Filling Out the Observation Area Classes

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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:

<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.)



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.



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>.

There is a useful list of standard values for the various attributes in this class on the Questions page

Note: While this class is currently optional, SBN will require that this class be provided for just about all observational data products.



The type attribute is a broad categorization of the discipline of the observation. It has values like Astrometry or Image. The value for this attribute must be one of the recognized standard values listed in the PDS4 Information Model (also found in the master Schematron file used for validation). Values current as of this writing are listed for handy reference on the Questions page.



This attribute describes the immediate goal for recording the observation. The value must be one of the five defined standard values:

  1. Calibration
  2. Checkout
  3. Engineering
  4. Navigation
  5. Science



This attribute classifies the observation by broad wavelength range or the equivalent for non-photon data. The value must be one of the standard values defined for this attribute. The values as of this writing are summarized on the Questions page.



This attribute can be used for additional free-format text decription.



This attribute must have one of the following four defined standard values:

  1. Calibrated
  2. Derived
  3. Raw
  4. Reduced



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

Note: For SBN data that do not have an associated mission or observing campaign, use the Null Investigation and its associated reference for this class.



This is the name of the mission or funded observing campaign. It should be the same as the <title> in the corresponding investigation context object, which must exist.



This must have one of these four values:

  • Mission - Use this for any funded mission.
  • Observing_Campaign - Use this for funded and/or formally coordinated observing campaigns (like the International Halley Watch)
  • Individual_Investigation - Use this for data resulting from specifically funded research with an archiving obligation, like data sets resulting from Data Analysis Program funding not associated with the original mission team.
  • Other_Investigation - Use this when you're also using the Null Investigation reference.

The value here must be identical to the <type> value in the context object cited in the <Internal_Reference>.



This must be a reference to the context object associated with the investigation named above.



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.



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



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.



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.