Production processing of a subset of VLBA observations with the DiFX
software correlator began 30 November, 2009. It is expected that by the
end of December all VLBA scientific observations will be processed by
DiFX offers these new capabilities and advantages:
- Spectral resolution as high as 4096 points per baseband channel, for any polarization configuration. Compared to the original VLBA hardware-based correlator, this is an increase by a factor of 4 for non-polar, and a factor of 32 for cross-polar processing. This resolution is available even for extreme narrow-band observations, and there is no limitation on spectral points across multiple baseband channels.
- Significantly shorter integration periods, in principle as short as twice the reciprocal frequency resolution.
- A substantially increased correlator output data rate limit of 10 MB per second of observing time, a ten-fold increase over the most recent maximum rate available (at speedup factor 1) on the original correlator.
- Processing of any recorded data bit rate in a single correlation pass. In particular, the current maximum recordable rate of 512 Mbps no longer requires two passes. However, this recording rate remains a limited resource since it is constrained by the VLBA Mark 5 media pool, and its use must be justified in proposals.
- Processing of any mix of VLBA, Mark 4, and Mark 5B formatted data.
- Sophisticated pulsar processing modes.
The maxima specified above are flexible, and can be waived on the basis of a sufficiently compelling scientific justification.
Please consult the updated VLBA Observational Status Summary for detailed information. Most aspects of DiFX are discussed in Section 7, while the new pulsar gating options are presented in Section 16, and Section 18 explains how wide-field observations could exploit the expanded output data rates now available. Current information is maintained on the “DiFX Arrives” web page.