  We present a new technique to extract the cosmological information from
high-redshift supernova data in the presence of calibration errors and
extinction due to dust. While in the traditional technique the distance modulus
of each supernova is determined separately, in our approach we determine all
distance moduli at once, in a process that achieves a significant degree of
self-calibration. The result is a much reduced sensitivity of the cosmological
parameters to the calibration uncertainties. As an example, for a strawman
mission similar to that outlined in the SNAP satellite proposal, the increased
precision obtained with the new approach is roughly equivalent to a factor of
five decrease in the calibration uncertainty.
