Nasa's Cassini spacecraft to begin final journey around Saturn


Nasa’s Cassini spacecraft is set to commence its final five orbits around Saturn, marking the final phase of its exploration mission of the planet.

Cassini will make the first of the five passes over Saturn on 13 August.

The closest encounter between the spacecraft and Saturn will occur when the former comes between 1,630km and 1,710km above the planet's cloud tops.

Cassini is also expected to experience an atmosphere dense enough to require the use of its small rocket thrusters to maintain stability.

Nasa will consider the second day of Cassini’s final mission as nominal if thrusters operate between 10% and 60% of their capability. If they are forced to work harder due to increased density, the agency will increase the altitude of subsequent orbits.

This is known as ‘pop-up manoeuvre’, where the thrusters will be used to raise the altitude of closest approach on the next passes by approximately 200km.

"The team is confident that we understand how the spacecraft will behave at the atmospheric densities our models predict.”

On 11 September, Cassini is expected to face a distant encounter with Saturn’s moon Titan.

The encounter will act as a gravitational version of a large pop-down manoeuvre, thereby slowing Cassini’s orbit around Saturn and bending its path slightly to send the spacecraft toward its plunge into the planet. The plunge is planned to take place on 15 September.

During the final phase, the spacecraft’s instruments are expected to make detailed, high-resolution observations of Saturn's auroras, temperature, and the vortexes at the planet's poles.

Nasa Jet Propulsion Laboratory Cassini project manager Earl Maize said: “Cassini's Titan flybys prepared us for these rapid passes through Saturn's upper atmosphere.

“Thanks to our past experience, the team is confident that we understand how the spacecraft will behave at the atmospheric densities our models predict.”

The agency also noted that it will try to activate the spacecraft’s seven science instruments, including INMS and reporting measurements, during Cassini’s half-orbit plunge in near real-time.


Image: Artist’s rendering shows Cassini as the spacecraft makes one of its final five dives through Saturn's upper atmosphere in August and September. Photo: courtesy of Nasa.