Parsing Messages

This package parses Orbit Data Messages provided as XML strings. All parsing functions accept either a raw XML AbstractString or an already-parsed XML.LazyNode object.

Parsing is strict and case-sensitive by default. Pass strict = false to parse_omm, parse_omms, or parse_odm to match XML tags and the required OMM id attribute value case-insensitively. Permissive mode also preserves an empty OMM header creation date as nothing, which accommodates known Celestrak OMM 2.0 output without inventing a timestamp. Such an incomplete message cannot be written as OMM 3.0. Both modes otherwise reject unrecognized tags and malformed or incomplete OMM sections.

Throughout this page, we assume the variable omm_xml holds the XML string of a single OMM, and ndm_xml holds a Navigation Data Message (NDM) that bundles two OMMs (AMAZONIA 1 and SCD 1).

Parsing a Single OMM

Use parse_omm to obtain a single OrbitMeanElementsMessage. If the input is an NDM containing several OMMs, only the first one is returned:

julia> omm = parse_omm(omm_xml)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°

If the input does not contain any OMM, the function returns nothing.

Parsing Multiple OMMs

When a document may contain several messages — as is typically the case with an NDM — use parse_omms to retrieve all OMMs as a vector:

julia> omms = parse_omms(ndm_xml)2-element Vector{OrbitMeanElementsMessage}:
 OMM: AMAZONIA 1 [2021-015A] (Epoch = 2025-12-30T18:12:04.533984)
 OMM: SCD 1 [1993-009B] (Epoch = 2025-12-30T20:30:29.736576)
julia> length(omms)2
julia> omms[2].body.segment.metadata.object_name"SCD 1"

parse_omms always returns a Vector{OrbitMeanElementsMessage}, which is empty when a recognized document contains no supported OMM.

Parsing Generic Orbit Data Messages

The parse_odm function is the most general entry point. It inspects the root tag of the document and dispatches to the appropriate parser:

parse_odm always returns a Vector{OrbitDataMessage}. A stand-alone <omm> produces a single-element vector, while an <ndm> produces a vector containing every supported message.

julia> odm = parse_odm(omm_xml)1-element Vector{OrbitDataMessage}:
 OMM: AMAZONIA 1 [2021-015A] (Epoch = 2025-12-30T18:12:04.533984)
julia> odms = parse_odm(ndm_xml)2-element Vector{OrbitDataMessage}:
 OMM: AMAZONIA 1 [2021-015A] (Epoch = 2025-12-30T18:12:04.533984)
 OMM: SCD 1 [1993-009B] (Epoch = 2025-12-30T20:30:29.736576)

Working With LazyNode Directly

If you already have an XML.LazyNode — for instance, because you are traversing a larger document — you can pass it directly to any of the parsing functions:

using XML

xml = parse(omm_xml, LazyNode)
omm = parse_omm(xml)