NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
MAGSAT scalar anomaly map of South AmericaA scalar magnetic anomaly map was prepared for South America and adjacent marine areas directly from original MAGSAT orbits. The preparation of the map poses special problems, notably in the separation of external field and crustal anomalies, and in the reduction of data to a common altitude. External fields are manifested in a long-wavelength ring current effect, a medium-wavelength equatorial electrojet, and short-wavelength noise. The noise is reduced by selecting profiles from quiet periods, and since the electrojet is confined primarily to dusk profiles, its effect is minimized by drawing the data set from dawn profiles only. The ring current is corrected through the use of the standard ring current equation, augmented by further filtering with a Butterworth bandpass filter. Under the assumption that the time-variant ring current is best removed when a replication of redundant profiles is achieved, a test set of 25 groups of 3 nearly coincident orbits per group is set up for filtering with a range of long-wavelength cutoffs to determine which cutoff best replicates the residual profiles. Altitude differences are then normalized by an inversion of the profile data onto a grid of equivalent point dipoles, and recalculated at an altitude of 350 km. The resulting map, when compared to the 2 deg averaged map, shows more coherent anomalies, with notable differences in the region affected by the electrojet.
Document ID
19850023273
Acquisition Source
Legacy CDMS
Document Type
Other
Authors
Ridgway, J. R.
(Purdue Univ. West Lafayette, IN, United States)
Hinze, W. J.
(Purdue Univ. West Lafayette, IN, United States)
Braile, L. W.
(Purdue Univ. West Lafayette, IN, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1985
Publication Information
Publication: Improving the Geol. Interpretation of Magnetic and Gravity Satellite Anomalies
Subject Category
Earth Resources And Remote Sensing
Accession Number
85N31586
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

There are no available downloads for this record.
No Preview Available