Orbit Ephemeris Message

The primary interface between the oem package and OEM files is the OrbitEphemerisMessage class. In addition, the package provides objects to represent each component of an OEM ephemeris.

OrbitEphemerisMessage

See also

Module Ephemeris Components

Module OEM Data Types

Python representation of an Orbit Ephemeris Message.

This class provides the primary interface between the OEM module and an OEM file.

oem.OrbitEphemerisMessage.header

Object containing the OEM header section.

Type:HeaderSection

Examples

The OrbitEphemerisMessage class can load directly from a file:

>>> ephemeris = OrbitEphemerisMessage.open(file_path)

An OEM is made up of one or more data segments available through an iterator:

>>> for segment in ephemeris:
...     for state in segment:
...         # Iterate through states
...         pass
...     for covariance in segment.covariances:
...         # Iterate through covariances
...         pass

It is also possible to iterate through the states and covariances in all segments with the .states and .covariances properties.

To determine if a particular epoch is contained in the useable time range of any of the segments in an ephemeris, use in:

>>> epoch in ephemeris
True

The save_as method enables saving of copies of an OEM in both KVN and XML formats.

>>> oem.save_as("new.oem", file_format="xml")

To convert directly between KVN and XML formats, use the convert class method. For example, to convert a KVN OEM to XML:

>>> oem.convert("input.oem", "output.oem", "xml")
oem.OrbitEphemerisMessage.covariances

Return a list of covariances in all segments.

oem.OrbitEphemerisMessage.states

Return a list of states in all segments.

Ephemeris Components

See also

Module OrbitEphemerisMessage

Module OEM Data Types

EphemerisSegment

class oem.components.EphemerisSegment(metadata, state_data, covariance_data=None, version='2.0')

Bases: object

OEM ephemeris segment.

Container for a single OEM ephemeris segment.

covariances

Return list of Covariances in this segment.

has_accel

Evaluate if segment contains acceleration data.

has_covariance

Evaluate if segment contains covariance data.

states

Return list of States in this segment.

useable_start_time

Return epoch of start of useable state data range

useable_stop_time

Return epoch of end of useable state data range

HeaderSection

class oem.components.HeaderSection(fields)

Bases: oem.base.KeyValueSection

OEM header section.

Container for a single OEM header section.

Examples

This class behaves similar to a dict allowing membership checks, iteration over keys, and value set/get.

>>> "CCSDS_OEM_VERS" in header:
True

>>> keys = [key for key in header]

>>> metadata["ORIGINATOR"] = 'ORIG_NAME'

>>> metadata["ORIGINATOR"]
'ORIG_NAME'
version

MetaDataSection

class oem.components.MetaDataSection(metadata, version='2.0')

Bases: oem.base.KeyValueSection

OEM metadata section.

Container for a single OEM metadata section.

Examples

This class behaves similar to a dict allowing membership checks, iteration over keys, and value set/get.

>>> "OBJECT_NAME" in metadata:
True

>>> keys = [key for key in metadata]

>>> metadata["CENTER_NAME"] = 'Mars'

>>> metadata["CENTER_NAME"]
'Mars'
useable_start_time

Return epoch of start of useable state data range

useable_stop_time

Return epoch of end of useable state data range

DataSection

class oem.components.DataSection(states, version='2.0')

Bases: object

OEM data section.

Container for a single OEM ephemeris state data section.

has_accel

Evaluate if section contains acceleration data.

states

Return a list of States in this section.

CovarianceSection

class oem.components.CovarianceSection(covariances, version='2.0')

Bases: object

OEM covariance section.

Container for a single OEM covariance section.

covariances

Return a list of covariances in this section.

OEM Data Types

See also

Module OrbitEphemerisMessage

Module Ephemeris Components

State

class oem.components.State(epoch, position, velocity, acceleration=None, version='2.0')

Bases: object

Basic Cartesian state.

epoch

Epoch date and time.

Type:DateTime
position

3-element array describing the position at epoch.

Type:ndarray
velocity

3-element array describing the velocity at epoch.

Type:ndarray
acceleration

3-element array describing the acceleration at epoch. If unavailable, this attribute is None.

Type:ndarray
has_accel

Covariance

class oem.components.Covariance(epoch, frame, matrix, version='2.0')

Bases: object

Basic 6x6 covariance.

epoch

Epoch date and time.

Type:DateTime
frame

Reference from of this covariance.

Type:str
matrix

6x6 covariance matrix.

Type:ndarray

Indices and tables