mallorca, spain, 2009 march 31 – april 1
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EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
Mallorca, Spain, 2009 March 31 – April 1Mallorca, Spain, 2009 March 31 – April 1
EPIC Calibration & Operations Meeting
Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
“Noise events”: events which are not caused by photons,
mainly evident at low Pulse Height Amplitudes (PHAs)
“Noise events”: events which are not caused by photons,
mainly evident at low Pulse Height Amplitudes (PHAs)
50.7 ks closed FF quadrant 0, rev 059
50.7 ks closed FF quadrant 0, rev 059
PHA [adu]
nu
mb
er
of
ev
ents
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
raw_y
20-65 adu
nois
e
Previous attempts to suppress the noise events were based on their spatial/spectral characteristics ( epreject )
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
Previous attempts to suppress the noise events were based on their spatial/spectral characteristics ( epreject )
without noise suppression (epreject)
Vela SNR, FF, rev 534, 38.8 ks
with noise suppression (epreject)
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
However, the spatial/spectral characteristics of noise events turned out to be not sufficiently stable in time to achieve in all cases a satisfactory noise suppression with the concept of a temporally constant noise model.
20 50adu
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
However, the spatial/spectral characteristics of noise events turned out to be not sufficiently stable in time to achieve in all cases a satisfactory noise suppression with the concept of a temporally constant noise model.
20 50adu
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
An improved approach would be to scale the temporally constant noise model individually to each observation, by using information derived from the particular observation.
This approach is under investigation, but it is fairly sophisticated, and it is not clear yet whether it will be reliable enough for general usage.
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
An improved approach would be to scale the temporally constant noise model individually to each observation, by using information derived from the particular observation.
This approach is under investigation, but it is fairly sophisticated, and it is not clear yet whether it will be reliable enough for general usage.
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
An improved approach would be to scale the temporally constant noise model individually to each observation, by using information derived from the particular observation.
This approach is under investigation, but it is fairly sophisticated, and it is not clear yet whether it will be reliable enough for general usage.
In the process of investigating the temporal properties of noise events, it was found that individual frames are considerably noisier than the average. If these frames are rejected, the signal to noise ratio can be improved at low energies.
This method is so straightforward that it can be easily implemented.
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
FF closedclosed, rev 0462, 23 ks, CCD 1
Number of frames containing NEVT_FRM events within 20..30 adu
NEVT_FRM > 7
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
FF closedclosed, rev 0462, 23 ks, CCD 1
NEVT_FRM > 5
Number of frames containing NEVT_FRM events within 20..30 adu
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
FF closed
closed, rev 0462, 23 ks, CCD 1 – 6
Number of frames containing NEVT_FRM events within 20..30 adu
CCD 1
CCD 2
CCD 3
CCD 4
CCD 5
CCD 6
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
Number of frames containing NEVT_FRM events within 20..30 adu
FF closed
closed, rev 0462, 23 ks, CCD 7 - 12
CCD 7
CCD 8
CCD 9
CCD 10
CCD 11
CCD 12
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
EPIC-pn noise (LW), rev 0790, 61 ks closedclosed, after offset corrections, all events
20 adu 21 adu 22 adu 23 adu 24 adu
25 adu 26 adu 27 adu 28 adu 29 adu
30 adu 31-35 adu 36-40 adu 41-45 adu 46-50 adu
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
rev 462
23 ks closedclosed
FF
no offset corrections
all events
30-50 adu
raw dataraw data
At 30-50 adu, “noise” creates mainly undefined patterns:
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
rev 462
23 ks closedclosed
FF
no offset corrections
non-singles
processed dataprocessed data
At 30-50 adu, “noise” creates mainly undefined patterns:
30-50 adu
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
rev 462
23 ks closedclosed
FF
no offset corrections
singles
processed dataprocessed data
At 30-50 adu, “noise” creates mainly undefined patterns:
30-50 adu
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
singles, 20 – 30 adu, all frames
LW thick, SNR 1E0102, rev 0803, 30 ks
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
total number of frames
(reconstructed) number of frames with no event below 31 adu per CCD
number of frames with 2 events below 31 adu per CCD
SNR 1E 0102, rev 803, LW, thick, 30 ks
number of frames with more than 9 events below 31 adu per CCD
number of frames with 1 event below 31 adu per CCD
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
Number of frames containing NEVT_FRM events within 20..30 adu
CCD 1
CCD 2
CCD 3
CCD 4
CCD 5
CCD 6
LW thick, SNR 1E0102, rev 0803, 30 ks, CCD 1 – 6
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
Number of frames containing NEVT_FRM events within 20..30 adu
CCD 7
CCD 8
CCD 9
CCD 10
CCD 11
CCD 12
LW thick, SNR 1E0102, rev 0803, 30 ks, CCD 7 – 12
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
LW thick, SNR 1E0102, rev 0803, 30 ks
image image mask image mask applied
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
LW thick, SNR 1E0102, rev 0803, 30 ks
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
original image cleaned image removed noise
= +
LW thick, SNR 1E0102, rev 0803, 30 ks
20 – 30 adu, all events
source practically invisible in removed events
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
LW thick, SNR 1E0102, rev 0803, 30 ks, CCD 4
before / after
removal of noisy frames
20 – 30 adu
all events
same intensity cuts
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
singles, 0.3-3.0 keV
mask for source regions to be avoided for noise
determination
source region mask
In order to determine the noise properties, some areas have to be ignored:
SNR 1E 0102, rev 803, LW, thick, 30 ks
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
final mask, excluding source regions and noisy pixelsnoisy pixel mask
SNR 1E 0102, rev 803, LW, thick, 30 ks
In order to determine the noise properties, some areas have to be ignored:
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
unfiltered data singles, 24 adu after noisy frame removal
SNR 1E 0102, rev 803, LW, thick, 30 ks
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
= +
singles, 20 – 30 adu, frames with more
than 2 events below 31 adu per frame and
CCD
singles, 20 – 30 adu, frames with 1 or 2
events below 31 adu per frame and CCD
singles, 20 – 30 adu, all frames
LW thick, SNR 1E0102, rev 0803, 30 ks
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
unfiltered data after noisy frame removal
singles, 120-130 eV
LW thick, SNR 1E0102, rev 0803, 30 ks
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
epreject
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
At which stage should “noisy frames” be identified At which stage should “noisy frames” be identified
and removed ?and removed ?
raw data recombined event list
raw data:
events not yet recombined better discrimination of noisy frames
standard processing does not allow removal of frames before epevents
major changes of SAS may be required
time-consuming tasks (epevents..) need to be repeated in case of iterations
screening improves signal/noise ratio only at low energies and would cause
unnecessary loss of exposure at higher energies
recombined events list:
quick and easy application: optional task at the end of the pipeline processing
number of events within PHA range not available anymore (patterns)
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
Solution:Solution:
separate the determination of noisy frames from their removal !
only one change required for pipeline processing: keep the “rawevents.dat” files;
they contain
• information about the raw events (no recombination yet performed)
• time tags: unique identification of frames possible, also in the final event list !
noise suppression is based on the removal of complete frames
no need for repeating the pattern recognition and energy correction,
only exposure needs to be updated if frames are removed
one additional task (e.g. “epnoise”) would be sufficient:
- filter a copy of the final event list according to criteria derived from the “rawevents.dat” files and other input: masks, adu range and cutoff criteria (e.g. discrepancy between observed distribution and poissonian fit)
- update the exposure extensions
quick iterations possible
output from source detection could be used for creating masks
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
optional image mask
upper ADU threshold
“epnoise”
raweventsxx.datraweventsxx.dat
“Final” cleaned event file
possible implementation:
EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression K. Dennerl, 2009 March K. Dennerl, 2009 March 3131
Mallorca, Spain, 2009 March 31 – April 1Mallorca, Spain, 2009 March 31 – April 1
EPIC Calibration & Operations Meeting
Update of EPIC pn noise suppressionUpdate of EPIC pn noise suppression
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