Converts a Themis VIS or IR PDS spectral cube into an Isis Cube. The Themis
IR cube will automatically be converted to 32-bit floating point unless the
user specifies differently by modifying the output files attributes. This is
done to accommodate different core/base multiplier values for each band.
The output for an ingested Themis VIS cube will be two files, one consisting
of even framlets and the other of odd framelets. These framelet files will
have the name of the TO parameter with ".even" and ".odd" inserted prior to
the ".cub" extension. For example, if the TO parameter was out.cub,
the even framelet file of the output would be named out.even.cub.
The software assumes that the SCLK (spacecraft clock) recorded for an IR image is the time at which the first detector frame readout occurs. Apparently, the actual first readout can be delayed from this by the following amounts:
8 microseconds - PACI write
0 to 1/30 sec - delay of the image acquisition after receipt of the command
0 to 0.1 sec - delay for the command sending by the HPP code so that it is aligned on a 0.1 second boundary
Currently, the software ignores these three because the 8 microseconds is a negligible fraction of the 1/30 second line rate and the other two are (apparently) variable and unknowable. However, this can result in an incorrect absolute position of as much as four pixels.
Similar timing uncertainties probably are applicable to the VIS images.
The effect of these timing uncertainties is primarily to potentially introduce errors in absolute coordinates in the along-track direction. This in turn can result in misalignment when mosaicking multiple observations together.
The TIMEOFFSET parameter on "thm2isis" allows the user to apply a correction for this time delay, which can thus improve absolute coordinate accuracy and improve mosaic alignments. This offset is stored in the Instrument group of the output Isis cube as SpacecraftClockOffset.