C212A

Data completness

• Ef: missed scans: No0038, No0039, No0041, No0042, No0046, without comments in the log.
• Mh missed scans: No0001
• Ys: No0008 - No0014 corrupted data files
• Ky: File /data/c212a/ky/c212a_KVNYS_274071501.vdif VDIF summary failed with return value -5
• Kt: Kt: File /data/c212a/kt/c212a_KVNTN_274070001.vdif VDIF summary failed with return value -5

NOEMA: LCP time shift

Timeserver on one of the polyfix units was not running leading to a timeshift between LCP and RCP in the beginning of the session including the fringe test. The issue was fixed on DOY 274  09:51:40.0 UT. The issue was fixed from scan No0193 onwards.

According to the NOEMA staff the issue should introduce integer second offsets of unknown value between the  LCP and RCP data streams. An extensive fringe search was carried out with integer second clock offsets between -20 and +20 seconds. For scans No0001 - No0018 fringes were found at -9s offset. The time stamps of the corresponding VDIF files were shifted accordingly and fringes were found. For the following scans no matching time shift could be found and the LCP data was discarded:

No0019 - No0030
No0032, No0033, No0035 No0036 No0038 No0039
No0154 No0158 No0163 No0164 No0168 No0173 No0177 No0178 No0183 No0187

GBT: corrupted data

Issue: Strong GBT fringes in LCP found but no detection in RCP (tested on scans 189 and 191).

Conclusion: (even) RCP threads apparently have been configured with the wrong thread IDs (odd LCP threads) for some portion of the session. This leads to duplicate threads even thread IDs. The extended header carries no informaton that permits to separate the correct from the incorrect threads. Even though LCP correlation has shown fringes it consists of a mixture of LCP and RCP threads. This is also reflected by the fairly large SNR in the LR cross correlations.
Problem seems to have been fixed in part c212b from scan C212B_GB_No0631 onwards. All scans prior will have to be discarded.

Diagnostics:

mark6-06 INFO  VDIF multiplexing statistics: nValidFrame=153 nInvalidFrame=0 nDiscardedFrame=0 nWrongThread=18421482 nSkippedByte=0 nFillByte=0 nDuplicateFrame=0 bytesProcessed=92697667320 nGoodFrame=38 nCall=8661
mark6-06 INFO  VDIF multiplexing statistics: nValidFrame=9938486 nInvalidFrame=0 nDiscardedFrame=359095 nWrongThread=153 nSkippedByte=0 nFillByte=0 nDuplicateFrame=8851360 bytesProcessed=92697667320 nGoodFrame=2482554 nCall=23029
mark6-06 ERROR  One or more wrong-threads were identified.  This may indicate a correlator configuration error.
mark6-06 ERROR  One or more wrong-threads were identified.  This may indicate a correlator configuration error.
mark6-06 ERROR  One or more duplicate data frames (same time and thread) were found.  This may indicate serious problems with the digital back end configuration.

Residuals

FITS completeness (pclist)