Parse and manipulate Orbit Ephemeris Messages (OEM) and Orbit Parameter Messages (OPM) in KVN format. Supports multi-segment files, optional acceleration data, and Lagrange polynomial interpolation for position queries at arbitrary times.

Installation#

Install with opam:

$ opam install odm

If opam cannot find the package, it may not yet be released in the public opam-repository. Add the overlay repository, then install it:

$ opam repo add samoht https://tangled.org/gazagnaire.org/opam-overlay.git
$ opam update
$ opam install odm

Usage#

let report path =
  match Odm.of_kvn_file path with
  | Ok oem ->
      List.iter
        (fun seg ->
          let start, stop = Odm.epoch_range seg in
          Fmt.pr "Segment: %s to %s (%d points)@." start stop
            (Array.length (Odm.state_vectors seg)))
        (Odm.segments oem)
  | Error e -> Fmt.epr "%a@." Odm.pp_error e

(* Interpolate position at a given time. *)
let position_at ~segment ~unix_timestamp =
  Odm.interpolate segment unix_timestamp

API Overview#

type t -- Complete OEM file: header + segment list
type segment -- Metadata, state vectors, and comments
type state_vector -- Epoch, position (km), velocity (km/s), optional acceleration
type metadata -- Object name/ID, reference frame, time system, interpolation info
of_kvn_string, of_kvn_channel, of_kvn_file -- Parse KVN format
segments, state_vectors, epoch_range -- Accessors
interpolate -- Lagrange polynomial interpolation within a segment
position_at -- Search all segments and interpolate at a given time

Testing#

Upstream vectors: bradsease/oem test suite (valid + invalid OEM samples)
GMAT interop: 24 tests against NASA GMAT R2026a high-fidelity propagation traces (LEO, GEO, Molniya). Validates parser robustness on real-world scientific notation (1e-16 exponents), 5 orders of magnitude range, trailing whitespace, and orbital mechanics constraints (energy conservation, vis-viva). See test/interop/gmat/.

License#

ISC

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