Group for Earth Observation

No 61 - March 2019

This MODIS image is part of an Aqua X-band transmission dating from February 11 this year, captured by Canadian Jean-Luc Miletteusing homebrew equipment. The segment displayed above measured 8300 pixels in width and was cropped from the full transmission
which measured 13384 × 15040 pixels. Jean-Luc describes his set-up in an article on page 11.

Useful User Groups

GEO MANAGEMENT TEAM
Director and Public Relations

Weather Satellite Reports

Francis Bell,

This group provided weekly reports, updates and news
on the operational aspects of weather satellites.
https://groups.io/g/weather-satellite-reports

Coturnix House, Rake Lane,
Milford, Godalming, Surrey GU8 5AB,
England.
Tel:

SatSignal01483 416 897

This end-user self help group is for users of David
Taylor’s Satellite Software Tools, including the orbit
predictor WXtrack, the file decoders GeoSatSignal and
SatSignal, the HRPT Reader program, the remapper
GroundMap, and the manager programs - MSG DataManager, GOES-ABI Manager, AVHRR Manager etc.
https://groups.io/g/SatSignal

email: francis@geo-web.org.uk

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

GEO Newsletter Editor

MSG-1

Les Hamilton,

This forum provides a dedicated area for sharing
information about hardware and software for receiving
and processing EUMETCast data.
https://groups.io/g/MSG-1

email: geoeditor@geo-web.org.uk

Technical Consultant (Hardware)David Simmons

GEO-Subscribers

email: tech@geo-web.org.uk

This is the official group is for subscribers of the Groupfor Earth Observation (GEO), aimed at enthusiasts
wishing to exchange information relating to either GEO
or Earth Observation satellites.
https://groups.yahoo.com/neo/groups/
GEO-Subscribers/info

Webmaster and Website Matters
Alan Banks,e-mail: webmaster@geo-web.org.uk

GEO Shop Manager
Nigel Evans

Meteor M N2-2 Delayed Again(Assistant: David Simmons),
email: shop@geo-web.org.uk

Last issue we reported that Russia’s next Meteor weather
satellite, Meteor M‑N2-2, was provisionally set for launch
during March 2019. But there has been a further delay,
and the WMO’s OSCAR website now states that thelaunch is now unlikely before June 2019 at the earliest.

Management TeamDavid Anderson
Rob Denton
Clive Finnis

You can keep up to date with any changes to thisinformation at the following URL
https://www.wmo-sat.info/oscar/satellites/view/483

Carol FinnisPeter GreenDavid Taylor

Peter Kooistra obtained this Feng Yun 3D image of theEtna eruption plume on December 27, 2018. You can readmore about this eruption on page 9 inside.

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www.geo-web.org.uk

Les HamiltonFor years it has been promulgated that ever increasing data rates, andtransmission frequencies in the X-band, would lead to the demise of
direct reception of high resolution weather satellite imagery by amateurs.
But not so.

Earlier this year I received a memo from David Taylor to alert me that
Jean-Luc Milette from Québec, Canada had been receiving X-band datafrom NASA’s Aqua and Terra satellites, as well as NOAA 20 and China’s
Feng Yun 3D. What’s even more remarkable is that he is doing so using ahand-tracked dish! One of Jean-Luc’s recent images is reproduced, in parton the front page of this Newsletter. The original 132 MB image measured
a staggering 11384 × 15040 pixels.

The outcome is that we have an article, starting on page 11 of this issue,
where Jean-Luc explains the home-brew system he has devised toachieve this remarkable breakthrough. It’s not a full scale construction
project, but it should be sufﬁcient to allow those of you who have beenheavily involved in home-brew projects over the years to emulate his
system.

As you will read elsewhere in this issue, it is with regret that a very poor
response to the proposed visit to EUMETSAT next July has resulted
in the trip having to be put off— for this year at least. We will address thepossibly of such a visit again in the future, perhaps as early as 2020 if
there is sufﬁcient interest.

F

inally, a reminder that GEO is always interested in learning about
initiatives being undertaken by our readers. Jean-Luc’s enterprising
foray into the world of X-band underlines what is becoming possible.
Should any reader contemplate following in his footsteps, we will
welcome it if you get in touch and share your experiences with the GEO
community.

Materials for publication are always welcome, by email, togeoeditor@geo-web.org.uk

Contents
GEO Report
Quarterly Question
Australia’s Disappearing Lakes
South Georgia
Etna Awakens
How to receive X-bans Weather Satellites
Makgadikgadi Salt Pans
Clouds and Eddies off Newfoundland

Francis Bell
Francis Bell
NASA Earth Observatory
European Space Agency
NASA Earth Observatory
Jean-Luc MiletteNASA Earth Observatory
MODIS Image of the Day

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6
7
8
9
11
17
19

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Francis Bell
Darmstadt Visit
Rather distressingly, I have to report the very poor
response there has been for our planned GEO visit toDarmstadt on 4th July this year. I spite of the long noticethat has been given for this visit and the encouragement
relating to the success of our past visits to date there have
only been eight registrations for our Darmstadt visit thisyear.
My judgement is that a group of eight or thereabouts
does not justify the potential disruption our visit would
cause to the leading international space agencies such as
EUMETSAT, ESOC and their associated ground stations.
For our last GEO visit in 2015 we had 28 members in thegroup and in other years our number have been in excess
of 30. Just check the number of our members shown in our
photographs of previous visits.
I note that in our past visits to Darmstadt, our hosts went
to the trouble of organising detailed tours of their facilities,
providing guides, plus making formal presentations
relating to some technical aspects of their weather satellite
reception. For a group of eight this would be unreasonable.
Because of the lack of widespread support for our
proposed visit I have decided to cancel this year’s visit

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to Darmstadt. I cannot personally justify the disruption
we would cause to the space agencies for such a small
number of visitors. Perhaps we can try again in 2020.
I will contact directly those who have already registeredwith Rob Denton with the news about the cancellation of
our 2019 Darmstadt visit.
I am very disappointed with the outcome of this planned
visit to our friends at EUMETSAT and ESOC not tomention missing the social experiences we have enjoyedin the past.
GEO Accounts
Again this year we are publishing our annual accounts
on our website because we have not had a membership
meeting during 2018.
When GEO was first established it was decided to create
two bank accounts: the ‘Membership A/c.’ and the ‘Shop
A/c’. The Membership A/c was intended to deal withmembership subscriptions, printing and the distribution
of GEO Quarterly, together with other costs involvedin running the group. The Shop A/c was, as the nameindicates, to deal with the modest trading within the groupof electronic equipment and software. This also gave a

www.geo-web.org.uk

degree of autonomy to the Shop business, although there
has recently been some overlap because the Membershipaccount income has declined.
Notes
The sales and receipts include some late membershipsubscriptions, via PayPal, which we have now stopped
taking. Most of the printing and postage charges wereleftovers from the publication of our final printed GEO
Quarterly. There may be a small PayPal charge for lastyear but it will have to be included in our 2019 accounts.
The value of any equipment that has been purchased to
run our group over the years, for example two computers
to run displays at exhibitions has been written off and, as
best I know, the Shop stock is minimal. The total assetsof our group are the balances in the two bank accounts
with liabilities limited to running the website and the small
annual Companies House fee. As director of GEO I haveto submit our accounts to Companies House annually.
Coming Event
GEO will have its usual stand at the West London
Electronic Show which is to be held at Kempton Park in
14th April 2019. This is usually a busy show covering theinterests of amateur radio and electronics. The public entry
starts at 10.00 a.m. and the show closes about 3.00 p.m.
The cost of entry is just two or three pounds. For additional
details go to www.radiofairs.co.uk
Quarterly Question Number 59 Revisited
Further to my piece on Stromboli last issue, I thought thefollowing notes extracted from the Wikipedia website mightprove of interest.

Map showing the location of Stromboli
Image: Wikimedia Creative Commonsis maintained in which explosions occur at the summit
craters, with mild to moderate eruptions of incandescentvolcanic bombs, at intervals ranging from minutes to hours.
This Strombolian eruption, as it is known, is also observed
at other volcanoes worldwide. Eruptions from the summit
craters typically result in a few short, mild, but energetic
bursts, ranging up to a few hundred meters in height,
containing ash, incandescent lava fragments and stone
blocks. Stromboli’s activity is almost exclusively explosive,
but lava flows do occur at times when volcanic activity
is high: an effusive eruption occurred in 2002, the first in
17 years, and again in 2003, 2007, and 2013–14.

Stromboli, photographed in 2004
Photo © Steven W. Dengler / Wikimedia Creative Commons

Stromboli is a small island in the Tyrrhenian Sea, off thenorth coast of Sicily, containing one of the three active
volcanoes in Italy. The volcano has erupted many times
and is constantly active with minor eruptions, often visible
from many points on the island, from the surrounding
sea and satellites, giving rise to the island’s nickname‘Lighthouse of the Mediterranean’. Stromboli stands
926 metres above sea level, and over 2,700 metres, on
average, above the local sea floor.
Mount Stromboli has been in almost continuous
eruption for the past 2,000 years. A pattern of eruption

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Francis Bell
Quarterly Question 60
The answer to the last Quarterly Question which asked for theidentification of a country from its political and coastal outline
was Mexico. My thanks to those who emailed me with thecorrect answer.
The reason I picked this as a question was because of theunusual appearance of the country which is almost always
shown with its land connection with Central Americancountries to the south and the USA on its northern border.
However, the major clue for me to the country’s identity was
the very clearly shown Baja California peninsula, which I havevisited twice.
Quarterly Question 61
This Quarterly Question relates to an image taken by theCopernicus Sentinel 1A Satellite in 2015. The question isquite straightforward—name the island group shown in theimage and the approximate location of this group. The edited
text below has been taken from ESA material published withthe satellite image and contains both technical information andenough place names for a reader to identify the island group.
Please send your answers, by May 26, 2019, tofrancis@francisbell.com
ESA Text
This Sentinel-1A radar image was processed to depict waterin blue and land in earthen colours. It features some islands,
including the turtle-shaped Faial, the dagger-like Sao Jorge
and Pico Island, with Mount Pico reaching over 2351 metresin height. The image highlights the differences in the relief of
the islands, with volcanoes and mountains clearly standingout.

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Faial is part of the central group of the islands. The
surface area covers 173 km2. It has some 15 000
inhabitants and its main municipal seat is the city of
Horta. Different shades of blue decorate the houses,
which divide the fields and line the roads, giving Faial
the name ‘Blue Island’.
In the 18th century, the development of whale hunting
brought whaling fleets to Horta. By the 19th century,
Horta had become an important seaport and a layoverfor a large number of yachts crossing the ocean. Alongwith other islands in the archipelago, Faial is of volcanic
origin. In 1957, a big eruption about a kilometre offshore
ejected large quantities of lava and ash, forming an islet
that later became connected to Faial by an isthmus.
Unique among these islands São Jorge isuncharacteristically long and slender, and so susceptible
to oceanic erosion. The island is 55 km in length, with amountain range forming its backbone. At 1053 metres,
Pico da Esperança is its highest summit. The island
has an area of 246 km2, with an obvious difference inthe relief between the western and eastern sections:
the western coast is lined with cliffs, while the east issmoother. Similarly, the northern coast has sharp cliffs,
while the southern side is less inclined.
The island’s 9500 residents have lived in relative
isolation for many years. Disturbed only by rare visitsfrom the authorities, commercial boats from the local
islands, or the occasional aristocrat who comes tocontemplate the local scenery, life on São Jorge is veryrelaxed.

www.geo-web.org.uk

Australia’s Disappearing Lakes Disappear Even MoreNASA Earth Observatory
In December 2016, the Menindee Lakes of New South
Wales were nearly brimming with water. More than
two years later, these Australian lakes are almost
totally dried out.
These satellite images show the dwindling water levelsof the Menindee Lakes, a chain of freshwater lakes
located 110 kilometres southeast of Broken Hill. The
shallow natural depressions were developed into water
storage by the Australian government to manage riverflows. The images were acquired by the Operational
Land Imager carried by NASA’s Landsat 8 satellite on
January 27, 2017, February 15, 2018, and February
2, 2019, shown top to bottom at right..
Water levels often fluctuate as the basins collectprecipitation or flood water. Evaporation accounts
for about 400 gigalitres of water loss from the lakes
every year. At other times the water is released into
the nearby Darling River by the New South Wales
government. During drought, when less water iscoming into the lakes, the basins tend to be drier.
Lake Menindee is the largest of the lakes. But
river managers have been keeping as much water
as possible upstream in Lake Wetherell and Lake
Panamaroo, which supply water to Broken Hill
and local communities. Recent years have brought
exceptional drought to the area. New South Wales
has faced extremely hot temperatures and low
precipitation, causing one of its worst droughts onrecord.
The Lower-Darling River has been experiencing‘extreme low inflows’ of water from the Menindee
Lakes since August 2018. As of February 18, 2019,
the Lower-Darling’s storage level had fallen to justone percent. Water has stopped flowing in parts of theriver.
Public concerns drastically increased when millions
of fish were found floating belly-up along the DarlingRiver on three separate occasions in January 2019.
The massive fish kills stemmed from a series of
events. As water levels fell, the river stopped flowing,
and temperatures were high—creating ideal conditions
for blue-green algae to bloom. When a cold front swept
through the area and killed the algae, the populationof bacteria that feeds on the algae then blossomed.
These bacteria consumed most of the available oxygenin the water, causing the fish to suffocate. Somesources say the massive fish kills were partly due to
how the Menindee Lakes are managed, while others
blame global warming and drought.
NASA Earth Observatory images by Lauren Dauphin, using Landsat datafrom the US Geological Survey.

Story by Kasha Patel.

www.geo-web.org.uk

7South Georgia
European Space Agency

Copyright: Image contains modified Copernicus Sentinel data (2018), processed by ESA,Creative Commons Attribution-ShareAlike 3.0 IGO (CC BY-SA 3.0 IGO) licence

The Copernicus Sentinel-2 mission
takes us over the island of South
Georgia. Linked with the South
Sandwich Islands to form a British
Overseas Territory, this southern
Atlantic island is a haven for a vastarray of wildlife.
Around five million seals call theisland home, as well as 65 million
birds of 30 different species. Migrating
whales and various fish species
populate the surrounding waters andthere is a large penguin population.
First discovered by Captain James
Cook in 1775, there is no permanenthuman population on the island, due
to its remote location and inhospitableenvironment. Nevertheless, a British

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Antarctic Survey research station
operates in the capital, King Edward
Point, in the island’s centre. This is acentre for applied fisheries research,while on Bird Island, lying off thenorth-west tip of South Georgia,
scientists and support staff focus on
research into bird and seal biology.
As the image clearly shows, South
Georgia is mostly covered in snow.
Its polar climate gives it short andvery cold summers, and long, freezing
and overcast winters. The rugged
landscapes of the island are often
said to leave visitors in awe, with two
mountain ranges dominating—the
Allardyce towards the middle of theisland and Salvesen in the south.

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In 2012 the UK Government
designated South Georgia as one of
the world’s largest sustainable use
Marine Protected Areas. Significant
investment has also been made infisheries management and scientificresearch, as well as targeted
conservation efforts to help protect thealbatross. South Georgia is home to
the Wandering Albatross—the largest
flying bird species in the world.
Sentinel-2 is a two-satellite mission to
supply the coverage and data delivery
needed for Europe’s Copernicus
programme. The mission’s frequent
revisits over the same area and highspatial resolution allow changes ininland water bodies and the coastal
environment to be closely monitored.

Etna Awakens on its SideNASA Earth Observatory
For the first time in perhaps a decade, Mount Etna experienced a ‘flank
eruption’—erupting from its side instead of its summit—on December 24, 2018.
The activity was accompanied by 130 earthquakes occurring over three hours
that morning, some attaining magnitude 4.3. Mount Etna, Europe’s most active
volcano, has seen periodic activity on this part of the mountain since 2013.
The image on the right was acquired by the Operational Land Imager (OLI)
on the Landsat 8 satellite and shows the ash cloud emitted by the volcano on
December 28, 2018. The lower image highlights the active vent and thermal
infrared signature from lava flows, which can be seen near the newly formed
fissure on the southeastern side of the volcano. The image was created withdata from OLI (bands 4-3-2) and the Thermal Infrared Sensor (TIRS) on
Landsat 8.
Ash spewing from the fissure cloaked adjacent villages and delayed aircraftfrom landing at the nearby Catania airport. Earthquakes occurred in thesubsequent days after the initial eruption and displaced hundreds of people
from their homes, according to news reports.
NASA Earth Observatory images by Joshua Stevens, using Landsat data fromthe US Geological Survey.
Text by Kasha Patel.

Figure 1 - Mount Etna and its Ash Cloud

Figure 2 - The the active side vent and thermal infrared signature from lava flows at Mount Etna, in Sicily, on December 28, 2018.,
NASA Earth Observatory images by Joshua Stevens, using Landsat data from the US Geological Survey.

www.geo-web.org.uk

9This Meteor M2 channel-5 infrared image was received in Aberdeen, Scotland at 20:06 UT on the evening of January 30, 2019
during the coldest spell of weather experienced by the British Isles since 2010. The country is almost cloud-free, and whilesouthern England was relatively mild at -6°C, Braemar in Scotland’s Grampian Highlands recorded a low reading of -14.5°C.

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How to Receive X-Band Weather Satellites
Jean-Luc Milette
At first, I thought that amateur receptionof X-band weather satellite images would
be impossible. It needed equipment
costing $15,000 dollars or more. Then I
thought that, if people can receive DeepSpace probes as amateurs, I should be
able to receive X-band signals too.
I had no downconverter, no LNA, nothing
so I had to start from scratch. Where
could I find a downconverter? I searched
the internet but found almost nothing.
Maybe I could use a modified Ku band
LNB that I had available?
I first checked the Web to learn which
frequencies the X-band weather satellites
were using:
Satellite

Frequency (MHz)

Aqua

8160

NOAA 20

7812

Feng Yun 3D

7820

Terra

8212.5Figure 1 - Remove the bandpass filter

Sourcing a Suitable LNB
A normal Ku band downconverter has an
IF frequency from 950 to 1450 MHz. So,
for a normal Ku band downconverter, thelocal oscillator frequency is 10750 MHz.
This covers 11700 to 12200 MHz.
Let’s start with Aqua satellite,
10750‑8160=2590 MHz, which isbeyond the IF frequency of the stock
downconverter. So the stock LNB oscillator
frequency is no good for X-band.
Fortunately, my stock LNB had a DRO
oscillator. I searched the Net, and foundreplacement DRO pucks which had a9475 MHz frequency.

Figure 2 - The stock LNB after removing the bandpass filter

So, repeating the calculation for the Aqua
satellite: 9475-8160 MHz=1315 MHz,
which is now within the LNB IF frequency.
Now repeating the calculation, this timewith NOAA 20: 9475-7812=1663 MHz, avalue not too far from 1450 MHz.
But then, I thought, there are alreadysome Ku band downconverters on themarket which use a 9750 GHz internal
oscillator, so these should work right ofthe box?

Figure 3 - The completed modification

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Figure 4 - This section from Jean-Luc’s front cover Aqua MODIS image centres on the Gulf of
St Lawrence, and emphasises the resolving power of the image

I ordered a PLL LNB with the 9750 MHz internal
oscillator but, after testing, found that the chip
inside the PLL LNB has a filter to block X band
reception. So it was back to square one and my old
LNB.
I opened it and removed its microstrip bandpass
filter (figure 1). Then I removed the old DRO puck
and installed the new one with 9475 MHz (figs 2, 3).

12This worked, but it had very low sensitivity, because
the stock waveguide was simply too small for
X‑band. So now I had to make a waveguide myself.
The Waveguide
The waveguide consists of a length of copper pipe
(figures 5, 6, 7, 8). When testing, I slotted the copper
tube in order to be able to play with the backend
distance. After a lot of testing, the distance fromwww.geo-web.org.uk

Figure 5 - Waveguide Prototype Schematic

Figure 6 - The Waveguide

Figure 8 - The teflon Polarizer

Figure 7 - The Prototype Feed

Figure 9 - The Lotus Communications 2-18 GHz 1.4 dB NF LNA

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probe to backend should be 16.8 mm. The probe
length is 10 mm. These measurements are to be
used without the sliding probe. (Simply make a holein the tube and solder it to your SMA connector.)
The waveguide length is not critical: I used
19 centimetres.
Stock Ku band LNA modifications
At first, I tried to input the signal directly to thefirst stage transistor, but I had oscillation problems.
So I input the signal to the second transistor, andthen it worked. The LNA I am using is a Lotus
Communications 2-18 GHz 1.4dB NF (figure 9).

Figure 10 - The whole Downconverter and LNA

SDR
For SDR, at first I used a HackRf with the Aqua
satellite. This satellite transmits with a bandwidthof 15 MHz, so I chose a 16 MHz sampling rate withHDSDR software.
For Feng Yun 3D, you need an SDR capable ofcovering at least 30 MHz. I currently use a LimeSDR
with 40 MHz sampling. Speaking of sampling, if you
want to be serious in X-band reception, consider
using an SSD hard drive.
Demodulation
For demodulation, I use GnuRadio for Windows. I
have written the scripts myself. But they are freely
available.
After demodulation, which creates soft bits, I createda program in C++ to transform from soft bits to
CCSDS frames. This program is also free. Finally, I
created another program to convert CCSDS frames
into a picture.
Additional Satellite Information
NOAA 20

Aqua/Terra

Feng Yun 3D

RHCP

RHCP

RHCP

QPSK

QPSK

QPSK

FEC 1/2

no FEC

Double FEC 3/4

Symbol Rate 15 MHz

Symbol Rate 7.5 MHz

Symbol Rate 30 MHz

Bandwidth 30 MHz

Bandwidth 15 MHz

Bandwidth 60 MHz

Resolution 475 m/pixel Resolution 250 m/pixel Resolution 250 m/pixel

Feng Yun 3D uses two viterbi encoders, so decoding
requires two viterbi decoders.
Regarding Dish Size

Figure 11 - The author’s 1.7 metre dishwaveguide is linear polarization, so to convert fromlinear to circular you need to insert a piece of teflon
just at the waveguide mouth, this will give you a
3 dB gain.
The teflon polarizer should be placed at a 45° angle
relative to the probe (figure 7). If you don’t use theteflon part, it will still work, but you will lose 3 dB.

At first, I used a 1.7 m dish with good results from
Aqua satellite. But, the bigger the better, I bought a
2.4 m dish. I can say that with NOAA 20, 2.4 m is amust, the signal fluctuates and is lower than othersatellites.

Have fun !!

Aqua is the strongest, Feng Yun 3D also. But do notforget these satellites use circular polarization. Theor email to

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For software download or questions, contact me on
Twitter athttps://twitter.com/LucMilette?lang=en

www.geo-web.org.uk

jlm80286@hotmail.com

Figure 12 - This image of Nova Scotia showing detail of Cape Breton Island and part ofPrince Edward Island came from a NOAA 20 transmission on January 13, 2019.

Figure 12 - An Aqua waveform during decodingwww.geo-web.org.uk

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Figure 13 - This image of stretching from Hudson Bay to Nova Scotia was acquired from a pass of China’s Feng Yun 3D satellite.

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www.geo-web.org.uk

Makgadikgadi Salt Pans
NASA Earth Observatory

The Makgadikgadi Salt Pans, imaged by NASA’s Terra satellite on June 10, 2018.
NASA Earth Observatory image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response

Northeast of Africa’s Kalahari Desert and southeast of the
Okavango Delta lies one of the largest salt pans in theworld. It was once the site of one of the largest inland season Earth.
On June 10, 2018, the Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s Terra satelliteacquired this natural-colour image of the Makgadikgadi
Salt Pans. The collection of salt flats covers roughly 30,000
square kilometres (10,000 square miles) amidst desert
and dry savanna in Botswana. Located in Makgadikgadi
National Park and Nxai Pan National Park, the salt pansare rivalled in extent only by the Salar de Uyuni in Bolivia.
For much of the year, the salt pans glimmer in white,parched by the sun and the salt and allowing little morethan algae to grow. But during the rainy season (roughly
November to March), the area can be transformed into a

crucial wetland. Water can flow in from the Boteti and Natarivers, filling ephemeral ponds, watering holes, and shallow
lakes and creating short-lived but abundant grasslands.
The event draws migrating wildebeest and zebras, as wellas the predators that hunt them. The waters fill with ducks,
geese, pelicans, and flamingos—one of just two breeding
spots in southern Africa for the long-legged birds.
The pans are the salty remains of ancient Lake
Makgadikgadi. Scientists estimate that the inland sea
once spanned anywhere from 80,000 to 275,000 square
kilometres. The Okavango, Zambezi, and Cuando rivers
likely emptied into this lake until tectonic shifts changed theelevation of the landscape and a changing climate dried up
the rains.
Story by Mike Carlowicz.

www.geo-web.org.uk

17Viewed in context, the Makgadikgadi Salt Pans appear at centre right in this wider view, with the Okavango delta clearly visible to its northwest.
NASA Earth Observatory image by Joshua Stevens using Terra MODIS data from LANCE/EOSDIS.

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Clouds and eddies off Newfoundland and Labrador, Canada
MODIS Image of the Day
A complex pattern of clouds, snow,
ice and ocean was captured in atrue-colour image by the Moderate
Resolution Imaging Spectroradiometer(MODIS) on board NASA’s Terrasatellite on January 9, 2019 as it
passed over the Hamilton Inlet in
Newfoundland and Labrador, Canada(figure 1).
The land surrounding Hamilton Inlet,
lying in the south-west third of thisimage, sports a snowy blanket while
the waters of the inlet appear brightwhite, which means they are coveredin ice. Heavy banks of clouds cover
the western side of the image, insome places obscuring the land
from view. These clouds thin as they
stretch towards the east. A secondbank of marine cloud can be seenalong the eastern edge of the image.

Figure 1
Image acquired by NASA’s Terra satellite on January 9, 2-19 by combining bands 1, 4 and 3.
Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Between these banks of clouds, clear
skies allow visualisation of a peculiar
pattern of bright white swirls just off
the coast. While these appear to bewhite clouds, they are almost certainly
actually formed by ice caught in
the offshore eddies of the Labrador
Current. The Labrador Current flows
from the Arctic Ocean southward
along the coast of Labrador andaround Newfoundland to the east
coast of Nova Scotia.
Each year, Arctic sea ice increases
throughout the winter, reaching its
maximum extent around March.
It then melts during the summer,
reaching its minimum in September.
By January, Arctic freeze-up iswell under way in many locations,such as off the coast of Labrador
and Newfoundland. As ice begins
to freeze, it remains malleable andcan easily break into many small
fragments. Such fragments canbe stirred by ocean currents into
cyclone-shaped vortices that may
range in size from a few hundred feetto a few hundred miles in diameter.
Ice eddies are most common in thespring and fall months when the ice
is warm enough to fragment, but stillcold enough to remain frozen as it is
moved by the ocean current.

Figure 2
Image acquired by NASA’s Terra satellite on January 9, 2-19 by combining bands 7, 2 and 1.
Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Swirls of ice imitating cloud
When seen from space, complex
winter scenes that include cloud,snow, and ice may look like amagnificent study in white. Thanks tosimilar reflectance values, cold andfluffy clouds, brittle and frigid ice, andsoft, fluffy snow all appear similar intrue-colour satellite imagery. While
this conveys the power and chill of a
winter landscape, scientists frequently
need to be able to differentiatethese features. To tell the difference
between snow, ice, and cloud,scientists often turn to false-colour
images.

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In a false-colour image from thesame Terra pass (Figure 2), which
combines both infrared and visible
light (true-colour uses visible lightonly), the differences between ice,cloud, and snow are readily apparent.
Ice now shows in mid-range blue
while vegetation appears green,snow appears bright turquoise, water
appears black, and cloud renders
as white or, in some areas, very
light pink. With this combinationof channels the swirls are easily
recognised as ice which has beenswirled into eddies by the off-shore
currents.

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Robert Moore shared this Metop-A image received on January 28, 2019, and wrote “The British Isles have been under cloud for a long time. Today’s
Metop-A image shows England, southern Scotland and much of Wales cloud free. In addition to the obvious heat islands of Manchester, Merseyside,
Birmingham and London, many smaller towns show clearly in this image.”
Image © EUMETSAT (2019)20www.geo-web.org.uk

This remarkable APT image showing a band of heavy rainfall crossing the North Sea during a storm on December 18, 2018 was sent to us by André
T’Kindt from Ronse in Belgium. It is a composite, created in WXtoImg, from NOAA 15 and NOAA 18 passes using mcir/precipitation mode.

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A ‘medicane’ was reported on GEO-Subscribers internet forum by John Tellick, on February 24, 2019. The event is well illustrated by this NOAA 20
image transmitted at 12.30 UT on that date. The storm caused havoc over the Mediterranean Sea, particularly around Greece, where shipping was
confined to port to port. There was also a report from Malta of boats being washed ashore and on to roads by rough seas.
Image: NASA’s Worldview (https://wvs.earthdata.nasa.gov/) / EOSDIS

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Many readers have had reason to value assistance from the Eumetsat User Service Helpdesk over the years, andNigel Heasman thought you might like to see this photograph he has of two of the helpful ladies who run it,

Joachim Scharrer sent in some interesting GIS processed images from Russia’s Meteor M2 satellite. Both theseimage segments have been taken from the 09:39 UT pass on January 21, 2019. The left-hand image shows the
British Isles sitting between two weather fronts; the right-hand image has been processed to highlight rainfall.

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There was an early taste of spring when NASA’s Aqua satellite captured this MODIS image of the British Isles on February 15, 2019. The jet stream
was keeping the Atlantic depressions at bay and bathing the region in warm air from the Azores. Most places enjoyed temperatures of 15°C and more.
Image: LANCE, Rapid Response, Global Imagery Browse Services (GIBS), Worldview

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