[ldd-ctli] It is not possible to use the CTLI namespace to describe multi-mode instruments

[acraugh]

Issue Type Multi-mode instruments are not uncommon; I'm assuming it is a bug that they are not supported. If the intention was not to support multi-mode instruments, then this is an enhancement, not a bug.

Describe the issue identified (if applicable) I attempted to use the CTLI dictionary to create a context object to describe the IMACS instrument mounted on the Magellan Baade telescope at Las Campanas Observatory. A summary of instrument specs is here:

http://www.lco.cl/wp-content/uploads/2021/03/IMACShandout2021.pdf

This instrument acts as both an imager and a spectrograph (among other things). There is no value exactly corresponding to "spectrograph", and it is in fact a wide-field imager, which is an important characteristic to note. When I encountered the in the object, I went looking for documentation on how to use the CTLI dictionary, but found none (I checked the Standards, the DPH, and the CTLI repo). When I attempted to guess my way through I was informed by validation that all these variations are not schematically valid because of their structure (the attribute values themselves are valid):

Method 1:

<Type_List_Area>
  <ctli:Type_List>
    <ctli:type>Imager</ctli:type>
    <ctli:subtype>wide-field</ctli:subtype>
  </ctli:Type_List>
  <ctli:Type_List>
    <ctli:type>Spectrometer</ctli:type>
    <ctli:subtype>spectrograph</ctli:subtype>   
    <ctli:subtype>multi-object</ctli:subtype>
  </ctli:Type_List>
</Type_List_Area>

Method 2:

<Type_List_Area>
  <ctli:Type_List>
    <ctli:type>Imager</ctli:type>
    <ctli:subtype>wide-field</ctli:subtype>
    <ctli:type>Spectrometer</ctli:type>
    <ctli:subtype>spectrograph</ctli:subtype>
    <ctli:subtype>multi-object</ctli:subtype>
  </ctli:Type_List>
</Type_List_Area>

Method 3:

<Type_List_Area>
    <ctli:type>Imager</ctli:type>
    <ctli:subtype>wide-field</ctli:subtype>
    <ctli:type>Spectrometer</ctli:type>
    <ctli:subtype>spectrograph</ctli:subtype>
    <ctli:subtype>multi-object</ctli:subtype>
</Type_List_Area>

Method 4:

<Type_List_Area>
  <ctli:Type_List>
    <ctli:type>Imager</ctli:type>
    <ctli:subtype>wide-field</ctli:subtype>
  </ctli:Type_List>
</Type_List_Area>
<Type_List_Area>
  <ctli:Type_List>
    <ctli:type>Spectrometer</ctli:type>
    <ctli:subtype>spectrograph</ctli:subtype>   
    <ctli:subtype>multi-object</ctli:subtype>
  </ctli:Type_List>
</Type_List_Area>

Describe the solution you'd like I need to be able to describe both types and subtypes of each of the modes of multi-mode instruments, and have the subtypes properly associated with their respective major types.

Describe alternatives you've considered See above. Context objects are required and instrument type attributes are potential search criteria. There is no alternative to the context requirement. Not supporting search for multi-mode instruments is not an acceptable alternative.

LDD Dictionary Version 1.16.0.0 and all preceding

PDS4 IM Version ASAP. This will impact the ability to ingest essential ground-characterization data included in the DART mission.

Need-by Date ASAP, in terms of build cycles. Data from this instrument are expected in early 2022, and would likely be registered in the March-June quarter.

Additional context This capability will also be needed for migration of data from multi-mode instruments on Rosetta, Deep Impact, etc. That timeline is more flexible than that of the DART mission.

[lylehuber]

Yes, we thought that Method 2 was what we were allowing but it turned out not to be. Method 1 is going to be the option going forward. Posting new Ingest file shortly.

[acraugh]

That'll work. Thanks @lylehuber!