BIPP: An efficient HPC implementation of the Bluebild algorithm for radio astronomy

The Bluebild algorithm is a new technique for image synthesis in radio astronomy which forms a least-squares estimate of the sky intensity function using the theory of sampling and interpolation operators. We present an HPC implementation of the Bluebild algorithm for radio-interferometric imaging: Bluebild Imaging++ (BIPP). BIPP is a spherical imager that leverages functional PCA to decompose the sky into distinct energy levels. The library features interfaces to C++, C and Python and is designed with seamless GPU acceleration in mind. We evaluate the accuracy and performance of BIPP on simulated observations of the upcoming Square Kilometer Array Observatory and real data from the Low-Frequency Array (LOFAR) telescope. We find that BIPP offers accurate wide-field imaging with no need for a w-term approximation and has comparable execution time with respect to the interferometric imaging libraries CASA and WSClean. Futhermore, due to the energy level decomposition, images produced with BIPP can reveal information about faint and diffuse structures before any cleaning iterations. The source code of BIPP is publicly released.