Weak Gravitational Lensing Shear Estimation with Metacalibration for the
  Roman High-Latitude Imaging Survey
  We investigate the performance of the Metacalibration shear calibration
framework using simulated imaging data for the Nancy Grace Roman Space
Telescope (Roman) reference High-Latitude Imaging Survey (HLIS). The weak
lensing program of the Roman mission requires the mean weak lensing shear
estimate to be calibrated within about 0.03%. To reach this goal, we can test
our calibration process with various simulations and ultimately isolate the
sources of residual shear biases in order to improve our methods. In this work,
we build on the Roman HLIS image simulation pipeline in Troxel et al. 2021 to
incorporate several new realistic processing-pipeline updates necessary to more
accurately process the imaging data and calibrate the shear. We show the first
results of this calibration for six deg$^2$ of the simulated reference HLIS
using Metacalibration and compare these results to measurements on more simple,
faster Roman-like image simulations. In both cases, we neglect the impact of
blending of objects. We find that in the simplified simulations,
Metacalibration can calibrate shapes to be within $m=(-0.01\pm 0.10)$%. When
applied to the current most-realistic version of the simulations, the precision
is much lower, with estimates of $m=(-1.34\pm 0.67)$% for joint multi-band
single-epoch measurements and $m=(-1.13\pm 0.60)$% for multi-band coadd
measurements. These results are all consistent with zero within 1-2$\sigma$,
indicating we are currently limited by our simulated survey volume. Further
work on testing the shear calibration methodology is necessary at higher
precision to reach the level of the Roman requirements, in particular in the
presence of blending. Current results demonstrate, however, that the
Metacalibration method can work on undersampled space-based Roman imaging data
at levels comparable to the requirements of current weak lensing surveys.
