EDIT: Still looking into this, but here's the latest reply from Wolfram:
The Scientific Astronomer package you are referencing was a third
party package that the company never maintained. It looks as though it
has not been updated since version 5.
You will find similar functionality in the interpreters listed under
Related Interpreters at the following link:
I cannot say if the exact functionality from that package has been
implemented in more recent versions however, as we did not maintain
EDIT: It appears that Mathematica has or had a product
called Scientific Astronomer that did this. Snapshotting
pages 44-45 (pages 56-57 of the PDF version) of:
Presumably, Wolfram won't give away for free what they sell
in a separate software package.
The unusual thing here is that all the links I found to
purchase Scientific Astronomer are either broken or lead to
a generic "packages" pages. See also:
How do I determine astronomical transit times? which
mentions Scientific Astronomer is a "legacy" package.
You may also want to ping Wolfram. Searching for
'"scientific astronomer" site:wolfram.com' (as quoted)
yields several results, but no actual mention I could find
of how to obtain the package.
ORIGINAL ANSWER: Too long for a comment, but not an answer.
OK, I think I see your problem now. When I did
AstronomicalData["Io", "Properties"] (I'm using an older
version of Mathematica), I did see
Position as one of the
values. However, Mathematica yields
Io's position (and it works for Jupiter and the Sun, so
it's not because I'm not providing a date object).
Properties just returns a template that may
or may not work in a specific case.
In:= t2 // TableForm
> AbsoluteMagnitude Missing[NotAvailable]
AlternateNames Jupiter I
Apoapsis 4.235 10
Diameter 3.6432 10
Mass 8.9298 10
OrbitPeriod 1.528 10
SemimajorAxis -> 4.218 10
Eccentricity -> 0.0041
Inclination -> 0.036
PeriapsisArgument -> 84.129
AscendingNodeLongitude -> 43.977
PeriapsisLongitude -> Missing[NotAvailable]
Periapsis -> 4.201 10
OrbitRules Apoapsis -> 4.235 10
Periapsis 4.201 10
Radius 1.8216 10
RotationPeriod 1.528 10
SemimajorAxis 4.218 10
- It's possible this functionality is available in a
Mathematica add-on, but a lot of add-on functionality is
now part of Mathematica itself. However, you may want to
just in case I missed something.
If you just need a table of Io position data:
If you're OK with using something other than
Mathematica to compute positions:
There's also pyephem, skyfield, Astro::Nova and
doubtless many others, though the CSPICE libraries above
are the ones NASA uses.
Finally, I've converted some position data to
Mathematica format. I can provide more details, but,
unless you absolutely have to use Mathematica, I wouldn't
recommend this method.