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.

<comment>

OPTIONAL

Free-format text for any additional comments or description you might care to include.

---

<Time_Coordinates>

REQUIRED

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.

<start_time>

REQUIRED

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:

<start_time nilReason="inapplicable"/>

or this:

<start_time nilReason="inapplicable"></start_time>

(These two forms are equivalent. The first form uses the XML shorthand for an element with no value content.)

<stop_time>

REQUIRED

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:

<local_mean_solar_time>

<local_true_solar_time>

<solar_longitude>

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.

---

<Primary_Result_Summary>

OPTIONAL

This class contains attributes for high-level searching across large sections of the PDS archive. For more detailed descriptive attributes, look for the <Primary_Result_Details> in the <Discipline_Area>.

Note: While this class is currently optional in the general case, SBN will require that this class be provided for just about all products.

<Investigation_Area>

REQUIRED

This class is used primarily to identify the mission or organized observing campaign that collected or produced the data/documentation comprising this product.

For SBN data that do not have an associated mission or observing campaign, use the Null Investigation.

<Observing_System>

REQUIRED

This class documents the significant pieces of the observing equipment. It is used, for example, to associate instruments, spacecraft, or telescopes with the product.

Note: While this class is currently allowed to be repeated, that is almost never logically valid. If you think you need multiple <Observing_System> classes, contact your PDS consultant first.

<Target_Identification>

REQUIRED

This class associates a target name with the product. It can be repeated as many times as needed.

<Mission_Area>

OPTIONAL

This class is a wrapper to hold classes and attributes from one or more mission dictionaries, or equivalent non-mission local dictionaries for data not associated with a mission.

The <Mission_Area> may not be repeated. Any number of different local dictionaries can be referenced inside this class.

<Discipline_Area>

OPTIONAL

This class is a wrapper to hold classes and attributes from one or more discipline dictionaries.

The <Discpline_Area> may not be repeated. Any number of difference discipline dictionaries can be referenced inside this class.