Ground Track / Orbital Period vs Altitude

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Earth & Space (astronomy, orbital mechanics, meteorology, geology, geodesy, oceanography)

Tranche

tranche-4

Evidence ID

t4-256

Ledger rows

1

No ledger note is attached.

Review findings

NEEDS_REVIEW because the exact ambiguity is: the specification claims a rough ground-track repeat but supplies no ground-track-repeat formula, required orbital inputs, or defined repeat output. The period and orbits-per-day formulas are standard only under the stated circular-orbit and unit assumptions.

Formula and scope findings

• The implied circular-orbit formula should be stated explicitly as T = 2π√(a³/μ), with a = Rₑ + h; 'T from Kepler' is underspecified.
• Altitude and orbital period do not determine a ground-track repeat. A repeat calculation also requires at least orbital inclination, Earth's rotation rate, and a specified resonance/repeat criterion; with perturbations, nodal regression and other orbital elements are additionally relevant.
• The stated outputs list period and orbits per day, but the instrument description also claims a rough ground-track repeat without providing a formula or output definition.
• The formula assumes a circular orbit. An altitude alone is insufficient for an eccentric orbit, whose period depends on semimajor axis rather than instantaneous altitude.

Unit assumptions

• Use Earth gravitational parameter μ = 398600.4418 km³/s².
• Use mean/equatorial Earth radius Rₑ = 6378.137 km; altitude must be measured from the same reference radius.
• Use altitude in kilometers in the orbital formula, or explicitly convert meters to kilometers first.
• Compute period T in seconds and orbits per day as 86400/T.
• For the period-input mode, the supplied period is assumed to be in seconds and positive.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

A zero supplied period makes the orbits-per-day calculation undefined, and an unspecified altitude unit permits materially different outputs for the same numeric input.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "altitude_km": 0,
    "mu_km3_s2": 398600.4418,
    "earth_radius_km": 6378.137
  },
  "expected_outputs": {
    "period_s": 5069.34,
    "orbits_per_day": 17.0436
  },
  "working": "a = Rₑ + h = 6378.137 + 0 = 6378.137 km. T = 2π√(a³/μ) = 2π√(6378.137³ / 398600.4418) ≈ 5069.34 s. Orbits/day = 86400 / 5069.34 ≈ 17.0436."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json