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Posts tagged Meris

Envisat Extension Orbit – Update

41.8N 12.4E

October 28th, 2010 Category: Earth Observation, Events

ESA Envisat-1

The Envisat mission was launched in March 2002 for 5-year nominal lifetime. Consequently the on-board hydrazine capacity was designed for a 5-year duration operation. Careful management of the satellite orbital manoeuvres allowed saving enough hydrazine for operating nominally Envisat for an additional 3.5 years, i.e. until end 2010.

The operations of the Envisat satellite beyond end 2010 require modifying the orbital characteristics of the mission. Careful trading between all possible options led to the selection a new orbit, called the “Envisat Extension Orbit“, which allows:
1) operating the mission for an additional 3 years, with a minimum amount of hydrazine,
2) ensuring the continuity of the maximum number of Envisat applications, with the exception of ASAR interferometry which will be degraded.

The Envisat extension orbit will be implemented through an altitude decrease of 17.4 km which will be reached through different orbital manoeuvres starting on 22 October 2010.

Consequently, the Envisat data flow will be suspended during the period 22 October to 01 November 2010. The data flow will resume on 02 November 2010.

The Envisat mission represents an important goal in the field of Earth Observation. Chelys will follow the entire operation attentively, as we are also the real time image generation software (Miravi) provider for the Meris sensor. This post will be updated in the next few days in order to provide a preview of the Envisat images at the end of the maneuver as soon as its sensors are reactivated.


The last OCM (Orbit Control Manoeuvre) finished in time without problems on October 26th. The satellite instruments are gradually resuming their nominal condition and the dissemination to the users is started. However the ESA disclaimer is clear: users are invited to discard such data until November 2nd, 2010 as they are destined only for the ESA internal verification.

We started generating the first images using the “new” data, and the results, despite some geolocation problems, are very promising. Here below are some images generated after the completion of the manoeuvre.

Argentina from Andes to Ocean (ASAR Image Mode)

Richat Structure in the Sahara Desert (MERIS Full Resolution)

France, Spain and Pyrenees (MERIS Full Resolution)

Strait of Gibraltar (MERIS Full Resolution)

Oil Coats Louisiana’s Shorelines and Reaches into Marshes, USA – May 25th, 2010

25.6N 92.4W

May 25th, 2010 Category: Environmental Disasters, Image of the day

Gulf of Mexico, USA - May 21st, 2010

Gulf of Mexico, USA - May 21st, 2010

Crews try to clean an island covered in oil on the south part of East Bay May 23rd, 2010. (© REUTERS/Daniel Beltra/Greenpeace)

Crews try to clean an island covered in oil

Over one month after the initial explosion and sinking of the Deepwater Horizon oil rig, crude oil continues to flow into the Gulf of Mexico, and oil slicks have slowly reached as far as 12 miles into Louisiana’s marshes. According to Louisiana Governor Bobby Jindal, more than 65 miles of Louisiana’s shoreline has now been oiled.

BP said it will be at least Wednesday before they will try using heavy mud and cement to plug the leak, a maneuver called a “top kill” that represents their best hope of stopping the oil after several failed attempts.

Based on low estimates, at least 6 million gallons of crude have spewed into the Gulf so far – though some scientists have said they believe the spill already surpasses the 11 million-gallon 1989 Exxon Valdez oil spill off Alaska as the worst in U.S. history.

New FAPAR/MGVI Raw Data Processor for Monitoring Vegetation Cover

October 2nd, 2009 Category: Climate Change, Earth Observation, Image of the day, Mosaics

FAPAR Index - Source and Processed products

FAPAR Index - Source and Processed products

FAPAR - Source Product

FAPAR - Source Product

FAPAR - Processed Product

FAPAR - Processed Product

Envisat’s Medium Resolution Imaging Spectrometer (MERIS) acquires multi-spectral imagery of the Earth, and is used to monitor the state and evolution of the terrestrial vegetation cover.

In particular, the MERIS Global Vegetation Index (MGVI), which corresponds to the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), is generated operationally as a standard level-2 product, using the radiation measured by MERIS over land surfaces.

This bio-geophysical product plays a critical role in the plant photosynthetic process and is regularly used in diagnostic and predictive models to compute the primary productivity of the vegetation canopies.

FAPAR has been established as a fundamental surface parameter by international organizations including the Global Climate Observing System (GCOS), charged with providing data on the Earth’s climate system.

Chelys has developed a new processor that is able to process and directly extract the FAPAR index from raw data (level-0) at a reduced or full resolution (but also from level-1), generating the relative false-colored image just a few seconds after the original data is ingested.

In the next few weeks, a processor that will systematically generate these vegetation index images will be incorporated in the SRRS (Satellite Rapid Response System). As soon as enough images have been collected, it will be possible to generate mosaics as well.

The World from MERIS – Summer 2008

September 11th, 2009 Category: Mosaics

The World from MERIS - Summer 2008

The World from MERIS - Summer 2008

Over 2000 Level0 Reduced Resolution products from the MERIS instrument onboard the Envisat satellite were collected in the time period from January to August 2008 and processed by the Chelys Satellite Rapid Response System (SRRS) to generate high quality images.
The images were projected to obtain this composite view using MOSRI, a real time mosaic generation system, which automatically removes clouds and shadows while combining the data.

The new mosaic is available at different resolutions in the MOSAICS section of the EOSnap website.

SAR-Sharpened MOSAIC of Italy

41.8N 12.4E

August 26th, 2009 Category: Image of the day, Mosaics


SAR-Sharpened Mosaic of Italy

SAR-sharpening of Sardinia

SAR-sharpening of Sardinia

The main image here was realized by merging ASAR and MERIS orthorectified Mosaics of Italy, generated by Chelys MOSRI, using a technique we call “SAR-Sharpening” due to its similarity to a method known as PAN-Sharpening.

PAN-Sharpening merges high resolution panchromatic and lower resolution multispectral imagery to create a single high resolution color image. “SAR-Sharpening”, on the other hand, uses a radar image instead of a panchromatic one.

In this image, we maintained the resolution of the MERIS sensor (250m) while greatly enhancing the level of detail using an ASAR mosaic with a 75m resolution.

The animated imagery focusing on Sardinia shows the improvements made through the SAR-Sharpening technique. Due to its resolution, the original color MERIS image clearly has a level of detail inferior to that of the ASAR image.

However, after the processing, the contours of the Italian terrain can be seen in great detail.

ENVISAT Sensor Coverage

ENVISAT Sensor Coverage

ASAR operates simultaneously with the other ENVISAT instruments. The image on the left shows the swath positioning of ASAR along with those of the other sensors.

Chelys is currently exploring the possibility of enhancing the capabilities of their SRRS (Satellite Rapid Response System) processors, enabling them to automatically generate SAR-Sharpened images for all zones in which ASAR and MERIS images overlap.