Source: https://guthlabs.ai/docs/instruments/absolute-magnitude-of-solar-system-body-h-diameter/mechanism/

instrument mechanism / verified-clean

# Absolute Magnitude of Solar System Body (H) ↔ Diameter mechanism

The inspectable method record for Absolute Magnitude of Solar System Body (H) ↔ Diameter, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The algebra and constant are correct for the standard approximate asteroid relation. Verdict is NEEDS_REVIEW because the unknown-albedo behavior and the exact meaning of albedo/H are underspecified. The honest label appropriately warns that assumed albedo makes the diameter a rough estimate, but it should also state the selected default value or albedo range and the resulting uncertainty.

- The formula D(km)=1329/sqrt(p)*10^(-H/5) is the standard approximate asteroid H–diameter relation when p is the dimensionless geometric albedo and H is the standardized absolute magnitude.

- The specification says a default albedo is assumed when unknown but does not specify the default value or how it is selected by taxonomic type; therefore an unknown-albedo input does not produce a uniquely defined result.

- The input label 'albedo' is ambiguous unless explicitly defined as geometric albedo in the photometric band and convention used by the H value.

## Units and conventions

- H is dimensionless absolute magnitude, conventionally an apparent V-band magnitude normalized to 1 AU from both the Sun and observer and zero phase angle.

- p is dimensionless geometric albedo, with p>0; typical physical values are between 0 and 1.

- The constant 1329 produces diameter in kilometers; conversion to meters requires multiplying the result by 1000.

- The relation is an estimate and assumes the standard asteroid H–albedo–diameter convention.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "H": 0,
    "albedo_p": 1
  },
  "expected_outputs": {
    "diameter_km": 1329
  },
  "working": "sqrt(p)=sqrt(1)=1.  -H/5=-0/5=0.  10^0=1.  D=1329/1*1=1329 km."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specification leaves the default albedo value unspecified, does not explicitly state that albedo must be a fraction in the interval 0 < p <= 1, and provides no rejection behavior for p = 0 or p > 1. It also has no genuine piecewise formula branch; the tested switch is only a physical-validity gate.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/absolute-magnitude-of-solar-system-body-h-diameter/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/absolute-magnitude-of-solar-system-body-h-diameter/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/absolute-magnitude-of-solar-system-body-h-diameter/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-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`