AVISO: Rss Feeds

SARAL/AltiKa, 12 years old!

Tue, 25 Feb 2025 15:54:50 +0000

SARAL opened the doors of interdisciplinarity thanks to the extended capabilities offered by Ka-band, which allowed to open some new frontiers of classical altimetry, such as coastal oceanography, cryosphere sciences and hydrology.
The quality of all products continues to meet and exceed mission requirements after more than a decade of in-orbit operation, making SARAL an important part of our climate and ocean observing systems. Long live SARAL and many thanks to the SARAL teams!

SWOT Level-3 LR SSH v1.0.2 on AVISO

Tue, 17 Sep 2024 12:47:07 +0000

We are pleased to announce the release of the Basic and Expert SWOT L3_LR_SSH v1.0.2 (2-km) products on AVISO for both the Calibration (cycles 474 - 578) and Science (cycle 1 - ongoing) phases.
Several updates have been made. For more information, see the AVISO SWOT L3_LR_SSH product page available here. The user manual with the various product information is available here. For everything else related to SWOT see AVISOâs one-stop web page is located here. If you do not have a MY AVISO+ account, please fill out the registration page on the AVISO+ website.
If you already have an AVISO account, data access is available through the following services:
CNES AVISO FTP/SFTP (with AVISO+ credentials)

FTP access: ftp://ftp-access.aviso.altimetry.fr:21
SFTP access: sftp://ftp-access.aviso.altimetry.fr:2122
/swot_products/l3_karin_nadir/l3_lr_ssh/v1_0_2

CNES AVISO THREDDS Data Server, TDS (with AVISO+ credentials)

SARAL/AltiKa celebrates 10 years in orbit

Tue, 28 Feb 2023 10:44:38 +0000

The satellite consists of an ISRO SSB (Small Satellite Bus) platform and a CNES payload composed of ARGOS-3 and AltiKa instruments (altimeter, radiometer, DORIS, LRA). Imagined at the turn of the 3rd millennium, AltiKa brought a technological breakthrough with for the first time a Ka band altimeter to measure the topography of the surface of the oceans.
Still working perfectly, the altimeter of AltiKa continues to offer a better resolution to the ground allowing to approach closer the coast or to have access to rivers and lakes on continents and penetrate less profoundly into the snow or sea ice, allowing to collect information of height on these surfaces. So, besides contributing to the observation of the mesoscale ocean circulation, which is essential to understand the dynamics of the ocean and its climatic impacts, the data of AltiKa are also widely used by the community of the glaciologists and the hydrologists.
Thanks to the constant investment of the ISRO, CNES and EUMETSAT operational teams and despite worries about maintaining the precise track on the ground and attitude control, SARAL is relentlessly pursuing its work as an ocean surveyor for the benefit of the international scientific community and the Copernicus Marine Service.
ISRO and CNES are committed to operations at least until the end of 2023 and will jointly study during the year a possible continuation of the mission in 2024 and beyond...

Happy anniversary SARAL and all our wishes for good health...

Further information:

Missions: Saral

2022 summer extreme events: Floods in Pakistan

Wed, 14 Sep 2022 08:04:48 +0000

A very hot spring, with temperatures reaching 51Â°C may have worsened the monsoon rains, since hot air can hold more water vapor. These temperatures have most probably led also to the observed increase in mountain glacier melting. Moreover, monsoon was early (June) and heavy this year, with precipitations three times higher than usual, or even more in some regions, falling on already soaked soils after a time.

The Indus, as well as some of its major tributaries, are monitored operationally by altimeters. At some points of their course the data are available continuously since 2008 : some of those show also the 2010 levels, which led to extreme floods inundating one-fifth of the country. The August data at 320, 949 and 1356 km (figures) from the Indus mouth show clearly higher level than the latest monsoon seasons. (see all Hydroweb altimetric virtual stations on the Indus river). Some tributaries, like the Sutlej and the Chenab show this, too

Altimetry monitoring does not constitute an early-warning system in itself, but could help in building such a system by providing data for modelling of the future flow downstream of the measurements.
Swot will provide data over more rivers, enabling to better understand such phenomena for a better modelling of those monsoon floods, in average as well as in extreme years.

SARAL, already 9 years old!

Wed, 23 Feb 2022 14:29:45 +0000

Who would have believed it! Launched in 2013 for a nominal lifetime of 5 years, after inertia wheel failures that forced to stop station keeping maneuvers (drifting orbit since July 2016), mispointing anomalies in February and March 2019 due to the degradation of the stellar sensors, SARAL is still in orbit with a global availability of the system (onboard + ground) of 99.68% over the year 2021.

This Ka-band world premiere (precursor to the future SWOT mission) is acclaimed by the scientific and operational community and is the result of an outstanding CNES/ISRO/EUMETSAT cooperation.

Developed in cooperation between ISRO and CNES, the Saral (Satellite with ARgos and ALtika) satellite carries AltiKa, a Ka-band altimeter (35 GHz), a radiometer and a Doris instrument. The use of the Ka-band frequency allows a better observation of ice, rain, coastal areas, land (rivers, lakes, etc.), and wave heights.

Initially planned on the same ground tracks as the ERS and Envisat satellites, Saral provides long-term continuity of observations and becomes an essential part of the altimetry satellite constellation.

Saral/AltiKa also provides the first demonstration of Ka-band altimeter capabilities for high-resolution along-track applications, including coastal and inland water applications, which will be developed for the future Swot mission.

Like its little brother Jason-3, which just celebrated its 6th birthday (Jason 3, already 6 years old!), it contributes to the CNES altimetry fleet, which allows, among other things, to follow the evolution of the oceans, but also contributes to the IPCC (Intergovernmental Panel on Climate Change) reports with its very accurate measurements.

Long life to Saral, thanks to all the teams who still allow this great adventure.

HAPPY BIRTHDAY SARAL !

Tue, 25 Feb 2020 14:24:57 +0000

On February 25th, SARAL celebrates seven years in orbit. It continues a major contribution to Ocean...

[SARAL/Altika] Data quality : back to normal

Fri, 26 Apr 2019 14:52:47 +0000

Dear SARAL/Altika users,

We are pleased to inform you that the quality of data is almost back to normal. Indeed, ISRO teams have improved the pointing stability thanks to new operational procedures. Since April 19th 2019, the availability and the quality of data measurements are better (small time to time limited effects may anyway occur). Therefore, before using the data, Users are still invited to remove any ocean data with âoff_nadir_angle_wfâ over 0.09 degÂ²)

Release of Jason-3 and Saral/Altika GDR annual validation reports 2018

Tue, 23 Apr 2019 09:05:20 +0000

The executive summaries give the essential results of the validation: Jason-3 and Saral/Altika. The annual reports describe the complete and detailed analysis: Jason-3 and Saral/Altika. Find here more information about the Calibration and Validation (CalVal) activities.

[Saral/AltiKa] Data information

Fri, 19 Apr 2019 08:26:00 +0000

Dear SARAL/Altika users,

Please take note of the disclaimer below :

SARAL/AltiKa satellite encounters since 3rd of February 2019 some issues affecting the nadir pointing accuracy. ISRO Operational Team in charge of the platform is doing many efforts to fix the issues and to recover a nominal mission as soon as possible.

The availability and the quality of data measurements is degraded from time to time. Nevertheless, Cnes, EUMETSAT and ISRO have decided to continue the dissemination of the near real time and off-line products; Therefore, before using the data, Users are invited to remove any ocean data with âoff_nadir_angle_wfâ over 0.09 degÂ²; otherwise standard quality flags may be used.

GDR cycle 126 (31 December 2018-04 February 2019 is just released today. It covers the beginning of the degraded period and you are encouraged to read the associated Cal/Val report available on AVISO+. In brief, during this cycle mispointing is quite larger than usual from pass 962 (03/02/2019 06:21:18 ) due to this attitude deviation. Hence a higher percentage of rejected measurements (up to 80%) is observed starting at pass 962. The attitude deviation also explains the higher percentage of missing measurements Users are advised not to use data with off_nadir_angle > 0.09degÂ².

[Saral] A new phase with a drifting orbit

Wed, 29 Jun 2016 14:32:00 +0000

SARAL/AltiKa mission will enter in a new phase named âSARAL-DPâ. Indeed, from July 4th onwards, SARAL satellite will fly free of station keeping maneuvers; the repetitive ground track will be no more maintained and with the natural decay of the orbit, the ground track will drift. âSARAL-DPâ stands for SARAL Drifting Phase.

This decision - endorsed by CNES and ISRO management - is due to the technical issues we have encountered on the reaction wheels since March 2015 and was proposed considering 2 key drivers:

fine station keeping maneuvers with thrusters only is very difficult to achieve,
there are new science perspectives emerging with drifting orbits on mean sea surface (MSS), geodesy/ bathymetry and other applications.

and implements two recommendations made by the Science Team in 2015 OSTST meeting which are recalled hereafter :

RECOMMEND the not-maintained (drifting) orbit for MSS/Gravity/Bathymetry.
RECOMMEND this phase to start as soon as possible (awaiting 3 years project meeting in early 2016)

Altimetry payload will be operated nominally on the drifting orbit; data processing is unchanged as well as data latency. Even no more linked to the ground track, we keep a âcycleâ duration of 35 days with 1002 passes (sub cycle ~ 16 days); cycle number will jump to #100 and OGDR, IGDR and GDR products will be produced as before. Concerning the SSALTO/Duacs products, no change is foreseen in the Near-Real-Time processing since the reaction wheels issue has been taken into account on June 30th, 2015 (i.e. no theoretical track projection but use of a gridded Mean Sea Surface (MSS) solution). Please note also that a semi-major axis increase (+1 km) will be performed just before to start the new phase. This maneuver will optimize the sampling for mesoscale applications for the next 2 years.

CNES and ISRO share the common objective to continue the SARAL mission as long as possible both for altimetry and ARGOS and we hope that the drifting phase will be as successful as the first 3 years on the repetitive orbit. Of course you will be informed on the progress of operational activities.

T. Guinle, J. Verron, P. Bonnefond, S. Arunan

Saral: three years in orbit!

Thu, 25 Feb 2016 11:21:00 +0000

Three years ago, the joint CNES/ISRO mission Saral was successfully launched. It embarks the first radar altimeter in Ka-band (AltiKa) providing new path for investigation in oceanography or for ice studies. These higher frequencies in Ka-band (35.75 GHz instead of 13.6 GHz for Ku-band and 5.3 GHz for C-band) offer higher spatial resolution, with more waveforms samples, so data closer between each other along the satellite ground track (~ every 180 m) and a reduced footprint. Its 35-day repeat orbit already followed by ERS-1 (1991-2000), ERS-2 (1995-2011) and Envisat (2002-2012) is a great opportunity to extend the repeat observations. Saral, with a high inclination orbit (at 98.55Â°) allows an optimal coverage in high latitudes, in the Arctic and the Antarctic. Its measurements are therefore naturally used for studying the cryosphere. By observing both in high latitudes, on different orbits, the combined use of the AltiKaâs Ka-band and the Ku-band of Cryosat-2 is ideally complementary.


Proportion of ice measurements from Saral/AltiKa waveforms classification from Oct.2014 (available by playing the animation). Waveform classification in function of the return echo shape enables to discriminate sea ice from ocean and allows to deduce sea ice extent . Credits CLS/CNES.

Further information:

Missions: Saral
Applications: Ice and Cryosphere: Sea ice extent seen by altimeters

Special issue in Marine Geodesy : The SARAL/AltiKa Altimetry Satellite Mission

Mon, 12 Oct 2015 09:01:00 +0000

The India-France Saral/AltiKa mission launched on February 2013 is the first Ka-band altimetric mission dedicated to oceanography. If the main mission objectives concern the observation of the ocean, the secondary objectives include ice sheet and inland waters monitoring.

This special issue provide some scientific examples that illustrate some main features of today's SARAL/AltiKa data with regard to standard altimetry: data availability, data accuracy at the mesoscales, data usefulness in costal area, over ice sheet, and for inland waters.

Further information:

Marine Geodesy (2015): Special Issue, The SARAL/AltiKa Satellite Altimetry Mission. Volume 38, Supplement 1, 2015 DOI:10.1080/01490419.2014.1000471. See the list of all articles here.
Mission: Saral/AltiKa

Saral: two years in orbit !

Wed, 25 Feb 2015 14:35:00 +0000

The SARAL/AltiKa satellite mission, an India-France ISRO-CNES joint project, celebrates its second...

Saral, first verification workshop : main conclusions

Thu, 05 Sep 2013 09:28:00 +0000

Please find hereafter the main conclusions of the first Saral Verification Workshop, which has been held on August 27-28-29th in Toulouse.

Synthesis

The performances of the payload instruments and the quality of the results has to be underlined, especially just a few months after the launch.

OGDR and IGDR products have been distributed to all Users from June 25th; GDR products are available to PIs since August 2^nd.
Some algorithms are still to be tuned: neural network used for radiometer data ground processing, Sea State Bias computation, altimeter wind speed and ICE2 retracking.
According to users presentations, the main message of this meeting is the easiness to use the data (thanks to the ground segment operationality and the expertise of the users). The level of quality achieved by the products in terms of accuracy, data latency and availability is such that the Saral/AltiKa data are now operationnaly integrated in several forecast systems (in Europe : CNES SALP, MÃ©tÃ©o France, Mercator, ECMWF, in India : ISRO/INCOIS, in Australia : CSIRO, in USA : NOAA, Navy).
The catchword for the Saral/AltiKa data could be "ready to use".

Disclaimers and foreseen evolutions

The GDR in V1are delivered to the PI since August 2nd, and their good quality has already been assessed. As a consequence, it has been decided to deliver the GDR_T ("T" for test) to all users (via AVISO ftp server) in the current version by September. Then the foreseen products evolutions V2 have been detailed by the project, and the level of priority has been discussed with the PIs. The V2 will be prepared by end 2013, to be available early 2014 and evaluated in frame of the second verification workshop (foreseen in April 2014). It could be relevant to hold the next Saral verification workshop around April 2014, possibly in India, mainly aiming at reviewing and assessing the quality of GDR data and discussing first scientific results. The 2014 OSTST will be in Germany and it is planned to have a joint dedicated Saral/AltiKa symposium. See further information on

foreseen evolutions. CNES Saral project team,

Saral: Synthesis of data quality after public release of the O/IGDRs

Mon, 15 Jul 2013 12:55:00 +0000

We are pleased to provide this short synthesis of the Saral IGDR-T products data quality assessment over oceans. CalVal analysis was performed on Cnes and CLS side during past months using classical tools like Cross-Overs and SLA analysis.
This memo provides early metrics computed on our side in order to ease the Saral use. This is based on the analysis of IGDR and OGDRs data dated from mid March 2013 to end of June. The Calval analysis will continue with the assessment of the first GDRs cycles and the routine monitoring of OGDRs and IGDRs products. We also like to mention that a patch has been prepared to correct for some anomalies and to account for the in-flight calibration data in the ground processing. The evolutions included in this patch are described in the pdf document. This patch has been installed on IGDRs products on July 11^th. It will be installed on OGDRs processing chains around July 17^th. Regarding the IGDRs products, the first product generated with this patch is :
SRL_IPN/R/S_2PTP004_0395_20130710_235618_20130711_004636.Cnes.nc This is mentioned in the Netcdf product in the global attribute âreferencesâ. This patch corresponds to the patch number 2 on the Level1B Scientific Library ; number 10 on the Level2 Scientific Library and number 9 on the Processing Pilot chain :
references = "L1 library=V3.1p1p2, L2 library=V4.2p1p6p9p10, Processing Pilot=V3-4-1p2p5p6p7p8p9" ; Former values were:
references = "L1 library=V3.1p1, L2 library=V4.2p1p6p9, Processing Pilot=V3-4-1p2p5p6p7p8" ; Amandine Guillot âSaral CalVal Responsible
Nicolas Picot - Saral Measurement System Engineer
On behalf of Cnes Saral project.

Saral : integration in Ssalto/Duacs with NRT Along-Track Sea Level Anomalies (SLA) and maps (MSLA)

Wed, 03 Jul 2013 09:35:00 +0000

Further information on the Ssalto/Duacs product changes and updates page.

Saral: data access open to all users for OGDRs and IGDRs products on June 20th, 2013

Tue, 18 Jun 2013 13:26:00 +0000

All participants have emphasized the extremely good results obtained with the SARAL mission and the very promising Ka band technology.
Considering the data quality, the project has decided to open the data access to all users for OGDRs and IGDRs products.
OGDRs and IGDRs product will be disseminated in version 'T' by June, 20th on CNES side on the AVISO ftp server.
A user release note is under finalization to provide detailed informations on the current data quality.

Saral also provides promising results over the Amazon river

Wed, 05 Jun 2013 06:38:00 +0000

The analysis of the Saral products over inland water is ongoing. Saral provides a new opportunity to monitor remotely the level of the major rivers, and comes at a perfect time to allow a continuous monitoring of rivers by carrying on the time series of data for inland waters initiated with ERS-2 in 1995, then continued with Envisat in 2002. These plots present the river level measured over an intersection of Saral ground tracks (pass number 063 and 478) with the Amazon (near the Amazon and Madeira confluence). The water levels are compared with the in situ measurement at IracÃ¨ma, available just 3 km upstream.

Water surface altitude (in meters) over the Amazon river (near the confluence of Amazon and Madeira rivers) along the Saral #063 and #478 ground tracks, between cycle 1 and cycle 3 (no data from pass #063 on cycle 1). Each curve represents the altitude in meters (Y-axis) along the ground track (X-axis represents the latitude) at a given cycle so each curve for a given pass is spacen from 35 days. Use the pass locator to visualize the ground tracks with Google Earth. CrÃ©ditsCnes/Legos/IRD, S.Calmant.

Water levels time series derived from ERS-2 (triangles) between 1995-2002, Envisat (squares) between 2002-2010 and Saral (circles) from 2013. The blue and cyan colors used for the water level derived from altimetry correspond to passes #063 and #478. Both tracks are separated of 14 days for a given cycle. The red line superimposed are derived from in situ measurements at the IracÃ¨ma gauge, located 3 km upstream. Missing blue squares between 2010 and 2012 correspond to an orbit change for Envisat beyond November 2010. The missing red line between 2011 and 2013 correspondonds to a lack of in situ measurements. Credits Cnes/Legos/IRD, S.Calmant.

The agreement between in situ water level records and Saral data is already very good. In the coming months, we will further increase the Saral data quality over inland water by using dedicated processing methods

Further information:

Applications: Hydrology, Rivers
News, 2012-06-05: Record flood in the Amazon basin
News, 2009-05-14 Exceptional flood on the Amazon river
Image of the month:
- April 2010: Drought and floods in the Amazon basin
- - Mar. 2007: Malaria and altimetry in the Amazon
  - Oct. 2001: The Amazon under close surveillance
Altimetry applications in videaos: Hydrology
Data use case in Radar Altimetry Tutorial : Temporal water surface height variations in enclosed areas: the Amazon Basin

Saral: first maps of Sea Level Anomalies

Fri, 24 May 2013 08:00:00 +0000

In orbit since a few months, Saral has just begun to collect data on its cycle 3 (2013/05/23). So far all results are very good and the Ka band altimeter, the radiometer, and the Precise Oorbit Determination payload (Doris and laser) provide very good results. The analysis of the level-2 data (O/IGDRs) quality is going smoothly over all surfaces, including land ice, inland water and obviously ocean.

The map below (left) displays the sea level anomalies measured by all Saral ground tracks (separated of 75 km at the Equator) over the last 35 days (duration of the Saral repetitive cycle). A same map is displayed for the Jason-2 mission which the ground track separation at the Equator is larger (315 km) during the same period (35 days for Jason-2 represent about 3.5 cycles). Both are very close, the integration of Saral mission into the SALP/Duacs multi-mission system will so be prepared in the coming weeks.


Maps of Sea Level Anomalies computed from IGDR (orbit MOE) for Saral in Ka-band (left) and for Jason-2 in Ku-band (right) between 2013/04/15 and 2013/05/20. This 35-days period represents one cycle for Saral and about 3.5 cycles for Jason-2. The anomalies are centered around 0.03m. Credits CLS/Cnes.

Saral/AltiKa provides the first promising results over Antarctica ice sheet

Mon, 13 May 2013 12:14:00 +0000

Antarctica and Greenland ice sheets are essential in the sea-level rise and climate understanding. Satellite altimetry is one of the powerful tools to study them. The Saral satellite, a joint-mission between Cnes and Isro, has been successfully launched the 25th of February 2013 and just ended its first cycle. AltiKa, the altimeter onboard has proven to be efficient and excellent results are yet observed over the Antarctica ice sheet as we see on the attached figures representing both the backscatter and the topography for the first time since Saral is in flight.

Maps of backscatter coefficient (in dB, left) and toppography (in m, right) over the Antarctica ice sheet. The measurements are provided by the AltiKa altimeter on the Saral satellite for its first cycle (cycle_001: 2013/03/14 - 2013/04/18). Credits Cnes/CLS, A.Michel

Saral succeeds amazingly in providing a continuity in good agreement with Envisat as the topography shows and supplies us with new informations through its innovative caracteristics, such as the backscatter. In the short term, we will analyse AltiKa data accurately in order to better explain the interaction between the snowpack and the radar wave, to expand the amount of observations we already have from ERS1/2 and Envisat and to measure height and volume variations. Thanks to Saral, Antarctica and Greenland ice sheets are surveyed, a crucial fact pointing out we will be enhancing the expertise in these both regions.

Further information:

all Aviso news about Saral since its launch on 2013/02/25
Missions: Saral
Image of the month:
- June 2012: Antarctica thinning seen by Envisat
- Oct. 2010: Envisat measures up Antarctica
- Nov. 2004: A dual-frequency view of Antarctica
Applications: Ice sheets