Mobile version

The Jason-1's orbit

Jason-1's orbit is identical to that of Topex/Poseidon. It is optimized to study large-scale ocean variability and to provide coverage of 90% of the world's oceans over a ten-day cycle.

Jason-1 before February 2009 (red) and Topex/Poseidon (green) ground tracks on its new orbit on September 20, 2002. Download Google Earth files with <link fileadmin documents data tools visu_tpj1_tracks_ge_v3.kmz download>Jason-1 and <link fileadmin documents data tools visu_tp_interlaced_tracks_ge_v3.kmz download>Topex/Poseidon ground tracks or retreive all ground tracks here.

Choice of orbit

Jason-1's high altitude (1 336 kilometres) reduces interactions with the Earth's atmosphere and gravity field to a minimum, thus making orbit determination easier and more precise. The orbit inclination of 66 degrees North and South enables the satellite to cover most of the globe's unfrozen oceans. The orbit's repeat cycle is just under 10 days (9.9156 days to be precise, i.e. 10 days minus two hours) - in other words, the satellite passes over the same point on the Earth's surface (to within one kilometre) every ten days. This cycle is a trade-off between spatial and temporal resolution designed for the study of large-scale ocean variability. The fact that the orbit is prograde and not sun-synchronous also avoids aliasing of different tide components at the same frequency.

Furthermore, using the same orbit as Topex/Poseidon ensures better intercalibration and data continuity. The orbit is also designed to pass over dedicated ground calibration sites (Cap Senetosa in Corsica , the Harvest oil rig platform in California, USA,...).

Jason-1 has undergone an orbit change at the end of OSTM/Jason-2's calibration  phase in February 2009. From 2008 to 2016, Jason-2 is located on the former orbit of Topex / Poseidon (before 2002) and Jason-1 (before February 2009). The Jason-1's orbit is shifted midway between its original ground tracks (corresponding to those of Topex/Poseidon after 2002). Jason-1 and OSTM/Jason-2 also have a time lag of 5 days. Two cycles (260-261) of Jason-1 science data were lost during the transit to the new tandem orbit phasing (26 Jan to 15 Feb, 2009).

After having encountered an anomaly at the end of February 2012 and early in March 2012, Jason-1 was in Safe Hold Mode (see chronology of these events at the bottom of this page). Cnes and Nasa management, through the Joint Steering Group, have directed the Jason-1 Project to begin a series of maneuvers to reduce the orbit on a drifting geodetic orbit at 1324.0 km.


A satellite's orbit parameters tend to change over time as a result of atmospheric drag. In the long term, more or less periodic variations also occur due to instabilities in the Earth's gravity field, solar radiation pressure and other forces of smaller magnitude.

Orbit maoeuvres are performed every 40 to 200 days. Intervals between manoeuvres depend chiefly on solar flux and each manoeuvre lasts from 20 to 60 minutes. Wherever possible, they are performed at the end of the orbit cycle, and above solid earth, so that lost data acquisition time is reduced to a minimum.

Orbit parameters

Main characteristics new geodetic orbit (>April 2012)
Semi-major axis 7714.4278 km 7702.437 km
Eccentricity 0.000095 1.3 to 2.8 10-4
Inclination (non-sun-synchronous) 66.039° 66.042°
Auxiliary data    
Reference altitude (equatorial) 1 336 km 1324 km
Nodal period 6 745.72 seconds (112'42" or 1h52') 6730s (1h52'10'')
Repeat cycle 9.9156 days  
cycle 406 days
sub-cycles 3.9 - 10.9 - 47.5 - 179.5 days
Number of passes per cycle 254 280
Ground track separation at Equator 315 km  
Acute angle at Equator crossings 39.5°  
Longitude at Equator of pass 1 99.9242°  
Orbital velocity 7.2 km/s  
Ground scanning velocity 5.8 km/s  
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!