MEROPE payload data analysis HOWTO
Description:
The MEROPE payload data is binned in number as opposed to the normal binned
in time. What this means is that we recored only
the time at which the N'th count occured. The bins in number are N
counts each. The reason for this it that one only has to report
one quantity (the time at which the N'th count happened-N is fixed) instead
of # of counts and time that it happend in.
The data files are columns containing the time at which the N'th count was
recieved. To "best" look at the data we plot a histogram
of the numbers binned in time. By doing this we have in effect created
a arbitary time binning resolution for the data, the smaller the
binsize the rougher the graphs look.
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Keywords:
merope_payload.pro has many
keywords they are:
binsize= - sets binsize (default=~2)
/notitles - omits the standard titles on output
/ylog - plot the y axis
as a log scale
title= - add a custom title
subtitle= - add a custom subtitle
xtitle= - add a custom x title
ytitle= - add a custom y title
xrange= - set xrange to a value different than whole
histogram eg: xrange=[2,5]
ps= - sets
output to postscript and filename (remember quotes ' ;)
/portait - when using ps plots in portriat mode
/nostats - do not calculate statistics on the histogram
(output to screen)
jpg= - sets output
to jpg and filename (remember quotes ' ;) requires x2jpg.pro
/stop - tells the program
to stop at the end maintaining variables
cps= - sets the counts
per stamp (N) also changes titles (outputs count rate)
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This howto wil be run as a step by step look at
a data file howto.payload,
analyzed with the code merope_payload.pro.
Examples:
- unix> idl
- idl> ls
-lists files in current directory-
- idl> merope_payload, 'howto.payload'
# stamps: 21468
Mean: 23.643172
Variance: 240.33119
STD DEV: 15.502619
ABS DEV: 13.75801
Skewness: 0.11747761
Kurtosis: -1.3390048
--Note here that we get statistics on the idl terminal as well as
the graph--
- idl> merope_payload, 'howto.payload', binsize=5.0, /nostats
--Note that with the keyword set nostats we do not get the
stats in the idl terminal--
- idl> merope_payload, 'howto.payload', binsize=2.5, /nostats, /ylog
--Note that the keyword set ylog we get a log y-axis--
- idl> merope_payload, 'howto.payload', binsize=2.5, /nostats, /ylog,
ps='howto.ps'
or idl> merope_payload, 'howto.payload', binsize=2.5, /nostats,
/ylog, jpg='howto.ps'
--Note the quotes on the filenames for ps and jpg--
- idl> merope_payload, 'howto.payload', binsize=2.5, /nostats, cps=500
--Note that the axes now reflect count rate because you specified
the counts
per bin for the data.
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FAQ:
Questions:
- Why is the binsize different than what i set at the
IDL prompt?
- Why are there all the little bumps in the data that
are 1 bin tall?
- This data is all fine and great but where in space
is it?
Answers:
- This is an interesting problem with the way the data
is taken in the hardware, sufficient to say that the time needs to
be a multiple of the internal MEROPE system clock to get meaningful results.
back
- This is another interesting hardware issue, the system
clock and the payload share the same interrupt space and therefore
only one can be served at a time, so one bin with one more stamp comes from
the system clock not being able to increment
until the payload interrupt is done, so the bins are a little longer and
shorter, hence more or less stamps by 1. back
- Good question... as of yet (prelaunch) we
have no information on satellite position and this will be implemented when
we have data to play with. back
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Required Functions:
MEROPE_PAYLOAD.PRO was origionally written using the Solar-Soft package.
While this is no longer necessary some
Solar-Soft functions are still required as well as some on my own, there
are listed here:
note: If you are at MSU it is easiest to just include /home/larsen/idl
on mithra in your idl_startup script.
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Brian Larsen
Wed Jul 31 16:30:25 2002
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