The Catalog

I have compiled a catalog of over 1000 artificial objects in `deep space'. Version 1.0 of this catalog has been released online at https://planet4589.org/space/deepcat.

By deep space, I mean broadly space beyond the region where the US satellite catalog provides coverage. Note that the term has been used with a variety of definitions. In the context of the SGP4 orbit model [3], deep space' refers to orbital periods above 225 minutes, corresponding to altitudes of about 5900 km, a region normally thought of asmedium Earth orbit' these days. For our purposes a boundary somewhere beyond 50,000 km seems needed. It also appears desirable to exclude communications satellites on supersynchronous transfer orbits which have apogees typically in the 60,000 to 100,000 km range.

For definiteness I adopt a boundary I call [14] EL1:4, the Earth-lunar 1 to 4 orbit resonance in which a satellite in a circular orbit will complete four revolutions of the Earth for every one that the Moon does. EL1:4 is at 152066 km from Earth's center. The choice is motivated by the idea that satellites well within this distance can to first order ignore the Moon and be regarded as being in simple Keplerian orbits on short timescales (clearly, even much closer in at GEO, lunisolar perturbations are important on longer timescales). Satellites at this distance or beyond are more strongly affected by lunar perturbations and should be considered as part of a three-body system. This distinction is obviously not a sharp one and is somewhat arbitrary but it seems as good as any. It also echoes the Sun-Jupiter 1 to 4 resonance which approximately marks the inner edge of the asteroid belt and which serves as a good candidate for a boundary between the inner and outer solar system.