By combining signals from NASA’s Cassini spacecraft with observations from the National Radio Astronomy Observatory’s (NRAO) very long baseline array (VLBA), scientists have been able to accurately identify Saturn’s position to within a single mile. This information will be useful in understanding the orbits of planets in the outer solar system, and will have other widespread implications for future research. The study was led by Dayton Jones of Jet Propulsion Laboratory, and the paper was published in The Astronomical Journal. The work was also presented this week at the 225th meeting of the American Astronomical Meeting.
"This work is a great step toward tying together our understanding of the orbits of the outer planets of our solar system and those of the inner planets," Jones said in a press release.
The VLBA is a network of ten radio antennae that span across North America, from Hawaii to the Virgin Islands. Working in concert, the array is able to resolve incredible detail across great distances. In this case, it was able to very accurately track the radio signal from the Cassini spacecraft, which has been orbiting Saturn for the last ten years.
Using five years’ worth of Cassini’s signaling data, the VLBA was able to resolve Saturn’s location to an area smaller than two miles, which is roughly 50-100 times more accurate than previous calculations. This greatly clarifies Saturn’s ephemeris, which is the table that states a celestial body’s predicted location at any given point in time.
"An accurate ephemeris is one of the basic tools of astronomy, and this work is a great step toward tying together our understanding of the orbits of the outer planets and those of the inner planets," Jones explained to the NRAO. "The orbits of the inner planets are well tied together, but those of the outer planets, including Saturn, have not been tied as well to each other or to those of the inner planets.”
By better understanding Saturn’s orbit and where it will be at a given time in relation to other objects, astronomers can take advantage of research opportunities. These include using distant light to study its rings, the better timing of experiments with pulsars, and even improving tests regarding Einstein’s theory of general relativity using quasars. The updated ephemeris will also be quite useful for better navigation of spacecrafts, and has already improved the course of Cassini’s mission to make more meaningful measurements and observations.
The researchers hope to replicate the success from this study in the future with Jupiter. The VLBA will track the radio signals from NASA’s Juno spacecraft, which is set to insert into Jupiter’s orbit in July of 2016. As Jupiter and Saturn are the two largest planets in our solar system, having accurate ephemerides for these planets will be a tremendous accomplishment and greatly improve future scientific research and spacecraft missions.
