Reading and Writing Files

Besides working with XML strings directly (see Parsing Messages), this package can read messages from files on disk and serialize them back to the XML format defined by CCSDS 502.0-B-3.

Reading From a File

Assume the variable sample_file holds the path to an XML file containing a CCSDS-compliant OMM. We can load it with read_omm:

julia> omm = read_omm(sample_file)OrbitMeanElementsMessage:
  Header
    Comment       : GENERATED VIA SPACE-TRACK.ORG API
    Creation Date : 2025-12-30T23:36:37
    Originator    : 18 SPCS
  Body
  └─ Segment
     ├─ Metadata
     │    Object Name         : AMAZONIA 1
     │    Object ID           : 2021-015A
     │    Center Name         : EARTH
     │    Ref. Frame          : TEME
     │    Time System         : UTC
     │    Mean Element Theory : SGP4
     └─ Data
        └─ Mean Keplerian Elements
             Epoch              : 2025-12-30T18:12:04.533984
             Mean Motion        : 14.40772474 rev/day
             Eccentricity       : 0.0001124
             Inclination        : 98.3721°
             RA of Asc. Node    : 75.0877°
             Arg. of Pericenter : 97.3772°
             Mean Anomaly       : 262.7545°

To read a generic Orbit Data Message — which may be a single message or a Navigation Data Message (NDM) bundling several messages — use read_odm:

julia> odm = read_odm(sample_file)1-element Vector{OrbitDataMessage}:
 OMM: AMAZONIA 1 [2021-015A] (Epoch = 2025-12-30T18:12:04.533984)

Both functions simply read the file contents and forward them to the corresponding parsing function, so the return values follow the same rules described in Parsing Messages.

Writing to a File

Given an OrbitMeanElementsMessage object, we can serialize it to XML using write_omm. The function receives an IO stream, which makes it easy to write to a file or inspect the output in memory:

julia> io = IOBuffer();
julia> write_omm(io, omm)
julia> print(String(take!(io)))<?xml version="1.0" encoding="UTF-8"?>
<omm id="CCSDS_OMM_VERS" version="3.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://sanaregistry.org/files/ndmxml_unqualified/ndmxml-4.0.0-master-4.0.xsd">
  <header>
    <COMMENT>GENERATED VIA SPACE-TRACK.ORG API</COMMENT>
    <CREATION_DATE>2025-12-30T23:36:37.000000000</CREATION_DATE>
    <ORIGINATOR>18 SPCS</ORIGINATOR>
  </header>
  <body>
    <segment>
      <metadata>
        <OBJECT_NAME>AMAZONIA 1</OBJECT_NAME>
        <OBJECT_ID>2021-015A</OBJECT_ID>
        <CENTER_NAME>EARTH</CENTER_NAME>
        <REF_FRAME>TEME</REF_FRAME>
        <TIME_SYSTEM>UTC</TIME_SYSTEM>
        <MEAN_ELEMENT_THEORY>SGP4</MEAN_ELEMENT_THEORY>
      </metadata>
      <data>
        <meanElements>
          <EPOCH>2025-12-30T18:12:04.533984000</EPOCH>
          <MEAN_MOTION>14.40772474</MEAN_MOTION>
          <ECCENTRICITY>0.0001124</ECCENTRICITY>
          <INCLINATION>98.3721</INCLINATION>
          <RA_OF_ASC_NODE>75.0877</RA_OF_ASC_NODE>
          <ARG_OF_PERICENTER>97.3772</ARG_OF_PERICENTER>
          <MEAN_ANOMALY>262.7545</MEAN_ANOMALY>
        </meanElements>
      </data>
    </segment>
  </body>
</omm>

To write directly to a file, open the file in write mode and pass the stream:

open("amazonia_1.xml", "w") do io
    write_omm(io, omm)
end

Writing Several Messages as an NDM

The write_odm function can serialize either a single message or a vector of messages. When a vector is provided, all messages are wrapped inside a single Navigation Data Message (<ndm>) root element:

omms = [omm1, omm2, omm3]

open("catalog.xml", "w") do io
    write_odm(io, omms)
end

This is convenient, for example, to persist the full set of messages returned by one of the online fetchers.

Note

OMM elements are always written with version 3.0, regardless of the version stored in the parsed message, and target the NDM/XML schema. NanoDate values are written with nine fractional digits, preserving nanosecond precision. Optional sections (spacecraft parameters, TLE-related parameters, and user-defined parameters) are only written when the corresponding fields are present in the message.