**[TIDE Chromograms]{.underline}**

**Introduction:**

TIDE chromograms are used to display multi-dimensional data. For TIDE
data, the color intensity is used to represent one dimension (ion flux).
Color is used to represent a second dimension, either particle energy,
spacecraft spin angle, or TIDE polar angle channels. The vertical axis
on each panel is another dimension either spin angle or energy. The
horizontal axis has two dimensions. Between each of the white tick marks
is energy, spin angle, or polar channel. The entire horizontal axis
represents time, one spin average at a time. Each panel represents the
final dimension: ion mass (H+, He+, O+, m/q=2, and/or NO+). Six
dimensions are display on a single plot. The software allows the user to
select what dimension is used for color, and on the vertical and
horizontal axes. If color is not based on polar channel, the polar
channel has to be used on the horizontal axis because of the limited
number of polar channel bins (only 7). There are 31 energy bins and 32
spin angle bins. The energy and angle bins are described in
<http://satyr.msfc.nasa.gov/archive/tide_docs/ProcFiles/DataFiles/energy_angle.bins>.

Stops (Total Ions) have no polar angle resolutions (i.e. counts have
been summed on the polar angle channels) so chromograms cannot be
created fro data after 12/07/96.

**Color Calculation:**

The color is determined by spitting the range of the color dimension in
to three parts. The first part is used to determine the red component of
the color, the second part the green component of the color, and the
third part, the blue component of the color. The color can be based on
an 8-bit color scheme with only 216 possible colors (6 values for each
color component) or a 24-bit color scheme (256 values per color
component). Due to the limit amount of color variations that the human
eye can see, the 8-bit works as well as the 24-bit color scheme. Note:
the 8-bit color option is the only one available on the web interface.

If color is based on polar channels (1-7), the user specifies the polar
angle channels used for each color. For spin angle (0-360 degrees), the
user-specifies the angles at the red/green, green/blue, and blue/red
boundaries. For energy (0-373 eV), the user-specifies the minimum red,
the red/green and green/blue boundaries, and the maximum blue eV.

Before calculating color, for each energy, spin angle, and polar channel
bin, the counts are converted to the user-specified flux units with
sector sensitivity and mass calibration applied and if requested minimum
count subtracted. The logged flux value is adjusted so that it falls
between the user-specified minimum and maximum color intensity values,
i.e. the logged flux value is adjusted so that it is between zero and
the flux difference (flux maximum minus flux minimum). If color is based
on energy, for each polar channel and spin angle bin, the flux values
are averaged for each color component based on the user-specified energy
ranges. If color is based on spin angle, for each polar channel and
energy bin, the flux values are averaged for each color component based
on the user-specified spin angle ranges. If color is based on polar
channel, for each spin angle and energy bin, the flux values are
averaged for each color component based on the user-specified polar
channels.

For 8-bit color, for each color component, the average is divided by
flux difference and multiplied by 6 giving a number between 0 and 5. The
index into the 8-bit color chromogram color table is calculated by
multiplying the red component by 36 and adding it to the green component
times 6 and adding the blue component. The actual color table used in
the software is calculated as the code is run but a text version called
chromo-8bit.tbl is available in /archive/tide_docs/ProcFiles/DataFiles.
The first 10 colors are not part of the chromogram color table. They are
used for shades and colors used for plot labeling. The remaining 216
colors are the color table.

For 24-bit color, for each color component, the average is divided by
the flux difference and multiplied by 256 giving a number between 0 and
255. The 24-bit color table is a three dimensional array, one for each
component. Each pixel in the 24-bit color chromogram is represented by a
red/green/blue color triplet, each value is between 0 and 255.

**Plot description:**

The output plot filename has the standard format:
**tyymmddh1m1_h2m2.ext2.ext1.ptype** where **t** stand for TIDE,
**yymmdd** is the 2-digit year, month, and day-of-month of the plot
start time, **h1m1** are the start hour and minute, **h2m2** are the
stop hour and minute, **ext2** is an optional file extension used to
distinguish plots processed differently but with the same start/stop
times, **ext1** is the chromogram extension, and **ptype** is the plot
type. If **h2m2** is smaller than **h1m1**, the plot crosses a day
boundary.

The chromogram plot file extension **ext1** indicates which dimension
was used where: polar channel is **p**, spin angle is **s**, and energy
is **e**. The horizontal axis dimension is listed first, the vertical
axis dimension second, and the color dimension third. So **.esp** is
energy on the horizontal axis, spin angle on the vertical axis, and
color based on polar angle. The other possible extensions are **.pse**,
**.pes**, and **.sep**. Note: when color is based on energy or spin
angle, polar angle is always plotted on the horizontal axis.

For 8-bit chromograms, IDL creates gif (**.gif**) and postscript
(**.ps**) plot types (**ptype**). A pdf (**.pdf**) file was created from
the postscript file because the .pdf file is much smaller but provides
the same resolution. Thumbnail jpeg (**.jpg**) were created from the
.gif files. For 24-bit chromograms, the IDL software creates plot types
of **.ps** and **.jpg** because early IDL gif software didn't support
24-bit color.

Samples of each type of chromogram for both the 8-bit and 24-bit color
schemes can be found in /archive/tide_docs/ProcFiles/Chromo/Plots or
<http://satyr.msfc.nasa.gov/archive/tide_docs/ProcFiles/Chromo/Plots/>.
The optional **ext2** file extension was used to distinguish the 8-bit
(**.8bit**) from the 24-bit (**.24bit**) chromograms.

As with most TIDE plots, there is some documentation at the bottom of
the plot that includes the processing software version number; date the
plot was created; plot filename; whether or not the minimum count was
subtracted; the names for the sector sensitivity, calibration, and mass
calibration files used in processing; source or value of the spacecraft
potential used; and the names of the mask, attitude, orbit, and
level-zero files used in the processing.

Above these are the time axis labels including time (hh:mm), Re,
L-Shell, magnetic local time (mlt), magnetic (mlat) and invariant
(invlat) latitude.

At the top left of the plot, the standard labeling includes the title
line (POLAR TIDE/PSI), the start and stop times of the plot, the number
of spins averaged, the data collapse option (see the TIDE Flight
Software Requirements Document, page 10-13 for collapse option details
http://satyr.msfc.nasa.gov/archive/tide_docs/old_docs/TIDEFlightSoftwareRequirements.pdf
), an indication that the spin data accumulation starts at the sun plus,
and a plotted indication of the operational status (operational,
standby, off, or mirror stepping) of both TIDE and PSI.

If the vertical axis is spin angle, the location of the ram (x), the
positive (+) and the negative (-) magnetic field directions are
indicated on the image.

At the upper-right of each plot are flux intensity color bar and the
chromogram color wheel indicating the ranges of data used to determine
the color and the colors that could appear on the chromogram image. If
color is based on polar angle, the location of the minimum/maximum ram
elevation (black) and the minimum/maximum magnetic elevation (white) are
drawn on the color wheel.

Each panel represents a mass. There can be anywhere from 1 to 5 masses
(H+, He+, O+, m/q 2, and/or NO+) on a plot.

The time axis is set up to display as much data as possible. The time
axis is made up of a series of spin-averaged sets of data. Each spin is
six seconds long. The number of spins averaged for each set of data on
the plot depends on the user-specified length of time for the total plot
and the dimension displayed on the horizontal axis. The start and stop
times of the plot and the number of spins averaged for each set of data
appears at the top left of a plot. If the horizontal axis is polar
channel, there can be up to 35 spin averages on the horizontal axis. For
spin angle and energy there can be up to 30 spin averages.

**lz-parm command files and tide_lz input files:**

All processing is controlled from the parameter file created using
lz_parm. See ParameterFileCreation.doc or
<http://satyr.msfc.nasa.gov/TIDE/Documentation/ProcessingSoftware/ParmFileChromo.html>
for details on creating the chromogram parameter file from **lz_parm**.
**lz_parm** can be run from a UNIX shell script that makes **lz_parm**
easier to use. Sample command files, those used to create the parameter
files that were used to create the sample plots are in
/archive/tide_docs/ProcFiles/Chromo/ParmCmd
(<http://satyr.msfc.nasa.gov/archive/tide_docs/ProcFiles/Chromo/ParmCmd/>).
Sample **tide_lz** input files (list of start and stop time and
associated input files) are in /archive/tide_docs/ProcFiles/InputFiles
(<http://satyr.msfc.nasa.gov/archive/tide_docs/ProcFiles/InputFiles/>).

**web-interface:**

8-bit chromograms can be created using the TIDE Custom Plot Chromogram
web-interface: http://satyr.msfc.nasa.gov/TIDE/lz_chromograms.shtml. All
of the prompts are designed to get the input used to create the lz_parm
parameter file and the tide_lz list file that contains the start and
stop times and a list of input files associated with that time range.
The webpage is filled in with some defaults that you can change. At the
top of the webpage are some clickable examples of each type of
chromogram plot.

All TIDE custom plots ask for the start and stop date range of the data
to be processed. The date can be enter as year/day-of-year (**yyyydoy**)
or year/month/day-of-month (**yyyymmdd**). The year must be four digits.
Time is entered in hour/minute/second (**hhmmss**). Seconds must be
included even if they are **00**. Do not use any spaces. Use the tab key
or the mouse to move from one date/time field to the next.

There are a series of default parameter files that you can use in the
next prompt. Just select the chromogram type you want. And 'Submit
request'.

The default processing is what comes up in the second set of prompts.
You can change the masses plotted. Just unselect the massed you don't
want. You can change the flux units and range of the flux units on the
intensity scale. The standard processing that you have the option to
change includes selecting a different mask to use, whether or not to
correct the mask subtraction (See
TIDE\\documentation\\new\\DatafileFormat\\mask.doc for details), whether
or not to use the sector sensitivity correction (See
InstrCalibration.doc), and whether or not to subtract the minimum count
(See MinimumCountSubtraction.doc for details). The last set of prompts
lets you select the type of chromogram to create and the ranges of the
dimension that the color will be based on. Once you have made all the
changes you want to the default plot settings '**Submit request**'. To
clear the form '**Reset Form**'.

Once you '**Submit request**', the web server queries the File Location
Table to get a list of the input files needed for the processing and
where they are stored. This information is used to create the
**tide_lz** list file. The information provided via the menu is used to
create the parameter file via **lz_parm**. The web server uses the
parameter and list files as input to the idl version of **tide_lz**
(@**run_tide**). Once the processing is completed and the postscript,
gif, and pdf files are created, the gif image is returned as a webpage.
Any or all of the plot files can be downloaded from this webpage. The
plots files remain in a staging area
(<http://satyr.msfc.nasa.gov/stage/>) for three days. They can also be
downloaded from the staging area. The web uses the job process id as the
optional **ext2** filename extension.