Deciphering the Universe with Rosetta

Edward Bach was involved in a key part of the mission.

Seven years after I first interviewed Edward on the work he was doing in Dublin at the time with his company ‘Captec’– what he referred to as the ‘Rosetta mission (whose name came from the Rosetta stone, which helped deciphering the hieroglyphs) (see Science Spin 21 and read our pre launch feature on the rosetta here: ). Nobody really heard or cared at the time about the Rosetta spacecraft and its lander, Philae, which were supposed to carry out a long journey into space towards an unlikely rendezvous with a mysterious comet so many years ahead.

“C’est vrai?” I answered tongue in cheek, as I actually knew it was true. I had heard it in the news the day before. After 10 years, 5 months and 4 days, the moment had finally arrived; the day when the spacecraft and its lander were going to make history. And Edward Bach, who was involved in a key part of that mission – the timely separation of the lander from its spacecraft–, had been following all the stages.

A mosaic of four images captured by Rosetta’s camera showing the two-lobed comet.

A mosaic of four images captured by Rosetta’s camera showing the two-lobed comet.

“Where is the lander now?” I asked. “It should land on the comet sometimes around 4pm Irish time”, Ed replied. But for now what kept him excited was that the delicate separation process they had come up with, which was quite original, had worked. “How did it work?” I asked, though I reckon he had probably told me already a few times while he was working on it.

He took on a serious tone: “The separation was by means of a spring release which was held in place by a thick wax coating” he explained.” When the coating was heated until it melted, separation occurred”. The idea, and what was original about it, is that it was not an ‘explosion type’ separation, which once initiated would be impossible to stop. “Our system means that the process was also reversible simply by removing the heat before the wax had melted”, Ed said. Ensuring some level of control probably sounded like good idea in a mission so far away from earth that it takes 30 minutes for any signals to travel from there at the speed of light.

The comet viewed from a distance of apx 3 km during descent of the Philae lander. Image: ESA

Edward told me that he took part in the ‘software’ part, including the analyses and verifications of the flight software requirements, code and design, as well as its validation with simulations of the spacecraft and its environment. “I participated in both activities, with my role in the validation more as analyst and technical manager and my role in the verification more as engineer”, he explained.

He was helped by some of his colleagues as the small team also included one analyst (also project manager), one developer, and two testers.

While Captec were involved in the flight software for the lander, another Irish company, Space Technology Ireland Ltd (STIL), was responsible for its hardware. Ed explained: “STIL participated in the flight hardware by building the computer on which the Captec software executed; they also provided a clean room for assembly and test”. Altogether hardware and software supported communications between the spacecraft and the lander.

One of the numerous pits on the comet surface viewed from a disrtance of 7.7 km. It is thought that gas vents into space from these pits carrying dust from the comet.The landing

It took another 7 hours of careful approach before Philae successfully made it to the surface of the four-kilometer-wide comet 67P/Churyumov-Gerasimenko, a little bit after 16.00 GMT.

As we have all heard since, Philae failed to anchor to the surface of the comet as its harpoons did not fire. The one-meter edge high-tech cube, which weighs 100 kilograms on Earth, only weighs a few grams on the comet given its small gravitational field. The lander thus rebounded very slowly, once, twice, moving away from the landing site that has been carefully chosen to optimize sunlight. At the original landing site Philae was expected to receive around 6.5 hours of illumination per 12.4 hour comet day; at its new location, it receives just 1.3 hours.

The mission

Never mind, Philae was still able to achieve its mission. About 56 hours of continuous scientific measurements of chemical, physical and mineralogical properties of the comet core and its surface were performed in the hope of achieving a greater understanding of the comet’s origins and properties, and hence the evolution of the Solar System.

Comets are of special interest to scientists as they are believed to be the witness of the formation of our solar system. But aren’t all its planets as well? As Ed explained to me. there is a difference. Compared to planets like early earth which were bombarded with asteroids, comets are very stable environments. Their characteristics have not changed much since 4.5 billion years ago when the solar system was formed. And it is possible also that such stability was what made the emergence of life possible. “So we are looking for traces of water that could exist at particular spots on the surface, or in the core, and within those, traces of organic molecules”, said Edward.

Preliminary results have already been published; but data from Philae are still being analysed. And according to Ed, until their publication, the forefront findings of this pioneer expedition are likely to be kept top secret (see box on next page for details of scientific goal and preliminary findings).

A 45 metre wide and 25 metre high boulder is the largest among others lying upon the dusty surface of the comet’s larger lobe.Preliminary results of scientific analysis of Comet 67P/Churyumov-Gerasimenko *

  • Remarkably heterogeneous body with a varied surface exhibiting structures similar to ‘goose bumps’, which the re searchers have yet to explain
    • Roughly 70 percent of the comet’s surface has been mapped
    • 19 regions found, given Egyptian god names
    • five distinctive types that predominate on the surface: dust-shrouded areas, brittle material, large-scale depressions, smooth terrains and exposed, consolidated structures
  • Among the darkest objects in the Solar System – its surface reflects a mere six percent of the incident solar radiation.
    • may be due to the dark materials such as iron sulphides, dark-coloured silicates and carbon-rich compounds deposited across the comet’s surface


  • Most likely, there is little or no frozen water directly on the surface of the comet’s nucleus, as it was probably stripped during its journey through the solar system (by sublimation)
  • However, there is, undoubtedly, frozen water inside the comet

Organic compounds

  • Long chain hydrocarbons, organic compounds precursors to amino acids, have been detected
  • These compounds can only form through complex reactions at low temperatures under conditions (i.e. ultraviolet or cosmic radiation) which are only found in the outer reaches of the Solar System, beyond the orbit of Neptune.This is one of the most interesting discoveries, which would not have been possible via ground-based observations.
    • The comet may thus allow the planetary researchers to look back into the early life of the Solar System
  • This is one of the most interesting discoveries, which would not have been possible via ground-based observations.

A large fracture running across the neck between the two comet lobesWhat’s next?

On the 15th of November 2014, Philae entered in a sleeping mode. However, the official end of the mission is not expected till the end of December 2015, as the Rosetta-escorted comet continues its journey towards the sun. So what is next?

“All of the science originally planned for the lander was completed”, Ed insisted, “so now we are really talking about a prolongation of its mission”. He continued, talking about the future of the mission: “It really depends on how much power they can generate, e.g. by repositioning the lander so its solar panels are more regularly sunlit—this will determine what can be done with the lander.”

So now we have to wait it is closer to the sun to be warmed up and brought back to life. Philae needs about 17 Watts to wake up and say “hello”. In fact it is not expected to warm up before the end of March, and it’s not before May or June that it will be able to transmit to Rosetta. It will then take even longer until it is fully charged and ready to do science again.

“They are now talking about August for reengaging with the lander, which I suppose would also give some time to study its situation in more detail”, said Ed.

The observation of the comet’s activity as it approaches the Sun and its interaction with the environment is one of the scientific objectives to come. This is also one of the most challenging. “The lander is obviously quite vulnerable to jets, radiation or comet breakup or surface disturbance. All of these will be expected as the comet approaches the sun. The orbiter is less vulnerable but if it has to stay very far from the comet to avoid radiation, jets or even pieces of comet, there will be a point where it will not be able to observe much”.

An artist’s impression of the Rosetta cometary probe. The Rosetta spacecraft was launched in March 2004 and it arrived eleven years later at the comet, 67P Churyumov-GerasimenkoSo the suspense is not finished yet. And it may even continue for quite a while. As Ed noted, “Dec 2015 is the official end of mission but it might be extendable for another few months”.

Thus, Philae and its mothership may well have a few more cutting edge science to teach us before the end of the year, and beyond.

However, the biggest achievement of Rosetta may be less scientific than human. What impressed Ed most is, as he put it, “the successful international cooperation and the ability to operate for a long time, especially after undergoing deep space hibernation for several years, under widely differing conditions.”

“The Rosetta mission was definitely more interesting and challenging than a space telescope or planetary mission like Mars Express”, he concluded.

Read our pre launch feature on the rosetta here:

References: DLR (German Aerospace Center, which coordinated the lander development** ), latest results as per January 22 2015

* Preliminary results from seven of the 11 instruments on the Rosetta orbiter have been published in a special edition of the journal Science

**The lander was developed and built by an international consortium involving the French Space Agency (CNES), the Italian space Agency (ASI) and MPS under the coordination of the German Aerospace Center (DLR).

Marie-Catherine Mousseau 
Marie-Catherine Mousseau has a PhD in neuroscience from Pierre et Marie Curie University, Paris, and has an MSc in Science Communications from DCU/Queen’s. Marie-Catherine has worked as an editor of a medical periodical and is a regular contributor to Science Spin

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