Journal: Transactions of IAA RAS vol. 40
Keywords: Radioastron, VLBI, Data processing, ASC Correlator
The “Radioastron” space mission is an unique project of Russian Space Agency (Roscosmos) and Russian Academy of Sciences to investigate the Universe by means of VLBI implementation. “Spektr-R” is a sattellite with on-board 10-m radio telescope. It has been operating since November 15, 2011 as a space element of the space-ground interferometer with the orbit apogee up to 350 000 km. Here we describe the first step in VLBI data processing is correlation. Space-VLBI brings new requirements to the correlation process due to significant uncertainties in delay model for space telescope. The software correlator (ASC Corrrelator) was developed at Astro Space Center of Lebedev Physical Institute specially for the “Radioastron” mission to accomodate all pecularities of Space-VLBI data processing. This correlator is a part of ASL (Astro Space Locator) software package. In this report the main features of the ASC Correlator are described with the emphasis on the Space-VLBI data-processing differences compared to the ground VLBI. This includes a time delay and its derivatives calculation algorithm and the procedure of correction for these parameters. It is critical for correlation of space-ground interferometer data. We also show the importance of the orbit accuracy and the requirements for correlator of the future Space-VLBI missions, such as the “Millimetron” project.