2007 / 5 / 141 VLBA Requirements, Plans & Status Jon Romney NRAO, Socorro Second US VLBI Technical Coordination Meeting Socorro 2007 / 5 / 14

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 2 VLBA Sensitivity Upgrade Overall Theme Restore VLBA competitiveness through enhanced sensitivity. … as well as expanded flexibility and compatibility in observing modes. Two Basic Sub-Projects Upgrade selected receiver systems. … through replacement of LNAs. Results with first three upgrades at 1.3 cm suggest doubling of VLBA sensitivity at this band will be possible. Upgrade entire data path downstream from IFs. Sampler-Filter / Recording System / Correlator. Each is directly relevant to main discussion areas at this meeting.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 3 VLBA 4-Gbps Data Path Upgrade Replace All Equipment Downstream from IFs MHz 2 bits / Nyquist sample → 4 Gbps. Target completion: Wideband Sampler/Filter module. Wideband Recording system. Wideband Correlator.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 4 Wideband Sampler/Filter Module Replaces BBCs / Samplers / Formatter Initial NRAO Concept Exploit expertise in FPGA design developed in EVLA project. Transfer functionality implemented there to a VLBA application. Outlook for rapid completion matched personnel availability. Target: end of FY First US VLBI Meeting (Haystack, 06/10/25-26) Recognized potential synergy with Haystack DBE-2 plans. Initiated joint collaborative development.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 5 Wideband Sampler/Filter Module [2] NRAO/ Haystack Development Scope expanded to accommodate VLBI-2010 requirements. Increased bandwidth; doubled sampler clock. Added fast memories for corner-turning. Two-board concept to support both VLBA and VLBI-2010 usage economically. iBob-2 Learned about UCB/CASPER plans for iBob-2 at end of March. Inadequate capacity as specified, but possibly could be expanded. Possibly attractive option, but also possible delay. Timescale for design completion not clear. Scope and organization of international collaboration not clear.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 6 Wideband Sampler/Filter Module [3] Current NRAO Status Internal mandate to complete prototype by end of FY Will probably adopt two-track approach (pending outcome of this meeting). Rapid Completion of 4-Gbps “VDBE” Prototype Matched to basic VLBA requirements, plus whatever else can fit and be included without significant delay. In-depth review by Mike Revnell this afternoon. Parallel, Longer-Term Collaboration on iBob-2 … with UCB/CASPER, Haystack, South Africa, et al. Matched to VLBI-2010 requirements. Re-evaluate if design ready when 4-Gbps prototype complete.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 7 Wideband Recording System Major Gap in NRAO Development Efforts Urgently need a way to transmit 4-Gbps data from new wideband sampler/filter to wideband correlator. First US VLBI Meeting (Haystack, 06/10/25-26) Decided to approach Conduant Corp. about potential “Mark 5C” system, capable of continuous recording at ≥ 4 Gbps. Haystack/NRAO Visit to Conduant (07/2/12) Agenda included 4-Gbps recording. … in addition to many other, more immediate concerns. Encouraging indications that could be achieved. … using Conduant’s new “Amazon” board, and well before 2011.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 8 Wideband Recording System [2] NRAO Status Internal funding requested to support Conduant Mark 5C development. Seek to be involved in ongoing design. Hope to learn much from presentations later this morning.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 9 Wideband Correlator Replaces Original VLBA Correlator Sufficient capacity to keep up with current and future mix of VLBA observations. Significantly enhanced bandwidths, spectral resolution, integration times, special processing modes, and flexibility. Continuity of results across transition. Two Different Options Under Consideration …

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 10 Wideband Correlator [2] Software Correlation on Cluster System ‘DiFX’ software written by Adam Deller at Swinburne University. Variety of peripheral software required to interface to VLBA, most already complete. Software free; cluster hardware cost TBD. Everyone’s favorite option – if we can afford 4-Gbps system. Mini-cluster under construction for test purposes; internal funding requested for intermediate-scale system. In-depth review by Walter Brisken Tuesday morning.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 11 Wideband Correlator [3] Hardware Correlation on EVLA WIDAR … designed by Brent Carlson at DRAO. Use excess capacity in 32-station system. Hardware free; software may be expensive and/or late. Additional complications in control & resource allocation. Availability may be fairly late for 2011 target date. Dedicated Mini-WIDAR for VLBA … using additional boards of same design. Hardware might be contributed by Canada; software might be less expensive. In-depth reviews by Craig Walker Tuesday morning.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 12 e-VLBI NOT Part of VLBA Sensitivity Upgrade Project NRAO has had a negligible involvement in operational e-VLBI. Recent VLA-Westford test series providing some welcome encouragement. … from preparations at least, even if no solid results yet. US e-VLBI Roadmap document should be finalized, with inclusion of Arecibo input. In-depth review by Steve Durand Tuesday afternoon.

2007 / 5 / 14 – jdrSecond US VLBI Technical Coordination Meeting 13 Thank you