In my last Space Sunday update, I was writing at the very time a final effort was being made to see a little Japanese space probe finally achieve an operational orbit around Venus, precisely five years to the date after the first attempt failed as a result of the craft’s primary motor malfunctioning.
At the time of writing that update, it appeared as if little Akatsuki (“Dawn”), designed to probe the Venusian climate and atmosphere had finally arrived in orbit about the planet, but as I noted, final confirmation would take a while. In the end, it wasn’t until Wednesday, December 9th that the Japan Aerospace eXploration Agency (JAXA) did confirm Akatsuki, less than a metre on a side (excluding its solar panels) was secure in its orbit around Venus and would likely be able to complete its mission.
Following the failure of its main engine on December 7th 2010 during a critical braking manoeuvre, the probe had finished up in a heliocentric orbit, circling the sun and heading away from Venus. However, orbital mechanics being as they are, both the probe and Venus would occupy the same part of space once again in December 2015, presenting final opportunity to push the probe into orbit using its RCS manoeuvring thrusters. This is precisely what happened on the night of December 6th / 7th, 2015. While not designed for this purpose, a set of the probe’s RCS thrusters undertook a 20-minute burn just before midnight UTC on December 6th, and preliminary telemetry received on Earth some 30+ minutes later showed Akatsuki had achieved sufficient braking to enter a very elliptical orbit around Venus.
Data received since then show that the craft is in an eccentric orbit with an apoasis altitude (the point at which it is furthest from the surface of Venus) of around 440,000km, and a periapsis altitude (the point at which it is closest to the surface of Venus) of around 400km. This is a considerably broader orbit than the mission had originally intended back in 2010, giving the vehicle an orbital period of around 13.5 days, the orbit slightly inclined relative to Venus’ equator.
In order to maximise the science return from the vehicle – which is now operating well in excess of its designed operational life – JAXA plan to use the next few months to gradually ease Akatsuki in an orbit which reduces both the apoasis distance from Venus, and bring down the orbital period to about 9 days.
These manoeuvres will likely be completed by April 2016, allowing the full science mission to finally commence. This is aimed at learning more about the atmosphere and weather on Venus as well as confirm the presence of active volcanoes and thunder, and also to try to understand exactly why Earth and Venus developed so differently from each other, despite being seen as sister planets in some regards.
Even so, right from its arrival in its initial orbit, Akatsuki has been flexing its muscles, testing its imaging systems and returning a number of preliminary pictures of Venus to Earth, such as the ultra-violet image shown above right, captured just after the craft finally achieved orbit.
Curiosity reaches Sea of Sand
NASA’s Mars Science Laboratory rover Curiosity has reached the edge of the major “sea” of sand dunes located on the flank of “Mount Sharp”. Dubbed the ““Bagnold Dunes” after British military engineer Ralph Bagnold, who pioneered the study of sand dune formation and motion, doing much to further the understanding of mineral movements and transport by wind action. Such studies are seen as an essential part of understanding how big a role the Marian wind played in depositing concentrations of minerals often associated with water across the planet, and by extension, the behaviour and disposition of liquid water across Mars.
Sand is not a new phenomenon for rovers on Mars to encounter – Curiosity, Opportunity and Spirit have all had dealings with it in the past; in fact Spirit’s mission as a rover came to an end in 2009, after it effectively got stuck in a “sand trap”. However, the “Bagnold Dunes” are very different to the sandy environs previously encountered by rovers; it is a huge “genuine” dune field where the sand hills can reach the height of 2-storey buildings and cover areas equivalent to an American football field.
So far, Curiosity has only probed the edge of the dune field around a sand hill originally dubbed “Dune 1”, and now called “High Dune”, using both its camera to image the region and its wheels to test the surface material prior to moving deeper into the sands. Wheel slippage is a genuine concern for the rover when moving on loose surfaces, as it can both overtax the motors and put the rover at risk of toppling over. Given this, and while there are no plans to attempt any ascent up the side of a dune, the mission team are taking things cautiously.
Tracking the “Weather” Across the Solar System
As well as vastly increasing the amount of information we have on the Pluto-Charon system (and adding to its mysteries), the New Horizons space missions has also helped increase our understanding of “weather” in the solar system.
While the space between the planets is about 1,000 times emptier than a laboratory vacuum, it is not a “perfect” vacuum. The sun is constantly releasing streams of particles with their own magnetic fields into space, called the solar wind, and denser particle clouds referred to as coronal mass ejections, or CMEs. both of these travel outwards from the Sun, forming radiation hazards for anything they might encounter. It’s the interaction of the solar wind with the Earth’s magnetic field which gives rise to the aurora, which in turn fluctuates in response to the ebb and flow of the solar wind and the violence of CMEs.
How these solar winds and CME interact with one another in deep space, and how they might impact the planets and moons of the outer solar system has been largely a matter of conjecture and theoretical models based on limited, and vry localised amounts of data gathered by various space craft sent out from Earth. However, during its nine-year journey through the solar system, New Horizons offered a unique opportunity to chart these solar “weather systems” for an extended period, tracing CME as they spread outward from the Sun, forming “weather patterns”. This has enabled scientists to start to build a better understanding of the solar wind’s role in the solar system and how it interacts with itself, how it might impact deep space missions and how it might affect the atmospheres of planets and moons like Venus, Jupiter, Saturn and Titan.
Getting Set to Fly: Tim Peake and SpaceX
On Tuesday, December 15th, A Soyuz space vehicle will lift-off from Baikonur Cosmodrome in Kazakhstan, en route to the International Space Station, led by Russian veteran of five previous missions into orbit, Yuri Malenchenko. He’s also the only groom to have been wed whilst in space: on August 10th, 2003, with the ISS passing over New Zealand, he was married to his fiancée, Ekaterina Dmitrieva, who was in Texas for the ceremony.
Joining Malenchenko in the Soyuz will be American Tim Kopra, making his second flight to the ISS, where he will eventually take over as the Expedition 47 commander, and rookie ESA astronaut Tim Peake of the United Kingdom, making his first trip into space.
The “Two Tims” mission will be only the second time a fully British national will have flown into space, the first having been Helen Sharman in 1991, when she became the first woman to visit Russia’s MIR space station as a part of the Juno mission. While fellow Britons Michael Foale, Piers Sellers and Nicholas Patrick have all flown aboard the space shuttle, to Mir and to the ISS, they have all done so as NASA astronauts under the umbrella of the US “half” of their dual British / American citizenship.
“Major Tim” was selected as one of the first six people to be admitted into a new European Astronaut Corps training programme in 2008, and commenced training in 2009. He also served on the back-up crew for the Expedition 44 crew deployment to the ISS. During his 6 months aboard the ISS, he will conduct around 256 experiments and may get to participate in extravehicular activities (EVA) as well.
Those wish to follow Tim Peake’s mission can do so via the dedicated website at Principia Mission.
A few days after the Expedition 47 Soyuz launch, on Saturday, December 19th, a Falcon 9 booster is expected to lift-off from Cape Canaveral Air Force Station in Florida. The launch will mark the first attempt to launch the Falcon 9 since June 2015, when a similar vehicle, lifting a SpaceX uncrewed Dragon resupply vehicle to the International Space Station, exploded during flight after a fuel tank suffered a structural failure.
The December 19th launch will not be to the ISS – that has just been resupplied courtesy of an Orbital ATK Cygnus vehicle, as I reported in my last Space Sunday update. Instead, the vehicle will hopefully place 11 communication “smallsats” into low Earth orbit on behalf of telecommunications company Orbcomm.
The flight – assuming all goes according to plan – will also see a further attempt to recover the first stage of the Falcon 9 booster by flying it back for a controlled landing, allowing it to be reused – a desired goal for SpaceX, as being able to re-use the generally discarded first stage of the booster would greatly reduce launch costs. As regular readers here will know, previous attempts to recover the Falcon 9 haven’t ended well. However, it is hoped that this one will be significantly different.
Rather than trying to recover the descending booster stage at sea, as has been the case thus far in SpaceX’s attempts, this flight will see the Falcon attempt a controlled return to Earth over land – at Canaveral Air Force Station in fact, where SpaceX has been spending the better part of 2015 refurbishing one of the launch pads for just this purpose.
In order to make a safe landing, a returning booster must achieve a number of things: slow down from hypersonic speeds, control its descent and make a gentle tail-first landing. To help with the latter, the Falcon 9 is equipped with sets of four deployable landing legs and steering vanes – the latter being used to steer the ungainly rocket during the final phase of its powered decent.
The video below shows how a landing should be achieved. It was shot during a demonstration test flight which saw a Falcon 9 first stage ascend to an altitude of 1 kilometre, its landing legs already deployed, and then use the steering vanes to guide itself back to a controlled landing.
Catch a Falling Star
the end of the year brings with it the Geminid meteor shower, the result of asteroid 3200 Phaethon, which passes close to the sun every year, slowly crumbling away as a result of the heat and the solar wind. As it does so, it leaves behind a trail of debris behind which Earth passes through every December, giving rise to what can be a spectacular display of meteors which appear to originate in the constellation of Gemini, hence their name.
The 2015 Geminid event reaches its peak overnight on Sunday 13th and Monday 14th December, although it has already proven quite stunning this year. Those in the northern hemisphere are best placed to see it (clear skies allowing): with a best time for viewing occurring at around 02:00-03:00 on the morning of December 14th, local time – although the meteors should be visible from about 22:00 onwards, on the 13th. Catch this report from EarthSky for tips on how best to see them.