IMAP-Hi L1B Histogram Quicklook

[tech3371]

From the algorithm document (https://lasp.colorado.edu/galaxy/download/attachments/146768943/imaphi-data.pdf?version=6&modificationDate=1742930198196&api=v2):

2.2.2 Pretty Histogram Outputs
The SDC should have the general capability to generate a “histogram plot” for a Pointing as follows.
For a specified sum of histogram types available in the IMAP-Hi histogram packet (e.g., qualified AC1
plus qualified AC1C2), plot, with time on the horizontal axis and spin phase on the vertical, the counts
observed in each 4◦ spin bin, according to a rainbow+white linear autoscaled colourbar beginning at 0.
These plots should be stacked with the first ESA in the stepping sequence (nominally ESA 1) at the top
and the final ESA (nominally ESA 9) at the bottom. The ordering is by entry in the stepping sequence
table (not by the voltages actually on the electrostatic analyzer). The spin phase at the top of each plot
should correspond to the 4◦ bin at which Hi45 or Hi90 was looking closest to NEP (HAE ˆz). Stepping in the
horizontal axis should align with every new set of ESA 1 data. As long as histogram data follows sequentially
for increasing ESAs, the same vertical alignment should be used; the time axis should increment on each
new ESA 1 data set, or on nonconsecutive ESA histogram packets (e.g., an ESA 4 histogram packet followed
by an ESA 7 histogram packet would start a new column with the ESA 7 data; two consecutive ESA 1
histogram packets would display next to each other, with only zeros shown for ESAs below the first ESA 1
histogram packet of the pair). If science data for a given Pointing begins with data from an ESA other than
the first (as it will if IMAP-Hi is operated through repointing maneuvers), the first column of data will be
empty until the first ESA seen. Any missing or empty entries in the plot should be set to zero.
No interpolation or averaging should ever be performed by the plotting package when generating this
plot. The goal is to see exactly what the data was, warts and all.
These plot should include all histogram data available for a Pointing, whether or not any of it ends
up being marked as bad. The plots are for diagnostic purposes and are useful for looking for “anything
interesting”.
One should assume that the science team would like actual plots, in directly viewable format, for every
defined calibration product, even if they may then go off and make additional plots on their own. However,
with the expectation that qualified TOF windows will be wider onboard than on ground processing, it’s not
actually possible to produce such plots exactly from the onboard histograms. By default, make one such
plot for each sensor, each ESA energy step, and representative of each calibration product,
using the on-board qualification scheme rather than the ground-based TOF ranges.
The units of the plot are debatable and you probably want the ability to label it either as counts or count
rates. I prefer actual integer counts, but there are those who’d like you to divide every single bin by (nearly)
exactly the same exposure time (8 spins at 15s/spin, or whatever the average spin value ends up being for
the Pointing, divided into 90 angle bins is 1.33 s per bin; the slight change in exposure time from bin to bin
over the Pointing is ignorably small for the purposes of this diagnostic plot) and call it a rate instead. You’ll
notice the example plot in Figure 3 isn’t even labelled.
These plots should be done independently for Hi90 and Hi45.
Note: some people prefer the horizontal axis to line up exactly with time, to make any data dropouts
more obvious. I’m not averse to this concept either, as long as standard ESA 1-9 products are stacked and
not slanted.
An example plot from IBEX-Hi is shown in Figure 3.