CCSDS CDM¶

Note

The CDM types live in the IO.Astrodynamics.CCSDS.CDM namespace.

The CDM module supports constructing, reading, writing, and validating CCSDS Conjunction Data Messages in XML format.

Cdm Object Model¶

Cdm is the root object representing a complete Conjunction Data Message with header, relative metadata, and two object entries.

Static Methods¶

Method	Description
`Cdm.ReadFromFile(path)`	Parse a CDM XML file into a `Cdm` object
`Cdm.ReadFromString(xml)`	Parse a CDM XML string
`Cdm.ReadFromStream(stream)`	Parse from a stream
`Cdm.ValidateSchema(path)`	Validate a CDM file against the CCSDS schema
`Cdm.ValidateSchemaFromXml(xml)`	Validate a CDM XML string against the schema

Instance Methods¶

Method	Description
`WriteToFile(path)`	Serialize the CDM to an XML file
`WriteToString()`	Serialize the CDM to an XML string

Supporting Types¶

Type	Description
`CdmWriter`	Direct object-to-XML writer
`CdmReader`	Direct XML-to-object reader
`CdmValidator`	Schema and content validation

Export from EncounterCase¶

EncounterCase.ToCdm(CdmExportOptions) converts a conjunction assessment result directly into a Cdm object.

CdmExportOptions¶

Property	Type	Description
`Originator`	`string`	Originating organization
`MessageId`	`string`	Unique message identifier
`MessageFor`	`string`	Intended recipient
`CollisionProbabilityMethod`	`string`	Overrides the method name, `FOSTER-2D` by default
`AllowStaleCovariance`	`bool`	Allows exporting an encounter flagged `StaleCovarianceUsed` (refused by default)

The covariance of each participant is resolved as in the conjunction analysis: the covariance at TCA, otherwise the initial-state covariance held fixed in RTN (not propagated). In the second case a comment gives its age at TCA. See Conjunction Assessment.

Reference frame¶

States in Frame.ICRF (SPICE J2000) and Frame.GCRF are written with REF_FRAME = GCRF. Both frames share the ICRF axes, so the label is exact and the same state gives the same CDM content in either frame. A state in a frame named EME2000 is labelled EME2000, and a state in ITRF93 is labelled ITRF.

Unit Conversion¶

The managed API stores values internally in SI units. The CDM writer emits CCSDS-required XML units:

Quantity	Internal (SI)	CDM (XML)
Position (state vector)	m	km
Velocity	m/s	km/s
Miss distance	m	m
Relative position	m	m

Standards-compliant CDM export requires covariance for both participants, so the exported COLLISION_PROBABILITY_METHOD is FOSTER-2D.

Example¶

using IO.Astrodynamics.CCSDS.CDM;

var cdm = encounter.ToCdm(new CdmExportOptions
{
    Originator = "MyOpsCenter",
    MessageId = "CDM-20260315-001",
    MessageFor = "Protected"
});

cdm.WriteToFile("encounter.cdm.xml");

var validation = Cdm.ValidateSchema("encounter.cdm.xml");
if (!validation.IsValid)
    throw new InvalidOperationException("CDM failed schema validation.");

var parsed = Cdm.ReadFromFile("encounter.cdm.xml");