1. 2005/7/131 Plans and Options for e-VLBI on the VLBA Jon Romney NRAO, Socorro 4 th e-VLBI Workshop 2005 July 13

2. 2005/7/13 – jdrVLBA Plans & Options2 Outline Update on NRAO’s Current “e-LBI” Project: EVLA (Phase 1). What the VLBA Has Been Doing instead of e-VLBI. E-VLBI Options for support of Mark 5 operations. Potential VLBA Fiber Connectivity

3. 2005/7/13 – jdrVLBA Plans & Options3 Update on NRAO’s Current “e-LBI” Project: the EVLA Expanded VLA (Phase 1) Burial of fiber complete…

4. 2005/7/13VLBA Plans & Options4 Enough Fiber to Cross the United States from L.A. to D.C. 93.2 Km (57.9 mi) of 12 fiber cable 19.2 Km (11.9 mi) of 36 fiber cable 36.5 Km (22.7 mi) of 60 fiber cable 4.6 Km (2.8 mi) of 96 fiber cable Total trench length is 65 Km (40.4 mi) Total cable length is 153.5 Km (95.4 mi) Total fiber length is 4441 Km (2759.6 mi) Total delivered fiber cable cost - $330K

5. 2005/7/13 – jdrVLBA Plans & Options5 Update on NRAO’s Current “e-LBI” Project: the EVLA Expanded VLA (Phase 1) Burial of fiber complete. Data transmission at 120 Gbps / station demonstrated…

6. 2005/7/13VLBA Plans & Options6 Formatted 120 Gigabits

7. 2005/7/13 – jdrVLBA Plans & Options7 VLBA Has Been Preoccupied with … [1] Transition to Mark 5 Recording [2] Development of Spacecraft Navigation And Severely Constrained by Limited Budget

8. 2005/7/13 – jdrVLBA Plans & Options8 [1] Transition to Mark 5 Recording [1] Transition to Mark 5 Recording Prerequisite for e-VLBI. Essential to Escape High Maintenance Costs … of tape system. Already committed: stopped buying most replacement parts two years ago. Expensive for Full-Time, Dedicated Array 10 stations / 128 Mbps mean rate / 30-day turnaround : 415 TB ; US$ 278 K. Current Status Will pass transition midpoint by end of August 2005. 9 station recorders (8 VLBA + GBT), of 12 total. 9 correlator playbacks, of 20 total.

9. 2005/7/13 – jdrVLBA Plans & Options9 [2] Development of Spacecraft Navigation Capability [2] Development of Spacecraft Navigation Capability Considered Best Option to Obtain Funding for Both... Mark 5. e-VLBI. Strongest case for (near) real-time analysis. Pilot Project Completed 2004/9/30 General approach: Observe using standard VLBA phase-reference mode. Process routinely in VLBA correlator. Results judged to be extremely promising by JPL navigation team. NASA/DSN invited NRAO to propose full development and validation program. NASA Unable to Fund Proposal … due to massive budget cut.

10. 2005/7/13 – jdrVLBA Plans & Options10 Spacecraft Navigation (continued) Cassini Mission Requested VLBA Observations … of Cassini, before & after flyby of Iapetus on 2004/10/17. … to reduce uncertainty of Huygens trajectory to Titan. Request received by NRAO on 2004/10/1 -- day after Pilot Project ended. Target-of-Opportunity proposal negotiated and written during 2004 e-VLBI Workshop in Makuhari. VLBA & GBT Also Observed Huygens Landing … but delivered recordings in conventional way. Interesting contrast to VLBA Spacecraft Navigation technique.

11. 2005/7/13 – jdrVLBA Plans & Options11 e-VLBI as Supporting Technique for Mark 5 Operations Rapid Media Turn-Around: 30-Day Target Generally achieved by VLBA stations in current operations. Non-VLBA stations in HSA / Global / Geodetic observations usually require fringe-searching, sometimes extensive. Eastern VLBA station(s) could join EVN e-VLBI fringe checks, to calibrate EVN clocks against VLBA’s GPS-based monitoring. Mauna Kea VLBA Station Poorly accessible for tape shipment; site tech overtime incurred. High-altitude operation suspected of causing failures. MK signals could be linked to Hilo – or Socorro – for recording.

12. 2005/7/13 – jdrVLBA Plans & Options12 Potential VLBA Fiber Connectivity C. Walker Study of Station Fiber Proximity Distances from VLBA stations to nearest known fiber --- 4 stations are within 1 km:BR / KP / MK / NL 4 are within 1-15 km: FD / HN / OV / SC 1 station is already connected to fiber: PT 1 station may have to be moved: LA National Lambda Rail Rio Grande Trunk Probably essential for practical e-VLBA correlation. Is it a current fact, or a plan?

13. 2005/7/13 – jdrVLBA Plans & Options13 Thank you