Operators of low-Earth-orbit (LEO) non-geostationary satellite networks, also known as mega-constellations, are required by current regulations to share all available satellite spectrum. This paper proposes a consensus mechanism to facilitate spectrum sharing with accountability by multiple operators, a subset of which may even be adversarial. A distributed ledger is used to securely record and track the state of consensus on spectrum usage, including interference incidents and the corresponding responsible parties. A key challenge is that operators generally do not have initial agreement due to noise in their analog measurements. To address this, two categories of spectrum-sharing solutions are studied in detail. The first category employs an exact Byzantine fault tolerant (BFT) agreement model; the second category utilizes an approximate BFT agreement model. Practical considerations were taken into account regarding the BFT agreements, substantiated by numerical findings on the feasibility of the proposed solutions within the context of non-geostationary orbit satellite networks (NGSO).