Mobile version

Focusing on small water bodies

Image of the Month - March 2019

A pond as seen by optical satellites (left); right, the fully-focused SAR measurements of it (note that the repetitions are due to the emission/reception pattern of the altimeter which leads to secondary images; Jason-CS/Sentinel-6 interleaved emission/reception pattern should remove those) (Credits CLS)

The SAR-altimetry mode (or Delay-Doppler altimetry) is implemented on Cryosat, the Sentinel-3A & B and in the future on Jason-CS/Sentinel-6 and the Sentinel-3 C& D. This mode enable to get higher along-track resolution at a better accuracy (see Technique > Altimetry > SAR altimetry), and is more and more used, in particular for inland water applications. 

The currently SAR altimeters processing uses coherent altimeter radar echoes over a limited time (approximately 3.52 ms). However, the entire illumination time of the surface (almost 2.5 s) can be used for the synthetic aperture processing since it stays coherent for that entire period. This, called  “Fully-focused SAR processing” thus achieves better along-track resolution, eventually reaching the theoretical limit of approximately 50 cm for current SAR altimeters (which is half the diameter of the antenna). 

With such a finer resolution, very small water bodies crossed by the satellite ground track can be accurately observed and measured. The fully-focused SAR processing can be applied to the three currently flying SAR altimeters (CryoSat-2, Sentinel-3A & B) and also to the upcoming SAR altimeters (Sentinel-3C & D and Jason-CS/Sentinel-6). Jason-CS/Sentinel-6 should show even greater performance thanks to the interleaved mode planned on this mission, which will emit and receive the altimeter echoes alternatively, instead of emitting 256 times then going on receiving mode for a period, and so on (this latter mode have the drawback of generating "ghost" measurements in fully-focused SAR processing, duplicating the results further along the track if not taken into account)

Those altimeters having different ground tracks, a huge dataset of water levels will be studied for itself, and will also be used in combination/comparison with Swot data when the satellite will be flying. Studies on ice, coasts and even open ocean are also ongoing.

See also:

References:

EnglishFrançais
Rss feedsContactPartnersFAQLexiconLegal noticePersonal Data Protection PolicyMobile
You must enable cookies in your browser preferences to save the modifications
You are using an older version of Internet Explorer, please update to take full advantage of Aviso+ features

Customize the home page

View all widgets
Reduce display
Public profile
User profile

Select/Deselect widgets

Discover AVISO+

Customizable home, reading tools, products search guide, etc.. Discover step by step the features of the new site AVISO+.

Customizable homepage

This home page is composed of blocks called "widgets".

Rearrange the blocks with a "Click & Drop".

Hide a widget with the cross at the top right. Reset or add a widget with the "wrench" icon. The "User" and "Public" profiles offer a predefined organization.

All the modifications are automatically saved as cookies on your machine so as to enable you to have your own specific AVISO+.

Reading tools

Ease your reading by choosing the page background colour (black/white) and/or by modifying the font size.

Browsing menu and breadcrum trail

To ease your browsing through AVISO+, you can use at any time the main banner items with the interactive submenus or use the browsing menu on the left side of the screen (it is open by default). For more readiness of the page contents, you can fold and unfold the browsing menu by clicking on the tab. At any time you can know where you are thanks to the browsing menu or the breadcrum at the top of the page.

Products search guide

The first submenu of the "Data" banner item leads you to a new search form enabling you to find quickier the product that suits your needs. The list of results is updated according to your selection criteria.

AVISO+ Multimedia

The first submenu of the "Multimedia" banner item leads you to AVISO+ collections of images and videos linked to altimetry and its applications. Have a nice visit!