Coordinate equinox: B{year} or J{year} with at least one decimal; do not use in conjunction with ICRS Coordinate reference frame: optional equinox with either a standard reference system (ICRS, FK5, FK4) and optional standard pole (equatorial, ecliptic, galactic, etc.), or pole (positive Z-axis) and positive X-axis direction Coordinate equinox: B{year} or J{year} with at least one decimal; do not use in conjunction with ICRS Most common: standard reference system with optional pole direction (default: equatorial) Define coordinate reference frame from scratch; pole and X-axis need to be defined in a known coordinate system Origin of the coordinate reference frame: either a "known place" such as geocenter or barycenter, or a position defined in a known coordinate system Coordinate reference frame: optional equinox with either a standard reference system (ICRS, FK5, FK4) and optional standard pole (equatorial, ecliptic, galactic, etc.), or pole (positive Z-axis) and positive X-axis direction Origin of the coordinate reference frame: either a "known place" such as geocenter or barycenter, or a position defined in a known coordinate system The time reference frame consists of a time scale, a time format, and a reference time, if needed Origin of the coordinate reference frame: either a "known place" such as geocenter or barycenter, or a position defined in a known coordinate system Some time transformations (e.g., change of RefPos) depend on an assumed directonal position of the source If solar system positions are implied anywhere, the planetary ephemeris to be used needs to be provided - usually JPL-DE405 with ICRS and JPL-DE200 with FK5 The Doppler definition used: optical, radio, or pseudo-relativistic (i.e., how is a redshift converted to a velocity); the most common is optical, except when the reference is LSR (usually radio) The reference frame for the Doppler velocities; note presence of LSR Contains the Doppler definitions, including whether the values are velocity or redshift (value_type) The Doppler definition used: optical, radio, or pseudo-relativistic (i.e., how is a redshift converted to a velocity); the most common is optical, except when the reference is LSR (usually radio) The reference frame for the Doppler velocities; note presence of LSR Provides the coordinate definitions: number of axes, SPHERICAL or CARTESIAN, presence of velocities, and the Doppler definitions (if needed) The coordinate system definition: spatial coordinate frame and reference position; time frame and reference position; the coordinate flavor; and the planetary ephemeris; an ID is required, since this is how coordinate elements are associated with their coordinate systems The time coordinate reference frame The spatial coordinate reference frame The reference frame for the spectral coordinate; note presence of LSR Contains the Doppler definitions, including whether the values are velocity or redshift (value_type) Provides the coordinate definitions: number of axes, SPHERICAL or CARTESIAN, presence of velocities, and the Doppler definitions (if needed) If solar system positions are implied anywhere, the planetary ephemeris to be used needs to be provided - usually JPL-DE405 with ICRS and JPL-DE200 with FK5 The time interval needs to contain a start time or a stop time or both; it needs to refer to a coordinate system; boundaries may or may not be inclusive astronTime may be expressed in ISO8601 or as a double relative to a reference time; or it may be provided in an entity refered to by the Reference element astronTime may be expressed in ISO8601 or as a double relative to a reference time; or it may be provided in an entity refered to by the Reference element The spatial coordinate interval needs to contain a minimum or maximum scalar or vector value, or both; it needs to refer to a coordinate system; boundaries may or may not be inclusive A scalar coordinate value consists of a double or a reference to an entity (that should contain a double) A scalar coordinate value consists of a double or a reference to an entity (that should contain a double) A special kind of area is a circle or sphere (in two or three dimensions), defined by a center position and a radius; the radius requires a unit A coordinate area consists of a time interval, a spatial area, a velocity interval, and a redshift interval (as needed); the spatial area may be specified by an interval, a circle or sphere, a region element, or a region file Toplevel: STCmetadata contains a choice of: ResourceProfile, SearchLocation, CatalogEntryLocation, or ObservationLocation plus ObservatoryLocation elements Describes the spatial and temporal coverage of a resource The coordinate system definition: spatial coordinate frame and reference position; time frame and reference position; the coordinate flavor; and the planetary ephemeris; an ID is required, since this is how coordinate elements are associated with their coordinate systems The coverage area of the resource; the fill factor does not need to be 1.0 CoordSpec contains information on time and spatial resolution, errors, and pixelsizes (if fixed); typical best numbers are expected Defines the spatial and temporal coordinate space specified by a query The coordinate system definition: spatial coordinate frame and reference position; time frame and reference position; the coordinate flavor; and the planetary ephemeris; an ID is required, since this is how coordinate elements are associated with their coordinate systems Region of Interest CoordSpec contains information on desired time and spatial resolution, errors, and pixelsizes (if fixed); typical best numbers are expected Describes the spatial and temporal coverage of a catalog (fragment) The coordinate system definition: spatial coordinate frame and reference position; time frame and reference position; the coordinate flavor; and the planetary ephemeris; an ID is required, since this is how coordinate elements are associated with their coordinate systems The coordinate element consists either of a coordinate file or a sequence of time element, spatial coordinate element, velocity element, and redshift element; the spatial and velocity elements may be scalar or vector; it needs to refer to a coordinate system Optional specification of the area covered by the catalog data Describes the spatial and temporal volume covered by an observation Specifies the location of the observatory during the observation The coordinate system definition: spatial coordinate frame and reference position; time frame and reference position; the coordinate flavor; and the planetary ephemeris; an ID is required, since this is how coordinate elements are associated with their coordinate systems The coordinate element consists either of a coordinate file or a sequence of time element, spatial coordinate element, velocity element, and redshift element; the spatial and velocity elements may be scalar or vector; it needs to refer to a coordinate system Describes the spatial and temporal coverage of the observation The coordinate system definition: spatial coordinate frame and reference position; time frame and reference position; the coordinate flavor; and the planetary ephemeris; an ID is required, since this is how coordinate elements are associated with their coordinate systems The coordinate element consists either of a coordinate file or a sequence of time element, spatial coordinate element, velocity element, and redshift element; the spatial and velocity elements may be scalar or vector; it needs to refer to a coordinate system The field of view