• P-series runs every other day.
• Z-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.
  • SC began having a cable cal problem in June 2023. Still being investigated.
• Q-series intensive observations at MK run on weekends.
• I-series "Holiday" intensive observations at MK, substituting for Kokee on federal holidays.

• 48 of the 72 hours of backlog from March were caught up with in April but unfortunately 48 hours of observing in April were not observed so we still have 72 hours of backlog to make up in May.
• Ten Z-series observations were requested, nine ran.
• US006 requested 12 hours, only used 4.63 hours.
• UF006 requested 24 hours, only used 19.23 hours.

• Nothing unusual noticed in the request.
• PT will be out the week of May 13 - 17 for replacement of an elevation bearing.
• HN may be out for the final week of May to have a new backup generator installed. It might end up happening in early June though due to scheduling issues with local contractors.

• Nothing unusual noticed in the request.
• SC rail repair will hopefully happen in June, site would be out for a week at least.

• KK will be down September 3 through at least mid-October and possibly through November or December.
  
  • USNO would like to use MK for the Monday-Friday Int1 sessions while Kokee is down.
  • USNO will be discussing it further with Haystack and Kokee June 11.
  • VLBA data analysts expressed concern over getting the I-session files in a timely manner because they need to be manually edited before they will run on MK and in the past have often arrived on the late side.
  • VLBA scheduler expressed concern over getting 24-hour observations scheduled (USNO and open skies) as we try to avoid having them interrupted by intensives, especially multiple ones (currently the P and Q-series runs), as these projects usually require MK. Having M-F intensives at MK would severely reduce those scheduling possibilities.
• S-band performance issues
  • RFI has been increasingly affecting S-band observations for VLBA and VLA.
  • Does anyone at USNO have time to work with NRAO on looking into this issue?
    
    • USNO will be in touch with Justin.
      • Justin's been testing things with the P-series setups.
      • Test results not promising for astronomy observations in S-band.
• NRAO login accounts for new USNO analysts
  • Accounts have been set up, most issues resolved.
    
    • Marc has been issued credentials but not clear if he's managed to successfully log in yet.
      • Update on Marc? - should be resolved but USNO will double-check.
      • Should be okay.
• Data ingest of IVS data to NRAO/Socorro in support of USNO backup correlator operations:
  • We will do a monthly test of the backup correlator by correlating a WZ-KK intensive. .
    
    • Future tests: May 15 (changed, was originally the previous week), June 5, July 10, August 14, September 4, October 1, November 6, December 4
  • Further use of the backup correlator in the processing of P-series and Z-series observations has been proposed.
    • Eventual goal would be to see a demonstration of these being processed on the backup correlator without the involvement of any DC-based USNO personnel.
    • Some testing might involve using the VLBA correlator rather than the backup correlator.
    • Will be easier for VLBA to handle after the deployment of the e-transfer filesystem later in 2024.
      • etc/etd will be the only transfer software initially supported by the e-transfer system.
      • Kokee will need to be asked to change to this software for the COOP tests. Wetzell has already switched to it.
    • This will hopefully transition into the ability to do bigger projects for USNO at DSOC such as the 24-hour R4 observations.
    • Testing has been done on both P and Z series observations with the backup correlator.
      • Storage space in the datacopy areas is insufficient to hold data from a P series and a Z series at the same time.
      • 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 backup correlator is up or down but are unable to do so, can NRAO set something up for this?
    
    • Might have to wait for e-transfer to be operational at NRAO due to internet security concerns.
      • E-transfer hardware is at DSOC, no ETA on when it will be ready.
        • external facing server has not been certified yet but hopefully by next month there will be news.
          
          • Waiting on IP addresses to be set up.
        • internal testing of e-transfers have so far been successful.
• Replacements for the Xcubes (called Data Buffer Server, DBS) started rolling out but stalled.
  • Remaining installs were completed on May 2.
    
    • OV was found to not have all of its software properly installed and a Z-series observation did not get recorded to the DBS. Should be fixed now.
  • New software will ultimately cause a change in the naming structure of data files and PFB data format will no longer be supported, instead it will be converted on the fly to VDIF format.
    
    • Software changes won't happen immediately after the Xcubes are replaced and first iteration of the software changes may not change naming structure of data files.
      
      • Will need further testing before deployment. Software might roll out before VNDA but the conversion of PFB to VDIF may not happen until after.
• Higher speed network connections to HN and MK opens the possibility of realtime correlation of intensives.
  
  • Neither Washington correlator nor NRAO set up to do it yet.
    
    • Blocking issue for NRAO is mostly network speed into the correlator. This will probably be another thing that has to wait for the e-transfer hardware to be installed.
    • USNO made some upgrades to their correlator's networking, up to ~2.5 Gbps on an individual transfer, but still not quite fast enough to do realtime transfers. Further upgrades are being worked on.
• 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 really practical at this time so expedited shipping of disk packs is needed.
  • Might be limited to just attempting it for one of the two 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.)
    • UD011 AS 9 days, UD011 AT 11 days, UD011 AU 6 days, UD011 AV 12 days, UD011 AW - 6 days, UD011 AX - 12 days, UD011 AY - 9 days, UD011 AZ - 15 days, UD011 BA - 7 days, UD011 BB - 17 days, UD011 BC - 8 days, UD011 BD - 20 days, UD011 BE - 8 days, UD011 BF - 18 days, UD011 BG - 16 days, UD011 BH - 13 days, UD011 BI - 9 days, UD011 BJ - waiting on disk packs
• New IVS session code naming structure change in 2023-24
  • On NRAO's side, the Mark6 disk pack shipping/tracking program Packtrack has some problems with lengthy project codes but there are workarounds. This would only affect any intensives which get correlated in Socorro off of disk packs, currently there are none.
    • Plans are being developed in NRAO to overhaul Packtrack to cover things such as longer project codes and e-transferred data.
    • Packtrack will need to be rewritten to work under more up-to-date versions of Linux OS before other changes can be implemented.
      • This has been postponed to FY25 due to a lack of resources.
  • IVS will continue to use the existing shorter naming structure through all of 2023.
    
    • USNO notes they are using the longer naming structure in correlation and archiving of data but will probably hold off on using it for observations until after IVS makes the switch.
      • No firm date yet for IVS to make the switch, still working on software.
        • I and Q sessions will not change, P and Z sessions will. Some other USNO observations will also switch.
          • Actually I and Q names will probably change first. Goal is to be fully on the new naming convention before FY25.
          • Or P and Z sessions might be first depending on software developments. Maybe start using longer codes July 1st?
  • USNO sent some representative "new style" IVS observing codes for NRAO to run through its software looking for any unexpected problems.
    • Test NT2022224 AAA ran on Aug 12, 2022.
    • DiFX does have some project code length limitations, a modified trunk version of has been made for the correlation and the change will hopefully go into the next release (DiFX 2.8,which has now been released.)
      • There is an issue with Mark4 data, it does impact some USNO data (though not VLBA data).
      • USNO not using DiFX 2.8 yet. Also believe that 2.8 has a problem with mixed mode?
    • SCHED also has some project code length limits but SKED and VieSched ++ may not?
    • Some minor issues were found with archiving of data and some automated emails truncated the longer project code.
      • Xcube/DBS recording software does look at project codes to determine to record or not, will need to be addressed.
        • VLBA will run a test with a P or Z series using the new longer project code style to see if the Xcube/DBS handles it correctly.
          • Test has not been run yet.
• Can some kind of acknowledgement be added to USNO data in the NRAO data archive indicating USNO's involvement?
  • Learned in mid-April that this has been pushed back to development cycle AAT 4.4.1 which is expected out in November.
• Possible changes coming to login accounts on DBS modules, moving to a group USNO account rather than using individual accounts?
  • No ETA on if/when group accounts would be instituted.
  • NRAO is trying to move away from group accounts for cybersecurity reasons so things may remain with individual accounts.
• USNO-NRAO contracts:
  
  • V3 DiFX (correlator upgrade) contract awarded in March 2023.
    • Biweekly build status meetings between NRAO and USNO are being held Wednesdays.
    • Some issues in installing DiFX 2.6.1 and its reliance on Python2 but it's in progress (think it's been solved.)
• USNO reported users' passwords not working on some machines.
  • According to computing department, password changes do not propagate from computers in the DSOC to computers at the VLBA stations, each machine needs to be individually updated.
  • Computing department recommends USNO users switch to using ssh keys instead of passwords to avoid this problem. Instructions on how to do this are supposed to be forthcoming.
    • Have not received any instructions from NRAO yet.
      • No. Can't put ssh key on machines they don't have a password for. Key is on MK DBS so just needs to be copied from there.
      • Ticket will be filed with NRAO helpdesk.
      • No update yet.
        • Appears to have been resolved for Sara and Bruce. Rest will check out and see if they can get in or not. Looks resolved for now.
• Missing baseline delays seen in some USNO K-band observations. Possible correlator issue? Not sure where it's happening. USNO's using CASA. Walter & Justin think this might have been reported by other CASA users. Seth will submit a CASA helpdesk ticket. Chris DiLullo has also seen some issues with CASA. Will set up a meeting with Justin to see how to proceed with reporting these issues.
  • Meeting has happened. Also seen in some C-band observations. Justin will be looking into it.
  • It's been seen in an odd observation so maybe it's due to that. The UF006's it was seen in may have been a one time problem?
  • Probably doesn't need to be tracked here.

Long term issues

• Next DiFX release (2.8.2?) - a blocker issue for moving on to the next version for NRAO and probably USNO too has been resolved so moving to testing phase of the next release candidate can happen. Meetings for that will begin next week, probably take a couple months to sort everything out. Will be first release of it through GIT, procedures haven't been established for that yet. USNO input should be directed to Walter. August probably the earliest it could be released.
• NRAO will at some point begin doing data downloads during and after observations and this could conflict with USNO's own data downloads of the intensives.
  • Currently NRAO is only regularly doing data downloads once a week during a post-maintenance day test. Sometimes this does come shortly after a Z-series observation during the night.
    • USNO has not noticed any problems with their data downloads even when this has been the case.
  • Data downloads are also being done during the Z-series and P-series observations for realtime fringe checks, but this ends when the observation does so would not interfere with the following data downloads by USNO.
• There's interest in having VLBA observe along with a VGOS session in "mixed-mode".
  
  • First IVS needs to move some correlation off to other correlators and then they can start considering adding more stations like VLBA to the VGOS observations.
    • Not ready to include VLBA yet. Still issues within IVS and mixed mode to address first.
    • Some mixed mode issues may have been resolved.
    • Might add some VGOS stations to RDV observations to see how that works, VLBA correlator should be able to handle it
• .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 so comparisons can be made. 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 raised..
    • KK will be in the April 2024 RDV observation so could get data from that.
      • RV165 observed April 24.
      • After USNO (or NASA?) does analysis a copy of the clock offsets can be provided to VLBA for comparisons.
      • Kokee does have a different maser compared to last time VLBA correlated with them, might have an effect?
  • NRAO might wait until after new GPS receivers get installed on array.
    • Seven antennas have been installed so far - NL, FD, LA, PT, OV, KP, SC, BR.
      
      • Remaining antenna installation dates: HN - week of May 13, 2024, MK - June 2024.
      • No firm ETA on GPS receiver installations, hope is first one will be installed by July 1.
      • Move this out of the peculiar delays section.
• USNO and IVS partners have challenges with creating VLBA-valid VEX files with the SKED and VieSched ++ software packages.
  
  • Tuning VLBA at certain frequencies requires the additional commented information, it's not found in standard VEX setups/catalogs.
  • What is the plan, if there is one, for removing the need for the additional information required by the VLBA?
    • VEX2 standard will cover the missing information for VLBA, though the scheduling software used will still need to have the right setups information.
    • Probably 2024 before VLBA might switch to using VEX2, hopefully before 2025.
    • 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, pointing and other modes still need some work.
      • No timeline for migrating to VEX2 yet but progress is being made.

• 200 Mbps minimum at each site
• 1 Gbps at PT, KP, OV, NL. FD will be upgraded to 1 Gbps in June
• 5 Gbps at HN
• 10 Gbps at LA,MK; BR should be upgraded to 10 Gbps soon (might have happened last week, waiting for confirmation)
• 600 Mbps at SC (download up to 400 Mbps)