Multi-frequency Imaging Algorithms and Simulation of Space VLBI Using the VLA

New Multi-Frequency Synthesis (MFS) algorithms were developed and implemented in the Astro Space Locator (ASL) operating under MS Windows system. In November 2005 multi-frequency VLA observations of the radio source M87 were carried out at the following frequencies: 14.7, 15.2 21.3, 22.2, 23.0, and 23.4 GHz. We used the new MFS algorithms to determine the structure of M87 at the central frequency (19 GHz) and obtained both the image and spectral index map of the source. Comparison with more straight-forward imaging techniques (with single frequency images) shows that the new MFS algorithms increase the fidelity of the image by at least a factor of two and provides accurate spectral indices across the emission. Application to simulated Radioastron data is also shown.