USNOVLBASupportMeetingNovember2020 < NM/Electronics

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Date: November 12, 2020

Time: 11:00 am Mountain, 1:00 pm Eastern
Phone: 434-817-6468 ext 228111#

NRAO: Jim, Walter, Justin
USNO: Nicole, Phil, Bruce, Chris, Andy, Stewart. Lucas, Megan,

VLBA Observations
Daily Observation Report (N-series)
- Due to a time crunch at USNO they are currently not doing a daily analysis of the N-series correlation results so there is no feedback report for August or September. Any problems like a lack of fringes will still be reported to NRAO when they're seen.
- Two reobservations in October due to data tests indicating failure and one rescheduled observation due to a hardware failure.
- Some observations in July were reported as having cable cal problems at PT, cause unknown. Due to the halt in daily analysis it's unknown if this has persisted. Was not seen in the few August runs they did analyze.
- Beginning November 1 SC was added to the daily N-series intensives making it a three station observation.
  - Potential future multi-station (~5 stations) intensives would probably not preempt other observations, and would therefore require a larger observing window than is currently present on the daily intensives.
  - We're encountering some problems with three station observations coming up short due to limitations of the SCHED software. In one recent instance only a 22 minute file was created! Moving the start time to an hour later finally allowed for the creation of a full-length file.
    - To try and alleviate some of these problems we could make changes to the key file used to generate the observation files. Walter Brisken has two suggestions:
      - geosrep could be reduced to 10, but the resulting schedule may sufer a bit.
      - geotries could be increased to 50, will take longer to generate files but that's not a serious issue.
- Tests have run on N-series vex files made using "VieSched ++" to see if it would run on the VLBA system. This would likely provide a solution to the problem of too-short files mentioned above.
  - First test file in August did not fringe. A second test in October failed due to hardware problems at PT. A third test ran on 10/22/20, was successful on all baselines. Some tweaks still needed.
Other Intensive Observations
- O-series test on HN-OV baseline
  - Will run simultaneous with the N-series observations but will not interrupt other observing.
  - HN suffered an azimuth wheel bearing failure on September 25 and was offline until October 9th.
  - Possible oscillation/tracking issue at HN recently detected, suspect an elevation encoder issue.
    - Only seen at low temperatures, hasn't been noticed since January.
    - Elevation encoder replaced while repair crews were on site for azimuth wheel replacement in early October.
- F-series characterization series on five of the VLBA stations every two weeks.
  - Project code for these observations is FYYDOY.
- P-series intensive observations roughly every other day on the HN-MK baseline
  - Project code for these observations will be PYYDOY.
  - Using the same setups as the other runs but duration is 1.5 hours instead of 1 hour.
  - HN suffered an azimuth wheel bearing failure on September 25 and was offline until October 9th. P-series observations resumed on the 12th.
- "Holiday" intensive observations at MK
  - Project code for these observations will be IYYDOY.
  - Will be substituting MK for Kokee on federal holidays in 2020.
- MK-WZ backup observation series
  - Project code for this observation will be QYYDOY.
  - Involves a new post-observing procedure for operators to copy the data to correlator in Japan.
  - Was restarted in late June due to the Ishioka station being unavailable, continuing through the end of calendar year 2020.
Post-Monthly Report Review for October
- No backlog from September that needed to be caught up in October.
- The request for October missed one F-series observation.
- US003 requested 16 hours in October but used none.
Pre-monthly request for December
- December request has not been received yet. Not sent around at NRAO, will check with M. Claussen.

Open issues
- A minor 'DiFX' release went out in October and will be installed on the VLBA correlator. A good fraction of the changes in this release are related to difx2mark4. USNO will stick with 2.6.1 for now and check out the changes to difx2mark4.
- USNO emails to ut1 list are not being forwarded along to other USNO people.
  - Mail is being blocked at the Dept. of Defense level. A possible fix is being tested.
- HN-OV baseline is more precise than any of the others USNO has data for, not sure why. With all the recent problems showing up at PT maybe switch around the stations involved in the N-series observations?
  - HN-MK actually looks most promising baseline rather than HN-OV. After current time crunch is over USNO will analyze which baselines will be best for future 3-station intensives.
- LA fiber install almost completed, should be finalized either today (11/12/20) or early next week.
  - Fiber line is capable of 10 Gbps but initially will be at 1 Gbps.
- USNO-NRAO contracts
  - USNO renewal of MK fiber support contract currently at NAVSUP and being combined with other support contracts.
  - Networking support contract being worked on, might involve changing some dates to spread out USNO contract renewals over different times of the year.
  - A follow-on to the correlator support contact is in place for six months.
- Transition to Mark6 recording system at VLBA is done, including 4 Gbps capability.
  - Tests for transitioning to the higher data rate, perhaps with C-band, will be considered. (Though C-band has ionosphere problems.)
- Data ingest of IVS data to NRAO/Socorro in support of USNO backup correlator operations has been lightly tested.
  - Desire to do a monthly test of the backup correlator by correlating a WZ-KK intensive.
  - Transfer of data from KK was demonstrated in September and again recently. WZ has not been successfully demonstrated yet.
    - ssh key information has been sent to WZ. A low data rate test has been successful.
    - Will attempt to do a test of the 11/16/20 intensive. USNO will need to establish access. Probably will be a high latency attempt, download the data first then USNO will try the correlation later.
- Possible issue raised with accessability of USNO data in the VLBA legacy archive. Any way to put in a request people who do access the data to properly credit USNO and limit access?
  - Probably not much can be done with legacy archive, new archive system will have more potential.Currently new data is going into both, sometime soon it will switch to only going into the new archive.
- USNO has interest in exploring the recently announced VLBA+Y3 observing mode. What would be needed to move forward on exploring this?
  - This is RSRO so an external proposal will be needed? A number of scheduling and technical issues are still being sorted out at NRAO.
  - How will this fall under the USNO's 50% VLBA time since this is not fully VLBA? Probably open skies instead.
  - A letter to Mark McKinnon expressing interest in doing this could get the necessary discussions started. Will also be brought up at next VLBA coordination meeting.
- (long-term issue) There's interest in having VLBA observe along with a VGOS session in "mixed-mode". But there's apparently some support problems with latest version of 'DifX' correlator software and VGOS, more technical discussions need to be held to determine what could be done.
  - Some discussion has happened, may not be as big of a problem as initially thought.
  - It may come up in an IVS OPC which is scheduled for mid-September.
    - No information from the IVS OPC yet.
- (long-term issue) New IVS session code naming structure
  - There is likely to be a change to format of the IVS "session code", but maybe not until later in 2021 or 2022. As the USNO works to make the VLBA intensives look like IVS sessions we want to discuss what impacts such a change might have on this effort. This particularly relates to the 'exper_name' in the .vex files.
  - Intensives are all now using the xYYDOY naming format (ie, N20001, O20001, etc)
  - New IVS codes will be similar to existing codes but perhaps slightly longer, for example "NYYYYDOYNN". USNO & Goddard have discussion about it, length will be more than six characters. NRAO has already used some seven character length codes (such as "N20014B") without it causing any problems.
  - Scheduling OMS program was tested, it will support up to at least ten characters for projects.
  - The Mark6 disk pack shipping/tracking program Packtrack has some problems with lengthy project codes but there are workarounds. This would primarily only affect the O, P and F-series observations which get correlated in Socorro.
- (long term issue) 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 and may have to wait until things return to normal.

Next meeting December 10.

-- JimOgle - 2020-11-09

Topic revision: r4 - 2020-11-12, JimOgle

NM/Electronics

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