Mapping the recent expansion history of the universe offers the best hope for uncovering the characteristics of the dark energy believed to be responsible for the acceleration of the expansion .
In determining cosmological and dark-energy parameters to the percent level , systematic uncertainties impose a floor on the accuracy more severe than the statistical measurement precision .
We delineate the categorization , simulation , and understanding required to bound systematics for the specific case of the Type Ia supernova method .
Using simulated data of forthcoming ground-based surveys and the proposed space-based SNAP mission we present Monte Carlo results for the residual uncertainties on the cosmological parameter determination .
The tight systematics control with optical and near-infrared observations and the extended redshift reach allow a space survey to bound the systematics below 0.02 magnitudes at z = 1.7 .
For a typical SNAP-like supernova survey , this keeps total errors within 15 % of the statistical values and provides estimation of \Omega _ { m } to 0.03 , w _ { 0 } to 0.07 , and w ^ { \prime } to 0.3 ; these can be further improved by incorporating complementary data .