Delining and the Cleaning process

One item I forgot to mention last night was the effects of lines/delining on
PCA subtraction. These should be the primary effects on the final map for all
epochs except 2010, in which case the primary effect SHOULD be to reduce
substantial noise.


In the examples below, there are PSDs of whole timestreams (left) and
example timestreams from single scans (right). The first thing to note is that
the delined timestreams still have correlated components in the line region,
but they are suppressed - their amplitudes, and therefore their sort order in
the PCA removal scheme, are changed. Since PCA cleaning is by its nature adaptive
(the number of components remains fixed, but the order changes), these effects
can be significant and dangerous. If the line noise is more correlated, a PCA
component will be dedicated to removing it instead of atmospheric signal.


Below are examples from l089 (epoch 0709) first. These have less correlated
line noise and are more typical of BGPS observations. The first PCA component,
the average, does not change much with PCA cleaning. However it is clear that
the second component changes substantially, from large-amplitude high-frequency
noise to small-amplitude variations that are very likely to describe
atmosphere.

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Example 1 - Zeroing out the lines:
Example 2 - Fitting and removing the lines:
Example 3 - Suppressing the lines with a non-fitted Gaussian:
The next examples are from December 2010 observations of Uranus. In this case, the correlated noise component is clearly dominant.
Zeroing lines:
Fitted lines:
Non-fitted gaussian suppression:
Finally, these two are demonstrations of what you might expect to see for a purely noiseless images of a planet (it was constructed from a PSF). PCA is first:
A single bolometer's timestream and PSD: