Group for Earth Observation

The Independent Amateur Quarterly Publication for

Number 17

Earth Observation and Weather Satellite Enthusiasts

March 2008
Inside this issue . . .
Climate Change is a topic
that is seldom far from ourminds these days. A seasonof unprecedented ice melt in
the Arctic Ocean is
documented by Les
Hamilton, while a year of
turmoil on the European
weather scene, particularlyin the UK, is described byJohn Tellick.
Our star article this issue isJohn Silver’s Lightning
Radar construction project.
Taking advantage ofavailable free software,
John describes how to build
hardware to capture
lightning signatures anddisplay them on your PC.
Regular feature writer Peter
Wakelin has produced areal gem for this issue,
reminiscing on his years
spent as a professional
meteorologist based in the
Falkland Islands. Lavishly
illustrated with his own
colour photographs, thisarticle provides a revealing
insight to this remote cornerof the planet.
And to complete this eclectic
issue, David Taylor
evaluates an alternative
USB receiver for the
reception of EUMETCast on
computers running ‘Vista’.
Plus many more features ...

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

www.monitoringmonthly.co.uk

MANAGEMENT TEAM
Public RelationsT

he striking MODIS image on our front cover shows Foxe Basin in the Canadian
Arctic as it appeared to NASA’s Terra satellite in late September 2007, just when
the summer’s unprecedented ice-melt had reached its peak. Not only did the infamous
Northwest Passage become entirely ice-free for the first time in recorded history but
vast swathes of the Arctic were opening up as never before. Our article, Arctic
Meltdown, which appears on page 4, investigates the recent increasing dynamism
beyond the Arctic Circle.

A

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 Editornd to complement this, Peter Wakelin casts his gaze to the southern hemisphereas he draws on his experiences as a meteorologist based in the Falkland Islands
to paint a vivid picture of this distant and generally inaccessible part of our planet.

W

ith four full years under our belts, GEO would like to offer readers theopportunity to say what they think about the Group. Are we satisfying yourneeds in the world of satellite imaging? Are there areas in which you feel we could do
better? Are there particular topics you would like to read about more regularly in
GEO Quarterly? Maybe there are topics we cover that do not interest you at all! Help
GEO to tailor this periodical more to your tastes and to plan the Group’s future bylogging into
www.geo-web.org.uk/survey08.html

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

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

and completing our On-line Survey Form. Results from the survey will be publishedlater in the year.

Meteorological Consultant

S

Technical Consultant (hardware)ince last issue, Ed Murashi has been busy completing the second instalment of hisseries on obtaining LRIT images from the GOES geostationary satellites. In thisissue, Ed documents his home-brew hardware and provides everything needed byreaders who would aim at duplicating his efforts.

G

Peter Wakelin
email:
meteo@geo-web.org.uk
David Simmons
email:
tech@geo-web.org.uk

Webmaster and Website Matters

EO has featured several articles on the topic of lightning detection in the past.
Commercial detection systems tend to be somewhat expensive, however, so John
Silver has developed his own. Full details of his Lightning Radar System can befound in his article on page 31, which features full details of his design project, using
surface-mount components.

Ray Godden
e-mail: ray-geo@lescharriols.eu

y the time the next issue of GEO Quarterly appears, another GEO Symposium
will have taken place at the National Space Centre in Leicester. These events
prove popular every year, particularly for the opportunity they provide to readers tomeet up and exchange ideas. This is the opportunity where every GEO reader cancontribute to the Group, actively, by making a talk or demonstration, or simply byproviding GEO’s Management Team with ideas they would like to have included.
Turn to page 3 to learn the latest news about this year’s Symposium.

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

B

GEO Shop Manager

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

Francis BellLes Hamilton
David Taylor
Terence Smith
Francis Bell
Ed Murashie

GEO Shop
NOAA Satellite Predictions for the UK and Western Europe
Software Showcase - Douglas Deans
Copy Deadline for June issue - April 26
GEO Membership Renewal Form
Earth Observation News
Crystals for VHF Satellite Receivers
Why use the 3rd Harmonic
Trialling the Dexatek USB Box for EUMETCast
Unseasonable Weather Throughout 2007
Bernoulli Effect observed over the Gulf of St Lawrence
DIY Lightning Radar Project
Falkland Reminiscences
Cover and Full Page Image Details
GEO Web Survey
In Tray - Reader’s Letter
The Complete Earth - Book Review

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

International Liaison

Contents
GEO Report
GEO Symposium 2008
Arctic Meltdown
News in Brief
Script Snippets
Automated Overlays with GeoSatSignal
News 14 Carolina
GOES LRIT - Part 2: Hardware

Education CoordinatorPeter Wakelin
Francis BellRay Godden
David Taylor
John Tellick
Keith Fraser
John SilverPeter WakelinPeter Green

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3
4
9
9
10
16
18

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

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Advent Print Group,
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Hampshire SP10 3LU.
Every effort is made to ensure that thetechnical and constructional articles
published in this Quarterly are correct.
However, the ultimate responsibility is withthe reader to ensure the safety of
constructions and for any interfacing withother equipment. GEO cannot accept liability
for shortcomings in any published design or
any constructions carried out by members orother third parties.

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

GEO Quarterly No 17Group for Earth Observation

March 2008

Francis BellAs usual I would like to extend a welcome
to new members and thanks to those whohave renewed their existing membership. In
each Quarterly I do ask that renewals aredone promptly. Following up expired
membership is time-consuming andexpensive. I have just completed thisexercise for 134 lapsed members. The
response rate is looking good at the
moment so it is a worthwhile exercise
though still a lot of work. Currently ourmembership numbers are:
• UK
391
• Europe120• Rest of World50
To maintain a healthy bank balance weneed to retain or increase our membershipnumbers. If you have a friend, or belong toa group or club which you think may beinterested in joining GEO, please let meknow about them and I will dispatch theman encouraging letter together with a recent
GEO Quarterly. Just let me have the detailsof the prospective member by email tofrancis@geo-web.org.uk

Nostalgia
I have recently received my latest ESA
Bulletin and nostalgically noticed that they
have republished the very first image theyreceived from Meteosat-1 on December 7,
1977. At the time, it took me about a year
to recognise that quite low-cost equipment
was available for the direct reception of
Meteosat in ones own home. I duly boughta 90 cm dish, a Dartcom downconverter, areceiver and a hybrid computer interface. I
remember being so pleased with my firstimage of Madagascar! I was hooked, andfrom then on worked my way through all
the subsequent Meteosat series. My
equipment failures have been few, mainly
due to nearby lightening strikes which blew
the top off my downconverter's GAsFET,
my APT preamp and computer modem. I
expect other members have had similar
experiences.
Congratulation.
On behalf of GEO, congratulations are inorder for Meteosat's almost faultlesstechnical achievements over 30 years andalso for their policy of making their data
available to users other than national
meteorological services. Thanks!
ESA Bulletin
I know I wrote something similar in our lastissue, but the ESA Bulletin always contains
something to interest me. The recently
issued Bulletin No 132 contains 18 pages

2

relating to Earth observation and weather
satellites and pages 42-56 show three
spectacular images of algal blooms in thesea. The growth of these algae is an
important dimension in the carbon balanceof the planet. The cell walls of some ofthese algae contain deposits of calcium
carbonate. When the algae die they finish
on the floors of the oceans, hence
removing carbon dioxide from theatmosphere. There are some excellent
electron micrographs of coccolith algae on
page 26 of GEO Q2.
The Bulletin also contains some stunning
images of the Earth (pp 88-9). The imageof California taken in October 2007 wasparticularly frightening to me as I was inthat region not many months before it was
taken. Page 91 shows the very first image
from Meteosat-1 while pages 79-80 givethe latest news about the Meteosat andMetop programmes.
The ESA Bulletin may be obtained free ofcharge from:ESA Communication Production Office
PO Box 299
2200 AG Noordwijk
The Netherlands
As well as your address, please write a few
words on why you want to receive theBulletin: for example,:research, home
experimentation, GEO member—orwhatever reasonably describes you
activities. The Bulletin is circulated to 59
countries so anybody could reasonably ask
to be put on the mailing list.
Forthcoming Events
GEO’s annual Symposium takes place on
Saturday, May 10, 2008. Details appear on
the following page.
GEO also hopes to be at the following
events• April 6, 2008 for the London
Electronics and Computer rally.
Location Kempton Park race course.
• April 25, 26 and 27. We hope to be
invited to the AMSAT-UK colloquium
held at Guildford University.

• October 23-23: Leicester AmateurRadio Show LARS at Donington Park.
It is worth noting that our friends in The
Netherlands, Werkgroep Kunstmanen, will
be holding their meetings in Utrecht on
May 10, Sept 6 and November 8 this year.
Visit their web site atwww.kunstmanen.nl

Conclusion
Of course my thanks to our talented
membership for sharing their skills within
our group: also to those who contribute to
our Quarterly publication and to thededicated management team who oversee
the running of GEO.

Question 16
September’s Question related to ESA’s
Sentinel-1 satellite which, together withfurther satellites in the series, will meet the
Earth observation needs for the Global
Monitoring for Environmental Security(GMES) programme. The launch of
Sentinel-1 is currently scheduled for 2011.
The satellite will carry synthetic apertureradar (SAR) capability; hence it will have totransmit a powerful radar signal to irradiate
the Earth's surface and then receive thereflected signals.
The Quarterly Question related to theavailable power from the satellite's solar
cell array. The answer can be found on
page 17 of ESA Bulletin 131, which gives afigure of 4800 W end-of-life power. I only
received a small number of replies but I
chose as the winner Storm Dunlop. I havesent him his calendar as his prize.
The Quarterly 17 Question
This Quarterly Question has been
generated by me looking at images of
Iceland. See page 49 of Bulletin 132 andthe front cover of GEO Quarterly 14 asexample images.
The question is straightforward:‘Does any part of mainland Iceland
fall within the Arctic circle?’• June 27-28 - GEO hopes to be atFriedrichshafen, Germany for
Europe’s largest amateur radio,
electronics and computer rally. If any
German members can help with
GEO’s stand please contact me at

You can answer just yes or no, or offer anumeric qualification if you wish. Answers
to me by email, atfrancis@geo-web.org.uk

by the copy deadline for GEO Quarterly 18.

www.geo-web.org.uk

francis@geo-web.org.uk

March 2008

Group for Earth Observation

GEO Quarterly No 17

www.geo-web.org.uk

3

GEO Quarterly No 17Group for Earth Observation

March 2008

Les Hamilton
The very first feature article in GEO Quarterly’s Launch Issue [1]highlighted the persistent summer decrease in permanent sea ice
cover in the Arctic Ocean between 1978 and 2003. Since then, theretreat of the permanent ice has continued apace. New summer
minima were recorded in 2005 and more recently 2007, when it
had shrunk to a 29-year low. Figures 2 and 3 illustrate how thispermanent ice has diminished by almost one quarter in the past
two years alone.
Satellites have been monitoring the Arctic continuously since 1978,
during which time their sensors have recorded a continuing
recession of the permanent sea ice summer minimum. At the endof each summer, sea ice cover retreats to its minimum extent. The
ice that remains, which is upward of three metres thick, is termed
perennial ice, and consists, mainly, of thick multi-year ice floes that
endure from one season to the next (as opposed to the muchthinner seasonal ice that reforms over open water between latesummer and the following spring). The area of this perennial sea
ice has been steadily decreasing by about 6.5% per decade since
the satellite record began.
Beginning in 2002, however, this decline steepened to an
estimated 8.5% per decade following the early arrival of springtime
melting north of Siberia and Alaska—and it continues to accelerate.
The 2007 minimum on September 16 was considerably less thanthe 2005 record, showing a decrease of 24% in just those twoyears! NASA scientists are working to understand this sudden
speed-up in sea ice decline and what it might mean for the futureof Earth's northern polar region (figure 1).

frequency which, being relatively insensitive to atmospheric effects,
can observe the entire polar region, even through clouds andsnowfall, to provide a view of sea ice dynamics in greater detailthan ever before. The images depict the AMSR-E data overlain on
a NASA Blue Marble [2] image of the Arctic Ocean and its environs.
Sea ice, depicted as a white mass at the centre of each image,stretches across the Arctic Ocean from Greenland to Russia, butlarge areas of open water are apparent as well. Although the 2007
melt season started out with slightly greater sea ice extent than2005, melting accelerated during the second half of June,especially in the East Siberian Sea, where warm temperatures andclear skies hastened the ice’s retreat. By early August—more thana month before the end of the melt season—ice extent had already
dropped below the minimum reached in 2005. Melting culminatedaround September 16 when the area of permanent ice had fallen tojust 4.13 million square kilometers, 38% below the 1979-2000
average and 24% below the 2005 record.
Given that the reduction in ice cover
over the preceding decade had
averaged some 100 000 km2 per year,
this decrease of over a million km2
compared with 2005 is extreme!

Figure 1 - Monthly Arctic Ocean Ice Minima (1979-2007)
Credit: National Snow and Ice Data Center, Boulder, Colorado.

The actual loss of sea ice between the 2005 and 2007 minima,
illustrated by figures 2 and 3, was in excess of 1.2 million km2, fivetimes the area of the United Kingdom. These images were createdusing information from the Advanced Microwave ScanningRadiometer for the Earth Observing System (AMSR-E) which waslaunched aboard NASA’s Aqua satellite in 2002. AMSR-E is ascanning passive-microwave radiometer which senses radiation at
six frequencies ranging from 6.9 to 89 gigahertz (GHz). The
determination of Arctic ice cover is achieved using the 89 GHz

4The Northwest Passage
In 1497, King Henry VII of England sponsored Venetian explorer
John Cabot’s expedition to search out a suspected east-west sea
route north of Canada that would, hopefully, shorten the journey
between Europe and the Orient. But Cabot got no farther thanwww.geo-web.org.uk

March 2008

Group for Earth Observation

GEO Quarterly No 17

Figure 2 - Permanent Arctic Sea Ice minimum on September 21, 2005

Figure 3 - Permanent Arctic Sea Ice minimum on September 16, 2007

Image: NASA/Goddard Scientific Visualization Studio, based on data from AMSR-E

Image: NASA/Goddard Scientific Visualization Studio, based on data from AMSR-E

Figure 4 - This Terra MODIS image dating from September 15, 2007 shows the Northwest Passage completely open.
NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center

Figure 5 - This Terra MODIS image dating from July 27, 2007 shows the East Siberian Sea with the New Siberian Islands prominent.
NASA image courtesy the MODIS Rapid Response Team, Goddard Space Flight Center

www.geo-web.org.uk

5

GEO Quarterly No 17Group for Earth Observation

making the discovery of Newfoundland. Nevertheless, Cabot’s
effort inspired a succession of adventurers, including Davis,
Hudson, Foxe, Cooke and ill-fated Franklin, who would continue
the search; but it was not until 1905 that Roald Amundsen became
the first to achieve the feat. Even so, Amundsen’s accomplishment
has rarely been repeated in modern times, as navigating from theAtlantic to the Pacific through Canada’s Arctic archipelago has
always proved difficult. However, during late summer 2007, resultsfrom the Advanced Synthetic Aperture Radar (ASAR) instrument
aboard ESA’s Envisat satellite (figure 6) confirmed the channel tobe fully navigable, the retreat of the sea ice having created an icefree opening through its waters that lasted five weeks
On September 15, 2007, the Moderate Resolution Imaging
Spectroradiometer (MODIS) flying aboard NASA’s Terra satellite
captured a largely cloud-free image of the Northwest Passage(figure 4) showing it to be ice-free for the first time since satellite
records began. Although this sea route had been characterised as‘nearly open’ several weeks earlier, persistent cloud cover had
prevented acquisition of a MODIS true-color view of the open
route. In this image, clouds are confined to areas north and southof McClure Strait and navy blue ocean waters stretch all the way
east into Lancaster Sound, north of Baffin Island. McClure Strait
does sport some remnant fragments of sea ice, the blocky, brokenup shapes suggesting old sea ice undergoing melt.
Foxe Basin
The extraordinary extent of melting is evident throughout the
Canadian Arctic, and the Terra MODIS image gracing our front
cover, dating from September 23, spotlights an ice-free Foxe
Basin—the shallow extension of the Atlantic Ocean that acts as the‘gateway’ to the Northwest Passage.

March 2008

Icemelt and Positive Feedback
The accelerating decline in sea ice may be due to changes inclimate brought about by the very lack of sea ice itself. Sea ice
has a bright surface which reflects most of the incident solar
energy back into space. When this ice melts, dark-coloured ocean
water, which absorbs rather than reflects radiation, is exposed. As
the ice continues to recede during the summer months, the Arctic
Ocean absorbs ever more heat from the sun. The increasing
reservoir of warmed water makes it harder for the ice to recover
during winter, bringing an increased likelihood of an even greater
ice retreat the following year. As this process repeats itself year
after year, the reduction in summer ice may become selfsustaining. It may well be that, before the end of the current
century, permanent Arctic sea ice could disappear completely.
The party was provisioned with food and fuel for an expedition that
could last as long as three years, and overwintering in the far north
was fully intended. That year the Arctic had enjoyed a particularly
warm summer and progress was rapid; ice-free seas leading all theway south down Prince Regent Inlet where a bay Ross christened‘Felix Harbour’ was selected for his winter base.
That October the seas froze and the party sat out the winterconfident that they would complete their quest the following
summer. But it was not to be. 1829 had been a truly remarkable
Arctic summer and it was not until August the following year that
Victory finally broke out from Felix Harbour. But she was able to

Sandwiched between Baffin Island and Hudson Bay in the territoryof Nunavut, Foxe Basin remains ice-covered for much of the year.
Landfast ice shelves normally hug its northern coastline until late in
the summer while its southern reaches bristle with shattered packice. The Basin is named after Luke Foxe, who explored the area in
1631-32 in the hope of finding a Northwest Passage across North
America. Roughly 500 kilometres across at its widest point, Foxe
Basin is home to the last large landmass to be discovered in North
America. The prominent, low-lying, almost circular island in thecentre of Foxe Basin was only identified as such following an aerial
survey in 1948, when it was named after Prince Charles, who wasborn that same year.
Sea Ice Retreat in the East Siberian Sea
Arctic sea ice melted at an unprecedented rate during the summerof 2007, especially in the East Siberian Sea. Figure 5 is a MODIS
image acquired on July 27; this shows a stretch of coastline fromthe Lena delta in the west and threading past the New Siberian
Islands, in which open water dominates the scene. The channels
between the Siberian coast and the New Siberian Islands arelargely ice-free, with only a rim of ice lingering against the southernshore of Kotel’nyy Island. The water is almost completely open to
the islands’ immediate northwest whilst what sea ice remains to thenortheast is sparse and fragmented.
A Historical Anomaly in the Context of Long-Term Prognosis
It is tempting to jump to the conclusion that runaway Arctic melting
could result in summer ice cover in the Northern Ocean dwindlingto zero within the next few decades. If the acceleration recorded inrecent years is maintained, this will become a certainty. But wemust be wary of interpreting what is a very brief snapshot of time inthis manner. Arctic waters have been known to open up then close
again spectacularly in the past.
In 1829, John Ross, fired by the ambition of discovering the elusive
Northwest Passage, set sail in the Victory, a 150 tonne paddledriven steam packet boat specially strengthened for service in the
Arctic. Privately funded to the tune of £18 000 by the gin magnate
Felix Booth, the expedition included James Clark Ross, nephew ofthe expedition leader, a man destined for future greatness in the
Antarctic arena.

6

Figure 6 - Envisat used its side-looking radar to image McClure Strait
in the Northwest Passage on July 31, 2007www.geo-web.org.uk

Image: ESA

March 2008

Group for Earth Observation

GEO Quarterly No 17of the ice remained at record-low levels
throughout most of October, suddenly, latethat month, the sea ice started to reappear
with unprecedented speed. During a tenday spell, ice cover increased at a rate ofover 150 000 km2 per day, the fastest everregrowth observed throughout all the years
of satellite observations. Nevertheless,overall sea ice extent throughout the Arctic
remained below normal throughout
November.
Figure 7 shows a close-up representationof the record minimum of September 16,
2007, using data from the AMSR-E
instrument flying aboard NASA’s Aqua
satellite. Figure 8 shows how the ice cover
had already reasserted itself byNovember 14. The irregular line drawn
around the Arctic zone in each image
indicates the region where there was atleast 15% ice cover during at least half ofthe months of November during the longterm record (median sea ice extent).

Figure 7 - The ice at its record minimum extend - September 16, 2007

This long term record is based on satellite
observations collected between 1979 and2002 by sensors on the Nimbus-7 satellite
and three DMSP satellites.
It is apparent that the September ice extent
was a long way below normal, and that by
November the sea ice had increased
significantly compared with two months
earlier. The area of persistent open water
north of Alaska and eastern Siberia, though
not unprecedented, was unusual for thetime of year. It was also predominantly icefree during the November months of 2002
and 2006.
A particularly rapid sea ice regrowth rate
following a record low may initially appear
to be surprising, but it is not completely
unexpected. Where large expanses of ice
survive the summer melt, less open wateris available over which new ice can form.
When summertime ice extent has
diminished to record minimum, on theother hand, much larger large areas ofopen water are available for regrowth
once temperatures drop sufficiently.

Figure 8 - The ice makes a rapid return - November 14, 2007

sail a bare five kilometres north before ice
forced the ship to a standstill. And that was
about it for the season as a mere
300 metres of further advancement proved
possible before winter reasserted itself inearly November.
The one tiny success that year was James
Clark Ross’ discovery of the North Magnetic
Pole. Three further winters were spent in
the confinement of the ice until, indesperation, John Ross decided to trek
overland to gain safety, the party dragging
three of the ship’s boats with them.
Eventually, on August 14, 1833, the ice in

Prince Regent Sound relented sufficiently tolaunch the boats, and the party fled north,
to be rescued in Lancaster Sound on
August 25.
Is the current opening of the Northwest
Passage a similar freak of Nature; or will it
similarly turn out to be a one-year wonder.
The answer to this should become clear
later this year..
Return of the Ice
After its record retreat during September,
the Arctic sea ice made a slow start to its
winter recovery. Although the mean extent

www.geo-web.org.uk

So, while summer warming of the ocean
surface initially tends to hold back the
regrowth of wintertime sea ice, diminishing
sunlight as the seasons advance meansthat the nett rate of energy loss from theocean eventually increases. That heat loss,
in conjunction an unusually large area ofopen water, creates ideal conditions for the
rapid growth of new sea ice on a large
scale.
The NASA images reproduced in figure 8 andfigure 9 were created by Jesse Allen, using
data obtained courtesy of the National Snowand Ice Data Center (NSIDC).

References
1 The Disappearing Arctic Perennial Sea Ice
GEOQ 1, page 5
2 Blue Marble - GEOQ 9, page 13

7

March 2008

Meteosat-8 Orbit Anomaly
On Tuesday May 22, 2007, around
00:50 UT, Meteosat-8 experienced an
unplanned orbit change which included a
decrease in spin rate, change in attitude,
nutation, temperature changes and a small
drop in solar array power.
Intensive investigations revealed thatdamage had been sustained close to oneof the radial thruster pairs and it seems
likely that Meteosat-8 suffered a collision
with a micro-meteorite or particle of spacedebris. Subsequent tests have shown theimaging system to have been unaffected by
the incident.
The Unified Propulsion, Thermal Control
and the Electrical Power sub-systems were
all affected; in particular, one of thethrusters used for east-west stationkeeping manoeuvres was damaged but the
redundant thruster has been tested and is
performing well.
The external surface of the satellite has
been damaged with the consequence thatsome internal components are now directly
exposed both to the cold of Space andsolar illumination as Meteosat-8 spins. Thismeans that a new thermal configuration will
be required to minimise the impact on thesatellite and to allow safe operation during
eclipse.
Overall, there should be no impact on
Meteosat-8’s ability to serve as the in-orbit
backup satellite and to provide the Rapid
Scanning service. However, a level ofredundancy has been lost and this could
have a longer-term impact on the satellite’s
availability.

Group for Earth Observation

Earth nearest the sun. However, nojustification for this belief is given.
Without boring readers with the maths, thefacts are that both mountains lie north of
the Tropic of Capricorn, and hence of thesun itself at local midsummer. Additionally,
Aucanquilcha lies 1°37’ of arc farther norththan Licancabur. This may seem trifling, but
equates to 113 kilometres due north on the
ground. Over this distance, the Earth’s
curvature carries the entire mountain of
Aucanquilcha, from base to summit, inexcess of a kilometre (1405 metres) farther
from the sun than Licancabur, more thansufficient to swamp its nominal heightadvantage of 256 metres [Editor].

Iceberg
While browsing through his full-world
Metop-A images on November 7 last year,
Alan Banks spotted this large iceberg,
designated A53a, drifting in the Southern
Ocean at 58°S, 46°W.

GEO Quarterly No 17

cloudy summer they recently endured,NASA climatologists have reported 2007 as
equal with 1998 as Earth’s second warmest
year during the past hundred. The greatest
degree of warming occurred in the Arctic,
as you can read in Arctic Meltdown (p 4).

David Taylor
The Problem
In a previous Script Snippet we explained
how a set of Metop AVHRR data could becompressed into Zip files fitting on tomultiple DVDs. The DVD recipient wanted
a way to play out these files into a
directory, one by one, over a period of one
day, so as to simulate the experience ofreceiving the data in real-time.
The Solution
FOR %%F IN (C:\MetopData\*.zip) DO (PKZIP25 -extract %%F
SLEEP 160)

Iceberg A53a
Image © EUMETSAT 2007

Nearest the Sun
We received an email from Hann Redwinregarding Peter Wakelin's explanation of
the point on Earth that comes closest to thesun (GEO Q16, page 3). He has
discovered a number of references on theInternet stating that the point on Earthnearest the Sun is Aucanquilcha (6186
metres, at 20°40’ south) and not
Licancabur. Haan quotes several
references, including:

Missing Images• www.climbfortibet.org/no_shadows.cfm• www.alpine-club.org.uk/news/
newsletters/2000/April-2000.doc

But all is not lost. Live webcam images ofKliuchevskoi are available fromThe gist of all the reports (which simply
cross reference each other) is a climb to
the mountain’s summit on December 30,
1999 by an eight-strong ‘Climb for Tibet’team. The team chose this mountainbecause they believed that, for a few
seconds that day, it would be the point on

Some of the best images of the volcano
can be viewed by following the ‘Best
Image’ link on the page above.

There was a reference in Robert Moore’s‘Kamchatka’ article last December to‘spectacular webcam images appearing
overleaf.’ Readers who looked in vain need
not worry. Although it was originallyplanned to incorporate such images,
repeated e-mails requesting permission to
do so went unanswered: so the images had
to be removed.

http://data.emsd.iks.ru/video/video.htm

Second Warmest Year
Although GEO readers in western Europe
might find it surprising in view of the wet,www.geo-web.org.uk

Explanation
Here we are using the FOR command toloop over all the Zip files in a particular
directory (C:\MetopData\) and act on each
Zip file. As before, I'm using PKWARE's
PKZIP (in a 32-bit Windows version) except
this time I am using the "-extract" command
to extract the Metop data contained in the
Zip file into the current directory. The %%Fvariable is replaced by the full Zip file nameas the second parameter to the PKZIP25
command.
The difference here is that inside the FOR
loop I have two command lines.
You can have as many command lines as
you need inside a FOR loop. The second
command is the SLEEP command. This
causes the script to pause for the specified
number of seconds, and hence emulates
the delay between the successive Metop
data chunks. You might want to use the
SLEEP command in a script which collects
live WebCam images - where the WebCamchanges every five minutes or so.
The SLEEP command is not built into
Windows. Whilst there are many versionsof SLEEP.exe on the Internet, I used theone from the Windows 2000 Resource Kit
which can be downloaded for free at
http://www.microsoft.com/
windows2000/techinfo/reskit/default.mspx

9

GEO Quarterly No 17Group for Earth Observation

March 2008

Terence Smith
Introduction
Without doubt, many professionals and experienced GEO
members alike are already well conversant with David Taylor’s
GeoSatSignal (GSS) software, its command file operation, syntax
and task scheduling. It is hoped that this article may enthuse andencourage readers, particularly the less experienced, to extend
their use of the software and experiment in areas not yet explored.
There is a significant learning curve to much of GSS, and for quitea while I had been using it solely for particular, basic imaging tasks;
it was only fairly recently that I began to delve more deeply into
what else could be achieved.
I had previously relied upon MSG Animator for live Meteosat
animations and, although GSS was not conceived to produce
these, this did seem a possibility. In his inimitable manner, David
Taylor has been instrumental in making adjustments to GSS tofacilitate this.
These notes relate specifically to my attempts to satisfactorily
automate GSS animations, initially of the 15-minute channel-09
Meteosat-8 and Meteosat-9 images, overlain with the Bracknell
Mean Sea Level Pressure 6-hourly isobaric charts, somethingoutwith the scope of MSG Animator.
Configuring GSS for Animations
Start by running GeoSatSignal, clicking <Job> on the menu-bar
and selecting a new Job number—in my case, Job-4. Next select<Options Job → setup> and configure each of the five tabs asfollows.
Processing Tab
Select False colour as either ‘Normal’ or ‘Day and Night’ (totaste), uncheck the Thermal FC and Fire boxes and selecteither ‘Stretch’ or ‘Histo equalise’ depending on personal
preference. I prefer to make my animations from images froma single infrared channel such as Channel-09 as this involves
less demanding processing. Should you prefer to create
animations from a visible channel (Channel-01 or -02) the
associated thermal and water vapour images are also loaded
by default to create colour composite images. This results inmuch more demanding processing while the animation is
being created, which may exceed the capability of some older
PCs.
Remapping Tab
The Enable remapping box at top left must be checked if you
are to create an animation. GSS automatically adjusts the
mapping to 1065 x 718 when Bracknell charts [1] are used as
overlays but it is still a good idea to check this under
Remapped image size for conformity, should you acquiredifferently sized charts from elsewhere.
For the same reason there is no need to alter the Map
projection or to enter any Meridian/Parallel/Span coordinates—the Bracknell overlay automatically dictates all
such matters. Now select the Bracknell option from theOverlay drop-down menu; you may wish to select a colour for
it to make a suitable contrast with your Meteosat image’s
palette.

10

Figure 1 - the Processing tab

Figure 2 - the Remapping tab• Finally, browse to the directory where your overlay files are

saved and ensure that it displays correctly in the Path field.
Leave Grid set to ‘none’ because a latitude/longitude grid isincorporated in the charts themselves.

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Group for Earth Observation

Animation Tab• If you are receiving 15-minute data from MSG-2 (Meteosat-9)
select the ‘15 mins’ Take picture every radio button; should
you also be receiving the Rapid Scan (MSG-1 RSS) 5-minutedata, then you can select ‘5mins’. A Loop delay of five to six
seconds (e.g. 5500 ms) can be useful to give an obvious break
if the animation is to be looped. The default Animation speed
should be satisfactory for 15-minute data but can be increased
to 5 frames per second or more if you wish for RSS.
• The Number of pictures figure should be chosen to reflect the
duration of animation you require, bearing in mind the available
RAM. For instance, 24 hours worth of 15-minute data (fourframes per hour) equates to a total of 96 frames: for 5-minutedata (12 frames per hour) this would amount to 288 frames. In
any event, it would be wise to start small with only a few frames
for testing, then increase this once everything is working
properly.
• Another point worth mentioning is that selecting Smoothanimation adds interpolated intermediate images, which
affords kinder transitions between the six-hourly charts.
• Generating a 100-frame animation of 15-minute data takes myPC approximately 5 minutes (because a frame is added to theanimation every three seconds). For 5-minute RSS data ananimation covering the same duration will therefore take nearly
15 minutes (three times as many frames per minute). This is
close to your likely animation update period, which might
possibly interfere with the processing. A more modern PC
should accomplish this considerably faster.
• If GSS is running continuously in the background, it mightprove safest to start the program at a specific time; noting thatthe refresh period will commence from that time. You can set
the time for the scheduled animation build to a point just after
this, which will not interfere with a refresh.
• I have found that there is a propensity for the processes to lockup on my P4 computer, requiring a restart, and suspect that thismay occur because of some conflict between refreshing andanimation builds. This is another reason I set refresh to 15
minutes, even when processing 5 minute data.
The RSS trial period is now over, but these transmissions may
become fully operational some time during 2008.

GEO Quarterly No 17

Figure 3 - the Animation tab

Annotation Tab• The most useful feature of this tab (not illustrated) is the option to
add country boundaries. Check the Country boundary box andselect a colour that shows well against your images.
• Whilst not strictly necessary, since the Bracknell chart has thisanyway, there can be justification for a coloured boundary whichshows up land masses more clearly when they are cloud-covered.

General Tab• First, assign this Job a name, ‘MSLP-IR9’ in my case (figure 4) thenuse the ‘Browse’ button next to Path to data files to select the path
to your HRIT image files (usually processed by MSG DataManager).
Likewise, set Path to result files to the directory where you plan tostore your animation files. The Wildcard specification box permits
easy loading of the latest image into the program. Figure 4 shows
the setting I use for my latest Meteosat-9 image.
‘C:\MSG-2\Images\HRIT\%yyyy\%mm\%dd\*ch09.jpg’• Finally, set the Refresh minutes field to ‘15’. If this option is
missing, you must update to the current version of GSS. This option
provides the foundation for automating your animations, which will
refresh at the chosen intervals. It is a really useful facility which will
regularly update a static image as well as any associated overlay.
Your displayed picture will always be the latest one while GSS is
running.
• Unless you wish to adjust the Temperature range (applicable if you
select a thermal false-colour image for your animation), allremaining items under this tab can be left with their default settings.
• Although it is possible, with a fairly up-to-date and fast computer, tobuild RSS animations (with a limited number of frames) at fiveminute intervals, this is not always practicable. Even with the Take
picture every setting (figure 2) set at five minutes for RSS, it isperhaps more sensible to ‘refresh’ only every 15 minutes, to ensurethat the current animation is fully built before the program tries to

Figure 4 - the General tab

start the next build. On my 2.4 GHz P4 PC with 1.5 GB RAM, it cantake nearly ten minutes to build a 200+ frame animation. For 15
minute data this ceases to be a problem unless you are animating avery large number of frames.

Obtaining the Bracknell Overlay Charts
The easiest method to achieve this is through the Autoget utility
bundled with GSS. Charts can be downloaded manually by ticking
the box beside ‘Bracknell’ on the Weather data tab and clicking‘Run’. Autoget automatically creates the directory ‘C:\Bracknell’ andsaves the charts there, using the same ‘year/month/day’ tree
structure that MSG DataManager uses for its images. GSS willcollect its overlays from this ‘Bracknell’ directory. More usefully,
Autoget can be activated automatically four or more times per day
via the MS Windows Task Scheduler and a Command File asdiscussed below. Once you are reliably downloading the Bracknell
charts, the four files each day, namely ‘bracka_0000.gif’,‘bracka_0600.gif’, ‘bracka_1200.gif’ and ‘bracka_1800.gif’ will besaved in the designated folder.

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GEO Quarterly No 17Group for Earth Observation

One small point to note is that old data are not automaticallydeleted from the Bracknell directory. You have to manage this task
manually from time to time. You can use David Taylor’s free
TrimTree program to do this for you.
Making an Initial Test
Now that the setup procedures are complete, run GSS for a spelland check for the correct opening of the ‘Latest file’. Check alsothat the first build of the animation has occurred and that it plays
back correctly.
By this stage, you should have an image, refreshing with the latest
data at the chosen intervals, and creating an animation that can be
replayed later, but only by manual selection.
Updating the Animation
What is lacking at this point is an updating animation. To achieve
this requires use of a Command File and the Microsoft Windows
Scheduler. Being somewhat conservative, I am still happily using
Windows 2000 Pro SP4 for most of my image reception andprocessing but I do have some experience of scheduling withXP Pro on a laptop. The scheduling method is effectively the samefor both. If Vista scheduler operates differently, perhaps readers
can write in and explain.
Command Files
Two separate command files are necessary, one to activate
Autoget at least four times a day to download the Bracknell Chart,
and another to run the Animate command in GSS, ideally every
15 minutes. These command files are easily created using your
Notepad utility, which can be found from the Windows Start Menu
under ‘Programs/Accessories’.
The Autoget Command File
Open Notepad and type in the command instructions for Autoget.
This does not need a full path because the command file will besaved in the same directory as the Autoget.exe file (the GSS
directory). The line should read something like
Autoget.exe -brack -close

which opens Autoget, downloads the Bracknell chart file thencloses Autoget again. Save this file into the GSS directory as‘Autoget.cmd’.

March 2008

The job number used must be the one that you gave the identifying
name ‘MSLP-IR9’ and which assumes the file name ‘MSLP-IR9.avi’for the animation. The ‘-min’ command runs the programme
minimised, but can be temporarily removed while testing andchecking that the command file operates satisfactorily.
Scheduling the Command Files
Access to the Scheduler via Windows <Control Panel → Scheduled
Tasks>. There are two methods one can use when preparing aschedule to run a command file: a ‘multiple schedule’, where eachprogram run is listed separately for the required times, or the task
can be entered once only with its repetitions occurring at specified
intervals defined under ‘Advanced Schedule Options’. For reasons
which I do not actually understand, I have found the former
arrangement to be more reliable, even though it is a little moretedious to set up.
Scheduling Autoget
Open the <Scheduled Tasks> window and double-click ‘Add
Scheduled Task’ to open the Task Wizard, click ‘Next’ and browse
for the GSS directory (where the Autoget.exe and Autoget.cmd fileslie) and double-click on ‘Autoget.cmd’ to select it. Select ‘Daily’ andclick ‘Next’ again.
The next screen shows the current date and time as defaults.
Select ‘Every Day’ and continue to the next dialogue box where
you must enter your Username and Password; if you do not do
this, the schedule may not operate. Click ‘Next’ for the last timeand you will be informed that the task has been successfullyscheduled . . . but do not click the ‘Finish’ button yet!
Check the Open advanced properties box then click the ‘Finish’button to reveal a fresh dialogue box with four tabs. The Task tab
confirms the path to Autoget.cmd as well as the Username
selected earlier. At bottom left is a check-box where you canenable or disable the schedule once it has been configured. Leave
this checked.
The Schedule tab should confirm the ‘Daily’ schedule. You shouldchange the default value for Start Time to ‘00:10’—ten minutes
after the hour. The Schedule Task Daily box should show its
default value of every ‘1’ day(s).
Click the adjacent Advanced button which will show a dialogue
box (figure 6) indicating the current date as the Start Date. Check
the Repeat task box to activating the fields beneath.

The Animation Command File
Open a new file within Notepad and type a line such as
Geosatsignal.exe C:\MSG-1\Images\HRIT\*.ch09.jpg j4 anim:C:\MSG-1\animations\MSLP-IR9.avi -min -close(Note: this is really a single line, but wraps round two lines whenprinted on this page. It contains two space characters, one eitherside of the ‘j4’.)

The Bracknell files are not reliably available at the expected hours
of 0000, 0600, 1200 and 1800, so I hedge my bets and ensure upto-date downloading by activating Autoget more than just fourtimes each day. The download is so quick that I suggest setting

Save this file as ‘GSSanim.cmd’ into the GSS directory.
This command opens GSS in ‘minimised’ configuration (as an iconon the Taskbar), opens the latest Channel_09 IR file, activates
Job 4 and builds the animation set up within it, then closes GSS.

Figure 5 - Downloading Bracknell charts with Autoget

12

Figure 6 - The Advanced tab in MS Scheduler

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March 2008

Group for Earth Observation

GEO Quarterly No 17

This July 29, 2007 Meteosat-9 Channel-9 IR image was processed using a modified LUTLandSea-zw2 palette (image © EUMETSAT 2007)

This October 19, 2007 Meteosat-9 Channel-9 IR image was processed using the ‘Normal’ false-colour option (image © EUMETSAT 2007)www.geo-web.org.uk

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GEO Quarterly No 17Group for Earth Observation

March 2008

Repeat task to ‘Every 3 hours’ (or even every hour) to makeabsolutely certain.
Next check the Duration button and enter 23 hours 59 minutes;
this is the total period during which these activations will take place
every day. Click ‘OK’ to return to the main Scheduled Tasks
window showing, for example, your new task ‘Autoget’ scheduled
as ‘Every 3 hours from 00:10 for 23 hours every day, starting
dd/mm/yyyy’. Make sure that <View → Details> is checked on the‘Scheduled tasks’ menu bar and columns will display showing ‘Next
Run Time’, ‘Last Run Time’ and ‘Status’ (figure 7).
At this stage, the Last run time will say 'Never'. In the left handcolumn, right click Autoget then click 'Run'. If all is well, theprogram will activate and download a Bracknell file. Should any
problem manifest itself, use Explorer to locate and double-click the
Autoget.cmd file in order to run it. If this works satisfactorily, thenthe difficulty lies within the Scheduled Task configuration. Usually,
any failure of the scheduled task to run shows up in the Status
column as ‘Could not start’.

Figure 8 - Multiple option in MS Scheduler

Figure 7 - Schedule status information

Note: If you run a single-PC system, avoid timing this task while
the animation is building.
Scheduling GeoSatSignal
Now we can repeat the above for the scheduled activation of the
GSS command file, which will build a new animation every
15 minutes. This will be done using the ‘Multiple Schedule’ method(figure 8).
Add a new scheduled task, this time based on the ‘GSSanim.cmd’command file. The task will be called ‘GSSanim’. Repeat
everything in the previous paragraph until reaching the Scheduletab, where you must check the Show multiple schedules box.
This opens a hidden dialogue line at the top of the window where
you may add new lines, one for each task in the day’s schedule.
To allow time for the addition of each updated image to theanimation, I suggest that the first task again starts at 00:10 hours.
Add new lines for 00:25 hours, 00:40 hours and so on, for eachsuccessive 15 minute interval. This will take a few minutes but,once done, is there for good. Once the list is complete, click ‘OK’and the schedule will be added to the Scheduled Tasks list. The
only difference will be that the Schedule column (figure 7) will show
as ‘Multiple schedule times’, and Status will state ‘Running’ once
the first activation has commenced. Again, the command file canbe tested on its own, and the Schedule can be checked by forcing
a 'Run' as described for the Autoget schedule.
The Command Window
By now you should have noticed an irritating problem when runningcommand files. While each task is running, a command window
pops up smack in the middle of your screen, regardless of whether
that task itself is minimised.
This annoyance is surmountable however. Open a new command
window via <Programs/Accessories/Command Prompt>. Right-click
the title bar then click Properties on the drop-down menu. In the
dialogue box which opens, select the Layout tab, adjust the Sizeand Position parameters as preferred and uncheck the Let
system position window box. As a guide, a width of 100 andheight of 10 will produce a shallow window. If using 1024x768
screen resolution, a left position of 50 and Top position of 760 will
centre the window, almost out of sight at the bottom of the screen,

14

where it can be raised or extended upward with the cursor if
required. In everyday use its presence will scarcely be noticed.
Displaying Animations in GeoSatSignal
You ought by now to have an automated animation which only
needs to be displayed. You can view your animations using asecond installation of GeoSatSignal, either on the same PC or on asecond networked computer.
The second instance of GSS must be installed in its own uniquefolder and its executive file renamed—as Geosatsignal2.exe forexample. This is configured with a new Job as follows.
General Tab• The job name must be identical with that used in the original Job
setup, in this case ‘MSLP-IR9’. The Path to data files field should
be browsed to the home of the AVI file; the Path to results files is,for convenience, set to the location of the AVI animation file(whether on the same computer or on a remote networked one).
• The important entry is the Wildcard specification, which should
carry the path to the AVI file and its name—e.g. ‘C:\MSG2\Animations\mslp-ir9.avi’. The final significant setting is that of theRefresh minutes box which should be set to 15 minutes (or 5minutes if animating RSS). See figure 9.

Processing Tab• Here, False colour should be set to ‘none’, Thermal FC andFire should be unchecked, CLUTs set to ‘none’—indeed, allfields set to minimum.
Remapping Tab• Enable remapping must be unchecked.

Animation Tab• Select 5 mins or 15 mins (but this is unimportant, even thenumber of pictures can remain at ‘1’).
Annotation Tab• Leave in default settings.
Important Finalisation Step
It is vital that, once these specific job settings have been entered,and that window has been closed, you open the <File> menu andclick File/Open Latest. This ensures that the path to the animation
file is saved correctly.

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GEO Quarterly No 17

Additionally, when initially opening the display installation of GSS,
the menu tabs work as expected. But after a while these become
ineffective: the ‘Open’ button blacks out and, even though theanimation is still running and updating, it is impossible to control it
or close it without resorting to Task Manager.
All these tendencies seem most notable with single processor PCs,
even P4s with 1.5 GB of Ram. A new 2.13 GHz C2D Intel
computer with 3 GB RAM keeps the displayed GSS animation
running and updating without problem thus far for about twelve
hours, although all control via the menu tabs has been lost.
Behind these idiosyncrasies there may well be software or
programming reasons which are obvious to the professionals, but
beyond comprehension to the likes of me.
Manual Display of Animations in IrfanView
These difficulties led me to seek an alternative means of displaying
the animation using the freeware image handling programme
IrfanView. This can be downloaded fromhttp://www.irfanview.de

Figure 9 - the General tab for playing back animations

There seems to be a glitch in GSS which may otherwise return thepath to default or clear it from its field altogether. Unfortunately, theOpen latest command will not actually activate until a different Job
is briefly selected and the MSLP-IR9 job is reselected. Following
this manoeuvre, it should be possible to access the Open latest
command. I do not pretend to understand this slightly odd
behaviour, but it manifests itself on each copy of the program
installed on several different computers. It may also prove
expedient to just once open the animation by means of the Openbutton under the job’s Animation tab.
If the displaying program is remote from the computer which builds
the animations, then mapping that network drive could speed
matters up.
Finally, close the setup window and click the Animation tab, thelast on the right in the GSS main window. All things being equal,
the animation should run. If, for some reason, it does not, then justclick the Open button and browse to the location of the AVI file andopen it, and your overlaid images should be displayed in all theirglory. This should update to the latest animation build every
15 minutes without further intervention. In the unlikely event that
there is a report that it cannot find or open the file, this indicatesthat the last animation build failed to complete, for some reason orother, and may need restarting manually.
When the display installation of GSS is run for the first time(refreshing every 15 minutes), it must be started between the endof one animation build and the commencement of the next toprevent conflict between the two running instances of GSS,
otherwise the display version will each quarter-of-an-hour, attempt
to load a file that is still being written to disk.
Teething Troubles
With both Windows 2000 and XP there has been a tendency(whether networked or on the same PC) for either the animationbuild or the display installation of GSS to freeze after a while. Thisrequires either task to be ended via Windows Task Manager—and
this by means of ending the process rather than just theapplication. Oddly, I have also noted that, when 5-minute RSS data
is being animated, such a lock-up returns the frames to 15 minutedata, despite the job setup still requesting 5 minute frames. After alock-up, I also experience intermittent error messages relating topermission to view the animation file and refusing to overwrite thefile; this can necessitate a reboot/restart.

Once installed, click <File/Open> and browse to the location of youranimation file. A double-click on the file will open and start the
animation. A press of the ‘Enter’ key will immediately hide thestatus, tool and caption bars and display only the animation onscreen. <View> on the menu-bar reveals ‘hide’ options for thevarious bars and affords a full-screen view with a useful slide-bar
at the bottom.
Under the <Options/Properties> ‘Video/Sound’ tab is the ‘Loop’option. A really useful feature of Irfanview version 4 is a slide barthat shows at the bottom of the screen in full-screen view. If you
have a fast processor with plenty memory, it is possible to hold the
cursor on the slide and run a smoothed 300 frame animation
backwards or forwards very quickly. On a Core2Duo 6420
2.13 GHz PC with 3 GB RAM this is almost instantaneous, but a
1 GHz Pentium 4 struggles somewhat. The very handy HotKey‘Shift+R’ immediately reopens the animation with the latest frame
added.
Automated Display of Animations in IrfanView
To achieve a fully automated animation display using Irfanview you
must create a command file (named e.g. ‘IrfanMSLPanim.cmd’)i_view32.exe C\MSG-2\animations\mslp-ir9.avi /hide=15 /oneand schedule this as described above for automating GSS. This
command string will open Irfanview, display the animation and,after the chosen interval (15 minutes being the ideal here), close it
down then immediately reopen Irfanview displaying the updated
animation (with the latest frame newly added).
The ‘IrfanMSLPanim.cmd’ file must be placed in the Irfanview
directory. The command ‘/hide=15’ effects full-screen viewing withthe removal from the display of the tool, menu, status and caption
bars, whilst the ‘/one’ suffix forces the closure of the displayed
instance of Irfanview as the fresh one opens. (See the Irfanview
Help file for alternative command options).
Timing Considerations
It is imperative that the repetition times for the schedule are set tofall after completion of each GSS animation build, otherwise failure
to start and accompanying error messages will occur. As withalmost all satellite real-time imagery reception, accurate time
setting is crucial, particularly if networked computers are
involved. I would recommend automatic computer time-setting by
an NTP program such as Tardis 2000, which can be downloaded
fromwww.kaska.demon.co.uk

For reliability, the schedule would also best be of the multiple
variety rather than a simple ‘repeat task’ format. To obviatelaborious multiple 15 minute schedule construction, it is worth... concluded on page 44

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GEO Quarterly No 17Group for Earth Observation

GEO company secretary Nadine Bellon the News 14 Carolina presenters’ desk

Francis Bell in front of the ‘green screen’ practising a mock weather
presentation (but really just learning his left from his right).

The newsroom at News 14 Carolina

Francis Bell giving some GEO Quarterlies to Gary Stevenson,
News 14 Carolina’s senior weather forecaster

Here is another example in our occasional series featuring unusual photographs ofreception antennas. The photo was taken outside the University of Surry’s School ofManagement building by Francis Bell during the AMSAT-UK colloquium last July. GEO had
been invited to demonstrate the reception of weather satellite signals and the best view ofthe sky proved to be from a corner of the ornamental pool. The photograph was taken
while the dish was providing excellent live signals into the meeting area for two sets ofcomputers. And yes: the cable did run underwater for several metres!

16

March 2008

www.geo-web.org.uk

Neil Thackrey, who resides six kilometres into themountains some 25 km east of Malaga, Spain, sent GEO
this splendid photograph of a waterspout. Neil wrote: “We
had severe electric storms over the Christmas period,
culminating in this wonderful waterspout on the morningof the December 26. The only downside of the storms
was the power cut we experienced on Christmas Eve.
The power did not came back on for 12 hours.

March 2008

Group for Earth Observation

GEO Quarterly No 17

Francis Bell
Regular readers of GEO Quarterly will know that I sometimes
report my experiences in America. In the past I have taken myportable APT system with me and received some excellent live
NOAA 17 and NOAA 18 APT images [1]. On one of our outward
flights I took some interesting aerial photographs of Greenland
and Canada which were subsequently published [2].
The background reason for our regular visits to America is tosee our son Christopher, his wife and young family: ourgrandchildren. Christopher moved to America in 2003 following
his career in computing and IT.
He settled in Raleigh, North Carolina, in a region looselybounded by Raleigh, Durham and Chapel Hill which has
communications, pharmaceutical, computer and IT companies
located within it and is aptly described as the ‘Research
Triangle’. The region has the assets of good communications,
physical space for development, adjacent universities and an
equable climate.
Christopher’s job was initially connected with the computing
side of the Time Warner group, who run the CNN station which
can be received by satellite in most parts of the world. But earlyin 2007, he moved to a Time Warner TV station called News 14
Carolina. Christopher’s job seems to be to trouble-shootanything relating to the station’s hardware or software whichneeds immediate attention. Of course, when I discovered what
his new job was, I asked him if it would be possible to arrange
an opportunity for us to look around the station when we next
visited. This was duly agreed.

Forecasters
The station has four
permanent weather forecasters, at least one being on duty at all
times. We were pleased to meet Gary Stevenson, the station’s
senior forecaster, who briefly showed us around his office anddescribed the background sources of data which he uses forweather forecasting. We looked around the forecasting team’s
studio and sat at their desk, where we offered a mock weather
forecast—which, fortunately, was not broadcast!
A forecaster stands in front of a plain green background where
his image and the weather map or diagram are combined. The
green from the background of the forecaster’s image is thenelectronically removed, making it look as if he is standing infront of the subject map. The most gymnastic mental exercise I
tried was standing in front of this green background.
Now that sounds simple enough, but what the forecaster sees of
the combined images in the monitor is a mirror image of
himself. Presentation skills have to be learned, because in thesecircumstances, when you move your right arm (as viewed via
the monitor), it looks to be the left one. I briefly had a go at this
and, after a minute or two, began to get the hang of a reflected
image of myself appearing on the monitor. Well, I shave every
morning so I do know my mirror image.
The comments here are not trivial: apparently Gary Stevenson,
experienced as he is, will, when giving a live forecast,sometimes gently shake his left wrist as if to adjust the positionof his wrist watch. In fact he told me he does this to check theorientation of his image on the combined screen.
Later in the evening, after leaving the station, I had thiscunning idea: instead of the forecaster looking directly at amonitor display of himself and the background map, why notlook at the monitor via a mirror? The forecaster would then becorrectly orientated. However, with a I little further mental
analysis I recognised that if this were done the forecaster would
be correctly imaged but the map would be seen as a reflection.
It would be a bit tricky for the public if this was the transmitted
image; it would also require more mental gymnastics from theforecaster to faultlessly and instantly sort out, for example,
south east from north west looking at a reflected map.
Eventually I concluded it was better to leave the system alone
and let the forecaster mentally sort out left and right hands.
The station content and forecasts for North Carolina can befound at their web site

The control room at News 14 Carolina

News 14 Carolina is a 24 hour cable station based in Raleighbut has sister stations in Greensborough and Charlotte, serving
a total potential audience of about two million people. The
output from the station is mainly weather forecasting, weather
related topics and news, the balance being determined by the
dynamics of the weather. In settled times this area does have adelightful climate, so perhaps only 15% of air time is spentcovering the weather. However, the region is also on the edge ofpossible Atlantic hurricanes coming from the southeast andthunderstorms with potential tornados arriving from the west.
When these extreme weather conditions prevail, the TV station
can go into 100% weather mode.

http//www.new14.com

My sincere thanks to Gary Stevenson and his colleagues attheir TV station. All were friendly and allowed us to lookaround their busy facilities without obstruction. For my part I
left Gary with a few copies of GEO Quarterly which I’m sure
will be distributed to those who look after the weather
forecasting at their busy News 14 Carolina station.
References
1 Peripatetic APT - GEO Q15, September 2007, page 45.
2 Cape Farewell - GEO Q13, March 2007, page 17.

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GEO Quarterly No 17Group for Earth Observation

March 2008

Ed Murashie

It’s time to start focussing on LRIT.
Just as GVAR (GOES Variable Format)
was developed to meet the demand formore timely data and flexible
scheduling for high resolution data,
LRIT was likewise developed for lower
resolution data. LRIT also has theadded advantage of supplying morequantitative digital data.

WEFAX

LRIT

Subcarrier frequency

2400 Hznone

Subcarrier modulation

80% maximum AM

none

Data rate

Comparable 30 kbps

1 2 8 kb p s

Carrier frequency

1691 MHz

1691 MHz

Carrier modulation

FM - analogue

BPSK - digital

Bandwidth

30 kHz300 kHzEIRP (power)

54.4 dBm

48.5 dBm

Error correction

None

Viterbi/Reed-Solomon

Data Framing

Start signal 300 Hz for 3 sec
Phasing signal for 5 sec
Stop signal 450 Hz for 5 sec

32-bit sync. pattern
Header blocks

LRIT is the digital replacement foranalogue WEFAX, on the sametransponder frequency of 1691 MHz.
NOAA has touted that LRIT can bereceived with the same hardware by
simply replacing the VHF FM receiverwith a digital receiver and different
software. They have provided a
website,V i deo

800 pixels × 800 lines[2853 × 983] to [5199 × 4734]

Minimum spatial resolution

7 km

4 km (Vis, IR); 8 km (WV)

http://noaasis.noaa.gov/LRIT/

Max greyscale resolution

64 level for C/N > 10dB

256 levels

with general LRIT information, sample
data files, data format and receiverspecifications and uncompiled
software. They also provide an email
address for general inquires,lrit@noaa.gov

First Steps
When I became divorced 13 years ago,
I moved from one apartment toanother. About two years ago I actually
moved back into the same complex
where my ex-wife and I first lived
before we bought a house. One of the
few memories I have of that firstapartment was sitting in the livingroom with my home-built Hamtronics
receiver and a cable running throughthe dining room and out to the patio.
There I had a Microwave Modules
down-converter connected to a coffeecan feedhorn mounted to a 3 footaluminum snow saucer (a circularchild’s toboggan). I sat tweaking thecoils until I could hear a scratchy
WEFAX signal while my then-wifelooked at me dumfounded.
I knew that someday I wanted to getback to tweaking on weather satellite
hardware, so when I moved back, I
waited until one of the backapartments was open so that I had noneighbours behind me to complain
about antennas. The apartments are
all single-story, have large 8 foot by 20
foot patios—and my patio was on thenorth side of the apartment.

18

Table 1 - A quick comparison between WEFAX and LRIT

When I finally got permission to put up
the antenna this year, I first had tofigure out what size of dish was
required. Decoding the LRIT signal is acomplex task, with two forms of error
checking, Viterbi at the bit level andReed-Solomon at the block level. After
understanding the LRIT decoding
process, I realised that you have toperform the Viterbi decoding process
but not the Reed-Solomon, provided
you have a high enough signal-to-noise
ratio. Realising that the 4-foot dishsome companies use would be on thesmall and while my patio was 8 feetwide, I decided to try a 6 foot dish.
Wouldn’t you know it; I have a 10 foot,
4 foot, 3 foot and 2 foot dish! A quick
search on eBay showed a new solid 6
foot Fotec Star model FC-06 dish for$100, which included a ring base. After
winning the auction, I drove two hours
to San Diego and picked it up.
Mounting and Connecting the Dish
The next challenge was getting theantenna ring-mount on to a 5 footplatform so that it could ‘see’ over theapartment roof when at a 50° angle
pointing at GOES-W (GOES-11). Dads
are wonderful people and I am lucky tohave such a nice one living nearby.
This is the same gentleman who hadthe ‘Weather Satellite Picture Receiving
Stations’ NASA publication, describing
how to build that $30,000 station, in

www.geo-web.org.uk

his library at work when I was thirteen.
He was a high school electronics andwood shop teacher and is very
resourceful. He studied my problem
and decided the best thing to do was tobuild a wood base and attach the baseto -inch conduit, bent in upside
down U-shapes, for added support.
Really, this just gave him anotherexcuse to dig out the pipe bender. I
have never seen a person make so

Figure 1 - The mounted 6-foot dish

March 2008

Group for Earth Observation

many things out of conduit. When I got the base home, I
quickly mounted the dish using cement anchors to get theright height and firmness even during the strong Santa Ana
wind conditions.
I mounted a coffee-can style feedhorn with a Down East
Microwave kit-built 1691 MHz LNA preamp on to theantenna and covered the assembly with a plastic bucket. A
20-foot length of RG9913 co-ax connected to this preamppasses through a spare bedroom wall to a 6 foot table that
holds my equipment, where it links up with a 31 dB
Wilmanco model 1698 amplifier. I measured the GOES-11

Figure 2 - CM701 modem (top left) and Wilmanco preamp (bottom)

signal coming out of the Wilmanco amplifier at -58 dBm.
This same combination was used many years ago for an old
WEFAX station. My LNA has a 0.8 dB noise figure and a
14 dB gain. Nowadays, the kit form is long gone and Down
East Microwave now sells only a pre-built version for $120.
Demodulating the Signal
Now I needed to BPSK demodulate the signal and performthe Viterbi error detection and correction process. I studied
Viterbi and found it to be a long process; I really did not lookforward to programming a Field Programmable Gate Array(FPGA) to perform the task. I had many BPSK/PSK
demodulators from my work with GVAR, GMS and HRPT.
One day I was looking through eBay (a recurring theme inthis article) and I saw mention of satellite modems. A
Comstream/Radyne modem caught my attention so I looked
it up on the Internet and found the operator’s manual. It
mentioned 70 MHz, 140 MHz, L-Band, BPSK, QPSK, Viterbi
and Reed-Solomon—all the right words. Next thing you
know, I am the proud owner of two CM701 modems with the
70 MHz, 140 MHz and L-Band plug-in cards. The CM701 is
a versatile modem built around a main frame with power
supply and user interface and separate demodulator,
modulator, Reed-Solomon and interface cards. I plugged in
the L-Band demodulator card, connected the Wilmanco
amplifier’s output to the modem’s input, turned on themodem, entered the carrier frequency (1691 MHz) and thesymbol rate (293.000 ksymbol/s). To my disappointment,
although I was getting a nice strong input reading, themodem did not lock on. Now what? Was the modem not

GEO Quarterly No 17

working? Did I have the wrong setting? Was it the wrong
type of Viterbi decoding?
I have heard many things about needing the correct filtering(especially from my good friend George Isleib at GTI
Electronics) to eliminate the EMWIN signal that is on theside skirt of the LRIT signal. Maybe it was interfering with
LRIT and preventing the modem from locking on. Building anarrow filter at 1691 MHz is impossible so I figured thesignal had to be down-converted to 70 MHz or lower.
Fortunately I still had an old Microwave Modules 1691 MHz
to 70 MHz down-converter in my junk box. As for a filter, I
studied using either a SAW
filter or a TOKO coil filter.
Just about the time I was
getting ready to order them,
I saw a surplus 70 MHz
bandwidth switchable SAW
filter on eBay for about $50.
I bought it and hooked up
the down-converter to theWilmanco amplifier and thento the filter. The results lookpromising on the spectrum
Figure 3 - Trace showing EMWIN
analyser; however the(tallest peak) and LRIT (next tallest)
modem still refused to lockon. Playing with the modem settings I could get it to lock on
randomly, but for no more than a few seconds at a time.
PC Interface
Lucky I still have a few friends in the industry like George at
GTI and Rick and Allan at Quorum Communications. I calledup Rick, told him my problem and he passed me over toAllan because he had remembered something about the data
rate. Allan immediately knew what my problem was andhow to fix it. All of the NOAA documentation refers to a data
rate of 293 ksymbol/s when the exact rate is293.883 ksymbol/s. I entered that rate into the modem andits green sync light immediately switched on. I was elated to
say the least! I tried removing the filter, down converter andreplacing the 70 MHz demodulator card with the L-Bandcard. Once again the system locked on. So the receiverchain is simple. I have a 6 foot dish with a preamp outside,a short run of co-ax to a line amplifier and Comstream
CM701 L-Band modem indoors. The block diagram for thesystem is shown in figure 4.
Long before my software defined radio (SDR) talk at the GEO
Symposium in 2005, I had been reading and studying SDR
technology. I had programmed with FPGAs for previous
satellite ingest boards and knew that FPGAs were the heartof SDRs. I had programmed with the Lattice and Altera
FPGAs but knew that I would be better using Xilinx FPGAs
since they offer the largest free source of cores, including
filtering and multiplier cores, that could be used to build a
SDR. A core is a logical building block that can be very
complex, thus saving you time from having to create that

Figure 4 - Block diagram of the author’s LRIT system

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GEO Quarterly No 17Group for Earth Observation

March 2008

Figure 5 - PC Interface Schematicfunction yourself. Knowing that I wanted to build a SDR
using Xilinx, I bought a Xilinx SpartanII XC2S100 demoboard for $79 years ago (figure 6). So I dug it out of my junkbox, dusted it off and wired up a simple Maxim MAX3094
RS422 interface integrated circuit to two of the FPGA I/O
pins, one for clock and one for data. The CM701 modem has
RS422 differential outputs on one of the 9-pin interface
connectors. The Maxim chip converts the differential RS422
signals to single-ended inputs that can be connected to the
FPGA.
Now how was I going to get the FPGA output into the PC sothat I could process and save the data? I knew that I wanted
to use a notebook PC for convenience, which ruled out ISA
or PCI plug-in boards. Most notebooks today don’t have
RS232 ports and a few don’t even have a parallel printerport—so these were ruled out too. This only leaves theuniversal serial bus (USB) port which could handle thespeed and was being used in the GTI and Quorum designs.
So I now had to become a USB expert in addition to a LRIT
and Xilinx expert? I have worked with long time mentor andweather satellite expert, John Dubois, for years.
You may remember John as being the first amateur toreceive GOES high resolution images and for designing an
APT patch antenna using housing insulation material. John
introduced me to an RS232 to USB interface chip from
Future Technology Devices International (FTDI) and said it
made it a snap to add USB functionality to a design. I looked
the website over and found they not only made a USB to
FIFO (first in first out) chip that came with the computer
drivers, but they made it in a module form to. That allows
me to simply connect power, 8 data lines, a read and write
line plus a transmit
buffer, empty andreceive buffer fullhandshake linefrom the USB
module to the
FPGA. FTDI
provides a DLL low
level driver andhigh level driverthat make themodule look like a
PC COM port. It
could not be much
Figure 6 - The FPGA board

20

simpler. Now I must say this is probably overkill, and could
be done with a cheaper USB microcontroller; but in the end
I want to add the SDR capability to the board, so for me thisis the way to go.
FPGA Code Development
The plan was simple: take small steps because the NOAA
documentation is slim and I will have to learn a lot on theway. For the first test, I programmed the FPGA with an
exclusive OR gate feeding a 32-bit shift register, a 32-bit
comparator and a sync-detect latch connected to an LED.
The modem data enters the FPGA, passes through theexclusive OR gate and then into the shift register. The
output of the shift register is compared with the block
synchronisation pattern, 1ACFFC1D hex.
The output the comparator is latched and will turn on an
LED if the bit pattern is detected. The exclusive OR is usedbecause of the nature of the NRZ-L bit data. The output of
NRZ-L changes when the input changes. This is not to saythat the output will be a ‘1’ when the input is a ‘1’ andchange to a ‘0’ when the input changes to a ‘0’. If the systemstarts with an output of ‘0’ from an input of ‘1’, the opposite
will also happen. So the exclusive OR has one input tied to aswitch on the demo board that can be toggled between a ‘1’and ‘0’. The nature of an exclusive OR is that’ if the control
input (the one tied to the switch) is ‘1’ then the output willbe the opposite of the input. If the control is a ‘0’ then the
output will be the same as the input. This is how the initialambiguity of NRZ-L is removed. It was done manually at first
but was later made automatic. When the system was turned
on, the LED lit and I knew that I most likely had data, andwas again elated.
Next I had to decide how best to share the processing
between the FPGA and the PC. Being a slow data rate, I
decided to keep most of it in the PC for flexibility and update
convenience. I would have the FPGA only detect sync,
remove the pseudo number randomisation that is applied tothe data stream and count off the bytes until the next sync.
I set off to program the FPGA and write the PC code, which I
will describe in a future article. When all was said and done,
I received my first images on the PC and knew that I had
won the LRIT battle.
The FPGA schematic based code can be found at

www.geo-web.org.uk

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GEO Quarterly No 17

Figure 7 - Top Level FPGA Code

Figure 8
LRIT Sync FPGA Module

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March 2008

FPGA Coding Details
The top level schematic, LRITsch (figure 7), contains
IOBUF8 and LRITSync schematics and bitctr, caductr andsyncctr counter macros. IOBUF8 (figure 9) is a tristate
buffer that controls the flow of data into and out of the
FIFO USB chip.
LRITSync (figure 8) contains a two-bit I/O latch with bit0
used to invert the input data to remove NRZ-L ambiguity.
Bit1 is used to clear the sync circuit. Both bits arecontrolled by the PC software through the USB chip. The
data can be inverted by an exclusive OR gate before
entering two 16-bit cascaded shift registers. The output of
the shift registers is compared to the 1ACFFC1D synccode using two 16-bit comparators. When there is amatch, the comparator output is latched.
Data is shifted into an 8-bit shift register (SR8CE) on the
LRITsch page. When sync has been detected, bitctr andcaductr counters are enabled. Bitctr counts off the data
bits, and on count 7, writes the SR8CE data to the FIFO
through the IOBUF8. Caductr counts off the 8160 bits of
CADU data and then enables the synctr counter. Syncctr
counts off the 32 bits of sync and then rests both itself
and the caductr counter. The SR8CLE shift register andoutput exclusive ORs form the pseudo number circuit. Itsdata exclusive-ORs the incoming data after initial sync
has been detected but not during following sync
sequences, when the caductr output is high and syncctr isenabled.

Figure 9 - IOBUF8 FPGA Module

Closing Comments
I receive all of the images transmitted (which include only
GOES-11 images with an occasional GOES-12 infrared
image), the Data Collection System data (which is moving
and fixed environmental platform data) and the same text
message over and over. The text message mentions the
LRIT email address and, for emergencies, to telephone
301-817-3880. The EMWIN (Emergency Manager’s
Weather Information Network) is buried in the data but,because it does not come out as normal data files, and I
am only interested in the pictures, I am ignoring it for
now. The images are spectacular, about half as good as
GVAR and twice as good as WEFAX.
So now I ask you which is better, WEFAX or LRIT: or
better yet, why can’t we have both? I know the satellites
are launched for the scientists, not the amateurs, andthat the quality of the data is better. Technically LRIT is
as complex if not more so than GVAR, so why have only
two transmissions that are similar in technology insteadof the system we used to have? WEFAX and GVAR which
are completely different, could be received with simple orcomplex equipment depending on the data you needed.

Figure 10 - Waveform from the Maxim RS422 clock and data outputs

What's next on the Hardware Front?
There are three directions I plan on exploring. The firstwill be to reprogram the FPGA and write the code to
decode GVAR. The second is to experiment with a
CDM-IP300L Comtech receiver I just bought on eBay. The
Comtech receiver is similar to the CM701 with the L-Bandcard installed but has an ethernet interface. That will
eliminate the Xilinix interface board but put more demandon the PC and software. The third direction is to explore
SDR technology using the Xilinx interface board andComblock modules. Comblock modules are Xilinx hardwareand firmware modules that can be chained together toform SDRs. See
www.comblock.com

for more information.
In the next article I will describe the software and thedecoding process.

22

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Figure 11 - GOES 10 IR Full Disc LRIT image

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Peter Wakelin
Oil Leak off South Korea Imaged by Envisat
The 146,000-tonne oil tanker Hebei Spirit,
collided with another vessel to thesouthwest of Seoul, South Korea, on
December 7, releasing an estimated
10,000 tonnes of crude oil into the sea.
Envisat’s Advanced Synthetic Aperture
Radar (ASAR) imaged the polluted area
four days later. Oil on the sea surface
damps down wind-generated waves
making them reflect less of the radar signal
back toward the source. Consequently, oil
slicks appear as darker areas than thesurrounding sea.

significant and powerful technical advances
which include 3-metre high-resolution
imaging, flexibility in selection ofpolarization, left and right-looking options,superior data storage and more precise
measurements of spacecraft position andattitude. The radar operates in C-band(5.405 GHz) and the SAR antenna is
15 m x 1.5 m. More information and further
images can be found at:
http://www.space.gc.ca/asc/eng/
satellites/radarsat2/default.asp

and
http://www.radarsat2.info/

First lunar image from Chang’e-1
Credit: Xinhua News Agency

China Launches another Radar Satellite
China launched Yaogan 3 on November 11
into a sun-synchronous 613 x 623km orbit
and then, on November 20 and 21, small
adjustments trimmed the orbit to 628 km
circular, which is identical to that of
Yaogan 1. Yaogan 2 orbits a few kilometres
higher.

Oil pollution from the wrecked tanker Hebei Spirit
near Seoul, South Korea
Credit: ESA

Canada’s Radarsat 2 Launched
Radarsat 2 lifted off from the Baikonur
Cosmodrome in Kazakhstan on
December 14 aboard a Soyuz-FG/Fregat
combination to a 798 km circular sunsynchronous orbit. The Soyuz upper stage
re-entred the atmosphere within a few
hours and the Fregat was deliberately deorbited after releasing the payload.
Radarsat 2, although smaller and lessmassive than Radarsat 1, which waslaunched in 1995, has been designed with

Vancouver airport at full resolution
imaged by Radarsat-2
Credit: Canadian Space Agency

The city of Vancouver is visible in the upper part ofthis image (reproduced at reduced resolution)acquired on January 6 from Radarsat-2
Credit: Canadian Space Agency

China Launches First Deep-Space Probe
China launched Chang’e 1 into a highly
eccentric Earth orbit on October 24. The
apogee was initially at about 50,600 km
then it was raised to about 120,000 km on
October 29 and 380,000 km on October 31.
It enterd a polar orbit around the moon on
November 5. After further manoueuvres itreached its 200 km operating orbit twodays later. Following on-orbit testing,imaging with its CCD stereo camera began
on November 20. The composite image
reproduced above is made up from multiple
60 km swaths and covers an area
approximately 280 km wide and 460 km
long.

Believed to have a resolution of 5 m in thehighest of the two operating modes, theChinese report that its uses include
estimating crop yields and monitoring
natural disasters. Of course, should they
just happen to leave it switched on when
passing over the Taiwan Strait, it may
detect naval forces too.
More Space Debris Catalogued
In this column, in GEO Quarterly No 13,
March, 2007, it was reported that several
hundred fragments were created when the
Chinese deliberately destroyed their old
weather satellite Feng Yun 1-C in an antisatellite weapon test. US sensors continue
to detect more fragments from this breakup and the number of catalogued pieces
has now reached 2,380, which represents
nearly 20% of all known orbiting objects.
The sensors are believed to be able todetect fragments no smaller than about
10 cm across, so there must be many
thousands of smaller pieces each of which,when travelling at around 7 km/s, has... concluded on page 43

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March 2008

Francis BellI have a number of VHF satellite receivers.
Some I have built myself from kits andothers I have accumulated second-handfrom radio/computer rallies. My recent
project was prompted by the changes offrequency for the downlink APT signal fromNOAA 18.
My understanding is that NOAA andEUMETSAT agreed that NOAA-18 should
transmit on the frequency of 137.9125 MHz
while Metop-A would use 137.10 MHz.
Following the launch of NOAA-18 it
became clear that reception in the UK was
difficult because adjacent frequencies werebeing utilised by high-powered commercial
pager systems. Representations by myself
and others persuaded NOAA to switch
frequency from 137.9125 MHz to
137.1 MHz, a frequency change that lasted
until the launch of Metop-A. At this point,
NOAA-18 was switched back to its original
frequency of 137.9125 MHz, thus leaving
UK receiving stations with the backgroundproblem of interference from pagers.
Subsequent events, and the non-use of
137.1 MHz by Metop-A, appear to havereleased this frequency, which is once
more being used by NOAA 18.
Some of the APT receivers I use contain
EPROMs, which can be changed/replacedto accommodate new frequencies. My
Dartcom receiver and the Ray Godden
designed RX2 which I built from a kit bothfall into this category, and I have upgradedthem with the new EPROMs available fromthe GEO Shop. However, this left me with
two further receivers, of my own andanother belonging to a friend, which havecrystal controlled frequencies.
Understandably my friend wished toreceive NOAA-18, hence a requirement for
new crystals or the purchase of a newreceiver. We decided to go for the new
crystals.
Custom Crystals
I don’t know how many companies arewilling to make custom specified crystals
but the one I identified was QuartsLab
Marketing Ltd [1]. This company used to belocated in Erith, Kent, UK but has recently
moved to Ireland. Their business still
seems to include the supply of crystals
suitable for VHF satellite receivers.

24

If you are planning to upgrade a receiver,be careful to order the correct crystal
casing. The plug-in crystals illustrated
above have substantial one millimetre
diameter pins. The plug-in system is very
easy—just replace an old crystal with a
new one: polarity is not important.
Two of the receivers I modified containedplug-in crystals but, in the case of my RX1,
these were soldered directly to the circuitboard; these crystals have a base with wire
terminals and are directly soldered on to
the board with no socket.
Care must be taken when changing
components directly soldered to a circuitboard. When I changed my circuit board
crystals I used a temperature-controlled
soldering iron and, using a solder sucker toremove the molten solder from its pins, I
was able to lift the crystal from the board.
Provided no other adjustments are made to
the circuits the new crystal will give thedesired frequency.
The RX1 receiver can have additional
crystals added to the existing circuit board
but this requires a small circuitmodification.
If anybody wants to do this pleasecontact me and I will send you the
new circuit diagram.
Determining Receiver Frequency
The crystal controlled receivers I have dealt
with have all used the same system fordetermining the final receiver frequency. A
crystal can be made to have a desired
fundamental frequency but it will also
generate harmonics of that fundamental.
In the case of my receivers, the third
harmonic was exploited, to which the IF
value of 10.7 MHz must be added. The
crystal value for the 137.1 MHz frequency
is calculated as(137.1 – 10.7) / 3 = 42.13333

Similarly, for a frequency of 137.9125 MHz,the crystal value is calculated from(137.9125 - 10.7 ) /3 = 42.40416

A supplier will need to know these two
figures if you order new or replacement
crystals.

www.geo-web.org.uk• For 137.1 MHz order a crystal with a valueof 42.13333 MHz• For 137.9125 MHz order a crystal with avalue of 42.40416 MHz

The cost of such crystals is about £8.00
each, but the company has a minimum
order charge of £15.00. The logic here
seems quite clear: order two crystals, one
for each of the two new frequencies.
Reference
1 QuartSLab, Connogue House, River Lane,
Shankill,
Co. Dublin, IRELAND
Telephone (from the UK): 0845 004 7603
or 0207 100 6357
email: quartslab@connogue.com
Website: www.quartslab.com

Why use the 3rd
Harmonic?
Ray Godden
Crystals oscillators rely on the acoustic
resonance of a piece of quartz
sandwiched between two electrodes. The
resonant frequency bears an inverse
relationship to the thickness of the quartz:
the higher the frequency, the thinner thequartz. As frequency increases it
becomes increasingly difficult tomanufacture resonators at reasonable
cost with adequate performance. The limit
is at about 30 MHz and the crystals areused at their parallel resonant frequency.
The range is extended by using crystals
at harmonics of their fundamental
resonance (3rd, 5th harmonics etc.), theso-called overtone operation. Note that
only odd overtones are possible and theirfrequencies are near, but not exactly
multiples of, the fundamental frequency.
Higher overtones make oscillator circuitry
more critical, particularly if a number ofcrystals are to be switched, and crystals
for high overtone use are more expensive.
Therefore, above about 100 MHz, it’seasier to use a multiplier to derive therequired frequency.

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David Taylor - davidtaylor@writeme.com
Ever since EUMETSAT started transmitting MSG-1 SEVIRI
data via the Hot Bird-6 EUMETCast link in April 2003, theTechnisat SkyStar-2 DVB-S satellite receiver card (andsubsequently USB box) have been the favoured means ofreceiving the data. As the primary units recommended by
EUMETSAT [1], these receivers have gained universal
acceptance. Since those days, more and more data has been
added to the EUMETCast stream. The SkyStar-2 card copes
comfortably with current maximum data rates for thoseenthusiasts who wish to download the full spectrum of MSG,NOAA and Metop data. The USB box, on the other hand, only
operates at USB 1.1 data rates and requires users to be more
selective as to which data they acquire. Moreover, it has been
discontinued and unavailable for a year.
Owing to the compromise, the USB 1.1 box placed on full
EUMETCast data reception, Arne van Belle and later David
Simmons began researching alternative USB units, and spent
many months testing the both SkyStar Plus andTechnoTrend DVB-S USB boxes. Owing to several operational
problems, including driver software, both units proved very
difficult to use. EUMETSAT engineers had also come up against
these problems. At the start of last year, Microsoft released thelatest version of Windows—Windows Vista—which imposes
additional requirements on hardware and software. Some early
adopters of Vista and the beta hardware drivers found that they
suffered more data loss than with Windows XP.

The Dexatek Software
The installation file, along with instructions, can be found on
the included CD. It is well worth checking the Dexatek website
for updates: if the CD does not provide the latest version, you
should be able to obtain it as a 13 MB download fromhttp://www.dexatek.com/Download.asp

This file comes in the compressed ‘RAR’ format and you will
require the freeware utility UnRAR.exe to unpack it. Download
your copy of UnRAR fromhttp://www.rarlab.com/rar/unrarw32.exe

then double-click to extract andinstall the UnRAR.exe commandline utility. The easiest way toproceed is to place the Dexatek
driver software and UnRAR.exe inan empty folder along with a smallcommand file ‘go.cmd’. This contains
the single instruction ‘unrar x *.rar’(you can create this using any text
processor such as Notepad; thensave it as ‘go.cmd’). When you
double-click on go.cmd, all thedriver and application software forWindows Vista are unpacked
Figure 2 -The Dexatek box + PSU
into a folder named
V2.0build02_20071102Dexatek.

Fortunately, David Simmons has recently come across a newer
USB 2.0 hi-speed box - the Dexatek DK-5702 I-TEK Sphere which he has found to be quick and easy to set up, and able toreceive the both MSG and Metop EUMETCast data without
problems. He demonstrated this on a laptop at the GEOManagement Team meeting in November 2007 and the results
were very encouraging. The excellent, loss-free performance heobtained has now been replicated by others using various PCs,
running both Windows XP and both the 32-bit and 64-bit
variants of Windows Vista.

At the time of writing, the latest drivers and application
download file for Windows Vista was ‘DK5702 - 20071107
update Vista Driver and updated application pack’, containing a
number of files and subfolders, including the all-important
setup.exe. Double-click on setup.exe to start the install process.

The Dexatek I-TEK Sphere USB-S Receiver
The I-TEK Sphere comes with a universal PSU, remote control,
USB cable and a CD which contains the installation softwareand manual. All you have to do is attach the lead from yourdish antenna to the box, which connects to a USB port on yourPC. Connect the PSU to the I-TEK Sphere,
power it up, and you are ready to install thesoftware. At this point you will almost
certainly be presented with a‘Found New Hardware’
warning dialogue. Ignore thisand press the ‘Cancel’ button.

and in the ‘DVBWorld Software and Drivers’ section, download
the ‘DVBWorld Software’ (big remote control). The download,
DVBWorld-V2.0.rar, can be unpacked as described above. The
setup.exe file can be found in the ‘DVB World’ subfolder. Thesefiles also work with the 64-bit version of Vista.

From the outset, it is vital that younote to which USB port you connected
Figure 1
the receiver (your PC will surely have
The Dexatek
several). If, for any reason, you disconnect
I-TEK Spherethe unit from the PC, you must reconnect it to
the same USB port. If you don’t, Windows will assume that you
are connecting a second unit and therefore fail to associate itwith the already installed software!

Note: It is not unknown for the Dexatek drivers site to go off-line.
In this case, you can also use the DVBWorld drivers with the
Dexatek hardware. Go to the DVBWorld download page at
http://www.worlddvb.com/html/softdown.htm

Note: The Dexatek and DVBWorld boxes contain almost
identical hardware and the same software works with both. The
screen-shots that follow are applicable to either, even though
there are minor differences.
Driver Installation
Windows Vista may prompt you to authorise the program before
continuing—unless, of course, you have disabled the User
Authorisation Control (UAC). Select ‘Allow’ then proceed towork through the installation wizard.
In the ‘Setup Type’ screen (figure 3), make sure that both
‘Drivers’ and ‘Software’ are checked. At two points during the
installation you will be presented with a warning that thedrivers are unsigned: just click on the ‘Install this driver

www.geo-web.org.uk

25

GEO Quarterly No 17Group for Earth Observation

March 2008

Figure 3

Figure 6

Figure 4

Figure 5
Figure 7

software anyway’ box. At another point you will have to chose afolder for the installation (figure 4).
You will be prompted to install older versions of Windows Media
Player and Direct-X. Check both options (figure 5) and click‘Next’. If your PC already has up-to-date versions of these
installed, this step will simply be skipped. When the ‘Wizard
Complete’ screen appears, click ‘Finish’ and reboot yourcomputer.
The manual notes:‘If you are using a USB2.0 adapter PCI card/PCMCIA etc.
to support the USB2.0, please turn off the USB Box power
before you restart the computer. Please restart yourcomputer directly if USB2.0 supported by motherboard.’
If required, power-up the USB box after the computer has
rebooted. You may see messages about finding new hardware,
installing drivers and the device being ready for use.
Setting up the Dexatek Software
There are two stages to this process, firstly setting up the
I-TEK Sphere for TV operation, followed by a second stage when
you have to set it up for data reception.

26

TV Setup
You must select thesatellite andtransponder you wish toconnect with, andconfigure the data
connection for
EUMETCast use.
Double-click the
Dexatek icon on yourDesktop to reveal thescreen illustrated infigure 6 and click the
Figure 8
spanner-shaped
configuration icon on the bottom row. Use the drop down lists toselect the satellite as ‘HotBird 1/2/3/4/5/6/7A’, and thetransponder as ‘TP8_10853_H_27500’ (figure 7). If you have amore complex LNB setup, you may also need to configure the‘DiSEqC’ parameters at lower left but for most simple setups,‘Universal LNB’ should be all that is required. There is no needto scan the whole satellite (Scan Sat); just click the ‘Scan TP’
button to scan the selected transponder for the active TV andradio channels. After scanning a transponder you are presented
with a choice as to what to make available. Select ‘All’ and ‘FTA’
as illustrated in figure 8 then click ‘OK’.

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March 2008

Group for Earth Observation

The website [2] also
carries a highly
comprehensive guideto the latest
information on
testing the Dexatek
box and is regularly
updated as new
results become
available.

Figure 9

You should now be able to select andview TV channels via your I-TEK SphereUSB receiver.
Data Setup
Click on the spanner-shaped icon once
more but this time select the ‘IP Config’
tab to display figure 9, where your firsttask is to select the 10853 (MHz)transponder from the left-hand browser
in the ‘Transponder information’ panel;then click on the transfer button (rightpointing double arrow) to transfer thisinformation to the right-hand list
(circled).
Next, click on the TP1 transponder inthis list and, in the PID information box,
click the ‘Scan PID’ button. You may
have to add the PID manually in order toenable the ‘ Scan PID’ button. Do this byclicking the ‘Add’ button, then click on‘Decimalization’ (sic) and enter ‘100’ inthe top PID Data box (figure 10). Click‘OK’ to confirm.
You can now click ‘Scan PID’, which ismuch more efficient than entering all the
PIDs you need, individually, by hand.
Any PIDs that you don't want can beselected with a mouse-click and removed
by pressing the keyboard ‘Delete’ key.
You can access a list of all the relevant
EUMETCast PIDs on my website at
http://www.satsignal.eu/wxsat/atovs/

Figure 10

Do please be aware
that, if the datafrom a particular
PID is not actually
flowing while you
click ‘Scan PID’, thePID for that data
may not be recorded
automatically. Be
sure to check the
PID list carefully—ifyou miss a PID
associated with data
you are allowed toreceive, you may get
an intermittent red ‘T’ icon. Check thelist of PIDs carefully to avoid this (e.g.
PID 302 for DWDSAT data). When all isdone, click ‘OK’ to close the configuration
dialogue. Your data should. now startflowing when you click the ‘IP’ button.
Recent Developments
Recently, Ian Deans invested in a new‘Vista’ computer and transferred his
SkyStar-2 card to it with the intention ofusing the higher PC specification to
streamline his EUMETCast reception.
Unexpectedly, Ian suffered severe
problems. Although the SkyStar card andsoftware certainly appeared to installcorrectly, he was beset by large numbersof missing segments, an issue he wasunable to cure. So bad was the problem,that Ian had to restore the card to his old
PC to resume his EUMETCast activities.
I suggested that the Dexatek I-TEK
Sphere USB receiver might be worth
trying and took round a spare unit for
him to try out. After following the
installation instructions, I found that theunit worked well, with one exception;although there was no data loss, he kept
getting a red ‘T’-icon. It didn’t take longto source this problem: the PID for
DWDSAT was missing, and as soon as it
was included the red ‘T’-icon went away.
It is not yet understood just why Dexatek
USB box works so well with Ian’s PC
when it had suffered problems with the
SkyStar-2 PCI board. Other GEO readers
have transferred to Vista without
problems. Perhaps it is a question of thespecific hardware in Ian’s PC, or maybe asoftware or driver problem. Perhaps
Vista is better optimised for USB
operation; maybe the SkyStar-2 drivers
don't work as well under Vista; it could
simply be that the Dexatek drivers are
better than the TechniSat ones? I would
love to get to the bottom of thiswww.geo-web.org.uk

GEO Quarterly No 17

unexpected result! If you have any ideas,
do get in touch and let me know.
Testing and the Future
At the present time, the Dexatek I-TEK
Sphere USB receiver is giving highly
promising results for a number ofdedicated EUMETCast enthusiasts.
There is little doubt that the volume ofdata available to amateurs via
EUMETCast will continue to increase,and that a faster receiver, such as the
Dexatek or DVBWorld boxes, will be
required to cope with all the data.
Neither GEO nor EUMETSAT is yet in aposition to state definitively that the
Dexatek USB box is the way forward, but
it is highly promising and no adverse
issues with the unit have yet been
identified.
The Dexatek I-TEK Sphere USB receiver
is not currently available in the UK but
can be purchased from vendors in the
EU. Cost is generally in the range 65 - 70
euros.
GEO are investigating the logistics ofmaking this, or a similar, unit available
from the GEO Shop. By the time youread this it may be worthwhile visiting
the Shop web page at
http://www.geo-web/shop.html

to see if there have been any
developments. Meanwhile, any reader
keen to experiment with the Dexatek box
should be able to order one from thecontinent by searching the web for‘Dexatek I-TEK 5702’.
Note for Windows XP Users
If you have not upgraded to Vista, don’t
despair. The Dexatek USB box and its
software also operate successfully underWindows XP.
Acknowledgements
I wish to acknowledge the work andeffort of many others. Arne van Belle has
been looking at different USB boxes eversince the need for the higher bandwidth
to handle Metop data became apparent,
and tried many combinations ofhardware, operating system, and drivers
with various degrees of success. David
Simmons has contributed his technicalexpertise, John Tellick his knowledge ofthe satellite TV field and Klaus-Peter
Renner (EUMETSAT) his in-depth
knowledge of EUMETCast to an informal
working group which has correspondedby e-mail over the last year or so.
References
1 EUMETSAT Technical Document No 15
http://www.eumetsat.int/groups/ops/
documents/document/pdf_td15_eumetcast.
pdf
2 David Taylor’s Website
http://www.satsignal.eu/==> Eumetcast and Vista (under ‘Weather
Satellites’)27

GEO Quarterly No 17Group for Earth Observation

March 2008

John Tellick
Well, what a year? I started writing anarticle about winter and our record-breaking
spring in the UK and parts of northern
Europe. But thinking the summer mightalso be noteworthy, the article was left
pending and I now find myself at the
keyboard, between Christmas and New
Year finalising it. I’m sure I’m not alone inasking: ‘Where did 2007 go?’Winter
It was another mild winter in southeast
England, but fortunately the succession of
dry winters leading to last years 11 monthhose-pipe ban was broken. Good rainfall
over the period allowed reservoirs to
replenish and underground resources tobegin to build up again.
Winter was late arriving in Scandinavia andthe Alps with many resorts having to rely
heavily on snow cannon to produce
artificial snow until good falls of the ‘real
thing’ arrived in January and February. This
lack of real snow, coupled with warm
temperatures and sometimes windy
conditions, forced the curtailment orcancellation of several winter sports
championship events. In figure 3, highpressure over central Europe gives a clear
mid-April view of the Alps.
SpringNorthern Europe experienced prolonged
large areas of high pressure throughout
March and April. This situation produced
extended spells of record-breaking, aboveaverage temperatures and sunshine insoutheast England and other European
countries during both months, coupled withunusually little monthly rainfall.

dense ice showing as milky swirls while
figure 5, dating from April 28, depicts a notvery icy Iceland. By way of contrast,
though, figure 6 illustrates a very icy
Svalbard on May 1, with lots of sea ice to
the N and E. Svalbard is, of course, thelocation of the EUMETSAT Metop groundstation.
Summer
The record-breaking spring was, alas, a false
promise. Having spent many days on thebeach during March and April, what followed isbest forgotten. Summer was, nevertheless,memorable, but for all the wrong reasons! Mayexperienced well above average rainfall overmost of the UK, lower than average sunshine
and disappointing temperatures. A mere 7.9°C
was recorded at London’s Heathrow Airport on
May 28! And things just got worse. The below
average sunshine continued through June with
rainfall well above average. Parts of NE
England experienced severe flooding and inYorkshire, rainfall was 300% up on normal.

Temperatures continued below averagewith sunshine well below average throughJuly and rainfall was again well above
average in most areas: England and Wales
recorded more than double the norm while
Worcestershire suffered four times its
average precipitation, leading to severe
flooding throughout Worcestershire,
Gloucestershire and the Sheffield area.
August also proved disappointing, thecoldest in most of Britain for at least ten
years. Unsettled weather lasted till the endof the month when high pressure finallybegan to build.

Figure 1, dating from March 27, shows oneof these high pressure areas, with earlymorning fog in central England stretching
into Wales. Sea fog and low cloud—called
haar—shrouds the coastlines of northeast
England and eastern Scotland while heavy
winter snowfall continues to highlight themountains of Norway.

Throughout June, July and August the jetstream looped much further south thannormal, allowing Atlantic depressions tocross the UK when they would normally
have passed to the north, between
Scotland and Greenland. Several times
during these months, as many as three
active low pressure systems would crossthe UK within a week, bringing cool, wet
and windy weather. The image on theinside back cover shows a typicalsuccessive scenario.

Figure 2 is part of a NOAA-18 AVHRR
transmission on May 2 which shows thephenomenon particularly well. The highpressure conditions led to the formation of
an impressive region of haar over the North
Sea, which persisted for several daysaround the end of April and blanketedmuch of the east coast of Britain. Figure 4
shows sea ice breaking up off the east
coast of Greenland on April 19, with lessSeptember started promisingly, with the jetstream back where it should be; the Atlanticlows were passing north of the UK as avery large area of high pressure close bystarted influencing the weather. However, it
was 'in the wrong place': just too far to thewest, and allowed a northerly airflow tostream across the UK, bringing cloudy yetsettled conditions and mid range
temperatures for a long period.

28

www.geo-web.org.uk

The high pressure stubbornly remained
stationary off Ireland for nearly four weeks.
Finally, on September 23/4, a depression
passed over Scotland bringing an active cold
front across the UK, with mini tornados
reported in parts of southern and central
England.
Whilst much of northern Europe suffered a
cool, miserable summer, southern Europe
experienced weeks of cloudless sunshine andrecord breaking high temperatures. Wild fires
broke out in several countries with Greece
experiencing the worst fires ever. These werefanned by days of blustery NE winds which
devastated vast areas of forest, countrysideand homes and caused loss of life. The
neighbouring countries of Bulgaria, Albania,
parts of the former Jugoslavia and southern
Italy were also affected. These fires could beclearly seen in both NOAA and Meteosat
imagery (lower image on inside back cover).

AutumnAs if to make up for the poor summer, autumn
throughout much of the UK was wonderful. SE
England enjoyed fine settled weather from mid
October into November as periods of highpressure brought calm sunny conditions. The
cool wet summer had provided a considerable
spurt of growth to trees and bushes and theautumn colour was just breathtaking; in thecalm conditions the leaves remained andseemed to last for a month.
However, 'the weather' had one more sting to
its tail: on November 9, a combination of very
low pressure, a very high tide and strong
winds in the North Sea brought a fear of
severe flooding from an enormous tidal surge
along the North Sea coasts of England and
The Netherlands. It had been predicted forseveral days but passed off with only minor
flooding, since sea defences all alongvulnerable coasts had been strengthened andupgraded after the catastrophic flooding andloss of 307 lives in the UK during a similar
surge in 1953. Predictions are for this type of
event, with climate change and rising sea
levels, to become far more frequent!
December had many days of fine, cold sunny
weather, though with a chilling north toeasterly wind at times. And, the winter sports
season in Europe got off to a brilliant start with‘early’ heavy snowfalls in parts of the Alps
during early November—a once in 30 year
occurrence. Scandinavia also enjoyed goodfalls of snow in November, with cold, clear
sunny conditions for all the opening Nordic
events, including cross country skiing, biathlon
and ski jumping.
It was reported on BBC News in early January
that, despite the cool, wet dismal summer, withthe heaviest rains in living memory and arecord-breaking warm spring, 2007 was apretty average year for the UK in terms ofoverall rainfall, sunshine and temperature.
Now what will 2008 bring?

March 2008

Group for Earth Observation

GEO Quarterly No 17

Figure 1 - High pressure over Europe - NOAA-17 on March 27, 2007

Figure 2 - Haar fills the North Sea - NOAA-18 on May 2, 2007

Image © EUMETSAT 2007

Image © EUMETSAT 2007

Figure 3 - Cloud-free Alps - NOAA-17 on April 17, 2007

Figure 4 - Ice breaking off the Greenland Coast - NOAA-18 on April 19, 2007

Image © EUMETSAT 2007

Image © EUMETSAT 2007

Figure 5 - Iceland without the ‘ice’ - NOAA-18 on April 28, 2007

Figure 6 - Svalbard - NOAA-17 on May 1, 2007

Image © EUMETSAT 2007

Image © EUMETSAT 2007www.geo-web.org.uk

29

GEO Quarterly No 17Group for Earth Observation

GEO reader Keith Fraser, who lives in Amherst, just outside
Buffalo, New York, spotted an unusual cloud formation
streaming down the Gulf of St Lawrence, on one of his NOAA-17
APT images. Keith, now retired, formerly worked as a pilot, andimmediately recognised the pattern as being identical to thesmoke streamlines observed in a wind tunnel Venturi as it flows
over an airplane wing.
The airflow over the top curve of the wing is faster than thatflowing beneath the wing, thereby causing a lower pressure on
top; it is the higher pressure from below the wing that provides
the lift that keeps the ‘plane aloft.

30

March 2008

Daniel Bernoulli (1700-1782) was working with liquids rather
than air when he discovered this eponymous effect but it isequally applicable when the fluid is a gas.
In the satellite image above, cloud streamers sweeping past
Anticosti Island, one closely following the full length of theGaspe Peninsula then stretching far out to sea, are clearly an
aerodynamic effect.
The image above is a channel-2 NOAA-17 obtained at 14:45 UT
on December 12, 2007.

www.geo-web.org.uk

Image: NOAA CLASS Archive - http://www.class.noaa.gov

March 2008

Group for Earth Observation

GEO Quarterly No 17

J P Silver - e-mail: john@rfic.co.uk
Having a general interest in the weather, I have always beenfascinated by storms, and particularly the lightning associatedwith them. There are professional lightning detectors, the mostwell known being the Boltek system, which provides a radar-like
display of the surrounding location and the position of lightning
strikes. However, this system can cost around £300 and I
wondered if there was a ‘simple’ DIY solution? A quick searchon the Internet led me to Daniel Verschueren’s Lightning Radar
Project site at
http://users.edpnet.be/DanielV37/Detecteur3/

featuring a Lightning Radar (LR) based on a design and concept
by Frank Kooiman
http://members.home.nl/fkooiman/lightning/

I have to say that these guys have developed the hardware andsoftware for this project and I owe them much thanks forhelping me to set up my own LR station. The purpose of thisarticle is to describe the principal behind LR, the hardware
required (including a surface mount design I have developed)
and the setting up and use of the software.
The Concept
The LR system antenna consists of two loops with a resonant
frequency of approximately 10 kHz; these are mounted 90°
apart so that one can point north/south and the other east/west.
Lightning strikes produce a distinct 'signature' that can berecognised by a software algorithm which eliminate spurious
sources like car ignitions and central heating switches. The low
frequency RF lightning signal arrives at the antenna and,depending on the direction, will generated a voltage in eachloop.
Each antenna loop is connected to a simple circuit containing an
op-amp, with the gain set close to 100, which is in turnconnected to the line input of a PC soundcard. The speciallywritten software can sample the signal arriving at thesoundcard, decide whether it is a lighting strike, and if so, thedirection from which it arrived. Also, depending on the signal
amplitude, it can calculate how distant the strike was.
Unfortunately, using just two antennas gives rise to a 180°
phase ambiguity in the received lightning signal. To overcome
this problem, Frank's software is able to link up with anotherstation (via the Internet) and, using a clock synchronisation
routine, employing triangulation to pinpoint the direction of thelightning strike. This triangulation method has an accuracy of
one degree. Figure 2 shows how two 'linked' stations can use
triangulation to pinpoint the location of a lightning strike. It
will only work if the two PC's have their clocks synchronised sothat they detect the strike at the same time.

antenna on his website when
you click the ‘Hardware’ button.
I have built this antenna
myself, specifically for an
outdoor location. The antenna is
made from four lengths of
15 mm copper tube bent into
semicircles and mounted at eachend in PTFE blocks. Connecting wire is then fed through the
openings in the top and bottom blocks into the copper pipes toform each of the two loops. A diagram showing one of the twinloops is shown in figure 6. Note that the ends of each winding
are twisted together (twisted pair) but, if fairly short, less than
15 cm, then the wires can be left free.
The diameter of the loop is 900 mm and each semicircularelement is 1382 mm in length. A 1 µF capacitor connectedacross the winding of each loop should resonate the antenna to
the correct frequency (around 10 - 11 kHz).
The PTFE blocks are fitted in the 32 mm wide gaps. Details on
manufacturing the PTFE blocks and more information on thisantenna can be found on Daniel’s ‘Hardware’ page.
Hardware Electronics
The electronics for the LR are very simple and consist of two
identical low noise op-amp circuits each with a gain of 100. The
op-amps require a dual voltage supply of ±15 V from a PSU
sited indoors and fed to the op-amp circuit at the antenna.
The PSU Design
If the whole system is to be sited indoors, in a loft for example,
then the circuitry could be easily built on Veroboard using
leaded components. The surface mount (SM) design described
below is based on Daniel's circuit. To simplify the build of thesystem, I designed a surface mount version of Daniel's LR
design (figure 12 and 13). The top view, with component
identities, is shown in figure 18. Figure 14 shows the system
connections to the PC via a stereo 3.5 mm plug. Connection
between the PC/PSU and the antenna-mounted LR PCB was
made via four individually screened audio leads.

My system has been up and running for a few months now andwhen it is properly set up can give very accurate results. The
latest software additions allow connection to the Blitzortung
network [1]. Figures 3 and 4 show a comparison between my LR
and the corresponding Blitzortung map. As you can see there isa very good correlation between the lightning strike maps whichshow a storm over Belgium.

Note that the SM circuit
is built on double-sided
standard FR4 PCB board
with the underside
ground-plane remaining
intact to allow earth
connections. The earth
connections of thecomponent side arecompleted by drilling a
0.8 mm hole through theboard and linking the twolayers with a piece ofcopper tape or wire. The
Figure 1 - The completed SM LR PCB
PCB layout is shown in
Figure 16 and the completed PCB assembly in figure 1.

The Copper-Pipe Loop Antenna
For a more robust and waterproof design, Daniel designed thecopper-pipe loop antenna and figure 5 shows my more sturdy
version. You can find all the constructional details for this

Most of the parts are easily sourced through component
suppliers like Maplin and Farnell. Table-1 (page 36) lists theparts for the amplifier-regulator section. The values of R4 andR9 are set to 100k which gives each amplifier a gain of 100,

www.geo-web.org.uk

31

GEO Quarterly No 17Group for Earth Observation

Figure 2 - Lightning Location by Triangulation

Figure 3 - The author’s Lightning Map

Figure 5 - The Copper-Pipe Loop Antenna

Figure 6 - Schematic: Copper-Pipe Loop Antenna

March 2008

Figure 4 - The Blitzortung Lightning Map

Figure 8 - A strike detected

Figure 7 - The initial radar screen shown when first running LR

32

www.geo-web.org.uk

Figure 9 - The prototype PSU

March 2008

Group for Earth Observation

which seems to be a pretty optimum value. No alignment isrequired with this design. However, it is very important that
the PCB is thoroughly sprayed with a conformal coat of lacquer
to ensure it is absolutely waterproof. I am hopeful that a
populated and tested LR Antenna amplifier PCB assembly will
be available from the GEO Shop.
The PSU Circuit
The PSU provides an unregulated ± 20V to the LR circuit board
sited at the antenna. The circuit diagram is shown in figure 15
and the parts lists in table-2 (page 36). The transformer has two
12-0V windings that are wired to give ± 20 V a.c. The rectifiercomponents are mounted on a small PCB. My prototype, whichused a simple Veroboard layout, is shown in figure 9 (a PCB has
been designed for future builds). The voltage outputs areconnected to a 9-way Cannon plug (top left) and this connector
is used to receive the right and left channels from the antenna
PCB. In addition, a 3.5 mm stereo socket connected to the
Cannon socket is located at upper right so that the strike pulses
from the LR circuit can be fed into the PC soundcard. The audio
cable to the PC is connected to this socket. The IEC mains
connector, with fuse, is at the bottom right. As a precaution, two
additional fuses have been added to the +20 V and –20 V
outputs in case of cable shorts.

GEO Quarterly No 17

strike on a map. The audio output cable connects to thesoundcard 'Line' input (usually denoted by a green connector).
Ensure that the line is activated and set it to maximum using
Windows sound recording options. Also, if you have a firewall
running (software and/or router), you must make sure thatport 4711 is free. This will enable the LR software tocommunicate with another station; otherwise, there will be no
triangulation process and the plotted strike direction will bemeaningless.
Once you have constructed the hardware, it is time to installand set up the Lightning Radar software, which can be
downloaded from.
http://members.home.nl/fkooiman/lightning/index.htm#5

Click menu item No 6 at the top of this page ( 'Software
Downloads'), which takes you to the 'Download Lightning
Radar Software' section near the foot of the page. Click the linkto download the current full version, V.6.7.25Setup.zip andinstall it. The program is constantly being updated and you
may also also download and install the latest update patch,currently V 7,12,5.zip, which should be saved into the existing
application folder. Note that these version numbers may wellhave been updated by the time you read this.

It's a good idea to fit fuses all round, especially as our new dog
decided to chew through the LR cable causing one of therectified voltages to short—and resulting in a very hot PSU
unit.

If you experience difficulties obtaining the software, feel free toemail me and (john@jps.myzen.co.uk) and I can forward
copies to you

There is no requirement to use the PSU design given here.
Some LR operators have simply used two mains unregulated
power supplies. Such a power supply suitable for thisapplication is Maplin’s 24 V, 500 mA unit (order code N88AT).

This section assumes that you have the latest version of thesoftware installed. The screenshots below refer toversion 7.12.5. When first running LR it will open with adefault radar screen (figure 7). Set the centre value to –20 andthe outer value to –120.

There will still be a need for a small box, the purpose being toprovide a socket for the LR data/PSU cable, sockets to connect
the two PSUs and a 3.5 mm jack socket to permit an audio
connection to the PC.The wiring inside this box connects the
PSU and jack sockets to the LR data/PSU cable socket (theaforementioned 9-way Cannon socket).
The PSU PCB
As described above, the original PSU section was built on
Veroboard. My latest design uses a single-sided PCB measuring
85 x 75 mm; the component side is shown in figure 16 and thefoil side in figure 17. (The 4 fixing hole positions are
65 x 65 mm). The PCB is mounted in a
die-cast box with the mains fed
through a fused IEC connector. The
a.c. mains is wired to theprimary of the transformer.
You must ensure that any
exposed connections are
insulated with heat-shrink
sleeving. Make sure that thesecondary transformer connections
are made correctly, so that therectified voltage outputs of the PCB are
Figure 10
approximately +20V and –20V. The
The completed PSU PCB
completed PCB assembly is shown in
Figure 10.
The circuit diagram (figure 15) shows the suggested Cannon pin
connection numbers to be used. Two pins on the connector
supply the audio from the LR amplifiers and connect to thestereo 3.5mm audio connector. You also require a lead to link
the PC to the LR amplifier. I used 4-core screened cable (Farnell
389-4745) although you could in fact use twin screened audio
cable as the current taken by the LR is very small.
The ‘Lightning Radar’ Software
The software written by Frank determines whether a strike has
occurred and uses triangulation with another station to plot theInitial Startup

An instruction manual on how to generate your own radar map
can be found at
http://users.edpnet.be/danielv37/Detecteur3/Forum

Download the file ‘Step 6 - How to build a map.pdf’’.
Setup Gain
You need to ensure that a signal is being received by thesoundcard and that the level is set correctly in LR. To start
with, connect the LR audio lead to the 'Line' input of thesoundcard, not the 'MIC' input and use Windows sndvol32.exe
utility to ensure that the recording level of the 'Line' input is
set to maximum.
Next, select the LR
gain window andinsert the details
shown in figure 11(these values are agood starting point).
If lightning strikes
are being received
you should be seeing
the sort of patterns
Figure 11 - The LR gain settings dialogue
shown in figure 8; if
not, and you get aflat line all the time or nothing at all, then either the lightningradar is faulty, there is a broken wire, or there is a problem
with the soundcard setup.
Note: A small utility called Sound Input should be running,
showing a blue bar for 'bu' at about 10% and green bars for 'vl'and 'vr' at about 1%.
General Settings
Figures 22 to 23 show screen dialogues from the LR program
which illustrate good starting settings.

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33

GEO Quarterly No 17Group for Earth Observation

March 2008

Figure 12

Figure 13

Figure 14 - The wiring of the LR and PSU modules to the PC and antenna.

Figure 15 - The PSU section circuit diagram. The components are mounted on a small PCB in a diecast box.
The 100 mA Fuse (F1) is part of the IEC mains input plug, SK1.

34

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March 2008

Group for Earth Observation

Figure 16 (Actual size)
The PCB foil track side of the LR SM PCB (thereverse of the PCB is continuous copper groundplane). There are 17 via thru holes, which are
made by drilling a 0.8 mm diameter hole andlinking the top track to the rear ground-plane
using thin strips of copper tape (or tinned copperwire). PCB size is 58mm by 58mm.

Figure 17
The component positions for the PSU PCB section (actual size).
Note the line on C5 and C6 signifies the positive end of the capacitor.

Figure 18
The PCB component schematic (actual size)

Internet Settings
This dialogue (figure 24) allows data to
be uploaded from the user’s own FTP site
to Daniel 's website. First, enter yourFTP site address in the ‘FTP to’ field,
then edit the file 'Publish.cmd', found in
the LR folder.Initially, it looks like this:<username><password>
send “picture5.png”
send “picture4.png”
send “picture1.png”
byeEnter your FTP username between theangle-brackets in the topmost field andthe corresponding password between thesecond set of angle-brackets.

GEO Quarterly No 17

Figure 19
The PCB foil pattern (actual size) of the PSU section. This iswhat you need to see on the copper clad side of the PCB.

Next, add the instruction‘cd Lightning_radar/’, the address of thefolder on your FTP site to which you
intend to upload the pictures. This mustbe followed by the instruction ‘binary’ toestablish the mode of transmission.
Finally, just prior to the ‘bye’ command,
add a line such as
send “C:\Program files\
LightningRadar\Data\picture8.png”<ftp.username.isp.co.uk><mypassword>
cd Lightning_radar/binarysend “picture5.png”
send “picture4.png”
send “picture1.png”
send "C:\Program Files\
LightningRadar\Data\picture8.png"byewww.geo-web.org.uk

Your edited 'Publish.cmd' file should now
look something like the above. This script
will upload your plots on to Daniel's
website.
Forum
Although the software does not possess afull help file, there is a forum to assist
would-be LR builders at
http://foudre.chasseurs-orages.com/
viewforum.php?f=45

Conclusions
This article describes the construction ofa simple lightning radar capable ofresults similar to commercial systems
like Boltek. Although SM components canbe somewhat fiddly to use, they do result

35

GEO Quarterly No 17

Figure 20 - Enter the coordinatesof your Station Location

Group for Earth Observation

Figure 21 - Selecting a high-pass filter, whichhelps to eliminate spurious sources

Component

Figure 23 - Display Options
The Minimum amplitude matches that entered on
the radar diagram; Duration visible is the number ofminutes to show the strike before erasing it; Focus
window uses software to pinpoint clumps of strikes;
Angular separation is a parameter that can bevaried to remove spurious strikes.

March 2008

Quantity Part typeFigure 22 - Calibration Settings

Part Package

R1, 2, 5, 6, 7, 10

6

1k Resistor

0805 SMT

R3, 8

2

10k Resistor

0805 SMT

R4, R92100k Resistor

0805 SMT

R12, 152

1k1 Resistor

0805 SMT

R13, 162

100R Resistor

0805 SMT

R11, 142

10R Resistor

0805 SMT

R 0 ohm (figure 11)

1

0 ohm link

1206 SMT/wire link

C 1, 2, 8, 9

4470nF Capacitor

1210 SMT

C 3, 102

150nF Capacitor

1210 SMT

C 5, 122

1nF Capacitor

0805 SMT

C4, 11

2

10nF Capacitor

0805 SMT
0805 SMT

Part Source

C 6, 7, 13, 14, 15, 18, 20, 23

8100nF Capacitor

C 16, 212

C 17, 222

C 19, 242

1000µF, 35V Capacitor SMT Case J16
Farnell 9695982(Range FK Panasonic)
SMT Case D
10µF, 50V Capacitor
Farnell 1244410(Range FK Panasonic)
SMT Case F
330µF, 25V(Range FK Panasonic) Farnell 1244418

D 1, 2, 7, 8, 13, 14, 15, 16

8

Schottky 60V, 1A

SMT Case SMB

Farnell 4213038

D3, 4, 5, 6, 9, 10, 11, 12

8

1N4148SMT

RS

IC1, IC2

2

OP27GSZ

SMT SOIC-8

Farnell 942612

IC3

1

LM317LMSMT SOIC-8

Farnell 9488537

IC4

2

LM337LMSMT SOIC-8

Farnell 9485945

Table 1 Parts list for the antenna amplifier PCB
Figure 24 - Internet Settings

in a very compact design that can behoused within a box at the antenna. In
addition, I found that using an SM
design made it at lot easier to waterproof
the active antenna circuit (by spraying
the completed PCB with ConformalCoat), So far, my unit has survived thevery wet weather experienced during the2007 summer.
The author of the software is continuing
to develop it, removing bugs and adding
extra functionality (most recently, a linkto the Blitzortung storm site [1]. The
latest version now has a drop and dragfeature under the calibration menu. The
user can locate a local storm (either fromthe Blitzortung site or a local Boltek site)and drop and drag the correspondingstorm on to the correct position on theirown LR map.
Reference
1 Blitzortung - http://www.blitzortung.org

36

Component

Part type

Suggested Part Source

T1

12-0, 12-0 Transformer 6VA each winding

Maplin N01CF

F1

100mA, 20mm fitted into IEC chassis socket SK1 Maplin GJ72P

F 1, 2

100mA, 20mm fuses and chassis sockets

Maplin GJ72P & GU73Q

P L1

IEC mains plug and fuse holder

Maplin FT37S

SK1

3.5mm Stereo Jack socket

Maplin FK03D

P L2

9-way D-sub plug + lock posts

Maplin RK60Q & FP31J

SK2

9-way D-sub socket & Hood

Maplin RK61R & KE94C

D1-D4

1N4007

Maplin QL79L

R1, 2

Resistor 6.8 ohms, 5 W

R3, 4Resistor 100k, 0.25 W

Maplin M100K

C1-C4

Capacitor Ceramic 100pF, 100V

Maplin WX56L

C 5, 6

Capacitor Electrolytic 4700uF, 35V

Maplin AT24B

C 7, 8Capacitor Polyester 220nF, 100V

Maplin BX78K

Diecast case, PCB, Nuts, Bolts etc
4-core screened cable
Table 2 - Parts list for the PSU section

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March 2008

Group for Earth Observation

GEO Quarterly No 17

Peter Wakelin
The recent sinking of MS Explorer
following a collision with an iceberg near
King George Island reminded me of myseveral tours of duty to the Falkland
Islands following the conflict with
Argentina in 1982. During my three years
at RAF Mount Pleasant I made several
flights in Hercules C130 aircraft to theSouth Sandwich Islands and South
Georgia. I also made a very memorable
flight down the incredibly beautiful
Antarctic peninsula.
Background
The remote Falkland Islands, east of thesouthern tip of the South American
continent and its even more remote
Dependencies of South Georgia and theSouth Sandwich Islands, made world news
headlines after Argentinian scrap
merchants landed at Leith, South Georgia,
on March 18, 1982 and raised theArgentinian flag. On the 20th, HMS
Endurance left Stanley, Falkland Islands,
for South Georgia, carrying Royal Marines
who observed other Argentinian shipping
off the coast of South Georgia. At 0430
hours local time on April 2, ArgentinianForces started landing near Stanley, thecapital and only community of any size inthe islands, with a population of about
1,100 persons.

The Antarctic Peninsula near Brabant Island

During April, the Task Force, ordered by
British Prime Minister Margaret Thatcher,
was prepared and despatched southwards
and on May 1st the effort to retake theIslands began when Vulcan bombers from
Ascension Island (8°S, 15°W) bombed
Stanley airfield. During six weeks ofintensive military activity numerous ships
were destroyed and over 1,000 persons died
before the surrender on June 14.
Local meteorological services for the
support of British military activities during
the conflict, and for nearly four years
afterwards, were provided by the Met
Office’s Mobile Meteorological Unit (MMU),
staffed by volunteers on Special
Commissions and in uniform. In April 1986
the MMU team was replaced by civilian
volunteer staff on five-month tours of duty.
I was amongst the first group of forecasters
to go and enjoyed it so much I went down
seven times in four years. By 1986 a new
airfield was nearing completion some
70 km from Stanley which enabled RAF
Tristar aircraft to operate on the entire
route between the UK and the Falklands.

Anvers Island off the Antarctic Peninsula

Falklands Weather
At latitude 52°S the islands are about thesame distance from the equator as
southern Britain. But with no equivalent of
the North Atlantic’s Gulf Stream in theSouth Atlantic, and the proximity of icebound Antarctica, Falklands’ weather ismore akin to that of northern Scotland or
the Faroe Islands. The treeless andwww.geo-web.org.uk

extensively peat-covered terrain resembles
the Scottish moors too. Prolonged settled
weather is rare and snow cover rarely
persists for more than a few days except on
the peaks which reach about 700 m. In
summer, dry, northwesterly winds fromPatagonia occasionally bring pleasant,warm days to the islands withtemperatures topping 20°C.

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GEO Quarterly No 17Group for Earth Observation

March 2008

Wind circulation around South Georgia forms a cloud-free zone in which the whole island is visible Credit: NASA GSFC

The influence of the Antarctic continent effectively confines thetemperate-climate zone to a narrower latitude band than in thenorth. Also, the Andes mountain range is an effective barrier tothe predominantly westerly flow. At the time, numerical weather
prediction was advancing steadily and forecast accuracies in thenorthern hemisphere were very good but Bracknell’s computer
output for the South Atlantic region was of limited value.
Consequently, forecasting was challenging to say the least, but it
was a nice change from working at Heathrow where, with onlyrare exceptions, computer output had to be followed .
A few weather reports were available in the region but the biggest
aid was satellite imagery. Fax machines of the Muirhead typeusing electro-sensitive paper were the standard in those days andresolution was poor. The Falkland Islands are very close to theedge of Meteosat’s field-of-view and the images from GOES East
rarely extended far enough south to be useful. Polar-orbiting
satellites were the best for the area but radio interference on
137 MHz was a serious problem. However, by trying for every passfrom all the transmitting satellites, including the Russian ones, weusually had some recent data to work on.
Flying Opportunities Within the Falklands
Met Office staff are always encouraged to fly as much as possible
to observe the weather from a different aspect and opportunities
arose often. Apart from the two main islands, East and West
Falkland, 15 of the the smaller offshore islands are populated witha few sheep farmers. FIGAS, the Falkland Islands Government Air
Service, operated small fixed-wing aircraft to link these outlying
settlements to Stanley and, space permitting, would sometimes
drop in at the RAF airfield to pick up Met staff. A small, highwinged Dornier aircraft was operated for the Falkland Island
Government to monitor fishing activities and ensure licensing
compliance. Based on the RAF airfield, it was easy to get flights on
this plane and see some of the remote islands in the archipelago.

38

Helicopters were extensively used to supply the remote military
outposts and it was easy to get a seat on them too. I’d sometimes
get dropped off 30 or 40 km out and walk back to base, following
sheep’s tracks where possible as it’s hard work walking throughthe tough grass and diddle dee, a woody sub-shrub from which thebulk of the peat deposits have formed. The
Argentinians did lay extensive minefields
during the conflict, mostly near Stanley, butwere later able to provide maps of the affectedareas which were subsequently fenced off.
Caution still needed to be exercised though as
there was still much unexploded ordnance lying
around.
Opportunities to fly aboard the Hercules C130
aircraft arose occasionally, and I made threeflights down to South Georgia, the primary
mission of which was to drop supplies and mailto the small British garrison at Grytviken
A reminder of(which has no landing strip). On anotherpast hostilities
occasion, the weather was too poor to attempt adrop but the flight continued southeastwards to the South
Sandwich Islands to check for signs of Argentinian activity.
South Georgia
The submerged Scotia Ridge extends eastwards from the southern
tip of Argentina, just breaks surface at Shag Rocks then rises to
end in a magnificent mountainous arc at South Georgia. Mount
Paget, at 2934 m, is the highest point but most of the island ishigh enough to be permanently icebound; only on a narrow coastal
strip around bays on the sunny northern side is there much in
the way of vegetation.
This part of the South Atlantic is rarely free of cloud but, even if
the island itself cannot be seen on a satellite image, its location

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March 2008

Group for Earth Observation

GEO Quarterly No 17

2004, is dominated by the waves created byMontagu Island but as only about 70 km
separates the islands, interference patterns
are formed where the waves diverge andmeet one another. Although the wakepatterns are moving almost due east in
this image, there is evidence of anotherforce at work resulting in a NW-SE
alignment of cloud. A thermal image would
almost certainly show a thin, higher cloudlayer. Another image of South Sandwich
Island waves, and an explanation of themechanism involved, written by Les
Hamilton, appeared in GEO Quarterly No
11, September 2006.

Map showing the principal islands discussed in this article

can often be ascertained by wave patterns
in the cloud or, sometimes, a complete
clearance of cloud on the lee side of theislands—created when air is forced up andover the island and then dries out as it
descends causing cloud to evaporate. On
rare occasions, as the accompanying image
shows, the entire island can be seen
through a hole in the cloud sheet createdby air motion around the island. Local
winds around an ice-capped island often
lead to extremely turbulent conditions so
the flight into Cumberland Bay, where
Grytviken is situated, is made cautiously
but with plenty of power on to get out oftrouble if it arises. Strong down-draughts
are especially hazardous to low-flying
aircraft but crews are trained to look out
for areas of unusually rough patches of sea
which may be indicative of down-draughts.
South Sandwich Islands
Almost 800 km southeast of South Georgia
lies an arc of small volcanic islands
discovered by Captain Cook in 1775 andnamed Sandwich Land after the 4th Earl of
Sandwich who, at the time, was the First
Lord of the Admiralty. He discovered theeight most southerly islands but Fabian
Gottlieb von Bellingshausen found three
more in 1819.

activity during my visit but, more recently,
the 1,370 m Mt Belinda on Montagu Island
has been very active. Montagu was alreadythe largest in the group when eruptions
began in 2002 but, more than 5 years later,lava flows continue to increase its size.
On my flight the weather was overcast anddull, and only four islands were well seen.
Fine weather is rare but, as in the case ofSouth Georgia, the presence of the islands
is often detectable in satellite images by
their influence on the clouds and, on rareoccasions, this influence is quite
spectacular as the accompanying image
shows. A stable airflow passing amountainous island is disturbed in muchthe same way as a water surface isdisturbed by a ship and these wake waves
can persist in clouds for hundreds ofkilometres before dissipating. This image,acquired by the MODIS instrument on
NASA’s Aqua satellite on January 27,

The Real Antarctica
Military aircraft are normally precluded
from going south of latitude 60°S but whenurgent medical supplies were needed on
HMS Endurance, the UN did authorise aflight. Leaving the Falklands before dawn
on a late summer’s day, we reachedcruising height just as the sun showed overthe horizon: and what a bright sun it was
too! Being so far from man-made pollution,
the air is extremely clear and visibility islimited only by the curvature of the Earth.
It was not long before the peaks of King
George Island pierced the southern horizon
but it took another hour to reach there.
With no air traffic controllers to botherthem, the crew had complete freedom of
the skies and we flew at low, sometimes
very low, level down the western side of
the peninsula, just east of Brabant andAnvers Islands and on towards Adelaide
Island (indicated by the arrow near the leftedge of the accompanying Meteor image).
HMS Endurance, with its bright red hull,
was easily spotted sheltering close to theeast side of the island not far from the
UK’s Rothera research station.

These islands are geologically very young,about 5 million years old, and lie in some
2,600 m of water on the small Sandwich
tectonic plate which is moving east andover-riding the South American plate. The
ocean trench created at this subduction
zone, which lies just east of the island
chain, reaches depths in excess of 8,000 m.
Although the the most southerly island,
Cook Island, is north of latitude 60°S, theclimate is harsh due to wind and ocean
currents coming from the Weddell Sea.
Most islands are glaciated to aconsiderable depth but the smaller
northern ones are almost ice-free during
the short summer. Unsurprisingly, theislands are not permanently inhabited but
they do attract scientists from several
disciplines during the summer months.
Only Zavodovski Island, in the north of thegroup was showing any signs of volcanic

South Sandwich Island Wakes
Credit: Jacques Descloitres, MODIS Rapid Response Team at NASA GSFC

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39

GEO Quarterly No 17Group for Earth Observation

March 2008

HMS Endurance sheltering off Adelaide Island

Part of Montagu Island, South Sandwich Islands.
Ice thickness estimated at 60 m

Banking steeply after a late-winter drop at Grytviken, South Georgia

Candlemas Island, South Sandwich Islands

Dropping supplies at Grytviken, South Georgia

Grytviken, South Georgia, in late summer

40

The author with an inquisitive striated caracara, one of theWorld's rarest birds of preywww.geo-web.org.uk

March 2008

Group for Earth Observation

GEO Quarterly No 17

The supply drop, in perfect weather, wassuccessful and the return flight beganalong a track slightly further east of thesouthbound one enabling distant views of
the vast ice-shelves on the eastern side of
the peninsula. Flying at low level, even at
low temperatures, uses a lot of fuel and,even though we were enjoying superb
weather with only small amounts of highcloud, landing conditions back in the
Falklands were deteriorating rapidly. In
order to have enough fuel to reachMontevideo, Uruguay, our primary
diversion airfield, a tanker aircraft was
despatched and we took on fuel near King
George Island. After a superb day in brightsunlight, we landed in very marginal
conditions at RAF Mount Pleasant.

A mid-summer image of the Antarctic Peninsula and Weddell Sea
received at RAF Mount Pleasant on December 28, 1988
and including Adelaide island (arrowed)

In-flight refuelling near King George Island.

The summer Meteor image opposite,
received in the Falklands during one of myvisits, well shows the edges of thepeninsula’s ice-shelves as they were almost
20 years ago. The huge, tabular ‘bergs at
the bottom of the picture had broken fromthe Filchner shelf and grounded inshallower water. The clock-wise circulation,
known as the Weddell Gyre, is evident inthis image; ice is moving westwards in thesouth and then turns north. A comparison
with more recent images will show
significant changes to the ice edges in thelast 20 years, especially to the Larsen shelf,
across the peninsula from Adelaide Island,
which has now largely disappeared.

Cover and Full-Page

Inside Back CoverTwin depressions march across Europe(top) while a spectacular smoke plumerises from forest fires in Greece(bottom). See John Tellick’s article on
page 28 for further commentary.

ImagesFront CoverFoxe Basin, southwest of Baffin Island,
imaged free from sea ice at the heightof the summer melt season on
September 23, 2007.
Image: MODIS Rapid Response Team at NASA/GSFC

Inside Front CoverOn December 16, 2007, a fire just west of
Dunkirk sent a huge column of smoke
skyward, which fanned out in a streamer
completely straddling the English
Channel. This 250 metre resolution
MODIS image was obtained by NASA’s
Terra satellite at 11:05 UT.
Image: MODIS Rapid Response Teamat NASA/GSFC

Falklands Wildlife
Finally, no writing about this part of theworld is complete without a mention of thediverse wildlife from the tiny tussock birds,
which are so tame they may perch on yourcamera when trying to photograph them, tothe mighty whales of the southern oceans.
The penguins are always fascinating towatch but my favourites are the huge

Both images © EUMETSAT 2007

Back Cover
Just two days before Christmas,
Robert Moore spotted an exceptional
image of the Kamchatka peninsulaamongst his Metop-A images andalerted GEO-Subscribers. It was so
exceptional that we just had toreproduce it here. John Tellick
provided this colour composite copy,
where, totally devoid of cloud, this iceencased region displays its backbone
of volcanos to dramatic effect in theearly light of dawn.
Image © EUMETSAT 2007www.geo-web.org.uk

black-browed albatross which come ashore
only in the breeding season. Fearless ofhumans, they raise no objection to yourwalking carefully through a nesting colony.
A few of the smallest islands have never
had sheep on them and retain the tall,native tussock grass which is ideal for seals
and sea-lions as well as numerous bird
species. As elsewhere, over-fishing is now amajor concern and many species are
suffering as a result but, hopefully, sanity
will prevail and the balance of nature will
be conserved for centuries to come.

Page 8Keith Fraser, who lives in Buffalo, NY,
keeps a regular eye on the Arctic via his
APT station. On December 1, he
obtained a NOAA-17 image showing
new ice building up in a rim around
Hudson Bay which prompted him toseek out this strikingly detailed Terra
MODIS image of the same scene.
Image: MODIS Rapid Response Team ad NASA/GSFC

Page 42
Metop-A imaged the British Isles
enjoying a rare sunny day on January
23, 2008. England is seen emerging
from deep shadow cast by the morning
sunshine. But this respite from therains and flooding was short-lived. The
next Atlantic depression is alreadypriming itself for action to the west.
Image © EUMETSAT 200741

March 2008

Group for Earth Observation

GEO Quarterly No 17

Dear LesI was very happy to see your article It’s a CLASS Act
in GEO Quarterly 16.
The reason is a bit strange. It is because we (my wifeand I) have suffered major water damage in our
house. Many floors, including the kitchen andbathrooms, are damaged so that the house isuninhabitable. We have now been living in our son’s
flat for a number of months. He happens to work in
Melbourne, Australia for a year or so.
This means that I presently don’t have access to mynormal APT-equipment. That is why the possibility toload down data from the CLASS archive comes in sohandy. It is also very good that our son has quite afast broadband connection.
I have followed the procedures in your article andhave; as I believe; been quite successful. It is apleasure to get so much higher resolution images
than with APT and it is also great to be able to get
images from any part of the globe. So I attach animage from eastern Australia. It is from a Metop
FRAC file dated 2008-01-17 at 23:14 UT, whichshould be 10:14 am Melbourne time. The areaaround Melbourne seems to be a little cloudy.
I am still very impressed by the high quality articles inthis issue (and earlier issues) of GEO Quarterly. The
article on the Aral Sea was very interesting, as I now
and then was able to see it on my APT pictures andwas terrified of how small it had become. I also
appreciate the various technical articles on ‘how to
do’ very much.
Best regards
Anders Hook (from Vallentuna, Sweden)

continued from page 23 ...

sufficient kinetic energy to destroy anoperational spacecraft.
India Launches Radar Satellite for Israel
An Indian Polar Satellite Launch Vehicle(PSLV) lifted off from the Satish Dhawan
Space Centre at Sriharikota, on the east coastof India, at 0345 UTC on January 21, carrying
TecSAR to a 403 x 581 km orbit inclined to theequator at 41 degrees.
Developed and built by Israel Aerospace
Industries Ltd and its subsidiary companies,
the 300 kg spacecraft carries an X-band dishantenna for SAR all-weather imaging. The firstimages are expected to be made available
early in February.

Eastern Australia, captured during Metop-A’s morning pass, on January 17, 2008
Image: NOAA CLASS Archive (www.class.noaa.gov/)

Processed in HRPT Reader by Anders Höök

GEO Members’ Internet SurveyaReaders who have been subscribers
since our Launch Issue four years ago
may recall we included a survey form
with that Quarterly. Although we did
publish a sample of the replies, it
proved physically impossible to takeeveryone’s views on board.
GEO would now like to offer its
subscribers the opportunity to voice

their opinions on the Group and tohelp shape its future. To this end, we
have placed a new Survey Form on
our website, which we would verymuch like you to complete.
www.geo-web.org.uk/survey08.html

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

TecSAR satellite
Credit: IAI

www.geo-web.org.uk

43

GEO Quarterly No 17Group for Earth Observation

March 2008

In Conclusion
I apologise in advance for any errors or omissions but, should you
discover any (or an opportunity for improvement), please contact
me at
tohs@rifleman.org.uk.

Perfected this arrangement is not; but it may at least offer aworthwhile basis for further experimentation and will certainly help
to while away the hours!

... continued from page 15

Footnote
noting that, once the first one has been prepared, such schedules
can be copied, pasted (to a temporary holding directory), renamed
and modified to suit.
Appendix A - Displaying Animations
Whichever means of display you use, take care that you do not
attempt to open an animation file whilst it is being built in the
background (as indicated by the presence on your taskbar of thecommand prompt and minimised GSS icons). I have found that thiscan cause unusual reactions, or an error message reporting the fileas unreadable. Indeed, the file may not even show in its directorywhen browsing. In either case the displayed animation may stop
when it is undergoing a rebuild or update.
Appendix B - Bracknell Charts from DWDSAT Data
Should your base of operations be ‘out-in-the-sticks’ and without
Internet access, it is also possible to extract the Bracknell chartsfrom the very EUMETCast data stream which provides the MSG
imagery via the DWDSAT data. You will, of course, have to make afree registration request—via your local Internet café in thissituation. It is a rather laborious manual task to crop and reducethese images to the 1065 x 718 resolution required by GSS but, if
you are au fait with command line and/or batch conversion, thenthis could perhaps be automated. This could certainly be a means
to an end from a remote location.
The DWDSAT service is provided by Deutscher Wetterdienst(DWD), the National Meteorological Service of Germany. DWDSAT
consists of European forecast data and meteorological charts,
which are disseminated via EUMETCast’s European Ku-bandservice. David Taylor has produced a separate program ‘DWDSAT
viewer’ for showing the HRPT images transmitted but the chart
images can be screened by most proprietary viewers, e.g.
Irfanview.
Appendix C - Example Animations
I have uploaded a couple of images and their resultant overlaid
animations on to a private web page at
www.rifleman.org.uk/mslp.htm

The first image shown there has been processed as explained
above, but with a modified version of the ‘LUTLandSea-zw’ paletteselected in the Vis ch field, while the CLUT field was set to ‘none’.
To lose the black arc that would otherwise show at the left-handupper corner of the image, Space is white has been checked.
Crispen is ‘none’. You will see that the image masking, giving thecustomary green land and blue sea, forms the base to a cloud
representation from white for lower warmer levels up to black forcold high level. This is quite a basic presentation, but a satisfactory
grounding for the overlaid charts. As ever, the possibilities here arealmost limitless if you are prepared to spend the time investigating
palette preparation. Les Hamilton has produced the ‘CLUT creator’software to assist such modification. You can download it fromhttp://myweb.tiscali.co.uk/wxsatellite/clutmaker.htm

Appendix D - Passwords
It is important to be aware that Windows Scheduler requires the
input of your Windows username and password to run command
files. If you are one of those who leave these fields blank when
installing Windows, you will soon discover that using a ‘blank’username and password in schedule files will result in them failingto run. A genuine username and password are absolutely
essential.

44

1 Although the Met Office moved from Bracknell to new headquarters
in Exeter during 2004, the term ‘Bracknell’ charts continues in use tothis day—perhaps an acknowledged but happy misnomer—and mostusers still prefer to recognise that naming.

The Complete Earth
A Satellite Portrait of Our Planet
Peter GreenI suppose this is what is called a 'coffee table' book. It's large
enough—36 x 42 cm—and if you have one, you will want to keep iton your coffee table, and not just for yourself: you can bore yourfriends rigid with the fantastic images that it contains.
I am sure we all look at our satellite images of Earth daily andwonder at its beauty. The resolution we get as amateurs is
spectacular, but we all want to see it in even more detail. Some of us
use the satellites to watch the weather, some to look at the Earth.
Well, The Complete Earth: A Satellite Portrait of Our Planet willcertainly help you fulfil these wishes.
The images show the Earth cloud-free at 93 miles to the inch andthe full-colour images are spectacular. I am sure you will be able toview these images on the NASA Blue Marble site, but there isnothing like sitting down with a photo of an area and really studying
it. Social and political boundaries are invisible and irrelevant, what
we see instead is the landscape of the whole Earth—the mountains,deserts, seas and oceans that have shaped human history.
The book is in several sections, starting with satellite images on rockand how it has transformed over time. The bigger picture combines
some of NASA's 3D imaging with satellite and digital images to show
how privileged we are to be able to look down on our planet.
Stunning pictures of cloud-free Arctic and Antarctica with ice flows
and on to North America, Europe, South America, Africa and so on
are all shown in both natural and false colour to highlight areas indifferent spectral bands. Each image has detail of how the area wasformed, what affects it weather wise and how it has been shaped
over millions of years. You get a great perspective of how huge,diverse and stunningly beautiful this globe is.
This cover price of this book is £50, which I would never have paid,
although the quality of printing does perhaps justify the price.
However some stores are selling it at a special price of £25, and I
ordered mine from Amazon, two months ago, for £14, which is asteal.
This is definitely one for your shopping list.
Details
Hardcover: 224 pages
Publisher: Quercus (October 2006)
Language English
ISBN-10: 1905204310
ISBN-13: 978-1905204311

www.geo-web.org.uk

Twin depressions over Europe on June 29, 2007 - see article on page 39
Image © EUMETSAT 2007

Wildfires in Greece show up starkly in the late evening sunshine in this August 25, 2007 image from Meteosat-9
Image © EUMETSAT 2007