The files in the munin directory were provided by South West Research Institute (SWRI)
and delivered to the SPDF on August 25, 2017.  This readme was written Ruddy Frahm.

MUNIN Data exists from about 2000 December 9 (344) through 2001 February 11
(042).  The MUNIN spacecraft had its first telemetry failure around 2000
December 20 (355), when the MUNIN telemetry system lost more than half of 
its capability.  Data from other instruments on the MUNIN spacecraft are
not presently recoverable.  This archive consists of data from the 
Miniaturized Electrostatic Dual-tophat Spherical Analyzer (MEDUSA)
instrument, and spacecraft orbit and attitude information.  The MUNIN 
telemetry system experienced a total failure on 2001 February 11 (042) 
when communication with the spacecraft was lost.

Some data from MUNIN was originally stored in the Instrument Data File Set 
(IDFS) format (http://www.idfs.org/).  In 2017, this data was converted into 
the Common Data Format (CDF - https://cdf.gsfc.nasa.gov/) and stored in the 
Space Physics Data Facility (SPDF) archive.  Data in this archive was 
validated by comparing CDF images with IDFS images.  Different software 
programs were used to compare IDFS data with CDF data, so exact comparison 
is not expected due to the differences in the display software.  The CDF 
is drawn using the gPlot program whereas IDFS data is drawn using the 
SpectroScalar program.  Both programs are available through the Southwest 
Data Display and Analysis System (SDDAS - http://www.sddas.org/).  
Differences observed in the data images are discussed below.  

1) Data Range - The CDF images do not show as much depth as the IDFS images
   due to differences in the imaging programs.  With gPlot, the image from 
   the CDF is composed of the last item written into the pixel.  gPlot holds 
   a stack of spectra at each pixel to allow for panning and zooming.  
   SpectroScalar does not allow panning and zooming, but displays the IDFS 
   values as averages of all spectral data that falls within a pixel.  As
   a result, the SpectroScalar image of IDFS data shows a larger data range
   because data in a pixel has been averaged; whereas, the gPlot CDF image
   just shows the last spectrum in the pixel.

2) Plot Resolution - In some cases the IDFS image from SpectroScalar does not 
   show data on the same axis scale as the CDF image using gPlot.  Images from
   the auto scale using gPlot show the full variation in the data, which can
   mean scale variations down to the sixth decimal place are displayed; 
   whereas, IDFS in SpectroScalar does not auto scale draw to this resolution.
   Thus, what appears as a straight line in SpectroScalar can appear as a line 
   with slope in gPlot.

3) Color Differences - gPlot images use a slightly different color bar to
   draw the CDF file contents than do images from SpectroScalar drawing IDFS 
   data.  Image differences can be detected which are caused by differences 
   in the color bar used by the two programs rather than in the data.

4) Data Gaps - CDF data drawn with gPlot shows locations where gaps in the 
   data occur.  SpectroScalar masks these gaps by drawing lines between
   IDFS data values, making it appear that there is continuous data.

The MUNIN spacecraft failed due to the telemetry system.  The symptoms were
observed early on in the mission where telemetry bits would be either filled 
with noise or were entirely missing from telemetry.  In general, the noise
filled the entire spacecraft telemetry frame and produced values which appear 
as energy independent noise within the instrument data.  These bad data values 
are kept within the CDF data conversion as the CDF is a copy of the IDFS data.  
In some cases these noise streaks appear smaller or do not appear within the 
CDF images from gPlot.  However, these streaks are actually included within 
the data file and are masked by the way gPlot handles data within a pixel.

The user should also be aware that there are times where the MUNIN telemetry 
system inserted noise into part of the MEDUSA telemetry.  These times appear
as time dependent chatter within energy bands or time independent high values
for part of the energy sweep.  It is left to the user to discard or try to 
recover any underlying MEDUSA data at these times.

At other times, the telemetry system would lose time synchronization.  These 
times can be identified when the lower and upper portions of the MEDUSA energy 
spectrum appear to be swapped. 

The MEDUSA instrument had no special high radiation shielding, so penetrating 
radiation may swamp data from MEDUSA when MUNIN passes through the horn of
the radiation belts.