As mentioned in a previous operational news, the Cnes-Nasa Joint Steering Group directed the Jason-1 Project to move the satellite to a geodetic orbit.

The target orbit was 12+297/406 with a mean altitude at the Equator of 1323.4 km.
Jason-1 maneuver operations were started on April 23rd with this baseline, and the first operations to lower the orbit were performed on April 25th.  
After an initial series of 4 maneuvers were completed, we encountered a serious new propulsion anomaly which resulted in the unexpected overconsumption of hydrazine.  
A 5th maneuver was designed in order to correct orbital eccentricity.  At the time of this new anomaly, Jason-1 was -12.0 km below the reference altimetric orbit with 600m remaining to reach the -12.6 km goal, however there were very few grams of fuel remaining in the tank to continue orbit lowering.

After checking the current orbit carefully, the operational team determined that a geodetic mission was still possible.  It was also decided to  preserve all remaining fuel for future station keeping maneuvers which is mandatory in a geodetic orbit. Core payloads were switched ON on May 4th and after some POSEIDON2 radar (PRF) adjustments the mission was resumed on May 7th at 15:12:48 UTC.

Below are the characteristics of the new orbit which will be maintained, as before, within +/- 1km control box at the Equator:

Semi major axis:

7702.437 km

Eccentricity:

1.3 to 2.8 10-4

Altitude equator:

1324.0 km

Orbital period:

6730s (1h52'10'')

Inclination:

66.042°

Cycle:

406 days

Sub cycles:

3.9 - 10.9 - 47.5 - 179.5 days

The ground team is currently preparing for the restart of ground processing operations. For this new phase of the Jason-1 mission, the cycle numbering will restart at 500 and the first OSDRs should be produced within a few hours. Off-line products will be produced once a day for the IGDR, and every 11 days for the GDR's.

We will provide more detailed information as soon as the first science measurements on the new orbit become available.

Few weeks after celebrating its tenth year of service, Envisat has stopped sending data to Earth (see our previous news). Esa's mission control has worked to re-establish contact with the satellite but there has been no reaction from the satellite.

Today, Esa declares officially the end of mission for Envisat.

Therefore, no Ssalto/Duacs data from Envisat can be released.

• Esa's website: ESA declares end of mission for Envisat

After 10 years of service, Envisat has stopped sending data to Earth on April 8, 2012. ESA's mission control is working to re-establish contact with the satellite. As is standard practice, an anomaly review board is investigating the cause for the break in communications.

Ssalto/Duacs NRT distributed by Aviso are impacted:
- the along-track data (NRT-SLA and NRT-ADT) : no data after April 9, 2012 in the enn_cf/ folders
- the impact on gridded data (NRT-MSLA and NRT-MADT) is not major for now, since the data are computed using 42 days of data before the date the data represent. If the situation continues, however, the merged grids will be made using only two satellites (Jason-2 and Cryosat), thus with a loss in sampling.

For more information, see ESA Earth news

Ten years ago, the Esa's Envisat mission was put into orbit. For a decade, more than one hundred cycles (with a-35 days orbital period) are counted. Today, the mission is still operational and still contributes to a robust sampling for near-real-time applications. Thus, Envisat is still a key component providing good complementarity with the tandem Jason and Cryosat-2.

The Envisat  altimeter's RA-2 has demonstrated its perfect performances for a wealth of applications: sea level, continental water, ice ... Indeed, thanks to its orbit to make measurements up to ± 82 ° North and South, Envisat is able to reach high latitudes, less available for other missions.

Map of the sea ice thickness anomaly for the 2007/2008
winter (see Image of the month, Feb. 2010,
Credits Centre for Polar Observation and Modelling).

 Antarctica topography as measured by Envisat
for January 2010 (see Image of the month, Oct. 2010,
Crédits Legos/CNRS). 

In October 2010, the Envisat satellite moved to a new lower orbit to ensure an additional 3 years lifespan. This is ensuring the continuity until the next generation of satellites are fully operational in 2013 (Sentinel-3).

• Esa's website: Happy Birthday Envisat!
• Mission: Envisat
• Images of the month:
• Oct. 2010, Envisat measures up Antarctica
• Sep. 2010: ASAR vs altimetry South of Africa
• Feb. 2010: Arctic sea ice shrinks and thins
• Feb. 2009: Water or ice?
• Jun. 2008: Sorting ice from space

The possibility of predicting the extension of a plume with altimetry data is very important for cruise campaigns, because ocean color data are not available in the presence of clouds. In that case, the position of a sampling station can only rely on altimetry data.

During the Keops2, a model of the plume extension ran in near-real time on board the Marion-Dufresne research vessel. The model was fed by the Ssalto/Duacs regional product and allowed to test a novel adaptive sampling strategy, by which the position of the sampling stations were adjusted day-by-day to the position of the plume.

This strategy allowed to monitor the development of the bloom and its biogeochemical dynamics with a unprecedented precision for more than one month with more than 300 biophysical operations. Such detailed observations will serve to better quantify the role of the Southern Ocean on the carbon cycle.

The nice fit between modeled and observed patterns highlights the key role of horizontal transport in structuring in space and time phytoplankton abundance and the possibility of studying this mechanism by satellite altimetry.
Although both altimetric products do a good job, the regional one is clearly better in predicting the southern flank of the bloom extension (see in particular the pattern centered in 79°E 51°S, highlighted by the black ellipses on the figures below). Note that a difference in the plume extension corresponds to differences in the regional primary production and carbon export.

(A-B) Ocean color image from MODIS / MERIS for the 11/11/2011. (A) shows the expected Chlorophyll concentration,
(B) provides the pattern of the chlorophyll plume (obtained by setting a threshold on (A)).
(C-D) Prediction of thebloom extension by a model driven by Ssalto/Duacs altimetry data. Panel C uses the global product, panel D the regional one. Credits LOCEAN/ F. d'Ovidio.

• Centre d'Océanologie de Marseille website: Keops-2 Objectives
• IPEV website: Keops-2, des nouvelles du terrain (in french).
• Club des Argonautes: Prévoir la floraison planctonique (in french)
• Image of the month, April 2009: Cruise around Kerguelen Island
• Access to Ssalto/Duacs data delivered for Keops-2 : first subscribe by filling in the form.