The Sentinel-3 orbit is almost the same orbit as ENVISAT, allowing continuation of the ERS/ENVISAT and CRYOSAT time series.

The main parameters for the reference orbit are:

• type: near-polar frozen sun-synchronous
• inclination: 98.65°
• mean local solar time at descending node: 10:00 h
• repeat cycle: 27 days (14 + 7 / 27 orbits per day) 
• reference altitude: 814.5 km
• cycle length: 385 orbits
• ground track separation at the Equator: 104 km with Sentinel-3A, and 52 km with Sentinel-3A and Sentinel-3B.

Figure 1: Example of Sentinel-3 Single Orbit Ground Track (Credit: isardSAT)

The mean local solar time at descending node at 10:00h still provides complementary local time coverage while optimising the viewing conditions for the imager and allowing continuity with the existing ERS and ENVISAT climate products.

Having a high inclination provides important extra information about sea level variations in high latitudes not properly sampled before by a high precision altimeter.