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Correlator Interface Issues Jim Ulvestad 1 November 2006

Correlator Interface Issues Jim Ulvestad 1 November 2006. Uplink Station. Predicted orbit required for computation of uplink frequency Accurate predicted orbit will minimize size of time correction at correlator Time Correction File

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Correlator Interface Issues Jim Ulvestad 1 November 2006

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  1. Correlator Interface IssuesJim Ulvestad1 November 2006

  2. Uplink Station • Predicted orbit required for computation of uplink frequency • Accurate predicted orbit will minimize size of time correction at correlator • Time Correction File • Unlikely to be more accurate than VSOP, so correlator will require high-order fit • Require common tracking station interface • Desire common sampling rate

  3. Reconstructed Orbit • Require highest possible orbit accuracy • Phase referencing at 8 GHz • Eliminate need to fit delay acceleration • Unmodeled quadratic terms must not reduce high-frequency coherence • 0.1 radians at 43 GHz in 2 minutes corresponds to 10-5 cm/s2 • Orbit delivery should be within one week of observation, if possible

  4. VLBI Data Transfer to Correlator • eVLBI not feasible due to need for accurate reconstructed orbit • Common recording format/media • Mark 5B, using VLBI Standard Interface, is the most likely standard • All data required at correlator within one week of observation

  5. VLBA Correlator Status in 2012 • Present VLBA correlator has sustainable rate of 256 Mbit/s • Limited capacity for 512 or 1024 Mbit/s • EVLA WIDAR correlator will have enough spare capacity for 20 stations at 4 Gbit/s • Likely number of playbacks is 10-20 • Issues • WIDAR delivery, software implementation • Will VLBA still be in operation in 2012?

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