Platform Capabilities Document

This section provides documentation on the content of a Platform Capabilities document. The following examples are extracted from the SPOT5 satellite instance. This document type is common to all three sentinels.

Overall structure of the document type

The overall structure of a Platform Capabilities document is show below:

<sml:SensorML
   xmlns:sml="http://www.opengis.net/sensorML/1.0.1" 
   xmlns:swe="http://www.opengis.net/swe/1.0.1"
   xmlns:gml="http://www.opengis.net/gml"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
   xmlns:xlink="http://www.w3.org/1999/xlink"
   version="1.0.1">
   <!-- -->
   <sml:member xlink:role="urn:ogc:def:dictionary:CEOS:documentRoles:v01#platform_capabilities">
      <sml:System gml:id="LOCAL_PLATFORM_ID">
         <gml:description ... />
         <sml:identification ... />
         <sml:classification ... />
         <sml:validTime ... />
         <sml:characteristics xlink:role="urn:ogc:def:role:CEOS:eop:OrbitCharacteristics" ... />
         <sml:capabilities xlink:role="urn:ogc:def:role:CEOS:eop:CommunicationCapabilities" ... />
         <sml:capabilities xlink:role="urn:ogc:def:role:CEOS:eop:DataCapabilities" ... />
         <sml:contact xlink:role="urn:ogc:def:role:OGC:contact:operator" ... />
         <sml:contact xlink:role="urn:ogc:def:role:OGC:contact:distributor" ... />
         <sml:documentation xlink:role="urn:ogc:def:role:OGC:document:datasheet" ... />
         <sml:components ... />
      </sml:System>
   </sml:member>
</sml:SensorML>

The "description" is used, as in the case of an Instrument, to give an overall, human readable, description of the platform.

All other section of the document are detailed further in the following paragraphs.

Identification Section

The identification section of an Platform is similar to that of an Instrument:

<sml:identification>
   <sml:IdentifierList>
      <sml:identifier name="Platform UID">
         <sml:Term definition="urn:ogc:def:property:CEOS:eop:PlatformID">
            <sml:value>urn:ogc:id:CEOS:platform:SPOT5:v01</sml:value>
         </sml:Term>
      </sml:identifier>
      <sml:identifier name="Short Name">
         <sml:Term definition="urn:ogc:def:property:OGC:shortName">
            <sml:value>SPOT5</sml:value>
         </sml:Term>
      </sml:identifier>
      <sml:identifier name="Long Name">
         <sml:Term definition="urn:ogc:def:property:OGC:longName">
            <sml:value>Système Pour l'Observation de la Terre Nº5</sml:value>
         </sml:Term>
      </sml:identifier>
   </sml:IdentifierList>
</sml:identification>

• Platform UID: Used to uniquely identify the Platform itself

• Short Name and Long Name: Used as in an Instrument Capabilities document, i.e. to provide human readable names for display

See the Identification Section of the Instrument Capabilities page for more details.

Classification Section

The classification section has the same form as the one in an Instrument Capabilities document, but the classifiers are different:

<sml:classification>
   <sml:ClassifierList>
      <sml:classifier name="Platform Type">
         <sml:Term definition="urn:ogc:def:property:OGC:platformType">
            <sml:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:eop:PlatformTypes:v01"/>
            <sml:value>Satellite</sml:value>
         </sml:Term>
      </sml:classifier>
      <sml:classifier name="Orbit Type">
         <sml:Term definition="urn:ogc:def:property:OGC:platformType">
            <sml:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:eop:OrbitTypes:v01"/>
            <sml:value>Sun-Synchronous</sml:value>
         </sml:Term>
      </sml:classifier>
      <sml:classifier name="Orbit Type">
         <sml:Term definition="urn:ogc:def:property:OGC:platformType">
            <sml:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:eop:OrbitTypes:v01"/>
            <sml:value>LEO</sml:value>
         </sml:Term>
      </sml:classifier>
   </sml:ClassifierList>
</sml:classification>

• Platform Type: Classifies the Platform according to the dictionary defined by the codespace. (You can view the GML dictionary document defining this codespace (through a stylesheet): urn:ogc:def:dictionary:CEOS:eop:PlatformTypes:v01).

• Orbit Type: One or more orbit types can be attached to the plaform, according to the dictionary of orbit types defined by the codespace. (You can view the GML dictionary document defining this codespace (through a stylesheet): urn:ogc:def:dictionary:CEOS:eop:OrbitTypes:v01).

For more information about the structure of each classifier, please refer to the documentation of the Classification Section of an Instrument Capabilities document.

ValidTime Section

This is used to indicate the temporal validity of the document.

<sml:validTime>
    <gml:TimePeriod>
        <gml:beginPosition>2002-05-04T00:00:00Z</gml:beginPosition>
        <gml:endPosition indeterminatePosition="now"/>
    </gml:TimePeriod>    
</sml:validTime>

This section is used like in an Instrument Capabilities document, as it gives the temporal validity of the description, and can be used in cases where the plaform capabilities are altered by an incident taking place while in flight. See the ValidTime Section of an Instrument Capabilities document for more info.

Physical Characteristics Section

This section can collect physical characteristics of the Platform (i.e. mass, max power, etc...) as shown in the corresponding section of an Instrument Capabilities document.

Orbit Characteristics Section

This section includes detailed characteristics of the nominal orbit, as shown on the following XML snippet:

<sml:characteristics xlink:role="urn:ogc:def:role:CEOS:eop:OrbitCharacteristics">
   <swe:DataRecord>
      <gml:name>Orbit Characteristics</gml:name>
      <swe:field name="Epoch Year">
         <swe:Count definition="urn:ogc:def:property:CEOS:eop:EpochYear">
            <gml:description>Year at Epoch</gml:description>
            <swe:value>2007</swe:value>
         </swe:Count>
      </swe:field>
      <swe:field name="Epoch Day">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:EpochDay">
            <gml:description>Day of Year at Epoch</gml:description>
            <swe:uom code="d"/>
            <swe:value>49.19794444</swe:value>
         </swe:Quantity>
      </swe:field>               
      <swe:field name="Inclination">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitInclination">
            <gml:description>Inclination of the Orbit</gml:description>
            <swe:uom code="deg"/>
            <swe:value>98.6997</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Right Ascension">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitRigthAscension">
            <gml:description>Right Ascension of Ascending Node</gml:description>
            <swe:uom code="deg"/>
            <swe:value>124.3641</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Eccentricity">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitEccentricity">
            <gml:description>Orbit (Ellipse) Eccentricity</gml:description>
            <swe:value>0.0000910</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Argument Of Perigee">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitArgumentOfPerigee">
            <gml:description>Argument of Perigee</gml:description>
            <swe:uom code="deg"/>
            <swe:value>73.4124</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Mean Anomaly">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitMeanAnomaly">
            <gml:description>Mean Anomaly of the Orbit</gml:description>
            <swe:uom code="deg"/>
            <swe:value>286.7156</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Mean Motion">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitMeanMotion">
            <gml:description>Mean Motion of the Spacecraft in revs/day</gml:description>
            <swe:uom code="circ/d"/>
            <swe:value>14.20037920</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Decay Rate">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitDecayRate">
            <gml:description>First Derivative of Mean Motion in revs/day^2</gml:description>
            <swe:uom code="circ/d2"/>
            <swe:value>-0.00000018</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Orbit Height">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:AverageOrbitHeight">
            <swe:uom code="km"/>
            <swe:value>832</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Orbit Cycle">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:OrbitCycle">
            <swe:uom code="d"/>
            <swe:value>26</swe:value>
         </swe:Quantity>
      </swe:field>
   </swe:DataRecord>
</sml:characteristics>

Most of these orbital parameters directly correspond to fields in the NORAD TLE (Two Line Elements) record format. All of them are defined using the SWE Common syntax that allows to specify the name, definition,*uom* (i.e. unit of measure) and value.

Communication Capabilities Section(s)

One or more "Communication Capabilities" groups (as shown below) can be included to specify communication capabilities of the platform in one or more frequency bands:

<sml:capabilities>
   <swe:DataRecord>
      <gml:name>Communication Capabilities</gml:name>
      <swe:field name="Frequency Band">
         <swe:Category definition="urn:ogc:def:property:CEOS:eop:FrequencyBand">
            <gml:description>Frequency Band used for the downlink radio transmission</gml:description>
            <swe:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:eop:SpectralBands:v01"/>
            <swe:value>X</swe:value>
         </swe:Category>
      </swe:field>
      <swe:field name="Downlink Capacity">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:DownlinkCapacity">
            <gml:description>Maximum capacity of the downlink radio transmission</gml:description>
            <swe:uom code="Mibit"/>
            <swe:value>100</swe:value>
         </swe:Quantity>
      </swe:field>               
      <swe:field name="Downlink Modulation">
         <swe:Category definition="urn:ogc:def:property:CEOS:eop:DownlinkModulation">
            <gml:description>Modulation used for the downlink radio transmission</gml:description>
            <swe:value>QPSK</swe:value>
         </swe:Category>
      </swe:field>
   </swe:DataRecord>
</sml:capabilities>

Data Capabilities Section

The "Data Capabilities" group is used to provide information relative to on-board data management capabilities:

<sml:capabilities xlink:role="urn:ogc:def:role:CEOS:eop:DataCapabilities">
   <swe:DataRecord>
      <gml:name>Data Capabilities</gml:name>
      <swe:field name="Onboard Storage Capacity">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:StorageCapacity">
            <swe:uom code="Gibit"/>
            <swe:value>41</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Onboard Storage Method">
         <swe:Category definition="urn:ogc:def:property:CEOS:eop:StorageMethod">
            <swe:value>Solid-State</swe:value>
         </swe:Category>
      </swe:field>
      <swe:field name="Compression Method">
         <swe:Category definition="urn:ogc:def:property:CEOS:eop:DataCompressionMethod">
            <swe:value>DCT</swe:value>
         </swe:Category>
      </swe:field>
   </swe:DataRecord>
</sml:capabilities>

This snippet shows the three mandatory characteristics that should be provided in all platform descriptions following the GMES Product Harmonization profile.

Contact Section(s)

As for an Instrument, one or more contact with different roles can be defined in this section:

<sml:contact xlink:role="urn:ogc:def:role:OGC:contact:operator">
    <sml:ResponsibleParty>
        <sml:individualName>Didier Giacobbo</sml:individualName>
        <sml:organizationName>Spot-Image</sml:organizationName>               
        <sml:contactInfo>
            <sml:phone>                
                <sml:voice>+33 5 62 19 42 52</sml:voice>
            </sml:phone>
            <sml:address>
                <sml:deliveryPoint>5, rue des satellites, BP 4359</sml:deliveryPoint>
                <sml:city>TOULOUSE, Cedex 4</sml:city>
                <sml:postalCode>31030</sml:postalCode>
                <sml:country>FRANCE</sml:country>                
            </sml:address>
        </sml:contactInfo>
    </sml:ResponsibleParty>
</sml:contact>

Platform Components

As discussed in the introduction, a Platform carries several Instruments, that are listed in this section.

<sml:components>
   <sml:ComponentList>
      <sml:component name="HRG1 Instrument" xlink:href="Instrument_SPOT5-HRG1_v01_draft03.xml#SPOT5_HRG"/>
      <sml:component name="HRG2 Instrument" xlink:href="Instrument_SPOT5-HRG2_v01_draft03.xml#SPOT5_HRG"/>
      <sml:component name="HRS Instrument" xlink:href="Instrument_SPOT5-HRS_v01_draft03.xml#SPOT5_HRS"/>
   </sml:ComponentList>
</sml:components>

It is recommended to not include the Instrument descriptions inline in the Platform Capabilities document but to reference an external document via an xlink, as shown on this example. This allows for easy reuse of the same documents for other purposes.

-- AlexandreRobin - 01 Feb 2008