Possible improvement of the SAA JASON-1 corrective model by the use of the maps of energetic particles obtained by the dosimeter CARMEN onboard of JASON-2



Jean-Michel Lemoine (CNES, France)

Event: 2014 IDS Workshop

Session: Precise orbit modeling and Precise Orbit Determination

Presentation type: Type Oral

The sensitivity of the ultra stable oscillator (USO) of DORIS/JASON-1 to the high energy protons trapped in the Van Allen belts was first pointed out by Willis. This sensitivity causes a fluctuation of the frequency when the satellite crosses the area of the South-Atlantic Anomaly (SAA). The principal consequence is the impossibility of using the measurements of the DORIS beacons located in the SAA for cm-precision positioning since the real frequency of the on-board oscillator is varying rapidly in that area.
To correct for this sensitivity to the effects of solar radiation, a model of frequency evolution of the USO was designed and validated by CNES. This model of frequency correction makes a significant improvement in the orbit adjustment. It takes into account the geographical characteristics of the SAA region (1x1 degree SAA grid) as well as parameters of the USO's response to this external stimulation: an amplitude, a relaxation time-constant and a memory effect of the SAA disturbance.
The satellite JASON-2 carries the dosimeter CARMEN instrument. The purpose here is to take the advantage of this instrument to improve our SAA corrective model by using the maps of energetic particles CARMEN. First, a correlation study between the SAA DORIS grid and the CARMEN maps has been done to determine the dosimeter map which has the best agreement. Then, this map is used to calculate the others parameters of the model. The new model will be used to correct the DORIS data and we will look the impact on the orbit and on the positioning.

Oral presentation show times:

RoomStart DateEnd Date
Blue salon Tue, Oct 28 2014,15:00 Tue, Oct 28 2014,15:15