Table of contents
- 1. MJ008 Correlation Report
- 1.1. General information
- 1.2. Status
- 1.3. Fringes
- 1.4. Notes
- 1.5. Post-Correlation checks
- 1.5.1. UV Coverage
- 1.5.2. Residuals
- 1.5.3. FITS completeness (pclist)
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. These normal sources have visbility in dataset mj008-main-PHALF.fits
- Source names for the additional phase centers around P-Half are SGRA_P (dataset: mj008-SGRA_P.fits) and IRS7_P (dtaset: mj008-IRS7_P.fits).
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 and completed | 20.02.2026 |
| Production correlation v1 released to PI | 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 | |
| No0175 | intra-VLBA | |||
| No0201 | APEX-VLBA, fringe amplitude dropouts on VLBA-VLBA and more clearly APEX-LA baseline | |||
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
UV Coverage
Plot of UV coverage with fringe detections shown in color and non-detections shown as blank dots
.
Residuals
Residuals of the detections on baselines to APEX
FITS completeness (pclist)
AA AX NL FD PT LA OV KP BR GB mj008_1000 No0072 1741-038 86ghz o o o o o o o o mj008_1001 No0075 P-HALF 86ghz o o o o o o o mj008_1002 No0078 P-HALF 86ghz o o o o o o o mj008_1003 No0084 P-HALF 86ghz o o o o o o o mj008_1004 No0088 P-HALF 86ghz o o o o o o o mj008_1005 No0094 P-HALF 86ghz o o o o o o o mj008_1006 No0098 P-HALF 86ghz o o o o o o o mj008_1007 No0105 1921-293 86ghz o o o o o o o mj008_1008 No0106 P-HALF 86ghz o o o o o o o mj008_1009 No0110 P-HALF 86ghz o o o o o o o mj008_1010 No0114 P-HALF 86ghz o o o o o o o mj008_1011 No0118 P-HALF 86ghz o o o o o o o mj008_1012 No0125 REALSGRA 86ghz o o o o o o o o mj008_1013 No0128 REALIRS7 86ghz o o o o o o o o mj008_1014 No0132 P-HALF 86ghz o o o o o o o o mj008_1015 No0135 P-HALF 86ghz o o o o o o o o mj008_1016 No0142 1921-293 86ghz o o o o o o o o mj008_1017 No0143 P-HALF 86ghz o o o o o o o o mj008_1018 No0145 P-HALF 86ghz o o o o o o o o mj008_1019 No0149 P-HALF 86ghz o o o o o o o o mj008_1020 No0151 P-HALF 86ghz o o o o o o o o mj008_1021 No0158 1921-293 86ghz o o o o o o o o mj008_1022 No0161 P-HALF 86ghz o o o o o o o o mj008_1023 No0163 P-HALF 86ghz o o o o o o o o mj008_1024 No0167 P-HALF 86ghz o o o o o o o o mj008_1025 No0169 P-HALF 86ghz o o o o o o o o mj008_1026 No0175 1921-293 86ghz o o o o o o o o mj008_1027 No0178 P-HALF 86ghz o o o o o o o o mj008_1028 No0180 P-HALF 86ghz o o o o o o o o mj008_1029 No0183 P-HALF 86ghz o o o o o o o o mj008_1030 No0187 1921-293 86ghz o o o o o o o o mj008_1031 No0190 P-HALF 86ghz o o o o o o o o mj008_1032 No0191 P-HALF 86ghz o o o o o o o o mj008_1033 No0194 P-HALF 86ghz o o o o o o o o mj008_1034 No0195 P-HALF 86ghz o o o o o o o mj008_1035 No0196 P-HALF 86ghz o o o o o o o mj008_1036 No0197 P-HALF 86ghz o o o o o o o mj008_1037 No0198 P-HALF 86ghz o o o o o o o mj008_1038 No0201 3C454.3 86ghz o o o o o o o o
Comments