VLBI Data Acquisition Terminal Modernization at the Deep Space Network

The Deep Space Network (DSN) is replacing the aging Mark IV Data Acquisition Terminal (DAT) with a digital backend, the DSN VLBI Processor (DVP). It is based on the Wideband VLBI Science Receiver (WVSR), a custom-made open-loop digital receiver developed at JPL that is successfully supporting differential-VLBI for spacecraft navigation (DDOR) and other radio astronomy applications, e.g. Earth orientation, astrometry, and spectroscopy observations.

From the WVSR the new acquisition terminal has inherited the Intermediate Frequency (IF) digitizer module, the firmware architecture, and monitor and control software. Among the new features, the DVP improves considerably the recording rate providing at least 2 Gbps with the goal of achieving 4 Gbps; uses a CASPER ROACH board for real-time Digital Signal Processing and channelization and streams the data into a Mark 5C recorder. This paper describes in detail the DVP in the context of similar digital developments (e.g., RDBE, DBBC).

As the new backend will not use the standard Field System environment to perform the VLBI observations, efforts are under way to make it compatible with non-JPL correlators, providing monitor and calibration data in the appropriate format. Lately an important effort has been made in the DSN towards automation of VLBI data acquisition using the Automation Language for Managing DSN Operations (ALMO). The automation process will be adapted for the new DAT.