Early scientific results from the Cassini/Huygens Earth swingby
24 August 1999This remarkable observation of the Cassini/Huygens spacecraft was made from Australia while it was on its way out towards Jupiter a few hours after it had successfully completed its Earth flyby on 18 August at 3:38 UTC.
The swingby was performed to give the NASA/ESA Cassini/Huygens space probe a 5.5 km/s boost in speed, propelling it towards Saturn, more than 1 billion kilometres away.
The Huygens Probe was dormant during the Earth flyby phase, several of the scientific instruments on the Cassini Orbiter performed 'calibration' measurements while crossing the Earth's magnetosphere at high speed. Optical observations of the moon were also made. The 11-m long magnetometer boom was deployed about two days before the Earth flyby to allow precise calibration of the magnetometer sensors (MAG, Principal Investigator: D. Southwood, Imperial College, London) while still in the well-known Earth's magnetic field. The two magnetometer sensors were switched on during the boom deployment, which allowed unique measurements to be made during this crucial activity. Details on these measurements can be found on the MAG homepage at Imperial College
The Radio and Plasma Wave System (RPWS, Principal Investigator: D. Gurnett, Univ. of Iowa) aboard the Orbiter also made observations. The spacecraft crossed the Earth's bowshock only two hours before closest approach, giving an idea of the speed at which it went through the Earth's magnetospheric cavity. Interesting to note are the Earth radio station signals that were easily detected by RPWS when the spacecraft went above the nightside ionosphere as illustrated in the trajectory plot in the third figure.
The spacecraft remains in excellent health as it continues on the next phase of its seven-year journey to Saturn. On 30 December 2000 its swingby of Jupiter will give it the final boost to reach Saturn on 1 July 2004.
Note for editors:
Cassini-Huygens is a joint programme of NASA, ESA and the Italian Space Agency (ASI). The Cassini orbiter, built by NASA, and the Huygens probe, provided by ESA, were mated together and launched as a single package from Cape Canaveral, Florida, on 15 October 1997, by a Titan 4-B rocket. ASI provided Cassini's high-gain antenna.
Cassini-Huygens will enter orbit around Saturn on 1 July 2004. The Huygens probe will separate from Cassini to parachute through the atmosphere to the surface of Saturn's largest moon, Titan, in November that year.