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Space Very-Long-Baseline-Interferometry (S-VLBI) observations at highfrequencies hold the prospect of achieving the highest angular resolutions andastrometric accuracies, resulting from the long baselines between ground andsatellite telescopes. Nevertheless, space-specific issues, such as limitedaccuracy in the satellite orbit reconstruction and constraints on the satelliteantenna pointing operations, limit the application of conventional phasereferencing. We investigate the feasibility of an alternative technique, sourcefrequency phase referencing (SFPR), to the S-VLBI domain. With theseinvestigations we aim to contribute to the design of the next-generation ofS-VLBI missions. We have used both analytical and simulation studies tocharacterize the performance of SFPR in S-VLBI observations, applied toastrometry and increased coherence time, and compared these to results obtainedusing conventional phase referencing. The observing configurations use thespecifications of the ASTRO-G mission for their starting point. Our resultsshow that the SFPR technique enables astrometry at 43 GHz, using alternatingobservations with 22 GHz, regardless of the orbit errors, for most weathers andunder a wide variety of conditions. The same applies to the increased coherencetime for the detection of weak sources. Our studies show that the capability tocarry out simultaneous dual frequency observations enables the application tohigher frequencies, and a general improvement of the performance in all cases,hence we recommend its consideration for S-VLBI programs.

Exploration of SFPR techniques for astrometry and observations of weak sources with high frequency Space VLBI