Space Sunday: celestial harmonics, breathing air and singing for Pluto

July 14th: Jupiter with Io, Europa and Ganymede as seen by Juno after the craft had finished its critical orbital burn to slip into a 53.5 day orbit around the giant planet
July 10th: Jupiter with Io, Europa and Ganymede as seen by Juno after the craft had finished its critical orbital burn to slip into a 53.5 day orbit around the giant planet on July 4th. Credit: NASA/JPL / SwRI / MSSS (click and image for full size)

The banner image, captured by NASA’s Juno spacecraft, might look like the one I used in my last Space Sunday update, but there is one important difference. The images used last time around had been captured by Juno on June as it approached the Jovian system on June 29th, five days before the craft had to complete a critical engine burn whilst almost scraping the planet’s cloud tops, to place itself in an extended orbit around Jupiter. The image above was captured on July 10th, as Juno headed away from Jupiter, having successfully completed the manoeuvre.

At the time the picture was captured, 17:30 UTC on July 10th, 2016, Juno was already  4.3 million kilometres (2.7 million miles) distant from the planet, and heading away from it at a relative velocity of 18,420 km / hour (11,446 mph) and decelerating under the influence of the Jupiter’s gravity.

Juno's flight around the poles of Jupiter and it's position on July 10th, as seen by the NASA Eyes application
Juno’s flight around the poles of Jupiter and it’s position on July 10th, as seen using the NASA Eyes simulator (click for full size)

Juno’s imaging system – JunoCam – had, along with other major systems aboard the craft, been shut down prior to the July 4th engine burn, both to conserve power – Juno had to turn its solar panels away from the Sun during the burn manoeuvre, limiting the available electrical power – and to protect them through the initial passage through Jupiter’s tremendous radiation fields. It wasn’t until July 6th that the instruments were all powered back up, and after testing them, the July 10th exercise was the first opportunity to have a look back at the Jovian system.

Juno will keep travelling outwards from Jupiter until the end of July, slowing to a relative velocity of just 1,939 km/h (1212 mph), before it starts to “fall” back towards the planet, making a second close flyby on August 27th. At this time, the craft will pass just 4,142 km (2,575 mi) above the Jovian cloud tops at a speed of 208,11 km/h (129,315 mph). More importantly, all of vehicle’s science instruments will remain powered-up, and JunoCam in particular should gain some stunning images of Jupiter during this second close pass.

To celebrate Juno’s arrival around Jupiter, NASA released a time-lapse video of the Jovian system as seen by the approaching spacecraft. It begins on June 12th with Juno 16 million km (10 million mi), and ends on June 29th, when JunoCam was shut down and Juno was 4.8 million km (3 million mi) distant.

Made possible by Juno’s high angle of approach into the Jovian system, it is the first close-up view of celestial harmonic motion we’ve ever had. Also, the 17-day duration of the movie means we see Callisto (flickering very faintly) make a full orbit around Jupiter, and get to see Ganymede, Europa and Io (counting inwards towards the planet) each experience eclipse as they pass through Jupiter’s shadow. Note that the flickering exhibited by the moons is an artefact of JunoCam, which is optimised to image bright features on Jupiter, rather than capturing the (relatively) dim pinpoints of the distant moons as they circle the planet.

Curiosity Resumes Operations as 2020 “Sister” Takes Shape

In my last update I reported that NASA Mars Science Laboratory, Curiosity, had entered a “safe” mode on July 2nd.  On July 9th, the mission team successfully recovered the rover from this safe mode – a precautionary state the rover will set for itself should it detected an event which could damage its on-board systems – and then subsequently returned Curiosity to a fully operational status on July 11th.

The cause of the problem lay in  a glitch in one of the modes by which images are transferred from the memory in some of the rover’s camera systems to its main computers. This generated a data mismatch warning, prompting the rover to active its “safe” mode and call Earth for assistance. Use of this particular data transfer mode between the identified camera systems and the computers is now being avoided in order to prevent a repeat of the problem.

Meanwhile, NASA’s next rover mission – designated Mars 2020 at present, as it will launch in the summer of that year to arrive on Mars in February 2021 – is taking shape. The basic vehicle will be based on the Curiosity class of rover, but will carry a different science suite and have somewhat different capabilities.

A CAD image of the Mars 2020 rover: visibly similar to MSL's Curiosity rover. Credit: NASA
A CAD image of the Mars 2020 rover: visibly similar to MSL’s Curiosity rover. Credit: NASA

In particular, the new rover will carry an entirely new subsystem to collect and prepare Martian rocks and soil samples which can be stored in sample tubes. About 30 of these sample tubes will be deposited at select locations, so that they might be collected by a possible future automated mission and returned to Earth for direct analysis for evidence of past life on Mars and possible health hazards for future human missions.

Two science instruments mounted on the rover’s robotic arm will be used to search for signs of past life and determine where to collect samples by analysing the chemical, mineral, physical and organic characteristics of Martian rocks, while a suite of advanced camera systems will be housed on the vehicle’s mast. As with Curiosity, Mars 2020 will carry a comprehensive meteorological suite for monitoring the Martian environment and weather, together with a ground penetrating radar system for determining what is going on under the rover’s wheels.

Mars 2020 will be delivered to the surface of Mars using the same Entry, Descent and Landing (EDL) approach as Curiosity, including the “skycrane” system which hovers over the surface of the planet whilst gently winching the rover to the ground. However, this  system will have some significant new capabilities, notably a terrain-relative navigation system. This will use on-board analysis of downward-looking images taken during descent, matching them to a map in the rover’s computer that indicates zones designated as either “safe” or unsafe for landing. If the terrain below the descending lander is designated “unsafe”, the vehicle will divert itself, tracking to a designated “safe” region prior to deploying the skycrane. In this way, Mars 2020 should be able to access parts of Mars previously thought to be inaccessible to landers, but which are of significant scientific interest.

On-board terrain navigation, couple with advances in the vehicle's landing capabilities will allow Mars 2020 steer itself to a safe landing on Mars
On-board terrain navigation, couple with advances in the vehicle’s landing capabilities will allow Mars 2020 steer itself to a safe landing on Mars

Also as a part of the EDL system will be a new camera and microphone, allowing us to see and hear the vehicle’s passage through the Martian atmosphere to touch-down, and afterwards hear the sounds of Mars.

Finally, and in a further effort to prepare the way for missions on Mars, the rover will carry out the first test of “in-situ resource utilisation” (ISRU) on Mars, a means by which water, oxygen and methane can be manufactured out of the Martian atmosphere using an exothermic process called the Sabatier reaction, first discovered in the early years of the 20th century.

Use of this reaction was first proposed in the 1990s as a means to reduce the payload mass for human missions to Mars, allowing fuel (oxygen and methane) to be produced on Mars and used by vehicle returning crews from Mars to Earth. However, the technique – which has been extensively shown to work in simulated Mars conditions here on Earth – has numerous possible applications on Mars. I’ll have more to say on it, Mars 2020 and human missions to Mars in future Space Sunday articles.

Breathing Air into Space

If the idea of using a planet’s atmosphere to produce fuel sounds exotic, then how about the idea of using a planet’s atmosphere as rocket fuel?

REL's Skylon is a potential vehicle for their SABRE air-breathing rocket motor
REL’s Skylon is a potential vehicle for their SABRE air-breathing rocket motor. Credit: Reaction Engines Limited.

This is precisely the idea Reaction Engines Limited (REL) in the UK are developing.  Called SABRE (Synergistic Air-Breathing Rocket Engine), the idea, first mooted 30 years ago, moved a further step towards reality on Tuesday, July 10th, 2016, when the European Space Agency signed a deal to provide the project with a further 10 million Euros (US $11,036,500) of financing.

In order to push a payload into space, conventional rockets must carry a huge amount of fuel, a good part of which is an oxidiser such as liquid oxygen. This is combined with fuel in the rocket’s combustion chamber to generate thrust. It also accounted for a lot of mass (even if it is burnt off during the ascent); around 270 tonnes of liquid oxygen has to be carried by the Falcon 9 1.1 rocket at launch, for example.Even allowing for attempts to make reusable rocket systems such as the Falcon 9, this still adds up to a lot of extra expense involved in lunching things into space.

SABRE seeks to get around this by using the Earth’s atmosphere as the oxidiser. While there are significant technical challenges in doing so – such as keeping the air cool enough so that the frictional / compression heat generated as the air passes through the engine doesn’t actually melt it – being able to use the denser part of the Earth’s atmosphere in this way means far less oxidiser has to be carried aloft by the launch vehicle. So much so that computer modelling shows that SABRE could offer a 8x improvement in propellant consumption compared to a conventional rocket. The unique nature of the engine also makes the potential for an aircraft-like, single-stage to orbit (SSTO) launcher, such as REL’s proposed Skylon, a distinct possibility.

The ESA deal, first announced at the end of 2015, is part of an overall package which includes £50 million (US $65,970,000) from the UK government. It will allow REL to go ahead with the development and construction of full ground test demonstrator versions of SABRE by the end of 2020 which, if successful, could see the engine in use within the following decade. Nor are the UK government and ESA alone in expressing interest in SABRE; in June 2016, as a result of growing interest in SABRE on the part of the US government and American aerospace companies, REL announced they were establishing an American subsidiary, Reaction Engines Inc.

REL is also one of five industrial teams wanting to operate orbital or suborbital launch vehicles from British territory on a commercial basis. The others being Sir Richard Branson’s Virgin Galactic, Europe’s Airbus Safran Launchers, Deimos UK and Firefly Space Systems of the USA, and America’s Lockheed Martin.

New Horizons: Flyby First Anniversary

An artist's impression of the Antarctic region of Pluto, a place where the Sun hasn't shone for the last 20 years and will not shine on again for another 80, but above which Charon looms. Credit: NASA
An artist’s impression of the Antarctic region of Pluto, a place where the Sun hasn’t shone for the last 20 years and will not shine on again for another 80, but above which Charon looms. Credit: NASA

One year ago, on July 14th, 2015, NASA’s New Horizons spacecraft shot by Pluto and Charon at the outer reaches of the solar system. The images and data it returned have revolutionised our understanding of these remote worlds – and potentially overturned a lot of ideas surrounding the formation of small rocky bodies in the outer solar system.  As such, I couldn’t let the anniversary pass without marking it – but how?

In the end, I opted to dive back to August 2015 and grab a video put together by the interns at the Space Exploration Sector of John Hopkins University’s Applied Physics Laboratory (APL being the folk who  designed, built, and operate the New Horizons spacecraft and managed the mission for NASA’s Science Mission Directorate), who offer a fun (and informative) parody of Nsync’s Bye, Bye, Bye. Given I also opened this update with a reference to celestial harmonic motion, it seems appropriate I close it with an actual song 🙂 .