OCM (Orbit Comprehensive Message)

For the complete documentation index, see llms.txt.

The Orbit Comprehensive Message (OCM) is the most feature-rich standardized format for exchanging spacecraft orbital information. Unlike OPM (single-epoch state) and OEM (ephemeris time series), OCM combines multiple data types into a single comprehensive message, supporting trajectory state history, spacecraft physical properties, covariance time history, multiple maneuvers, perturbation parameters, and user-defined data.

Why OCM is “Comprehensive”

OCM aggregates and extends the capabilities of OPM, OMM, and OEM into one unified format:

Multiple Trajectory States: Time series of state vectors or Keplerian elements (like OEM)
Single-Epoch States: State snapshots at specific times (like OPM)
Multiple Maneuvers: Comprehensive maneuver planning with impulsive and continuous thrust
Physical Properties: Spacecraft mass, area, drag/SRP coefficients, attitude information
Covariance Time History: Uncertainty evolution over time
Perturbation Parameters: Force model configuration for propagation
User-Defined Data: Custom parameters for mission-specific needs
Parent-Child Scenarios: Support for deployment and separation events

OCM is the recommended format when you need to exchange comprehensive mission planning data, including orbital states, maneuver plans, spacecraft properties, and uncertainties in a single file.

Key Components

An OCM file contains several distinct sections (all optional except Header and Metadata):

Header: File-level metadata (format version, creation date, originator)
Metadata: Mission context (object identification, time system, reference frame)
Trajectory State Time History: Cartesian state vectors or Keplerian elements over time
Physical Descriptor: Spacecraft physical properties (mass, area, drag coefficient, etc.)
Covariance Time History: Position/velocity uncertainty matrices over time
Maneuver Parameters: Multiple maneuver definitions (impulsive or continuous thrust)
Perturbation Parameters: Force model specification for propagation
Orbit Determination Parameters: OD configuration and results
User-Defined Parameters: Custom mission-specific data

Structure Overview

OCM Hierarchy

OCM File
├── Header (CCSDS_OCM_VERS, CREATION_DATE, ORIGINATOR)
├── Metadata Section (META_START to META_STOP)
│   ├── Time system, reference frame
│   ├── Object identification
│   ├── Epoch reference (EPOCH_TZERO)
│   └── Trajectory interpolation settings
├── Trajectory State Blocks (TRAJ_START to TRAJ_STOP) [Optional]
│   └── Multiple state vector or Keplerian element time series
├── Physical Descriptor Block (PHYS_START to PHYS_STOP) [Optional]
│   └── Mass, area, attitude, drag/SRP coefficients
├── Covariance Blocks (COV_START to COV_STOP) [Optional]
│   └── Time series of covariance matrices
├── Maneuver Blocks (MAN_START to MAN_STOP) [Optional]
│   └── Multiple maneuver definitions with unique IDs
├── Perturbation Block (PERT_START to PERT_STOP) [Optional]
│   └── Force model configuration
├── Orbit Determination Block (OD_START to OD_STOP) [Optional]
│   └── OD settings and results
└── User-Defined Block (USER_START to USER_STOP) [Optional]
    └── Custom parameters

Metadata Fields

Required Metadata

Field	Description	Example Values
TIME_SYSTEM	Time system for all epochs	UTC, TAI, GPS
EPOCH_TZERO	Reference epoch for relative times	2024-01-01T00:00:00

Object Identification

Field	Description	Example
OBJECT_NAME	Spacecraft common name	SPACECRAFT-ALPHA
INTERNATIONAL_DESIGNATOR	COSPAR ID	2023-001A
CATALOG_NAME	Catalog identifier source	SATCAT
OBJECT_DESIGNATOR	Object ID in catalog	12345

Trajectory Configuration

Field	Description	Values
REF_FRAME	Reference frame for states	GCRF, EME2000, ITRF
REF_FRAME_EPOCH	Epoch for reference frame	J2000 epoch
TRAJ_TYPE	Trajectory representation	CARTESIAN, KEPLERIAN, GEODETIC
TRAJ_UNITS	Units for trajectory data	[km, km, km, km/s, km/s, km/s]

EPOCH_TZERO serves as the time origin for all relative time references in the OCM. Absolute times can also be used where appropriate.

Trajectory State Time History

OCM supports time series of orbital states in multiple representations:

Cartesian State Vectors

TRAJ_START
TRAJ_TYPE   = CARTESIAN
TRAJ_UNITS  = [km, km, km, km/s, km/s, km/s]

EPOCH       X           Y           Z           X_DOT       Y_DOT       Z_DOT
+0.000      6655.994    -40218.575  -82.918     3.115482    0.470426    -0.001015
+3600.000   6892.441    -39845.123  -76.234     3.087234    0.501287    -0.000923
+7200.000   7112.873    -39458.892  -69.445     3.058012    0.531456    -0.000831
TRAJ_STOP

Keplerian Elements

TRAJ_START
TRAJ_TYPE   = KEPLERIAN
TRAJ_UNITS  = [km, n/a, deg, deg, deg, deg]

EPOCH       SEMI_MAJOR_AXIS  ECCENTRICITY  INCLINATION  RA_ASC_NODE  ARG_PERICENTER  TRUE_ANOMALY
+0.000      42164.140        0.0001234     0.05         75.123       180.456         90.789
+3600.000   42164.245        0.0001245     0.05         75.234       180.567         95.123
TRAJ_STOP

Time values can be:

Absolute: Full ISO 8601 timestamp
Relative: Offset in seconds from EPOCH_TZERO (indicated by + or - prefix)

Physical Descriptor Block

Spacecraft physical properties for accurate propagation:

PHYS_START
WET_MASS            = 2000.000 [kg]
DRY_MASS            = 1850.000 [kg]
SRP_CONST_AREA      = 10.000 [m**2]
SOLAR_RAD_COEFF     = 1.300
DRAG_CONST_AREA     = 10.000 [m**2]
DRAG_COEFF_NOM      = 2.300
OEB_PARENT_FRAME    = SPACECRAFT_BODY
OEB_Q1              = 0.707
OEB_Q2              = 0.000
OEB_Q3              = 0.000
OEB_QC              = 0.707
PHYS_STOP

Key Physical Parameters

Parameter	Description	Units
WET_MASS	Fully fueled mass	kg
DRY_MASS	Mass without propellant	kg
SRP_CONST_AREA	Cross-sectional area for solar radiation pressure	m²
SOLAR_RAD_COEFF	SRP coefficient (typically 1.0-1.5)	dimensionless
DRAG_CONST_AREA	Cross-sectional area for atmospheric drag	m²
DRAG_COEFF_NOM	Nominal drag coefficient (typically 2.0-2.5)	dimensionless
OEB_Q1, Q2, Q3, QC	Attitude quaternion	dimensionless

Covariance Time History

OCM supports time-varying covariance matrices to represent uncertainty evolution:

COV_START
COV_TYPE        = CARTESIAN
COV_ORDERING    = LTRI
COV_UNITS       = [km**2, km**2, km**2, km**2/s**2, km**2/s**2, km**2/s**2]

EPOCH           CX_X    CY_X    CY_Y    CZ_X    CZ_Y    CZ_Z
+0.000          4.142e+01  -8.579e+00  5.189e+01  -4.788e+01  -4.472e+01  5.960e+01

EPOCH           CX_DOT_X    CX_DOT_Y    CX_DOT_Z    CX_DOT_X_DOT
+0.000          3.523e-03   1.045e-03   -1.234e-03  8.945e-07

EPOCH           CY_DOT_X    CY_DOT_Y    CY_DOT_Z    CY_DOT_X_DOT    CY_DOT_Y_DOT
+0.000          -2.678e-03  -5.234e-04  1.876e-03   -3.456e-07      7.234e-07

EPOCH           CZ_DOT_X    CZ_DOT_Y    CZ_DOT_Z    CZ_DOT_X_DOT    CZ_DOT_Y_DOT    CZ_DOT_Z_DOT
+0.000          -1.234e-03  2.345e-03   -8.765e-04  2.134e-07       -4.567e-07      6.789e-07
COV_STOP

The covariance matrix is stored in lower-triangular form, representing the 6×6 position-velocity uncertainty.

Maneuver Parameters

OCM’s most powerful feature is comprehensive maneuver specification supporting both impulsive and continuous thrust maneuvers.

Impulsive Maneuver

A single instantaneous velocity change:

MAN_START
MAN_ID              = MAN-001
MAN_DEVICE_ID       = THRUSTER-PRIMARY
MAN_PREV_ID         = N/A
MAN_NEXT_ID         = MAN-002
MAN_REF_FRAME       = RTN
MAN_FRAME_EPOCH     = 2024-06-03T09:00:00.000

DC_TYPE             = IMPULSIVE
MAN_COMPOSITION     = TIME_ABSOLUTE, MAN_DV_1, MAN_DV_2, MAN_DV_3
MAN_UNITS           = [s, km/s, km/s, km/s]

2024-06-03T09:00:34.100  -0.02325700  0.01683160  -0.00893444
MAN_STOP

Continuous Thrust Maneuver

Extended burn with time-varying thrust profile:

MAN_START
MAN_ID              = MAN-002
MAN_DEVICE_ID       = THRUSTER-ION
MAN_REF_FRAME       = RTN
DC_TYPE             = CONTINUOUS
MAN_COMPOSITION     = TIME_ABSOLUTE, MAN_DURA, THR_X, THR_Y, THR_Z, THR_ISP, DELTA_MASS
MAN_UNITS           = [s, s, N, N, N, s, kg]

2024-06-04T01:10:00.000  500.0  0.0000  0.0650  0.0000  3000.0  -0.78
2024-06-04T01:20:00.000  500.0  0.0000  0.0000  0.0650  3000.0  -0.78
2024-06-04T01:30:00.000  500.0  0.0650  0.0000  0.0000  3000.0  -0.78
MAN_STOP

Maneuver Metadata Fields

Field	Description	Values
MAN_ID	Unique maneuver identifier	MAN-001, BURN-A, etc.
MAN_BASIS	Optional CCSDS provenance metadata	Does not classify a stored VALAR record or select import behavior; omitted on export
MAN_DEVICE_ID	Thruster or device ID	Thruster name or ALL
MAN_PREV_ID	Previous maneuver in sequence	MAN_ID or N/A
MAN_NEXT_ID	Next maneuver in sequence	MAN_ID or N/A
MAN_REF_FRAME	Reference frame for delta-V	RTN, LVLH, TNW, inertial
DC_TYPE	Maneuver type	IMPULSIVE, CONTINUOUS

MAN_COMPOSITION — Customizable Data Columns

The MAN_COMPOSITION field defines which data columns appear in the maneuver data rows. This allows flexible maneuver specification tailored to the mission needs. Common composition fields:

Field	Description	Typical Units
TIME_ABSOLUTE	Absolute time stamp	ISO 8601 string
TIME_RELATIVE	Time relative to EPOCH_TZERO	seconds
MAN_DURA	Burn duration	seconds
MAN_DV_1, MAN_DV_2, MAN_DV_3	Delta-V components	km/s
THR_X, THR_Y, THR_Z	Thrust components	Newtons
THR_MAG	Thrust magnitude	Newtons
THR_ISP	Specific impulse	seconds
DELTA_MASS	Mass change (negative for consumption)	kg
THR_EFFICIENCY	Thruster efficiency	0.0 to 1.0

The order of fields in MAN_COMPOSITION must exactly match the order of data columns in subsequent maneuver data rows. Units must be specified in MAN_UNITS in the same order.

Maneuver Chaining

OCM supports maneuver sequences through MAN_PREV_ID and MAN_NEXT_ID, enabling:

Maneuver dependency tracking
Sequence validation
Mission timeline reconstruction

Perturbation Parameters

Define the force model configuration for orbit propagation:

PERT_START
ATMOSPHERIC_MODEL       = NRLMSISE00
GRAVITY_MODEL           = EGM-96: 70D 70O
EQUATORIAL_RADIUS       = 6378.137 [km]
GM                      = 398600.4415 [km**3/s**2]
N_BODY_PERTURBATIONS    = SUN, MOON
SOLAR_RAD_PRESSURE      = YES
SOLID_EARTH_TIDES       = YES
OCEAN_TIDES             = YES
THIRD_BODY_GRAVITY      = YES
PERT_STOP

Perturbation Parameters

Parameter	Description	Example Values
ATMOSPHERIC_MODEL	Atmospheric density model	NRLMSISE00, JB2008, Harris-Priester
GRAVITY_MODEL	Geopotential model with degree/order	EGM-96: 70D 70O, WGS84: 8D 8O
GM	Gravitational parameter	398600.4415 km³/s²
N_BODY_PERTURBATIONS	Third-body perturbations	SUN, MOON, JUPITER
SOLAR_RAD_PRESSURE	Include SRP	YES, NO
SOLID_EARTH_TIDES	Include solid Earth tides	YES, NO
OCEAN_TIDES	Include ocean tides	YES, NO

Perturbation parameters ensure the receiving system can accurately propagate the orbit using the same force model configuration as the originating system.

User-Defined Parameters

OCM allows custom parameters for mission-specific data:

USER_START
USER_PARAM_1 = MISSION_PHASE
USER_VALUE_1 = OPERATIONAL
USER_PARAM_2 = BATTERY_SOC
USER_VALUE_2 = 87.5 [%]
USER_PARAM_3 = CONTACT_FREQUENCY
USER_VALUE_3 = 2.2e9 [Hz]
USER_STOP

User-defined parameters should be used sparingly and documented in Interface Control Documents (ICDs). Their meaning must be clearly communicated to all parties exchanging the OCM file.

Common Use Cases

Comprehensive Mission Planning: Complete mission state including trajectory, maneuvers, and spacecraft properties
Maneuver Sequencing: Planning and tracking multiple burn sequences
Conjunction Data Submission: Providing detailed orbital information to conjunction assessment services
Formation Flying: Parent-child deployment scenarios and relative state information
Mission Handover: Comprehensive state transfer between control centers
Long-Duration Missions: Time-varying properties (mass, drag coefficient) over mission lifetime
High-Fidelity Propagation: Providing complete force model and spacecraft parameters

Complete definition of the OCM standard in CCSDS 502.0-B-3 specification.

Complete OCM Example

Here is a comprehensive OCM file demonstrating multiple features:

CCSDS_OCM_VERS     = 3.0
CREATION_DATE      = 2024-06-15T08:30:00.000
ORIGINATOR         = VALAR

COMMENT Comprehensive mission planning file
COMMENT Includes trajectory, maneuvers, and physical properties

META_START
TIME_SYSTEM        = UTC
EPOCH_TZERO        = 2024-06-15T00:00:00.000
OBJECT_NAME        = SPACECRAFT-GAMMA
INTERNATIONAL_DESIGNATOR = 2024-001A
CATALOG_NAME       = SATCAT
OBJECT_DESIGNATOR  = 59234
REF_FRAME          = EME2000
TRAJ_TYPE          = CARTESIAN
TRAJ_UNITS         = [km, km, km, km/s, km/s, km/s]
META_STOP

COMMENT Initial trajectory state history

TRAJ_START
EPOCH       X           Y           Z           X_DOT       Y_DOT       Z_DOT
+0.000      6655.994    -40218.575  -82.918     3.115482    0.470426    -0.001015
+3600.000   6892.441    -39845.123  -76.234     3.087234    0.501287    -0.000923
+7200.000   7112.873    -39458.892  -69.445     3.058012    0.531456    -0.000831
TRAJ_STOP

COMMENT Spacecraft physical properties

PHYS_START
WET_MASS            = 2000.000 [kg]
DRY_MASS            = 1850.000 [kg]
SRP_CONST_AREA      = 10.000 [m**2]
SOLAR_RAD_COEFF     = 1.300
DRAG_CONST_AREA     = 10.000 [m**2]
DRAG_COEFF_NOM      = 2.300
PHYS_STOP

COMMENT First orbit-raising maneuver

MAN_START
MAN_ID              = RAISE-PERIGEE-1
MAN_DEVICE_ID       = THRUSTER-MAIN
MAN_PREV_ID         = N/A
MAN_NEXT_ID         = RAISE-APOGEE-1
MAN_REF_FRAME       = RTN
DC_TYPE             = IMPULSIVE
MAN_COMPOSITION     = TIME_ABSOLUTE, MAN_DV_1, MAN_DV_2, MAN_DV_3
MAN_UNITS           = [s, km/s, km/s, km/s]

2024-06-15T09:00:34.100  0.05234000  0.00124500  -0.00012300
MAN_STOP

COMMENT Second orbit-raising maneuver

MAN_START
MAN_ID              = RAISE-APOGEE-1
MAN_DEVICE_ID       = THRUSTER-MAIN
MAN_PREV_ID         = RAISE-PERIGEE-1
MAN_NEXT_ID         = CIRCULARIZE-1
MAN_REF_FRAME       = RTN
DC_TYPE             = IMPULSIVE
MAN_COMPOSITION     = TIME_ABSOLUTE, MAN_DV_1, MAN_DV_2, MAN_DV_3
MAN_UNITS           = [s, km/s, km/s, km/s]

2024-06-15T21:45:12.300  0.04876000  -0.00087600  0.00023400
MAN_STOP

COMMENT Circularization burn using low-thrust ion propulsion

MAN_START
MAN_ID              = CIRCULARIZE-1
MAN_DEVICE_ID       = ION-THRUSTER-1
MAN_PREV_ID         = RAISE-APOGEE-1
MAN_NEXT_ID         = N/A
MAN_REF_FRAME       = RTN
DC_TYPE             = CONTINUOUS
MAN_COMPOSITION     = TIME_ABSOLUTE, MAN_DURA, THR_X, THR_Y, THR_Z, THR_ISP, DELTA_MASS
MAN_UNITS           = [s, s, N, N, N, s, kg]

2024-06-16T10:00:00.000  600.0  0.0000  0.0850  0.0000  3200.0  -0.92
2024-06-16T10:10:00.000  600.0  0.0000  0.0850  0.0000  3200.0  -0.92
2024-06-16T10:20:00.000  600.0  0.0000  0.0850  0.0000  3200.0  -0.92
MAN_STOP

COMMENT Perturbation parameters for propagation

PERT_START
ATMOSPHERIC_MODEL       = NRLMSISE00
GRAVITY_MODEL           = EGM-96: 70D 70O
EQUATORIAL_RADIUS       = 6378.137 [km]
GM                      = 398600.4415 [km**3/s**2]
N_BODY_PERTURBATIONS    = SUN, MOON
SOLAR_RAD_PRESSURE      = YES
SOLID_EARTH_TIDES       = YES
OCEAN_TIDES             = NO
PERT_STOP

VALAR Import Requirements

VALAR uses OCM as its file format for importing and exporting maneuver data. When importing an OCM file, VALAR validates several requirements beyond the base CCSDS standard. This section is the canonical reference for all import validation rules.

VALAR uses OCM exclusively for maneuver data. Other OCM sections (trajectory state history, covariance, perturbation parameters, orbit determination, user-defined parameters) are parsed but not imported.

File Requirements

Requirement	Details
Format	OCM (CCSDS 502.0-B-3), KVN notation
Maximum file size	52 MB; the complete multipart request also has a 52 MB limit
Content	File must not be empty and must contain at least one maneuver block

Required Maneuver Fields

Every maneuver block (MAN_START to MAN_STOP) must include the following fields:

Field	Requirement
`MAN_ID`	Must not contain RFC 3986 reserved characters: `! * ' ( ) ; : @ & = + $ , / ? # [ ]`
`MAN_REF_FRAME`	Required. Must be one of the supported reference frames listed below.
`THR_X`, `THR_Y`, `THR_Z`	Required in the maneuver composition. At least one thrust component must be non-zero.
`THR_ISP`	Required. Specific impulse must be between 50 and 10,000 seconds. A value of zero is not accepted.

MAN_BASIS is optional format metadata. When supplied, it must be parseable as CCSDS metadata; the customary TELEMETRY spelling is accepted as DETERMINED_TLM. Its value does not select an import mode, become a stored classification, or authorize replacement of records. Maneuver blocks do not need a uniform basis. Generic VALAR exports omit this field. Stored burn segments also require an epoch and a positive finite duration. The general OCM examples above illustrate the format; delta-V-only impulsive examples do not meet VALAR’s thrust, ISP, and duration requirements for stored maneuver imports.

Specific impulse values outside the 50–10,000 second range will be rejected. This range covers all common propulsion technologies, from cold-gas thrusters (~50 s) to advanced ion engines (~10,000 s).

Physical Properties

Your OCM file must include a physical properties block (PHYS_START to PHYS_STOP) with the WET_MASS field:

PHYS_START
WET_MASS = 2000.000 [kg]
PHYS_STOP

Supported Reference Frames

The MAN_REF_FRAME field must use one of the following frames. Inertial Frames:

Frame	Alias
`EME2000`	Also accepted as `J2000`
`GCRF`
`ICRF`
`ITRF`
`TOD`
`TEME`
`MOD`

Local Orbital Frames:

Frame	Alias
`RTN`	Also accepted as `RIC`
`TNW`
`QSW`	Also accepted as `VNC`

If your OCM file uses J2000, VNC, or RIC as the reference frame, VALAR automatically maps them to their canonical equivalents (EME2000, QSW, and RTN respectively).

Spacecraft Matching

Select a target spacecraft in the import dialog, or pass its VALAR spacecraftId to the API, when an explicit target is needed. Otherwise VALAR looks for candidates using OCM metadata in this order:

OBJECT_NAME — spacecraft name
INTERNATIONAL_DESIGNATOR — COSPAR ID (e.g., 2024-001A)
OBJECT_DESIGNATOR — NORAD catalog number

The first identifier with candidates resolves the spacecraft only if there is one match. An ambiguous match requires an explicit selection; VALAR does not choose an arbitrary spacecraft. If no identifier matches an accessible spacecraft in the current organization and environment, the import fails. After resolving the spacecraft, file identifiers with corresponding non-null values on the spacecraft record are cross-validated case-insensitively. A mismatch rejects the import, including when you select the spacecraft explicitly.

Before importing, verify that the OBJECT_NAME, INTERNATIONAL_DESIGNATOR, or OBJECT_DESIGNATOR in your OCM file matches what is configured on the spacecraft details page in VALAR.

Consistency Rules

Unique identities: Each MAN_ID must be new for the target spacecraft, both within the file and relative to existing stored records.
No temporal overlaps: Enclosing maneuver intervals within the file and relative to stored records on the same spacecraft must not intersect, including gaps between a record’s segments. Two maneuvers may share an endpoint (one ends exactly when the next begins).

Import Behavior

Import adds records. Each file is atomic: if a record fails validation or conflicts, none of that file is saved. Other successfully imported files remain saved. Review per-file outcomes before retrying. Duplicate identities and overlaps with stored records are rejected with MANEUVER_CONFLICT. To change a record manually, use Edit on the Maneuvers page. A name edit does not change the stable identity or exported MAN_ID. Through the Maneuver API, prepare corrected OCM, explicitly delete the stored record, then import the corrected file. These are separate operations, not an atomic replacement: a failed import leaves the record deleted. Import does not overwrite existing records, and all file and physical validation still applies. Conflicts require an explicit edit or delete; import never merges, trims, or deletes another record. Pre-existing overlaps remain viewable in the application and exportable, but an application edit or a corrected import must satisfy the non-overlap rule.

Exporting Maneuvers

OCM Export: Export individual stored maneuvers or a selected time range from VALAR as OCM files
Multi-Maneuver Support: Multiple maneuvers are included in a single OCM file
Standard Compliance: Exported OCM files follow CCSDS 502.0-B-3 specification
Interoperability: OCM format enables maneuver data exchange with external systems and agencies
Identity: MAN_ID stays fixed after name edits; optional MAN_BASIS is omitted

Best Practices

Data Organization

Use EPOCH_TZERO effectively: Set to mission start or a significant epoch for cleaner relative times
Include physical properties: Always provide mass, area, and coefficient data for accurate propagation
Document maneuver sequences: Use MAN_PREV_ID and MAN_NEXT_ID to chain related maneuvers

Maneuver Specification

Choose appropriate DC_TYPE: IMPULSIVE for chemical burns, CONTINUOUS for ion/low-thrust
Specify reference frames clearly: Document whether RTN, LVLH, or other LOF is used
Include all composition fields: Don’t omit important fields like DELTA_MASS or THR_ISP

File Quality

Add comments liberally: Explain mission phases, maneuver purposes, assumptions
Validate before sharing: Ensure all referenced IDs exist and data is self-consistent
Use appropriate units: Follow CCSDS conventions and specify units explicitly in MAN_UNITS

Interoperability

Minimize user-defined parameters: Use standard fields whenever possible
Document extensions: If using USER blocks, provide clear documentation in ICDs
Test interchange: Check supported burn values on import/export. Optional classification metadata is not retained, and importing an identity already stored on the target spacecraft is rejected.

Comparison with Other Formats

Feature	OCM	OPM	OEM	TDM
Data Type	Comprehensive	Single state	Ephemeris	Observations
Temporal Scope	Time series + snapshots	Single epoch	Time series	Observation period
Maneuvers	Multiple (full specification)	One impulsive	None	None
Physical Properties	Extensive	Basic	None	None
Covariance	Time-varying	Optional single	Optional per epoch	None
Perturbations	Force model specification	None	None	None
Use Case	Mission planning	State exchange	Trajectory sharing	OD input
Complexity	High	Low	Medium	Medium

When to Use OCM

Use OCM when you need:

Multiple maneuvers in a single file
Time-varying spacecraft properties (mass, drag coefficient)
Complete force model specification for propagation
Maneuver sequencing and dependencies
Parent-child deployment scenarios
Comprehensive mission state exchange

Use OPM instead when:

Sharing a simple single-epoch state vector
Only one maneuver needs to be specified
Simplicity and minimal file size are priorities

Use OEM instead when:

Providing pre-computed ephemeris for interpolation
No maneuvers or physical properties needed
Standard trajectory exchange format expected

​Why OCM is “Comprehensive”

​Key Components

​Structure Overview

​OCM Hierarchy

​Metadata Fields

​Required Metadata

​Object Identification

​Trajectory Configuration

​Trajectory State Time History

​Cartesian State Vectors

​Keplerian Elements

​Physical Descriptor Block

​Key Physical Parameters

​Covariance Time History

​Maneuver Parameters

​Impulsive Maneuver

​Continuous Thrust Maneuver

​Maneuver Metadata Fields

​MAN_COMPOSITION — Customizable Data Columns

​Maneuver Chaining

​Perturbation Parameters

​Perturbation Parameters

​User-Defined Parameters

​Common Use Cases

​Complete OCM Example

​VALAR Import Requirements

​File Requirements

​Required Maneuver Fields

​Physical Properties

​Supported Reference Frames

​Spacecraft Matching

​Consistency Rules

​Import Behavior

​Exporting Maneuvers

​Best Practices

​Data Organization

​Maneuver Specification

​File Quality

​Interoperability

​Comparison with Other Formats

​When to Use OCM

Why OCM is “Comprehensive”

Key Components

Structure Overview

OCM Hierarchy

Metadata Fields

Required Metadata

Object Identification

Trajectory Configuration

Trajectory State Time History

Cartesian State Vectors

Keplerian Elements

Physical Descriptor Block

Key Physical Parameters

Covariance Time History

Maneuver Parameters

Impulsive Maneuver

Continuous Thrust Maneuver

Maneuver Metadata Fields

MAN_COMPOSITION — Customizable Data Columns

Maneuver Chaining

Perturbation Parameters

Perturbation Parameters

User-Defined Parameters

Common Use Cases

Complete OCM Example

VALAR Import Requirements

File Requirements

Required Maneuver Fields

Physical Properties

Supported Reference Frames

Spacecraft Matching

Consistency Rules

Import Behavior

Exporting Maneuvers

Best Practices

Data Organization

Maneuver Specification

File Quality

Interoperability

Comparison with Other Formats

When to Use OCM