lunar-descent (scenario kind)

Scenario kind of the engine v0.40.0, family Lunar and cislunar. Advisory: analysis output from a research and engineering tool, not type-approved navigation equipment and not a safety-of-life service. Every label here is the engine's or the verification matrix's; a kind is MODELLED unless the matrix says otherwise (how a label is earned: the README's Evidence section).

What it does#

MODELLED landing-dispersion budget for a powered descent to a south-polar site (Artemis-class). Per horizontal axis a five-state inertial error model (position, velocity, accelerometer bias, attitude tilt, gyro bias) is driven by the descent's specific force; a sequential filter takes position fixes from the enabled aids: an AFS fix from the visible relays of an ILLUSTRATIVE LCNS-class constellation (standalone, or differential using the correction-link residual of lunar-differential-pnt, with the clock aided when only three relays are visible) and a terrain-relative fix (the crate's TERCOM/SITAN matcher on a synthetic relief, or the Cramer-Rao bound of matching an elevation window of the real LOLA south-polar DEM). Lunar time enters through the vehicle clock at the fixes (the LTC-TT offset of lunar-time-offset, or the uncertainty of its published band) and as a time-tag error along track. Reports the 3-sigma landing ellipse, R95, the closed-form inertial sources, each aid's contribution, the ablation of every aid combination, a Monte Carlo calibration of the ellipse, and the covariance handed on. MODELLED: illustrative IMU class, relay set, descent profile and guidance term; terrain-nav uses a synthetic relief on an Earth metre scale; AFS availability is one epoch on a flat mask. Not agency-endorsed; advisory software, not certified navigation equipment.

One run of scenarios/lunar-descent.toml summarises as: lunar-descent | -89.50 deg | inertial only 517/517 m (E/N) | with aids 7.6/4.8 m | dispersion R95 51 m | 3-sigma ellipse 64 x 62 m | 99.1% inside (expect 98.9%) (MODELLED)

Inputs#

From the schema (kshana kinds --json):

• Required fields: none
• Optional fields: site_lat_deg, site_lon_deg, more_site_lats_deg, descent_s, specific_force_m_s2, horizontal_speed_m_s, accel_bias_ug, align_arcmin, gyro_bias_deg_per_hr, carried_pos_sigma_m, carried_vel_sigma_m_s, guidance_sigma_m, afs_mode, n_relays, mask_deg, afs_cn0_dbhz, sis_ure_m, afs_first_fix_s, afs_interval_s, baseline_km, trn_source, trn_fix_time_s, trn_altimeter_sigma_m, trn_map_sigma_m, dem_descriptor, trn_window_m, trn_height_sigma_m, trn_registration_sigma_m, lunar_time_mode, time_since_sync_days, n_trials, seed

The example scenarios/lunar-descent.toml sets, among others:

Run it#

kshana scenarios/lunar-descent.toml

2 bundled scenarios use this kind; the others are in scenarios/.

What it gives#

The scalar results of that run, with the units the engine states:

Result label (the engine's): MODELLED

Evidence#

MODELLED: the verification matrix rows that name this kind.

• MODELLED The lunar-descent kind and phase: a five-state per-axis inertial error model (position, velocity, accelerometer bias, tilt, gyro bias) over a powered descent, aided by AFS fixes (standalone or differential, with the clock-aided three-rela

The rows the run itself exercised, with the oracle the matrix gives each (the public sources are named there):

• MODELLED Deterministic, scenario-hashed, SBOM + cross-platform golden gates. Oracle (ExternalDataset): SBOM conformance to the official CycloneDX 1.5 JSON Schema (+ valid SPDX identifiers) — an external published standard, zero validation errors over the full dependency graph; the FoM-determinism / byte-reproducibility part remains a pinned self-consistency check, so the row stays MODELLED
• MODELLED The lunar-descent kind and phase: a five-state per-axis inertial error model (position, velocity, accelerometer bias, tilt, gyro bias) over a powered descent,. Oracle (InternalConsistency): The closed-form inertial drift, the reused kinds' own results and the calibration of the 3-sigma ellipse (the fraction inside agrees with its expectation) in the tests. No flown or tested landing is compared

Limitations#

What the run's own report says is not modelled or not validated:

• MODELLED (result label)
• MODELLED landing-dispersion budget for a powered descent to a south-polar site (Artemis-class). (kind catalogue (kshana kinds --json))
• MODELLED: illustrative IMU class, relay set, descent profile and guidance term; terrain-nav uses a synthetic relief on an Earth metre scale; AFS availability is one epoch on a flat mask. (kind catalogue (kshana kinds --json))
• HONESTY: MODELLED. The IMU class, the descent profile, the relay set, the signal-in-space error and the guidance term are ILLUSTRATIVE inputs, not measurements. The terrain-nav mode uses the self-contained synthetic relief and an Earth metre scale, so the terrain term here is the matcher's behaviour on a stand-in, not a statement about south-polar relief: the lola-crlb variant (lunar-descent-lola.toml) uses the real (scenario file comment, lines 14 to 20)
• Reproducibility & software assurance is MODELLED, not validated: a sub-claim is externally checked, but the whole capability composes modelled pieces, so the capability stays Modelled. (verification matrix (docs/MODELLED-RATIONALE.md))
• Landing-dispersion budget at a lunar polar site (lunar-descent) is MODELLED, not validated: checked against its own closed-form / analytic identity — catches transcription and coefficient errors, but is not an external oracle. (verification matrix (docs/MODELLED-RATIONALE.md))

See also#

• Family page: Lunar and cislunar
• All kinds: KINDS.md
• Topic page: MISSION-THREAD-LUNAR.md
• Topic page: MISSION-THREAD.md