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At line 1 added 3 lines
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
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!Overlap of SAA and XTW (night)
There is often a substantial overlap between SAA and XTW (X-ray / EUV night) events around the orbit. However, the phase of EUV night does not change phase in the orbit, whereas that of the SAA does. Therefore nights and SAA passes sometimes coincide (with night being the longer event), and sometimes do not overlap so much. However, there is almost always some overlap. The exception to this is during the Golden Period, during which there are no SAA periods, but EUV nights continue to occur once per orbit.
!Overlap of SAA and Eclipse
There is often a substantial overlap between SAA and XTW (X-ray / EUV night) events around the orbit. However, the phase of EUV night does not change phase in the orbit in the way that that of the SAA does. Therefore nights and SAA passes sometimes coincide (with night being the longer event), and sometimes do not overlap so much. However, there is almost always some overlap. The exception to this is during the ''Golden Period'', during which there are no SAA events, but EUV nights continue to occur once per orbit.
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As a result, a some parts of the day, the less-than-complete overlap of SAA and night means that the clear window for observing in such orbits can be shorter. 2009 was the first year for which XTW calcluations were made for Hinode. So taking into account the buffers (summarised below) around orbital events, I recalculated the distribution of clear observing windows from the middle of eclipse season in 2009.
As a result, at many times of day, the less-than-complete overlap of SAA and night means that the clear window for observing in such orbits can be shorter. From 2009, EUV Night event were calculated for Hinode's orbit. So taking into account the buffers (summarised below) around orbital events, we can recalculate the distribution of clear observing windows from the middle of eclipse season in 2009.
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You can see from the histogram below that there are two distinct populations (ignore the very short windows at the far left: these are due to vanishingly small SAA events that occur shortly after larger events).
The histograms below show a distribution of these windows' length over a three-day sample. There are two distinct populations (ignore the very short windows at the far left: these are due to vanishingly small SAA events that occur shortly after larger events).
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| {{{XTW_ENTRY}}} | 2 minutes after
| {{{XTW_EXIT}}} | 2 minutes after
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__Please note__ that as of late 2008, the planning tool has a "SHOW OBEV WINDOWS" feature that factors in these buffers (with the exception of the XTW buffer, which we hope will be implemented shortly (2010/05/11).
__Please note__ that as of late 2008, the planning tool has a "SHOW OBEV WINDOWS" feature that factors in these buffers. This feature is shown in the screenshot below
[{Image src='attach/SbandObservingInfo/OBEV%20Windows.png'}]