Opened 14 years ago
Closed 14 years ago
#103 closed defect (fixed)
Q & U sign negated at 7mm
| Reported by: | JamieStevens | Owned by: | MarkWieringa |
|---|---|---|---|
| Priority: | major | Milestone: | |
| Component: | MIRIAD - CABB branch | Version: | |
| Keywords: | polarisation 7mm | Cc: | |
| Estimated Number of Hours: | 0 | Add Hours to Ticket: | 6 |
| Billable?: | yes | Total Hours: | 0 |
Description
It has been found by a team (Feain, Broderick, Mahony) investigating polarisation at 7mm that the position angle of the E vectors change by 90 degrees from 12mm data to 7mm data. This has been reported on a few sources. By forcibly multiplying the Q and U components by -1 they achieve much more satisfactory (and believable) results.
Feain also points to a similar problem found by Johnston and Koribalski at 12mm a few years ago, that required a change to atlod to fix.
Change History (3)
comment:1 Changed 14 years ago by
| Add Hours to Ticket: | 0 → 4 |
|---|---|
| Status: | new → assigned |
comment:2 Changed 14 years ago by
| Add Hours to Ticket: | 4 → 6 |
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User feedback indicated the fix was not correct. I've installed a new fix, this time by changing the feed position angle (chi) by 90 degrees. It has the same effect on Q and U but avoids strange gain effects around transit which mess up the pol images. Awaiting new feedback..
comment:3 Changed 14 years ago by
| Resolution: | → fixed |
|---|---|
| Status: | assigned → closed |
New feedback was positive. Declare this fixed for now.
A fix has now been made to atlod which reverses the sign of the XY and YX correlations for 7mm data. This results in Q and U (and V) having the opposite sign. The polarization angle changes by 90 degrees. Awaiting user testing before this is closed.