Navigation and star identification for an interstellar mission

The possibility of interstellar scientific missions, even if only to explore the local Interstellar Medium (ISM), has received increased consideration in recent years. Due to the immense distances involved, an interstellar spacecraft must be capable of autonomous navigation. Many autonomous navigation strategies exist, but nearly all of these depend in some way on star observations and an ability to match these observations to a catalog of known stars. This is generally accomplished by computing and matching a star pattern descriptor that is invariant to changes in the spacecraft attitude. Unlike missions within the Solar System, an interstellar spacecraft will require a catalog that treats stars as 3D points rather than directions. This is problematic, since it has long been known that view invariants do not exist for sets of 3D points—making the classical method (or any modifications thereof) completely ineffectual for star identification in interstellar space. Moreover, other effects for a spacecraft traveling at relativistic speeds – such as stellar aberration and the relativistic Doppler effect – can negatively affect star identification, navigation observability, and sensor design. These challenges of star identification during interstellar flight are discussed and some possible solutions are suggested. Numerical examples are provided for a variety of motivating mission concepts.