We commonly use the polynomial + secant filter to remove large scale atmosphere and airmass signal from our timestreams. Some of the SPT guys at McGill now use a fourier mode filter instead of a polynomial. Presented is how this filter would apply to APEX-SZ data.

Proceedure, all the Fourier modes up to the specified order are simultaneously fitted and removed from the timestream along with a first order polynomial and an airmass signal.

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The original Timestream

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Filtering to 5th order fourier modes.

The fourier mode filter is comparable to the polynomial + secant filter, for the low order case.

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*Filtering to higher orders.*

The airmass signal looks very similar to a 36th order fourier mode. Here, we filter up to this order (35th order + secant) to remove signal on scales larger than the airmass signal.

Here is the residual timestream

We also tried to remove a the first 36 orders and NOT the secant to see if we still need to fit the secant. The residual shows some large scale structre likely due to the airmass signal.

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*Maps*

-- JamesKennedy - 23 Jun 2009

test_wiki

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This topic: APEX_SZ > WebHome > A520 > 2009-06-23 Topic revision: r4 - 2009-06-26 - JamesKennedy

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