Table of contents
Version from 11:42, 20 Feb 2026
MJ008 Correlation Report
General information
- Track of the 3mm project MJ008 without Europe
- In-beam phase referencing (Sgr A* - IRS 7) where stations observed on a P-Half position between the two targets.
- Session info: http://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/
- Session feedback: https://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/sessions/apr25/feedback_apr25.asc
- ANTAB and log files are available at
- Station feedback:
- ALMA and GBT were out and essentially did not observe this track
- Although ALMA observed the first scan (No0072 on 1741-038; no fringes) they then stopped on a technical fault
- GBT notes that they "did not observe c251a and mj008". Their Mk6 recordings expectedly produced no fringes.
- FD and PT receivers were warm, KP mostly(?) stowed due to weather
- DiFX v2d has two addPhaseCentre=... statements which form the required additional phase centers on Sgr A* and IRS 7 away from the P-Half telescope pointing position.
- Scans that got scheduled on the targets directly (not P-Half) had the source names REALSGRA and REALIRS7.
- Source names for the additional phase centers around P-Half are SGRA_P and IRS7_7.
Status
| what | date |
|---|---|
| Prepared DiFX setup for production correlation | 18.02.2026 |
| Full-track correlation v0 finished. Fringes to more stations. Revised VEX. | 20.02.2026 |
| Production correlation v1 started | 20.02.2026 |
Fringes
| Station | Code | Fringes | Plots | Comments |
|---|---|---|---|---|
| ALMA | no | only one "valid" scan, but it has no fringes | ||
| GBT | no | did not observe, has Mk6 recordings, but (as expected) they do not produce fringes | ||
| APEX | yes | No0105 | APEX-VLBA_FD fringes | |
| VLBA | partly | No0072 | weak fringes only; BR FD OV KP LA, and in one scan PT, none with NL | |
| No0105 | ||||
| No0175 | ||||
| No0201 | ||||
Notes
Stations that actually joined the test were: VLBA_BR, FD, PT, KP, LA, OV, NL, APEX. Out of these, NL produced no fringes. Others produced weak fringes and in just some scans.
Overall the intra-VLBA fringe SNRs are surprisingly low. In some cases the SNR over the course of a scan has strong dips as if from wind of other telescope movement. In addition, unlike in c251a c251b, the VLBA stations are not in time and start a few seconds late on every VEX scan.
The one and only potentially "valid" scan from ALMA produced no fringes. Hence ALMA was removed from the production correlation.
The GBT notes say they skipped this track. There are nevertheless GBT Mark6 recordings for the entire track, for some reason, but they did not produce fringes. Hence GBT was removed from the production correlation.
For the in beam phase referencing, the DiFX v2d definition of phase centers around the fake midpoint source P-HALF is:
SOURCE P-HALF {
# VEX SGRA ra = 17h45m40.0317460s; dec = -29d00'28.272280"; ref_coord_frame = J2000;
# VEX IRS7 ra = 17h45m40.0340570s; dec = -29d00'22.821530"; ref_coord_frame = J2000;
# Note: despite the ':' syntax below, the v2d units are RA hms and Dec dms
addPhaseCentre = name@IRS7_P/RA@17:45:40.0317460/Dec@-29:00:28.272280
addPhaseCentre = name@SGRA_P/RA@17:45:40.0340570/Dec@-29:00:22.821530
}
Post-Correlation checks
Residuals
FITS completeness (pclist)
Version as of 13:22, 20 Feb 2026
MJ008 Correlation Report
General information
- Track of the 3mm project MJ008 without Europe
- In-beam phase referencing (Sgr A* - IRS 7) where stations observed on a P-Half position between the two targets.
- Session info: http://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/
- Session feedback: https://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/sessions/apr25/feedback_apr25.asc
- ANTAB and log files are available at
- Station feedback:
- ALMA and GBT were out and essentially did not observe this track
- Although ALMA observed the first scan (No0072 on 1741-038; no fringes) they then stopped on a technical fault
- GBT notes that they "did not observe c251a and mj008". Their Mk6 recordings expectedly produced no fringes.
- FD and PT receivers were warm, KP mostly(?) stowed due to weather
- DiFX v2d has two addPhaseCentre=... statements which form the required additional phase centers on Sgr A* and IRS 7 away from the P-Half telescope pointing position.
- Scans that got scheduled on the targets directly (not P-Half) had the source names REALSGRA and REALIRS7.
- Source names for the additional phase centers around P-Half are SGRA_P and IRS7_7.
Status
| what | date |
|---|---|
| Prepared DiFX setup for production correlation | 18.02.2026 |
| Full-track correlation v0 finished. Fringes to more stations. Revised VEX. | 20.02.2026 |
| Production correlation v1 started | 20.02.2026 |
Fringes
| Station | Code | Fringes | Plots | Comments |
|---|---|---|---|---|
| ALMA | no | only one "valid" scan, but it has no fringes | ||
| GBT | no | did not observe, has Mk6 recordings, but (as expected) they do not produce fringes | ||
| APEX | yes | No0105 | APEX-VLBA_FD fringes | |
| VLBA | partly | No0072 | weak fringes only; BR FD OV KP LA, and in one scan PT, none with NL | |
| No0105 | ||||
| No0175 | ||||
| No0201 | ||||
Notes
Stations that actually joined the test were: VLBA_BR, FD, PT, KP, LA, OV, NL, APEX. Out of these, NL produced no fringes. Others produced weak fringes and in just some scans.
Overall the intra-VLBA fringe SNRs are surprisingly low. In some cases the SNR over the course of a scan has strong dips as if from wind of other telescope movement. In addition, unlike in c251a c251b, the VLBA stations are not in time and start a few seconds late on every VEX scan.
The one and only potentially "valid" scan from ALMA produced no fringes. Hence ALMA was removed from the production correlation.
The GBT notes say they skipped this track. There are nevertheless GBT Mark6 recordings for the entire track, for some reason, but they did not produce fringes. Hence GBT was removed from the production correlation.
For the in beam phase referencing, the DiFX v2d definition of phase centers around the fake midpoint source P-HALF is:
SOURCE P-HALF {
# VEX SGRA ra = 17h45m40.0317460s; dec = -29d00'28.272280"; ref_coord_frame = J2000;
# VEX IRS7 ra = 17h45m40.0340570s; dec = -29d00'22.821530"; ref_coord_frame = J2000;
# Note: despite the ':' syntax below, the v2d units are RA hms and Dec dms
addPhaseCentre = name@IRS7_P/RA@17:45:40.0317460/Dec@-29:00:28.272280
addPhaseCentre = name@SGRA_P/RA@17:45:40.0340570/Dec@-29:00:22.821530
}
