This page (revision-43) was last changed on 18-Apr-2021 19:03 by JianSun

This page was created on 24-Apr-2008 18:38 by JianSun

Only authorized users are allowed to rename pages.

Only authorized users are allowed to delete pages.

Page revision history

Version Date Modified Size Author Changes ... Change note
43 18-Apr-2021 19:03 5 KB JianSun to previous
42 02-May-2008 17:30 5 KB JianSun to previous | to last
41 01-May-2008 03:17 5 KB David R Williams to previous | to last

Page References

Incoming links Outgoing links
CompressionFactorStudy
CompressionFactorStudy

Version management

Difference between version and

At line 1 changed one line
The compression rate of on board EIS data may vary depending on a few factors such as the observing target (QS, AR, CH, etc), slit/slot selection, exposures, etc.
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
The __compression factor__ of on board EIS data may vary depending on a few factors such as the observing target (QS, AR, CH, etc), slit/slot selection, exposures, etc.
At line 3 changed one line
The purpose of this study is trying to investigate how different compression schemes effect EIS data volume on board and work out a better estimation of compression rate for compression scheme (eg. DPCM, JPEG98, JPEG95, etc.)
The purpose of this study is trying to investigate how different compression schemes effect EIS data volume on board (MDP) and work out a better estimation of compression factor for compression scheme (eg. DPCM, JPEG98, JPEG95, etc.)
At line 7 changed one line
1. to get actual data volume from MDP status information: the inclined curve means data packets from EIS on MDP, the vertical curve means data packets dumped to ground station. So in general, known a raster's start and end time can calculate actual data volume, and then compare it with the designed data volume of this raster to get data compression rate.
1. to get actual data volume from MDP status information: the inclined curve means data packets from EIS on MDP increasing, the vertical curve means data packets dumped to ground station. So in general, knowing a raster's start and end time one can fitstly calculate actual data volume in that duration, and then compare it with the designed data volume in raster's definition, to get data compression factor.
At line 13 changed one line
3. prepare plots based on various factor combinations: compression rate vs. slit/slot, rate vs. target, rate vs. exposures
3. prepare plots based on various factor combinations: compression factor vs. slit/slot, factor vs. target, factor vs. exposures
At line 17 added one line
\\
At line 16 changed one line
!!Some preliminary results (plots):\\
!!Some preliminary results (plots):
At line 21 added one line
\\
At line 19 removed one line
(The investigation here is for dates between %%(color:#cc0000;)2007-Sep-15 and 2007-Dec-15%%, as EIS is operationally stable over this duration. The other data sets is in %%(color:#cc0000;)2008-Mar%% (for JPEG85), and %%(color:#cc0000;)2006-Dec%% (for JPEG75))
At line 24 added 3 lines
''The investigation here is for date sets obtained mainly between %%(color:#cc0000;)2007-Sep-15 and 2007-Dec-15%%, as EIS operations were most efficient and stable over this duration. The other data sets inluded here are: %%(color:#cc0000;)2008-Mar%% (for JPEG85), %%(color:#cc0000;)2006-Dec%% (for JPEG75), %%(color:#cc0000;)2007-Jan to 2007-Apr%%, and %%(color:#cc0000;)2008-Feb%%.
''
At line 47 added one line
\\
At line 43 changed one line
!Table is here!
The __average values__ of compression factor for each scheme are listed in following %%(color:#c00;)Sortable Table%% (although only a single number can't show the compression factor varation over a large dataset).
At line 45 changed one line
There is difference between the number shown here and other previous results, for example, Hara'san work:
%%sortable
|| Scheme || Total || QS || AR || CH || 1" || 2" || 40" || 266" || 10s || 15s || 20s || 30s || 60S
|DPCM |2.52|2.80|2.80|2.70|3.0|2.96|3.63|2.49|3.08|3.01|2.5|2.6|2.42
|DPCM | | | | | | | |QS|3.14|2.94|2.91|2.52|2.32
|DPCM | | | | | | | |AR|2.96|3.0|2.35|2.5|2.14
|DPCM | | | | | | | |CH| |3.05|2.52|2.88|2.47
|JPEG98|2.56|2.67|2.46|3.44|2.80|2.36|2.56| |3.21|2.54| |2.4|
|JPEG98| | | | | | | |QS|3.32|2.60| |2.43|
|JPEG98| | | | | | | |AR|3.17|2.42| |2.49|
|JPEG98| | | | | | | |CH|3.6| | | |
|JPEG95|6.25|6.12|6.38| |6.23|6.3| | |5.86| |4.60| |
|JPEG95| | | | | | | |AR|5.82| |4.08| |
|JPEG90|8.11|7.39|8.6|8.4|4.85| |5.04|8.34| | | |5.04|
|JPEG90| | | | | | | |QS| | | |3.87|
|JPEG90| | | | | | | |AR| | | |3.81|
|JPEG85|5.56|5.58|4.92|6.21| | |5.56| | | | | |
|JPEG75|11.39| | | | | | |11.39|11.39| | | |
%%
At line 71 added 2 lines
However, the number shown above has difference from previous work done by others, eg, Hara'san result:
At line 60 changed one line
!As I mentioned above, this is a preliminary study on EIS compression factor. The method and results shown here need to check, confirm and compare with other number. There are still mystery hide behind these numbers. It is really just a start, so more contributions are very welcome!
\\
At line 88 added 3 lines
This work is just a start, the method and results shown here need to check again, and compare with other numbers. !As I mentioned above, these are only preliminary results on EIS compression factor. Still there are more need to be done, so any contributions, comments and suggestions are very helpful!\\
At line 66 changed one line
For target selection, in this case, uses value of %%(color:#cc0000;)SCI_OBJ%% keyword instead of %%(color:#cc0000;)TARGET%% keyword as the later is only for (study/raster) design stage, the actual targets are decided during the EIS planning.
As for target selection, in this case, I uses value of %%(color:#cc0000;)SCI_OBJ%% keyword instead of %%(color:#cc0000;)TARGET%% keyword as the later is only meaningful at (study/raster) design stage, the actual target is chosen during the EIS planning.
At line 68 changed one line
However, there is not always having value for SCI_OBJ in EIS fits header, also the range of value of SCI_OBJ keyword is varying, ([SCI_OBJ_Example]), sometimes we have to throw away some EIS data as it's hard to judge the SCI_OBJ belong to QS,AR or CH, eg. LMB, or FIL.
However, sometimes there is no value for SCI_OBJ in EIS fits header, and sometimes there are two many values (see [SCI_OBJ_Example]). Lots of EIS dataset are thrwon away as hardly to decide to which catagroy the SCI_OBJ belongs to, such as QS,AR or CH.
At line 71 changed one line
There is a compensation for paused (and aborted) raster. This is implemented by comparing %%(color:#cc0000;)NEXP%% and %%(color:#cc0000;)RAST_REQ%% and times the ration of two values
Compensation has been applied for those paused (and aborted) rasters. This is implemented by comparing %%(color:#cc0000;)NEXP%% and %%(color:#cc0000;)RAST_REQ%% and timing the ratio of two values.
At line 74 changed one line
The related information for investigated EIS data set has been stored in a structure array, which has elements with the following format:
There is a structure array to store all related information for the EIS data investigated here. The array has element with the following format:
At line 99 changed one line
I attached the IDL sav file [here|http://msslxr.mssl.ucl.ac.uk:8080/eiswiki/images/newgifs/20071201_20071215.sav.tar.gz]. Please download it and play it with your self, for example, I use:
I attached an IDL sav file [here|https://vsolar.mssl.ucl.ac.uk/eiswiki/images/newgifs/20071201_20071215.sav.tar.gz]. You may download and play it, for example, I use:
At line 103 changed one line
to find those records having 'QS' SCI_OBJ and using DPCM compression scheme.
to extract records associated with 'QS' SCI_OBJ and using DPCM compression scheme.
This page (revision-43) was last changed on 18-Apr-2021 19:03 by JianSunTop