satellites, formerly MSG-1, finally became fully
operational as Meteosat-8 on January 29 this year
when it commenced routine operations. GEO readers
who are not yet equipped to download their own raw
Meteosat data can consult an archive of near real-time
image data from Meteosats -5, -7 and -8 at:
http://oiswww.eumetsat.org/IDDS-cgi/listImages

This web page is headed by a control panel whichallows the visitor an extensive choice of Meteosat
Images at the click of a mouse button. You can view thelatest available static and animated Meteosat WEFAXImagery. It should be noted that all images, including
those from Meteosat-8, are in the familiar 800 pixels
square WEFAX format - you do not have access tohigh-resolution MSG imagery.
Meteosat-8 images are available in four wavelengths,
0.6 µm visible, 3.9 µm IR, 6.2 µm WV and 10.8 µm IR.
All are available at 1-hour intervals, with the 10.8 µm
IR images also available at 30-minute frequency.

Images are available in all the traditional WEFAX
segments as well as full Earth disc. There is also an
option to display a coloured version of each image (nota colour composite, though. If desired, movies can bedisplayed showing the most recent frames (maximum
12 frames). Meteosat-7 provides similar options,
except that only three channels are available. Data
from Meteosat-5, located at 63°E over the Indian
Ocean, is restricted to full-Earth images at 3-hourlyintervals.

Important Note
All Meteosat images on the EUMETSAT web server
are subject to EUMETSAT copyright. If you wish toreuse these Meteosat images, for example on yourpersonal website, EUMETSAT’s copyright credit must
be shown by displaying the words ‘copyright 2004
EUMETSAT’ on each of the images you display.
All Meteosat images on this page, arecopyright © 2004 EUMETSAT
Page 6www.geo-web.org.uk

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

Peter Wakelin
Fire at Indian Rocket Plant

MTSAT 1R Launch Delayed

A major fire killed six workers at the Solid Propellant Space
Booster Plant at the Satish Dhawan Space Centre in Sriharikota
on February 23. Nine workers were nearing the conclusion of apropellant curing operation involving a segment of rocket motor
containing about 14,500 kg of a mixture comprising atomised
aluminium fuel, ammonium perchlorate oxidiser and a
polybutadiene binder. Whilst removing the lower plate of acasting assembly, the propellant caught fire and only threeworkers were able to escape from the blaze albeit with severeburns. The building was extensively damaged due to the intenseheat generated but, as a second cast-cure facility was built forsuch contingencies, the Indian Space Research Organisation do
not anticipate any significant delays to any of their programmes.

As surmised in the last issue, it has now been confirmed that thelaunch of MTSAT IR will be delayed until at least November.
This follows the failure of the last launch attempt by the H-IIA on
November 29 2003. At the time of writing (late March), efforts
are being made to recover the solid-fuelled booster rocket fromthe ocean floor. Its apparent failure to separate prevented theupper stages from reaching sufficient speed to orbit the payload.

NPOESS First Launch Delayed
The US Air Force has awarded Northrop Grumman Space andMission Systems a contract modification for a 21-month delay tothe launch of the first satellite in the next-generation National
Polar-orbiting Operational Environmental Satellite System. The
delay has been attributed to the need to match a new funding
profile and to make some engineering changes to enhancecapabilities and reduce technical risks.
The first NPOESS satellite will not now be launched until 2010at the earliest which will greatly increase the probability that thecurrent polar-orbiters together with NOAAs N and N-prime, still
to be launched, will not be able to maintain a full service until the
new craft become operational.
However, there are still four remaining DMSP (Defense
Meteorological Satellite Program) spacecraft to be launchedbetween now and 2010 but, although now operated by NOAA,
their direct-readout access is restricted. If all goes well, datafrom the first European polar-orbiting weather satellite, METOP,
should come on stream in 2006.
Monitor-E 1 Due for Launch in June
Russia's Monitor-E 1 spacecraft is one of nine small satellites tobe launched on a single Rokot launch vehicle from Plesetsk,
Russia in June into a 540 km sun-synchronous orbit. Its two
high-resolution imagers are designed for research of natural
resources and the monitoring of land usage and emergency
situations such as natural disasters within Russia. Fastresponse can be achieved by tilting the imagers thus obviating
the need to wait until the spacecraft's ground track is optimal.
The panchromatic imager has a spatial resolution of 8 metresand can scan a 94 km swath within the 730 km observing zone.
The multispectral scanner can return 20 m resolution images tothe main receiving centres and reduced resolution imagery to
the numerous, widely distributed, small receiving stations.

MTSAT - Image: Space Systems/Loral.
MTSAT 1R was built by Space Systems/Loral in the USA and isbased on SS/L's standard LS-1300 three-axis stabilised
spacecraft. It incorporates many of the state-of-the art
technologies developed for the US GOES satellites and will belocated over the equator at 140° east longitude replacing theaged and ailing GMS-5. Meanwhile, GMS-5 continues totransmit WEFAX imagery derived from nearby GOES-9.
USA May Adopt EUMETCast-style System for NPOESSThe Low Rate Data (LRD) from the next-generation NOAA
spacecraft will be broadcast at 3.88 Mbps (about six times fasterthan the current HRPT transmissions) and will require anantenna about 90 cm diameter. The High Rate Data (HRD) will
come down on 7.8 GHz at 20 Mbps requiring an accurately
steerable antenna of about 1.8 m diameter. A few GEO
Quarterly readers may find direct reception of HRD within theircapability (and budget) but most will be pleased to hear that the
Integrated Program Office, in cooperation with NOAA/NESDIS,is also investigating alternative communications capabilities
such as the rebroadcast of processed imagery and other data
via the Internet or ‘commercial’ services. The success of the
EUMETCast system will undoubtedly influence their decision.
India Signs Imaging-related Agreements
A programme of cooperation between the Indian Space
Research Organisation and the Brazilian Space Agency was
agreed and signed in New Delhi in January. The programme
envisages joint research in space and atmospheric sciences,
exchange of proposals for remote sensing applications, the. . . . . continued on page 23
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GEO Quarterly No 2Group for Earth Observation

May/June 2004

Fred van den Bosch - fred@vandenbosch.speedlinq.nl
In December 2003, I posed the question as to whether
there was a more intelligent way to use pictures fromWXtoImg in Digital Atmosphere. Then I had somee-mail discussions with Ton Lindemann of Meteo
Maarssen. His website (in Dutch) is worth a visit.
www.meteo-maarssen.8m.com

This further instalment has been developed on thebasis of these contacts. It is still a trial-and-error story,
but now in a structured way. New maps can be
developed very quickly, especially after you havegained initial experience with my techniques.

Setting up WXtoImg
Open <Options> on the WXtoImg menu-bar, and click on<Projection Options...> to display the Projection Options
input screen (figure 1). Here you must input values forthe latitude, longitude, north, south, west and eastboundaries, and scale—choose values that will give theimage area you want. Additionally, in the <Options>menu, uncheck ‘disable map overlay’—this method will
not work correctly if the overlay is absent. Finally,
move to the <Projection> menu and select‘Orthographic’.

Setting up Digital Atmosphere
Open <Map/Generate map-->Enter lat/lon> and use thehorizontal and input exactly the same longitude andlatitude values you used in WXtoImg. Next, enter thewidth and height values you wrote down earlier into
their respective fields (figure 2) then click ‘OK’ togenerate a map.
You will now have to resort to a little trial and error to
select a scale that generates more or less the same sizeof map as the WXtoImg image—precision is not soimportant at this moment. Once you have generated a
map that looks ok, save it with <Map/Save map> as a
BMP.

Now you are ready to generate your satellite image. Do
so, and write down its width and height in pixels (thiswill appear on the status line at the bottom of thescreen, just before the image is displayed). Finally,choose <Image/White background> and save the image asa BMP file (the image format must be BMP for later
importing into Digital Atmosphere).

Figure 1
The WXtoImg parameter screen
Page 8www.geo-web.org.uk

Figure 2
The Digital Atmosphere parameter screenMay/June 2004

Group for Earth Observation

GEO Quarterly No 2

Figure 5
A WXtoImg orthographic image, is created, completewith country outlines (12:18 UT pass from October 12, 2003).

Figure 6First attempt loading the image into Digital Atmosphere.
Registration between image and map is poor.

Figure 7
Following fine tuning, as explained on the opposite page,the image and map now show excellent registration

Figure 8
The WXtoImg image loaded into Digital Atmosphere,with added synoptic sea-level pressure overlay.

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GEO Quarterly No 2Group for Earth Observation

Fine-tuning

this corresponding map before loading a picture with adifferent layout from WXtoImg.
The dimensions of the map can be changed bymodifying the ‘width’ parameter in WXtoImg. Always
make sure that the width and height in Digital
Atmosphere have the same values as in WXtoImg.

Repeat the following steps until both maps fits exactly.
1. Choose <Map/Load map> from the Digital
Atmosphere menu-bar and read in the WXtoImg
image.
2. Choose <Map/Add basemap> to project the DA-map
over the image. At this stage, it is unlikely tomatch correctly.

Below are two examples of parameter sets I have founduseful. The first one gives an image of Europe

Wxtoimg
Lat

Lon

N

May/June 2004

Digital Atmosphere

S

W

E

Width

Lat

Lon

Scale Width Height

1

55

5

75

35

-25

35

800

55.73

4.95

3250

800

696

2

55

26

61

47

-10

15

600

54.18

25

1167

600

515

Figure 4 - Samples of typical parameter sets following fine tuning

Now we must try to make the DA-map fit by making
changes in the <Map/Generate map/Enter lat/lon.> window(figure 2).
3. Make small changes to the Latitude field to movethe map in vertical direction
4. Making changes to the Longitude field will movethe map horizontally.
5. Adjust the Scale factor for overall resizing of themap.
6. Make further small changes as necessary by
repeating steps 3, 4 and 5. After clicking ‘OK’,
Digital Atmosphere will generate a new map
7. Repeat step 1, because only after step 2 can you
judge the result
It can happen that meridians do not fit exactly on toeach other. In this case, you can try rotating the image
in WXtoImg by changing the ‘reference longitude’.

including Iceland, the second Holland and England(figure 4).
Figure 5 shows the morning NOAA 17 pass fromFebruary 5, 2004. Figure 6 shows this image used as a
background for Digital Atmosphere, overlain with thenoon sea-level isobars.

Software Links
Digital Atmosphere can be downloaded fromhttp://www.weathergraphics.com

The program is shareware, but remains fully
functional for a trial period of 30 days, after which
certain features, including the map drawing facility,cease to work. You have to register the program torestore these functions.
WXtoImg can be downloaded from:

Finishing Off

http://www.wxtoimg.com

Save the Digital Atmosphere map for the last time
(figure 3). This must be done because every lay-out has
its own base map and parameter-files. Always open

This program is also shareware, and though it has
many useful features, the various map projections are
only accessible within the registered version.

Interest in the first issue of the GEO Quarterly has
been world-wide, and the members of the steeringgroup have been delighted with the response to their
new venture.

•

Not only have we received numerous testimonials
regarding GEO Q1, but readers have risen
magnificently to the cause by providing more articles
then we can possibly publish in one single issue—but
do please keep these articles and images coming in.

•

GEO Q3, planned for July/August is already well underdevelopment with a number of contributions alreadyfinalised, and others in the pipeline.

Page 10•••For enthusiasts of the RQFH antenna, Rob
Hollander presents the first instalment of a twopart articles on Antenna Theory and Measurement, in which he discusses such topics asradiation patterns, sensitivity and polarisation.
Peter Wakelin continues his treatise on the IndianSpace programme
We will have an illustrated article detailing theboth the weather and space-orientated activities
of of the Callington Space Centre in Cornwall
For the mobile weather satellite enthusiast, Fred
Van den Bosch describes how he captured weather
images while on a holiday in Vietnam
There will be a full illustrated report on the GEO
Symposium held at the National Space Centre in
Leicester on May 1

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May/June 2004

Group for Earth Observation

GEO Quarterly No 2David Taylor - davidtaylor@writeme.com
I was recently lucky enough to be invited to an internal
Eumetsat event - ‘MSG Goes Operational—Wheninspiration meets dedication it deserves celebration’.
Although the satellite actually went operational on
January 29, the event itself took place on Monday,
February 9, allowing me a little more time to write myown presentation!

Alain Ratier (Director of Programme Development)
spoke about Achievements throughout commissioning,
including the various problems encountered and how
they were handled. Of course, the major issue was thefailure of the SSPA (solid state power amplifier), andthe consequent move to dissemination of data via the
Hot Bird-6 DVB system.

The format of the day was for all EUMETSAT staff toattend a common morning session, where speakers
from the organisation spoke about MSG-1 and four
members of the user community introduced topics
covering ‘How do users work with the MSG data’.
There then followed a toast by the Director-General of
EUMETSAT and a light lunch, followed by parallel
presentations in the afternoon from the four membersof the user community and further presentations on
Search and Rescue, Weather Phenomena seen from
Meteosat, and the GERB instrument. During theafternoon it was possible for staff (and presenters!) tovisit the MSG Control Centre.

Mikael Rattenborg (Director of Operations) spoke
about MSG-1 becomes Meteosat-8.

Morning Session
Tillmann Mohr’s (Director-General of EUMETSAT)
presentation was entitled ‘Looking back with pride’. He
identified three key dates for MSG-1; 1984, 1994 and2004. 1984 was when a brainstorming session in
Avignon decided the basic concept requirements for
MSG as the follow-on to the existing Meteosat
programme. June 1994 saw the final go-ahead being
given by all nations, and 2004, of course, was when
MSG-1 became operational as Meteosat-8. (Dr Mohr
has been involved with EUMETSAT since its earlydays as a spin-off from ESRO/ESA, and has written afascinating history about making EUMETSAT theorganisation we know today.)

EUMETSAT Director-General Tillmann Mohr

The four user presentations which were introduced in
the morning were from Herve Roquet (Meteo France),
Wolfgang Benesch (Deutscher Wetterdienst—German
Weather Service), Hans Rosenkrans (KNMI—RoyalDutch Weather Service), and David Taylor from
SatSignal Software. I finished my talk quoting the twoquestions I am asked most often - my own FAQs which are: ‘Is it still working?’ and ‘What is the cut-out
in the high-resolution visible channel?’Afternoon Sessions
Unfortunately, as I was involved in either giving myown presentation, interviews, or involved in meetings
during the afternoon, I never got to hear the otherspeakers. I did manage to squeeze in a quick guided
tour to the Control Centre during lunch, though!

Some Things I Learned
I was most surprised by the number of people in
EUMETSAT who seem to know me, and who obviously
follow the postings on the MSG-1 Yahoo Group! People
were keen to explain about some of the things I had
asked.
The first question concerned how you manoeuvre aspinning satellite, for example to change the orbit. As
far as I could tell, the only thrusters available wereattached to the spinning part of the satellite, so if they
were operated continuously they could not provide theunidirectional thrust required for an orbit change. The
answer is that the thrusters are not operated
continuously, but in very short bursts; for example, a
100 millisecond burst every rotation. It might take ahundred or more such bursts to get the desired
momentum change. Operating the thrusters in pairs
avoids any spin change. Clever, eh?
Many of us have experienced missing segments, andwondered if it was our system or the transmission that
was at fault. My FAQ ‘is it still working?’ triggered a

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GEO Quarterly No 2Group for Earth Observation

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The full-sized model of MSG1 outside EUMETSAT HQ

Sally Wannop at MSG-1 control

Cranes around EUMETSAT HQ block C-band reception

The Meteosat Transitional Program (MTP) control room

MSG Data Manager display on a large screen in the foyer

Cutting MSG-1’s birthday cakechance to see how EUMETSAT themselves monitor
missing segments. Wow! It’s a lot more complex than I
imagined. The flow of segments is monitored as they
are processed within EUMETSAT, as they are sent to
the link for Hot Bird-6 satellite transmission, as they
are transmitted back from Hot Bird-6 (at two Ku-bandreceiving stations), and finally, after retransmission
over the Atlantic Bird C-band link, at two C-bandreceiving stations.

Not only is the presence or absence of a segment
known, but also the exact time of each event in thesegment file’s progress. Somewhat amusingly, at the
moment, EUMETSAT cannot monitor the C-band
transmission as well as they would like because there
are some building site cranes in the way! They need tofind another location for their local C-band antenna.
I’m sure we’ve all been down that path!

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GEO Quarterly No 2

As a result of talking about missing segments, and outof-order segments, we investigated a problem that I
had observed. The thing I learned there was that thesegment system works well for ‘live’ data, generated
over a period of time as a satellite scans the Earth.
However, different problems are faced with some of thederived data and foreign satellite data. Because theentire image is generated at once, the segment files
may all have the same timestamp when they reach thepoint of transmission. Thus, instead of the
EUMETCAST system simply being able to transmit
the data in the order it is generated, it may try andtransmit all the data at the same time, resulting in ascrambled segment order. All the data is there—it’s
just not in the sequence you expected! This problem canbe solved with some fine-tuning at the sender’s end.

adjustments can be made by comparing the satellite
image with well-defined points on the ground.
However, I had always considered this as dealing witha complete scan, and matching the whole picture to amap of the Earth. Not so with Meteosat-8! Because theimage segments are transmitted in near real-time, theentire image is not available while the scan is inprogress, so the image correction must be carried out
using the predicted error rather than the as-measured
error. Presumably, after the scan, the quality ofcorrection is checked and used to make the correction
for the next scan. Well, perhaps that is obvious now but
it only became obvious to me by watching the process
at work!

Yet another thing that should have been obvious to me,
and yet only became so during my visit to the control
room, was the way the geometric correction of theimages works. Basically, the image will typically beslightly imperfect as the satellite may be tilted or offaxis compared with an ideal orbit. During the life of thesatellite, the orbit inclination may vary from a couple ofdegrees through zero up to perhaps five degrees ormore at the end of its life. By allowing some inclination,
fuel is conserved. You can correct this because the orbit
is well known (from the Kepler data) and fine

There are many people at EUMETSAT who made thisevent possible and I am very grateful for being invited
to speak. Anne Taube in particular went out of her way
to ensure that everything was ready for me and theother speakers in good time for the sessions while Sally
Wannop took time to discuss User Services with me,
including a number of issues where the differing
approach in different countries is causing someproblems. Even after a long day, Nick Coyne was happy
to chat about some of the more ‘IT’-related aspects of
the operation.

Acknowledgements

Francis BellA few months ago duty called and I was dispatched by
H.M. to the Caribbean. Of course as well as the lovely
warm climate there I love the clarity of theatmosphere. There are not many places in the world
when the setting sun just disappearing over thehorizon will give you that four second colourful ride
through the visible spectrum. Red, through green to
sapphire blue—faster than you can read this sentence.
There was another manifestation of the visible
spectrum which I noticed. It can be seen regularly inthis country also: a rainbow. Occasionally there were
showers but often with the sun still shining. With acorrect sun and rainfall angle this is the recipe for arainbow. Over a period of a few days I saw several.
Now it so happened that on February 5, 2004 there wasa full moon in the night sky. A tropical full moon isspectacular: at our UK latitudes we never see it so highin the sky. I was impressed. There was no light
pollution and a clear haze-free atmosphere. With justmoonlight the light level was bright enough to walkaround safely.

On this occasion there were still a few clouds clearlyvisible in the sky and sometimes, when they occulted
the moon, a halo developed around the moon. Of course
I have seen this before but it made me think about
rainbows again.
With the moon at thecorrect angle in the sky
and a falling shower, is it
possible to see a rainbow
with moonlight alone?
I’m sure a physicist could describe the spectral
composition of the reflected light from the moon.
However, the issue is this: given the correct alignmentof raindrops and moonlight, is a rainbow produced
under these conditions? Can you see it? Has anybody
seen one?
Responses to the editor please. As usual, here is a clue:
Don’t ask a physicist what you can see—believe youreyes.

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GEO Quarterly No 2Group for Earth Observation

May/June 2004

Article byArne van Bellea.van.belle@hccnet.nl

Translated by
Chris van Lint

Regardless of whether you are receiving weather
satellite transmissions in the 137 MHz or 1700 MHz
range, both require a co-axial cable connection between
the antenna and / or downconverter. If your Meteosat
downconverter is located indoors (or if long distances
are to be covered), low loss co-axial downlead isrequired. However, low loss co-ax is both difficult tofind and rather expensive. Not many people seem to beaware that a good alternative to this special low loss
co-ax is available for use by amateurs.

using a thicker outer sheath in order to maintain thecorrect impedance. Therefore, large diameter co-ax
usually exhibits lower loss. Nevertheless the dielectric(the insulation between the inner conductor andshielding) is also a factor in determining loss. Solidpolymer material such as transparent polythene

TheoryCo-ax is available in different impedances; the mostoften used types being 50 ohm and 75 ohm. The
impedance is determined by the spatial relationshipbetween the inner diameter of the shield and thediameter of the inner conductor.
Radio amateurs use 50 ohm, whilst for cable andsatellite television, 75 ohm is used. There is a goodreason for this: a 75 ohm cable with the same outer
diameter exhibits lower loss compared with 50 ohm
co-ax. However, radio amateurs at times pushhundreds of watts through the co-ax to their antenna,
but 75 ohm is not suitable for this purpose as it causes
a mismatch which can damage the transmitter. Since
we are not using our co-ax for transmission, it would bebetter to choose an impedance which causes minimalloss and this is 75 ohm.
Losses in co-ax may be divided into conductor losses
and dielectric losses. Conductor losses are due to thefact that a finite resistance occurs over long lengths(several ohm per 100 metres). This is particularly
important for the inner conductor. A thicker innerconductor provides less resistance but necessitates

Figure 1 - Satellite TV co-axial cable

exhibits higher loss as compared to air. As it is notpossible to keep the inner conductor centred using air
alone, a dielectric containing air pockets or a foamed
polymer is present in low loss co-ax.
In addition to loss, the shielding efficiency is also
important. If it is too low, the signal will leak to theoutside or, worse still, interfering signals could
penetrate to the inner conductor. A solid copper outer
sheath would prevent entry of just about anything but
would make the co-ax very inflexible and expensive.
Consequently, a combination of copper or aluminium
foil with braided copper wire is used, and provides
much better shielding than braided copper alone(figure 1).

Table 1 - Comparisons between different types of co-axial cable
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Group for Earth Observation

Practice
With the emergence of TV satellites, low loss 75 ohm
TV co-ax (which can be used up to 2200 MHz) is nolonger expensive. Well-known brands are Belden
H125, Wisi MK90A and Hirschmann Koka 799. Goodlow loss TV co-ax has an outer diameter of between
6 mm and 7 mm, a copper inner conductor, white foam
dielectric, aluminium foil and a tinned copper braid.
The plastic outer cover is either white or black.
Beware! Cable with a green outer cover is undergroundcable, which is not UV resistant.
Since TV co-ax has non-standard dimensions, common
BNC or N-connectors can no longer be used. However
F-connectors are available for this type of co-ax but
these are of lower quality and result in somewhat
higher losses. This should not pose a problem as longas they are used following the first preamplifier /downconverter or at 137 MHz. Don’t use F connectors
between the antenna and the preamplifier /downconverter on 1700 MHz!

GEO Quarterly No 2

sharp knife whilst bending the cable slightly until the
cut tears open. Straighten the braid and fold it backover the outer sheath but leave the aluminium foil
around the dielectric.
Now cut the foil and dielectric all round at about 9 mm,
leaving 3 mm. If necessary smooth the foil over the
dielectric. Next screw the F connector on to the cable.
Continue turning the connector until the dielectric(covered with foil) is clamped against the conical part,
inside the connector. This causes the inner conductor
to be centred and creates a good contact between the
foil and the connector barrel. Never turn it so far as tocause the dielectric to protrude at the screw-on side of
the connector opening!
If the screwing-on process proves to be difficult, a bit of

Figure 2 -Crimping pliers and inset tool

At 137 MHz, TV co-ax may be connected directly to theantenna with F connectors. Although a minor
mismatch (from 50 to 75 ohm) will result, in practicethis seldom causes problems. An advantage ofF connectors is that they are cheap and can be fittedwith ease. There are two versions; the screw-on type
and the crimp type. Both have to fit properly on to the
TV-co-ax. Various diameters of co-ax and connectors
are available commercially and care should be taken to
ensure that the correct connector is used! For the crimp
version an appropriate inset tool and crimping pliers
are required (figure 2). The inset tool can also be used
for the screw version. Screw the F connector on to theinset tool and fasten with an 11 mm spanner. It is now
easier to screw the connector on to the co-ax.

Figure 3 - Wiring up an F connector

Vaseline may be applied to the outer sheath. Do notturn too far, as this may cause the foil to tearinternally. Finally cut the inner conductor if it
protrudes more than 4 mm outside the connector nut.
A minor disadvantage of F connectors is that, in orderto ensure a lasting connection, they have to be fastenedwith a 11 mm spanner. This is because the F-connector
does not have any spring contacts like BNC or

If you are using screw connectors I would advise that,after screwing on the connector, a short length ofshrink tubing is applied over the connector barrel andco-ax to prevent both entry of water and loosening of
the connector.
Carefully remove the outer insulation over a length ofapprox. 12 mm without cutting into the braid or foil. To
facilitate this, carefully cut the outer shield with awww.geo-web.org.uk

Figure 4 - Various connector types

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GEO Quarterly No 2Group for Earth Observation

May/June 2004

N-connectors. Take care however not to apply
excessive force and over-fasten!

these versions are difficult to remove.

Good adapters are available which can interconnect F,
BNC or N connectors, allowing the cable to beconnected to existing equipment. But if you build yourown equipment, it is of course better to fit them with
F connectors in the first place!

Good satellite-TV co-ax is not only cheaper, but also
results in lower loss, when compared with Aircell or
RG213. Because we are not transmitting, the minor
mismatch from 50 to 75 ohm seldom presents a
problem. If TV co-ax is used between a preamplifier
and the LNC 1700 Meteosat downconverter, thismismatch can be mitigated to a large extent bycarefully adjusting the first trimmer in the LNC for
maximum signal.

Unfortunately Teflon is seldom used in F connectors
which makes them difficult to solder without melting
the insulation. But there is a simple way to achieve agood soldered connection. You need an F connector(crimp or screw type) which is drilled out with a 7 mm
or 8 mm drill until the nut can be removed. This nut isnow soldered on to the tin case, centred on the 4 mm

Conclusion

When using a single stage preamplifier, either as anintegral part of the antenna (active feed), or one
connected directly to the antenna, TV co-ax can be usedsuccessfully over distances of up to 20 or 30 metresfrom your Meteosat downconverter. When receiving
APT on 137 MHz, a cable run of up to 100 metres
between a masthead preamplifier and the receiver caneasily be achieved.
TV / Satellite shops often offer a variety of brands ofco-ax at reasonable prices. If a type is identified as‘digital’ satellite TV co-ax, a low loss and better degreeof isolation is indicated compared with cheaper
varieties. This type is excellent for use at 1700 MHz.
(Ask for Belden H125, Wisi MK90A or Hirschmann
Koka799). The cheaper varieties (e.g. CX5S or otherunbranded types) are also suitable for 137 MHz.

Figure 5 - Lock-nutting the F connector in position

hole in the tin. For the inner conductor, a small lengthof 1 mm silvered copper wire is soldered to the PCB
track to which the connector is to be fitted.
Allow about 2 mm of the inner conductor to protrude
outside the soldered-on nut. Next take an F couplingbarrel and screw it into the nut, over the innerconductor. With an additional nut (some pot meternuts also fit), the F barrel can be lock-nutted in place.
You now have a good connection which may bereplaced later if something goes wrong unexpectedly(damaged screw thread or moisture in the connector).
To waterproof F connectors is not really difficult.
Rubber covers are available which fit snugly over the
TV co-ax and the F connectors. If the cover is coatedwith Vaseline on both sides, a good waterproof
connection, which can easily beremoved, is obtained. Ensure thatthe front of the cover seals aroundthe hexagonal nut or the surfaceof the case.

One Final Hint
I always wind some red adhesive tape around theshrink tubing and the co-ax to differentiate myantenna downleads from the multitude of other cables(see figure 4). Whenever a thunderstorm threatens, I
always remove all red-labelled cables!

New Download Address for
WXSAT Software
Shortly before GEO Quarterly No 1 was printed, major
reconstruction work by Marius Rensen on the HF-FAX
site resulted in a change of address for downloading
the popular WXSAT satellite decoding software.
GEO readers trying to achieve this using the address
published on page 44 of our Launch Issue would havebeen disappointed.

Figure 6
Rubber cover
It is also possible to buy more
expensive waterproofing covers
which click around the connector; these are filled witha type of gel which provides waterproofing. However

Page 16

The new address for WXSAT is:
http://www.hffax.de/html/hauptteil_wxsat.htm

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Hartmut Schaksmeier from Remscheid, Germany captured
this NOAA-17 APT image showing northern Scotland blanketedin snow on February 29 this year. The image was processedusing the MSA enhancement in Craig Anderson’s WXtoImg.

GEO Quarterly No 2

Gerry Berg from Wilnsdorf, Germany acquired this NOAA-17
image of stormy central Europe on February 21, 2004. This
MSA + precipitation image created with WXtoImg clearly showsthe extent of precipitation. (DK1RR@aol.com)

This image presages the end of the ‘Big Freeze’ that gripped the UK in late February. A composite of two NOAA 17 HRPT passes
processed in ‘vegetation’ mode using David Taylor’s HRPT Reader, followed by remapping using Groundmap, the image shows theadvance of an Atlantic depression while northern Scotland and eastern England remain blanketed under snow.
Image credit: NOAA Satellite Active Archive (SAA) at http://www.saa.noaa.gov/
www.geo-web.org.uk-

Processing: Les Hamilton
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GEO Quarterly No 2Group for Earth Observation

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John Tellick
Meteosat-8 became the 0° operational Meteosat
satellite in January 2004. Had things gone to plan,logistics and reception of this satellite would have beenquite different. At the end of 2003, Meteosat-7 would
have been stationed at 10°W to continue WEFAX andHRI (PDUS) dissemination till the end of 2005 (whichit continues to do from 0°) while Meteosat-8 would
have been at the 0° location transmitting HRIT and
LRIT on 1695.15 MHz and 1691.0 MHz respectively:
reception of this satellite would have been very
different to the situation we have today.
We would have been using our familiar prime-focus
dishes with ‘coffee can’ feed-horns and the
EUMETSAT recommended dish sizes of 2.4 m for
HRIT and 1.8 m for LRIT for reception of MSG
satellites! Apart from that, receivers—well the Viterbi
and Reed-Solomon signal processing part—would havebeen complex and very costly. I think it safe to say
that, under those constraints, nobody would now be
downloading HRIT and very few LRIT.

cable and have longer cable runs between dish andreceiver, and did not require an LNA.
The early days of 10/11GHz satellite TV also usedprime-focus dishes and I still have both my 1.8 m and
2 m dishes though they are now in retirement, hidden
at the end of the garden. Satellite ERPs were quite low
in the early days and front ends ‘noisy’ compared withtoday’s electronics, hence large dishes were required.
Higher powered Astra satellites changed all that anddish sizes came down; nowadays most people use offset
dishes—which get even smaller with increasing
satellite ERPs.

How Things Have Changed
Owing to problems with MSG-1’s SSPAs (detailed in
GEO Quarterly No 1 and on our website), EUMETCast
was born and a new method of meteorological data
distribution has evolved in Europe. Will the rest of theworld catch up and adopt this system? EUMETCast,using the proven (domestic) satellite TV DVB
standard, has proved in a short time to be robust,
flexible, very expandable and allows selective
encryption.
Currently EUMETCast is disseminating HRIT, LRIT
(including foreign satellite data), Meteosat-7 data,
Meteosat-5 data, ATOVS data, RSS data, ‘Met.
products’ and DWDSAT. Other services will be addedin the future including data from MetOp-1, Europe’s
new polar orbiting meteorological satellite due forlaunch late 2005. All this can be received (in Europe)on cheap widely available domestic satellite TV
hardware. Plus, of course, the Tellicast reception
software, a USB dongle and display software (seepages 7-9 of GEO Quarterly 1) and a well specified
computer.

A Brief Guide to the Front End
Users of Meteosat-7 WEFAX will be familiar withprime-focus dishes with a ‘coffee can’ feed-horn andsome with offset dishes and active feeds. Both systems(mostly) will use a two channel downconverter tochange the 1.69 GHz signals to 137.5 MHz. This gave
three advantages: you could use your polar orbiting
APT receiver to receive Meteosat, use much cheaper
Page 18

The old and the new
On the left, the 1-m Meteosat-7, 1.69 GHz dish with 'coffee can'feed horn and to its right the 85 cm offset dish with LNBs forEutelsat EUMETCast (at 13°E) and Astra (at 19.2°E).

The Mystery of the Offset Dish?
An offset dish can be thought of as a top segment cut
from a prime-focus dish, with its reception device
attached. It is taller than it is broad with its reception
device situated near the bottom of the dish andadjusted to point up into the dish. This has threeadvantages; the dish is shallower in profile, less‘angled up’ in an elevation sense while the reception
device does not sit in the signal path and partially
block the signal as in the case of a prime-focus dish.

The Low Noise Block (LNB) Downconverter
This ‘collects’ the 10/11/12 GHz signal at the focal pointof the dish, amplifies it and downconverts it to a morepractical frequency (IF) to send over cheaper cable(compared to what would otherwise be required) to thereceiver.
In the early days the Ku ‘satellite TV band’ was fairly
narrow—10.95 to 11.75 GHz if my memory serves me
correctly, though not all of it was used. The Low Noisewww.geo-web.org.uk

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

After a few years satellite capacity was increased
owing to the number of broadcasters requiring
channels and this led to an ‘enhanced’ band byextending downwards from 10.95 GHz to 10.70 GHz. A
new enhanced receiver or a frequency changer was
required to deal with the widened downconverted IF
signal. Finally the band was extended to what we use
today 10.7 – 12.75 GHz.

Prime focus dish feed horns
Left, Ku-band scalar feed horn on magnetic 'polarotor'
Rear, Ku-band feed assembly from my original 1.8 m dishRight, Ku-band scalar feed horn on early LNB
Centre, C-band feed horn [with 'polariser slab'] for comparison

Converters (LNCs) used in those days had a reasonablegain but were noisy and very expensive. My first Kuband LNC in 1985 was an Avantek LNC with 1.5 dBnoise and cost something like £1,500 alone!
Also, in those days LNCs were single polarity. Tochange the polarity you required a polarotor which
could be either an electro-mechanically adjustableprobe or a magnetic polarisation changer called a
Ferotor or an orthomode transducer – 'wave-guide
splitter', feeding two LNCs for vertical and horizontal.
Otherwise you had to go to the dish and turn the LNC
by hand. LNCs also required a Ku-band scalar feedhorn attached to the LNC wave-guide.
The feed-horn is important since it collects the signal
and directs it to the LNC/B probe. It must ‘see’ thewhole dish otherwise the signal will be attenuated, but
it should not ‘see’ outside the dish as it will then pickup noise from the sky or reflected signals from nearby
walls etc.
Feed horns are specific to the type of dish in use.
Modern LNBs designed for offset dish reception don’t,
I believe, work as well with a prime focus dish as an
LNB with a scalar feed-horn designed for prime-focus
dish reception. The satellite TV band was later
extended with an ‘upper Ku-band’, a DBS band for
EUTELSAT and Intelsat satellites and the ‘Telecom
band’ for French satellites.
This included the region of 11.75–12.75 GHz which
required yet another LNC with a different frequency
local oscillator (10.75 GHz). French Telecom satellites
used circular polarisation instead of linear.
When Astra began their service, satellite TV went
‘domestic DTH’ as opposed to having been a feed forthe cable-TV providers which enthusiasts had been
receiving. That saw the introduction of the voltage
switched polarity LNB; two polarities from one, fixed,
LNB. In addition, the feed-horn was incorporated into
the LNB structure and offset dishes became the norm.
The feed-horn is tailored for use with offset dishes
regarding the above ‘what it sees’ requirements.

This brought problems because you could not convert
the whole new wider band with a single local oscillator:
you now needed two, as well as means of switching
between them, as well as switching the signal polarity.
Voltage switching was already in use for changing
polarisation and Astra decided to use a 22 kHz tone toswitch the local oscillators. This works well and does
not interfere with the signal in the way that voltage
polarisation switching does. The Universal LNB wasborn and, owing to digital signal transmission (as wellas the ‘old’ analogue), these new LNBs had to exhibit
lower phase noise—the noise generated by the local
oscillator—than previous LNBs.
So, your modern LNB covers the band from 10.70 to
12.75 GHz, incorporates a feed-horn, has high gain
(55 dB is typical), low noise (0.6 dB typical), low phasenoise (is digital signal capable), has two tone switchedlocal oscillators— 9.75 GHz without 22 kHz tone and10.60 GHz with 22 kHz tone and can switch between
vertical (~13 V) and horizontal (~18 V) polarised
signals—all controlled automatically from yourreceiver. Also the LOs must have very little drift frombeing frozen in winter to being baked in summer
sunshine. And all this for £15 odd. Compared with myoriginal professional LNC cost of £1,500 I think that isquite remarkable. Add to that an 85 cm offset dish foraround £50, a TechniSat SkyStar DVB receiver card
for around £45 and software at around £100, then, fora total of £210 – 230 (plus a reasonable computer, ofcourse) you have yourself a state-of-the-art
EUMETCast HRIT/LRIT receiver.
Who would have thought it just 18 months ago?

Various LNBs
2nd from left, Avantek single LO, single polarity ‘lower band’(1985). Far left, Chaparral Wide-band (10.7 to 12.75 GHz)
2 x LO, single polarity (1994). Note both have WR-75 flanges(slots) for connection to a wave-guide (to the right) for
connection to scalar feed horn. 3rd from left (black) an early
Astra Cambridge Juno 2 FSS LNB with voltage switched V/Hpolarity single LO. The rest are modern day LNB's.

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Image: Copyright © EUMETSAT 2004

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

In the early morning of March 7
2004, category-5 tropical cyclone
Gafilo, hit the northeastern coast ofMadagascar. The most devastating
Indian Ocean storm for at least 10
years, Gafilo ripped across theisland republic not once, but twice.
According to a UN estimate, thismajor catastrophe left as many as
700 000 victims in its wake,
including 74 fatalities and 177
missing; as many as 100 000 wererendered homeless. Damage to
agriculture raised the spectre ofwidespread food shortages andmalnutrition among children.
Gafilo made landfall near the cityof Antalaha in the northeasternpart of the island on March 7,
crossing northern Madagascar
before entering the Mozambique
Channel the following day. There,
the storm gained strength thenbacktracked and returned to hit thesouthwest of the island.
The high-resolution Meteosat-5
image image on the facing page,
was provided by David Taylor andshows Gafilo on March 6, the day
before it made landfall near thenorth-east city of Antalaha.
The image was downloaded via the
Meteosat-8 link at 12:30 UT on
March 6, 2004 then processed infalse colour using Geosatsignal4.
The town of Antalaha was almost
entirely destroyed by winds of up to
up to 225 kilometres per hour.
Several deaths and injuries wererecorded as the torrential delugeand high winds destroyed 95% ofbuildings in the region leaving an
estimated 55,000 inhabitants
without shelter.
Gafilo continued to cut a swathea close-up look at Cyclone Gafilo from the MODIS instrument aboard NASA’s Terrasatellite on March 6, 2004. At the time this image was taken, Gafilo had sustained windsof approximately 80 mph with gusts to 115 mph.
Image: Jeff Schmaltz,MODIS Land Rapid Response Team, NASA GSFC.

across the northern part ofMadagascar as winds exceeding
200 kph—with some gusts reported
in excess of 300 kph—devastatedthe entire region, destroying
buildings, uprooting trees andflooding towns before sweeping
back out to sea.
Further loss of life was incurred
when the ferry Samson foundered
en route between Anjouan island in
www.geo-web.org.uk

the the Comoros group andMadagascar. All but two of the 115
passengers and crew aboard
perished in the mountainous seas.
By the time Gafilo made its second
pass from the southwest, its winds
had abated to 150 kph and caused
little further damage or casualties.
Finally, on March 11, Gafilo was
downgraded to a moderate storm as
it departed Madagascar.
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Arthur Andrews VK2 AAE - andrews@hwy.com.au
Well, by all accounts the first issue of the GEO
Quarterly was a great success judging by the feedback
received by the GEO team. My thanks to the readers
who contacted me and said they enjoyed my article;
such feedback makes it all worthwhile.
I would be the first one to admit that my knowledge of
meteorology is very basic and my interpretation of
weather events as seen by the satellites is very
amateurish to say the least. A few years ago I wrote anarticle in another publication, which contained asatellite image I had captured in which I identified,
what I thought was a tornado. I was later contacted bya retired meteorologist who thoroughly explained what
the phenomenon I had observed actually was. It
appears I have erred again, as Brian, an officer in the
USAF Weather Agency, disagrees that myinterpretation of the image shown in GEO Q1, Fig 4,
Page 32, is a thunderstorm. He thinks that it is a good
example of an area of marine stratus. He no doubt iscorrect: the only reason I thought it was athunderstorm was the apparent thunderheads poking
up through the cloud. I have a lot to learn and welcome
any correction where I have made the wrong
interpretation. Thanks Brian.

Figure 1 - Tropical Cyclone Grace off the Queensland coast

Our Tropical Cyclones have been fairly late this year
and as I write TC Fay is about to cross the west coast
just above Port Hedland. She is rated Category 4,
which means she comes under the ‘severe’ heading,with destructive winds and torrential rainfall. Luckily,
if she continues on her present course, she will passover a sparsely populated area. Unfortunately she is
too far west for me to get any HRPT images. TC Graceapproached the east coast a few days earlier but did
not actually make landfall, but bounced back into the
Pacific and headed south east. However she caused
widespread flooding in northern Queensland and very
high seas down as far as the New South Wales easternseaboard. I wonder if it is coincidence that the female
variety of cyclones tend to be more destructive than
Page 22

their male counterparts. Figure 1 is a NOAA 17,
channel-1, image of TC Grace as she moved away fromthe Queensland coast. The island of Noumea can beseen at the top right and at the extreme top right is aninteresting weather feature looking something like a
Catherine Wheel. However I will not hazard a guess as
to what it is.

Figure 2 - Bushfire smoke

It is not often that I can look at an event occurring on
the ground and also see it on a satellite image. Where
we live, which is near heavily wooded ranges, we arealways on the lookout for bushfires, especially at the
moment because of the drought. It was with sometrepidation that one afternoon we saw very thick cloudof smoke from a bushfire which was only about 25 km
away and which covered a few kilometres in area
(figure 2). As the smoke
was so dense andwidespread I wondered if
it could be seen fromspace. NOAA-16 was due
to make an almost
overhead pass and I
hoped it would behave
itself, as the previous
Figure 3 - Smoke plumepass imagery had beenuseless. Obviously knowing that I required a good pass
the satellite behaved impeccably and the imagery was
perfect. Sure enough the smoke could clearly been
seen. Figure 3 is a much magnified portion of achannel-1 image fromNOAA-16. Smoke can beseen billowing from thedark area, which are theheavily wooded ranges.
To be absolutely surethat it was not cloud I
looked at the channel-3A
IR image of the samepass and saw that the
Figure 4 - Hot-spot
hot spot of the fire

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May/June 2004

Group for Earth Observation

GEO Quarterly No 2

showed up clearly (figure 4). This fire was soon brought
under control by the local volunteer bushfire brigades
and damage was minimal.
Now for a bit of trivia. One morning whilst I was
waiting for the NOAA17 morning pass I noticed onDavid Taylor’s WXtrack tracking programme that thesatellite was on a collision course with the moon andwas rather interested to see how the tracking screen
would handle it. On arrival at the moon the satellite
completely disappeared under it and emerged a few
seconds later on the other side. Intrigued, I conducteda couple of experiments and found that the LEOs
passed under the geostationary satellites whilst thesun and moon passed over them, as of course theyshould. I wonder if the ISS passes under the orbiting
weather satellites as it is in a much lower orbit.
Knowing David’s attention to detail, I would bet it does.
A couple of weeks ago I was sent a 1.2 m centre-focus
dish for testing and appraisal. The dish, which is ofChinese manufacture, is collapsible and can be used ineither a fixed or portable situation. It consists of 6 lightmetal ‘petals’, two rounded centre plates and a roundmetal cradle. It takes one person less than half an hour
to assemble or disassemble which makes it ideal forfieldwork. Excellent images were received from the
HRPT and CHRPT satellites using this dish. I suppose
it would have to be good though, as the Chinese havehundreds of years practice making woks!
I mentioned last issue that I was interested in findingout how hot it got at the dish during summers.
Temperatures appear to be between 15 to 20°C higher
than the shade temperature on hot cloudless summerdays. On our hottest day this summer, with a shadetemperature of 42.2°C, Hazel’s oven thermometer
mounted by the LNA at the dish measured 63°C.
Following heavy rains in Queensland back in January,
flood-water has been making its way slowly inland andhas started to fill Lake Eyre, the first time for four
years. The first explorers and settlers thought that the

Earth Imaging News. . . . . continued from page 7
launch of a Brazilian micro-satellite for atmospheric studies by
India and the establishment of a ground station in Brazil forreceiving remote sensing data from ISRO's RESOURCESAT 1.
In the same week, Antrix Corporation of India's Department ofSpace signed an agreement with Space Imaging, USA which
gives Space Imaging rights to sell data from RESOURCESAT 1,
and the forthcoming CARTOSAT 1, worldwide. Space Imaging
have been accessing the older Indian satellites IRS 1C and 1D
for several years.

Figure 5 - NOAA-16 channel-3 IR showing Lake Eyre

large salt pan lake was always dry but, every now andagain, following good rains in Queensland and theLake Eyre basin, the lake will begin to fill, but notoften to full capacity—which is a pretty rareoccurrence. The Lake Eyre Basin, which in the main isarid, or semi arid, covers an area of 1.2 million square
kilometres, about twice the size of Texas in the USA.
The Lake is 9690 square kilometres in area and is 15
metres below sea level. Figure 5 is a NOAA-16
channel-3 image of Lake Eyre received on March 27.
The water flowing into the lake is white. A large
volume of water can be seen at the top right, partiallycovered by speckled cloud, and the two rivers feeding
the lake can also be seen. The grey areas of the lake are
the salt flats, not yet covered by water.
Last Sunday saw the end of our stupid daylight saving
and our time zones are back to normal, thank goodness.
Autumn has come and at last our temperatures are
beginning to fall after a very torrid summer. Althoughsome parts of Australia have had good rains, we arestill in drought and received only 13 mm for the wholeof March.
Cheers for now,
ArthurMaldive Islands and for setting up a Remote Sensing Unit in theMaldives. The National Remote Sensing Agency in Hyderabad
will execute the project which will involve the creation of
medium-scale maps of the entire archipelago and large-scale
maps of selected regions.

GEO Membership Form
If you have colleagues who would like to join GEOm
and receive four Quarterly Magazines each year,
please let them know that Membership Forms canbe downloaded from our website at:India has also agreed to undertake the task of providing satellite
imaging and aerial services for creating digital mapping of the
www.geo-web.org.uk

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GEO Quarterly No 2Group for Earth Observation

May/June 2004

NASA Earth Observatory News
http://earthobservatory.nasa.gov/Newsroom/NewImages/

In the Southern Atlantic Ocean some 845 km east ofSouth Georgia Island lies an arc of eleven volcanicislands extends roughly 400 km from north to south.
These are the South Sandwich Islands, whose volcanic
peaks stand on the Earth’s South Sandwich Plate,which is moving eastward at the stately pace of 7 cm
per year.

Notice how the size of the waves, as well as the angle
they form coming off the islands, correlates with theheight of the islands. For example, the peak on
Zavodovski, the northernmost of the islands, stands at
551 m, while that on Visokoi, the island just south of it,
is 1,005 m tall. The taller Visokoi peak produces a more

As it encounters theSouth American Plate,the South Sandwich
Plate is forced to passunderneath, hence theformation of the South
Sandwich Islands lessthan 5 million years ago.
The islands’ peaks range
in between 550 metresand 1,100 metres inelevation and stand in
about 2,600 metres ofwater.
As is apparent in thisimage, the islands aretall enough to disrupt
the cloud forming andflowing around them.
Most of this scene isdominated by a large
formation of low-levelstratiform clouds thatappears to be flowing ina southeasterly direction(from upper left to lower
right).
However, appearances
are deceiving, as thewake patterns extending
due eastward from each island suggest that the air
mass is moving to the east. Alternatively, it is possiblethat there are two air masses moving in slightly
different directions—a lower wind pattern moving due
east with a slightly higher wind pattern moving
southeast.

substantial wake pattern. Also notice how the wakes
produced by the islands are fanning out and forminginterference patterns where they meet one another.

The clouds in the upper right-hand corner of this scene
are higher level cirrus and altocumulus. You can see
where they are casting shadows on the lower levelstratiform cloud deck in several places.

Image courtesy Jacques Descloitres,
MODIS Land Rapid Response Team at NASA GSFC

Page 24

This scene was acquired by the Moderate Resolution
Imaging Spectroradiometer (MODIS), flying aboard
NASA’s Aqua satellite, on January 27, 2004.

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Group for Earth Observation

GEO Quarterly No 2

Francis BellThe issues I wish to discuss relate to carbon dioxide
gas in the atmosphere and to global warming. The twoissues are intertwined through misunderstanding andmisinformation. I offer my perspective on both issues.
I don’t think anybody who lives in the UK and has any
interest in our planet and its weather/climate pattern
can doubt that we are experiencing global warming.
Last summer the highest UK temperature ever wasrecorded. Mild winters and warm moist summers.
Actually, I love it. I do not need a statistician or
meteorologist to tell me our climate is changing. I justwalk out into the garden or look at my heating bill.
However, I sincerely doubt the capacity of humans to
influence the underlying forces responsible for thesechanges: the scales are so enormous. But there
remains the intellectual challenge of trying to identify
and perhaps quantify the causes and the forces
involved.
This is where I am about to expose my personalunderstandings and beliefs for public criticism because
I don’t believe for an instant that carbon dioxide in ouratmosphere, over say, the last several million years,
has had the slightest effect on global warming. Suchgas concentration changes that there have been are
trivial beyond belief compared with the thermal budgetof our planet.
There is compelling evidence establishing the fact thatcarbon dioxide has increased in Earth’s atmosphere
over the last 100 years. Instruments in a monitoring
station on Hawaii which have analysed clean air thathas blown over the Pacific Ocean for thousands ofkilometers shows this trend clearly. Over that same
100 years global warming has occurred. Wow! Herecomes the beguiling argument: ‘The increased carbon
dioxide in the atmosphere has caused the global
warming’. I assert that such an argument is rubbish
and illustrates nothing more that a spurious
correlation with no causation whatsoever. And yes, I do
know the IR absorption spectrum of carbon dioxide,and yes, it is a greenhouse gas. But this is theestablishment argument which has recently prevailed:
but it isn’t true. The effects of increased carbon dioxide
in our atmosphere must be thermally close to zero.
I accept that the above personal view is unconventional
but so were the views of Galileo. There is a substantial
scientific community promoting the causation between
the increase of carbon dioxide in the atmosphere andglobal warming. There are international and inter-governmental conferences—Helsinki, Tokyo, Buenos
Aires—where these issues are discussed. Most
commendable, but it doesn’t make the underlying
arguments more credible. The press and electronic
media must accept a burden of responsibility inpromoting this misconception. I think the media areclose to hysteria; ill judged and ill researched: theirreports are presented for the purpose of sensation andcirculation rather than information There is about asmuch substance in the average media report aboutcarbon dioxide in the atmosphere as you find in reportsof UFOs, the Bermuda Triangle and the Loch Ness
Monster. Read the stuff—it’s pitiful! In the same
paragraph, the average journalist can’t struggle
through the concepts of oxides of carbon associatedwith global warming; oxides of sulphur associated withacid rain—yes I believe this one; and free chlorine as
the cause of ozone depletion (and yes I believe that aswell). I can excuse journalists. They just want copy totheir editor and next day move on a totally different
subject. Perhaps I can excuse the politicians with theirfine qualities of intellectual manoeuvrability andelectoral adaptations. It’s harder to excuse and tolerate
the scientific community who should know better thanto promote this tenuous connection.
Okay, so how can I be so confident in my assertion thata trivial change in atmospheric carbon dioxide is notaffecting the thermal budget of our planet. There are
two points; one is about the carbon dioxide the otherconcerns global warming. Both are true but there is
only a tenuous connection between them.

The Evidence
Consider carbon dioxide. There is geological andbiological evidence which strongly indicates that 200300 million years ago the atmospheric carbon dioxidelevel may have been 10 to 100 times greater thattoday’s 0.035%. But the biology on this planet
flourished under these conditions.
The evidence comes for carbonaceous deposits such ascoal and oil which we all readily recognise but also
from deposits of limestone and chalk.
Consider coal. When the coal deposits were laid down
approximately 300 million years ago the primary
production of plants must have been awesome, locking
up huge amounts of carbon from atmospheric carbon
dioxide Nowhere in the world today, except some coldacid bogs, is net fixation of carbon taking place. You
may consider some of our major forests. I’ve been towww.geo-web.org.uk

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GEO Quarterly No 2Group for Earth Observation

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them. The canopy of a rain forest is an impressive place
to be—beautiful and diverse. There is a high standing
biomass but autotrophic production is matched byvoracious heterotrophic respiration: certainly with nonet carbon fixation. The carbon is too precious. Have alook around the world and see how much biology there
is. The answer is very little. Most of the Earth’s landmasses are either cold or arid; the oceans are marine
deserts. Marginal seas are productive and sometemperate and tropical land is productive but most of
our planet is not. Biologically our planet is dying
through lack of carbon dioxide!

Where Has all the Carbon Gone?
Where has the carbon that once supported suchvigorous life gone? Deposits of coal and oil account forsome of this depletion. But also consider the process oflocking up carbon in another form via the sea.
Microscopic marine organisms, typically coccoliths andforaminifera, have evolved with a capacity to convert
soluble bicarbonate, which results from the dissolvingof carbon dioxide in water, into the much less soluble
carbonate. This reaction, which is associated with thepresence of calcium and of the enzyme carbonic
anhydrase, produces the highly insoluble mineral
calcite (calcium carbonate). These plants use theresulting crystalline calcite as skeletal material. If
there is subsequent deposition of the skeletal material
in the remains of these plants the original carbon
dioxide is lost to the atmosphere and locked up in
marine sediments. Yes, I know these sediments can be
subducted and heated with subsequent volcanic
outgassing but this process is just too slow to keep pacewith deposition. By this mechanism carbon dioxide has
been progressively removed from our atmosphere toestablish today’s very low level. I was going to write
the word equilibrium but I’m not sure that ouratmospheric carbon dioxide is in equilibrium: it’s too
dynamic.

Three coccolith species
From top down, Discosphaera tubifera,
Emiliania huxleyi and Syracosphaera pulchra

sediments. I have had the privilege to swim along theGreat Barrier Reef in Australia. No, not all 2500
kilometers of it, but enough to be impressed. The
process is the same: dissolved bicarbonate is
crystallised with calcium as carbonate material for thecoral polyp, hence building a reef over time.

Niridea - a typical foramanifera species

Quite recently I was walking along the south coast at
Saltdean, East Sussex. The chalk cliffs there are veryclear. I looked at them and thought if there was ever an
apt metaphor it was: ‘I’m looking at the tip of theiceberg’. These carbonaceous deposits are common in
England and are distributed all over the world in what
we would call rocks, or beneath the sea as marine
Page 26

Consider some evidence from animal evolution. The
consequences for diminishing atmospheric carbon
dioxide have been profound. Deep within my lungs the
carbon dioxide level is close to 6%. My body chemistrywith its high metabolic rate keeps it this way. This isagainst a background level of carbon dioxide in the air
close to zero. I have to maintain this differential
otherwise my body chemistry will slow and I will die.
Anybody who knows the story of Apollo 13 will know
the crisis they had when coming back to the Earth. It
was not the lack of oxygen which was critical. It was
the build-up of carbon dioxide in the air they werebreathing that threatened the astronauts’ lives. We
have to maintain that 6% differential to stay alive.

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Group for Earth Observation

GEO Quarterly No 2

Chalk cliffs on the south coast of England at Saltdean, East Sussex: ‘Is this where the Earth’s carbon dioxide has gone?’
Photo: Francis bell

Evolution in Animals
Consider the evolution of some animal groups about
200 million years ago. The two supreme examples must
be birds and mammals. Up to that point animals would
have been poikilothermic, that is, maintaining atemperature dependent on their environment:
generally we describe them as cold blooded. An
increase in metabolic rate offered by decreasing carbon
dioxide levels triggered the evolutionary alternative of
being homeothermic or warm blooded. With
atmospheric carbon dioxide declining there was theopportunity for metabolic rates to increase and foranimals to be thermally independent of theirenvironment. The pulmonary to atmosphere differential increased so animals could exploit this.
Archaeopteryx, a protobird from 165 million years ago,
would have descendants running a faster metabolic
rate hence the evolution of the birds.
The same would have been true of mammals. An earlymammal such as Morganucodon about 210 million
years ago would have been able to run its bodychemistry faster, subsequently evolving into the warm
blooded fury creatures we know today. Just remember
why was this possible. Atmospheric carbon dioxide wasdiminishing because it was being locked up in marine
sediments. This analysis may also account for the
return of the Teleosts (bony fishes) to the sea with theirsubsequent evolutionary success.

Evidence from Plants
Well, if there is evidence here for the success of threeclasses of vertebrates, they are on a winning streak.
What about plants? They are losing. Less carbon
dioxide means less primary production. Today theaccess to carbon dioxide is a severe limiting factor for
most plants.
Consider some tropical monocotyledons. The two best
examples are maize and sugar cane. It’s no coincidence

that we grow these as crops, GM or not. Try driving
across Nebraska, Illinois, Georgia or Kentucky: ‘it’s
devastatingly dull’, (not my quote). Look at how muchmaize is growing. Try driving along the Pacific coast of
Queensland and look at the sugar cane fields. Yes, I
would rather do this. These plants have evolved in
desperation for access to the diminishing atmosphericcarbon dioxide. Their photochemistry, cyclic and noncyclic photo-phosphorylation is conventional but they
have evolved a chemical pathway for the subsequent
fixation of carbon which avoids the negative feedbackof some chemical pathways present in most otherplants. The net result is that under conditions wherecarbon dioxide is limiting, they do better that otherplants. And we grow them as crops!
Calculations suggest that human activity annually
vents about six billion tonnes of carbon dioxide into ouratmosphere. Yet measurements indicate the sustained
increase of atmospheric carbon dioxide is only about
half this figure. Where has the missing three billion
tonnes gone? Research, if you believe it, indicates the
Amazon rain forests are mopping it up. I might suggest
a marine sink. However, plants desperate for carbon
dioxide, growing in otherwise favourable conditions,avidly mop up the extra available carbon dioxide. Wow!
You don’t have to be a member of Mensa to work that
out; it just reinforces most of my text above. Thisplanet is desperate for extra carbon dioxide!
I have tried to argue the case that carbon dioxide in thepast has been very much higher than today’s level andthat life on the planet today is dangerously low because
carbon dioxide has been geologically sequestered.
What about the global warming?

Global Warming
Let us accept that we are experiencing global warming.
What are causes? I will not be able to answer thisquestion but I can address the issues.

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GEO Quarterly No 2Group for Earth Observation

The Earth has experienced cyclic periods of ice ages
and inter ice age warming most certainly not affectedby humans and any small influence humans may have
had on the atmosphere. My analogy here for ageological heat wave is a wave in water. Suppose asmall stone were dropped into a garden pond. Small
waves would be produced and the height of these waves
could be measured. The height of the wave is theequivalent of a thermal displacement. Now go out into
the middle of the English Channel on a very calm day
and drop the same size stone into the water. Can the
ripples it produces be observed and measured? The
answer must be yes. But what might be harder todetect in a small boat would be the gentle Atlanticswell almost imperceptibly raising and lowering theboat with a period of about 30 seconds and, more
importantly, the tidal levels would be changing theheight of the boat with a periodicity of hours. At least
20 celestial factors affect tides plus many terrestrial
factors. But we myopically look at the ripples from thestone and debate them.
There are other candidates for the causation of global
warming besides carbon dioxide. Our Earth’s internal
dynamics: convection and magnetic field changes. The
same applies to our sun. I know these are being studied
and I expect the major factors affecting the thermal
budget of the Earth will be identified, but for the time
being don’t anybody tell me the major causation of
global warming is the minute change in atmosphericcarbon dioxide. I don’t believe it.
I am not, repeat, not tolerant of indiscriminate venting

May/June 2004

of exhaust gases and particulate materials into ouratmosphere and the same applies to aqueous
discharges into our seas. I must opt for the weakanthropic argument. ‘This is my planet; I was born
here; I am well suited to the planet as it is; I have
nowhere else to live so leave the planet alone’. I have tostop short of suggesting that it would be biologicallymore interesting and dynamic to live here if the carbon
dioxide in our atmosphere was, say, ten times its
present level!
Any reader who wishes to take issue with any of theabove views is invited to put pen to paper and make a
submission to the editor.
With a suitable acknowledgment the above text is
copyright free.

A Postscript or Short Digression.
News about the planet Mars is quite rightly topical.
People interested the dynamics of the Earth arenaturally interested in our neighbourhood planet. The
life—the atmospheric and hydraulic history there—
may be the Earth’s future. Yes, there is still life on
Mars. The evidence is overwhelming. I offer an award
of a Getmapping aerial photography CD-ROM showing
Greater London to the first person who writes to me (atthe address listed on page 1) giving the transcriptionamino acid for DNA sequence CGA on Mars. A one
word answer is all that is needed. A clue is that thequestion could have been put in four ways and theanswer is the simplest in the series. I am confident that
I know the answer: even for Mars.

Measuring Evaporation.
Cedric Roberts M.B.E.
Though all of us are well aware of
rainfall and the effects that can arise if
we get either too much or too little,
many people have no real conceptionof evaporation. Yet this is vital to watersupplies, for evaporation is basicallythe apposite to rainfall. We areconstantly
losingwaterbyevaporation that is going on from allwater surfaces, from the land itself
and from vegetation.
Attempts have been made for many
years to measure evaporation anddevices now exist for doing just thisfrom water surfaces, from the surfaceof the soil and from leaves. The
method in use at meteorologicalstations is the measurement of
evaporation from water surfaces, andis generally used to give an idea of
how much water is being lost as
opposed to the amount being accrued
from rainfall. Three types of
instrument are in general use forPage 28

measuring evaporation from freewater, the evaporation tank, the Piche
evaporimeter and the Lysimeter.
It would take far too long to describe
each instrument in use, so I shalldevote my time to the main device in
use here, the Piche evaporimeter.
This consists of a graduated glass
tube marked in millimetres that has,clamped across its base, a small
circular porous paper disc of standard
size: the instrument itself is housed in
the Stevenson thermometer screen.
The disc is at the bottom when the
tube is inverted and so, as water is
evaporated from the wetted paper
surface, the water level in the tube
falls thus enabling a measurement of
evaporation to be made. Having thepaper disc at the base ensures that it
is always kept wet as long as any
water remains in the tube and thismust be regularly ‘topped up’. The
instrument is simple to use and iswww.geo-web.org.uk

relatively
inexpensive,
merelyrequiring that it is removed from theStevenson screen if any severe frost
is expected.
Readerswho
requirefurtherknowledge on the Lysimeter and theevaporation tank can find references
to these in any good Meteorologicalglossary. I have referred here only to
the Piche evaporimeter. You will havegathered from the text that the
instrument is graduated in millimetresand so evaporation is measured inthis unit also, a valuable asset sincerainfall is also measured inmillimetres. If we keep a careful checkon rainfall in mm over a period, andevaporation in mm for the same
period, we have a quick and easy ideaof whether, over that period, water isbeing gained by rainfall or lost at agreater rate by evaporation from afree water surface.

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

Raul Fritz B Teixeira from Ceará State Department of Meteorology at Funceme in northeast Brazil (www.funceme.br) sent in someexamples of the satellite images captured at his station using a TeraScan System. Reproduced above are two NOAA-16 AVHRR
images of Hurricane Isabel made at 16:15 UT on September 8, 2003. The left-hand image is the ch-1 (visible) image; to its right isthe ch-4 IR image, enhanced using a customised colour palette created with TeraScan. The coldest temperatures are in purple andcorrespond to the cirrus shield´s overcast region and also anvils and ice at the top of cumulonimbus.

True to its name, Iceland is seen covered in a white blanket of
ice and snow in this January 28, 2004 true-color image acquiredby the MODIS instrument aboard NASA’s Aqua satellite. The
uniform color hides the exact boundaries of Iceland’s four
permanent ice caps—Langjokull and Hofsjokull in the interiorwest, Myrdalsjokull on the southern coast, and Vatnajokull, thelargest of the four, which rests on top of three active volcanoes.

The heat from these volcanoes causes the underside of the ice
cap to melt, slowly building up meltwater in the volcano’s
caldera. When the meltwater spills over the lip of the caldera, it
releases a torrent of water known as a glacial melt flood.
Image courtesy Jeff Schmaltz
MODIS Land Rapid Response Team at NASA GSFC

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May/June 2004

Cedric Roberts sent us this Meteosat-8 image he downloaded on Monday, March 22 this year. It is the 15:00 UT transmission andillustrates shower activity over the UK under a NW wind. Many of these showers are wintry with snow, hail and squally conditions.

The days leading up to New Year 2003 brought contrasting extremes of weather to Scotland. On the night of December 27-28, apolar low struck, gale-force winds and drifting snow causing severe disruption to the north of the country. There followed a day anda half of the most beautiful calm sunny weather, and the images above illustrate beautifully the extent of the snow cover. The lefthand image was submitted by Ian Deans and came from the MSG-1 HRV transmission at 15:00 on December 30. The right-hand
image comes from the 13:37 UT NOAA-16 channel-1 HRPT pass the same day. But these images already presage the turmoil thatwas shortly to follow—the thick band of cloud already seen spreading north over England was the fore-runner of the worst New Yearstorm to hit Scotland in living memory. Throughout that afternoon and early evening winds whipped up to gale force, driving heavy
rain before them. In both Edinburgh and Aberdeen the traditional open-air New Year festivities were cancelled with some hundred
thousand revellers being sent home in Edinburgh and another 50 000 missing out in Aberdeen.
MSG image © EUMETSAT 2003
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May/June 2004

Group for Earth Observation

GEO Quarterly No 2

Bill Johnston, K5ZI

All satellite orbital prediction computer programs
provide this critical information. The time at which asatellite appears above the horizon for a particularpass is known as ‘rise time’ or ‘acquisition of signal’(AOS). Similarly, the time when a satellite sets is the‘set time’ or ‘loss of signal’ (LOS). Commonly available
programs for personal computers correctly predict AOS
and LOS with an accuracy of a fraction of a second.

relatively fast technique is to use a surveyor’s transit.
The instrument is first positioned on a stable tripod
and properly levelled. Then the transit is rotated inazimuth by 1-degree increments (for a coarser table
you might use 5-degree increments). The transit’s
cross-hairs are placed on the true horizon at each ofthese points and a note made of both the azimuth andelevation angles. The complete circle, then, willproduce a table of 360 data pairs with suitably fineresolution for almost any analysis you might want to
conduct.
Horizon (deg)Those of us who utilise signals from orbiting satellites
have a paramount interest in knowing when asatellite’s signals are available at a given groundlocation. This is just another way of saying that weneed to know when a satellite is above the local
horizon, since for all practical purposes the commonlyused VHF and microwave radio signals travel to andfrom satellites along a line-of-sight path.

18
13
8
3
-2

What one must keep in mind, however, is that suchprograms compute AOS and LOS based on the‘theoretical horizon,’ i.e., the horizon which would exist
if the Earth were perfectly smooth, with no hills, trees,buildings, or other obstructions to get in the way of
your antenna’s view of the sky. The elevation angle ofthe theoretical horizon is 0 degrees at all points ofazimuth. On the other hand, a nearby building mightwell protrude, say, 20 degrees of elevation above thezero-degree theoretical horizon, thereby blocking
satellite signals up to that elevation angle for thewidth of the building (which itself might cover manydegrees of azimuth).
The signal from a satellite rising behind a building will
therefore become available at a later time and at ahigher elevation angle than your computer program
predicts. By taking into account all obstructions as
seen throughout a complete circle around your antennasite, you can characterise what is termed the ‘true local
horizon,’ or, for our purposes, the ‘radio horizon.’
Having a local radio horizon table consisting of theelevation angle of the true horizon at each point of
azimuth can be quite useful in understanding why
satellite signals are sometimes not available when thecomputer program says they should be. Additionally,such a table can sometimes go a long way toward
identifying sources of interference and objects which
degrade satellite signals without completely blocking
them. Some orbital prediction programs will evenallow you to enter your horizon table data into theprogram, thereby optimizing tracking by your antenna.
There are several methods which can be used tocompile your local radio horizon table. One simple and

0

100

200

300

Azimuth (deg)Figure 1 - Horizon-table graph (Excel)

Not everyone will have access to a transit, of course,
and there are other methods which will produce
equivalent results. In my own case (although I do own
a transit) I chose to use my HRPT weather satellite
image receiving system to electronically compile ahorizon table for my own station location in southern
New Mexico. The method is exceedingly simple, albeit,
not for the impatient.
For a period of time I kept a sheet of paper next to the
HRPT antenna rotator controllers. In several columns,
lines numbered from 1 to 360 (indicating azimuth
points) provided spaces where the corresponding
observed radio horizon elevations could be pencilled in.
Each time I captured a satellite image, I simply madea note of the azimuth and elevation angles at which
AOS and LOS occurred and jotted down the elevations
at the appropriate entries on the paper. I chose todefine AOS as the point at which the decoder locked on
to the signal, and LOS as the point at which the
decoder lost lock. This eliminated the ambiguity of theshort period between detection of a measurable signalby the receiver, and the point at which the signal isstrong enough for the decoder to make sense of it.
An advantage of collecting data through actual
observation of satellite signals is that the horizon
figures arrived at are automatically ‘adjusted’ for suchfactors as refraction and reflection, neither of which
could be easily accounted for through visual sightings
with a transit. Moreover, the measurements arewww.geo-web.org.uk

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GEO Quarterly No 2Group for Earth Observation

May/June 2004

Figure 2 - The peak on the horizon at azimuth 333°

Figure 4 - This NOAA-12 pass from May 2001 gave a maximum elevation of only
0.9°, yet imaged areas almost 3000 miles from the receiving station.

Figure 3 - The mountains to the south at 204° azimuth
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Figure 5 - An enlarged detail from the same
NOAA 12 pass as Figure 4, showing Long
Island, the Hudson River Valley, and Lake
Champlain.

May/June 2004

Group for Earth Observation

specific to the radio frequencies at which theobservations are taken. In my case, all data wererecorded at the HRPT frequencies centred around
1.7 GHz. One’s own radio horizon table, of course,
should be compiled through measurements at
whatever frequency is of greatest interest.
Once I had accumulated sufficient data for my horizon,
the results were plotted as a graph as shown infigure 1. While this can be done with pencil and graphpaper, there are many computer programs which will
not only display the data in graphical form, but will
permit you to manipulate it for further analysis with aclick of the mouse. One piece of software which will dothe job, and which I use extensively, is Microsoft Excel.
However, since I wasn’t versed in Excel’s graphingcapability, I enlisted the aid of my friend Jon Haas,
KD5OHH, who set up the spreadsheet and its
accompanying graph in a matter of minutes. It isn’t
necessary to collect data for every point on the horizon,
as Excel will interpolate missing points on the graph,just as you will do manually if working with pencil andpaper. You’ll find that the horizon table has much moreutility if you collect and record data (either visually orelectronically) for at least 200 or more azimuth points,
particularly if you have a very irregular horizon.
As the graph reveals in figure 1, my station, at 5,200
feet (1,585 m) above sea level, is surrounded by
mountains on three sides but has an open horizon to
the east and southeast. The highest nearby peak,
about four and a half miles to the south-southwest, is alittle over 9,000 feet (2,750 m), and as such presents aradio horizon at that point of about 9° elevation. Other
peaks, which are no more than 7,000 feet (2,130 m)
altitude, are much closer and consequently result inradio horizons at great as 12°.
The highest point on my radio horizon happens also to
be my one and only man-made obstruction—an 11-footdiameter parabolic dish antenna intended for anotherproject—which I mounted too close to my HRPT
antenna (itself an 8-foot diameter dish). The 11-footdish obstructs the sky to an elevation of about 15°,
from roughly 278° to 295° azimuth. It’s not quite as bad
as it sounds though, as the hills behind the obstructing
dish mask the sky to an elevation of 9° already, so mypoor planning actually cost me only an additional 6° ofelevation through the width of the large dish.
In addition to the graph already referred to, I’ve
included some photographs taken from my HRPT
antenna location. Near the centre of figure 2 is a peak
about a mile away whose azimuth is 333°. The outlineof the peak is clearly seen on the graph (the verticalscale of which has been intentionally exaggerated forclarity). At the left side of the same photo is seen theedge of the 11-foot dish, which in turn shows up as thelarge ‘peak’ on the graph, between about 280 and 295
degrees azimuth. Figure 3 shows the view to the south.
Near the centre, at 204° azimuth, can be seen a pair of

GEO Quarterly No 2

adjacent peaks known locally as the Rabbit Ears.
These show up at the corresponding point on the graphas a sharp spike which drops off into a mountain passjust to the right.
Obstructions which mask the sky below 16° elevation
may seem unimportant to some readers, as manyobservers consider satellite passes below 20° elevation
to be unusable anyway. But the fact of the matter isthat for a well constructed system whose components
are in accurate adjustment, this is a prime reception
area which can extend your imaging by hundreds ofmiles. Indeed, I do most of my own imaging withsatellite passes whose maximum elevation does notexceed 15 degrees. To the east and southeast where
there are no mountains, I regularly record images fromsatellites which skim barely 2° above the horizon.
Occasionally, with the aid of refraction andtropospheric ducting, I capture images from passes
which don’t rise above the horizon at all. On theseshort passes the satellites actually skulk a degree or
two below the horizon, while the antenna sweeps thehorizon at 0° elevation.
The accompanying HRPT image, showing part of the
Maritime Provinces of Canada and the northeastern
United States (figure 4), was captured from a
NOAA-12 pass whose maximum elevation above thetheoretical horizon did not exceed 0.9° at my location.
The pass lasted only four minutes, but after processingin WinHRPT, it produced an image with exquisite
detail of areas nearly 3,000 miles (4,800 km) from mylocation. This was an ascending pass whose azimuth
began at 39° and ended at 69°. Examination of myhorizon table shows that the true horizon ranges from
1° elevation, upwards to 3°, within that arc. In otherwords, the satellite was never above the true local
horizon at any time during the pass!
With a carefully adjusted system, it is not unusual tocapture below-the-horizon images such as this one.
However, images from the vast majority of HRPT
passes conform precisely to the true physical horizon
which I’ve recorded in my radio horizon table. I nevercease to be fascinated to see the receiver’s signal
strength meter swing from zero to full scale within acouple of seconds of the time the satellite reaches theelevation angle shown in the table for thecorresponding azimuth.
The horizon table, then, serves as a planning tool forimage reception. For passes in the west and northwest,
for example, I know not to waste my time if thepredicted maximum elevation is less than 8° or so. If
the pass will rise to 10° or higher, I’m certain to receive
an excellent image for at least part of the pass,showing weather systems far out into the Pacific
Ocean. The zone between 8° and 10° maximum
elevation is adventure-land, where I’m occasionallyrewarded with glimpses of territory as far away as
Alaska.

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GEO Quarterly No 2Group for Earth Observation

To the east and southeast, where the true horizon andthe theoretical horizon are the same, I generally see
the signal pop on or off at exactly the moment thecomputer program says the elevation angle hasreached 0°. But this is also a prime area to benefit fromatmospheric refraction, which often enables one toreceive usable signals down to -0.5°, and occasionallyas far as 2° or more below the horizon.
When you consider that building a radio horizon tablethrough direct observation of satellite signals requires
watching AOS and LOS over hundreds of passes (andmany passes will duplicate what you’ve already

May/June 2004

recorded), it becomes apparent that it takes quite awhile to form a reasonably complete picture of yourlocal radio horizon. Nonetheless, I personally found thetask very enjoyable and instructive. It’s not something
you have to do every time you receive an image.
Instead, if you do it when you have the time and you
feel like it, you’ll get a great deal of satisfaction eachtime you fill in another blank spot in your table. And
the greatest enjoyment comes when you have enoughdata to begin matching it to the physical horizon, andunderstanding why satellite signals sometimes appear
and disappear in seemingly peculiar ways.

Copy Deadline for GEO Q3 - Wednesday, June 30, 2004
The support GEO has so far received from its readers has beenmagnificent; indeed, so many articles and images were received
for this issue that GEO Q3 is already well under way.
The Editor is always on the lookout for articles and images
relating to all aspects of Earth Imaging, especially:• Technical articles concerning relevant hardware• Construction projects• Weather satellite images• Reports on weather phenomena• Description of readers’ satellite imaging stations• Activities from overseas• Letters to the Editor• Problems and Queries for our experts to answer
Contributions should of course be original and, where possible,
should be submitted to the editor in electronic format (floppy
disc, CD or e-mail attachment). But we will also accept
handwritten or typed copy.

Images and Diagrams
Images can be accepted in any of the major bitmap formats, e,g,
JPG, BMP, GIF, TIFF etc. Images in both monochrome andcolour are welcomed for inclusion. Line drawings and diagrams
are also welcome in Windows metafile and postscript formats.
Please note that images and drawings must not be embedded
within the text of your article, but should be submitted as
individual files.Submission of Copy
All materials for publication should be sent to the Editor, Les
Hamilton, 8 Deeside Place, Aberdeen, AB15 7PW, Scotland.
Materials may also be sent as attachments to the following
e-mail address:
editor@geo-web.org.uk

Weather Satellites and their Frequencies
Polar Orbiting Satellites
NOAA-12
NOAA-14
NOAA-15
NOAA-16
NOAA-17Feng Yun 1C, 1D

Frequencies
APT (MHz) HRPT (MHz)137.50137.50137.62-

1698.01707.01702.51698.01707.01700.4Frequencies

Geostationary Satellites

Location

WEFAX (MHz)

USA

75°W

1691.0GOES-W

USA

135°W

1691.0

Meteosat-5

INDOEX

63°E

1691.0

Meteosat-6

Europe10°E

1691.0

Meteosat-7

Europe0°1691.0, 1694.5

Meteosat-8

Europe0°

D VB

GOES-E

Where to Download NASA 2-line Elements
Satellite tracking programs require regular updates of the NASA 2-line element sets that they use to calculate
the positions of Earth-orbiting satellites. One of the best Internet sources for these files is Celestrak at:
http://www.celestrak.com

Elements for many groups of satellites are updated daily. Particularly useful are:http://celestrak.com/NORAD/elements/weather.txt (most weather sats)
http://celestrak.com/NORAD/elements/resource.txt (Okean and Sich)
http://www.celestrak.com/NORAD/elements/stations.txt (ISS)

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May/June 2004

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GEO Quarterly No 2

John Coppens ON6JC/LW3HAZ [4] - john@jcoppens.com
WXtoImg is one of those strange programs that may atfirst frighten the casual user but offers an impressive
performance for its price (free for the limited version).
I does most of what has to be done in automated APT
reception and processing, and does it very well indeed.
Some say I’m somewhat biased (or worse) towards
Linux, but I feel that somehow this operating system
reflects part of the radio amateur spirit. Do continue
reading - there’s a Windows version for the others too!
I freely admit that software offerings for Linux are
somewhat limited, not entirely unlike the recent
problems we have faced in electronic component
procurement. But generally, programs that areavailable are of excellent quality, offer many options,and are very reliable(and free, with source code!). A
case in point is the WXtoImg [2] program, which isavailable on the Internet, both for Windows and Linux(there’s also a MacOS version but it isn’t updated as
frequently).
WXtoImg comes in two forms; the ‘standard’ version
which is free, and which is the one I’m describing
below, and the ‘professional’ version, for which a low
registration fee is required. The latter adds several
projections, some processing options, and can evenautomatically create and update web-pages with yourimages.

Installing WXtoImg
Installing WXtoImg in Linux is easy—there’s just one
executable file. Copy xwxtoimg to /usr/local/bin
where the operating system will find it, and you’re set.
(If you use Windows, then just double-click thewxinstnnnn.exe file and installation is automatic,
complete with a desktop short-cut icon.)There’s a command line version for Linux, which
permits execution of all reception and processing frombatch files (in fact, it consists of a suite of 5 commandline programs: wxtoimg, wxrec, wxmap, wxproj, andwxbatch, each of which does the task which its nameimplies).
The most recent few versions display a nag screen
which waits for 10 seconds before enabling the rest of
the program. (Personally, I do not approve of thismethod of trying to get the user to register. Still, youwill normally never stop the program, so it's not too
bad either). A stumbling block with Linux programs isthe sometimes more austere user interface. Some ofthis is noticeable in WXtoImg.

Figure 1 - Thumbnail page of recently decoded images

You can select from several options to start processing:• Select an existing audio file
• Select what’s called a ‘raw image’• Select ‘Record’Standby (waiting for a 2400 Hz carrier) and reception
take no noticeable CPU
resources and I leave themrunning all the time. Once animage has been received, ittakes the PC just a few seconds
to do the processing and to
generate the final image. A new
feature in the most recent
versions of WXtoImg is thatthey actually show the raw
satellite
image
duringreception.
Figure 6 (page 37) shows the
program after processing an
audio file (or receiving asatellite pass). Note the tabs
above the image—this is
another relatively new featureand permits you to browse
through thumbnails of yourimages (fig. 1), for example, or
to check which audio files arestill available:

Available features
Let’s have a quick look at themain menus, and discuss someof the possibilities.

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Figure 2

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GEO Quarterly No 2

File Menu
In the File menu (fig.2) there are many
options , but the most frequently used willprobably be Open Audio File..., Save Image
as... and Record.... In most cases this will bevery straightforward. Under Linux, I prefer
to use the standard GTK gmixer application, which I am more comfortablewith (I don’t like the aesthetics of
WXtoImg’s built-in mixer).
The use of most options is simple, as most of
the parameters (JPEG quality, recording
settings etc.) need only be programmed
once into the Options menu item.

The Direction Menu
The Direction item (fig.3) allows you toselect a satellite direction manually or toleave WXtoImg to do this automatically foryou.

The Satellites Menu
The Satellite menu (fig.4) permits selecting
the satellite manually. This is useful if, forsome reason, the program gets confused byvery weak signals or strange schedules, orolder passes for which WXtoImg doesn’t
have orbital data stored.

The Enhancements Menu
Interesting though, are the enhancements
you can select. I haven’t seen anotherprogram that permits so many excellent—and different—algorithms for processing
the received imagery. For example, the ‘ZA’
infrared enhancement is excellent where
intense storms develop, as the normal IR
image tends to saturate in the white clouds.
The ZA remaps the intensities and nicely
shows the storms centres. Also useful is the‘NO’ enhancement, which colours clouds
starting at -25°C or so, down to -90°C. We
had some very severe storms here in
Argentina a couple of months ago, and they
were very nicely rendered using this mode
(I even warned the local Civil Defence
authorities).
All the time, temperature at the cursor
position is available on the screen (except
for a bug, that stops the display of
temperature after saving a file—I’ve
notified the problem to the author). The
value corresponds quite well with reality.

The Options Menu
The Options menu (fig.8) is the mostcomplicated—I had never really consideredthat the actual reception of images
depended on so many factors!
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May/June 2004

Several items that are normally only used
when post-processing images, such as
despeckling, and sharpening are available.
The despeckling algorithm works fine on
removing shot-noise. I was originally very
sceptical about despeckling, after having
tried several algorithms on other programs,
but I must admit that the one implemented
in WXtoImg works very well!
Figure 3

Be careful when setting the level though.
While the default value of 2.0 works fine, I
personally prefer to use 2.5. A value of 3.0
despeckles less while a setting of 1.0 is
basically useless—it modifies cloud detailstrongly and does not really improve theimage (you can check the effects of different
despeckle settings in fig.9)
Interpolate makes a brave try tointerpolate the video (or the audio) anddouble the resolution. This succeeds insome images but in others the image justbecomes larger without any noticeable
improvement. The Noise Filter works, but,
as expected also removes some of thedetails of the image, which is reallyunavoidable, I guess...
The Illumination Compensation again
makes a brave attempt to compensate forpredictable variations of light conditions in
the images. Though some images do
improve, in extreme cases the image getstoo noisy because of the increased gain
being applied.
Active APT Satellites lets you select, as
the name implies, the satellites for which
Kepler elements have to be fetched from theWeb, and which have to be monitored.
(WXtoImg downloads the data from theCelestrak [1] website.

Figure 4

On the same menu, you can also program
the satellite’s frequency (to control a
receiver, for example), and to assign apriority in case two satellites haveoverlapping passes.
Ground Station Data is, as you would
expect, where you input your station
information (name, latitude and longitude),though the registered version has thepossibility of synchronising with the NMEA
data stream from a GPS receiver (I use theInternet to sync the PC’s clock and a
program called Chrony [3] which connects to
NTP servers, measures the PC’s crystal
frequency error and, using saved statistics,
is able to correct the clock should the
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Figure 5
Projection menuMay/June 2004

Group for Earth Observation

GEO Quarterly No 2

0

2.5

2.0

1.5

1.0

Figure 6: WXtoImg: a screenshot with the program running

Figure 9
Despeckle Options

Figure 7 - A two-pass composition of NOAA-17 multispectral analysis images

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GEO Quarterly No 2Group for Earth Observation

Internet connection drops temporarily.

The registered version offers a lot ofother projections, some of which
seem interesting, other less so.

Recording Options offers four
different methods for initiatingrecording:• Start using WEFAX start tones• Record when a 2400 Hz tone isdetected (with safeguards at the
beginning and end, the methodthat I normally use)
• Record when the sound level
rises—nice if you have asquelch implemented in yourreceiver, preferably a toneactivated squelch.
• Record when an APT satellite isoverhead. The program has its
own orbital prediction program
built-in, so it can activate thereceiver using those data. In my
particular location this system
is not very useful because I’mactually living on the slope of arather steep hill; in somedirections I have a minimum
elevation of only 25° to 30°
while in other azimuths I canactually receive the satellite till
it is under the horizon—thisdefeats the minimum elevation
setting for me. To paint it
another way: I have only
sunsets, the sun rises wellbehind the ‘mountain’.

Image

Just one final option— it really goeson and on—is Map Overlay, whicheven permits you to select how themaps are going to be overlaid on theimages, how detailed they’re going
to be and the colours and line widths
used to display boundaries, etc.

Projections
The projections menu (fig.5) is theitem that is most restricted from theregistered version, I guess. It offers
three projections:• Normal (as sent by the satellite)• Equidistantcylindrical,aprojection which I particularly
have little use for• And Eckert IV, which is a very
interesting one, as it permits
fairly easy combination of theimages from two consecutive
passes. In fact, in the registeredversion, this combination can bedone automatically.
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May/June 2004

The image menu really contains a
lot of things I’d rather leave to apaint program. But then WXtoImg
is targeted as a ‘do-it-all’ programthat does everything from reception
to publishing, so any postprocessing enhancement has toprovided too. The only two items I
ever use are the Move Map Overlay(rarely, if for some reason theInternet connection breaks down
and the map slips in the image) andeven more infrequently, the Magnify
Area option, to look at anenlargement of part of an image. It’s
often interesting to observe theEnhancement Curves though.

Help
The Help menu does just that, andquite well. It has several chapterson the different aspects of thenormal use of WXtoImg, and also
provides help for the command line
version (which might otherwise
prove rather tricky). Help also has
the tools to register the program andto enable the features unavailable(greyed-out) in the unregisteredversion. I can vouch for thedevelopment activity on the
program.
ThoughIhaven’tregistered yet (I plan to do so real
soon now). I have sent the author
details of a few problems and always
had a helpful reply.

Some Final Musings
WXtoImg is performing excellently
here. So much so I have pretty wellarchived the processing program I
wrote a few years ago. The splash
screen with the 10 seconds delay
bugs me a little, particularly as it
wasn’t there in previous versions.
On the other hand, the programruns here for weeks on end, so it
does not make me suffer too much.
As a free program, the relation
between performance and pricewould probably be acceptable, but ina Linux world where most programs
are free, performance is normallyjudged separately—and WXtoImg
scores very well indeed.
www.geo-web.org.uk

Figure 8
Options menu

References[1] http://www.celestrak.com
Dr.
Kelso'suniqueKeplerinformation database[2] http://www.weather.net.nz/
wxtoimg/
Software to decode APT and
WEFAX signals from weather
satellites[3] http://chrony.sunsite.dk/
is a pair of programs which are used
to maintain the accuracy of thesystem clock on a computer.
[4] http://www.jcoppens.com/
sat/index.en.php
My own humble site (chronically indevelopment), with some info on
satellites and equipment, andrecent satellite APT imagery

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

Receiving Weather Satellites in
Belgium
François Verstraelen
I first took an interest in weather satellite reception in
the mid 1980’s and must have been one of the firstamateurs in Belgium to do so. But after a few years, I
gave up the hobby and became more concerned withwatersports and short-wave radio. For the past six
years, though, I’m back on stage with the wx satellites.
I use a home-made HRX 137 receiver (Dutch concept)
to acquire images from the NOAA APT satellites, andhave two antennas which I built myself. The firstantenna is a crossed dipole with an LNA built into themast, which is for general use. It stands free and gives
good pictures from about Denmark down to Gibraltar.

The 5-element crossed Yagi mounted in the roof-space

The other antenna is a 5-element crossed Yagi without
LNA which I built from very cheap aluminium tubes.
The original concept was from the authors of the book
‘Weersatelieten’, which was published in late 1970: I
still have it in my hobby shack. It was—as far as I
know—the first book that gave very good help for how
to receive weather satellites in those early days.

A NOAA 15 channel-4 image obtained using the crossed
dipole antenna at 08:34 UT on January 25, 2002 showing
Polar Low’s sweeping down the Norwegian coast.

WxtoImg software and track the satellites with
Footprint and WXtrack.

A memory of days long gone—a Meteor 3-05 image taken withthe crossed Yagi, extending the range deep into the Arctic.

I’ve tried many antennas over the years, and for me
this Yagi is one of the best. I must say that the antenna
is mounted with a fixed elevation of 65°. I adjust it to
he desired azimuth by hand because the antenna isunder the roof.
I use this Yagi only to ‘see’ farther in the N.E direction
towards Russia and the Baltic states during the winterperiod. It gives me very fine pictures. I use the Yagi
with no rotator because the it is located in the loft,
underneath the roof of my house (about 10 meters
above the ground). I produce images using Wxsat andA few months ago, I bought a complete HRPT
installation from an amateur in the Netherlands, but
as yet I have not set it up. But some day soon I hope tostart with the reception of HRPT.
François Verstraelen is 55, is married with two
daughters, and lives in Turnhout in the northeast partof Belgium.

Weather Brief
A ferocious winter storm hit the eastern Mediterranean on February 12
closing roads and airports throughout Turkey. Twenty crew were
missing, feared dead, after their boat foundered in gale force winds near
Istanbul. Up to 40 cm of snow was reported in the village of Busa. In
Greece, the severe weather brought heavy snowfall, causing chaos in
Athens where overnight temperatures plummeted to –9°C, recovering
only to –1°C by the following midday.

www.geo-web.org.uk

Page 39

GEO Quarterly No 2Group for Earth Observation

May/June 2004

This true-color image captured by the Moderate Imaging Spectroradiometer (MODIS) instrument aboard NASA’s Terra satellite on
February 17, 2004 shows bright yellow streamers of dust sweeping from the coast of Morocco toward the Canary Islands. Just off
the coast of Lanzarote, the northeastern-most of the Canary islands, gravity waves caused by the high winds driving the dust storm
create dark and light stripes on the water. More gravity waves stretch from Gran Canaria—the round island toward the centre of thegroup—towards the Moroccan coast.
Image: Jacques Descloitres, MODIS Land Rapid Response Team, NASA GSFC
Page 40

www.geo-web.org.uk

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

European Publications On-line

Erratum

Simon Kennedy

No doubt some of our eagle-eyed readers noticed aminor glitch on page 11 of the ‘Polar Low’ article in
GEO Q1. Figure 5 displayed a repeat of figure 1. The
correct image, displaying the final shreds of the dying
storm, appears below.

In response to Francis Bell’s article regarding free
European publications, GEO readers may beinterested to learn that all of these publications, plus
archive versions, are available to download from theInternet as PDF documents. The relevant addresses
are:
Image
www.eumetsat.de(then select Publications/IMAGE Newsletter from theleft hand frame)
ESA Bulletin
http://esapub.esrin.esa.it/bulletin/bullets.htm

Earth Observation Quarterly
http://esapub.esrin.esa.it/eoq/eoq.htm

EUMETSAT Operations Bulletin

Figure 5 - NOAA 16 - 00:11 UT on December 22, 2003

The download address for EUMETSAT Operations
Bulletin No 10 printed on page 40 of GEO Q1
inadvertently contained a ‘rogue’ space character. The
correct address is:
http://www.eumetsat.de/en/dps/helpdesk/
documentation/pdf/newsbulletin10.pdf

Visit the GEO Website
Have you visited GEO’s website yet? If not, point yourweb browser towards
http://www.geo-web.org.uk

Cover Colour Images
Front
The crescent Earth as captured from Meteosat-8 by
Cedric Roberts on February 2, 2004
Image: © EUMETSAT 2004

A recent e-mail from Geoff Derby suggested that it
would be useful to have a Glossary of Terms includedin each edition of GEO Quarterly. It is certainly
something worth thinking about, though perhaps notin every issue. But in fact, the GEO website has a fullpage of such abbreviations and acronyms at:
http://www.geo-web.org.uk/acronyms.html

Back
Saharan dust being carried over the Alps. NOAA-17
APT captured by Gerry Berg at 10:28 UT on
February 21, 2004. The image was processed withWXtoImg, using the MSA mode (see report on page 43).
Official GEO Internet Discussion GroupGEO has its own, private and moderated on-line
discussion forum, called ‘GEO-Subscribers’.
The aim of the Group is to provide a forum where GEO
members can share information, ask questions and receive
speedy responses.
To sign up, send an email to:
GEO-Subscribers-subscribe@yahoogroups.com

Talking of the website, remember there are pages
devoted to joining GEO, a beginners section devoted to
APT imaging from the NOAA satellites and several
pages about the new Meteosat-8 satellite and the
EUMETCast and C-Band dissemination services. If
you would like to see some high-resolution coloured
images from the Meteosat satellites, please turn to:
http://www.geo-web.org.uk/met_samples.html

GEO Members’ Ideas
We are always interested to hear from GEO readers. If
you have ideas that you believe could help our website
to serve you, the membership better, do please send
your thoughts and ideas to our webmaster, Ray
Godden. Ray can be contacted by e-mail via:
webmaster@geo-web.org.uk

asking to be placed on the list.
www.geo-web.org.uk

Page 41

GEO Quarterly No 2Group for Earth Observation

May/June 2004

Douglas Deans - douglas@dsdeans.freeserve.co.uk
For this second issue of GEO Quarterly, it is back towork with a look at the most popular CD and a brief
update review to one of the better known programs.
There are times when software updates are in short
supply and I intend to use those quieter moments toremind readers, especially those new to the hobby, ofthe contents of some of the Showcase CDs. This issue
we look at GS1.
GS1 provides, in one neat package, all of David
Taylor’s weather satellite programs complete with thenecessary runtime libraries and many extras. However
there is much more to this CD. To make it a complete
working package it includes over 600 Mb of program
extras which serve two purposes. Firstly there is lots ofraw data, specifically for each of David’s programs, tolet new users use, experiment with, and enjoy themwithout having to produce or source their own raw
data. Looking back, I can well remember how
frustrating it was to install a new program and notknow what data to use or indeed where to find it.
Secondly there are lots of high-resolution images to let
you see just what can be achieved with the software. A
mixture of images from polar and geostationary
satellites are provided with some examples, including
animations, from the new pride of the European fleet—
Meteosat 8 (MSG-1). Details on how to order this CD,
or indeed any of the other Showcase CDs, are provided
below.

Some of the new features in this upgrade include ‘fine
tuning’ for RTTY, and a luxurious NAVTEX /SYNOP /RTTY message viewer.
One of the real attractions of this program is its ability
to work using a computer’s soundcard and, although
there is a range of other optional interfaces, I suspect
the soundcard route will be the attractive one to mostusers. JVcomm32 is available on GEO Software CD,
GS2. For further information or to download theprogram go to
http://www.jvcomm.de

JVcomm32 in action decoding a NOAA 17 image

JVComm32 v 1.30 pre

How to Purchase CDs

JVComm32, written by Eberhard Backeshoff, is
probably one of the best known multi-purpose
programs for the reception of FAX, RTTY / SYNOP /NAVTEX and SSTV. It can be used on all Windows
operating systems from Windows 95 up to the present
2000 and XP options.

Simply write to the address below requesting GS1,
GS2, GS3 or GS4. Prices are £5 for any single CD,
2 for £8, 3 for £11 or all 4 for £14. Please enclose
cash or cheque (made payable to Douglas Deans
not GEO) for the appropriate amount. Nothingelse is required.

Version 1.30 pre, will become full release version 2.00
when the help and support files are completed. Can I
take this opportunity to remind readers of some of themore interesting and useful features of the program? It
can be used for the reception of HF-FAX weather
charts, weather images from low earth orbiting
satellites (e.g. NOAA), geostationary weather satellites
such as Meteosat, plus RTTY, SYNOP and NAVTEX
messages. In addition, the program can be used for the
reception and transmission of amateur-radio SSTV
(Slow Scan TeleVision). In SSTV mode, JVComm32
receives and transmits all the modern popular free runmodes including the new high resolution Pasokonmodes P3, P5 and P7.

The cost includes the CD, packaging and posting,a small donation towards the cost of overheads,
the cost of overseas orders and the search for new
or updated software. No fee is asked from overseas
members although an exchange of software orinteresting satellite images is always welcome.

Page 42

Orders are normally dispatched on the day ofreceipt.
Order your CDs from:
Douglas Deans, 17 Montrose Way,
Dunblane, Perthshire FK15 9JL, Scotland.

www.geo-web.org.uk

May/June 2004

GS1

A ll D a vi d Ta ylo r’ s we a the r s a te lli te p ro g ra ms a nd li b ra ri e s
i ncludi ng the current releases of WX track, S atS i gnal, HRP T
Re a d e r, Ge o S a tS i g na l, Gro und Ma p , RX 2 P a ssC o ntro l a ndmany other program extras. Thi s di sc also contai ns a large
quantity of sample files, many of high-resolution data, for use
with the programs
WXtrack

Satellite Tracking Programv 3.4.0

Creates images from wave
files
Converts raw HRPT data files
into images
Manipulates geostationary
weather satellite data

v 2.5.2

GroundMap

Rescales satellite images

v 1.3.6

RX2 PassControl

Computer control program for
the RX2 receiverv 2.2.8

SatSignal
HRPT Reader
GeoSatSignal

GS2Group for Earth Observation

v 4.0.8

v 4.1.0

A wi de range ofsoftware for all aspects of weather satelli tereception including tracking, receiving, monitoring and image
manipulation. Content is detailed below but many other extras
are provided. Titles correspond to folder names. * implies a
DOS program.
Recall (wave file decoder).
Collection D02
Palette (modifies wxsat colour
palettes).
Scanner recorder v 1.8 (wavefile recorder). *NOAA95 /Collection D03*FENG99 (Software for the
NOAA 95 HRPT project)
Wxsat v 2.59 (Wave file
Collection D04
recorder/decoder). Satellite
Monitor (Wave file recorder).
AGSatTrack
Cirkite-weatherman

Satellite tracking programv 1.33Documents for the Cirkit Wxsat
receiver and the UOSat
receiver. (PDF format)
Provides current weather
conditions from the Internet toyour computer

Element Manager

2-line element manager

v 1.58

Footprint

Satellite tracking programv 2.10IrfanView

Fast image/slideshow viewer

v 3.80

JVcomm32
Ma c i nto s h k e p le r
editorNeoPaint
Paint Shop Pro
Satscape
Splitter
WXtoImg

JVcomm32 evaluation(APT/FAX/SSTV decoder)
For editing verbose AMSAT
format elements. Mac. OS X
and OS9 only
Neopaint for Windows Image
processing program (30 day
evaluation)
Paintshop Pro Image
processing program( 30-day
trial)
Satellite Tracker/decoder
Uti li ty program for spli tti ng andreuniting large files
WAV file acquisition anddecoding programv 1.30v 4.0
v 7.04v 2.00v 4.0v 2.5.9

GS3

3DEM package for 3D terrain visualisation
The C D i ncludes the full set of GLOB E ti les to allow you to
produce excellent images and flybys from HRPT images. Also
included is a selection of Mars MOLA files, sample images andhelpful guides.

GS4

Image CD (New) - A wide selection of high-resolution remotei mages from a range of satelli tes i ncludi ng stunni ng i magery
from the Space Shuttle missions. A full description and source
is provided for each image.

GEO Quarterly No 2

Gerry Berg (DK 1RR)
Saturday, February 21, 2004 was the day theweather went crazy all round the world.
In Canada, meteorologists were speaking of a‘weather bomb’ as heavy snowfalls deposited up to
90 cm in some places. These sudden unusually
heavy snowfalls almost paralysed normal life innortheast Canada. The blizzard completely buried
even 4-lane highways under enormous snowdrifts,
and 400 articulated lorries were snowed in on thetrans-Canada Highway during the heaviest snowfall
since 1944.
By contrast an exceptional heatwave in Australia
saw the temperatures rise to 41°C in Queensland
while the mercury reached a scorching 46° in New
South Wales, 11 degrees above normal for February.
In Sydney, temperatures reached 45°.
But it was much nearer home, in Europe, that muchof the crazy weather was observed.
The image on the back cover of this issue shows thesituation in Europe as seen from NOAA 17 at 10:28
UT on February 21. Major sandstorms over the
Sahara Desert can be seen whirling aloft hugequantities of sand which are being transported
northwards over Italy, the Alps, and central Europe.
The image at top right on page 17 was processed fromthe same pass to show the extent of precipitation overcentral Europe that day.
In Bavaria, the Saharan dust turned the sky a rangeof unusual colours; first blue-white, then yellow,
orange and ochre. On the Mediterranean island of
Minorca, motorists found their cars covered in a
thick layer of orange dust.
Cold northern air coming into contact with the warm
Saharan air was also responsible for capricious
weather over Italy. While northern Italy
experienced heavy snowfall, the south of the country
basked in temperatures as high as 25°C.
Continuous storms over Spain caused substantial
damage and heavy snowfall in the north of thecountry closed many mountain passes: those thatwere open were only passable by vehicles fitted withchains. On the Mediterranean coast some beaches
were white with snow. Severe weather in the southwest of Gran Canaria devastated greenhouses full of
bananas, tomatoes and cucumbers. Forty
holidaymakers had to be rescued when their hotel
was flooded.

www.geo-web.org.uk

Page 43

GEO Quarterly No 2

Dear Les,
I've a number of points to raise arisingfrom the launch issue of GEO Quarterly.
I was interested to note that the latest
issue of Image reports the creation ofanother group called GEO, the acronym
stands for Group on Earth Observation,
so is slightly different from 'GforEO' if I
can express it like that. 'GonEO'. is an‘...ad-hoc inter-governmental group [setup] ... to oversee coordination andintegration of the different Earth
Observation Systems.’
Your article on The Polar Low
Phenomenon is interesting with somegood images but surely the copyright for
Figure 1 should be to NOAA and not
Ferdinand Valk? As has been discussed
at various times in the past NOAA statethat they are happy for images from theirspacecraft to be published as long as
they receive the copyright credit. As somuch is made elsewhere in the journal of
the copyright issues surrounding MSG
images is seems churlish not to also
observeandrecognise
NOAA'scopyrights.
Finally, congratulations on the journaland particularly the use of A4 sized
paper. The size really allows the images
to be displayed to full effect. The full page
MSG images are stunning.
Best wishes,
Simon Kennedy, Guildford, SurreyGroup for Earth Observation

purposes, that proper credit be given
to the agency. Typically the use of
the NOAA logo and a brief statementof what the image is and how or
where the image was obtained will
suffice (i.e. NOAA-17 1-km visible
image from February 23, 2004. This
image was obtained from the NOAA
Satellite Active Archive).
Regards, Darrell
Darrell R. Robertson
Satellite Data Services Team Lead
NOAA/NESDIS Direct Services
Division
This appears to conform largely to what
you say. Best wishes to you and GEO.
My membership form will be in the post
when work and my 2 year old and 6 week
old daughters allow.
Simon Kennedy
Hi LesMy copy popped through my letter box, inFelixstowe, at 09.09 this morning. A nicelooking mag, well done. I shall be having
a long slow coffee break this morning. My
thanks to the GEO launch team. My
membership form will be in the post
tonight.
Regards,
Bill Price, Felixstowe, Suffolk.

Editor’s reply to Simon . . .
Dear Simon,
The copyright issue is interesting, notleast because NOAA openly provide theirdata, paid for by the public purse, free toeveryone. EUMETSAT, on the other
hand, do not - you generally have to pay
for their data products, and they demanda copyright notice. NOAA only request acredit for materials directly downloaded
from their websites. So in the case of
NOAA images, directly downloaded byusers such as Ferdinand, it has always
been the custom to credit the person who
created the image, and not NOAA.

LesThanks for the new GEO magazine,
CONGRATULATIONS, its brilliant. I will
be joining the new group fairly soon.
Keep up the good work.
Kind Regards, Mike Stevens. G4CFZ. . and Simon’s follow-upLes,
I asked Darrell Robertson of NOAA forclarification and I include his response
below:
Simon,NOAA satellite images are in the
public domain (i.e. paid for by the
citizens of the United States for
public use). No copyright is required
but NOAA does request, when using
its data, especially for commercial

Posted on GEO-L
I've just received my first copy of GEO
and I wasn't disappointed - a truly
professional publication - I'll definitely be
subscribing!.
I also was surprised and impressed with
the A4 size. This allows much better
detailed pictures, for example theglorious full colour Earth view. Keep up
the good work.
Best regards,
John Silver, Whiteley, Hampshire.

Page 44

To the GEO TeamTake bow, gentlemen. The new magazine
is superb quality. An auspicious start,
long may it continue.
Best wishes,
Norman Munro, Isle of Lewis.

www.geo-web.org.uk

May/June 2004

Posted on GEO-L
The GEO Quarterly has just landed in myletter box here in Melbourne, Australia.
The best way to describe it is....stunning!!!!
I'm most impressed with the A4 format.
Just look at the outside back cover andpage 29 !! I'd be most proud to get one of
my images in there in all that glorious
colour.
I haven't had time to read it yet. That'll
come later this evening after the kids arein bed and the wife watches her
television.
Well done, and thank you.
Lindsay Vincent, Victoria, Australia.
Dear Editor
Cedric Roberts recently provided an
excellent article regarding evaporation. I
wonder if Cedric would be so kind as to
publish how he calculated the respective
average evaporation data based onsunshine - temperature / rainfall rate overthe past year. I have looked through acouple of meteorology books but havenot found the answer.
Peter Bartlett, Pinner, Middlesex.
(Cedric Roberts’ reply appears on
page 28 of this issue - Ed)Les
GEO Q1 arrived this morning. Certainly
looks nice in the larger format - only
reservation I've got is the note about
future issues possibly coming out on CD
rather than in paper format. I canunderstand the economics surrounding
this but personally I prefer something I
can read anywhere/anytime without
having to be continually stuck in front of ascreen. I'd be willing to pay a little more if
need be to maintain a paper offering.
But that's for future mulling - I've seen
enough to officially join up.
Colin Knight, Eastleigh, Hampshire.
Dear GEO Editor,
Congratulations for the launch issue of
The Geo Quarterly. The magazine isgreat. Its articles and images are very
good. I know it is already agreat
successamongamateurs(andprofessionals!).
Regards,
Raul Fritz B. Teixeira, Department ofMeteorology, Foundation for Meteorology
and Water Resources of the State of
Ceará, FUNCEME Brazil.
(www.funceme.br)May/June 2004

Group for Earth Observation

GEO Quarterly No 2

Peter Wakelin
In his letter in the last issue of GEO Quarterly, Francis
Bell correctly identified one of the essential ingredientsfor hurricane formation as high sea surface
temperatures. 27 degrees C is considered to be theminimum requirement and this value is reached in theSouth Atlantic regularly but only over a very small
area when compared with other ocean basins.
In addition, these values are reached only in a shallow
surface layer a few metres in depth and whenever apotential storm circulation is established, thestrengthening winds churn up the sea causing thesurface temperature to drop by several degrees so, inorder to develop, any potential storm has to keep
moving over very warm water.
As the South Atlantic receives the same solar radiation
as the other southern oceans, there must be anotherreason for the lower temperatures and this can befound by looking in a world atlas. The shape of theSouth Atlantic basin does not favour warm tropicalwaters for two reasons:across the true equator. In the Atlantic, this thermal
equator very rarely ventures very far south, almost
certainly due to the all-the-year-round hightemperatures in the 'bulge' of west Africa.
Very near to the equator, significant wind circulations
cannot form and the majority of hurricanes (typhoon isanother name for the same thing) form near latitude
15°. At this latitude in the South Atlantic, the upper
wind regime generally precludes hurricane formationand this, together with the small area of warm sea
means that South Atlantic hurricanes are extremely
rare.
Had I written this a week earlier, I would haveconcluded by saying that no hurricane has been
observed in the South Atlantic since satellite
monitoring of the oceans began about 40 years ago but
the image on the inside front cover, and the one below,
show that this is no longer true.

1 Ocean currents circulate counter-clockwise insouthern oceans and the cold waters of the
Benguela Current are carried northwards past St
Helena and onwards to Ascension, warming all thetime before turning westwards towards Brazil.
However, unlike in the Pacific and Indian Oceans,
the South Atlantic is narrow at tropical latitudes
and the water soon turns southwards again as theBrazil Current. Consequently only a very small
area east of Brazil reaches the necessary
temperatures.
2 The shape of the Antarctic continent results innear-freezing water at more northerly latitudes in
the South Atlantic than anywhere else in thesouthern oceans; at 50°S latitude off SW Africa,
the sea temperature is around 3°C at its summer
peak. Compare this with the 18°C or thereabouts
at latitude 50° in the North Atlantic.
Southern Oceans reach their highest temperatures inMarch but it is interesting to see that, at the time ofwriting in late March, the warmest waters in the entire
Atlantic are north of the equator. In addition toneeding high sea temperatures to develop, it is alsoessential that winds in the lowest few kilometres of theatmosphere remain light during the initial formation
as any significant wind shear will disrupt thedevelopment. Light winds occur in the tropical‘convergence zone’ where the winds from the tradewind belts converge. This can be looked upon as the‘thermal equator’ and tends to follow the seasons

Mike Stevens sent us this Meteosat-7 D7 segment from16:00 UT on March 26, clearly showing the cyclone in
relation to the South American coast.
Image © EUMETSAT 2004

An Internet search will reveal much about hurricanes
but for an in-depth study I recommend
http://www.bom.gov.au/bmrc/pubs/tcguide/
globa_guide_intro.htm

For current global sea temperatures try

www.geo-web.org.uk

http://www.ssec.wisc.edu/data/sst.html

Page 45

GEO Quarterly No 2Group for Earth Observation

May/June 2004

Les Hamilton
In early February this year, Gerry Berg of Wilnsdorf,
Germany sent me a number of coloured NOAA-17
APT images displaying interesting cloud whorls over
the Tyrrhenian Sea. Gerry suggested that he wasobserving a series of von Kármán vortices, and one of
his images appears inside the back cover of thisissue. The effect was visible over two full days, andappeared to emanate from the island of Elba
opposite the NE corner of Corsica as illustrated by
the two channel-2 NOAA-17 HRPT segments
opposite.
I don’t recall seeing such a phenomenon in this partof the world before, and decided to learn more about
the intriguing von Kármán effect.

Theodore von Kármán
Theodore von Kármán was born in Budapest in 1881
where he trained as a mechanical engineer before
undertaking undergraduate studies and eventually
his PhD at Göttingen in Germany. Von Kármán was
one of the pioneers of early aeronautics, building a
prototype helicopter for the Austro-Hungarian Army
during the First World War and becoming involved
over the years in the development of Zeppelins,
gliders, airplanes and even rockets. He designed andbuilt the World's first wind tunnel, and it was in thatdevice, while investigating the relative merits ofstreamlined and cylindrical spars on biplaneconfigurations, that he first observed the eponymous
vortex pattern. Among his lifetime achievements,
von Kármán became head of Caltech’s Guggenheim
Aeronautical Labs in Pasadena from 1930 to 1957,
he was a co-founder of NASA’s Jet Propulsion
Laboratory and was instrumental in founding boththe International Academy of Astronautics and thevon Kármán Institute in Brussels.

Figure 1 - NOAA-17 - 09:56 UT - February 5, 2005
Image: NOAA SAA - Processing: HRPT Reader / Groundmap

The von Kármán EffectVon Kármán vortices form when prevailing winds
are disturbed by an object, generally an island orgroup of islands, which possesses sufficient elevation
above sea level to obstruct the normal airflow. On
encountering the island, a disturbance is set up in
the airflow, and this propagates downstream in theform of a double row of vortices exhibiting alternate
directions of rotation.
The effect consists of two roughly parallel rows ofvortices positioned such that a vortex in one row issituated mid-way between two adjacent vortices in
the other row (figure 3). Initially, these vortices arecomparable in size with the island that creates the
Page 46

Figure 2 - NOAA-17 - 09:33 UT - February 6, 2005
Image: NOAA SAA - Processing: HRPT Reader / Groundmap

Figure 3 - Schematic illustration of the formation of von Kármán
vortex streets in the lee of an island.

www.geo-web.org.uk

May/June 2004

Group for Earth Observation

GEO Quarterly No 2

disturbance in the first instance. But later, as thevortices drift downstream, they tend to increase indiameter and gradually move farther apart: they may
persist to form a wake up to 100 kilometres in widthand extending several hundreds of kilometres inlength. An island creates a pair of new vortices roughly
once every 8 hours and these may persist for as long as
30 hours. All the vortices in one row have similar
circulation, but opposite to those in the other row.
The resulting vortex streets are easily identified insatellite images on account of the characteristic
formations they create in marine stratocumulus cloud
sheets. These clouds are often associated with a wellmarked temperature inversion in the lower levels of
the atmosphere, the height of which is important indetermining whether the air flows more easily aroundthe island rather than over it. Von Kármán vortex
streets are more likely to occur in a linear low-level airstream flowing steadily at around 35 kilometres perhour. Such vortex streets are frequently observed as
cloud wakes in the lee of the Canary and Cape VerdeIsland groups; Madeira; the Pacific islands ofGuadalupe (west of Baja California) and Juan
Fernandez (off Chile); and Jan Mayen island in thenorth Atlantic ocean.

Examples of Cloud Vortex Streets
The Landsat-7 image reproduced in figure 4 shows
clouds near the Juan Fernandez islands off the coast of
Chile. Alejandro Selkirk Island (famous as thelocation for the Robinson Crusoe story) is situated near
the lower left-hand corner of the image. This island isapproximately 1.5 kilometres in diameter and rises
precipitously some 1600 metres from the surrounding
ocean into a layer of marine stratocumulus clouds. A
steady wind blowing northward towards the equatorcreates vortices which flow from the eastern edge of theisland with a clockwise rotation and with a counter-

Figure 4 - A Landsat-7 image dating from September 15, 1999
showing a splendid von Kármán vortex street being shed by
the Juan Fernandez Islands off the coast of Chile.
Image courtesy Bob Cahalan, NASA GSFC

Figure 5 - This ranks as possibly the longest von Karman vortex street ever imaged by satellite. It
was observed emanating from Jan Mayen island in the northern Atlantic ocean by the Multi-angle
Imaging Spectroradiometer (MISR) aboard NASA’s Terra spacecraft on June 6, 2001
Image Credit: NASA/GSFC/JPL, MISR Teamwww.geo-web.org.uk

Page 47

GEO Quarterly No 2Group for Earth Observation

May/June 2004

clockwise motion from its western edge. The vortices
grow as they advect hundreds of kilometers downwind.
Both clockwise and counter-clockwise vortices are
generated by air-flow around the island. Much of theisland air tends to be cloudless because of a local ‘land
breeze’ circulation set up by the greater heat capacityof the waters surrounding the island. As each vortex
separates from the island’s leeward side, it engulfs a‘parcel’ of some of this clear air. These parcels of clear
island air can subsequently be carried within thevortices for considerable distances before they mix into
the surrounding clouds and disappear.
What is believed to be the longest cloud vortex street
ever viewed by a satellite is shown in figure 5. It was
imaged stretching approximately 365 kilometres
southward (right) from Norway’s Jan Mayen Islandby the multi-angle imaging spectroradiometer (MISR)
aboard NASA’s Terra Earth observation satellite on
June 6, 2001.
Jan Mayen is an isolated island located in the northAtlantic Ocean about 650 kilometers northeast of
Iceland. At the northern end of the island rises the2200 metre high volcano Beerenberg, which is morethan sufficient an obstacle to produce frequent cloud
wakes. The cloud-covered island is situated at lower
left in this image and the volcano can be seen risingfrom its centre (north is at the left-hand side of thisimage). Fifteen open vortex centres and at least threeclosed vortices trail behind the island in this view. The
entire cloud street covers an area of about 365 x 158
kilometers: again a cloud-clearing effect is apparent atthe vortex centres until they finally become closed at
the sixteenth eddy.

Figure 6 - Vortex street streaming from Jan Mayen Island
NOAA 14 HRPT - March 23, 2001
© Space Monitoring Information Support laboratory (SMIS IKI RAN)

rotating motions induce a vertical wind component
that can break up the cloud deck.

References and Further Reading• http://www.rta.nato.int/RTOhistory/TvK.htm• http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/
vonKarman_vortices.html• http://www.space.com/scienceastronomy/
planetearth/vortex_street_001213.html• http://www.ocean.washington.edu/research/gfd/
cloud/clouds.html• http://www.jpl.nasa.gov/releases/2002/
release_2002_103.html• http://www.eumetsat.de/en/area5/special/vonkarman_04042001.html• http://www.knmi.nl/~floor/artikelen/zenit/karman/• http://www.aerodyn.org/People/vonKarman.html

Obtaining images of von Kármán vortex streets fromJan Mayen Island should be well within the capabilityof many GEO readers, particularly if they receive
HRPT or MSG. Figure 6 shows a NOAA 14 HRPT
segment containing a vortex street being shed fromJan Mayan island while figure 7 illustrates how well
Meteosat-8 detects cloud wakes around the CanaryIslands.
GEO readers are encouraged to look out forthis phenomenon and to submit their own
images of cloud wakes for future publication.
Finally, the lower image on the inside back cover ofthis Quarterly is a true-color MISR image of a von
Kármán vortex street, in this instance shed by theeastern Pacific island of Guadalupe lying 260
kilometers west of Baja California. The rugged terrainof this volcanic Mexican island, about 35 kilometers
long, reaches a maximum elevation of 1300 metres(north is to the left). The orientation of the vortex
street indicates that the wind direction is from lower
left to upper right (northwest to southeast). The areas
within these vortex centres tend to be clear because thePage 48

Figure 7 - Von Kármán cloud wakes generated by the CanaryIslands, imaged by MSG-1 in May 2003
Processing: Cedric Roberts Image © EUMETSAT 2003

www.geo-web.org.uk

Gerry Berg of Wilnsdorf in Germany spotted what he took to be von Karman vortices coursing
south over the Tyrrhenian Sea between Italy and the islands of Corsica and Sardinia, apparently
spawned by the Island of Elba. NOAA 17 APT image - 09:30 UT on February 6, 2004.

Von Kármán cloud wakes being spawned from Guadalupe Island - June 11, 2000 (see article on page 25)
Credit: Jacques Descloitres - MODIS Land Rapid Response Team, NASA GSFC.