> ## Documentation Index
> Fetch the complete documentation index at: https://docs.herodotus.cloud/llms.txt
> Use this file to discover all available pages before exploring further.

# How Satellite Powers Herodotus Services

> How Satellite connects Storage Proof API, Data Structure Indexer, and HDP

Satellite is the on-chain anchor that other Herodotus services build on.

## Storage Proof API -> Satellite

[Storage Proof API](/storage-proofs-api/introduction) manages proof workflows and writes verified historical facts into Satellite.

From the app perspective:

1. You request proof-backed data.
2. The pipeline verifies data against block commitments.
3. Verified facts become readable through Satellite contract functions.

This is why on-chain reads can be simple while still cryptographically grounded.

## Data Structure Indexer -> off-chain visibility for Satellite data structures

[Data Structure Indexer API](/data-structure-indexer-api/introduction) is the off-chain companion for accumulator/remapper access.

It provides queryable access to data structures and metadata such as:

* MMR-related roots/peaks/proof data,
* remapper lookup helpers,
* and other proof-oriented indexing primitives.

In practice, this is the off-chain indexing and retrieval layer around the same commitment system that Satellite enforces on-chain.

## HDP -> computation on top of committed history

[HDP](/data-processor/introduction) executes proof-backed computation over historical chain data.

Its verification model relies on header commitments and proof chains rooted in MMR-backed history. In other words, the blocks and proofs HDP consumes are tied to the same Satellite commitment layer.

This linkage is central to HDP soundness:

* historical facts are validated against committed roots,
* those roots are anchored in Satellite MMR state,
* and resulting computations can be authenticated through fact-registry flows.

## Why this matters for trust

Together, these layers separate concerns cleanly:

* index and fetch off-chain efficiently,
* verify and anchor on-chain,
* compute with proof constraints.

That division is what lets Herodotus scale while preserving verifiable correctness across services.