Generic targets are those that can only be described in terms of astronomical characteristics or general location in the sky. This category is used only for Targets of Opportunity and parallel exposures.
For parallel exposures, both pure-parallel and coordinated-parallel (see Chapter 6: Parallel Science Exposures on page 103), the pointing is determined by the primary observation, and the specification of a generic target for the parallel exposure denotes a region within which the parallel aperture is expected to point. If the parallel pointing does not matter and the intent is simply to sample whatever the parallel aperture happens to detect, it is not necessary to define a generic target; instead the special target
ANY should be used (see
5.8 Target Name [Target_Name] on page 94).
Note: Generic Target region coordinates are assumed to be in the J2000 reference frame.
A descriptive name must be provided for each target. If a name cannot be specified in advance, a provisional name should be supplied. When the actual observation is made, a more specific name will be added to the target designation. Either the provisional name or the updated name can then be used for archival searches (e.g.,
SN might be the provisional name, while
SN-1995D might be the updated name). A unique target name
must be assigned to each generic target.
The "Criteria" field is a way to specify generic celestial regions and target lists is described below, and should be used for Generic Targets. These instructions should be followed in order for pure parallels with generic targets to be schedulable.
Region Generic Targets: a celestial region is specified in one of three coordinate systems
Target Lists: Lists of fixed or generic targets are specified
The Selection Criteria field should use the syntax specified below whenever the selection criteria can be fully specified by a celestial region in one of the supported coordinate systems, or by a list of fixed or generic targets.
Galactic: Galactic longitude (
LII) and Galactic latitude (
BII)
Ecliptic: ecliptic longitude (
LAMBDA) and ecliptic latitude (
BETA)
“Rectangular” regions: i.e. bounded by latitude and longitude limits in the appropriate coordinate system
Circular regions: specified as within some angular limit of a point specified in any of the three supported coordinate systems
Polar caps or equatorial bands: specified in any supported coordinate system
The following table provides examples of each of these types of region specifications. Note that the same rules for specifying RA and Dec apply as for fixed targets (
Section 3.4.2 on page 38) and that the angle specifications must include ' and " (or M and S).
Note that for rectangular and circular regions, the syntax is identical to that of fixed target regions except that the indicator
REGION is omitted, and galactic and ecliptic coordinates are allowed.
In some cases it may be desirable to specify as a Generic Target any of a list of Fixed Target positions or Generic Target regions. In this case the fixed targets should be provided as usual on the Fixed Target List, and the generic target regions should be specified as above on the Generic Target List. Then a new generic target can be defined with Selection Criteria specified by:
This will be taken to indicate that any of the targets in <target-number-list> are suitable as targets. Note that target numbers are required to be unique across all targets in a proposal, whether on the Fixed, Generic, or Solar System Target Lists.
This type of target is particularly useful when a known list of objects of interest is available, and it is desired to observe one of these objects with an imaging SI when a primary exposure with a spectrograph is positioned appropriately nearby.
