**AAS 200th meeting, Albuquerque, NM, June 2002**

*Session 4. Helioseismology and the Solar Interior*

Display, Monday, June 3, 2002, 9:20am-6:30pm, SW Exhibit Hall
[Previous] |
[Session 4] |
[Next]

## [4.09] Calculating the GONG and GONG+ leakage matrices -- latest improvements

*R. Howe, F. Hill (NSO)*

In helioseismology, time series for each spherical harmonic
are calculated by convolving the imaged data with spherical
harmonic masks. Because we image only a part of the solar
surface, each time series is contaminated by power from
neighbouring spherical harmonics. This contamination can be
quantified by calculating the so-called `leakage matrix'.
Many data analysis techniques depend on a good estimate of
this matrix. Motivated by the new GONG+ data, we have
improved the calculation of the leakage matrices for both
GONG+ and GONG Classic images. Specifically, we have
improved the grids used for calculating the apodization;
incorporated an empirical projection function; and allowed
for the different pixel aspect ratios and image apodization
functions of GONG+ and GONG Classic data. The effect of
these improvements will be shown through several comparisons
between the calculated matrices and the observed power
spectra.

NSO is operated by AURA, Inc. under a co-operative agreement
with NSF.

[Previous] |
[Session 4] |
[Next]

Bulletin of the American Astronomical Society, **34**

© 2002. The American Astronomical Soceity.