2 NEW DEVELOPMENTS

This edition of the Observational Status Summary includes descriptions of two new instrumental developments that will radically enhance the VLBA's capabilities.

1. 2-Gbps Continuum Bandwidth: New technologies for digital signal processing, data recording, and correlation, have made possible an expansion of the VLBA's continuum bandwidth to 256 MHz per polarization. This corresponds to a recorded data rate of 2 Gigabits per second (Gbps), a 16-fold increase over the sustainable rate of 128 Megabits per second that was available when the VLBA was inaugurated, and 4 times the current standard data rate. The signal/noise ratio in a typical continuum observation will be improved by factors of 2-4.

   Overviews of the new wideband instrumentation are presented in Sections 6.9 and 6.10 of this document. More detailed information is available in a memo series, at http://www.vlba.nrao.edu/memos/sensi/ . Questions can be submitted via the NRAO Helpdesk, at https://help.nrao.edu/ .

2. Wideband 6-cm Receiver: The VLBA's original 6 cm receivers are being replaced with substantially upgraded systems based on the EVLA design. An expanded tuning range, covering 3.9 - 7.9 GHz, will enable observations of the 6.7-GHz methanol maser line, and reduced system noise will enhance continuum sensitivity by about 35% in this band. Initial installations of upgraded receivers, and the accompanying new feeds, have already been completed at a number of stations. However, availability of the new system's full capabilities has been paced by completion of a new downconverter module, and an associated RF switch controller, which are now in production. This final upgrade stage has now been completed at two VLBA stations (Pie Town and Hancock), with continuing installations scheduled to proceed at about one per month. Full ten-station operation with the new system is expected by August 2012.

   Preliminary information on the new receiver system's performance is incorporated in Table 3 in Section 5 of this document. An NRAO eNews article (Walker & Hayward 2011) presents a comprehensive description of the new receiver and its first light in November 2011.