Parallax Measure

[mcdittmar]

The MANGO-v1.0 work has a use case involving GAIA data, including the Parallax data.
In that model, the parallax is consolidated to a simple value + error representation.

My attempt to map this to the Measurement model using GenericMeasure shows that this representation is inadequate to properly convey the coordinate space. The intent is to provide the detailed model backing the simple attribute described in the MANGO model.

1. The associated coordinate system is a simple 1D space, with no domain specification (eg: SpaceSys with SpaceFrame & Spherical )
2. The Generic representation can only accommodate the Earth-based scenario with a base of 1AU.

Parallax Angle: "The angle from the radial axis in line of sight from the object toward the origin such that P(arcsec) = B(AU)/distance"
o so the value should be associated with the radial axis of a spherical coordinate space. The important part is that it is measured from the line-of-sight from the object to an origin point.
o the length of the base is an important piece of metadata, especially for the usage of determining distance in an epoch propagation thread.

Options:
Note that the requirements mostly fall to the Coordinates model, with the majority of change occurring there.
I've made a couple diagrams of options to seed the discussion.

1. add Parallax measure, with angular coordinate mapping to a new axis added to the Standard Spherical Coordinate Space.
   

2. add Parallax measure, with angular coordinate associated with a new SpaceSys providing details of the coordinate space. This representation would allow the Parallax to be provided in a coordinate space that differs from the Position. I'm pretty sure this could be adjusted to accommodate the case where parallax is given in polar coordinates at the object with speed and direction angle.