Yellow skies look grey from above

You must have seen, in the press or social networks, images like these ones, showing yellow skies ( Loup de Bretagne said "Blade Runner skies"). Such a coloured sky was seen in the west of France, then later in England, and further East in the next days.

The Copernicus Atmosphere Monitoring Service, which keeps track of aerosols has also monitored these aerosols and tracked their provenance : is due to the combined presence of dust, ash from forest fires in Spain and Portugal, and humidity brought by the Ophelia cyclone. The IASI sensor on-board METOP satellites has also monitored the gases absorption due those wildfires.

 

So our question is: how such an event is handled by atmospheric correction software ?

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Venµs' moon

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Well, the audience of our blog is still steady increasing, there is no need to use explicit titles to get more connexions. And although I mainly use space to look down, I do not think the planet has a natural satellite. So why this title ?

The Venµs satellite actually showed us the moon, and not only to provide a nice title in this blog. Our Israeli colleagues from MBT really worked hard to obtain it, as a very good pointing accuracy is needed to image it from a quickly rotating satellite : the moon is far from here !

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Soil moisture maps at a high resolution over Occitania region

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Translated from Theia website.

The Theia forges just released a new product based on Sentinel-1 and 2 data. Le "High resolution soil moisture" Scientific Expertise Center, driven by Nicolas Baghdadi, from Tetis lab in Montpellier and Mehrez Zribi from CESBIO, distributes Soil Moisture maps from the French Occitania region at 20 m resolution, produced every sixth day from September 2016 to May 2017.

Soil Moisture maps for 2 Sentinel-1 images from the 19th and 26th of January 2017, over a part of Occitania région. On the 19th of January, the soil is dry with a moisture between 5 and 15 vol.%. After some precipitations, on the 26th of January 2017, moisture increases between 25 and 35 vol.%.

[MUSCATE news] 40 000 Sentinel-2 L2A products !


Our MUSCATE ground segment just passed a new milestone, with 40 000 L2A products processed with MAJA ! Last week was a bit difficult, with a new repetition of the Friday Night Bug (on Saturday morning this time), followed by a "NFS" issue on CNES computing center that blocked production during two days. We are sorry for those of you waiting for the data in near real time. The production has resumed last Friday. These days, our production includes the near real time production and the processing of data acquired in 2016 over Spain, Italy, Switzerland and Netherlands. Some parts are already available, Burgos in Spain for instance, the others should come soon.

 

 

The version 2.4 of MUSCATE is nearly ready, but a final bug, noticed during the qualification tests remains to be corrected. As soon as it is installed and checked, this version will bring several improvements :

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MAJA presentation at the Recent Advances in Quantitative Remote Sensing symposium, fifth edition

I just came back from Valencia, where I attended the fifth edition of the  Recent Advances in Quantitative Remote Sensing Symposium. It is one of my favourites, thanks to an amazing team of organizers led by Jose Sobrino. It is a unique symposium, because it has only one session  where you can even see opticians listen to radarists, or passive microwaves experts share ideas with active microwave experts ! Every three years, it is a way to gather quickly a good sense of the advances in each domain of remote sensing, over lands mainly. Next RAQRS will happen in 2020 in Valencia, and no doubt I'll be there, and not only for the delicious coffee breaks or for the giant paella.

 

Of course, my talk, available here or visible below, was about Sentinel-2 L2A products, including cloud detection and atmospheric correction. This time, I focused on product validation and provided a lot of validation results obtained by our little team at CNES and CESBIO, with special thanks to Camille Desjardins (CNES) and Bastien Rouquié (CESBIO) and Magdalena Main-Knorn (DLR). I also provided a comparison of MAJA and Sen2cor for various criteria that all show the benefits of using multi-temporal information, as done in MAJA. Despite all that, and although these results were perfectly known by ESA, ESA decided to stick with Sen2cor in their production, supposed to be global next year. The slides explain how this decision was made.

 

Anyway, as you probably know, you can access MAJA products from Theia, or you may also download MAJA's executable (if you have a powerful linux computer).

 

 

 

 

Aftermath of Mathew hurricane over Haiti in 2016

Following Simon's publication on Saint Barthelemy island after Hurricane Irma, one of our twitter friends, @Pierre_Markuse, posted a comparison of the South Western part of Haiti, before and after Mathew huricane ravaged it last year, on the 4th of October 2016. As you can see, the whole lands turn brown just after the hurricane. I am really not an expert, so I just can imagine it is caused by the wind cutting branches and trunks and by water run-off taking the lower vegetation away.  I read that 40% or the  forest and 20% of the shrub has been erased. Moreover, the wind and water must have left mud and dust on the remaining leaves, contributing to the brown color.

 

However, what is amazing is that by end of November, vegetation comes back ! My guess is that mud and dust disappear, shrubs and trees start to grow new leaves and the low vegetation grows back  But experts are welcome to explain how it happens exactly, there is a comment section !

 

I have an additional special own interest in displaying this information :  it is a hard test for how our multi-temporal methods included in MAJA to detect clouds, shadows and aerosols can manage such a case. Continue reading

The Delta of the Ebro seen by Venμs

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The Delta of Ebro

Delta of the Ebro observed by Venμs on August 18, 2017 (Copyright CNES 2017)

The Ebro (Iberus in Latin) flows into the Mediterranean in Catalonia after a journey of more than 900 km from its source in Cantabria. The current morphology of the Delta results from the significant increase in sediment inputs caused in the 15th century by the intensive deforestation of the river catchment: the conquest of the Americas required the construction of boats. It was at this time that the land emerged over the sea, making the delta this wide plain of which only 10% of the land culminates at more than 2 meters. The construction since 1930 of 187 upstream dams reduces the sediment flow (from 28 Mt / year to about 0.1 Mt / year), which partly explains the erosion currently observed in some parts of the delta.

 

80% of the area of ​​the delta is devoted to crops, mostly rice producing one-third of the country's production. The rest, protected by the Natural Park, consists of lagoons, reed and rush beds,  brackish marshes and sandbanks.

 

The Delta de l'Ebre is included in one of the sites that will be observed by Venμs every two days for two and a half years. It is part of ClimaDat, a long-term climate research network. Different issues will be adressed: land use, phenology, greenhouse gas fluxes (CO2, CH4, N2O), vegetation productivity, role of saline inputs.

 

Complement: the evolution of the Ebro delta from the 4th century:

http://geographyfieldwork.com/EbroEvolution.htm

 

 

[MUSCATE] 1141 L2A products in a day !

Yesterday, MUSCATE facility at CNES produced 1141 Sentinel-2  L2A products in a day, while the previous record was 762. A few glitches had reduced the production on the previous days, and yesterday allowed us to catch up the back log. At the same time we have started producing data acquired in 2016 for several zones outside Europe and Africa. The total number of L2A products in MUSCATE now amounts to 33071. Congrats and thanks to the development and exploitation teams !

Hier, le centre de traitement MUSCATE au CNES a traité 1141 produits de niveau 2A de Sentinel-2, alors que le record précédent était 762. Quelques petits soucis avaient retardé la production ces derniers jours, et c'est hier que nous avons rattrapé le retard, et en même temps lancé la production des données acquises en 2016 sur un grand nombre de  zones hors Europe et Afrique. Le nombre total de produits de nievau 2A atteint maintenant 33871. Félicitations et un grand merci aux équipes de développement et d'exploitation !

 

Flooded areas in Houston by Sentinel-1

Hurricane Harvey hit Texas on August 25. The first Sentinel-1 image of Houston since landfall was acquired on Aug 29 at 00:26 UTC. I'm writing this post at 21:09 UTC. As reported by the local news website chron.com "The most severe flooding is around the Highway 90 and Eastgate areas". This is also what we can see on the image comparison below: dark areas are flooded areas:

Click on this link to see in full screen. Or check by yourself in the EO Browser.

Below is a zoom between Dayton and Highway 90 (full screen):

Images are orthorectified VV backscatter in dB (-20 dB is black, 0 dB is white). The backscatter intensity received by Sentinel-1 drops over flooded soil because the emitted electromagnetic waves bounces off the water surface and thus do not return to the antenna (as explained in this post).