Source: https://guthlabs.ai/docs/instruments/redshift-velocity-distance/implementation/

instrument implementation / implementation-contract

# Redshift ↔ Velocity/Distance implementation

A source-bound implementation contract for Redshift ↔ Velocity/Distance; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-065

**Effect**: Computation or source lookup only

## Input and validation requirements

The distance calculation is undefined when the user selects H0=0, and the specification provides no explicit high-redshift branch or threshold even though v=cz is only a low-z approximation. Wavelength-field reversal also produces a materially different signed result.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "z": 0.01,
    "H0_km_s_Mpc": 67.4,
    "c_km_s": 299792.458
  },
  "expected_outputs": {
    "velocity_km_s": 2997.92458,
    "distance_Mpc": 44.47959317
  },
  "working": "v = cz = 299792.458 km/s × 0.01 = 2997.92458 km/s. d = v/H0 = 2997.92458 km/s ÷ 67.4 km/s/Mpc = 44.47959317 Mpc."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/redshift-velocity-distance/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/redshift-velocity-distance/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/redshift-velocity-distance/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`