Yasir Latif, Space Protocol; Anirban Chowdhury, Space Protocol; Samya Bagchi, Space Protocol
Keywords: TDM, SSA, AI, Blockchain
Abstract:
Reliably tracking the position of resident space objects (RSOs) is a fundamental Space Situational Awareness (SSA) task. The quality of tracking affects mission critical tasks such as conjunction analysis and launch window optimization. The Tracking Data Message (TDM) is a standardized data exchange format to broadcast and disseminate RSO observations.
Given a network of observers, a single RSO passing through it would generate multiple TDMs over time. However, it may consist of varying qualities of observations made by different sensors on ground and potentially in space.
In the current SSA landscape, TDMs are accepted from trusted parties without question and further verification. This is under the assumption of complete trust on the transmitting party. However, in an adversarial setting where bad actors can spoof TDMs, critical SSA capabilities lie vulnerable to false information and the subsequent generation of false or missed conjunction detection, a potentially catastrophic scenario for space safety and security.
In this work, we propose a trustless mechanism for TDM validation and verification using a blockchain. The blockchain, due to its trustless nature, removes the need for a central trusted authority as the source of truth, instead the source of truth is established via consensus on the chain. The authority of data through validation determines the source of truth, rather than the reputation of the generating observer, since the latter can be spoofed.
Starting from multiple observations of an RSO in the form of TDMs, our first contribution is a state of the art transformer-based orbit propagator that provides better accuracy compared to SGP4. This machine learning based propagation model is the key to cross validating multiple observations for the same RSO, even in the absence of its identity. Cross validation occurs by propagating the data in one TDM to another observed by a different sensor across time and comparing the propagated position to the actual observation. Doing this across multiple TDMs increases the confidence in its validity. However, who should validate this information and who can provide the TDMs in the first place?
Our second contribution implements the accumulation of TDMs on a Proof of Stake (PoS) blockchain. The chain consists of two types of entities: observers and validators. Observers contribute TDM data to the chain by supplying a collateral (a stake) which serves to keep them honest. Validator nodes, run the propagation and validation algorithm previously described, to establish the validity of these messages over a period of time. The adoption of the blockchain is incentivized by rewarding observers and validators using different mechanisms. Observers that contribute the first TDM for a new RSO, get the highest reward once the TDM has been verified, usually within the first 24 hours. Subsequent TDMs for the same RSO receive a smaller reward which diminishes over time to a constant value. To disincentivize false/spoofed TDMs – ones that can not be verified by any other participant in the network within the 24 hours duration – observers are penalized by having their stake slashed.
A blockchain over which TDMs for RSOs can be validated and recorded opens up a new permissionless, reliable and trustless source of truth for downstream SSA tasks such as conjunction analysis. The open nature of blockchain encourages not only existing operators with SSA capabilities to contribute observational data, but also enables amateur observers, such as those participating in SeeSat and SatNOGS, to contribute valuable information to the network, increasing the sources from which RSO data can be acquired, verified and made available for public and operator use.
This complete unalterable record of RSO TDMs on the chain, serves as a basis of computing the Detectability, Trackability and Identifiability scores for each RSO, which can then be used in a similar manner to Space Sustainability Ratings DIT module to characterize and track an RSO’s sustainability rating over time. However. the on-chain SSR is built from data that has been verified by the on-chain consensus.
Date of Conference: September 17-20, 2024
Track: Space Domain Awareness