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In fact what happens is that the IERS_Auto just serves up an unmodified IERS B file as if it were an IERS A file. This means all the A columns are missing (naturally enough), all the B columns are missing (which is awkward and unnecessary), and all the unmarked columns are taken straight from the IERS B table. The units of dX... and dY... are different in IERS B than IERS A (arcseconds versus milliarcseconds) but this is probably not a serious problem as long as people never take the .value without a .to() first. (The code in iers.py used to do this, so it's a realistic concern.) The IERS B table also has PM_X instead of PM_x as a column name.
The right answer is probably to construct a fake IERS A object from just the IERS B. Though really, the current interface doesn't provide you a way to get a plain IERS A table (that, is without some IERS B data substituted in). Perhaps a class providing a merge of whatever data is available? Perhaps that also provides auto-updating as needed? I notice that the IERS B data is never automatically updated even in IERS_Auto.
I think this particular issue is largely moot now that both IERS-A and IERS-B are bundled via astropy-iers-data (#14819). There are still lingering questions about merging in IERS-B data (e.g., #9227 and #13494), but they are probably better discussed in those issues.
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aarchiba commentedon Sep 6, 2019
In fact what happens is that the IERS_Auto just serves up an unmodified IERS B file as if it were an IERS A file. This means all the A columns are missing (naturally enough), all the B columns are missing (which is awkward and unnecessary), and all the unmarked columns are taken straight from the IERS B table. The units of dX... and dY... are different in IERS B than IERS A (arcseconds versus milliarcseconds) but this is probably not a serious problem as long as people never take the .value without a .to() first. (The code in iers.py used to do this, so it's a realistic concern.) The IERS B table also has PM_X instead of PM_x as a column name.
The right answer is probably to construct a fake IERS A object from just the IERS B. Though really, the current interface doesn't provide you a way to get a plain IERS A table (that, is without some IERS B data substituted in). Perhaps a class providing a merge of whatever data is available? Perhaps that also provides auto-updating as needed? I notice that the IERS B data is never automatically updated even in IERS_Auto.
pllim commentedon Sep 6, 2019
cc @taldcroft and @mhvk
Fixes astropy#9205
Fixes astropy#9205
ayshih commentedon Mar 12, 2024
I think this particular issue is largely moot now that both IERS-A and IERS-B are bundled via
astropy-iers-data(#14819). There are still lingering questions about merging in IERS-B data (e.g., #9227 and #13494), but they are probably better discussed in those issues.mhvk commentedon Mar 12, 2024
I agree that this is moot given
astropy-iers-data- let's close it.