comments on SED DM V0.93

[Alberto Micol]

Dear Jonathan and Doug,

I finally went through this remarkable work (SED DM v0.93)
and have a couple of comments/questions on the following topics:

1. Absolute vs Relative flux
2. Slit shape and position
3a. Astrometric information
3b. Astrometric accuracy
3c. Constant Coverage per "spectrum"?
4. Bandpass
5. UCDs

1. Absolute vs Relative flux

Is there a way to specify whether the Flux is Absolutely calibrated
or whether only the shape is correctly known?

I probably remember someone already asking this question, but cannot 
find it.
Sorry if this was already asked.


2. Slit shape and position

Do I get it right that in this version the only available aperture is 
circular?
I could not find the place to put the orientation of the slit. Have I 
missed it?


3a. Astrometric information

Which ones are the "observed" coordinates (RA_NOM,DEC_NOM) or 
(RA_TARG,DEC_TARG)?
According to the full example of a FITS header it seems to be the 
latter,
but according to the text in the document it is probably the other one.
Also, (8.1 FITS Serialization):
 > The Position.Type field is not explicitly serialized; the names
 > of the two columns used for Position are used to infer the type
The document should list all the allowed names.


3b. Astrometric accuracy

Have I missed the place to store the errors on the spatial position?
The entire "Coverage Fields" section is not listing any error.


3c. Constant Coverage per "spectrum"

The first sentence of (5.1) states:
 > The coverage fields will have constant value for a given "spectrum"
It should probably be "segment" instead.


4. Bandpass

For photometric points, the bandpass name is specified in 5.1 Coverage 
Fields
as Coverage.Location.SpectralCoord.Value (instr.bandpass) to be 
consistent
with RSM. The fact is that there is no defined list of such bandpasses,
hence it is not possible for the analysis software to understand what
the band pass really is.


5. UCDs

Non-compliant UCDs
There are some UCDs which, according to the UCD1+ standard, are not 
allowed
to be Primary words:

(4.2 Spectral Coordinate) instr.pixel;...
(4.3 Flux Object)         arith.ratio;...

Misleading UCDs
(4.7 Accuracy Fields) The Sky.Resolution UCD is "instr.ang-res" which 
makes one
think it is not taking into account the seeing. In case the seeing is 
to be
considered, the UCD should probably be "instr.obsty.site.seeing".

Wrong UCD
(5.1 Coverage Fields) Frame.Time.SIDim UCD is "time;arith.zp"
I don't know what should it be instead, maybe a arith.ratio?


THANKS!

Alberto
--
Alberto Micol
ST-ECF HST Archive Scientist