• P-series has changed to fixed times/dates while Kokee is down and MK is substituting for it in some of the I-series intensives.
  
  • Continues into April.
  • Three runs in February missed; one due to weather, one due to human error, one due to software problems.
• NZ-Series runs approximately every three days.
  
  • BR cable/phase cal problem
    
    • Maintenance visit in late August 2023 at first seemed to have fixed the cable cal problem at BR, there was only one observation at the end of August and one in October that still had jumps in the cable cal but every other observation in September and October has looked okay. However, in November the cable cal problem began appearing again.
    • USNO reports that BR cable cal was less of an issue in March and April 2024.
      
      • VLBA has noticed an increase in cable cal jumps since then. They appear to occur around the same times each day, 2000 and 0800 UT. Site tech speculates late afternoon heat and overnight cooling is causing expansion and contraction of cables.
      • Seemed to lessen a bit towards the end of summer but colder temperatures seem to have fired it back up again.
  • SC began having a cable cal problem in June 2023. Still being investigated.
• Q-series intensive observations at MK run on weekends.
  • Two runs in February missed; one due to weather, one due to software problems.
• I-series "Holiday" intensive observations at MK, substituting for Kokee on federal holidays.
  • Also substituting for KK in some regular I-series intensives while their fiber is out.
  • No ETA on restoration of KK fiber, replacement is in the early site survey phase.
    • Repairs expected to start in March and finish in April.
      • Repairs expected to start March 17. Finished by May 1 hopefully.

• MK substituting for KK I-series and new schedule for P-series observations continued.
• One P-series observation was moved to avoid global session.
• UD020 for February was observed as part of the global session, GC040.
• February request had ten sessions for NZ but due to shorter length of February NRAO pre-monthly report dropped that to nine.

• .MK substituting for KK I-series and new schedule for P-series observations continues.

• MK substituting for KK I-series and new schedule for P-series observations continues.
  • Possibly last month if KK fiber repair is on schedule?

• V2 correlator status:
  • Tuesday 5-7pm (Eastern Time) Maintenance Window weekly patches continue, with weekly reporting to USNO at the conclusion of each patch.
  • Troubleshooting as requested to maintain functionality.
  • USNO and NRAO completed the RMF Validation step in December. Since then, USNO and NRAO have been addressing questions and findings of validator, security control assessor liaison.
• V3 correlator status:
  • Progress has been minimal due to effort on V2 RMF process, and RFP/costing requested by USNO.
  • NRAO is continuing progress toward milestone 3, software testing in Socorro on a two-processing host system using a representative dataset.
  • USNO has advised of change in information security requirements for its IT infrastructure and systems. NRAO obtained new quotes and presented updated costing and scope parameters to incorporate TAA-compliance at system level, air-gap build and support USNO/N6 in commissioning via a 2-part RMF process.
  • USNO is identifying supplemental funding and will prepare an updated Performance Work Statement for the V3 Correlator to formalize the changes via NAVSUP/NRAO CAP. Supplemental funding is expected in 2 tranches, first in FY25, and another in FY26.
  • NRAO thanked bidders for their feedback on requirements and efforts to find a performant solution. We also informed them that a revised RFP is anticipated since contact amendment is in place.

• VLBA e-transfer system
  
  • All non-VLBA stations for RDV169 were successfuly transferred from Haystack.
    • Correlation ran into some problems, not due to e-transfer.
  • RV170 is also being e-transferred.
• Data ingest of IVS data to NRAO/Socorro in support of USNO V2 correlator ("backup correlator") continuity of operations (COOP):
  • We will do a monthly COOP test of the V2 correlator by correlating a WZ-KK intensive. .
    • COOP test is using WZ-MK while KK's fiber connection is out.
    • Some miscommunication happened with the March COOP test; request asked for Monday March 3, NRAO responded in its March response that Mondays and Tuesdays have possible conflict with software development/testing on COOP and suggested Thursday March 6. No response from USNO to that request. USNO didn't ask where March 3 data was so NRAO went with the assumption that test was moved to March 6 but when contacted people at USNO were unaware of the move. Test was done on March 6 after USNO said they would be able to do the test.
    • Next COOP test scheduled for April 17.
  • MOA actually was that the VLBA correlator would be used for the COOP not the V2. Once eTransfer is in place that could be done.
    • e-transfer is in use now, time to revisit this topic?
  • Further use of the V2 correlator in the processing of P-series and Z-series observations has been proposed.
    
    • An eventual goal would be to see a demonstration of these being processed without the involvement of any DC-based USNO personnel.
    • Another goal would be processing bigger projects such as a 24-hour R4 observation.
    • Will be easier for VLBA to handle after the deployment of the e-transfer filesystem.
      
      • etc/etd will be the only transfer software initially supported by the e-transfer system.
      • Kokee will need to change to this software for the COOP tests. Wetzell has already switched to it..
        • Switch at Kokee delayed by their fiber outage.
    • Test correlations have been done on both P and Z series observations with the V2 correlator.
      • Storage space in the DSOC /datacopy areas is insufficient to hold data from a P series and a Z series at the same time.
        • More space will be available once e-transfer is in place.
        • Currently we are still using the datacopy areas for transfers from VLBA stations, procedures for using e-transfer area instead need to be developed.
      • Data transfer rates were exceptionally slow, probably due to using rsync because tsunami and etc/etd were not available to USNO users on gygax.
        • Will need to get USNO access to the new transfer software before further testing can be done.
• USNO would like to be able to check automatically if the V2 correlator is up or down but are unable to do so, can NRAO set something up for this?
  • Probably have to wait for e-transfer to be operational at NRAO due to internet security concerns.
  • Time to revisit this?
• Higher speed network connections to HN and MK opens the possibility of realtime correlation of intensives but neither Washington correlator nor NRAO set up to do it yet.
  
  • Blocking issue for NRAO is mostly network speed into the correlator.
    • Initial attempts at realtime correlation of VLBA data could begin soon. There will be some limitations - VLBA stations only, limited to observations that record at 512 Mbits/sec or less and NRAO may need some help from USNO in determining sessions, creating files and looking at the output. These observations would still record to Mark6 disk packs but if USNO intensives were used they would not record data to the DBS units.
      • Contact person at USNO to assist on this needed. No update.
      • Q from USNO if this was realtime or near-realtime correlation, it is in realtime.
  • USNO not really set up for realtime with correlator design and workflow, and no real plans to do it in the near future. Wait for v3 correlator.
• Replacements of the Xcubes with DBS units
  
  • New software will ultimately cause a change in the naming structure of data files and PFB (Mark5B) data format will no longer be supported, instead it will be converted on the fly to VDIF format.
    
    • Software changes will need further testing before deployment and first iteration of the updates may not change naming structure of data files or include the PFB->VDIF conversion.
    • Low priority, won't happen until after eTransfer and v3 correlator.
• Is it possible to reduce the latency on 24-hr geodetic USNO-only sessions, with a goal of a latency between the completion of observation to analyzed result under 7 days?
  • E-transfer not practical at this time so expedited shipping of disk packs is needed.
  • Might be limited to just attempting it for one of the two UD011 observations per month.
  • Record of time to correlation:
    
    • first year of observations (UD011 AA - AR) average time was 9 days. (Specifics can be found in minutes of previous meetings.)
    • second year of observations (UD011 AS - BQ) average time was 12 days counting all observations, just counting the one observation a month we put a rush on the disk pack shipping the average time was 9 days.
    • third year: UD011 BR - 18 days, UD011 BS - 8 days, UD011 BT - 21 days, UD011 BU - 13 days, BV - 27 days; BW - 15 days; BX - 23 days; BY - 13 days; BZ - 20 days, CA - 17 days, CB - 13 days, CC - 17 days, CD - 17 days, CE - observed March 10
      
      • note: VLBA correlator was experiencing a networking related slowdown September through November (BT through BX) which lengthened correlation times.
• Next DiFX release (2.9) - Slow development continues.
  
  • testing is likely to start soon but there's a patch that needs to be put in concerning Mark4 and that hasn't happened yet.
  • there are also some issues with Mark6 units as well.
    • Mark6 issue resolved, no real blockers at this time.
• VEX2
  • Vex2 standard will cover missing tuning information that SKED and VieSked++ aren't able to include.
    • This information will still be required but VEX2 will have a space for it so manual editing won't be needed.
    • USNO has been sent vex2 samples, will have them send NRAO a file to test and make sure it works.
  • Things are okay right now with standard USNO setups and observations, could become an issue if USNO starts using non-standard setups in new observations.
  • Some testing of VEX2 has begun at NRAO.
    • Some diagnostic observations have switched to vex2 for testing purposes.
    • Seems to be okay for some regular observing and pointing tests. Some modes may still need testing.
    • Sched 12 is out, NRAO will switch to using vex2 internally after that. Vex 1.5 will remain supported but once VNDA is installed and running in 2026 NRAO will probably transition fully to vex2.
      • Vex2 transition for regular observing likely to happen before VNDA is installed, so probably sometime later this year.
• Installation of new GPS receivers at VLBA sites.
  
  • Antennas have been installed at all VLBA sites.
  • installation of first receiver was done at FD in November.
  • PT and OV had receivers installed but not turned on yet.
    • PT receiver turned on in January.
  • As of late February all stations had receivers installed except for SC and MK, but only PT and OV have been activated.
• Mixed mode correlation
  • 2025 RDV sessions will have at least one VGOS station in mixed mode, USNO might need to assist NRAO in correlating them.
  • First 2025 RDV session is January 8, 2025, RV169.
  • Correlation of RV169 done this week.. Problems with data from one station, unrelated to e-Transfer.
  • RV170 from February has been downloaded.
• VLBA planned to start upgrading its correlator from RHEL7 to RHEL8 in January 2025.
  
  • USNO still needs to use DiFX 2.7.
  • Upgrade progress - Mark6's need some hardware updates before they can be upgraded to RHEL8.

Long term issues

• New IVS session code naming structure change for intensives. (moved from open issues)
  
  • Problems encountered with the longer project codes:
    
    • Longer project codes not supported by all IVS stations so not all intensives will change to a longer code.
    • DiFX did have some project code length limitations, a change went into DiFX 2.8 .
      
      • USNO not using DiFX 2.8 yet. They can correlate with 2.8 but fringing doesn't work.
    • NRAO's Mark6 disk pack shipping/tracking program Packtrack has some problems with lengthy project codes. This would only affect any intensives which get correlated in Socorro off of disk packs, but currently there are none.
• .Peculiar delays - VLBA has a delay compared to Kokee that perhaps should be checked out, maybe put some VLBA stations into a KK observation as tagalongs?
  • Walter reached out to some people, says it looks like it would be a bigger effort than anticipated.
    
    • Possibility of adding KK to an RDV observation instead raised..
      • KK will be in the April 2024 RDV observation so could get data from that.
        • RV165 observed April 24. Has been correlated.
        • After USNO (or NASA?) does analysis a copy of the clock offsets can be provided to VLBA for comparisons.
          
          • Analysis finished, but didn't include VLBA stations so still need to do that and get the info to NRAO.
        • Kokee does have a different maser compared to last time VLBA correlated with them, might have an effect?
    • VLBA thinks it will have to wait until after all ten stations have received new GPS units (and they're all in use).
    • Moving to VNDA will also change VLBA delays slightly, so it'll probably have to wait until after that's in place as well.
      
      • The RV165 clock offset data would be useful for a before and after comparison, but it would not be used to adjust the VLBA offset. A second observation like RV165 would be needed so we could make the comparison.

• 600 Mbps minimum at each site
• 1 Gbps at PT, KP, OV, NL. FD
• 5 Gbps at HN
• 10 Gbps at LA,BR, MK
• 600 Mbps at SC (download up to 400 Mbps) - possibility it could be going up to 1 Gbps