Group for Earth Observation

December 2013
Inside this issue . . .
The lead article this issue
relates to the developing
practice of using a DVB-T
dongle to receive APT satellite
imagery. Author Raydel
Abreu Espinet boldly statesthat ‘The Future is Software
Defined Radio’, and his APT
images show that he has
mastered this new techniquesuperbly.
It’s now well known that the
Jet Stream is a major player
in determining our weather.
Mike Stevens provides abasic introduction to thisfascinating topic.
Marc Peigneux describes avisit to Mont Aigoual, the lastactive mountain weather
observatory in France.
For the computer hobbyist,
David Taylor introduces the
Raspberry Pi and describes
how he programmed a digitalwall-clock.
We also have the second partof James Brown’s article, thistime explaining the impact ofthe personal computer on ourhobby.

An
Ed niviti eron sa

ryThis issue of GEO Quarterly
also carries features on
Arctic Melting, Cyclone
Phailin, an eruption of
Kluychecskaya andthe recovery of the
Chelyabinsk
meteorite ...
th

Earth Observation and Weather Satellite Enthusiasts

40

10

The Independent Amateur Quarterly Publication forGEO MANAGEMENT TEAM
Director and Public Relations
Francis Bell,
Coturnix House, Rake Lane,
Milford, Godalming, Surrey GU8 5AB,
England.
Tel:
01483 416 897
email: francis@geo-web.org.uk
General Information
John Tellick,email: info@geo-web.org.uk
GEO Quarterly Editor
Les Hamilton,
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Aberdeen AB15 7PW, Scotland UK.
email: geoeditor@geo-web.org.uk
GEO Quarterly Despatch
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email: members@geo-web.org.uk
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Fax:
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email: tech@geo-web.org.uk
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David Painteremail: education@geo-web.org.uk
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email: shop@geo-web.org.uk
International Liaison
Rob Denton,
email: international@geo-web.org.uk
Clive Finnis
Carol Finnis

Publisher
Published by The Group for Earth
Observation Limited, a company in Englandand Wales, limited by guarantee and nothaving share capital.
The Company Number is 4975597.
The registered office is Coturnix House,
Rake Lane, Milford, Godalming,
Surrey GU8 5AB, England.
Printing
Hedgerow Print,
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Crediton, Devon EX17 1ES.
Tel: 01363 777 595
Responsibility
Every effort is made to ensure that thetechnical and constructional articles
published in this Quarterly are correct.
However, the ultimate responsibility iswith the reader to ensure the safety of
constructions and for any interfacing withother equipment. GEO cannot accept liability
for shortcomings in any published design or
any constructions carried out by members orother third parties.
Copyright GEO © 2013
The contents of this Quarterly remain theintellectual property of the Group for Earth
Observation Limited and its contributors.
Copying of text or images, either from theprinted Quarterly or from any electronicallystored source, is forbidden without
permission from the Editor.

Les Hamilton
geoeditor@geo-web.org.uk

O

ur headline article this issue is an expert treatise on the reception of APT satellite
imagery in which Raydel Abreu Espinet, who lives in Cuba, describes his progress over
the years using a variety of receivers. But as Raydel boldly relates: ‘‘The Future is Software
Defined Radio”, and the second section of his essay details his experiences using theinexpensive RTL-SDR Ezcap EZTV645 DVB-T Digital TV USB 2.0 dongle (which covers 48 - 864 MHz)
with SDR software. If Raydel’s NOAA-15 image which appears on page 17 is anything to goby, he is most certainly producing results to rival conventional APT receivers. GEO Quarterly
readers looking for an inexpensive, interesting project to occupy themselves during the dark
winter days could do worse than follow a similar course, and we look forward to learning
about your experiences next year. Raydel’s article starts on page 14.
EO will hold a Symposium at the National Space Centre, Leicester on Saturday,
April 26, 2014. Certain to be at the top of the agenda is the impending upgrade of the
EUMETCast Europe service from the DVB-S to the DVB-S2 standard. You can read fulldetails, insofar as they are currently known, on page 25.
his month brings the conclusion of James Brown’s two-part series chronicling his
experiences during a lifetime interest in weather satellite imaging. In this final part,
James details how the appearance of the now ubiquitous personal computer marked aturning point for the hobby.
s Francis Bell laments in his GEO Report, issue No 38 of EUMETSAT’s popular Image
Newsletter has turned out to be the final paper-based copy. Rebranded Insight, thestories that would have appeared in Image, as well as archived PDF copies of Image
newsletters, are now only available on-line atG
TA

http://www.eumetsat.int/website/home/InSight/O

ne of the great success stories of the past two years has been the popularity of thecredit-card sized Raspberry Pi mini computer. David Taylor has been experimenting
with this remarkable little device and presents a project he has been working on to create adigital wall clock display on an LCD television screen.
inally, as GEO celebrates its 10th anniversary, we wish all our readers the very best ofhealth and happiness for the Festive Season ahead, and for the New Year that awaits
us. With imminent changes in EUMETCast, and the emergence of SDR for decoding APT
satellite images, there are sure to be exciting times ahead.

F

Copy Deadline for the next issue of GEO Quarterly is
Friday, January 31, 2014.

Contents
GEO Report
Cover and Full Page Image Details
Swedish River Detail revealed by NOAA-15
A Raspberry Pi Digital Wall Clock
Arctic Meltdown: permanent sea ice increases
Bolshevik Island
The Jet Stream and how it affects Britain’s Weather
APT Reception with low-budget stations
Weather Systems in Collision
Cyclone Phailin
Another Tale from Yesteryear
Get Space!
GEO Symposium - 2014
Weather Watching Away from Home: Part 2
Geostationary Feng Yun-2 Imagery from China
The Way We Were: How the PC changed everything
NOAA Debates Need for L-Band Transmissions
Klyuchevskaya Erupts
Chelyabinsk Meteorite Recovered
Temperature Profiles of Cyclones and Typhoons
Satellite Status
FeedbackMore thoughts on the WS 1081 Weather Station
Mont Aigoual Mountain Weather Observatory
GEO Helplines and Internet Discussion Groups
Copy deadline for the next issue of GEO Quarterly
GEO Membership Application FormGEO Shop Catalogue and Price List

Francis BellDavid Taylor
David Taylor
Les Hamilton
Les Hamilton
Mike Stevens
Raydel Abreu Espinet
Les Hamilton
Les Hamilton
Francis Bell
Francis Bell
Francis Bell
Alistair Dunlop
Les Hamilton
James Brown
NOAA
NASA Earth Observatory
Les Hamilton
Francis Bell and Les Hamilton

Storm Dunlop
Marc Peigneux

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GEO Quarterly No 40

The Group for Earth Observation

December 2013

Francis Bell

This issue of GEO Quarterly celebrates the 10th anniversaryof the formation of GEO. Although a previous meeting hadtaken place a few weeks before, my guiding date for ourformation is the November 23, 2003, the date on which theGroup was registered with Companies House as a limited
company. The decision to register as a company was a formof protection for all our members, and the management
team, so that ultimate responsibility for legal, financial andother areas would rest with the company, and not with any
individual member. Fortunately, we have never had to seek
this protection and, now established, the cost of runningthe company is only £15 a year provided we comply with thelegal administrative requirements.
I offer my congratulation to those members who have beenwith us for the full 10 years and for sharing their technicalknowledge and experiences in our specialised hobby.
Particular thanks must go to those involved in the productionof GEO Quarterly: our contributors, the editor, the printers,
and those involved with its distribution. GEO Quarterly isrecognised by all who read it as high quality publication.
Thanks also to those who have helped to run the GEO
Shop, which was established in March 2005. The Shopmakes available high quality satellite receiving equipment
at reasonable prices: these items would be difficult to buy
elsewhere and their availability is a recognition of the time
and trouble that has been invested into sourcing these items
from around the world. Our website is another area fromwhich we all benefit, thanks to he expertise and commitment
on the part of our webmaster.
I fully expect the next 10 years will be as dynamic as thosejust passed because there are planned changes to both the
EUMETCast and NOAA satellite services: hence a requirement
for GEO to keep in touch with these organisations, and to
exchange skills and experiences within our own group.
EUMETCastIn the near future there are to be profound changes in the
direct reception of the EUMETCast service. The encoding of
the data streams will change from the current DVB-S to the
DVB-S2 standard, and this will also necessitate transmission
being disseminated from a different satellite. These changes
are necessary to enable higher rates of transmission to beachieved.
Currently, the maximum data rate is about 20 Mbps but the
new system will be capable of 60 Mbps and have a flexible
more efficient method of encoding the data. EUMETCast isplanning to retransmit more high resolution images, hence
the requirement for this new service.
EUMETSAT publish their plans for the upgraded service intheir weekly bulletins.
The guide to finding the latest bulletin issued by EUMETSAT
which relate to the proposed changes from the DVB-S
standard to the new DVB-S2 VCM standard can be found by
the following route.
Log on to EUMETSAT’s web sitewww.eumetsat.int/

2

At the right of the page, below the main image, you will see
this panel bearing the caption:
EUMETCAST EUROPE
MIGRATING FROM DVB-S to DVB-S2

Click anywhere on this panel to move directly to the updated
Technical Bulletin relating to the proposed new service.
This route should continue to work, even if the page referenceis changed by EUMETSAT as the bulletins are updated. If wepublish a single page reference it is likely to become out of
date, hence the above route is recommended.
If necessary, I will try to have an extract of this/thesenotices placed on our own website, which may makethem more accessible to our members. GEO management
is following these notices closely and are in touch withEUMETSAT for technical advice and the availability ofnecessary new receiving equipment for the upgraded
service. We are planning our own tests with new receivers
so that we may give best advice to our membership when
the new EUMETCast service begins. With this in mind, we
hope to have further information available, perhaps withdemonstrations, at our symposium in April 2014. See theSymposium notice on page 25
NOAA
Looking further into the future, it is worth noting thepotential change to NOAA’s policy relating to direct receptionof their weather satellites. My assessment is there will
be no changes to the current service from existing NOAA
polar orbiting satellites, and APT will continue for the life of
NOAAs -15, -18 and -19, but the future of direct reception
from weather satellites is being questioned, as there are othermethods of disseminating these data, such as by Internet or
landline.
Together with others, I have received a notice for NOAA whichraises the above issue but also identifies potential down-link
specifications for new satellites. The notice also includes aquestionnaire but by the time members have a chance to readthis text, the time frame for responding to the questionnaire
will have passed. You can read a summary of the main points
covered in this questionnaire on page 37 of this magazine.
Should you wish to read the full notice, I can forward it to
any member on receipt of an email request to myself at
francis@geo-web.org.uk

You will not be able to make a formal response to the notice
but at least it will keep you informed of NOAA’s thoughts

www.geo-web.org.uk

December 2013

regarding the future of direct weather
satellite reception.
GEO Symposium - April 26, 2014
On page 25 you can read a notice
relating to our 2014 Symposium. I hope
this event will be well attended because,
as well as bringing delegates up-to-datewith EUMETCast services and othertechnical issues with presentations
and demonstrations, towards the endof the day we will hold our members’
AGM. During this meeting there will bereports about membership numbers,
accounts and those other mattersusually covered at an AGM. However,in addition it is the opportunity formembers to offer their own feedback to
the Group, with possible suggestions
for GEO’s future. This is why I hope themeeting will be well attended.
Image
Several time a year, I receive a printed
copy of EUMETSAT’s publication‘Image’, and usually read it cover tocover. But in the September 2013
issue there is a notice saying that thisis to be the last printed version of the
publication, which in future will only be

The Group for Earth Observation

available electronically via their website.
I am disappointed because I like thepaper copy but recognise the economyof having an electronic only publication.
Software Defined Radio (SDR)
Prompted by Rob Alblas’ report in
GEOQ 37, plus articles in RadCom and
AMSAT-UK’s quarterly journal, I became
intrigued with the use of SDR for the
reception of weather satellites. I had tohave a go myself. Accordingly, I boughta plug-in USB dongle which claimed toreceive a wide range of radio frequencies
and modulations with the 137 MHz
narrow-band FM used by the current
NOAA satellites falling well within it’s
specification. It has taken me several
months of experimentation, but now
I can receive horizon to horizon APT
images using SDR. I will write a reportof my experiences for the next issue.
One of my recent images is shown
below.
My experience with my first SDR dongle
has provoked me to buy another very
modestly priced, widely available one.
My experiments will begin as soon as I
have the correct software for this device.

GEO Quarterly No 40

Front CoverReader Keith Fraser spotted this Terra
MODIS image on September 3, 2013,
which shows an unusual pattern of cloud
whorls surrounding the Balearic islands.
Image: LANCE-MODIS/NASA/GSFC

Inside Front CoverLaurence Holderness acquired this APT
image from the 13:55 UT NOAA-19
pass on April 19, 2013. Laurence kindly
provided the WAV file, captured using
WxSat, which we have processed using
SatSignal and Photoshop.
Inside Back CoverThis splendid image of the entire east
coast of Australia is a composite of three
MODIS frames acquired by NASA’s Aqua
observatory on September 29, 2013.
Image: LANCE-MODIS/NASA/GSFC

Back CoverMike Stevens sent in this attractive Terra
MODIS image captured on April 21, whichdisplays a veil of semi-transparent highaltitude cloud swirling up from the Bay of
Biscay and across England.
Image: NASA/GSFC/LAADS Web

Page 8NASA’s Aqua satellite obtained thisgraphic MODIS image of New South Waleson October 19, 2013, showing smoke fromwildfires billowing over the state while athick pall of smoke stretches offshore.
Image: NASA/GSFC/LAADS Web

Page 9Anthony Lowe acquired this attractive
NOAA-19 channel-2 visible image of theUK from the satellite’s 13:10 UT pass on
September 23, 2013. Great Britain sits inthe centre of a region of high pressure andfog lingers over central England.
Page 31This channel-4 IR image from NOAA-18
dating from 03:58 UT on October 29 shows
calm conditions either side of the English
Channel in the wake of the previous day’s
Great Storm.
The Quarterly Question posed in GEO
Quarterly 39 related to the abbreviation‘VCM’ in the context of data transmissions
from communication satellites. The question
was prompted by the fact that EUMETSAT
is moving to a new data transmission
standard for their new service, beginningwith validation in July 2014 and a fullservice starting 1st August 2014. They will
be using DVB-S2 VCM and those wishing
to receive the service must have equipment
capable of receiving this new standard.
The answer to the question what does
the abbreviation VCM stand for is Variable
Coding and Modulation.
My thanks to those who took an interestin this question and knew the answer. I
received correct answers from:

Mike Stevens (G4CFZ) UK
Elmar Bogels Brunssum The Netherlands
Andreas Lubnow Braunschweig Germany
Dermot Cronin Killiney Co Dublin
Quarterly Question 40
This Quarterly Question is less technical,
but relevant to every one of our members
who receive live signals via the EUMETCast
service. According to EUMETSAT’s
published plans, what is the very last dateon which it will be possible to receive thecurrent DVB-S transmission service fromthe current communications satellite? After
this date you will have to be on the new
system or receive nothing. Answers tofrancis@geo-web.org.uk

by January 31, 2014.

www.geo-web.org.uk

Image: SMIS

Page 32
This segment from a Metop-B passacquired by Mike Stevens via EUMETCast
on September 10, 2013 shows a region
from the Caspian and Aral seas, throughIran to the Persian Gulf and Gulf of Oman.
Image © EUMETSAT 2013

Page 40
Just days before the South Korean GrandPrix was due to take place, Typhoon
Fitow threatened to spoil the show. In thisimage from China’s newest geostationary
satellite, Feng Yun 2E, Fitow is seen
heading north across the East China Sea
at 01:30 UT on October 3, 2013.
Image: FengYun Satellite Data Center(http://satellite.cma.gov.cn/)

3

GEO Quarterly No 40

The Group for Earth Observation

December 2013

David Taylor

On August 25 this year, taking advantage of the longpolar summer, I captured an APT image from NOAA-15
that I found particularly interesting. It’s from the early
05:47 UT pass over Sweden, and it was the rivers
entering the east coast that caught my attention.
I was fortunate to be able to obtain an HRPT versionof the pass, courtesy of the University of Berne, and4

the image on this page is the result of converting theprocessed image into a natural scaling centred on
60°N, 15°E.
I would love to have confirmation from one of ourSwedish readers as to what may be causing the effect,
and whether it was fog or mist, or maybe even sunglint.
I’ve not seen a phenomenon quite like this before.

www.geo-web.org.uk

December 2013

The Group for Earth Observation

GEO Quarterly No 40

David Taylor
The Raspberry Pi Card Computer was designed to get youngsters
programming, with a view to them having more experience when
they started their university courses. But the computer has actually
become very popular with hobbyists as well, due its low cost,ease of programming, and the fact that it has a variety of input
and output pins which can be connected to hardware and used inprograms to sense and control a multiplicity of peripherals.
http://www.raspberrypi.org/

The Raspberry Pi can have a camera attached and has beenused in high-altitude ballooning. Although the range of applications
to which the 1.5 million cards sold so far have been put is very
diverse, my own simple project was to just replace a radio clock
working from the 60 kHz MSF transmissions with a clock basedon the Network Time Protocol (NTP)—time derived from theInternet or from a local GPS receiver. NTP has been mentioned
in GEO Quarterly on a number of occasions, as accurate time isrequired for good satellite tracking, lightning detection, and for
coordinated reporting of events from stations scattered throughout
the world. It just so happened that an older 10.2-inch LCD TV
became free and I wanted to have a go at programming the
Raspberry Pi to learn just a little (but not too much) more about
Linux. A free, close variant of my favourite programming language(Embarcadero’s Delphi/Pascal, not free) is available for Linux,
Windows and the Mac, so it was a chance to try that as well.
The project involved setting up the Raspberry Pi to display correctlyon the analogue TV, using the Free Pascal and Lazarus IDE towrite a suitable wall-clock program, learning how to auto-login on
the Raspberry Pi, and how to start a program automatically on thedesktop (i.e. using the GUI). Figure 1 shows the clock program
feeding the wall-mounted TV. The source and binary files areavailable for download [1], so you can either run the program as is,or modify it to suit your own preferences. It’s very simple right now,
but the results are just what I want.
Your Raspberry Pi should be up and running, network connected,
and running NTP correctly. It should be almost correctly configured
using the NOOBS (New Out Of Box) software you can download
or buy on an SD card. Select the Rasbpian Linux from the choices

Figure 1 - The Digital Clock Display on the TV Screen

offered by NOOBS. My own Raspberry Pi runs over Wi-Fi allowing
it to be placed anywhere within Wi-Fi range. Although it’s not
required in this application, if you want to be very precise withyour Raspberry Pi’s timing, you can configure it as a stratum-1
server and use that for the rest of your network [9]. As the average
CPU taken by the clock program is just 3% it shouldn’t makethe Raspberry Pi get too hot. Although I’ve shown the display as

Figure 2 - The Raspberry Pi Computer with a GPS Module attached

www.geo-web.org.uk

5

GEO Quarterly No 40

The Group for Earth Observationwall-mounted above, you may be able to use a VESA adapter tomount the Raspberry Pi card on a monitor, and perhaps, should a
USB port be available on the monitor, use that port to power thecomputer and Wi-Fi dongle.
What does a Raspberry Pi look like?
Figure 2 shows the Raspberry Pi while an experimental GPS
receiver module—which plugs directly into it—was being evaluated.
Working clockwise from the left, you can see the lead to the mouse(just for testing) plugged into the upper USB port, while in the lower
USB port is a compact Edimax Wi-Fi adapter: it’s only just visible
as it’s really tiny. Support for that Wi-Fi adapter (and many others)
is built into the Raspbian Linux supplied. Next, at 12 o’clock, isthe SMA connector for the GPS receiver’s active antenna (I useda magnetic ‘puck’ antenna which provided adequate signal whenplaced near an outside, but north-facing, wall on the top storey of
my house). At two o’clock you can see the 5 V power lead fed intoa micro-USB socket and, just below that, a standard SD card used
for the Linux operating system and other files. At the six o’clock
location you can see the TV video lead plugged into the yellow RCA
jack socket.
The GPS board is a prototype, but all being well you will be able
to buy a similar assembled GPS card and antenna by the time thisarticle appears. See: http://ava.upuaut.net/store/
Setting the Display Size
As the display unit was an analogue TV and not a digital computer
monitor, the scanning parameters required tweaking to get thedisplay to just fill the screen. It was easy to convert an existing
Delphi program for Windows to run on Linux, thereby providing a
testcard to check the screen coverage. The program and its sourcecode are in the Zip download. Setting the overscan parameters is arather fiddly business as a reboot is required after each change, so
progress is not very fast. I ended up with the following changes tothe /boot/config.txt file.
sdtv_mode=2 # PAL systemsdtv_aspect=3 # set 16:9 aspect ratio
overscan_left=-5 # scan margin adjustments
overscan_right=-30
overscan_top=-20
overscan_bottom=-20Your values will be different. For more options please refer to thefollowing web page
http://elinux.org/RPi_config.txt

With the above settings, the indicated display area was 928 x 552
pixels, an aspect ratio of 1.68:1, compared to the theoretical 1.78:1,
and this with a NextBase 10.2-inch 800 x 480 pixel analogue PAL
TV.
Running a Program AutomaticallyOriginally, I had intended to write a screen-saver, so that the digitalclock would be shown when the display was otherwise not in use.
However, I could not find a digital clock screensaver which suited
me—the examples in C which I could find were too complex tomodify quickly, and I could find no examples in my preferred Object
Pascal language. Following helpful discussions with Stefan Enziger,
Jasen Betts and others on the comp.sys.raspberry-pi Usenet
newsgroup (also available on Google Groups), I decided thatmaking a program start automatically from the graphical desktop
would be a better approach (rather like adding a program to the‘Startup’ group in Windows). No-one else would normally be logged
on to the desktop.
Auto Login at boot time
The next step was to make the Raspberry Pi automatically log me
in as a user (at the main desktop) when the Pi was booted. There
are instructions here [2]. In condensed form, they read as follows:
Auto Login: Edit /etc/inittab
Scroll down to: 1:2345:respawn:/sbin/getty 115200 tty1
Change to: #1:2345:respawn:/sbin/getty 115200 tty1
Under that line add:6

December 2013

1:2345:respawn:/bin/login -f pi tty1 </dev/tty1 >/dev/tty1 2>&1
Save the file and exit
[Optional] Install xscreensaver and set one.
[Required] Set to boot to GUI mode with: sudo raspi-config
To check that this has worked, simply reboot the Raspberry Pi andwatch for the desktop to appear on the TV. If you like, you can goa little further and install a package of screensavers, set one with,say, a 1-minute timeout, and check that the screen-saver activatesat one minute past desktop start time. Remember to set the screensaver back to ‘None’ for the wall-clock program, though. To add
screen-savers to your Raspberry Pi, enter the command
apt-get install xscreensaver
and you should now find a new item on the Desktop Preferences
menu => Screensaver.
Running a Program when the Desktop Appears
This is just a little more complex, and involves creating a file to run
the program of your choice. First, if you haven’t already compiled
the program DigitalClock, you will want to extract it from the Zip
archive and make it executable with the command:
chmod +x DigitalClock
On my Raspberry Pi, I had created the directory lazarus within thehome directory (which therefore had the path /home/pi/lazarus), andplaced the DigitalClock program and its source code there. With theFile Manager accessory, you should be able to run the DigitalClockprogram and check that you see something on your display
resembling the photograph shown in figure 1. Move the mouseand click anywhere to end the program. Now you see why I have amouse plugged into the Raspberry Pi.
Creating the Required Autostart File
Unfortunately, it’s not as simple in Linux as on Windows, where
you can just create a shortcut to the program in a Startup directory.
On Raspbian Linux you need to create a file named DigitalClock.
desktop, in the directory .config/autostart under your home directory.
By default, that directory does not exist on a new Raspberry Pi
installation, so you could use the following commands [3] to create it
and make a file to configure the DigitalClock startup:
mkdir ~/.config/autostart
touch ~/.config/autostart/DigitalClock.desktop
You can then edit the contents of the DigitalClock.desktop file - only a
few lines are required:[Desktop Entry]
Name=DigitalClock
Exec=/home/pi/lazarus/DigitalClock
Terminal=False
Type=Application
The line ‘Exec=’ should point to the full path of the DigitalClockexecutable file. If you want to know more about entries in the.desktop file, refer to reference 4.
Compiling the DigitalClock Software
If you want to compile the software, for example should you wantto make some changes to suit your own needs, you will need to
install the FreePascal compiler (fpc), and the Lazarus development
system. It’s not as speedy as Embarcadero’s Delphi on a WindowsPC, but developing a small program like this is perfectly feasible on
the Raspberry Pi. As fpc/Lazarus is also available for Windows, you
could develop and test on Windows (or the Apple Mac), and thentransfer the source for the .pas and .lfm files to the Raspberry Pi.
I ended up creating skeleton applications on the Raspberry Pi,
adding event handlers to the form, and cutting and pasting thecode for the event handlers from my Windows version to the
Raspberry Pi. For these short programs, typing the code in by handis straight-forward enough.
Installing Lazarus
I followed a discussion [5] which led to this most helpful web
page [6], getting a more recent version of Lazarus than that in the

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December 2013

The Group for Earth Observation

default Raspberry Pi Raspbian OS. Thanks to Jack (a.k.a. ‘zog’) forthat page and package. Once installed, Lazarus should appear as
a new entry on the desktop Programming menu. One hint: to keep
the size of the executable down, disable the debug information in
the Project, Options, Compiler, Linking menu. This will reduce thesize of the executable file from 15 MB to around 2 MB.
For help with Lazarus, try this Usenet group:
nntp://news.gmane.org/gmane.comp.ide.lazarus.generalwhich is also available through a mailing list.
How to Test while Developing
My procedure has been this: I log in via an X-Windows server for
Windows (ming) using PuTTY for authentication, and can thus
access the Lazarus IDE, to edit, compile and run the program.
Both PuTTY and ming are free Windows programs for your PC.
This produces output on the X-Windows server running on the PC,
completely separately from any display running on the TV.
I can also be logged in remotely from my PC via SSH to a console
session, and run the graphics program to produce output on the TV
screen by telling the SSH session where to display its output:

GEO Quarterly No 40

You might ask: ‘What else have you done with the Raspberry Pi?’
• I’ve received ADS-B signals on 1.09 GHz with a cheap TV
dongle and fed the results to Plane Plotter over a Wi-Fi link.
This allows me to place the receiver right up close to theantenna, avoiding an expensive (or lossy) length of cable;
indeed, avoiding the need for a cable run at all [8]. It’s notmuch more than following someone else’s instructions, but
at least I can vouch for every command on that page, andperhaps you will find something useful there.
• I’ve built a stratum-1 NTP server with microsecond-level
offsets and a power consumption of less than 4 watts. Thisreference [9] provides information about interfacing a GPS
receiver to the Raspberry Pi, choosing between various
receiver options, and how to compile NTP from the source. I
hope you will find the page interesting, and perhaps build aGPS-locked stratum-1 NTP server yourself.
Acknowledgements
My knowledge of Linux is very limited, but at least I am learning alittle due to my purchase of the Raspberry Pi. This project would
have been impossible without the patient help of folks on various
mailing lists and Usenet newsgroups, to whom I am very grateful.
Offering the following Web page and my software is my way ofactively saying many thanks.

export DISPLAY=:0

http://www.satsignal.eu/ntp/RaspberryPiDigitalClock.html

Thanks to Stefan Enziger for that nugget. Of course, you can’t
overwrite a program which is being actively run by the Raspberry Pi
on the TV, so for that reason you may want to have a separate
copy of the program which you auto-start. I was slightly surprised tofind that even though I had the DigitalClock running via autostart, I
could still run the TestCard program to confirm the resolution figures
I mentioned above.
Future Enhancements
At the moment the screen brightness is fixed. It would be nice tobe able to adjust it live. Also, perhaps for astronomy enthusiasts,
a darker red text on a very dark grey background would be
useful. With low-cost temperature sensors [7], an indoor/outdoor
temperature read-out could be added to the display, or made toalternate with the clock. You have the working source code so ....
it’s over to you now.

Thanks to Rob and Les for their encouragement to publish thisarticle. Let’s hear from you about your experiences with thisdelightful new computer card.
References
1
2
3
4
5
6
7
8
9

http://www.satsignal.eu/ntp/RaspberryPiDigitalClock.zip
http://raspisimon.no-ip.org/rpi_autologin.php
http://www.raspberrypi.org/phpBB3/viewtopic.php?t=18968
http://standards.freedesktop.org/desktop-entry-spec/latest/
http://www.raspberrypi.org/phpBB3/
viewtopic.php?f=34&t=7422&start=75
http://superbitysoft.co.uk/lazberrypi/page13.html
http://learn.adafruit.com/downloads/pdf/adafruits-raspberry-pi-lesson11-ds18b20-temperature-sensing.pdf
http://www.satsignal.eu/Radio/dump1090.html
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

Composite APT Image

Andre T’Kint, a GEO Quarterly
reader based in Belgium, enjoys
creating mosaics of APT images.

The composite image on thispage comes from a sequence of
NOAA-18 images acquired on
September 26 this year.

The image is notable for theunusually large percentage ofcloud on display, but Turkey isclearly visible at lower right andTunisia at lower centre.

At the upper left of the scene,
Greenland stands out sharply in
its own cloud-free oasis.

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The Group for Earth Observation

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December 2013

December 2013

The Group for Earth Observation

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GEO Quarterly No 40

9GEO Quarterly No 40

The Group for Earth Observation

December 2013

Les Hamilton
Sea ice loss in the Arctic Ocean during 2013 rather bucked thetrend of recent years, primarily as a result of a lengthy regime ofrelatively cool and stormy conditions. In contrast with last year,
when the annual minimum extent during the month of September
dropped to a record low (dotted blue line in figure 1), substantiallymore ice remained at summer’s end this year. The Greenland ice
sheet also showed less extensive surface melt while, by contrast,
Antarctic sea ice spread to its greatest recorded extent sincesatellite records began. Figure 1 shows this summer’s minimum
Arctic ice extent, with the pink line representing the 1981 - 2010
median extent for the month of September. For comparison, thedotted blue line outlines 2012’s record September minimum.
Arctic Ocean sea ice annual minimum was reached on
September 13, 2013, and remained largely unchanged until theend of that month when strong autumn cooling started to take hold.
Averaged over the whole of September, Arctic sea ice extent was
5.35 million km2, 1.17 million km2 below the 1981 to 2010 average
but 1.72 million km2 greater than the record low set in 2012. Nonetheless, despite being 47% up on the 2012 figure, this was still thesixth lowest September minimum extent on record. To further set
these figures in context, 10.03 million km2 of sea ice were lost overthe entire summer, between the maximum winter extent last Marchand September.
Figure 2 graphs Arctic Ocean sea ice extent for each year since2008 along with the long-term average. The broad grey band
indicates the two standard deviation range of the mean data.
Contrasting weather conditions were a significant factor in thisyear’s higher sea ice extent and lower Greenland Ice Sheet melt
intensity, compared with last year. Compared with recent years,
this summer was distinctly cool over much of the Arctic Ocean,particularly north of Greenland, with air temperatures at the
925 hPa level 1°C to 3°C lower than in 2012. Also, unusually low
pressure over much of the Arctic Ocean limited heat import fromthe south and created extensive cloud cover that kept temperatures
down. In addition, the winds associated with the low pressurecaused the ice cover to spread out and cover a larger area.
A major factor leading to the loss of multiyear sea ice in recent
years has been its transport into the Beaufort and Chukchi seas,

Figure 1 - Average Arctic sea ice extent during September 2013.
The added dotted blue line indicates the 2012 record minimum.
Credit: National Snow and Ice Data Center

where it has been broken up and exposed to warmer waters
and higher air temperatures. But 2013 was different, the wind
pattern largely holding this older ice into a compact area along theCanadian Archipelago and preventing it from reaching the Beaufort
and Chukchi seas. The cooler conditions this year also helped topreserve more of the first-year ice throughout the summer. The
first-year ice that survived the past summer will now thicken during
autumn and winter to become 2014’s second-year ice.
However, it will require several more cool summers in a row to
restore the sea ice cover to the levels characteristic of the 1980s,
when there was a much larger proportion of thicker, multiyear ice
that proved more resistant to melting during the summers. Andeven though the Arctic sea ice will thicken through this autumn andwinter, its accumulation is still at the mercy of the winds, which
could yet transport some of it out of the Arctic Ocean and into theNorth Atlantic.
Meanwhile, in the Antarctic ...
At the same time that Arctic sea ice was showing signs of recovery,
that in the Antarctic was stretching seawards to a record extent
since satellite records began in 1981: in all, 19.47 million km2 on
September 22. This maximum extent exceeded the long-term mean
by 3.6%, which represents an ice edge 35 kilometers farther northon average. Overall, Antarctic September sea ice extent is currently
increasing at 1.1% per decade. It is suggested that changes inwinds are resulting in greater compaction within the ice pack andmore ridging, resulting in a thickening of the ice which makes it
more resistant to summer melt.

Figure 2 - Average Arctic sea ice extent from 2008 - 2013

SourceInformation in the above has been sourced from the website of the
National Snow and Ice Data Center at

Credit: National Snow and Ice Data Center10

http://nsidc.org/arcticseaicenews/

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Les Hamilton

Map courtesy Wikimedia Commons/Kennonv

Rarely seen because of persistent
cloud and fog, Bolshevik Island(78.6°N, 102.48°E), which lies some
50 kilometres north of Russia’s
Taymyr peninsula, across the
Vilkitsky Strait is the southernmost
and, with an area of 11,270 km2,
second largest island of the Arctic
archipelago of Severnaya Zemlya.
Rising to only 935 metres, theisland is largely mountainous andincludes three glacier systems which
account for almost one third of its
area. The northwestern coastline isindented by a number of fjords but,with an annual average temperatureof -16°C, life is confined to sparse
coastal vegetation consisting of mossand lichen. Apart from an Arctic base
there is no human population.
Severnaya Zemlya was first noted in1913 and first charted in 1930–32,
making it the last archipelago on
Earth to be discovered. This islandgroup has long been the major
obstacle to opening the Northeast
Passage between the Pacific andAtlantic oceans for trade, remaining
firmly in the grip of ice even at theheight of the late summer melt
season. But, with the continued
decadal shrinkage of the permanent
Arctic ice cap, open water is now
often found to the north of thearchipelago.
This summer, history was madewhen the 19 000 tonne Chinese
freighter Yong Shen became the firstship to successfully navigate the5400 kilometre passage when she
docked in Rotterdam on September
10 following a 35-day journey from
China’s northernmost warm-water
port, Dalian (formerly Darien). The
traditional sea route through theThis Terra MODIS image acquired on September 15, 2013 provides a rare glimpse through the cloudy Arctic of Suez Canal and the Mediterranean
Sea takes 48 days.
the triangular, glacier covered Bolshevik Island belonging to the Svernaya Zemlya archipelago.

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GEO Quarterly No 40

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December 2013

Mike Stevens (G4CFZ)
What is the Jet Stream? It is a strongly flowing ribbon of airthat flows around our planet, high up in the atmosphere,
situated between the tropopause and the stratosphere. It’s
exact height above the Earth varies from approximately
11 kilometres at the Poles to 17 kilometres at the equator.
Jet Stream winds typically flow at between 100 and 160 kph.
We often hear weather presenters on TV mentioning the Jet
Stream and how it is responsible for influencing our weather
in the UK, so it is no wonder that we need to know more
about what causes it and why it has such an influence on
the weather we experience at ground level.
Jet Streams form, and are normally seen, in two zones:• the boundary between the polar and mid-latitude air,termed the Polar Jet.
• the boundary between the mid-latitude air and tropicalair, known as the Subtropical Jet.
Although both these Jets are separate entities, they do join
up from time to time across various parts of the Earth.
Jet Streams form near the boundaries of adjacent air masses
with significant differences in temperature, such as the polar
regions and the warmer temperate zones. The Polar Jet isthe stronger as the temperature gradients across polar andmid-latitude regions is greater than those between midlatitudes and the equator. And of course, the temperature
gradient over northern and southern latitudes increases
significantly during the winter months.
Both the Polar Jet and the Subtropical Jet travel fromwest to east, and would do so uniformly were it not forother influencing factors, such as the Coriolis effect, thelandmasses they encounter and the temperature gradients.
Landmasses affect the flow of the Jet Stream throughfriction and temperature differences, while the spinning of
the Earth produces the Coriolis effect, which accentuatesthese changes by causing the Jet Stream to meander above
the Earth just like a river.
Good and Bad
So, understanding this, how and why does the Jet Stream
affect our weather? A simple way to explain this in a mannerthat we can understand is to describe the Jet Stream as
having two sides: a ‘good’ side and a ‘bad’ side. You areon the bad side of the Jet Stream when you are situatednorth of it: this has the effect of pulling in the Atlantic
low pressure areas. Recall the so-called summer of 2012
when it rained from April till October as one low pressure
system followed another. At that time the Jet Stream lay
over northern Spain, meaning that Britain was on its bad
side. Additionally, a very high pressure system had formed
over Scandinavia and this remained stationary for manyweeks, maintaining the Jet Stream in more or less the same
position, at approximately 40°N over Spain.
The good side of the Jet Stream (in the northern hemisphere)
is its southern side. This is where all the good weather andthe high pressure zones are found. The July heat wave of2013, which produced some amazing temperatures within
the British Isles, was so because the Jet Stream was locatedat approximately 60° north latitude, between northern

12

Scotland and Iceland. And it remained there for almost three
weeks, until an Atlantic low pressure area moved in, steeredby the Jet Stream, which then diverted south. This createda trough in the Jet Stream which allowed a southerly airflow
to draw heavy thunderstorms from France over GreatBritain, marking an end to the extreme temperatures. Thissituation continued for several days until the Jet Stream’s
track changed again, bringing more Atlantic lows on to ourshores.
Now you begin to see the influence that the Jet Stream hasover weather in the British Isles. The direction and angle of
the Jet Stream will determine what air flows we experience,
be it warm air, moist or maritime air, or cold air, all of which
greatly influence our weather.
As experienced Earth observers, we are able, with the helpof EUMETCast and its amazing images, to see these fast
moving Jet Streams above us on a daily basis. Once you
have MSG-Data Manager up and running, with images
arriving on your screen at regular intervals, you are capableof detecting these flowing ribbons of air. They produce a
markedly different cloud formation due to the wind speeds
produced at high altitude and are soon easily recognisable
both at ground level and from satellite images.
The images shown in figures 1 and 2 display exactly how
the Atlantic or Polar Jet Stream can change over several
days. On these images, the faster the Jet, the more intense
the red colouring. On July 31 (figure 1), the Jet Stream wasflowing northward over the British Isles, carrying warmer
air from the mid Atlantic across the country. This can bringin moisture on a southwest air flow, which could mean thearrival of a low pressure system, and the chance of rain. But
by August 7 (figure 2), a trough in the Jet Stream lay to thesouth of Britain, which allowed cooler air to penetrate tolower latitudes.
In short, cooler air lies to the North of the Jet Stream andwarmer air to its South. As the Jet Stream constantly
changes its strength and direction, it can affect our weather
quite dramatically.
The Jet Stream in Satellite Images
We can now tie all this information to a Meteosat-10 satellite
image. Figure 3 is a channel-9 10.8 μm infrared image takenfrom my system at 19.15 UT on the same date as figure 1.
If you look carefully, you can see how the cloud pattern inthe satellite image lines up closely with the Jet Stream. Thisalignment provides absolute confirmation as to how the
Jet Stream has such an influence on our weather here at
ground level. Nothing could be clearer than that. Or could it?
One type of travel that benefits from the Jet Stream isaviation. Long haul flights from the USA to Europe can, once
they have located the Jet, save time in travel and costs infuel which, in this day and age, means money saved. To big
companies with huge fuel bills that can be very beneficial.
The down side comes if you are travelling in the reverse
direction: the Jet could in this case make your flight longer
and burn more fuel: so the Atlantic weather forecast can bemost helpful to the aviation industry in avoiding the Jet on
westward journeys.

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Figure 1 - The Jet Stream on July 31, 2013

Figure 2 - The Jet Stream on August 7, 2013

Image: Metcheck

Image: Metcheck

Figure 3 - A Meteosat-10 channel-9 10.8 IR image on July 31, 2013

Figure 4 - A Meteosat-10 channel-9 10.8 IR image on August 7, 2013

Image © EUMETSAT 2013

Image © EUMETSAT 2013

Jet Streams produce strong atmospheric turbulence,
often resulting in long bands of cloud, and with thewinds flowing at some 160 kph, can produce distinctive
narrow trails of cirrus cloud, as shown in figure 4.
This photograph was taken during the STS039 shuttle
mission in 1991, and shows the Jet Stream crossing
above Cape Breton Island in the Maritime Provinces ofEastern Canada.
We, as observers, can see these, and its fun to try anddiscover this weather wonder that is constantly movingaround above us. Many meteorologists around the world
are trying to ascertain what makes the Jet Stream movethe way it does. They now understand about landmass
and temperature gradients, but feel that there are also
other forces in play, making its movement more erratic
and creating such adverse weather conditions as severe
storms and heat waves. It’s even been suggested that
the Arctic ice melt, which has been continuing at an
alarming rate may have something to do with it. Anotherpossible influence could be El-Nino.
But of course, meteorologists do make use of the Jet
Stream to assist with weather forecasting. As I have
explained, it holds most if not all the information as
to what the weather is going to produce, so getting tounderstand this flowing ribbon of air much better could
lead to even more accurate forecasting in the future.
Next time a weather presenter tells you: ‘it’s all to do with
the Jet Stream’, I hope this article will have given you abetter understanding as to how it really does affect ourdaily lives at ground level.
My thanks to Metcheck for the Jet Stream images, and to
EUMETSAT for the Meteosat image.
Happy weather watch from Portland.
Reference Sources
1 Metcheck
http://www.metcheck.com/UK/
2 Wikipedia
http://en.wikipedia.org/wiki/
3 Encyclopedia of Weather & Climate, 2011 Edition.

Figure 4 - The Northern Hemisphere Jet Stream above Cape Breton Island
Image: STS039-601-049 - NASA/JSC

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Raydel Abreu Espinet, CM2ESP -December 2013

Havana, Cuba

email: cm2esp@gmail.com

In the following article we are going to explore some low budget solutions attempted by the author
in order to receive APT imagery. The text is focused on the hardware chain and the reference to thesoftware utilities is made as complement for some of the elements featured on it. A basic knowledgeof the reader regarding the APT format, active frequencies and signal characteristics is assumed.
Antenna
When designing any ground station, one of the key elements
to take into account is the antenna. Choosing one thatmeets your requirements is often a time-consuming problem.
Several considerations about size, ease of construction,materials availability, etc. must be dealt with. About four
years ago, when I first started my APT reception attempts,
the antenna was, initially, the only one I had available, a
145 MHz homebrew Moxon Rectangle [1].
After some months of receiving very limited results dueto the extremely narrow bandwidth of the commercial FMtransceiver used, I had no thoughts of complaining about
the antenna. But when the receiver was upgraded, it became
clear to me that it was time to upgrade the antenna as well.
In the world of APT reception there are two main antenna
types: the phased twin dipole with reflector (turnstile) and thequadrifilar helix (QFH). The QFH is considered by most users
as the better antenna for APT, which is understandable as itis the very same antenna that the satellites use to broadcast
their imagery to Earth. However, as the 145 MHz Moxon did
produce good results, which was considered a point at its
favour, it was also included in this consideration.
When the three candidates were compared, I soon discarded
the turnstile because the Moxon has similar characteristics
and better gain. However, the QFH is quite difficult to build
for a newbie, and it ended not being considered either. So, as
the Moxon came out my winner, some studies were carriedout. Using the simple but excellent free software MoxGen [2],which is easy to find on the Internet, a 137 MHz version of
the Moxon antenna was calculated. Moxons can be phased
to provide circular polarization, and an article published on
the August 2001 QST Magazine (Vol. 85; No. 8; pp. 38-41)
written by L B Cebik (W4RNL) provides a good guide to it.
Initially only one Moxon was built as a test-bed. As theantenna is linearly polarised due to the phase mismatch,a 3 dB loss in signal gain is expected when compared witha pair of phased Moxons, because we are loosing half ofthe signal transmitted by the satellite. If we analyse thebehaviour of the single Moxon scenario with an antennamodelling and analyser tool like MMANA-GAL Basic [3], whichis also free and easy to use, we can decide the best conditions
to locate the Moxon.

Figure 1 - The Moxon Antenna modelled with MoxGen

14

Figure 2
Screen capture of the Moxon gain pattern calculated with MMANA-GAL Basic

When correctly built, the Moxon is a 50 ohm match andprovides around 5.9 dBi on free space. However, if we takea look at figure 2, we can see that the Moxon provides agreat pattern with a nice gain when it is located one meter
above the ground or the roof. Placing the antenna at higher
elevations may increase the gain and improve its line of sight,
but it also deforms the gain pattern due to the appearance offringes and deep nulls which can degrade the received picture
quality badly. A single antenna produces an oval-like pattern,
another reason why two Moxons phased together are better—because the resulting gain pattern has a dome-like form very
similar in shape to the pattern provided by QFH antenna.
The Moxon has a low gain at the horizon and is horizontally
polarised, so it is less sensitive to ground station interference.
Of course this means we loose the lower part of the pass,
but for those living in highly populated areas with buildings
obstructing the horizon, and in-band emitters, it may not bea bad deal at all.
If we want to test APT reception right away in a fast and easy
fashion, a single Moxon is a solid candidate for a beginner’s
antenna. If we correctly align the oval-shape pattern in orderto obtain the maximum in a north-south trajectory (whichpolar orbiting satellites follow), we can achieve a good noisefree signal on every pass with an elevation greater than 30°
whenever the satellite is 10° above the horizon. Just point theantenna’s arms into an east-west alignment. Greater coverage
was achieved with a preamp attached to the antenna, andthis will be discussed later. So, three years later, the socalled ‘test’ antenna is still in use, even after suffering all the
climatic challenges that the Caribbean weather has to offer(figure 5).
PreampA reception preamplifier was obtained a few months ago
and it helped to extend my coverage. It is a Soviet-era
preamplifier, built in East Germany at the mid 1980s, but

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GEO Quarterly No 40

still in good working condition, even after many years of use
and a few more in storage. Only some minor adjustments wererequired. When using long runs of coaxial cable, a preamplifier
is recommended; however, in the several cases where I havetested it, it provided only a small improvement with traditional
receivers and 15 metres of low loss RG-11/U (Belden 8213)
coaxial cable. The convenience or not of using the preamp will
be better discussed later. Whether it is required may well depend
on local conditions, and the level of quality we are looking for in
our images. However, in special conditions it may be a must. The
circuit board of my preamp is shown in figure 6.
Receiver
Now is time to discuss the receiver. In the past four years I
have received APT imagery with three different receivers. My
first receiver was a Kenwood TK-760 FM communicationstransceiver which had a very narrow bandwidth (15 kHz), butwhich nevertheless received some nice pictures (figure 3). Later a
new receiver was obtained, an AOR AR-3000A, which, however,has too much bandwidth, 200 kHz. The Plus (+) version of thisreceiver features a modified Wide-FM filter of only 50 kHz, goodenough for APT imagery, but I own the normal version with thewider filter. Yet, even with the 200 kHz bandwidth, only few issues
were detected in more than two and a half years. The 136-138
MHz band in Cuba is free from ground transmissions so the
only interference that can be picked up by the wider bandwidth
comes mainly from the Orbcomm satellites—especially on the137.560 MHz downlink, when the satellites are in range of groundstations in Florida. This downlink badly affected both NOAA-17(now decommissioned) and NOAA-15, but NOAAs-18 and -19 werereceived without major problems: just some minor noise from time
to time which could be easily be filtered by the ‘Despeckle’ utility
most APT reception software has.
However, the greater a receiver’s bandwidth is in comparison withthe transmitted signal bandwidth, the more energy is required
so, when using the Moxon antenna without a preamplifier, thecoverage was limited to passes greater than 35° when the satellite
was above 15° in order to receive a noise free picture. Using thepreamplifier, the coverage was extended to passes of greater than
30° when the satellite was 10° above the horizon (figure 4). An
even more modern receiver with great features, based on evencheaper technology, will be discussed later.

Figure 3 - A NOAA-19 afternoon pass received with a narrow-band
Kenwood TK-760 Communications TransceiverComputer and Software
For traditional methods, almost every computer is capableof decoding APT imagery as long as it has a soundcard andcompatible APT decoding software. So far, three programs havebeen used for different purposes. An elderly and excellent software
named WXSat [4] is the best choice for very slow, old computers: it
provides all the minimum required options and runs at acceptablespeed even in an Intel 80486 computer. One more bonus, it isfree.
WXtoImg [5] is another great tool that many users prefer. It can beused in three ways: as a free version providing basic features, aregistered version with some improvements and a professionalversion which unlocks all its features. A normal computer isrequired, not extremely fast, but slower computers may produce
lost of sync when recording. Still, WXtoImg has a resync optionthat may help in such cases. This software is capable of producing
acceptable results even with very limited antenna and receiverconditions. So far only the free version was tested but it provides
good results.
Another favourite is David Taylor’s SatSignal [6], which can also be
used also in a free demo version with basic tools or a registeredversion with a lot more improvements. This program may not have
all the fancy options WXtoImg has, but in my personal opinion
the best pictures I have ever seen were obtained with SatSignal,
especially when activating the ‘Larger Image’ and the ‘Wide Input
Filter’. Of course, as it squeezes every single detail from theanalogue APT transmission, a stronger and noise clean signal isessential, otherwise a degraded picture is obtained.

www.geo-web.org.uk

Figure 4 - A NOAA-19 afternoon pass received with the AOR
AR-3000A General Communications Receiver

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December 2013

Figure 5 - The ‘test’ single Moxon is still in use three years after being built

Figure 6 - The Circuit Board of the Author’s preamplifier.

Figure 7
The RTL-SDR EzTV645 dongle and FC0013 tuner
attached to the rear USB ports of the author’s computer.

Figure 8 - A section from the 18:53 UT NOAA 19 pass on July 25, 2013, decoded with RTL-SDR, which clearly shows the author’s homeland, Cuba.

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Figure 9
A NOAA-15 afternoon pass decoded with RTL-SDR. The resulting WAV file was decoded with SatSignal 5.2.2, andalthough sync was lost four times, a good picture was nevertheless obtained. Cuba, however, is completely overcast.

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SatSignal doesn’t feature a self-recording option but this is
not a problem at all as we will see later. Again, only the freeversion has been used so far with no complaints.
There are several other decoding programs for APT andall may work as well, each one with its good features anddrawbacks. However, in your personal scenario you may
choose the one that accomplishes your expectations best.
The Future is Software Defined Radio
Not too long ago, a brand new device appeared which
captured the imagination and the heart of many radio
monitoring enthusiasts: it was the RTL-SDR dongle. For many
years before that, Software Defined Radio was used; however,its prices were prohibitive for most APT beginner users. It was
not until the discovery of the possibility of using some USB
Digital TV receivers—based on the RTL2832U chipset—asradio receivers that SDR technology became affordable tomost people.

avoid overwriting any other USB device’s driver. The RTL-SDR
dongle should be identified as Bulk-In, Interface (Interface 0).
Once the device has been correctly chosen, proceed with the
installation by pressing the ‘Install Driver’ button. With somecomputers it may be required to re-start Windows: even if
this is not requested, it is a good practice to do it. If the driveris correctly installed the device will appear at the USB Safe
Extract icon (Another driver installation window may appear.
This one is for the included Infrared Remote Controller but
can be ignored as it is not required). Figure 10 illustrates
the Zadig driver installation screen, showing that the correct
device has been identified.

Several attempts and experiments on receiving analogue APT
imagery—and even digital data such as LRIT and HRPT—werecarried out by a few users with mixed results. Using a device
designed for receiving television from a powerful transmitterin a scenario of weak signals coming from space in a heavy
RF interference environment is not an easy task.
Many RTL-SDR users report a lot of drawbacks, like ESD(Electro-Static Discharge) sensitive components, de-sensing,overloading, low sensitivity at VHF, need for high computing
resources, etc. However, if we consider that we haveintegrated into a small space an RF Spectrum Analyser andversatile all-mode, free-to-customize receiver, which can bebought by around 20 dollars, it may not look too bad. Manyof its problems can be solved with patience and perseverance.
Adding a couple of diodes will protect it from ESD, a
bandpass filter may help with out-of-band interference, apreamp will improve sensitivity, and so on.
The Ezcap EzTV645 Dongle
The RTL-SDR dongle we are going to explore in the rest of
this article is an Ezcap EzTV645 with an FC0013 tuner coveringfrom 48 MHz to 864 MHz. In order to start using this dongle
we need the proper software and drivers. One of the mostused is the SDR# (pronounced SDR Sharp). During the tests
described here, version 1.0.0.1135 was used. Figure 7 shows
the RTL-SDR and tuner connected to my PC. The originalantenna connector was replaced by a BNC one taken from an
old Ethernet card. A pigtail cable has been used to attach thedongle to the computer’s rear USB ports.
Integrating SDR# with the RTL-SDR DLL libraries may be hard
work, so it is recommended to use an integrated distribution
provided by ‘EA1KR’ which can be downloaded fromhttp://www.divxea.tk

This package comes in both Spanish and English language
versions and features the most used tools and plugins an
RTL-SDR enthusiast will require. It is a ready-to-use solution.
After completing the package’s self-extractor program,we open the folder were we installed it and execute theapplication named SDRSHARP TOOLS UPDATE.exe, which is theStart Menu for the main programs contained in the package.
In order to use our RTL-SDR dongle we must install an SDR
compatible driver, but not the one provided on the original
CD supplied with the dongle. The driver has an install
application named Zadig, which can be accessed via the
Menu Application.
To install the driver it is very important to first connect thedongle to a free USB port. When Windows asks for the driver,close and abort the installation, then run the Zadig program.
It is very important to be sure the correct device is chosen to18

December 2013

Figure 10 - Zadig Driver Installation Screen

Once we have completed the Zadig driver configurationand the plugin’s installation or de-installation, then we run
SDR#. On the SDR front-end selection menu, to the rightof the ‘Play’ button, choose ‘RTL-SDR/USB’. If everything isproperly configured there should be no problem; otherwise
it will produce a message box indicating the device was notdetected. If no error message is shown, click on the ‘Play’button and proceed to adjust the range, speed and contrast of
the waterfall to your own preferences. This so-called ‘waterfall’is the dynamic on-screen spectrum (see figure 12) displaying
the evolution of the radio spectrum with time, with frequency
strength colour-coded.
Many dongles may be quite inaccurate in frequency, around
5 kHz as an average. This problem is due to the poor qualityof the 28.8 MHz quartz crystal used internally. However, thestability seems to be acceptable, so we only need to perform
a frequency correction using an option which SDR# provides.
The best way to do so is using a frequency generator, but if
you don’t have one available, a less precise but neverthelessefficient way is to use a known frequency transmission
for adjustment. However, not every commercial service
transmitter may be as accurate as we expect, so we cancheck for several stations, then calculate the average offset
and elect the best one. Once the selection is made, with thestation tuned, open the front-end configuration window byclicking the button at the left of the VFO (variable frequency
oscillator) indicator. At the bottom of the window there is the‘Frequency Correction’ selection tool which can be increased
or decreased until the VFO frequency displayed matches thereal transmitter frequency. That value may be different whenusing other computers and dongles.
In order to overcome some of the problems RTL-SDR dongles
present with de-sensing and overloading, we may needto adjust the RF gain level. On the test performed here, it
was discovered that both RTL AGC and Tuner AGC on the
RTL-SDR configuration window produced very unsatisfactory
results, so a manual RF Gain is my recommended choice. Of
course, in your environment it may be different, so electing
the option that fits your station best will be required. It was
discovered also that, when choosing positive gain values, the
RTL-SDR produces mixing products and image signals (a copy
signal similar to a harmonic) from strong nearby FM and TV
broadcast stations. The cleanest and most interference freeband was obtained with negative RF Gain, but such an option
attenuates the received signals badly.

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December 2013

The Group for Earth Observation

So, during the test performed here, the best result was
obtained with a preamplifier at the antenna, which may beconsidered essential in some situations. Of course, in anenvironment that suffers high in-band ground interference, apreamp may actually make matters worse. But again, as the136-138 MHz band is free from ground interference in Cuba,
I found no problems when using the preamplifier. In fact,
as the preamplifier attenuates out-of-band signals, it served
both as an amplifier and a band-pass filter. After choosing
a -9.9 dB RF Gain Level with the preamplifier working, no
indication of RTL-SDR produced image signals was seen andstill the satellite’s signals were amplified.

GEO Quarterly No 40

waterfall. Wide-FM mode with 50 kHz was selected andthe decoded audio was fed directly into WXtoImg using the‘Stereo Mix’ setting on the soundcard recording tab to adjust
the audio level to the computer’s requirements. However,an extremely choppy picture was obtained due to computer
slowness. The higher bandwidth, added to the excessive
resolution of the waterfall and the WXtoImg requirements,
forced the microprocessor to run at high rates; so many
samples were being lost and not processed. The audio
sounded perfect, but some short 10 to 50 milliseconds gaps
were present, causing WXtoImg to lose sync quite a lot. The
resulting picture is shown below in Figure 11.

The only interference detected was a medium strength TV
carrier right at 138.0 MHz. However, when using the old
Soviet era preamplifier with analogue receivers like the AOR,
this carrier continued to be detected, so we can conclude
it is the preamplifier which is producing the signal, notthe SDR dongle. As that carrier is far enough from the
NOAA-18 downlink at 137.9125 MHz, when using 50 kHz
or less Wide-FM bandwidth it has no incidence—so it was
ignored, and no correction measures were required. Recently,
another interference signal showed up on the spectrum, at
137.500 MHz, produced by an image signal from a strong
nearby broadcast transmitter at 101.500 MHz. But NOAA-17
is now decommissioned and there is no current satellite on
this frequency that may be affected.
Figure 12 shows the SDR# screen with the software
running at 2.0 Msps bandwidth, selected to show the entire
136-138 MHz band. Several satellite downlinks and instancesof local interference can be seen. From left to right:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)

136.060 Computer generated Carrier
136.200 Computer generated Carrier
136.380 GOES-3 VHF Beacon and its SideBands at ± 33 kHz
136.800 Airplane ACARS
136.885 Steady Carrier (Computer?)
136.975 Airplane ACARS
137.020 Weak Steady Carrier (Computer?)
137.100 NOAA-19 APT
137.500 Image Signal of FM Broadcasting at 101.500 MHz
137.770 NOAA-19 TIP Beacon
137.999 Mix product of a TV NTSC Carrier(The three wide horizontal lines are distant lightning)

When using EA1KR’s SDR package, many plugins are
already included. However, for APT reception we only need
the following two: ‘Satellite Tracker’ and ‘WAV Recording’.
In slow computer environments, disabling other plugins is
recommended but not essential. The Satellite Tracker is notcommonly included, but a version for Orbitron (a free satellite
tracker program) can be downloaded from the SDR# websiteathttp://www.sdrsharp.com

This website also includes an easy step-by-step configuration
tutorial. David Taylor also provides a Satellite Tracker plugincompatible with WXTrack on his website at
http://www.satsignal.eu/software/wxtrack.htm

The tracker plugin is not essential, but greater success wasachieved with it.
If all previous requirements were completed correctly,
SDR# should now be ready for APT reception. A few minor
configurations are pending and may or may not be needed forseveral computer scenarios.
The First APT Trial
When attempting the first APT trial with RTL-SDR, a
1.024 Msps bandwidth was chosen with a 32768-point FFT

Figure 11
An early morning NOAA-15 pass received using
RTL-SDR. The author’s first attempt at reception using
SDR#, this image features many loss of sync issues.

A way to reduce computing resources to a minimum wasneeded. Of course, with the fastest modern computers that
may not be necessary at all, and the setup described above
may work perfectly.
Modifications for Older Slow Computers
In order to achieve good results with slow computers during a
NOAA satellite pass, the RTL bandwidth should be decreased
to 0.25 Msps and the FFT resolution to 512 points: suchsettings affect only the waterfall and cause no degradationof the decoded audio. To reduce even more the computing
resources, the WAV recording plugin of SDR# could be
used. On its tab just select ‘Audio’, with a ‘Sample Format’of ‘16-bit PCM Mono’, and a ‘Sample Rate’ of between 8 and
15 kHz. Press the ‘Record’ button during the satellite passand stop when the signal is too noisy. These steps reduce
the amount of computing resources, which is very usefulwhen using slow computers. However, the generated WAV filesample rate is incompatible with most APT decoding software
so some sort of re-sampling must be done.
The free audio handling tool, Audacity, which can be
downloaded from this URL
http://audacity.sourceforge.net

may be used for this purpose. In order to adjust the sample
rate, open the recorded WAV file in Audacity. The file’s
current sample rate will be shown in the bottom left sectionof the program’s main window. Just edit the number bychanging it to ‘11025’. Optionally, an audio boost may be

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GEO Quarterly No 40

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December 2013

Figure 12 - A Screen Capture showing SDR# in operation

performed with the tool ‘Amplify…’, which you find under the‘Effect’ menu. I used a 15 dB boost with great results but adifferent value—or even no boost at all—may be best withyour setup. Once all the audio post-processing requirements
are completed, save the audio file using the ‘Export’ option
under the ‘File’ menu. Here, be sure to select ‘WAV (Microsoft)
signed 16-bit PCM’ for the file format, complete the saving and
we are ready to go. Now, we can open the saved wave file with
our favourite APT decoding program and process the picture.
In very slow computers there may still be a few samples lost,
but the number shouldy be low enough to decode images
satisfactorily, as shown in figures 8 and 9.
As previously described, a 50 kHz Wide-FM mode was being
used for receiving so far, but if we want to reduce the amountof noise to a minimum and extract the greatest detail fromthe signal as possible, a narrower filter may be required.
During a test, I tried slowly reducing the filter bandwidth
to obtain a better satellite downlink spectrum, and found a
43 kHz filter to be the best. This smaller value may produce
noisy pictures when Doppler compensation is poor due tofactors such as old Keplerian elements or a time mismatch,and frequency compensation was found then to be essential.
This was achieved by using the Satellite Tracker Plugin in
conjunction with Orbitron, otherwise the downlink signal
could fall out of the filter, making the whiter pixels looks
noisy. When using this plugin, it is also essential to performthe dongle frequency correction (described above) to avoid
differences between the frequency tuned by SDR# and the20satellite downlink signal frequency due to the poor quality of
the 28.8 MHz quartz crystal.
Conclusion
In this discussion, we have discussed several low budget
solutions performed by an APT user in Havana, Cuba.
Traditional analogue receivers and new but yet economicalsolutions were explored. Unfortunately there may not bemany more years remaining for APT users, as the evolution oftechnology imposes new digital downlink systems. However,for beginners and low budget stations APT is still an option.
The cheap RTL-SDR dongles may be used for new downlink
formats like LRPT, LRIT, HRIT and HRPT but the decoding
tools are yet to be written or adapted, and new experiments
must be done. Let’s hope more software developers take alook into this fascinating and economical solution.
References
1 Moxon antenna
http://www2.mmae.ucf.edu/wiki/Moxon_antenna
2 MoxGen
http://www.ac6la.com/moxgen1.html
3 MMANA-GAL Basic
http://hamsoft.ca/pages/mmana-gal/
4 WXSathttp://www.hffax.de/html/hauptteil_wxsat.htm
5 WxToImg
http://www.wxtoimg.com/
6 SatSignal
http://www.satsignal.eu/software/satsignal.htm

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December 2013

The Group for Earth Observation

GEO Quarterly No 40

Les Hamilton

A tropical depression that formed over the ocean, northeast of the
Pacific island of Guam in early October 2012 rapidly deepened
to become category-3 Typhoon Papiroon by October 14, withpeak wind intensity of 165 kph. By the time NASA’s Terra satelliteacquired this MODIS image on October 18, Papiroon was winding
down: sustained winds were reduced to 65 kph and the typhoon
had lost the distinct eye and spiral arms it had sported days earlier.
But what makes this image particularly interesting is the formationof Von Karman vortices to the west of Papiroon. Though we think ofocean water and air as completely different materials, they are both
fluids. And when a fluid encounters an obstacle, it can form spiraleddies. The air-flow obstacle responsible for these vortices wasalmost certainly the mountain of Hallasan, which comprises the bulk
of South Korea’s Jeju Island. Hallasan is a Pliocene shield volcano
which, rising to 1950 metres, is South Korea’s highest point. The
volcano is probably extinct, the last recorded eruption from its
flanks being in the year 1007.
In the image above, the spiral eddies extend for over 700
kilometers to the south of the island.

www.geo-web.org.uk

Image: MODIS Rapid Response Team at NASA GSFC
Image processing: SmoothMODIS
Text sources: Wikipedia and NASA Earth Observatory

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December 2013

Les Hamilton

Cyclone Phailin was imaged by China’s Feng Yun 2D geostationary satellite at 04:30 UT on October 12, 2013.
Image: Feng Yun Data Centre at CMA

You would hardly imagine that an innocuous
tropical depression that formed in the Gulfof Thailand on October 4, 2013 would
eventually turn into the strongest cyclone
ever recorded in the Indian Ocean. But
that’s exactly what did happen. It drifted
across the Malay peninsula into theAndaman Sea, gaining strength as it
continued to track northwest over the Bayof Bengal. Five days later it was classed asa Very Severe Cyclonic Storm, equivalent
to a Category-1 hurricane. Named
Phailin (sapphire), the storm continued tointensify and, on October 11, became theequivalent of a Category-5 hurricane, andby the early hours of the following morning
Cyclone Phailin was officially stated to be
the strongest storm ever measured in the
Indian Ocean, and the most severe to hit
the subcontinent since Cyclone Odisha in
1999, when over ten thousand lost theirlives. According to the US Navy’s weather
service, wind speeds at sea were gustingat up to 310 kph and It was feared that thescale of damage caused by Phailin could
exceed that of Hurricane Katrina which hit
New Orleans in 2005. To place this storm incontext, it was twice the size of Superstorm

22

Sandy which devastated the east coast of
America in 2012 [1].
Although Phailin weakened slightly as it
approached the Indian coastline, it still
packed sustained winds of 250 kph when it
made landfall on the shores of Odisha andAndhra Pradesh on October 12. Phailin tore
down power and communication lines andknocked out road and rail links in addition
to flattening thousands of coastal homes,
uprooting trees and overturning cars andtrucks; hundreds of thousands were forced
to flee their homes and spend the nightin makeshift refuges. But the evacuation
effort—said to be the biggest in India’s
history for such an event—kept the death
toll low.
A major difference from fourteen years
ago was that present-day communications
are much better with the proliferation of
cellphones and television, and the arrivalof Phailin was predicted well in advance.
This enabled the authorities to be muchbetter prepared, particularly by setting inmotion the biggest storm evacuation inIndia’s history. Officials in Orissa claimed

www.geo-web.org.uk

that 873,000 people were moved from thecoast to schools, temples and governmentrun shelters before Phailin made landfall,
while over 100,000 more were evacuated in
Andhra Pradesh. As a result the death toll
was just 27, far fewer than had been feared.
It was also fortunate that Phailin hit at low
tide, reducing the effect of its four metrestorm surge.
Phailin left made more than half a million
people homeless, damaged or destroyed
at least quarter of a million buildings, andcaused an estimated loss of $320 million
through the destruction of five thousandsquare kilometres of paddy crops. But there
were tales of good fortune: 28 sailors whose
ship sank in the cyclone were rescued
from the Bay of Bengal. And in anotherremarkable story of survival, 18 fishermentrapped offshore in rough seas abandoned
their trawler as the cyclone approached andsuccessfully swam to shore.
Reference
1 Superstorm Sandy Savages States - GEOQ
36, p.42

December 2013

The Group for Earth Observation

GEO Quarterly No 40

Francis BellFor the second time in the space of just a few months, I was
telephoned by the widow of one of our long standing GEO
members. This time the call was from Joanna Swan, to pass on thesad news relating to the death of her husband Alan.
Alan had been a member of GEO since our group was establishedin 2004 and was very supportive of our activities, together withhis own live home live reception of weather satellites. During myconversations with Joanna, I learned of Alan’s early work with thereception of UoSATs 1 and 2 (Oscars 9 and 11) as well as the early
NOAA satellites and Meteosat. Joanna remembered visits to Surrey
University’s campus and its ground station in the early 1980s, at thetime when the university was becoming innovative in the productionof low-cost satellites. We agreed that those early days, with theskills which they developed, lead to the establishment of today’s
very successful company, Surrey Satellite Technology (SSTL).
Over the telephone, Joanna explained that Alan had left large
quantities of satellite equipment and she wanted, if possible,that these items should go to a good home. After some delay
I personally visited her home and tried to assess the best way
to dispose of the many items Alan had left. I brought some ofthese away, together with 13 years worth of RIG Journals. Where
possible, I have found most of these items good homes; however,
one item I still have left is a Mitsubishi Video Printer model P55B. I
cannot quite date this printer, but it must date to some time during
the early 1980s. I know these printers were used in the early daysof weather satellite reception, before the advent of home computers
and the electronic storage of images.

Figure 1
The Mitsubishi printer and monitor, which Alan Swan used during the 1980s.

Figure 1 shows a photograph of this video printer and figures 2
and 3 show two scans of typical images which it produced. I would
be disappointed to see this item scrapped but have no use for it
myself. If any GEO member would like to have this video printer—or indeed knows of any other club member who would—either for

Figure 3
This is an image printed on the Mitsubshi printer, and illustrates theway in which EUMETSAT communicated with its user community
in those days. The date on the print (1988) reveals that this was
before the widespread use of the Internet, which EUMETSAT use
today for such messages. Note that although the very left of theimage is missing from this print, the message still makes sense.

personal use or for a museum-type collection, please get in touchwith me at
francis@geo-web.org.uk
Figure 2
This is an image transmitted by Meteosat-2 on July 30, 1988 and printed
on Alan Swan’s Mitsubshi printer. In those early days, a visible image of the
Earth was taken every 30 minutes, but processing by the ground station
would divide the original image into many sections including nine standard
resolution visible sections ready for general dissemination. Section number
two in this group is shown above. These images were sent via a transponder
on the imaging satellite, unlike today where images are disseminated via a
different commercial satellite using a different transmission standard (DVB).

There would be no cost except for the carriage.
GEO will miss Alan Swan. In addition to his early amateur workon weather satellite reception, and his keeping up to date in thefollowing years, Alan had a distinguished professional career with
BOC as an overseas engineering manager. I hope that some of hiselectrical and astronomical instruments find suitable homes, andwhere appropriate continue to be used.

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December 2013

Francis BellI was delighted to be invited—on behalf of GEO—to aSpacelink Learning Foundation meeting at Broadwater School
last July, where I made a presentation to the attending
school students and provided a stand running live weather
satellite images. Last December GEO provided Spacelinkwith a one-page flyer for its member schools, relating todirect weather satellite reception. The flyer was illustrated
by current NOAA and EUMETCast images, together witha brief summary of the equipment needed for live satellite
reception. Feedback indicated that this information was wellreceived, but the numbers actually installing a receiving
station in their school is unknown—but at least they havethe information.
My relations with Spacelink go back to the mid 1990s
when I started the Millennium Satellite Project. This had
the aim of launching a UK-built satellite dedicated toschool interests, to provide easy access to Earth images,
international communications and scientific data. The
project was intended to be 50% funded by the Millennium
Commission, in the belief that NASA would provide a freelaunch as a secondary payload with a commercial satellite.
But after about two years the Millennium Commission shortsightedly turned down the project leaving it rather stranded.
As a consequence, my educational efforts were redirected
towards schools using existing satellite missions to sustain
or generate educational interests in space science. However,other members of my group continued with the project andsubsequently founded the Spacelink Learning Foundation,
which still runs today.
I was told to expect an attendance of some 12 schools, eachbringing about ten students aged 10-16, and I planned
equipment and displays which I thought would be appealing
and appropriate for this age group. These included live
EUMETCast reception and sequences of diverse recorded
satellite images, along with a stand displaying GEO literatureand posters kindly provided by EUMETSAT.

GEO’s stand ready to receive visitors.

I was particularly interested to hear Helen Sharman’spresentation and renew my friendship with her after a gapof almost 20 years. Helen was the first British cosmonautwhen she spent eight days on the Russian MIR space stationin May 1991. During her time on MIR there were planned
amateur radio links with UK schools. My own school, theRoyal Grammar School, Guildford, was allocated a slot in the
MIR schedules and issued with the callsign GB7JUNO. At
that time I followed events closely and had the privilege of,opportunistically, being the first amateur station to talk to
Helen (using the callsign GB7JUNO) while the space station
was crossing over the UK.
After her return to Earth, I was so pleased when Helen
accepted my invitation to visit the Royal Grammar
School. After several visits Helen became supportive of myMillennium Satellite programme, and subsequently thefollow-on Spacelink Foundation, of which she is now patron.

Students assemble for the formal presentations.

The day went according to plan, and featured a number ofpresentations given by leading space scientists.
The main programme included:• ‘Living in Space’ by Dr Helen Sharman, the first UK
woman in space• ‘The Sun Seen from Space’ by Dr Lucie Green of
the Mullard Space Laboratory, who is often seencontributing to space and science related programmes
on TV. She is a trustee of Spacelink• ‘Saturn and its Moons’ by Shelia Kanani, a member of theSpacelink management team.

24

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Cosmonaut Helen Sharman pictured with Francis Bell.

December 2013

The Group for Earth Observation

GEO Quarterly No 40

In the past the NSC, with its high profile space exhibition area, has
proved to be a popular venue for some of GEO’s annual meetings.
We hope the 2014 symposium there will be well supported by ourmembers, friends and other interested visitors.

Dr Lucie Green of MSSL pictured with GEO
Membership Secretary David Anderson.

Helen came over to see the GEO stand, and I think she
was impressed to see what we were doing towards enabling
schools the opportunity to run their own satellite station.
Later in the day, and equally satisfyingly, Lucie Green also
visited the GEO stand. In both cases I gave them recent
copies of GEO Quarterly plus other informative literature.
Between the presentations, students visited the various
stands located in the hall. I was impressed with the genuineinterest that they showed when visiting the GEO stand, andin return I gave brief presentations about weather satellites,
their history and how to receive images at home or at school.
The students all departed with literature and the EUMETSAT
posters showing whole Earth images.

The coming Symposium is particularly important because of thetechnical issues relating the EUMETCast transmission changes many of
us will face in the next 18 months. An important objective for thismeeting is to keep members informed about, and offer practicalinformation and demonstrations relating to, the upgrading of the
EUMETCast Europe Service from DVB-S to the DVB-S2 standard.
The Saturday programme will be along the following lines:• 9.00 - Arrival and registration• 9.30 - 12.30: Presentations• 12.30 - 2.00: Lunch and viewing the NSC exhibition areas• 2.00 - 4.00: Presentations• 4.00 - 4.30: Afternoon break• 4.30 - 5.00: GEO Membership AGM

Others stands in the hall were provided by:• ESERO and their UK ‘Space Education Office’• SSTL (Surrey Satellite Technology Limited)• MSSL (Mullard Space Science Laboratory)• STEMNET (Science, Technology, Engineering andMathematics Network)• Kingston University Aerospace Engineering Department

The programme is not finalised at this time, but we already have acommitment from EUMETSAT to provide us with a technical speaker
relating to the new EUMETCast dissemination standard.

I have seen feedback from the visiting schools, and all said
what a rewarding and interesting day they had experienced. I
hope that GEO contributed in some way to their satisfaction.

Other topics to be covered could include results from the GERB
instrument being carried on the MSG satellites and the use ofsoftware defined radio (SDR) for polar orbiting satellite reception.

Those involved in setting up the exhibition and demonstration area
for the Symposium will be able to do so on the Friday afternoon.

My specific thanks to David Anderson who helped with all
the GEO activities, spending two days of his time to be at theevent.
For further information on the Spacelink Learning
Foundation, visit their website at
http://www. spacelink.org

Any member wishing to make a contribution, be it apresentation, a suggestion for a topic to be coveredor a workshop for the exhibition and demonstrationarea, is invited to get in touch with Francis Bell at
francis@geo-web.org.uk

The cost for this one day symposium will depend on numbers
attending but should be in the range £15 - £20. Note this fee
includes free car parking and a free pass into the NSC exhibition:
good value for money.
Fuller details of the programme, which will include information on
pre-registration, will appear in the March 2014 GEO Quarterly, andon the Group’s website at
http://www.geo-web.org.uk/symposium.php
Francis Bell, with students from a Cranleighschool who visited the GEO stand.

But in the meantime, do write the date, April 26, 2014, into your diary.

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December 2013

Alistair Dunlop
A previous article [1] has covered the reception of weather satellite
images when away from home. Sooner or later, most weather
observers will want to predict the weather; if only to satisfy thefamily cry: ‘I know what it’s done, what is it going to do?’. Whilst
this is easily explored using the Internet, forecasting presents more
problems away from home. Assuming that you are not preparedto spend large sums on mobile Internet, this article describes one
source of wireless data that is free, and which can help to indicate
future weather trends even for the nonexpert.
Many articles have appeared in GEO Quarterly by Peter Wakelin
and others on the interpretation of weather images, and this article
does not pretend to cover this in detail. It is intended to be a roughoutline of the process only. Forecasting generally needs additional
data over and above a received image. This usually takes two
forms: first, the synoptic pressure chart with contour lines of
constant pressure known as ‘isobars’, frequently with weather fronts
added; and secondly, winds at altitude—usually at a pressure of
800 millibars or thereabouts. The pressure charts are reasonably
familiar from TV and other weather forecasts; the pressure drives
the winds and frontal systems are usually indicated, so this typeof chart is perhaps more useful for the nonexpert and easier tointerpret than the wind charts, although the winds at altitude areperhaps more useful for detailed forecasting.
Before the satellite era, raw weather data were gathered byweather ships out at sea and from meteorological aircraft as well
as a number of land-based meteorological stations. These data
were then used to produce the various charts which were broadcast
to distant stations using a form of facsimile transmitted in the
short-wave radio bands. These transmissions still continue today,even though much of the meteorological information is gatheredby satellites, and completed charts are disseminated in the samemanner. The major advantage of weather facsimile broadcasts(usually abbreviated as weatherfax or wefax) is that they can bereceived on a simple short-wave receiver and decoded using
readily available computer software.
There is a flourishing market for this system for yachts, fishingboats and other small craft sailing away from coastal waters. The
basic requirements are simple—a short-wave receiver with aerial
and a computer to decode the information. Figure 1 is a typicalsurface chart as received in a suburban area; as can be seen, it
has significant noise. You should be able to do better when wellaway from houses [2] but even so, the main weather fronts andareas of high and low pressure can be related to the main landmasses.
Short-Wave Reception
The short-wave band, also known as the High Frequency (HF)
band, lies between 3 MHz and 30 MHz. To receive wefax signals,
the radio must be capable of Single Side-Band (SSB) reception. As
not all short-wave radios can do this, look for the specific claim of
SSB reception; if the specification only states ‘short waves’, thisusually means that it will only receive amplitude-modulated (AM)programmes used by major broadcasters such as the BBC World
Service. Additionally, the radio should be capable of fine-tuning
across the frequencies of interest. Most radios have a main tuning
system, usually synthesised, which tunes in fixed steps, with asecond fine-tuning control for intermediate frequencies. For wefax
reception, you require the ability to tune in main steps of 1 kHz or
less. Some receivers only tune in 5 kHz steps in the short-wave
bands; whilst this is adequate for the AM broadcasters, it makes
fine-tuning for SSB reception difficult since the fine-tune control
must cover ±5 kHz or more and you need to tune to an accuracy ofat least 100 Hz.

26

Figure 1 - A typical weather facsimile chart.

Every receiver needs a good aerial system. For reception ofreasonably powerful wefax, a wire aerial of around 3 meters or so
is usually adequate. Ideally, this should be as high as possible andas far away as possible from sources of interference such as mains
leads and computers. In built-up areas, the set-mounted telescopic
aerial is usually too prone to interference to be useful although it
may be adequate well away from civilisation. Too long an aerial
may give the problem of too much interfering signal level, leading tooverload; try different aerial lengths if you have reception problems.
Connection to the computer is easy, using a suitable stereo ormono miniature audio jack-plug cable from the receiver output(headphones, tape outlet etc.) to the computer line-in or microphone
input. Check and adjust the audio levels, particularly if you areusing the microphone input on a laptop. The software you use will
have some way of indicating overload but it is possible to totallyoverload some microphone inputs to such an extent that it appears
that no signal is being received. This has caused me confusion in
the past. Note that SDRs are already using the computer, so thesesystems require either a second soundcard or a utility such as‘Virtual Audio Cable’ [3] to transfer data streams between programs.
Frequencies
There are several guides to the frequencies used for wefax
transmissions. One of the most comprehensive is the US
Coastguard [4], which covers the world but may not be up to date.
It was dated February 2012 when I last looked. However, thesefrequencies rarely change, although the transmission schedule ofwhen charts are transmitted may alter with the seasons.
In Europe, the two main broadcasters are the German Weather Service
based in Hamburg and the British Royal Navy based at Northwood(note that the transmitters may be some distance from these actual
locations). Both of these stations transmit a whole range of weather
charts—Hamburg even covers ice conditions in the Baltic Sea,should you be sailing there in winter. The main frequencies used
are shown in Table 1.
Hamburg also broadcasts the transmission schedule at 11:11 UT
which is a useful guide to all of the charts transmitted.
Hamburg Weather

Northwood

3855 kHz2618.5 kHz (20:00 to 06:00 UT)

7880 kHz4610 kHz

13 882.5 kHz

8040 kHzwww.geo-web.org.uk

11 086.5 kHz (06:00 to 20:00 UT)Table 1 - The main European weatherfax frequencies.

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All three frequencies are continually used for Hamburg but
generally I have found only the lower two (3855 and 7880) to bereadily receivable in the UK. I have found that generally only the
middle two of the Northwood frequencies are readily receivable in
the UK. In all cases, the receiver should be set on USB and tuned
approximately 1.5 to 2 kHz below the frequency shown—this will
be indicated as 2 kHz low (i.e. 3853 for Hamburg) if the set tunes
in 1-kHz steps. Fine tuning can be carried out once a signal isreceived.
Decoding
There are several programs capable of decoding wefax
transmissions. Old favourites such as Wxsat and JVComm32
will decode both weather satellite APT signals and HF wefax. A
more modern program is Fldigi [5], which will decode almost any
Amateur Radio transmission and wefax, but not APT at present.
This is a modern program with a number of add-ons designed toreduce noise and so on. Having said that, it is fairly intuitive to
use provided you configure the soundcard properly. In all cases,
the usual setting is HF-Fax or Wefax, IOC 576 and 120 lines per
minute. This will usually come up automatically but may needchecking if the resulting weather chart looks odd. You will almost
certainly need to adjust the slant setting in order to produce verticaledges on the chart—always read the manual for whatever software you areusing.
The wefax signal itself sounds like a chirrupy tone (not unlike APT)
when a chart is being sent, and a single tone or no signal whennot. It consists of two tones, one for black and one for white, andthese alternate so that the spectrum displays two peaks. All the
programs I am aware of show the spectrum of the received signal
with two tuning markers on the screen; with earlier programs (e.g.
JVcomm32) you have to fine-tune the radio to line up the received
signal peaks with these markers. Lining up the signal peaks
accurately with the markers is important for good results, hence
the need for a smooth, slow fine tuning control. With Fldigi, you
can move the signal markers with the computer mouse, so finetuning of the receiver is less important. Fldigi also has a reasonably
good Automatic Frequency Control (AFC) which will lock on to
the relevant tones if they are somewhere in the receiver audio
passband, but this process can become confused with particular
types of interference. The wefax signal has specific start and stop
tones which have a characteristic buzz; the programs detect thisto stop and start chart recording so you can leave the system on
automatic mode waiting for the next chart. JVComm32 lets you set
up specified recording times so you don’t have to record everything
to get the chart you want, nor sit up all night in waiting by theon-off switch. But all programs will record all received charts ina specified memory folder and it’s simple to delete the unwanted
ones. It is also possible to record to a tape-recorder and decode
later by playback into the computer; this method avoids keeping thecomputer powered up all the time but does depend on the recorderand tape quality.
Weather Charts
The wefax transmissions include a wide variety of charts, only
some of which are useful for our purposes. In between these charts
are many other more specialised ones. Note that chart content andtiming may vary, so do check with the transmission schedule. In my
experience, Northwood frequently changes the timing and content
of transmissions while Hamburg Weather keeps to its publishedschedule. The most useful charts are the Surface Analysis and theSurface Prognosis ones. The former contains the surface pressureisobars and contributing weather
Surface
Surfacestation observations at a particular
Analysis
Prognosis
time, usually 06:00 or thereabouts.
The chart itself is somewhat cluttered
T+24
T+48
as it contains a large number of
07:43
07:17
07:30
individual numbers as well as the
11:45
12:05
12:20
derived isobars. The latter show thepredicted surface isobars for 1, 2 or
18:00
18:34
18:47
3 days ahead, which help to forecast
Table 2
future weather. Hamburg Weathertransmits many charts but some of the Useful Analysis and Prognosis
Transmissions (all in UT)GEO Quarterly No 40

most useful sequences are shown in Table 2 (all times in UT). It
also broadcasts the transmission schedule at 11:11 UT which is a
useful guide to all of the charts transmitted.
Depending on the aerial system used, the local level of interference
and the time of day, there will be more or less noise on the received
chart. Usually, the lower frequencies are better at dawn and dusk
and the higher ones better during the day, but a quick check willshow you what is best for your location. At certain times andlocations the chart may display a pale ‘ghost’ copy, shifted a little
to one side: this is caused by the radio signal arriving first by theground wave then, a little later, via reflection from the ionosphere.
Interpretation
A few basic notes on interpreting the charts. High pressure areas(‘H’ on all charts) generally indicate settled weather, usually sunny
and warm with clear skies in summer. Low pressure areas (‘L’on Northwood, ‘T’ on German charts) usually denote unsettled
weather. Close pressure lines (isobars) mean strong winds whichblow from High to Low pressure. In the northern hemisphere, theCoriolis effect causes these winds to spiral out clockwise from Highpressure areas and spiral in counter-clockwise to Low pressure
areas. Weather generally travels in the direction of upper levelwinds, so identification of Highs and Lows tells you roughly in which
direction the weather is travelling: the closeness of the isobars tells
you how fast, and the fronts usually denote cloud and probably rain.
Note that accurate weather forecasting is significantly more
complicated than described above. There are many excellent books
and articles on the subject if you wish to go into it in more depth.

This infrared APT image 15:50 UT on August 24, 2013 while thesurface prognosis chart in figure 1 relates to 06:00 UT the following
morning. Weather charts are based on various conical projections
so won’t overlay on APT images without some extra geometric
processing, but it is usually possible to cross-reference specificfeatures such as fronts, Highs and Lows by eye. In this case, the‘hook’ of clouds seen southeast of the UK in the APT image roughly
corresponds with a Low pressure area. The surface prognosis in
the wefax chart shows this remaining more or less stationary while
the associated front over France is reducing in strength under the
influence of High pressure to the southwest. This would imply cloud
giving way to sunshine in the west of the UK although, as the front
was predicted to remain over the southeast, it would remain cloudy
there. The High pressure area has widely-spaced isobars, so winds
are likely to be light and will spiral outwards clockwise, then anti-

www.geo-web.org.uk

concluded on page 42

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December 2013

Les Hamilton
Did you know that near real-time imagery
from China’s Feng Yun 2D and Feng Yun 2E
geostationary satellites is available for freedownload from the Fengyun Satellite Data
Center (FSDC). The URL for this page is
http://satellite.cma.gov.cn/

Registration
As with most sites of this kind you have firstto register, though there is no charge for doing
so. On first visiting the site, you will notice theSign In/Sign Up panel at top right (figure 1). Clickon ‘Sign Up’ to open a new page featuring thepanel shown in figure 3. Complete the fields,
including both a username and password of
your own choice, then tick the ‘I accept box’and click the Sign Up Button at the foot of thepage (not shown in figure 3). You should now
be able to log into the website by entering the
Figure 1 - The Sign In Panel
Username and Password you selected. Be surealso to enter the four character verification
code into the field provided. If you tick the ‘Stay Signed In’box, you will not need to enter these details again to accessthe site (figure 2). This now entitles you to the basic service ofdownloading 500 MB of data per day.
Available Imagery
When you sign in to the Fengyun Satellite Data Center
website, the middle panel at the top of the page provides
access to the data from numerous satellites, by default fromthe Chinese low-Earth orbiting craft (FY-LEO). To access datafrom the geostationary Feng Yun 2 craft, select the FY-GEO
panel (figure 4). The available satellites are FY-2D, FY-2E
and FY-2F. FY-2C is also offered but only for historical dataprior to satellite’s decommissioning in early 2009. At present
the most recent satellite, FY-2F, is mainly concerned with
RSS operations, so what follows relates to FY-2D at 86.5°W
and FY-2E at 104°W, the satellites that produce regular
Normalized Geostationary Projection VISSR data. This supplied as
205 MB HDF files, each containing five channels of full-Earthimagery: four in the infrared and one in the visible. The fiveimages measure 2750 pixels square and have a resolutionof 5 km/pixel. Additionally, each file also includes a highdefinition version of the visible image that measures 11000
pixels square and has a ground resolution of 1.25 km/pixel.

Figure 3 - The required Sign Up information panel

Ordering FY-2 Files from FSDCFirst, from the tick-boxes that appear at the top of figure 4,
check the satellite you are interested in. Next, click the mousein the Data Name field (initially blank), and when the ‘Select’panel opens, click on the Visible and Infrared Spin-Scan Radiometer
option.
Next, select a Start Date and End Date, which should be thesame if you have a specific day in mind (usually, I would
imagine, the current date). Clicking on either data fieldreveals a pop-up calendar where you can choose the datewith a mouse-click (figure 5). As for time, the sun is overhead
in China at around 05:00 UT, so a selection of a few hours
centred on this time provides the best illuminated images.
Finally, click the Search Button to reveal a new page listing28

Figure 2 - Signing in to FSDC

Figure 4 - The default Selection Panel for FY-2 satellites

the available passes withinyour selected time span
(figure 6). If you click on
the small square icon in thethird column, you can checka quickview of the selected
image before downloading it.

www.geo-web.org.uk

All you need do now is tocheck the tick-box against
the file you require and click
the Add to Cart Button.
The next screen allows you toedit the contents of your cart

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GEO Quarterly No 40

if need be, but if you know what you are doing you will more
likely just click the ‘Next’ button at this point, which submits
your order.
Recovering Ordered Files
A few minutes after ordering a file, you will receive an email
containing a link that will allow you to download your file(s)by FTP fromfy3-ftp.cma.gov.cn

My FTP software refuses to recognise this, though this may
well be due to my own shortcomings in understanding how toeffect this.
What I have found to be the best and simplest way to recover
files is via the MyOrders option on the menu bar at the topof each page of the FSDC website. Click this to open a listof your ordered files (figure 7). Note particularly the final
Download column; when the link appears here, click it tomove on to the final page containing the direct download link
for the file. After the wait of five minutes or so before yourdownload becomes active, refresh your browser to display
it—or reload the browser.

Figure 5 - Selecting download parameters

Displaying FY-2 Geostationary Images
Many EUMETCast users already possess software that can
open the Feng Yun-2 HDF files and display its imagery: it isDavid Taylor’s GeoSatSignal (registered version only). From
the File menu, select Open one, navigate to the HDF file, anddouble-click on it. GeoSatSignal has tabs for displaying the• channel-1 thermal infrared image• channel-3 water vapour image• channel-5 visible light image• channels 1+5 false colour image
There is also a tab for remapping a selected area of the image
into a variety of projections (orthographic, Mercator, etc).
The latest version of GeoSatSignal can be downloaded fromhttp://www.satsignal.eu/software/geosatsignal.htm

If you are not a registered user of GeoSatSignal, there is afreeware alternative that I have compiled for my own use,
FY2-HDFReader. This program loads FY-2 HDF files anddisplays all five channels (channel-2 is almost identical withchannel-1 while channel-4 contains imagery on an alternative

Figure 6 - List of available FY-2 passes

Figure 7 - The browser link for downloading the HDF files

infrared frequency). On the processing side, there are far
fewer options than with GeoSatSignal, but there are limited
functions which provide control over gamma and gain, as well
as a few very basic colour palette options. You can download
the installation package for FY2-HDFReader fromhttp://myweb.tiscali.co.uk/wxsatellite/soft/fy2-hdfreader-setup.exe

An example of the imaging capabilities of the Feng Yun-2
satellites can be seen on page 22, which shows just a small
Concluded on page 42

Figure 8 - The default channel-5 tab of FY2-HDF Reader, showing the
04:30 UT visible image captured by Feng Yun-2F on October 11, 2013.

Figure 9 - The same Feng Yun-2F image displayed in
the False Colour tab of GeoSatSignal

Image: Feng Yun Data Centre at CMA (http://satellite.cma.gov.cn)

Image: Feng Yun Data Centre at CMA (http://satellite.cma.gov.cn)

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December 2013

Alastair Dunlop
The short-wave bands from 1.6 MHz (megahertz) to 30 MHz
contain several transmissions of interest to weather watchers.
Chief amongst these are weather facsimile [1] (weatherfax or wefax)
transmissions of various meteorological charts which are covered
separately in the article on page 28. Other transmissions of interest
are the NAVTEX [2] broadcasts in the medium-wave, primarily at
518 kHz (kilohertz) but also locally around 490 kHz. Whatever
your interest, you will need some form of short-wave receiver. This
article is intended as a simple introduction to suitable receivers.
You can pay anywhere from £50 to £500 or more for a short-wave
radio. Wefax and Navtex are transmitted at a reasonable power
level, so are relatively easy to receive, hence receivers at thecheaper end of this scale are usually fully adequate. The more
expensive receivers are only necessary if you want to receive lowpower transmissions in the presence of high-level interference. The
extra cost comes in the form of high dynamic range front-ends andsteep-sided filters— very similar to the way pager interference isrejected in APT receivers. Short-wave receivers fall roughly into
four main types: portable multi-band radios which can receive themain broadcast bands, wide-band scanning radios, dedicated shortwave receivers, and Software-Defined Radios (SDRs) often in theform of computer ‘dongles’.
Multi-Band Receivers
These receivers are usually about the size of a paperback book ora bit larger. They usually receive the Long and Medium Wavebands
and the VHF broadcast band. The ones we are interested in also
receive the shortwave bands—make sure that the specification
mentions Single Side-Band (SSB) reception. There are several
Far Eastern radios at reasonable prices—I have heard good things
about the Eton G5 series but have not used them personally.
Sony no longer makes this sort of radio but models such as the
SW 7600G and SW 7600GR (figure 1) are sometimes available
second-hand and from my personal experience are excellent forthis purpose. Don’t use the earlier 7600D model since this tunes in
5 kHz steps and in my experience is extremely tricky to fine tune to
the required accuracy on SSB.

Figure 1 - The Sony SW 7600GR Multiband Receiver

Scanning Radios
These receivers are designed to rapidly scan a range of
frequencies, usually in the VHF bands. A typical example isshown in figure 2. Very few of them can receive SSB signals inthe short-wave band and thosethat do usually have inadequate
selectivity and stability for longterm recording of data signals.
Not recommended unless you
have the technical know-how
to interpret the specifications
Figure 2 - A scanning radio
properly.
Dedicated Short-Wave Receiver
These radios are typically about the size of a car radio or a
bit larger, usually with controls and displays on the front and30

connections for aerials etc. on the back. Many are designed for 12
volt power, which is helpful when using from a campervan or boat.
They are generally purpose-designed for the task but have higher
performance than needed for wefax reception—this is usuallyreflected in a higher price. The Target HF3 series are specificallydesigned for wefax reception in small boats. They are simple but
adequate and cost around £200 new: perhaps half of this secondhand depending on age and condition. You may also come acrossthe Radio Shack/Realistic DX 394 receiver, which is also adequate,
but in my opinion not as nice or easy to use as the Target HF3.
Second-hand models from manufacturers such as Lowe and Icom
can be good value but are often considered as ‘collectables’ withridiculously high prices on auction sites such as eBay. Figure 3
shows an Icom IC-706 transceiver but is generally representative of
this class of radio.

Figure 3 - The Icom IC-70c Transceiver

Software Defined Radios
These radios use digital sampling at an early stage in the receiver
followed by computer processing of the sampled radio frequency to
decode the signal of interest. They can provide good performanceat relatively low cost and are usually extremely versatile, sincepractically any signal can be demodulated. The downside is theneed for a fast computer to handle all the processing involved.
Since the computer is intimately involved with the radio, you
usually need either a second sound card or a utility such as
Virtual Audio Cable to transfer the digital numbers from the radio
control program to the input of your wefax decoding software. The
Fun-Cube Dongle Pro Plus, at around £150 (figure 4) appears
very promising and, on paper at least, looks able to receive bothweather satellite APT signals andshortwave wefax signals, although
not at the same time. This area is awork in progress—see other articles
in GEO Quarterly. The short cableseen below the dongle converts
the SMA connector on the dongle
to a BNC aerial lead, as mentioned
Figure 4 - The Fun-Cube Dongle
in Rod Alblas’s article in GEO
Quarterly 37. The flexible cable reduces any strain on the dongle
aerial connection. Note that the Radio/TV dongle described by Rob
is not generally capable of short-wave reception.
Conclusion
As with many things, try before buying if at all possible. Get to know
your friendly neighbourhood Amateur Radio enthusiast if there isone. However, remember that many enthusiasts love technology,
specifications and high-end kit, whether its cars or radios. Buy
something simple and cheap at first and, when you have theexperience, you will know whether you wish to go further or giveit up. Finally, take the extra effort to drape 3 metres or so of aerial
wire out of the window or even around the room—it will usuallytransform the received signal compared with an in-built aerial. Good
listening and I hope you enjoy the experience.
References
1 http://en.wikipedia.org/wiki/Radiofax
2 http://en.wikipedia.org/wiki/Navtex

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James Brown
I was keen to explore what other folk were doing and had an
invitation from Dr Andrew Eccleston of the Met Office researchlab at the Royal Signals and Radar Establishment in Malvern.
They operated a Primary Data User (PDUS) station designed andsupplied by the folk at Dundee and using PDP 11/34 minicomputers
for display. They were also overlaying radar images—obtained fromtheir own radar station—on the PDUS images. Figure 1 is a sample
that they kindly let me take away with me. Very different from theimages we are used to today, but bear in mind that this was 1982.
I also offered a short article to Weather, which is a journal of theRoyal Meteorological Society. This was taken up and publishedin December 1982, and subsequently gained the James Patton
Memorial Prize.
Others were also realising that a number of us had been working
along similar lines. Folk like Bob Sansoni of York had use of a
University of Bradford PDUS station, and after a couple of visits
we became firm friends. I was even permitted a short loan of theequipment to see what my own dish was capable of.
Slowly the computer era was opening up. A Sinclair ZX Spectrum
provided my first foray into computing, but then the ubiquitous
BBC B microcomputer came along. It was a relatively expensive
item, but a friend of mine worked in the factory where the boards
for this and the later BBC ADSL ‘Master’ version were being
manufactured. Every day a number of boards failed the production
test, and were discarded for either recycling or, if possible, repair.
My friend was legitimately allowed to take a small selection ofuseless boards home as scrap, and both he and I had fun over a
year discovering the faults and eventually having enough parts toconstruct two working models. I then built an interface to connect
to the A/D convertor, and with the aid of some machine-code
programming borrowed largely from another article I found in a
magazine, was able to display the first colour pictures. The system
was somewhat primitive as there were effectively only eight colours,
but nonetheless, progress was being made.
Images could now be stored on floppy disks, so time was slowly
running out for the tape recorder as an archive medium. Then I
upgraded the ZX Spectrum for a Commodore Amiga which could
not only do sixteen grey levels, but boasted a full palette of 4096
colours. I found a company on the south coast doing a software
program for the Amiga, which could be modified to look at input
from an A/D convertor. The result was very encouraging. And
something else could now be done—images could be animatedusing yet another freeware program. We were also now into therealm of double density 3.5” floppies (figure 2).

Figure 1 - A 1982 PDUS image with Radar Overlay

Figure 2 - A frame from one of the author’s 1989 Meteosat animations
created on a Commodore Amiga microcomputer.

Some of the chips used by the BBC B computer were ofcourse memory chips, and I was now a regular subscriber to
VHF Communications. In a series of issues there appeared thedescription of a framestore, the famous YU3 UMV design, whichhappened to use the same memory chips as the BBC computer. I
think you know by now what is coming (figure 3).
So my next project became the construction of a framestore. In
fact, I ended up building two in the same case. The first usedboards obtained from the magazine; later I was able to modify andduplicate the memory board layout to add a further section. The
framestore was based around enough memory and display to scroll
up a single transmitted sector. But by adding the extra memoryboards it allowed me the flexibility of switching between viewing
the succession of single frames from Meteosat (SDUS)—or from a

www.geo-web.org.uk

Figure 3 - The YU3 UMV Framestore built by the Author

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polar orbiter—whilst allowing the secondary memory boards to be
used for holding multiple frames for animation of just one sector,
such as the ‘D2’ European half-hour frames. This all required somefairly complex switching, and in particular the invention of a timing
board that would be locked to the mains for accuracy. But it also
had to be programmable for whatever sequence I might want toanimate. No off-the-shelf solution here!
Figure 4 is the non-PIC version. Purists will no doubt be screaming
at me, but you know what—it worked. And it used more chips fromthe BBC box, so it came free.

December 2013flat roof at the back of the house and I discovered that, by carefulpositioning, I could get a usable signal at about 3.5° elevation,
though quite a skew of the antenna was needed. This gave meaccess to a whole new range of APT (WEFAX) transmissions, as
this satellite often produced composite Mercator pictures covering
the north pole as well as the standard USA ones. Now, of course,
WEFAX from the GOES fleet has been replaced by LRIT. I built
a second receiver to dedicate to the GOES signal (figure 5).
Folk were reporting great success building their own preamps

Looking at it now, I do just wonder if a little madness had notentered into my life.

Figure 5 - A NOAA 11 image of Central America transmitted by GOES

Figure 4 - The non-PIC Framestore Circuit

Like-minded amateurs were now banding together, and conferences
and magazines sprouted on a number of continents. Germany, Italy
and the USA in particular were getting increasingly active. I still
have magazines like ‘I quaderni Della Radio’, which featured a very
extensive introduction by Marciano Righini to the various satellites
and their reception and display possibilities. This was in 1983.
Also ‘Weatherwise’ from the USA, and the Remote Imaging Group
Journal in the UK. And firms were now manufacturing their own
modules and turn-key systems.
The PC was becoming ever more popular. My first one came with a‘massive’ hard drive holding 20 MB of data. The rise of the Internet
and the general advances in component quality and sophistication
opened other doors. Software for the various computers became
more widespread. Simple DOS based Internet was becoming a
possibility.

using GAsFETs and very low noise devices, and I too enjoyedthe challenge of these tiny devices, though soon discovered theirsusceptibility to atmospheric conditions when there was lightning
around.
My own links with the USA were growing. I discovered that you
could actually contact the GOES programmers directly, so when I
noticed registration errors for example, a call to Charlie Vance at
NOAA soon got the picture fixed. I also discovered that the GOES
series of satellites (GOES I-K) in the early 1990s had an additional
data stream dedicated to EMWIN.
This was the Emergency Managers Weather Information Network.
I mentioned an interest on a message board and was contacted by
Colin Schulz who was the Pacific Rim operations manager. He waswanting to gain as much feedback on marginal reception systems
as possible, so kindly provided me with a Tigertronics EPS-96
device (figure 6).

At the same time, I was keen to explore other antenna designs
that were being shown to work with both the VHF and L-band
transmissions. For example, Les Currington built a magnificent
pyramidal horn for HRPT and PDUS work. This was steered bymeans of two motors and gave a slightly better signal-to-noise ratio
than his loop Yagi (figure 9).
My own experiments were with loop Yagi’s for the L-band. My firstused quite thick copper wire obtained from a nearby scrap yard.
The thickness gave a good bandwidth but was difficult to workwith. A blow torch and careful soldering were needed to join therings to the tops of long screws which passed through insulatorsin the support arm. Nonetheless, it worked quite well, and I was
encouraged to try a Mk II version with more, but thinner, rings.
This was even more successful. By now NOAA was positioning
a geosynchronous satellite at about 30°W. They also had loan ofthe ‘spare’ Meteosat-3 from EUMETSAT for a while when there
were problems with the GOES fleet (Meteosat-3, incidentally, wasapparently built largely from spare parts from Meteosats 1 and 2).
The main purpose of the loan seemed to be for storm monitoring.
These satellites were just on the edge of my horizon, but we had a34

Figure 6 - The Tigertronics EPS-96

The GOES downlink frequency used for the 9600 baud EMWIN
data stream was 1690.725 MHz, 275 kHz lower than the standard
WEFAX 1691.0 MHz signal. The received signal was passed
through a downconvertor to convert it to 137.225 MHz and thendemodulated to 9600 baud. So if you tapped into the receiverchain just prior to the main IF, you could, by means of an extremely
tight filter and FSK decoder, derive a 9600 baud signal which inturn could give all kinds of text and imagery relevant to weather
warnings. An excellent software program at the time, called
Weathernode, reconstructed the data blocks into meaningful text
and images. This Windows product created a directory structureon the hard drive, and completed files were assembled and thenassigned to an appropriate directory. Very neat. Colin is still very

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much involved and a recent exchange via e-mail has provided thefollowing notes on EMWIN from Colin himself.
EMWIN in the US and Pacific Islands“EMWIN has been a mainstay for delivery of warnings and otherrelated information in the US and Pacific Islands region for morethan 15 years now. Its first application was during the mid 1980s, todeliver warnings of rapidly developing tornadoes and other severe
storm to US Disaster Offices. In those days, private leased lines tocarry data were very expensive and a US National Weather Service(NWS) engineer, James Doherty, decided to look for a secure
but lower cost way to deliver this information to locations within
the USA. He realised that spare bandwidth was available on the
GOES satellites and that this could be used effectively to broadcast
warnings to multiple locations at very low cost. Jim received a gold
medal from NWS for his efforts to develop this system.
“After some initial experiments, a trial EMWIN broadcast wascommenced on the GOES satellites. This was well received in
the US by all who were concerned with emergency management
as a low cost way of receiving warnings. About this time there
was a heightened awareness in the Pacific that existing systems
there could not deliver warnings of cyclones and other severe
weather events reliably, and it was realized that EMWIN could
be the answer to this problem. During the early 1990s the Pacific
was hit by a number of severe cyclones and, as most countries
had no reliable warning systems, it was realised that each one
needed reliable satellite image receiving systems to be able tofollow cyclone development and tracks. Through efforts of theWorld Meteorological Organization (WMO) and the Pacific Regional
Environment Program, countries were supplied with APT and
WEFAX receiving systems and, together with EMWIN, now hadaccess to reasonable quality data to assist with cyclone awareness(when WEFAX transmissions were discontinued from both GOES
and MTSAT, WMO, with assistance from US NWS, provided new
LRIT receiving systems for 15 Pacific countries so that they could
continue to have access to good quality satellite images. Thesesystems were manufactured by Dartcom in the UK and have proved
very reliable).
“Some preliminary EMWIN tests were conducted in 1996 and it
was clear that EMWIN could be the answer to a major problem.
In mid 1997, discussions were commenced with US NWS about
the possibility of adding Pacific data and warnings to the EMWIN
broadcast for use by Pacific nations. After some work, it was
realised that the existing low-speed broadcast would not be able toaccommodate the Pacific as well as US mainland data, and so adecision was made to re-design the EMWIN broadcast to operate
at 9600 bps, and add the Pacific data. Receivers specific to EMWIN
were produced by a couple of manufacturers, and the systemcommenced the new broadcasts which covered both the US and
the Pacific Islands (figure 10).
“Receiving systems were rapidly deployed throughout the Pacific aswell as on the US mainland and the service went from a trial to a
fully supported operational system.
“In the meantime, a second transmission method was addedusing ‘push’ technology via the Internet. Anyone with a goodInternet connection could connect to a set of servers and receive
the EMWIN data stream. This was often used as a backup to thesatellite transmissions especially, during satellite eclipses.
“A number of the Western Pacific countries could not ‘see’ GOES
West, situated at 135°W, so it was decided that a re-broadcastof the EMWIN data could be added to GOES-7 which was being
used by the Western Pacific region for data and distance education
broadcasts. An uplink to GOES-7, which could be received by anumber of countries in the Western Pacific, was established fromthe University of Hawaii. As GOES-7 was not in a stable orbit due
to fuel restrictions, tracking antennas were needed.
“As the older satellites were phased out and new ones took overthe GOES East and West locations, regulatory issues required

Figure 7 - A superior image of Great Britain produced by an ink-jet printera change of transmission format, so a new EMWIN format wasdeveloped which enabled added features, such as forward error
correction and double speed to be implemented. Again, newreceivers and new software were required, and manufacturers roseto the occasion by producing the necessary hardware and software
to enable the transition to take place.
“Funding for these upgrades from WEFAX and EMWIN-I to LRIT
and EMWIN-N were provided largely by the US NWS, USAID, EU,
the Pacific Regional Environment Program and the Pacific Applien
Geoscience Commission. Without these valuable contributions
these systems would not be available for Pacific nations.
“With the demise of GOES-7 due to the depletion of its positioning
fuel, the Western Pacific was again in EMWIN ‘darkness’ and now
a small version of EUMETCast is being developed to provide a
EUMETCast-type service to the region.
“Looking to the future, the Japan Meteorological Agency (JMA) has
announced that it will cease direct image broadcast from MTSAT,
and in future all users will be expected to use the Internet foraccess to MTSAT imagery. That suggest that a bandwidth of 35 MB
will be required, which is clearly out of reach of any but the mostdeveloped countries.
“Strong representations were made to JMA that, in most Pacificcountries, where the Internet service is far from satisfactory with low
speeds and high cost, this is not an option for most island nations
at this time. A trial broadcast of MTSAT data via GOES-W LRIT hascommenced, and this will fill some gaps.

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Figure 8 - The huge variety of equipment needed by the author to receive weathyer satellite images in ‘the Good Old Days’ of the hobby

Figure 9 - The pyramidal horn antenna built by Les Currington

Figure 10 - A typical EMWIN station“Just recently, JMA has announced that it may provide MTSAT data
via a commercial satellite for use by Pacific countries, so perhaps
this will assist to fill in gaps after the direct broadcasts cease. It will
mean another set of receiving equipment, but seeing that DVB-S2
format is proposed in ‘C’ band, the equipment required will besimilar to that used for EUMETCast’s Africa service”.
Bespoke Systems
The next logical evolution as computing power grew and came
down in price was for bespoke systems to appear. In the early36

1990s, about five companies were regularly targeting the amateur
as well as the professional market, concentrating mainly at theubiquitous WEFAX or APT end of the market. But some had also
found ways to receive HRPT and PDUS transmissions with circuitboards at prices just about affordable for the amateur pocket, as
well as those from satellites like the all too short-lived ‘SeaWiFS’.
For a long period, both bespoke and home-brew systems ran inparallel, depending on user ability. Many schools and colleges
were also buying systems using dishes and simple dipole aerials.
I had the privilege on a number of occasions of visiting the nearby

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comprehensive school to give illustrated talks, and also to sortout their systems when the weather itself seemed to get theupper hand. Amateur radio groups were also intrigued, as someof them were running slow scan picture transmissions (SSTV),
and I remember a visit to a Bristol group of the Radio Society ofGreat Britain to put on an exhibition and do a presentation in theuniversity.
By now I had also seen the benefits of some of those off-the-shelf
systems and, with a very busy period in life coming up, I saved up
the pounds to buy a couple of the systems which had interfaces to
the PC. Apart from occasional glitches, they gave superb results.
Colour was now prominent and, with PC graphic boards capableof using a palette of many thousands of colours, it meant thattemperature profiles as well as channel combinations suited to landand sea display gave greatly enhanced imagery.
Pagers began to transmit in the VHF bands causing spill overfrom badly set up systems (often their transmitters rather than ourreceivers), requiring higher specification systems at our end toeliminate the interference.
The photograph reproduced in figure 8 shows the greatest
extent of my receiving station in its pre-EUMETCast heyday.
The oscilloscope had become a smaller solid-state Cossor one,but alongside the older machines were now the framestore, withits black and white monitor, and on the right the Amiga and thebare-bones BBC Master with its sixteen colour monitor. You may
also pick out the dot matrix printer, which struggled to produce
meaningful image printouts. Later, inexpensive ink jet printersbegan to appear, which with good printer drivers were capable of

Last summer, NOAA circulated its user basewith a questionnaire relating to the ‘needfor L-Band service on JPSS-2 and beyond’.
The JPSS (Joint Polar Satellite System) is
to be NOAA’s next generation of weather
satellites. Suomi-NPP is the precursor
satellite of the series and is currently testing
the instrument technologies to be used by
future JPSS craft. Although responses to thequestionnaire are long closed, the document
does provide useful insights into the way
in which dissemination of data could be
handled in the future.
As ever, costing is at the heart of the matter,and NOAA is in the process of re-evaluating
the need for direct readout services on its
future polar-orbiting satellite system, most
specifically to determine if there is a user
requirement. Several NOAA managers
believe that data delivery could be met using
land lines, commercial rebroadcasting andthe Internet, rather than by direct readout.
JPSS Delivery Modes
It is planned that the JPSS will carry
High Rate Data (HRD) broadcasting on its
spacecraft, comprising the complete, full
resolution dataset from the entire instrument
suite. The HRD broadcast will be transmitted
on carrier frequencies of 7812 MHz and7830 MHz in the X-band at a rate of
20 Mbps. Reception will require a bandwidthof 30.8 MHz with a tracking receive antenna
aperture no greater than two metres indiameter.

GEO Quarterly No 40

giving some really good printouts. Figure 7 is an example showing
excellent detail in a visible image with the UK.
EUMETCast
Most recently, EUMETCAST arrived on the scene, transmitting both
LRIT and HRIT data via commercial satellites transmitting in the ‘C’band, spelling the end for WEFAX in the L-band. Thankfully, withthe agreement of the British Met office, following canvassing fromamateurs, access was granted to nonprofessionals. The rest, as
they say, is history. A smaller dish, a card in a PC and appropriate
software: that was all that was needed.
As much as I enjoy now using the bespoke equipment andsoftware, I would maintain that I was hugely privileged to enjoy
the thrill of the chase during those earlier years. I am profoundly
grateful for the plethora of help received as well as the satisfactionof a little given back. Perhaps having passed retirement age now
it is just as well that I am not climbing too many ladders to adjust
aerials blown around in the 70 kph gales we sometimes experience
here right on the coast. Battling to align an 80 cm dish when you
haven’t realised that your laptop LAN link cable has pulled out,
when you were using it to see the signal strength on the remotecomputer is not fun, but it is the best substitute.
Undoubtedly the best is yet to come in terms of data, resolution etc.
But for this gentleman, the best fun was in yesteryear. I just hopethat readers have found this blast from the past an informative andalso enjoyable read.
All the best for the future guys!

There will also be a Low Rate Data (LRD)
broadcast transmitting a subset of the fullsensor dataset, intended for, amongst
others, land and ship-based terminals,
worldwide weather services, and otherinternational users. The LRD is an
L-band broadcast that will provide data at
a rate of about 3.88 Mbps on 1706 MHz,
using a bandwidth of 8 MHz. It will
require a tracking receive antenna with
an aperture not exceeding one metre indiameter.
Starting with JPSS-2, NOAA will
simultaneously broadcast both HRD and
LRD real-time data streams to suitably
equipped field terminals worldwide.
Dissemination by X-Band or L-Band?
The NOAA JPSS Program Office believes
that the data included in LRD broadcasts
can be provided to users through othermeans. Frequencies between 7750 MHz
and 7900 MHz in the X-Band have been
allocated to data transmissions frompolar-orbiting meteorological satellites,and several satellite operators are now
considering using the X-Band (around
8 GHz) for direct readout from future
generations of polar-orbiting systems.
The main reason for this is that advancesin remote-sensing technology have
led to high-resolution instruments thatgenerate quantities of data an orderof magnitude greater than those of awww.geo-web.org.uk

decade ago: such high data rates cannot
be accommodated in lower frequency
transmissions. Furthermore, progress inradio-communication techniques renders
X-Band receiving equipment more‘affordable’ than it used to be.
The consequences of direct readout
services being available in X-Band, rather
than L-Band include:• access to higher data rate services(20 Mb/s instead of 3.8 Mb/s), which
is necessary to access all data at full
resolution• the need to use a higher-classantenna and receiving chain (systemcost: X-band $350k-400k, L-band$150-200k)• higher sensitivity to rain, requiring
appropriate margins in the linkbudget, especially for inter-tropicallatitudes• higher risk of interfering sources:
X-Band is used by many othertelecommunication applications, andthe feasibility to operate an X-Band
receiving site without interference
has to be checked on a case bycase basis for each site.
The combination of these two services
is expected to satisfy the user needs for
efficiency, robustness and affordability,
but maintaining two different services inparallel is a design constraint for futuresatellite systems.

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A NASA Earth Observatory Report

Located on Russia’s Kamchatka peninsula, Klyuchevskaya is one of
the world’s most active volcanoes, with twelve confirmed eruptions
since 2000. Erupting intermittently since mid August, activity
intensified on October 11 when a thick plume of ash and steam
streamed from the summit, and subsequent days were marked by
explosive eruptions, lava fountains, and volcanic tremors. At times
the ash plumes from the stratovolcano’s 4750 metre summit—thehighest in Kamchatka—were reaching an altitude of 10 kilometres.

38

This image was acquired by the Operational Land Imager aboard
NASA’s Landsat 8 satellite on October 20, and shows multiple lava
flows streaming down the mountain’s northern and western flanks.
Snow and clouds are white, the ash plume is light gray, and forests(where the trees are tall enough to stand above the snow cover)show as dark brown.

www.geo-web.org.uk

NASA Earth Observatory image by Robert Simmon
using Landsat data from the USGS Earth Explorer

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GEO Quarterly No 40

Les Hamilton
In the May issue of GEO Quarterly, we reported on the February
Chelyabinsk Fireball that resulted when the largest meteoroid toenter Earth’s atmosphere this century streaked across Russia’s
Ural mountains [1]. It was believed that a large fragment from themeteoroid had punched a mysterious hole that appeared in the iceon Lake Chebarkul.
Attempts to recover the meteorite, which was buried under the lake
bed beneath twenty metres of water, began in early September, butwere hampered by the thick layer of mud covering it. The divers
had to work in conditions of zero visibility due to the extremely
muddied waters of the lake, and storms caused additional delays.
Finally, after pumping mud away from the rock for ten days, therecovery of the largest fragment, which weighed 570 kilogrammes,
was able to go ahead on October 16. It is probably one of the tenlargest meteorites ever discovered on Earth.
Museum staff preparing the Chelyabinsk meteorite for exhibition
Photo © RIA Novosti

Divers bring the meteorite ashore from Lake Chebarkul
Photo © RIA Novosti / Aleksandr Kondratuk

According to Sergei Zamozdra, assistant professor at Chelyabinsk
State University, initial examination showed all the characteristics
of a stony meteorite: a thick fusion crust, clearly visible rust and alarge number of indentations.

Revealed for the first time: the 570 kg fragment of the Chelyabinsk meteoroid
Photo © RIA Novosti / Aleksandr Kondratuk

The cleaned meteorite exhibited in its strengthened display case
Photo © RIA Novosti

A group of local schoolchildren admire the 570 kg Chelyabinsk meteorite
in its permanent display area in the Chelyabinsk Regional Museum
Photo © RIA Novosti

Just a day after recovery, and following preliminary cleaning, themeteorite was put on display in the Chelyabinsk Regional Museum,
where it caused great interest. It was placed in a special display
case with a fortified base so that everyone can now admire it. The
showcase has become very popular. Its circular shape allows theexhibit to be viewed from all sides, and the dome can be raised
when necessary to carry out further work on the meteorite.
Reference
1 Chelyabinsk Fireball, GEOQ 38, page 6 (June 2013).

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Francis Bell and Les Hamilton

The first weekend of October thisyear was remarkable for the numberof severe cyclones that were active
over the Indian and Pacific oceans.
Francis Bell used the EUMETCast
service, which relays images fromgeostationary satellites located overthe Pacific and Indian oceans, to run
an animated sequence of MTSAT
and Meteosat-7 images using
David Taylor’s MSG DataManager
software, and applying theLandandSea-red colour lookup
table to differentiate cloud-top
temperatures.
Near centre on the image at right is
Cyclone Phailin, the most powerfulstorm ever recorded in the Indian
Ocean, about which you can readmore in the article on page 22.
The key at the foot of this pageshows the colours purple throughgrey for cloud temperatures between-80°C and 0°C, and shades ofblue for sea surface temperatures
between zero to 30°C.

Cyclone Phailin sweeps across India as Typhoon Fitow heads towards China imaged by Meteosat-7
on the evening of Sunday, October 13, 2013
Image © EUMETSAT 2013 - Processing: Francis Bell

Cyclone Phailin sweeps across India as Typhoon Fitow, hotly pursued by Typhoon Danas makes for the Chinese mainland
imaged by Japan’s MTSAT on the evening of Sunday, October 13, 2013
Image © EUMETSAT 2013 - Processing: Francis Bellwww.geo-web.org.uk

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section from a 1-km resolution visible image displaying
Typhoon Fitow bearing down upon China.
Ordering Larger Downloads
Should you find the FSDC service useful, and you require to
download more than two Feng Yun-2 HDF files per day, you
can apply to increase your allocation. On the main FSDC
web page, immediately above the ‘FY-GEO’ button describedabove (figure 4), is a menu bar where you will find the option‘Documents’. Click this and select the item ‘Application
Form’, which allows you to download a Word document
entitled ‘User Upgrade Application’.
Complete this form, in particular the field labelled ‘Whichlevel do you want?’ There are two options:• B (3 GB/order, 10 GB /day)• C (1 GB/order, 5 GB/day)Weather Watching away from Home
continued from page 27

clockwise into the small areas of Low pressure over Holland andFrance. Wind directions across the UK will be predominantly fromthe west but varying from southwest to northwest depending on
location.
References
1 Weather watching away from Home, GEOQ 39 September 2013
2 A major source of noise is mains-borne networking; the EU mandates
spectrum notches for the Amateur Radio bands but not for Utility
frequencies such as those used for wefax.
3 http://software.muzychenko.net/eng/vac.htm
4 http://www.nws.noaa.gov/om/marine/rfax.pdf
5 http://www.w1hkj.com/

Request from NOAA

Finally, scan the completed application form and email it todataserver@nsmc.cma.gov.cn

Further Image Option
In addition to HDF files of Feng Yun-2 imagery, FSDC also
makes available similar files for Japan’s MTSAT2. To accessthese data files, clock where it states ‘More ..’ to the right of
the FY-2C checkbox in figure 4. This moves on to a new page
with a menu bar that includes ‘MTSAT’. Clicking this opens
two tabs, one for MTSAT2 and the other for the now defunct
MTSAT-1R.

NOAA is trying to put together a list of LRIT, EMWIN and future
HRIT users. They would like to be able to distribute information on
the upcoming GOES-R HRIT/EMWIN that users will need. Some
500 satellite users have already been contacted, but there aresurely many more out there. If you can help in any way, pleasecontact Jim Wydick atjames.wydick@noaa.gov

so that all satellite data users will benefit.

At the foot of the page tick the check-box for ‘NOM Data’,
select the dates and times as for Feng Yun, then press the‘Search’ button. Note that historic MTSAT-1R data is only
available from July 2005 till July 2010.
MTSAT HDF files can be read using FY2-HDFReader (but notwith GeoSatSignal).

Figure 10
Part of the 04:32 UT MTSAT2 visible image from September 30, 2013
Image: Feng Yun Data Centre at CMA (http://satellite.cma.gov.cn)

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GEO Quarterly No 40

Storm Dunlop

Dear Les
With reference to the lack of interest/material from the members
referred to in the last issue of GEO Quarterly, I would like to put
forward a few thoughts as to why this may be. I would assume
that a high percentage of members are from the UK, and as such,maybe there is an attitude of ‘surely you do not want more picturesof the UK and Europe—Boring’. For myself I find them interesting,with a wide range of cloud formations as seen from above, but
possibly not so for readers in the USA or Down-Under.
As for those living elsewhere, some do send in pictures of theirareas, and I find them interesting, but I feel that in all cases there
may be the feeling of: ‘I am only an amateur in the hobby, and myknowledge is very limited’. Therefore, if I try to write an article and I
make mistakes, then I may have it rejected. Taking into account thetime involved to produce even a short article, this may well turn alot of members off from even attempting such an item. And time isalso a factor: family affairs, jobs, care for sick etc., are all reasons
why we tend to put off writing to GEO Quarterly or any othermagazine.
Many I am sure, like myself, are not really into the computing sideof the hobby (i.e. receiving MSG via EUMETCast) but are happy
with just the APT aspect of the it. I do wonder what will happen to
those members when APT ceases in a few years time. I am unsure
whether I will to go over to MSG or not. The cost of a new computerand all the accessories and license fees are off-putting, around£1000.
There is a small percentage of our membership, which appears
to have knowledge and experience in both the satellite/weather
professions and computing, and uses these skills, as can be seenfrom their excellent articles; but not every one has these skills, nor
are they able to obtain them. I thank them for their input, but withany magazine, we cannot reply on the membership to provide all
the articles.
A thought I have for an article that readers may be interested in, is
one concerned with all the satellites that may be received using the
MSG set-up, and a break-down of what they do and the software
required to create images from them. I know that there are many
that you show pictures from, but showing my amateur status, I haveno idea as to how to download them.
Laurence Holderness, Narbeth, Wales.

Ideally, of course, the wind vane and anemometer should beinstalled as high as possible: the standard height recommended
by the World Meteorological Organisation is 10 metres. Thisis impractical for most domestic installations, but whatever theheight, there is a problem in ensuring that the wind vane is set
to the correct compass direction. This is difficult, because thedirections are shown by small letters embossed on the plastic
housing and, at any height above eye level, these are essentiallyinvisible from the ground. Luckily, the arm connecting the windvane and the anemometer needs to be orientated east-west, andthis is easier to set correctly. But the task remains difficult unless
you have easy access at the full height of the mast (perhaps witha tower).
This was impossible in my case, and the best I could do was todefine a baseline from the mast extending to the east, and then,sighting visually from the end of the baseline, turn the whole
upper mast until the arm appeared to be correctly aligned. The
software does allow one to adjust the calibration for direction,and one method might be to temporarily restrict the vane to point
east (along the arm) and enter the appropriate correction, shownby the difference between the reading and 90°. I intend to try thismethod next time I need to gain access to the anemometer andwind vane.
A common criticism of this particular equipment is the length ofthe connecting cables. With my equipment, the cable between
anemometer and wind vane was only just long enough. Yet thecables from the wind vane and the rain gauge to the transmitterare exceptionally long. I have converted this last point into anadvantage by deliberately mounting the unit containing thetransmitter and the temperature, humidity, and pressure sensors
much lower down the mast—which should not compromise
accuracy—at such a height that the battery compartment is easily
accessible when the batteries need to be changed.
Another point was raised by a friend with an identical unit, who
experienced problems because his rain gauge became infested
with spiders to such an extent that the readings were affected.
This was cured by using an insecticidal spray such as those usedaround the house to kill cat or dog fleas. Spiders may not be
insects, but they have certainly stayed away from the rain gauge.

Interface Wanted
We have received a request from Trevor Smith VK3TI, one of ourmembers in Australia. Trevor is on the lookout for a TimeStep Prosat
for Windows External Interface to use with his Timestep APT system.
If any reader still has one of these interfaces, and no longer hasa use for it, Trevor would be pleased if you could get in touch withhim atvk3ti@bigpond.net.au

I was interested to read Geoff Morris’ account of his weather
station in GEO Quarterly 39 (page13), because I recently installed
an identical, ‘entry-level’, WS 1081 system from Maplin. A few
points from my own experience may help anyone else thinking
about installing similar equipment. Although there are warnings in
the instruction booklet about possible interference, I have had no
problems with radio reception between the transmitter on the mastand the touch-screen display, despite all the different pieces ofequipment either connected to my computer, or in close proximity
to the display (the distance between transmitter and receiver isabout 25 metres).

I, too, use the Cumulus software, which is certainly superior to
the EasyWeather program supplied with the unit. One strange
problem seems to affect the software, however. Both my friend
and I have found that the pressure reading shown by Cumulus
does not agree with the reading shown on the touch-screen.
Although it is easy enough to include a calibration adjustment,-6.5 hPa in my case, it seems a strange discrepancy when all theother readings are identical between touch-screen and computer
display.

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Marc Peigneux

Mont Aigoual is the last mountain weather observatory
still active in France (figure 1). Situated in the south of the
Cévennes massif, a few kilometres from the Mediterraneansea, its summit rises to 1567 metres.
I was lucky enough to take beautiful summer hikes in thismassif, but I would not for anything have missed the visit
to the site actually exploited by the Météo-France engineers
on this mountain. But, first of all, let us try to understandthe reasons for the establishment of this ground-observation
centre.
Some Reminders from History
On November 14, 1854, during the Crimean War, a terrible
storm, which arose without the slightest warning, crossed
Europe from west to east, causing the loss of 41 ships in theBlack Sea and sparked initial investigations into meteorology
and weather forecasting in Europe. Following this event (in1855) the famed astronomer Urbain Le Verrier, who was at
the time manager of the astronomical observatory of Paris,
decided to create a network of weather-observation stations.
The network consisted of 24 stations, initially all located in
France, but later expanded throughout Europe.
Connected by the telegraph, these stations transmitted theirinformation reports, three times each day, to the Imperial
Observatory in Paris, which used them to prepare a Europewide analysis. By 1861, the network had been extended toinclude Saint-Petersburg, Harapanda (Norway), Valentia(Ireland), Cadiz, Naples and Constantinople, and the firstisobaric maps were being transmitted to foreign weather
stations (figure 2).
During the 1930s, and more specifically following the end of
the Second World War, the French National Meteorological
Offices were developed. These surface observation
stations operate 24 hours per day, and their reports are
made simultaneously, at fixed times every day. Besides
these meteorological stations, there are also numerous
climatological stations manned by volunteers, as well as
automatic systems.

Figure 1 - The Observatory at Mont AigoualMont Aigoual
In an awe-inspiring area in the centre of the Cévennes
National Park, Météo-France and the ‘Communauté De
Communes de l’Aigoual’ advocated making the public moreaware of both the weather and the Aigoual massif.
Météo-France technicians introduced the public to thescience of meteorology and to the techniques of weather
observation. They also taught how to decode satellite andradar pictures. The centre has 600 m2 of exhibitions,hundreds of photos, videos and slide shows.

The recorded data are very useful in refining the forecasts
and pinpointing exactly the location of exceptional
meteorological phenomena. High altitude measurements weredeveloped during the nineteenth century, with the creation of
the following four ‘mountain observatories’:• Puy de Dôme station, in Auvergne (1465 m)• Mont Ventoux station in Vaucluse (1909 m)• Mont Aigoual station, in the Cévennes (1567 m)• Pic du Midi station, in the Pyrénées (2876 m)
The Pic Du Midi, Mont Ventoux and Puy De Domeobservatories, although very busy with scientific andtechnical activities, are still very nice places to visit, but theirpresent ‘vocation’ nowadays is somewhat different from thatoriginally assigned. Puy De Dôme, inaugurated in 1876, is
now a very important part of the Earth Physical Observatory.
Mont Ventoux, created in 1882, ceased its weather
observation activities in 1968 while Pic Du Midi, inaugurated
in 1882, was gradually transformed into an astronomical
observatory following the Second World War.

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Figure 2 - One of the early Isobaric Maps

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GEO Quarterly No 40

Conferences
Météo-France Mont Aigoual also hosts
some conferences and, due to a lucky
coincidence during my visit, I had theopportunity to attend two of them. The
main subject of the first conference
was Teledetection and Satellite Meteorology,
delivered by M. Sylvain Le Moal of
Météo-France, Centre de Météorologie
Satellitaire de Lanion. The second
conference, entitled The Future Weather on
my Planet, was given by M. Joël Colado,a weather forecaster for Météo-France
on two of Radio-France’s national
networks.
It is also important to point out that the
Météo-France specialists also organise
weather forecast workshops, where theyteach about how they control the tools
used for producing weather reports,
as well as holding educational days forschoolchildren and students.
The locations of the original four Mountain Weather Observatories

The author pictured in the museum during
his visit to Mont Aigoual Observatory

Part of the museum at Mont Aigoual Observatory

A video projection of a Meteosat IR image
at Mont Aigoual Observatory

Panoramic view over the Cévennes Massif
Credits: Météo-France, Mt St Aigoual, Eric DIOT, (Météo-France)

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EUMETCast On-Line
Registration Guide
If you require to register as a first-time user for
any of the free EUMETCast data streams suchas MSG, NOAA AVHRR, Metop etc., or needto renew an existing subscription, this must be
done on-line.
GEO has produced a step-by-step guide to theentire process at
http://www.geo-web.org.uk/eumreg.html
This guide also contains a direct link to theofficial EUMETCast on-line registration form,
which can otherwise prove somewhat tricky tolocate.

GEO Helplines

The Group for Earth Observation

Weather Satellite Reports
If there is a single Internet Forum that isrelevant to all weather satellite enthusiasts,
it must surely be Douglas Deans’ Weather
Satellite reports.
Here you will find every conceivable type of
information about weather satellites, whether
polar or geostationary, APT, HRPT, LRIT orwhatever.
Absolutely everything is covered, and theinformation is updated every week. Special
additional bulletins may be issued if an
important change takes place mid week.

Douglas Deans

You can read the bulletins from this URL

Dunblane, Perthshire, SCOTLAND.

http://tech.groups.yahoo.com/group/
weather-satellite-reports/
or, even better, elect to have the reports sent
to you by email every Monday.

All aspects of weather satellites from APT,
HRPT to Meteosat-9 DVB/EUMETCast
systems.
• telephone:(01786) 82 28 28• e-mail: dsdeans@btinternet.com
John Tellick
Surbiton, Surrey, ENGLAND.
Meteosat-9 advice: registering for the various
MSG services, hardware and software
installation and troubleshooting. John will
also field general queries about any aspect ofreceiving weather satellite transmissions.
• telephone: (0208) 390 3315
• e-mail: info@geo-web.org.uk
Geoff Morris GW3ATZ
Shotton, Flintshire, NE WALES.
Geoff has lots of experience with aerial,coax,connectors, mounting hardware etc. andhas also done a lot of work with the orbiting
satellites. Geoff has been a EUMETCast
Meteosat-9 user for some time and is familiar
with David Taylor’s MSG software. He
should be able to share his experiences with
newcomers to this branch of the hobby.
• Tel: (01244) 818252• e-mail: gw3atz@btopenworld.com
Mike Stevens
Portland, Dorset, England.
Assistance with reception of EUMETCast
to include Metop-A and Metop-B; also MSG
Data reception and set-up within the PC, andassistance with dish alignment and set-up.
• email: mikeg4cfz@gmail.com
Guy Martin G8NFU
Biggin Hill NW Kent, ENGLAND
Guy is prepared to advise anyone who wishing
to receive MSG/Metop using Windows 2000 or
XP. Can also help with networking and ADSL
router setup.
• gmartin@electroweb.co.uk
Hector Cintron
San Juan, Puerto Rico, USA
Hector is prepared to field enquiries on HRPT,
APT, EMWIN and NOAAPORT• Phone: 787-774-8657• e-mail: n1tkk@hwic.net
Email contact can of course be made at any
time, but we would ask you to respect privacy
by restricting telephone contact to the period
7.00 - 9.00 pm in the evenings.

46

Internet Discussion Groups
There are a numerous Internet-based
discussion groups available to weather satellite
enthusiasts. You can join any of these by
sending an e-mail to the appropriate address,
with a request to subscribe. Indeed, a blanke-mail containing the word ‘subscribe’ in its
Subject line is all that is required. Some of themore useful groups and their contact addresses
are listed below.
APT Decoder
This is a group where users of Patrik Tast’s
APTDecoder can share information andproblems.
http://tech.groups.yahoo.com/
group/APTDecoder/
GEO-Subscribers
This is GEO’s own group, where members can
exchange information and post queries relating
to any aspect related to weather satellite
reception (hardware, software, antennas etc),
Earth observation satellites and any GEOrelated matter.
http://tech.groups.yahoo.com/
group/GEO-Subscribers/
Satsignal
An end-user self help group for users ofDavid Taylor’s Satellite Software Tools(SatSignal, WXtrack, GeoSatSignal, HRPT
Reader, GroundMap, MSG Data Manager,
AVHRR?Manager and the ATOVS?Reader).
http://tech.groups.yahoo.com/
group/SatSignal/
MSG-1
A forum dedicated to Meteosat Second
Generation (MSG), where members share
information about the EUMETCast reception
hardware and software.
http://tech.groups.yahoo.com/
group/MSG-1/

www.geo-web.org.uk

December 2013

Copy Deadline for
GEO Quarterly No 41 is
Friday, January 31, 2014
The Editor is always delighted to receive
articles and images for inclusion in
GEO Quarterly. These can relate to any
aspect of Earth Imaging, especially• Technical articles concerning relevant
hardware and software• Construction projects• Weather satellite images• Reports on weather phenomena• Descriptions of readers’ satellite imaging
stations• Activities from overseas readers• Letters to the Editor• Problems and Queries for our experts toanswerContributions should of course be original
and, where possible, should be submitted
to the editor in electronic format (e-mailattachment, CD, DVD). But of course, wewould also accept handwritten or typed copy.
Please note, however, that major articles
which contain large numbers of satellite
images, photographs or other illustrations
should be submitted as early as possible,
so that they can be prepared and made up
into pages in time for publication.
Images and Diagrams
Images can be accepted in any of the major
bitmap formats: JPG, BMP, GIF, TIFF etc.
Images in both monochrome and colour are
welcomed. Line drawings and diagrams are
preferred in WMF, EPS or postscript formats.
We can also scan original photographs,
negatives and slides.
Gridding, Overlays and Captions
Please note that readers’ satellite images
should be provided without added grid lines,
country outlines or captions unless these areconsidered essential for illustrative purposes
within an article.
If your article submission contains embedded
images and diagrams, please note that you
must also submit copies of the original
images in one of the formats describedabove: these are essential for page make-up
purposes.
Submission of Copy
Materials for publication should be sent to
the editor,
Les Hamilton
8 Deeside Place
Aberdeen AB15 7PW
ScotlandThe most efficient way to do this is by email
attachments to the following address
geoeditor@geo-web.org.uk
Particularly large attachments (8 MB andabove) can be transmitted via YouSendIt
www.yousendit.com_________________________
And finally . . .
if you do have material ready for the next
issue of GEO Quarterly, please submit it
as soon as it is ready—do not wait till thedeadline above: this will simply create an
editorial log-jam and delay publication.

December 2013

The Group for Earth Observation

www.geo-web.org.uk

GEO Quarterly No 40

47

GEO Quarterly No 40

48

The Group for Earth Observation

www.geo-web.org.uk

December 2013

This striking image from Meteosat-10, acquired at 13:30 UT on February 18, 2003, was downloaded via EUMETCast by Mike Stevens
Image © EUMETSAT 2013