  We characterize the Millimeter Astronomy Legacy Team 90 GHz (MALT90) Survey
and the Mopra telescope at 90 GHz. We combine repeated position-switched
observations of the source G300.968+01.145 with a map of the same source in
order to estimate the pointing reliability of the position-switched
observations and, by extension, the MALT90 survey; we estimate our pointing
uncertainty to be 8 arcseconds. We model the two strongest sources of
systematic gain variability as functions of elevation and time-of-day and
quantify the remaining absolute flux uncertainty. Corrections based on these
two variables reduce the scatter in repeated observations from 12-25% down to
10-17%. We find no evidence for intrinsic source variability in
G300.968+01.145. For certain applications, the corrections described herein
will be integral for improving the absolute flux calibration of MALT90 maps and
other observations using the Mopra telescope at 90 GHz.
