1. VLBA Correlator Interfaces for VSOP-2
Mark 5 / VLBA Correlator Topics
2006/2/23
VLBA Correlator Interfaces for VSOP-2
Jon Romney
NRAO, Socorro
VSOP-2 Tracking Meeting
Madrid / Yebes
2007/2/19-20
2007/2/19-20
J. D. Romney

2. Essential Initial Digressions
The NSF Senior Review
Panel convened by NSF Division of Astronomical Sciences.
Report released 2006/11/3.
Primary goal: “redistributing roughly $30M of annual spending” from existing facilities, to invest in new facilities.
Primary recommendation on VLBA: “to seek assistance in operating the VLBA for a finite time from the international user community and, perhaps, also from NASA and the Japanese [ISAS] where there is a strong synergy with its missions.”
2007/2/ – jdr
VSOP-2 Tracking Meeting Madrid/Yebes

3. VSOP-2 Tracking Meeting Madrid/Yebes
The NSF Senior Review
NRAO Responses to SR Report
Concentrate on delivering high-profile science, in areas consistent with NSF Astronomy’s mission.
Seek non-NSF support for ~33% of $6M annual operational cost, at rate corresponding to ~$2k/hour.
Relevant options for VSOP-2: NASA and/or ISAS.
May require reducing scheduled observing time.
Upgrade VLBA’s sensitivity to expand range of science it can address.
2007/2/ – jdr
VSOP-2 Tracking Meeting Madrid/Yebes

4. The VLBA Sensitivity Upgrade
22-GHz Receivers
Replacement of LNAs.
4-Gbps Data Path
Replacement of all equipment downstream from IFs.
New wideband Sampler/Filter module.
Compatible with VSOP-2 channelization.
New wideband Recording system.
Disk-based; compatible with existing Mark 5 module pool.
New Correlator.
WIDAR- or software-based.
Planned upgrades to existing playback interface abandoned.
2007/2/ – jdr
VSOP-2 Tracking Meeting Madrid/Yebes

5. VLBA Correlator Interfaces
Discussed Here in Context of New Correlator
Existing correlator incompatible with VSOP-2 channelization; limited to 256 Mbps (for > 10 stations) without PBI upgrade.
Observation Data (Input)
1- (2-,4-) Gbps data rate OK; subject to media pool constraints.
Recorded on Mark-5-standard disk modules.
Format TBD: Mark 5A, 5B, or (hopefully) more advanced wideband system.
Prompt delivery requirements same (probably even more stringent) as for VSOP -- i.e., “Bologna Rules”.
2007/2/ – jdr
VSOP-2 Tracking Meeting Madrid/Yebes

6. VLBA Correlator Interfaces (Continued)
Orbit Data
Generally, same requirements as for VSOP.
Accuracy specifications TBD, possibly depending on correlator.
Format preferably same as JPL orbit kernels used for VSOP; could be changed for a different OD organization.
Logs
New correlator an opportunity to move to new log format.
Hope to develop new global standard.
Prompt delivery requirements same as for VSOP.
2007/2/ – jdr
VSOP-2 Tracking Meeting Madrid/Yebes

7. VLBA Correlator Interfaces (Continued)
Time Correction Files
Presumably also required for VSOP-2.
No known reason to change VSOP format.
GPS Offset Files
Recommend merging into new Log format.
Visibility Output Data
TBD, as appropriate for post-correlation analysis system(s).
2007/2/ – jdr
VSOP-2 Tracking Meeting Madrid/Yebes

8. VSOP-2 Tracking Meeting Madrid/Yebes
Thank you
2007/2/ – jdr
VSOP-2 Tracking Meeting Madrid/Yebes