Extracting shape measurements from optical images for the purpose of constructing shear maps requires high resolution, wide field data. This has been a major obstacle in the field of optical weak leasing throughout its history.
Due to the intrinsic difficulties associated with the imaging of radio data this problem is much more pronounced. We present a method for the extraction of shear modes from visibilities, somewhat removing the necessity, and hence issues, concurrent with imaging.Most weak lensing measurements so far have been conducted at optical wavelengths, but are subject to numerous challenges including correct removal of the effects the PSF, and dealing with noise bias as a function of size and magnitude.
Radio lensing measurements are therefore an intriguing alternative, but some techniques will suffer from the further difficulty of making unbiased images with limited UV coverage. We present a method for estimating the Fourier modes of the shear map on the sky, directly using the visibilities without going through an imaging process. We will discuss the successes and limitations of our approach so far.