How to manage ephemeris
Uploading/submitting OEM Ephemeris data
Definition
An OEM specifies the position and velocity of a single object at multiple epochs contained within a specified time range. The OEM is suited to exchanges that (1) involve automated interaction (e.g., computer-to-computer communication where frequent, fast automated time interpretation and processing is required), and (2) require higher fidelity or higher precision dynamic modeling than is possible with the OPM.
Monitor Space Hazards uses Ephemeris files in .oem format to exchange data from satellite operators to UKSA orbital analysts.
The format of .oem file can be found here: https://public.ccsds.org/Pubs/502x0b2c1e2.pdf
Because of some differences between the .oem format and the way Monitor Space Hazards handles satellite data, Ephemeris files have to be constructed with one thing in mind: the proper file name. Due to the fact that .oem files have different satellite names than SpaceTrack can provide, the satellite descriptor - NORAD ID has to be encoded in the .oem file. This is aligned with the SpaceTrack requirements on naming Ephemeris files and described in SpaceTrack Handbook for Operators (page 23):
https://www.space-track.org/documents/Spaceflight_Safety_Handbook_for_Operators.pdf
The format of a filename is as follows:
<DataType>_<SatelliteNumber#>_<CommonName>_<DayTimeGroup>_<Operational/Special>_<MetaData>_<Classification>.<FileExtension>
Examples:
- MEME_25544_ISS_1651200_oper__unclassified.txt
- MEME_25544_ISS(ZARYA)_1651200_operational_nomnvr_UNCLASSIFIED.txt
- MEME_25544_ISS_1651200_special_mnvr01_Unclassified.txt
- MEME_UCN01_SPACESAT1_1651200_special_burn01_Unclassified.txt
- MEME_799500234_Sat1_1651200_special_separation_unclassified.txt
Monitor Space Hazards expects the filename to contain the NORAD ID and when it’s not found either in filename or in the Monitor Space Hazards database, the file cannot be uploaded.
Monitor Space Hazards also checks the contents of the .oem file which has to be in line with the .oem file specification. Fields that are validated against the specification are:
- NORAD ID must be provided in filename (as above explained)
- NORAD ID must match the current page satellite NORAD ID
- Satellite with provided NORAD ID must be in Monitor Space Hazards database
- META_START/META_STOP tags must be in ephemeris file in header section in proper order (START before STOP)
Following fields must be present in ephemeris file:
- ORIGINATOR
- OBJECT_NAME
- OBJECT_ID
- REF_FRAME
- TIME_SYSTEM
- START_TIME
- STOP_TIME
- CENTER_NAME
- CCSDS_OEM_VERS
- CREATION_DATE
Ephemeris files can be uploaded directly in Monitor Space Hazards application in the Satellites section or via API using POST /ephemeris endpoint (when object_id and .oem file must be provided).