Source: https://guthlabs.ai/docs/instruments/transit-duration-impact-parameter/implementation/

instrument implementation / implementation-contract

# Transit Duration & Impact Parameter implementation

A source-bound implementation contract for Transit Duration & Impact Parameter; 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**: t6-008

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification has no explicit input validation for semi-major axis zero or for the non-transiting regime |b|>1. These inputs produce division-by-zero or non-real square-root results unless the instrument rejects them or selects a no-transit branch.

## 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": {
    "period": 72,
    "period_unit": "hours",
    "semi_major_axis": 10,
    "semi_major_axis_unit": "Rs",
    "star_radius": 1,
    "star_radius_unit": "Rs",
    "impact_parameter": 0
  },
  "expected_outputs": {
    "arcsin_argument": 0.1,
    "transit_duration_hours": 2.29566819
  },
  "working": "Rs/a=1/10=0.1. sqrt(1-b^2)=sqrt(1-0^2)=1. Argument=0.1×1=0.1. arcsin(0.1)=0.1001674212 rad. P/π=72/π=22.91831181 h. T=22.91831181×0.1001674212=2.29566819 h."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/transit-duration-impact-parameter/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/transit-duration-impact-parameter/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/transit-duration-impact-parameter/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-tranche6/tranche6-results.json`