ISIS Application Documentation
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Generates MESSENGER SPKs
Generates MESSENGER SPKs from the output of kerneldbgen and the NAIF utility commnt.
This program was created to help automate the process of generating new SPK DB files for the MESSENGER mission, as the output from the ISIS program kerneldbgen requires some further tweaking in order to be fully accurate. Specifically, it sets the end date of the reconstructed time period far into the future, which should be moved into a separate predicted section.
This program creates the predicted section. In order to determine the proper end time for the reconstructed range (and start time for the predicted range), a NAIF utilitt known as commnt is used (available as part of ISIS). Prior to running this program, the user should run commnt as shown in the following example:
commnt -r msgr_20040803_20120401_od233sc_0.bspHere, replace the argument with whatever the most recent BSP file happens to be. This will, however, dump far more information than this program is actually interested in. To get the relevant end time, pipe the output of commnt into the following:
grep -A 1 "Orbit" | sed -n "2p"An example of all this can be found in the downloadMessengerKernels script.
This program will typically be run automatically, and update the most recent DB file (generated by kerneldbgen) in place. The user optionally specify any UTC time or any output file, not conforming to the process laid out above.
The incomplete SPK DB file generated by kerneldbgen. This file will be added to in order to make a complete DB file, separating out part of the Reconstructed group to a separate Predicted group. Defaulted to use $ISISDATA/messenger/kernels/spk/kernels.????.db.
The new DB file, the result of extracting parts of the Reconstructed group out into a Predicted group. Defaulted to modify the input file in place.
This string should be formatted as a UTC time that will then be transformed into a TDB time. This format in particular is expected, as this value is expected to come from running the NAIF utility commnt on the most recent BSP and extracting the orbit date cut-off time.
This time will be used to take the existing end time from the Reconstructed group, set it to be the end time for the Predicted group, and then this time will mark the correct end time for the Reconstructed group and beginning of the Predicted group.