Orbit Data Messages (CCSDS 502.0-B-3)
Remove ocaml-chunk (not a standard protocol)
Application-layer chunking is custom, not CCSDS/RFC.
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test/interop/gmat/test.ml
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test/interop/gmat/test.ml
···
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(** GMAT interop tests for ocaml-odm.
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Parses CCSDS OEM files generated by NASA GMAT R2026a and validates
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structural properties and physical constraints.
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structural properties, physical constraints, and parser robustness.
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GMAT output exercises real edge cases:
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- Scientific notation exponents down to 1e-16 (near-zero velocity
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components)
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- 5 orders of magnitude range in one file (Molniya perigee vs apogee)
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- Trailing whitespace on metadata values (INTERPOLATION_DEGREE = 7 )
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- Space inside ORIGINATOR value (GMAT USER)
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- Variable-width columns (sign character shifts alignment)
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Source: GMAT R2026a, scripts in scripts/. Traces in traces/. *)
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···
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Alcotest.(check string)
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"start" "2026-01-01T00:00:00.000" seg.metadata.start_time
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(* GMAT outputs "ORIGINATOR = GMAT USER" — space inside the value.
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Parser must not split on internal whitespace. *)
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let test_leo_originator_with_space () =
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let oem = parse_oem "leo_7day.oem" in
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Alcotest.(check string) "originator" "GMAT USER" oem.header.originator
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(* GMAT outputs "INTERPOLATION_DEGREE = 7 " with trailing space.
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Parser must trim before int_of_string. *)
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let test_leo_interpolation_degree () =
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let oem = parse_oem "leo_7day.oem" in
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let seg = List.hd (Odm.segments oem) in
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Alcotest.(check (option int))
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"interpolation degree" (Some 7) seg.metadata.interpolation_degree
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let test_leo_radius_bounds () =
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let oem = parse_oem "leo_7day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
···
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Alcotest.(check string) "start epoch" "2026-01-01T00:00:00.000" start;
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Alcotest.(check string) "stop epoch" "2026-01-08T00:00:00.000" stop
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(* First data line has Vz = 3.68e-16 km/s (machine epsilon).
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Verify no NaN or underflow to exactly 0.0 — the parsed value should be
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non-zero and finite. *)
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let test_leo_near_zero_velocity_component () =
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let oem = parse_oem "leo_7day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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let vz = svs.(0).Odm.vel.z in
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Alcotest.(check bool) "Vz finite" true (Float.is_finite vz);
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Alcotest.(check bool) "Vz not exactly zero" true (Float.abs vz > 0.0);
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Alcotest.(check bool) "Vz ~3.68e-16" true (Float.abs vz < 1e-14)
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(* All state vectors must have finite (non-NaN, non-inf) components.
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GMAT uses 16-digit scientific notation — parser must handle full precision. *)
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let test_leo_no_nan_or_inf () =
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let oem = parse_oem "leo_7day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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Array.iteri
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(fun i sv ->
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let check name v =
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if not (Float.is_finite v) then
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Alcotest.failf "non-finite %s at vector %d (%s): %g" name i
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sv.Odm.epoch v
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in
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check "X" sv.pos.x;
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check "Y" sv.pos.y;
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check "Z" sv.pos.z;
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check "VX" sv.vel.x;
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check "VY" sv.vel.y;
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check "VZ" sv.vel.z)
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svs
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(* Epochs must be monotonically increasing. *)
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let test_leo_epoch_monotonic () =
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let oem = parse_oem "leo_7day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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for i = 1 to Array.length svs - 1 do
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if String.compare svs.(i).Odm.epoch svs.(i - 1).epoch <= 0 then
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Alcotest.failf "non-monotonic epoch at %d: %s <= %s" i svs.(i).epoch
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svs.(i - 1).epoch
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done
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(* Energy conservation: specific orbital energy should be roughly constant
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across the 7-day propagation (within drag/perturbation effects). *)
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let test_leo_energy_conservation () =
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let oem = parse_oem "leo_7day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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let mu = 398600.4418 in
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let energy sv =
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let r = vec3_norm sv.Odm.pos in
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let v = vec3_norm sv.vel in
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(0.5 *. v *. v) -. (mu /. r)
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in
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let e0 = energy svs.(0) in
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(* LEO with drag: energy decays. Allow ~1% change over 7 days. *)
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Array.iter
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(fun sv ->
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let e = energy sv in
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let rel = Float.abs (e -. e0) /. Float.abs e0 in
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if rel > 0.01 then
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Alcotest.failf "energy drift > 1%%: %.6e vs %.6e (%.2f%%) at %s" e e0
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(rel *. 100.0) sv.epoch)
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svs
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(* Interpolation: value at a known epoch should match the data point. *)
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let test_leo_interpolation_at_epoch () =
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let oem = parse_oem "leo_7day.oem" in
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let seg = List.hd (Odm.segments oem) in
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let svs = Odm.state_vectors seg in
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(* Pick a data point in the middle and interpolate at its exact epoch *)
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let mid = svs.(5000) in
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match Odm.interpolate seg with
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| exception _ -> Alcotest.fail "interpolate raised exception"
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| _interp ->
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(* Just verify interpolation function exists and doesn't crash on this OEM *)
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()
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(* --- GEO 3-day ---
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Source: GMAT R2026a, geo_3day.script.
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GEO orbit: SMA=42164 km, ECC=0.0001, INC=0.05 deg. *)
···
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let test_geo_parse () =
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let oem = parse_oem "geo_3day.oem" in
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let sv = Odm.state_vectors (List.hd (Odm.segments oem)) in
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(* 3 days at 300s step = 864 + 1 vectors *)
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Alcotest.(check bool) "~864 vectors" true (Array.length sv > 800)
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let test_geo_radius () =
···
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Alcotest.failf "GEO velocity out of bounds: %.3f km/s at %s" v sv.epoch)
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svs
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(* GEO: near-circular orbit. Eccentricity < 0.001 means radius variation
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should be tiny (< 50 km peak-to-peak). *)
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let test_geo_near_circular () =
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let oem = parse_oem "geo_3day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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let min_r = ref Float.infinity in
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let max_r = ref Float.neg_infinity in
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Array.iter
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(fun sv ->
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let r = vec3_norm sv.Odm.pos in
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min_r := Float.min !min_r r;
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max_r := Float.max !max_r r)
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svs;
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let variation = !max_r -. !min_r in
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Alcotest.(check bool) "radius variation < 50 km" true (variation < 50.0);
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Printf.printf " GEO radius variation: %.3f km\n" variation
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let test_geo_no_nan_or_inf () =
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let oem = parse_oem "geo_3day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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Array.iteri
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(fun i sv ->
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let check name v =
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if not (Float.is_finite v) then
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Alcotest.failf "non-finite %s at vector %d: %g" name i v
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in
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check "X" sv.Odm.pos.x;
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check "Y" sv.pos.y;
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check "Z" sv.pos.z;
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check "VX" sv.vel.x;
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check "VY" sv.vel.y;
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check "VZ" sv.vel.z)
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svs
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(* --- Molniya 2-day ---
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Source: GMAT R2026a, molniya_2day.script.
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Molniya orbit: SMA=26600 km, ECC=0.74, INC=63.4 deg. *)
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Molniya orbit: SMA=26600 km, ECC=0.74, INC=63.4 deg.
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This is the hardest orbit to parse correctly: 5 orders of magnitude
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in position values, near-zero Y components (1e-12 km), velocities
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from 1.5 to 10 km/s. *)
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let test_molniya_parse () =
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let oem = parse_oem "molniya_2day.oem" in
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let sv = Odm.state_vectors (List.hd (Odm.segments oem)) in
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(* 2 days at 30s step = 5760 + 1 vectors *)
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Alcotest.(check bool) "~5760 vectors" true (Array.length sv > 5700)
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let test_molniya_radius_range () =
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let oem = parse_oem "molniya_2day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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(* Molniya: perigee ~6916 km (SMA*(1-e)), apogee ~46244 km (SMA*(1+e)) *)
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let min_r = ref Float.infinity in
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let max_r = ref Float.neg_infinity in
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Array.iter
···
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(!min_r > 6500.0 && !min_r < 7500.0);
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Alcotest.(check bool)
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"apogee ~46000 km" true
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(!max_r > 44000.0 && !max_r < 48000.0)
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(!max_r > 44000.0 && !max_r < 48000.0);
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Printf.printf " Molniya: perigee %.1f km, apogee %.1f km\n" !min_r !max_r
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let test_molniya_velocity_range () =
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let oem = parse_oem "molniya_2day.oem" in
···
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"max velocity ~10 km/s" true
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(!max_v > 8.0 && !max_v < 12.0)
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(* Molniya Y-position at epoch is ~1e-12 km (numerical noise from integrator).
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Parser must handle exponents down to e-15 without underflow to zero. *)
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let test_molniya_near_zero_components () =
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let oem = parse_oem "molniya_2day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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let y0 = svs.(0).Odm.pos.y in
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Alcotest.(check bool) "Y0 finite" true (Float.is_finite y0);
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(* The value should be very small but not exactly zero *)
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Alcotest.(check bool) "Y0 ~1e-12" true (Float.abs y0 < 1e-10)
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(* All 5760+ vectors must be finite — no NaN from parsing 1e-15 exponents. *)
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let test_molniya_no_nan_or_inf () =
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let oem = parse_oem "molniya_2day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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Array.iteri
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(fun i sv ->
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let check name v =
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if not (Float.is_finite v) then
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Alcotest.failf "non-finite %s at vector %d (%s): %g" name i
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sv.Odm.epoch v
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in
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check "X" sv.pos.x;
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check "Y" sv.pos.y;
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check "Z" sv.pos.z;
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check "VX" sv.vel.x;
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check "VY" sv.vel.y;
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check "VZ" sv.vel.z)
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svs
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(* Vis-viva: v^2 = mu * (2/r - 1/a). For Molniya, SMA=26600 km.
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At each point, check vis-viva holds within perturbation error. *)
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let test_molniya_vis_viva () =
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let oem = parse_oem "molniya_2day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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let mu = 398600.4418 in
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(* Compute SMA from first state via vis-viva *)
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let r0 = vec3_norm svs.(0).Odm.pos in
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let v0 = vec3_norm svs.(0).vel in
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let a0 = 1.0 /. ((2.0 /. r0) -. (v0 *. v0 /. mu)) in
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(* SMA should be ~26600 km *)
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Alcotest.(check bool) "SMA ~26600 km" true (a0 > 26000.0 && a0 < 27200.0);
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Printf.printf " Molniya SMA from vis-viva: %.1f km (expected ~26600)\n" a0;
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(* Check vis-viva consistency across all points (allow ~0.5% for J2 effects) *)
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Array.iter
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(fun sv ->
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let r = vec3_norm sv.Odm.pos in
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let v = vec3_norm sv.vel in
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let a = 1.0 /. ((2.0 /. r) -. (v *. v /. mu)) in
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let rel = Float.abs (a -. a0) /. Float.abs a0 in
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if rel > 0.005 then
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Alcotest.failf "vis-viva SMA drift > 0.5%%: %.1f vs %.1f (%.3f%%) at %s"
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a a0 (rel *. 100.0) sv.epoch)
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svs
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(* Epoch monotonicity for Molniya (30s step — more data points to check). *)
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let test_molniya_epoch_monotonic () =
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let oem = parse_oem "molniya_2day.oem" in
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let svs = Odm.state_vectors (List.hd (Odm.segments oem)) in
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for i = 1 to Array.length svs - 1 do
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if String.compare svs.(i).Odm.epoch svs.(i - 1).epoch <= 0 then
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Alcotest.failf "non-monotonic epoch at %d: %s <= %s" i svs.(i).epoch
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svs.(i - 1).epoch
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done
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let () =
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Alcotest.run "odm-gmat"
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[
···
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[
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Alcotest.test_case "parse" `Quick test_leo_parse;
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Alcotest.test_case "metadata" `Quick test_leo_metadata;
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Alcotest.test_case "originator with space" `Quick
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test_leo_originator_with_space;
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Alcotest.test_case "interpolation degree" `Quick
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test_leo_interpolation_degree;
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Alcotest.test_case "radius bounds" `Quick test_leo_radius_bounds;
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Alcotest.test_case "velocity bounds" `Quick test_leo_velocity_bounds;
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Alcotest.test_case "epoch range" `Quick test_leo_epoch_range;
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Alcotest.test_case "near-zero Vz (3.68e-16)" `Quick
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test_leo_near_zero_velocity_component;
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Alcotest.test_case "no NaN or inf" `Quick test_leo_no_nan_or_inf;
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Alcotest.test_case "epoch monotonic" `Quick test_leo_epoch_monotonic;
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Alcotest.test_case "energy conservation" `Quick
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test_leo_energy_conservation;
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Alcotest.test_case "interpolation" `Quick
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test_leo_interpolation_at_epoch;
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] );
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( "geo",
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[
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Alcotest.test_case "parse" `Quick test_geo_parse;
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Alcotest.test_case "radius" `Quick test_geo_radius;
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Alcotest.test_case "velocity" `Quick test_geo_velocity;
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Alcotest.test_case "near-circular" `Quick test_geo_near_circular;
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Alcotest.test_case "no NaN or inf" `Quick test_geo_no_nan_or_inf;
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] );
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( "molniya",
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[
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Alcotest.test_case "parse" `Quick test_molniya_parse;
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Alcotest.test_case "radius range" `Quick test_molniya_radius_range;
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Alcotest.test_case "velocity range" `Quick test_molniya_velocity_range;
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Alcotest.test_case "near-zero Y (1e-12)" `Quick
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test_molniya_near_zero_components;
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Alcotest.test_case "no NaN or inf" `Quick test_molniya_no_nan_or_inf;
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Alcotest.test_case "vis-viva consistency" `Quick test_molniya_vis_viva;
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Alcotest.test_case "epoch monotonic" `Quick
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test_molniya_epoch_monotonic;
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] );
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]