# 📐 L2 Spec — Satellite Gravity Recovery — GRACE/GRACE-FO mass change Mismatch-Only Spec
**ID:** `L2-285-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-285`](/artifact/l1/L1-285)
> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.48 · **Delta tier:** 5
> **⛓ On-chain block:** 41554068
---
## 1. Domain Ω
**Type:** `range`
| Parameter | Unit | Range |
|---|---|---|
| Snr db | dB | 0 – 40 |
| N months | — | 24 – 400 |
| N harmonics | — | 10 – 300 |
| Orbit error | — | 0.0 – 0.1 |
| Leakage error | — | 0.0 – 0.3 |
| Striping error | — | 0.0 – 0.3 |
| Glacial isostatic bias | — | 0.0 – 0.3 |
## 2. Tolerance (ε)
**Type:** `fn`
```
1.5 + 10.0*orbit_error + 5.0*striping_error + 5.0*leakage_error + 5.0*glacial_isostatic_bias
```
## 3. Difficulty
| Property | Value |
|---|---|
| Difficulty score | 0.48 |
| Delta tier | 5 |
## 4. Fingerprint
`269bde75892ae7ca2cbdb4a479634ef9e7d5e48a9bac79426f52a97a0f45a5ce`
## 5. On-chain Registration
- **Chain hash:** `0xf2df9fbd807b90d0808f41358193672d1152e1b9d741fe0db562146e7df2e1ac`
- **Chain tx hash:** `0x84c833831445ecd229ebf9e0b198a159f4f1783f22bbbb41b40cde318cf87c92`
- **Chain block:** `41554068`
---
## File Mapping
This bundle consists of: `L2-285-001.md`, `L2-285-001.json`.
| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-285-001.md` | Source of truth — edit this | Human or LLM |
| `L2-285-001.json` | Structured metadata for the registry | LLM regenerates from the sections above |
**Prompt for your LLM after editing this Markdown:**
> Read the attached Markdown. Regenerate the sibling `.json` so every field matches.
> Preserve the schema documented in the rows above.
> Output each file in its own fenced code block tagged with the filename.
> Output only the JSON object.
_This Markdown was auto-synthesized from the catalog row for `L2-285-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._