ALLEVIATION OF THE BACKUS EFFECT IN GEOMAGNETIC-FIELD MODELING

Satellite magnetometry is plagued by the Backus effect which renders m aps of the magnetic field derived from measurements of the total field intensity unreliable, especially near the geomagnetic equator. The on ly remedy is to use oriented, vector component data in addition to sca lar intensity data, but this requires either accurate determination of the satellite attitude or the use of data from permanent magnetic obs ervatories. The former adds considerably to the cost and complexity of satellite magnetometry; the latter suffers in practice from the poor geographical distribution of magnetic observatories. Here we re-examin e the problem of attitude determination, and ask how well the attitude needs to be determined to alleviate the Backus effect. We show that t he use of a more complete model of the errors in satellite vector comp onent data allows the requirements on attitude determination to be rel axed significantly, so that lower-cost means of obtaining attitude det ermination, such as GPS, can be employed.