Spacecraft and its probe Huygens due to enter orbit on 1 July after seven-year journey
The joint NASA/European Space Agency orbiter Cassini and its probe Huygens are scheduled to arrive in orbit 20,000km (12,500 miles) from Saturn on 1 July, following a 96min rocket burn to slow the 5.5t orbiter from its 5.2 km/s (3.3 miles/s) transit speed.
The planned four-year tour of the planet and its satellites could be at risk if there is a problem with the main engine burn, says Dr Andrew Coates, head of the University College of London's Cassini-Huygens team, providing electron spectrometer equipment on the mission. "Of the 96min, 78min are absolutely crucial to slow the craft down, with the remainder necessary to align the orbiter on to its planned route. If the rocket fails to ignite and Cassini fails to be inserted into the orbit, there is no Plan B," he says.
A partial burn would result in the orbiter's tour being altered and extended, Coates says. NASA says the spacecraft's main engine was fired for 6min late last month and so far no problems have been reported. The Cassini-Huygens mission is a co-operative programme between NASA, ESA and Italian space agency ASI.
The duo has travelled 3.5 billion km over the past seven years on a mission to observe Saturn's atmosphere, rings, icy satellites and magnetosphere. The 319kg Huygens probe will be jettisoned on Cassini's third orbit on 25 December, and is expected to land on Saturn's moon Titan, which spins in a retrograde orbit, in mid-January.
During its mission, the Cassini orbiter will approach within 1.3 radii - 77,500km - of Saturn, producing photographs of up to 2km resolution. The spacecraft will also fly by six of Saturn's other moons.
JUSTIN WASTNAGE / LONDON
Source: Flight International
