Scenario kind pagesEdit on GitHubSource: docs/kinds/by-kind/gnss-ssv.md

gnss-ssv (scenario kind)

Scenario kind of the engine v0.38.0, family Space-user navigation. 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 GNSS availability and link strength in the Space Service Volume and beyond: for a user on a sphere (the ICG booklet's global shell) or on a Keplerian trajectory (LEO to lunar transfer) it counts, per constellation (GPS, GLONASS, Galileo, BDS, QZSS, NavIC) and for all together, the signals usable above a C/N0 threshold - availability of at least one and of four signals, maximum outage duration, received C/N0, dilution of precision, main-lobe against sidelobe links - with a booklet, parametric or user-supplied transmit pattern, optional limb-ray ionosphere, plasmasphere and atmosphere effects and an optional weak-signal receiver design; also an onboard GNSS extended Kalman filter for HEO and lunar-transfer craft (orbital dynamics, solar radiation pressure, third bodies, clock) and relative navigation of a multi-craft formation by single-differenced pseudoranges. Checked against the ICG SSV booklet tables under a pre-registration (xval/gnss-ssv)

One run of scenarios/gnss-ssv-heo.toml summarises as: gnss-ssv trajectory 497 to 58622 km altitude: l1 combined 1+ 100.0% 4+ 97.4% (max outage 0 min); l5 combined 1+ 100.0% 4+ 100.0% (max outage 0 min)

Inputs#

From the schema (kshana kinds --json):

  • Required fields: shell|trajectory|navigation
  • Optional fields: name, constellations, transmit, receiver, atmosphere, formation

The example scenarios/gnss-ssv-heo.toml sets, among others:

Field Value Unit
constellations.bands [l1, l5] not stated
constellations.include [gps, glonass, galileo, bds] not stated
kind gnss-ssv text
name HEO, high-gain nadir and patch zenith antennas, parametric s text
receiver.cn0_min_dbhz 20 dB-Hz
trajectory.antennas [booklet-high-gain-nadir, booklet-patch-zenith] not stated
trajectory.duration_periods 1 not stated
trajectory.preset heo text
trajectory.series_every_min 60 min
trajectory.step_min 10 min
transmit.pattern parametric text

Run it#

kshana scenarios/gnss-ssv-heo.toml

5 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 Value Unit
atmosphere_model.gamma0_db_per_km 0.0072 dB/km
atmosphere_model.gamma_scale_km 5.3 km
atmosphere_model.h_scale_km 60 km
atmosphere_model.hmf2_km 300 km
atmosphere_model.n0 315 N-units
atmosphere_model.n_scale_km 7.35 km
atmosphere_model.nmf2 1.0000e12 1/m^3
atmosphere_model.plasmapause_l 4.5 1
atmosphere_model.plasmasphere_scale 1 1
atmosphere_model.trough_density 5000000 1/m^3

Result label (the engine's): MODELLED: a geometric and link-budget sweep. The booklet pattern is a constant-power main lobe, the parametric pattern a representative stand-in, and the limb-ray medium a simple stated model; nothing here is a measurement of a signal in space. The availability and outage figures follow the method o

The chart the engine writes for scenarios/gnss-ssv-heo.toml, kind gnss-ssv

Evidence#

MODELLED: the verification matrix rows that name this kind.

  • MODELLED The gnss-ssv kind's availability sweeps: per constellation (GPS, GLONASS, Galileo, BDS, QZSS, NavIC) and combined, the share of (user, epoch) pairs with at least one and at least four signals and the longest outage, for a user on a sphere
  • MODELLED The gnss-ssv kind's [navigation] mode: a nine-state extended Kalman filter (position, velocity, receiver clock bias and drift, a solar-radiation-pressure scale) on pseudoranges whose availability, noise and C/N0 come from the same link
  • MODELLED The gnss-ssv kind's [formation] mode: a chief and deputies each run the absolute filter; the deputy's position relative to the chief is estimated by subtracting the absolute estimates and by a relative filter on single-differenced pseud

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 gnss-ssv kind's availability sweeps: per constellation (GPS, GLONASS, Galileo, BDS, QZSS, NavIC) and combined, the share of (user, epoch) pairs with at le. Oracle (ExternalDataset): The ICG Space Service Volume booklet (UN OOSA ST/SPACE/75, 2018), itself a simulation, compared under a pre-registration committed before the run (xval/gnss-ssv/PREREGISTRATION.md; results in xval/gnss-ssv/RESULTS.md, pinned by tests/ssv_booklet_results.rs, misses included). Run 1 on the pre-registered reading: the minimum-radiated-power constants and the lunar bar agree (S0, S6 met); the upper and lower SSV, RF-thre
  • MODELLED A Chapman ionosphere, a Gallagher-type plasmasphere and a neutral atmosphere (refractivity bending, oxygen absorption, defocusing) integrated along the straight. Oracle (InternalConsistency): Closed forms and published magnitudes in the tests (a Chapman layer's peak and the bending of the surface limb, a few TECU of plasmasphere on a GPS-to-GEO ray); the receiver design reuses the acquisition and tracking-loop models and their tests. No measured limb-sounding or weak-signal reception data is compared with it
  • MODELLED The gnss-ssv kind's [navigation] mode: a nine-state extended Kalman filter (position, velocity, receiver clock bias and drift, a solar-radiation-pressure sc. Oracle (InternalConsistency): Simulated truth against the filter's own estimate (a consistent filter's mean normalised estimation error squared is about 3 for the position) and determinism for a fixed seed. No flight or recorded high-orbit GNSS data is compared; the Sun and Moon are low-precision circular stand-ins
  • MODELLED The gnss-ssv kind's [formation] mode: a chief and deputies each run the absolute filter; the deputy's position relative to the chief is estimated by subtrac. Oracle (InternalConsistency): The same simulated truth as the absolute filter: the relative filter's error against the true relative state, and the check that it does at least as well as subtracting two independent absolute fixes. No flight formation data is compared

Limitations#

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

  • MODELLED: a geometric and link-budget sweep. The booklet pattern is a constant-power main lobe, the parametric pattern a representative stand-in, and the limb-ray medium a simple stated model; nothing here is a measurement of a signal in space. The availability and outage figures follow the method of the ICG Space Service Volume booklet (UN ST/SPACE/75) and are checked against its tables in xval/gnss-ssv/. (result label)
  • MODELLED GNSS availability and link strength in the Space Service Volume and beyond: for a user on a sphere (the ICG booklet's global shell) or on a Keplerian trajectory (LEO to lunar transfer) it counts, per constellation (GPS, GLONASS, Galileo, BDS, QZSS, NavIC) and for all together, the signals usable above a C/N0 threshold - availability of at least one and of four signals, maximum outage duration, received C/N0, (kind catalogue (kshana kinds --json))
  • MODELLED: the pattern is representative, not measured; the medium is a stated simple model (docs/SSV.md). (scenario file comment, line 14)
  • 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))
  • GNSS signal availability in the Space Service Volume and beyond, compared with the ICG SSV booklet 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))
  • Limb-ray ionosphere, plasmasphere and atmosphere effects on grazing GNSS signals, and the weak-signal receiver design, in the gnss-ssv kind 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))
  • Onboard GNSS navigation filter for high-orbit and lunar-transfer spacecraft 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))
  • Relative navigation of a multi-spacecraft formation in a highly elliptical orbit from GNSS 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#