VLBA Sensitivity UpgradeProject Status

Jon RomneyNRAO, Socorro

7th US VLBI Technical Coordination Meeting

Haystack Observatory2009 November 3–4

7th US VLBI Technical Coordination Meeting

22009 / 11 / 3-4 – jdr

Project Goal

Expand the VLBA’sdata-path bandwidth to

4 Gbps by 2011

Goal has been widely and frequently announced within the radio astronomy, astrometry, and geodesy communities. VLBA users are waiting to exploit it to enable a variety of

compelling new science.

7th US VLBI Technical Coordination Meeting

32009 / 11 / 3-4 – jdr

Implementation

Goal Corresponds to:2 IFs @ 500 MHz BW @ 2-bit Nyquist samples[i.e., retaining VLBA’s original IF system.]

New ElementsRDBE sampler/filter unit.Mark 5C recording system.DiFX software correlator.

7th US VLBI Technical Coordination Meeting

42009 / 11 / 3-4 – jdr

Project Status

DiFX Software Correlator OperationalComparisons with original VLBA correlator yielded excellent results.

Exactly matched integrations show amplitude and phase agreeing far better than realistic expectations.

Science use cases, analyzed by expert VLBA users, finding primarily limitations of data-analysis algorithms, not problems in correlator results.

DiFX alone enables some new scientific techniques.High spectral resolution.Wide-field imaging.Special pulsar processing.

Announced for correlation of all observations proposed Oct. 1.Observation trimester beginning mid-January.

Planning to ramp up use beginning as soon as possible.But DiFX can’t really come into its own without wideband observations.

7th US VLBI Technical Coordination Meeting

52009 / 11 / 3-4 – jdr

Status, continued

RDBE & Mark 5CAbsolutely central to achieving 4-Gbps goal.Some initial efforts successfully behind us:

ROACH final design, layout, exhaustive testing, beginning of production.Mark 5C concept design, development and production of 10 Gig E interface

mezzanine board.But both efforts have encountered schedule slippages, sufficient to

become serious concerns.Both NRAO &Haystack have major competing priorities: EVLA & MWA.Conduant also?

To recover schedule, we need to consider alternative approaches, possibly including

Additional personnel resources.(Matt Luce recently joined NRAO team, for FPGA development.)

Simplified, less comprehensive design “at least initially”.We hope to revisit these points throughout this meeting!

7th US VLBI Technical Coordination Meeting

62009 / 11 / 3-4 – jdr

Thank You