OUTER SOLAR SYSTEM NAVIGATION

 

About

To the outer solar system… and beyond!

Mankind’s curiosity and search for extra-terrestrial life is driving the future of space exploration to the Outer Solar System and beyond. Future spacecraft involved in such missions will encounter the Outer Planets more often than those of the past. The Outer Planets consist of Jupiter, Saturn, Uranus, and Neptune. Jupiter has already played a major role in past exploration efforts to the Outer Solar System.

Jupiter’s large mass makes it an ideal object for gravity-assist maneuvers, reducing fuel consumption and mission time. Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, and New Horizons, all of which were successful in visiting the Outer Solar System and leaving the Solar System, used Jupiter flyby maneuvers. Jupiter will continue to serve this strategic role for future missions to the Outer Solar System and beyond.

Traditional navigation during the Jupiter gravity-assist maneuver requires Earth-based communications to establish spacecraft position estimates. These communications involve the Deep Space Network (DSN). The DSN has been employed in nearly every space exploration mission to the Outer Solar System and provides a reliable means of spacecraft guidance and navigation from Earth. 

However, two-way communications are required to establish a spacecraft position estimate using Earth-based methods, such as the DSN. As spacecraft distance increases, so does the time required to obtain a position estimate. For the case of spacecraft in the vicinity of Jupiter, a time of 4000 seconds (~1.1 hours) is elapsed before a position estimate is established. In other words, there is a delay in knowing where the spacecraft is in its trajectory during a Jupiter gravity-assist maneuver. This delay compromises responsiveness and improving this aspect of navigation performance could enable new missions to the Outer Solar System. This opportunity, among other reasons, motivates an onboard means of navigating about Jupiter independent of communications from Earth.

Applications

Onboard Navigation

This work seeks to establish spacecraft position estimates independent of any Earth-based communications. Jupiter’s position relative to Earth has been heavily studied in astronomy and is known to a high degree of accuracy using ephemerides. Thus, only the spacecraft’s position relative to Jupiter is needed to establish a spacecraft position estimate relative to Earth. We seek to exploit Jupiter’s banded atmosphere to obtain spacecraft latitude estimates. Additionally, spacecraft longitude estimates are obtained using radio emissions from Jupiter’s moon Io.

Although our emphasis is on Jupiter, we expect our latitude estimation methods to also be applicable to other planets with a banded atmosphere such as Saturn, Uranus, and Neptune. 

Radio Astronomy

The Jovian decametric radio emissions serve as a source of information when establishing spacecraft longitude estimates relative to Jupiter. These emissions must first be detected and classified by the spacecraft. We employ machine learning and signal processing techniques to obtain information critical to spacecraft longitude estimation. These techniques may prove beneficial and helpful to radio astronomers studying/observing similar phenomena.