Mobile version

Laser telemetry

Laser telemetry has become the only space geodesy technique being at the same time, precise and absolute (exact distance measurement), continuously controllable on ground at the metrology level. This is due to its maintenance availability and its worldwide development. See the campaigns using ultra-mobile laser station (in french) ( FTLRS ).

  • Jason -1, the first satellite from the Jason oceanography family developed by Cnes and Nasa, is the outcome of a sea state survey concept initiated several years ago with Topex / Poseidon ( T/P ). On a geodetic point of view, the expected variations of the mean sea level are about a millimeter per year; so long uninterrupted time series of oceanographic data are essential. In the same way, we expect, thanks to laser telemetry as well as other space techniques, a better knowledge of the orbit of altimetric satellites, and the determination of the Earth's crust displacements, including vertical motion, with the same precision level.
  • The calibration of the on board altimeter radar is a key point for the validation of an altimetry mission [Ménard & al., 1994]. The time drift of an unexpected bias, due to electronic aging, is even more worrying for the analysis of secular mean sea level variations. The T/P mission experience has shown that is absolutely necessary to control this calibration at mm/year level over several years [Bonnefond et al., 2003a].
  • Another major limitation of the altimetric system is related to the orbit determination quality, which is required to achieve the proper accuracy of the sea level determination in a geocentric reference frame. This because altimetry measurement is performed from a spacecraft.

This implies the use of global satellite tracking systems such Doris and / or GPS and outstanding numerical orbit processing methods in order to reach an orbit determination accuracy compatible with the centimeter level precision of data [Nouel & al., 1994]. Laser telemetry is the only absolute technique (the Doppler technique provides information on time varying distances) providing the essential scale factor with a constant quality even on intercontinental distances [Bonnefond & al., 1999]. The troposphere effects (moisture effects) are also much smaller than with radio-electric techniques.

In the frame of space oceanography like for space geodesy, it is a prime necessity to develop laser instruments with much more stable biases typically less than 5 mm over several years. Grasse is one of the 3 sites in Europe, reaching a sufficient accuracy for such measurements. It's a very interesting site that covers a large geographic area in the western Mediterranean Sea.

The economic interest to survey this area is evident, from a scientific point of view. The western Mediterranean Sea has become a unique calibration and experimentation zone in the world of the 90's beginning, due to its low oceanic variability as a quasi-closed Sea and its economical abilities. That's why we proposed to develop a double calibration site, in Grasse (Calern Plateau) and in Corsica (Aspretto naval base and Cap de Senetosa in the south).

EnglishFrançaisEspañol
Rss feedsContactSitemapPartnersFAQGlossaryLexiconMobile
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

The new 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!