Scenario kind pagesEdit on GitHubSource: docs/kinds/by-kind/link-budget.md

link-budget (scenario kind)

Scenario kind of the engine v0.38.0, family Mission analysis, links and space operations. 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#

One-way link budget over the CCSDS 401 / DSN 810-005 link equation: free-space path loss, C/N₀, Eb/N₀, margin and closure for a transmit EIRP, receive G/T, range, data rate and band (s|x|ka) against a required Eb/N₀. A deterministic engineering calculation from the supplied inputs (not a calibrated terminal datasheet).

One run of scenarios/link-budget.toml summarises as: link-budget: x-band, 2000 km, 1000000 bit/s -> FSPL 177.0 dB, Eb/N0 96.6 dB, margin 92.1 dB (closes)

Inputs#

From the schema (kshana kinds --json):

  • Required fields: none
  • Optional fields: band, eirp_dbw, g_over_t_db, range_km, data_rate_bps, other_losses_db, required_eb_n0_db, tsys_k

The example scenarios/link-budget.toml sets, among others:

Field Value Unit
band x text
data_rate_bps 1000000 bit/s
eirp_dbw 55 dBW
g_over_t_db 53 dB/K
kind link-budget text
other_losses_db 3 dB
range_km 2000 km
required_eb_n0_db 4.5 dB

Run it#

kshana scenarios/link-budget.toml

What it gives#

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

Result Value Unit
band x text
closes true flag
cn0_dbhz 156.624475 dB-Hz
data_rate_bps 1000000 bit/s
eb_n0_db 96.624475 dB
free_space_loss_db 176.974625 dB
link_constants.boltzmann_dbw_per_k_per_hz -228.5991 dBW/K/Hz
link_constants.carrier_frequency_hz 8420000000 Hz
link_constants.eirp_dbw 55 dBW
link_constants.g_over_t_db 53 dB/K

Result label (the engine's): One-way link budget over the CCSDS 401 / DSN 810-005 link equation (EIRP − FSPL − L_other + G/T − k); a deterministic engineering calculation from the supplied inputs, NOT a calibrated terminal datasheet

The chart the engine writes for scenarios/link-budget.toml, kind link-budget

Evidence#

MODELLED 1 · VALIDATED 1: the verification matrix rows that name this kind.

  • VALIDATED Free-space path loss, C/N₀, Eb/N₀, margin and closure over the CCSDS 401 / DSN 810-005 link equation for EIRP/G·T/range/rate/band against a required Eb/N₀. Tests: one_way_link_budget_reference.rs.
  • MODELLED Lunar-native jammer-to-signal ratio, effective C/N₀ and loss of lock for a selenographic surface user under a lunar surface (or raised) jammer, over the illustrative public-source Moonlight/LCNS-class constellation.

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
  • VALIDATED Free-space path loss, C/N₀, Eb/N₀, margin and closure over the CCSDS 401 / DSN 810-005 link equation for EIRP/G·T/range/rate/band against a required Eb/N₀. Runn. Oracle (ExternalDataset): Published deep-space telecom design-control table as pinned numeric vectors: DESCANSO / J. H. Yuen (ed.), Deep Space Telecommunications Systems Engineering, JPL Pub 82-76, Table 1-1 (Galileo X-band) — kshana reassembles the table line-items and reproduces its published end-to-end L_fs 290.54 dB and Pr/N0 54.6 dB-Hz; free-space loss also checked vs ITU-R P.525
  • MODELLED The link-budget report states every absolute constant its own margin was computed from -- the carrier frequency the free-space loss used, the EIRP, the figure o. Oracle (InternalConsistency): No external oracle: this is self-description over an equation already validated against a published design-control table (see the one-way link budget row). It is recorded because the absence of it was a measured defect -- reproducing the released d1_rate_gain_beamwidth.csv required back-solving one effective constant to 0.0034 dB from all thirty rows, and the engine now both names that combination and proves, by test

Limitations#

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

  • Optional: the receive system noise temperature (K). It is NOT an input to the link equation -- that needs only the ratio G/T -- but stating it lets the report also give the receive antenna gain the figure of merit implies (G = G/T + 10*log10(T_sys)). Left out, the gain split is absent from the report rather than assumed. tsys_k = 300.0 (scenario file comment, lines 21 to 25)
  • 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))
  • Link-budget report self-description 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#