• P-series was changed to fixed times/dates while Kokee was down and MK substituted for it in some of the I-series intensives.
  
  • Continued to June 12, after the I-series observations resumed at Kokee the P-series remained with fixed dates but with more flexibility as to when they ran in relation to the I-series (still fixed times in relation to the Q-series observations.)
• NZ-Series runs approximately every three days.
  
  • BR cable/phase cal problem. Comes and goes, leading theory is thermal expansion and contraction of cables.
  • SC also has a cable cal problem but is slightly different in effect and doesn't seem to be due to thermal issues like at BR.
• Q-series intensive observations at MK run on weekends.
• I-series "Holiday" intensive observations at MK, substituting for Kokee on federal holidays.
  
  • Substituted for Kokee in some I-series observations until their fiber was replaced, ended on June 12.
  • There will be another period in the future where Kokee will be down again, some signal change and receiver upgrades, but no dates yet. November?

• MK substituting for Kokee I-series and new schedule for P-series observations continued until June 12.
  • Six requested I-series observations canceled.
  • Request was missing one I-series substitution observation, I25160 on June 9.
• Global observation GC040C substituted for UD020 this month.
• P2025158 was canceled because it would have interrupted a global observation.
• One extra NZ session observed.

• .Request from USNO initially asked for fifteen I-series observations. After Kokee came back this was reduced to one, the normal holiday substitution (July 4).
• A late addition of an I-series observation was added for July 17 due to additional fiber work at Kokee.

• looks pretty straightforward.

• 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 reviewers, as well as remediating new issues.The final authorizing official returned comments on June 4, and NRAO provided artifacts to address issues in its purview the same day. No further updates in June.
  • NRAO ordered QTY 5 drives for direct ship to USNO to augment spares on hand; these were delivered to USNO on June 12.
  • NRAO is investigating a few issues since late April/early May - power supply faults (test) and a kernel on one MD node (production). The latter issue was flagged in a STIG scan by USNO in early June; a coordinated repair is planned for July 15 with participation from both USNO stafff on site (performing an image backup to external drive) and NRAO stafff remotely (modifying the kernel, testing.)
• V3 correlator status:
  
  • NRAO has completed milestone 3, software testing in Socorro, and is completing reports documenting the results for delivery to USNO.
  • USNO delivered an Updated PWS to NRAO; however, additional changes in requirements and deployment process were briefed by USNO to NRAO in late June. A no-cost Extension to the contract, extending PoP to end of August, has been executed. NRAO is preparing an updated proposal to USNO according to most recent discussions and understanding of final requirements.

• USNO reports detecting a drift in MK baselines beginning mid-2023 and still happening.
  • Approximately 0.1 microsecond per day drift, works out to about 0.25 cm/year.
  • There was a major maintenance visit to MK in May 2023 during which the dichroic panel and antenna panels damaged by an ice storm in 2022 were replaced. Only other major work done in 2022 at MK was the replacement of an elevation motor in April.
  • It's seen in the Z/NZ series but not P-series? So maybe a correlation issue rather than with MK itself. Possibly seen in Q-series as well. Quick look at GPS data doesn't indicate a physical movement of the station.
  • Update?
• VLBA e-transfer system
  
  • RDV observations having non-VLBA stations e-transferred.
  • Direct transfers have worked, bypassing need for some stations to go through Haystack. Efforts continuing to add more stations.
  • Bonn has successfully pulled GMVA data from DSOC.
  • Anthony Sowinski PoC for NRAO.
• 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. .
    
    • July test will be on July 17.
      • Due to additional fiber work at Kokee this will be done with MK-WZ.
    • August test on August 7.
  • 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?
      • Different DiFX versions are in use, some prep work would be necessary. A larger discussion is needed.
  • Further use of the V2 correlator in the processing of P-series and Z-series observations has been proposed.
    
    • Would need to use e-transfer.
    • 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 other intensives and bigger projects such as a 24-hour R4 observation.
      • etc/etd will be the only transfer software initially supported by NRAO e-transfer system.
        • For intensives, Wetzell has switched to using etc/etd, Kokee change was delayed due to fiber outage.
        • Kokee likely to be a lot of work involved in making the switch due to an older OS being used there.
    • Test correlations have been done on both P and Z series observations with the V2 correlator.
      • Existing 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.
        • Moving to eTransfer would also get the procedures off gygax which isn't really suitable for it.
• USNO would like to be able to check automatically if the V2 correlator is up or down but are unable to do so.
  • Will probably need to be handled via the e-transfer system due to internet security concerns.
  • If we switch to using VLBA correlator instead of v2 as per the MOA it would eliminate the need for this.
• 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.
    • Now that e-transfer is working, should be consider trying it with UD011?
      • NRAO will put it on target list, would need to coordinate the download so as not to interfere with any realtime correlation observations.
      • Will be discussed in an NRAO e-transfer meeting July 30.
  • 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 - 10 days, CF - 13 days, CG - 14 days, CH - 13 days, CI - 17 days, CJ - 14 days, CK - 14 days
• Next DiFX release (2.9) - Slow development continues.
  
  • testing underway., target release date ???.
    
    • One issue involving VGOS data in HOPS package still being worked on, a workaround is in place. A new version of HOPS is expected to resolve the issue.
• 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.
      • NRAO has received samples, no test file yet.
  • 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.
    • Sched 12 is out, NRAO has switched to using vex2 internally.
      • Vex 1.5 will remain supported but once VNDA is installed and running in 2026 NRAO will probably end supporting v1.5 after a year.
      • Should start a test phase on USNO-provided vex files with vex2 now rather than later.
        • Problems reported by USNO with fourfit and vex2.
        • vex2 not supported by the mark4/HOPS data path? This and fourfit might be the same issue?
        • for the immediate future the vex 1.5 files can be used to avoid the fourfit and mark4 issues.
• Installation of new GPS receivers at VLBA sites.
  
  • Receivers have been installed at all sites but are not in use yet.
    • All stations except LA have been seen to transmit data but it's not usable by NRAO yet.
    • Some sites are experiencing overheating problems in the new GPS receivers.
    • Also waiting on firmware updates to address using them for timing purposes.
• Mixed mode correlation
  • 2025 RDV sessions will have at least one VGOS station in mixed mode, USNO needs assistance NRAO in correlating them. Maybe contact Haystack or Bonn?
  • Have tried mixed-mode correlation starting with RV169 but no success as of yet.
• USNO asked about getting CASA to read pulse cal data the way AIPS does, it would help with their imaging efforts on weak astrometry targets at higher frequencies.
  • This is on the CASA developer's target list but low priority.
• 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 VLBA playback units can be upgraded to RHEL8.
    
    • First testing of new hardware on one Mark6 unit was successful, hardware for remaining upgrades has been ordered.
    • Hardware has arrived, upgrading of Mark6 units has started.
      • Slight delay arose, some of the new ordered hardware proved incompatible and will need to be exchanged.
      • Replacement hardware has arrived, upgrade of first two playback units is in progress.

Long term issues

• Realtime correlation of intensives
  • Fast network connections at HN and MK make it theoretically possible but neither NRAO nor USNO are set up at the correlator end to do it yet.
  • NRAO could attempt this but there will be some limitations - VLBA stations only, limited to observations that record at 512 Mbits/sec or less and NRAO would need help from USNO in determining sessions, creating files and looking at the output.
  • An additional consideration is that while these observations would still record to Mark6 disk packs they would not record data to the DBS units so would not be easily downloadable should the realtime correlation not work.
  • USNO would have to wait for the v3 correlator before they could start planning for realtime correlation.
• DBS software changes
  • New software on the DBS units 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 will need 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 v3 correlator.
• New IVS session code naming structure change for intensives.
  
  • 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).
      • Prioritization of this and other lingering issues should be considered once we can start looking at this again.
    • 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