The South Atlantic Anomaly is a phenomena that takes place in the ionosphere, at the magnetic equator, where the Van Allen radiation belt (particles emited by the Sun and trapped by the Earth magnetic field into a belt following the magnetic equator) is closest to Earth. This "anomaly" causes among other things errors on the measurement of the Doris instrument onboard Jason-1, since the orbit of this satellite is especially exposed. Using the Doris instrument onboard the other satellites, it is possible to study and measure this phenomena, in order to better correct from it.

The very high accuracy demanded to location by altimetry requests that every phenomena that can perturbate the instruments is taken into account. The T2L2 instrument that will be onboard Jason-2 should enable to measure this South Atlantic Anomaly, and its impact on the instruments.

See also:

• Doris

Websites on this subject:

• South Atlantic Anomaly (Wikipedia)
• T2L2 (Cnes Scientific mission site)

References:

• Lemoine, J.M., H. Capdeville, A corrective model for Jason-1 Doris Doppler data in relation to the South Atlantic Anomaly, J. Geod., 80, 507-523, 2006