Filling Out the Observation Area Classes
The Observation_Area contains a series of classes used to describe the overall parameters of observational data (target, observing instrument, UTC, etc.). It is required in observational products, and may also be used in collection and bundle products, if desired.
For additional explanation, see the PDS4 Standards Reference, or contact your PDS node consultant.
Following are the attributes and subclasses you'll find in the Observation_Area, in label order.
Note that in the PDS4 master schema, all classes have capitalized names; attributes never do.
Free-format text for any additional comments or description you might care to include.
This class most often contains just the start_time and stop_time attributes, but may also contain surface-based time measurements, like local solar times.
This should be the UTC start date/time of the observation, in any of several standard date formats (day-of-year, YMD, etc.) Maximum precision is four decimal places in the "seconds" field. The UTC indicator ('Z') on the end is optional, but note that start_time will always be interpreted as UTC, regardless of whether the 'Z' is present.
The <start_time> attribute is required. On those rare occasions when it is not an applicable concept, use the nilReason attribute with a value of either "inapplicable" or "unknown", as appropriate, with no value for <start_time> itself. It looks like this:
(These two forms are equivalent. The first form uses the XML shorthand for an element with no value content.)
This should be the UTC stop date/time of the observation. It has the same format constraints and caveats as <start_time>.
As with <start_time>, use a nilReason of "inapplicable" or "unknown" if there is no stop time available for some reason.
Other Optional Attributes
These attributes are optional (but must appear in this order, after <stop_time>) if present:
See the PDS4 data dictionary if they seem appropriate to the data set you're preparing, to make sure the definition matches your use. If it doesn't, check with PDS consultant to see if there is a discipline dictionary attribute that is suitable and can be included in the Discipline_Area; otherwise, create suitable keywords in your local dictionary to reference in the Mission_Area.