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Posts tagged Richat Structure

Clouds by Bay of Arguin, Mauritania

20.1N 16.5W

June 29th, 2011 Category: Deserts

Mauritania - June 21st, 2011

Clouds hug the coast of Mauritania near the Bay of Arguin. Green algae can be observed in the northern part of the bay that is not cloud-covered.

Upon opening the full image, the Richat Structure can be observed in the Sahara Desert to the east of the bay. It has a bullseye-like appearance. Although it looks similar to a crater from a meteorite impact, it is actually thought to be a  symmetrical uplift (circular anticline or dome) that has been laid bare by erosion.


Concentric Circles of the Richat Structure, Mauritania – May 15th, 2011

21.1N 11.4W

May 15th, 2011 Category: Deserts, Image of the day

Mauritania - May 2nd, 2011

A a circular shape featuring concentric rings can be observed near the center of this image. This geographical features is the Richat Structure, also known as the Eye of the Sahara.

It is located in the Sahara desert of Mauritania near Ouadane. The structure has a diameter of approximately 50 kilometres (31 mi) and is located 400–450 metres (1,310–1,480 ft) above sea level.

Initially interpreted as a meteorite impact structure because of its high degree of circularity, it is now thought to be a symmetrical uplift (circular anticline or dome) that has been laid bare by erosion.

Green Algae in the Bay of Arguin, Mauritania – January 22nd, 2011

20.1N 16.5W

January 22nd, 2011 Category: Image of the day, Phytoplankton

Mauritania - January 22nd, 2011

The Bay of Arguin, in Mauritania, appears bright green due to phytoplankton growth. It is south of Cap Blanc, north of Cap Timiris, and contains the islands of Arguin and Tidra. The land to the east is covered by the Sahara Desert.

In the full image, the bulls-eye shaped Richat Structure can be seen to the northeast. Initially thought to be the result of a meteorite impact, scientists now believe it is a symmetrical uplift (circular anticline or dome) laid bare by erosion.

Senegal River Between Mauritania and Senegal

16.6N 15.7W

January 17th, 2011 Category: Deserts, Rivers

Mauritania and Senegal - December 26th, 2010

The dry, tan of the Sahara Desert in Mauritania turns greener and more vegetated at the bottom of this image, in Senegal. Visible roughly at the center of the coastline is the Senegal River, which marks the border between Mauritania and Senegal.

In the upper left quadrant, one can observe the Bay of Arguin, green with algal growth, while in the middle is visible the bulls-eye shaped Richat Structure. In the lower left quadrant, the greenish color offshore is due to sediments from the Geba River in Guinea-Bissau.

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)