VALAR supports industry-standard file formats for importing and exporting spacecraft orbital data, tracking observations, maneuver plans, and conjunction information. Most formats follow CCSDS (Consultative Committee for Space Data Systems) standards, ensuring interoperability with other space agencies, operators, and mission control systems worldwide.
VALAR supports seven primary file formats, each designed for specific operational needs:
| Format | Full Name | Primary Use | Data Type | Standard |
|---|
| OPM | Orbit Parameter Message | State vector snapshots | Single-epoch orbital state | CCSDS 502.0-B-3 |
| OEM | Orbit Ephemeris Message | Trajectory time series | Position/velocity over time | CCSDS 502.0-B-3 |
| OCM | Orbit Comprehensive Message | Mission planning | Comprehensive orbital data | CCSDS 502.0-B-3 |
| TDM | Tracking Data Message | Orbit determination | Ground-based observations | CCSDS 503.0-B-2 |
| CDM | Conjunction Data Message | Collision assessment | Conjunction event data | CCSDS 508.0-B-1 |
| TLE | Two-Line Element | Catalog data | Mean orbital elements | NORAD/Space-Track |
| SP3 | Standard Product 3 | Precise GNSS orbits | Multi-satellite ephemeris | IGS SP3-c |
- OPM: Single orbital state at a specific epoch, optionally with spacecraft properties and one maneuver
- OEM: Time series of orbital states with interpolation support for continuous trajectories
- OCM: Comprehensive format combining state history, maneuvers, physical properties, and force models
- SP3: Multi-satellite ephemeris with integrated clock corrections, primarily used for GNSS precise orbits
These formats contain raw or processed measurement data from ground sensors:
- TDM: Tracking observations (angles, range) from ground stations or optical telescopes
- CDM: Conjunction analysis results with collision probability and miss distance
- TLE: Public catalog format using simplified perturbation models (SGP4/SDP4)
I want to…
Share a spacecraft state vector
→ Use OPM for a single-epoch snapshot
Provide a pre-computed trajectory
→ Use OEM for a time series of state vectors
Import/export maneuver plans
→ Use OCM for comprehensive maneuver sequences
Upload measurements for orbit determination
→ Use TDM for observation data from ground sensors
Analyze conjunction events
→ Use CDM for collision assessment information
Work with public catalog data
→ Use TLE format (note: VALAR does not import TLEs directly)
Import precise GNSS or LEO satellite orbits
→ Use SP3 for IGS or similar precise orbit products
Temporal Scope
| Format | Time Coverage | Typical Use |
|---|
| OPM | Single epoch | State snapshots, OD results |
| OEM | Time series | Ephemeris generation, trajectory sharing |
| OCM | Single or multiple epochs | Mission planning, comprehensive state |
| TDM | Observation period | Tracking passes, sensor data |
| CDM | Event-specific | Conjunction analysis |
| TLE | Single epoch (mean elements) | Catalog distribution |
| SP3 | Time series | Precise GNSS orbits, PPP applications |
Data Complexity
| Format | Complexity | Required Information | Optional Information |
|---|
| OPM | Low | State vector, epoch, reference frame | Keplerian elements, maneuver, covariance |
| OEM | Medium | State vectors, epochs, interpolation method | Covariance time series |
| OCM | High | Metadata, reference frame | Trajectory, maneuvers, physical properties, perturbations |
| TDM | Medium | Observations, participants, measurement types | Corrections, atmospheric data |
| CDM | Medium | TCA, miss distance, state vectors | Covariance, collision probability |
| TLE | Low | Orbital elements, NORAD catalog number | None |
| SP3 | Medium | Satellite IDs, positions, epochs, time system | Velocities, clock corrections, correlations |
Common Use Cases by Mission Phase
| Mission Phase | Recommended Format | Alternative |
|---|
| Pre-Launch Planning | OCM (maneuver plans) | OPM (state snapshots) |
| Early Orbit | TDM (tracking) → OPM (OD results) | OEM (trajectory) |
| Station-Keeping | OCM (maneuver sequences) | OPM (single burns) |
| Conjunction Assessment | CDM (from screening services) | OEM (predicted trajectory) |
| End-of-Life | OEM (decay trajectory) | OPM (final state) |
| Data Archiving | OEM (historical trajectory) | TDM (raw observations) |
OPM (Orbit Parameter Message)
Purpose: Exchange single-epoch orbital states with optional spacecraft parameters and a single maneuver.
Key Features:
- Cartesian state vectors or Keplerian elements
- Spacecraft physical properties (mass, area, coefficients)
- Optional single impulsive maneuver
- Optional covariance matrix
Supported Variants:
- CCSDS OPM: Standard format using inertial reference frames (EME2000, GCRF)
- SpaceX OPM: Proprietary format from Falcon second stage telemetry using ECEF coordinates
When to Use:
- Sharing orbit determination results
- Providing initial conditions for propagation
- Exchanging state vectors between systems
- Importing launch vehicle separation states (SpaceX OPM)
Read OPM documentation →
OEM (Orbit Ephemeris Message)
Purpose: Share pre-computed spacecraft trajectories as time-ordered position and velocity data.
Key Features:
- Time series of Cartesian state vectors
- Interpolation methods (Hermite, Lagrange, Linear)
- Optional covariance matrices at each epoch
- Multiple data segments for different time periods
When to Use:
- Conjunction assessment coordination
- Trajectory sharing between control centers
- High-precision ephemeris distribution
- Orbit visualization and analysis
Read OEM documentation →
OCM (Orbit Comprehensive Message)
Purpose: Comprehensive mission planning format combining orbital states, maneuvers, spacecraft properties, and force model specifications.
Key Features:
- Multiple trajectory state blocks
- Multiple maneuver definitions (impulsive and continuous thrust)
- Maneuver sequencing (MAN_PREV_ID, MAN_NEXT_ID)
- Physical properties, covariance time history
- Perturbation parameters, user-defined data
When to Use (in VALAR):
- Import maneuvers from external sources
- Export maneuver plans for coordination with other agencies
VALAR uses OCM specifically for maneuver import/export. Other OCM sections (trajectory, physical properties, covariance) are not currently supported.
TDM (Tracking Data Message)
Purpose: Exchange ground-based tracking observations for orbit determination.
Key Features:
- Multiple measurement types (angles, range, frequency)
- Angle types: AZEL (radar), RADEC (optical), XEYN, XSYE
- Signal path specification (one-way, two-way)
- Multi-segment support for multiple tracking stations
- Metadata for corrections and biases
When to Use:
- Uploading measurements for orbit determination
- Sharing observation data from ground sensors
- Multi-station tracking campaigns
- Validating predicted trajectories against observations
Sensor configuration in VALAR must match PARTICIPANT_1 field in TDM metadata. Configure ground stations before importing TDM files.
CDM (Conjunction Data Message)
Purpose: Exchange conjunction assessment results for collision risk evaluation.
Key Features:
- Time of Closest Approach (TCA)
- Miss distance and relative velocity
- Collision probability
- State vectors and covariances for both objects
- Screening volume information
When to Use:
- Receiving conjunction warnings from Space-Track or other screening services
- Coordinating collision avoidance maneuvers
- Analyzing conjunction geometry
- Risk assessment for operational spacecraft
Read CDM documentation →
TLE (Two-Line Element)
Purpose: Compact format for distributing mean orbital elements from public satellite catalogs.
Key Features:
- Fixed 69-character line format
- Mean orbital elements (not osculating)
- BSTAR drag term for atmospheric decay
- Requires SGP4/SDP4 propagation models
- Distributed by Space-Track, CelesTrak
Important Notes:
- TLE accuracy degrades rapidly (days to weeks depending on orbit)
- TEME reference frame (non-standard)
- Mean elements, not instantaneous orbital state
- VALAR does not support direct TLE import
If you need to use TLE data:
- Use external SGP4/SDP4 library to propagate TLE
- Convert resulting state from TEME to GCRF or ITRF
- Import the state vector into VALAR as OPM format
Read TLE documentation →
SP3 (Standard Product 3)
Purpose: Distribute precise satellite orbits and clock corrections, primarily for GNSS constellations and LEO satellites.
Key Features:
- Multi-satellite support (up to 85 satellites per file)
- Integrated clock corrections at each epoch
- Multiple GNSS systems (GPS, GLONASS, Galileo, BeiDou, QZSS)
- LEO satellite support
- Optional velocity and correlation records
- Accuracy information via exponents and standard deviations
When to Use:
- Importing IGS precise orbit products
- Working with GNSS satellite ephemerides
- Precise Point Positioning (PPP) applications
- Orbit comparison and validation against IGS products
SP3 is an IGS (International GNSS Service) standard, not a CCSDS format. It is widely used in the geodetic and GNSS communities.
CCSDS Standards
Most formats follow CCSDS (Consultative Committee for Space Data Systems) recommendations:
- CCSDS 502.0-B-3: Orbit Data Messages (OPM, OEM, OCM, OMM)
- CCSDS 503.0-B-2: Tracking Data Message (TDM)
- CCSDS 508.0-B-1: Conjunction Data Message (CDM)
Other Standards
- IGS SP3-c: Standard Product 3 format for precise GNSS orbits and clocks
These standards ensure global interoperability between:
- Space agencies (NASA, ESA, JAXA, etc.)
- Commercial satellite operators
- Ground station networks
- Mission control centers
- Orbit determination systems
CCSDS formats support two representations:
KVN (Keyword-Value Notation)
- Human-readable ASCII text format
- Easier to parse and debug
- Smaller file sizes
- Preferred for operational use
- VALAR uses KVN format
XML (Extensible Markup Language)
- Structured hierarchical format
- Machine-readable with schema validation
- Better for complex nested data
- Common in enterprise systems
All examples in VALAR documentation use KVN format.
Reference Frames and Time Systems
All CCSDS formats specify reference frames and time systems explicitly:
Common Reference Frames
| Frame | Type | Use Case |
|---|
| GCRF | Inertial | Orbit propagation, recommended for most purposes |
| EME2000 | Inertial | Legacy systems, CCSDS file compatibility |
| ITRF | Earth-fixed | Ground tracks, ground station coordinates |
| RTN | Local Orbital | Maneuver planning (radial-tangential-normal) |
| LVLH | Local Orbital | Formation flying, relative guidance |
Common Time Systems
| Time System | Description | Use Case |
|---|
| UTC | Coordinated Universal Time | Operational tracking, most common |
| TAI | International Atomic Time | High-precision applications |
| GPS | GPS Time | GPS-based navigation |
| TDB | Barycentric Dynamical Time | Deep space missions |
Best Practices
File Import/Export
- Validate before sharing: Ensure files conform to CCSDS standards
- Include comments: Document assumptions, corrections, and data sources
- Specify units explicitly: Don’t rely on default unit assumptions
- Use appropriate precision: Match numerical precision to accuracy requirements
- Test round-trip: Verify data integrity through import/export cycles
- Match format to purpose: Don’t use OCM when OPM suffices
- Consider file size: OEM files can be large for long time spans
- Document extensions: If using non-standard fields, provide ICD documentation
- Standardize internally: Use consistent formats within your organization
- Maintain compatibility: Verify receiving systems support your format choices
Reference Frame Selection
- Use GCRF for propagation: Modern inertial frame, well-defined
- Use ITRF for ground operations: Earth-fixed frame for station coordinates
- Document LOF definitions: LVLH, RTN naming varies between organizations
- Convert early: Transform non-standard frames (TEME) to standard frames quickly
Time System Selection
- Prefer UTC for operations: Most universally understood
- Use TAI for precision work: Avoids leap second discontinuities
- Document time system clearly: Ambiguity causes significant errors
- Maintain consistency: Don’t mix time systems within a file
Getting Help
For detailed information about each format:
- Browse individual format documentation pages
- Consult CCSDS specifications (linked in each format page)
- Review example files provided in documentation
- Contact VALAR support for import/export questions
For questions about which format to use for your specific use case, consult the format selection guide above or reach out to support. 