On Thursday, February 1st, 2017, NASA’s Juno spacecraft completed its fourth 53.5 day orbit of Jupiter since its arrival on July 4th, 2016. The vehicle, reached perijove – the point at which it is closest to Jupiter’s cloud tops at 12:57 GMT (07:57 EST), just 4,300 km (2,670 mi) above the cloud top at a velocity of about 208,000 km/h (129,300 mph) relative to the planet.
As there were no plans to utilise the craft’s main engine to slow the craft into a 14-day orbit around Jupiter – a issue with a potentially faulty set of valves in the motor system is still being investigated – the spacecraft was able to conduct a “close-up” data gathering exercise as it swept around Jupiter, gathering data on atmospheric radiation and plasma.
Also active during the flyover was the spacecraft’s imaging system, dubbed “JunoCam”. This has already captured some stunning images of Jupiter during past perijoves, and the hope is it will have done so again. Thanks to an outreach programme in which NASA invite “citizen scientists” to download raw JunoCam images and process them at their leisure, together with a programme that allows the public to suggest areas the camera might image during each perijove, JunoCam has become extremely popular.
The next close flyby will be on March 27th. It’s not clear yet whether this will be a science pass, or whether the Juno Mission team will risk firing the vehicle’s motor to slow it into the planned 14-day orbit. If they do, then the science suite will likely be powered down to conserve electrical power during the manoeuvre.
But even if Juno doesn’t achieve that final 14-day orbit, its science mission will not be unduly compromised. The craft will be able to meet all of its mission goals even if it remains in the 53.5-day polar orbit it currently occupies.
The Jovian system is a place of intrigue. Not only is Jupiter a potential key to helping us understand the evolution of such gas giant planets, it sits at the centre of a gigantic magnetosphere so vast and powerful, it extends 5 million kilometres (3 million miles) towards the Sun, and reaches out as far as the orbit of Saturn – 651 million kilometres (407 million miles) – in the other direction.
All of Jupiter’s Galilean moons, Callisto, Ganymede, Europa and Io, orbit within this magnetosphere, “bubble” and are affected by it. However, it is innermost Io which has the greatest interaction, and a proposal has been put forward to have Juno examine the relationship between Io and Jupiter in greater detail.
With Jupiter on one side, and the other three big moons on the other, Io, roughly 320 km (200 mi) small in diameter than the Moon, is constantly being flexed by the opposing gravitational forces. This flexing physically manifests in the moon being the most volcanically active place in the solar system. At any given time, Io has an estimated 300 active volcanoes belching sulphur, sulphur dioxide gas and fragments of basaltic rock up into the space above itself to interact with Jupiter’s magnetosphere.
As the material from the eruptions rise from Io, it is bombarded by high-energy electrons withing Jupiter’s magnetsphere. These ionise the ejected material, forming a vast plasma torus of highly energised (aka radioactive) particles around the Jupiter and straddling Io’s orbit. In addition, Jupiter’s magnetic field also couples Io’s polar atmosphere to the planet’s polar regions, pumping this ionised material through two “pipelines” to the magnetic poles and generating a powerful electric current known as the Io flux tube, which can most visibly be seen (if you are close enough) as Jupiter’s polar aurora.
Both the plasma torus and the flux tube are utterly lethal environments, and they are one of the reasons why Juno’s science instruments and critical electronics are, as far as is possible, all contained in a radiation hardened “vault” nestled at the heart of the vehicle. However, there is much to be gained from a greater understanding of these plasma streams, and a team from Boston University have submitted a paper to NASA showing how Juno might employ a technique called radio occultation to indirectly probe the plasma torus.
The idea is that as Juno swings around Jupiter in its polar orbit, it must pass through the plasma torus. If it is signalling Earth as it does so, the radio waves will be refracted by the ionised particles in the plasma, causing frequency changes to occur. If measured, the frequency changes would point to how much material is within the different part of the torus, and how the density of that material changes over time. Thus greater understanding of the relationship between Jupiter’s magnetosphere and Io can be gained, an with it a deeper understanding of Jupiter’s magnetic field.
NASA has not indicated whether the idea will be folded into Juno’s overall mission, but given the alignment between the idea and the mission’s overall goals, it would seem to be advantageous were the approach to be used.
China’s Lunar Missions
China’s state-run Xinhua news agency has confirmed that the country is aiming for a November 2017 launch of the ambitious 4-part Chang’e 5 (“Moon Goddess 5”) mission, intended to land an automated vehicle on the Moon, gather around 2-3 kg (4.5lb – 6.75lb) of lunar samples, and then return them to Earth.
Massing eight tonnes at launch, Chang’e 5 will be lifted on its way to the Moon by one of China’s Long March 5 rockets. In all, it will comprise four modules: an orbiter vehicle, a lander which integrated ascender module, and an Earth re-entry module. Of the four elements, the last has already been tested during the Chang’e 5-T1 mission which took place between October 23rd, 2014 and October 31st, 2014. This saw the return module flown to the Moon and back before making a safe re-entry into Earth’s atmosphere followed by a parachute landing,
On its arrival in lunar orbit, Chang’e 5 will split into two operational unit: the orbiter / re-entry module remaining in orbit while the combination of lander and ascent module attempt a soft landing on the Moon. Once there, a sample gathering / transfer mechanism will be used to gather rock and regolith samples and place them inside the ascent module. The ascent module will than lift-off from the lander and rendezvous in orbit with the orbiter / re-entry module, transferring the samples to the latter before being discarded. Orbiter and re-entry module will then head back to Earth, parting company along the way so that the re-entry module can deliver the sample to Earth. If successful, the mission will see the first lunar samples returned to Earth since 1976, the last such sample return mission being the former soviet Union’s Luna 24.
Chang’e 5 will be followed in 2018 by Chang’e 4, a further ambitious automated mission, this time to the far side of the Moon. And if the number sequence for the missions seems odd, that’s because Chang’e 4 was a back-up mission should the Chang’e 3 mission fail for any reason. However, as the latter succeeded in its aim of placing a lander and rover on the Moon, Chang’e 4 was re-purposed for the far side mission, which was pushed back to later 2018 to give priority to Chang’e 5’s sample return mission.
Like Chang’e 3, the far side mission will deliver a rover to the surface of the Moon, with a separate communications satellite in lunar orbit acting as a relay between surface vehicles and Earth. While it has yet to be confirmed, the mission is said to be targeting the Aitken Basin.
In addition to scientific research, both Chang’e 4 and Chang’e 5 will act as potential demonstrators for techniques which could be used in China’s human spaceflight ambitions as well.
Google Lunar X Prize: The Final Five
The final five contenders for the US $30 million prize pot of the Google Lunar X-Prize have been confirmed.
The competition is the latest iteration of the X Prize series, which kicked-off back in May 1996 with what was to become the Ansari X Prize, which offered a US $10 million prize to the first non-government organisation able to launch a reusable manned spacecraft into space twice within two weeks. The Google Lunar X Prize was introduced on September 13th, 2007, and challenges non-government teams to successfully launch, land, and operate a rover on the surface of the Moon.
Up to US $20 million is on offer to the first team to land a rover on the Moon which can travel at least 500 metres (1,625 ft) and transmits high-definition images and video back to Earth before the end of 2017. A prize of US $5 million is on offer to the second team to achieve the same goals, with a further US $5 million in potential bonus prizes for extra features such as roving further than 5,000 metres, capturing images of man-made objects on the moon, or surviving a lunar night.
Some 32 original entrants were whittled down to 16, and these were further reduced to a handful, al of whom had to submit a launch contract for their rover vehicle to the X Prize Foundation, so that it could be verified before the end of 2016. This reduced the field to the final five contenders.
The Five teams are a mix of for-profit and non-profit companies and organisations. Two of the teams – the for-profit Moon Express, who plan to go on to mine the Moon for natural resources in the future, and the non-profit SpaceIL from Israel, are developing craft which land on the Moon then use their motors to fly short distances. This actually disqualifies them for some of the prize money, as the contest rules stipulate the rover must be mobile on the surface of the Moon.
The remaining three entries – the non-profit Japanese Hakuto, non-profit multi-national Synergy Moon and the for-profit Team Indus from India – all utilising “traditional” wheeled rovers, as so qualify for the mobility plan. In addition, Hakuto and Team Indus have combined resources to share a launch vehicle. No launch dates have been release, but as noted above, missions must be carried out by the end of 2017 in order to qualify for any of the prize money.
At the start of 2016, Academy Award-nominated director Orlando von Einsiedel and Direcotr / producer J.J. Abrams were contracted by the X-Prize Foundation to produce a documentary following the (then) 16 teams attempting to make the final selection, and I’ve included the trailer below.