Space debris: what can we do with unwanted satellites?

It's crowded up there - the many objects tracked in low Earth orbit. ESA

There are thousands of satellites in Earth orbit, of varying age and usefulness. At some point they reach the end of their lives, at which point they become floating junk. What do we do with them then?

Most satellites are not designed with the end of their life in mind. But some are designed to be serviced, such as the Hubble Space Telescope, which as part of its final service was modified to include a soft capture mechanism. This is an interface designed to allow a future robotic spacecraft to attach itself and guide the telescope to safe disposal through burn-up in the Earth’s atmosphere once its operational life has ended.

Thinking about methods to retire satellites is important, because without proper disposal they become another source of space debris – fragments of old spacecraft, satellites and rockets now orbiting Earth at thousands of miles per hour. These fragments travel so fast that even a piece the size of a coin has enough energy to disable a whole satellite. There are well over 100,000 pieces this size or larger already orbiting Earth, never mind much larger items – for example the Progress unmanned cargo module, which Russian Space Agency mission controllers have lost control of and which will orbit progressively lower until it burns up in Earth’s atmosphere.

A hole punched in the side of the SMM satellite by flying orbital debris. NASA

We don’t know exactly how many or where they are. Only the largest – about 10% of those fragments substantial enough to disable a satellite – can be tracked from the ground. In fact damage to satellites is not unknown, with Hubble and the Solar Maximum Mission (SMM) satellites among those to have coin-sized holes punched into them by flying debris. There is a risk that over the next few years there will be other, perhaps more damaging, collisions.

The soft capture mechanism was installed to prevent more space debris. Engineers worldwide are devising ingenious ways to try to limit the amount of debris orbiting the planet – for good reason. Predictions show that if we don’t tackle the problem of space debris then many of our most useful orbits will become too choked with flying fragments for satellites to safely occupy them.

At some point, there may be enough debris in a given orbit for debris-satellite collisions and debris-debris collisions to cascade out of control. This is known as the Kessler syndrome, as shown (in somewhat exaggerated fashion) in the film Gravity.

Given the degree to which we rely on satellites these days – for communication, GPS and time synchronisation, upon which in turn many vital services such as international banking rely – it’s crucial we prevent near-Earth space from reaching this point. And like it or not, one of the important steps required is to remove large defunct satellites that could become the source of many more chunks of debris.

Designed for disposal

Satellites such as the UK’s TechDemoSat-1 (TDS-1), which launched in 2014, are designed for end-of-life disposal. TDS-1 carries a small drag sail designed and built at Cranfield University that can be deployed once the satellite’s useful science life is over. This acts like a parachute, dragging the satellite’s orbit lower until it re-enters the atmosphere naturally and burns up high in Earth’s atmosphere.

TDS-1 is small enough to burn up – larger or higher satellites will require other ways of moving them away from the most important, valuable, and busy orbits. It’s possible, with enough fuel on-board (and all systems functioning after perhaps decades in space), for satellites to de-orbit themselves. Other, more exotic solutions include tug satellites using nets, tethers, and even high power lasers.

Bag it and bin it - ESA’s e.Deorbit project may use nets to collect debris and drag it into the atmosphere to burn up. ESA

However, space debris isn’t just an engineering problem. Suppose Europe develops a tug satellite and tries to de-orbit old Russian satellites, or passes close to an active US spy satellite. Clearly this could get political. Simply put, we haven’t yet found a way to use space sustainably, and the problem is almost as complex as finding ways to ensure sustainable development on Earth. What we need are practical solutions – and soon.

One that got through: part of the Delta rocket fuel tank that came back to Earth in 1997. NASA

So what will happen to Hubble, perhaps the most well-known case of a satellite that requires a retirement plan? One day, perhaps in the early 2020s, a small spacecraft will be launched to rendezvous with the space telescope. It will attach using the soft capture mechanism and then fire its engines to guide Hubble toward re-entry over the South Pacific. For a satellite as large as Hubble, it’s likely that some parts will survive re-entry so a large uninhabited region over the ocean is best suited to avoid risk of damage or casualties.

The re-entry can be tracked carefully from other satellites, aircraft, and ships – all will capture the moment that Hubble itself, having spent decades watching the heavens, will become a bright shooting star for other telescopes to capture. It somehow seems fitting that a mission as remarkable and long-lived as Hubble should itself end in a blaze of glory.

How earthquake safety measures could have saved thousands of lives in Nepal

Poorly built houses were destroyed in the earthquake. Domenico/flickr, CC BY-SA

Earthquake engineers often say earthquakes don’t kill people, collapsing buildings do. The tragic loss of life that followed the huge earthquake in Nepal on April 25 occurred despite the fact that the country is among the world’s leaders in community-based efforts to reduce disaster risk. But poverty, corruption, and poor governance have all led to a failure to enforce building codes – as has a shortage of skilled engineers, planners and architects.

Sadly the country was on its way to deploying knowledge and skills to tackle its long-term vulnerability just as the ground shook.

So why aren’t more buildings designed to withstand shaking – even extreme shaking.

To keep buildings standing, it is essential to have adequate building and planning codes, as well as proper training and certification for professionals such as engineers, architects, and planners. But having certification and codes on paper does not ensure implementation or compliance. Nepal does, after all, have some of these things. Laws and regulations must also be monitored and enforced. That is not easy in a country such as Nepal, which has isolated villages, a history of conflict and many governance difficulties.

Vast vulnerability

Financial as well as social resources are needed to set up earthquake resistant buildings. Governments at all levels need to be functioning and competent in order to engage with processes such as urban planning and earthquake-resistant construction. Citizens must trust and have the opportunity to work with their governments, including the law enforcement and judicial sectors.

It’s not just about buildings. Many non-structural measures are needed to ensure survivability in earthquakes. Appliances such as televisions, microwaves, hot water boilers, and refrigerators (which do not always exist in Nepalese homes) must be securely fastened to the floors and the walls. Otherwise, they move and topple, killing as readily as building collapse. Even in affluent earthquake-prone locations such as New Zealand and California, we see shockingly low rates of households enacting these basic measures.

Students at a Nepalese school practice earthquake preparedness. Australian Department of Foreign Affaris and Trade/flickr, CC BY-SA

But Nepal is not New Zealand or California. It has been wracked by conflict and troubled by unstable governments, not to mention the governance issues caused by being sandwiched between China and India. It has long had high poverty and low formal education rates.

Despite recent improvements, Nepal still lags behind other countries when it comes to human development and it is still seen as highly corrupt. It also scores badly on child health and gender equality measurements.

When families struggle daily for enough food to keep their children healthy, they are not likely to spend time thinking about making their home earthquake resistant.

And when children are malnourished and stunted, they perform worse in school. That leads to long-term education inadequacies that prevent them from developing into adults with the skills to lobby for adequate and enforced building codes. What’s more, when women lack the same opportunities as men, half the population is excluded from demanding and enacting good governance.

All these factors contribute to the country’s vulnerability. All these factors have led to housing and infrastructure prone to collapse in an earthquake.

Rebuilding a nation

None of these things can be solved overnight. Tackling vulnerability is a long-term process, yet earthquakes strike and bring down buildings in seconds and minutes.

As the earthquake struck, Nepalese people were working hard to overcome these vulnerability conditions. My friends and colleagues from the country have taught me plenty about retrofitting buildings and constructing earthquake-resistant homes.

There is hope Jean-Marie Hullot/flickr, CC BY

They travelled to communities with small shake tables, which are used to simulate earthquakes by shaking model houses or building components, showing the difference between an earthquake-resistant house and a non-earthquake resistant house. They made many schools safe. They taught school children and their parents about earthquake-safe behaviour.

A shake table demonstration for Earthquake Safety Day 2007 in Nepal. NSET, Nepal., Author provided

These efforts saved hundreds of lives, if not more, during the recent tremors. With a few more decades, a mere instant in geological time, they could have made Nepal comparatively safe from earthquake disasters despite earthquakes. In that time, so many more buildings would have been retrofitted, we might have had adequate building code enforcement, and most importantly, an earthquake-educated and vulnerability-educated generation would have started to take power.

Nepal must now continue these efforts in order to avoid similar future devastation. We can be optimistic. Education is happening – for boys and girls. Women are increasingly being given equal opportunities as men. This means the Nepalese people are taking charge of their own health, their own environment, and their own sustainability. That is vulnerability reduction over the long-term.

Forget the James Webb, a future high-definition telescope could probe life on exoplanets

Bigger but not better than Hubble. The James Webb's primary mirror. NASA/wikimedia

The James Webb Space Telescope will be Earth’s premier space observatory for the next decade, serving thousands of astronomers worldwide. However its scientific mission will be limited. Unlike Hubble, which is nearing the end of its scheduled life, the James Webb will cover a much smaller part of the electromagnetic spectrum. Instead, a proposed high-definition space telescope is the only way to image Earth-like planets orbiting others stars and study them in detail.

While such a project is being studied by a consortium of scientists in response to a NASA call for ideas for large future space missions, it has so far not been formally approved. But it is really urgent that we start working on this project now, because the planning timescales for large missions of this kind are long. Even if we started to build it right now, it would still not be ready before 2030 at the earliest.

The limits of James Webb

Hubble, in low Earth orbit since 1990, has been a great success and has demonstrated the many advantages that space telescopes have over ground-based telescopes. Its successor, the James Webb, which is due for launch in 2018, is an even larger instrument, with a 6m diameter mirror compared to Hubble’s 2.4m. Just like Hubble, it will be able to avoid the disturbing effects of the Earth’s atmosphere.

Hubble exceeded our expectations. NASA

Its scientific mission includes searching for light from the first stars and galaxies and to study the formation and evolution of galaxies. This is more easily achieved by measurements in the near-infrared, which is why it will not measure visible or ultraviolet light like Hubble. While James Webb will be able to deliver some amazing science – it will collect much more light and will be able to look deeper and farther back in time in the universe – the lack of ultraviolet measurements is a major drawback. Ultraviolet can only be observed by space telescopes like James Webb, it cannot be picked up from the ground as it is blocked by the Earth’s atmosphere. Astronomers will therefore completely lose access to UV when Hubble dies.

High definition is the way forward

ET phone home. Artist’s impression of an exoplanet. NASA/JPL-Caltech/flickr, CC BY-SA

The proposed High Definition Space Telescope, which would have a 10-12m aperture, would be tuned to work in the UV and visible, as well as the infrared.

The aim of the NASA project is to understand the technical challenges now so that they can be solved before any construction begins.

The photon-counting detectors in the proposed HDST would have a higher count rate per pixel and lower noise than James Webb and Hubble. AURA/NASA presentation

A facility would be a general, all-purpose observatory that would deliver some amazing and often unexpected science. However, the most compelling case for this telescope and one of the most exciting pieces of science that can be conceived, I believe, is the ability to image tens of Earth-like planets orbiting others stars and study them in detail. By looking at the chemical signatures in their atmospheres, it will be possible to work out if life exists and understand how common it is in our galaxy.

To do this, the telescope would be fitted with a disk to block the bright surface of stars, which would allow direct imaging of exoplanets. The group studying the telescope says most of the technologies needed for the mission are already being developed as part of other NASA programmes. The telescope could therefore be credibly be put forward to NASA’s Decadal Survey in 2020, which will identify and prioritise scientific questions and observations.

In the meantime, while we prepare for this over the next couple of decades, we should consider going back to Hubble with the next generation of human-carrying space vehicles, such as NASA’s Orion capsule, and service it at least one more time.

Computers are knocking on the door of the company boardroom

What's your golf handicap old chap? Mopic

While women sitting on company boards remains a much-discussed topic, there is something new waiting to take a seat at the table: artificial intelligence, computers with company voting rights.

Deep Knowledge Ventures has appointed an algorithm called VITAL (Validating Investment Tool for Advancing Life Sciences) as a member of its board. It uses state-of-the-art analytics to assist in the process of making investment decisions in a given technology.

Of course, companies have used computer assisted analysis to analyse investment opportunities for a long time, but is the vision of a computer with equal voting rights as human board members a bit far-fetched?

Defining artificial intelligence

Alan Turing Wikimedia Commons

What does the future hold with regard to the influence of computers on business decisions – and can they ever be used in place of a human board member? The Turing Test, formulated by Alan Turing in the 1950s, provides a strict interpretation of machine intelligence. A human participant must be unable to tell whether they are communicating (through a typed, text medium) with a computer or a human. If the human participant cannot reliably tell whether their conversation partner is a computer, then Turing would argue the computer has demonstrated intelligence.

Numberphile: The Turing Test

Not everybody agrees that passing the Turing Test is enough for a computer to exhibit intelligence. In his Chinese Room argument, the Stanford philosopher John Searle described a closed room, into which a sentence written in Chinese is fed. A response emerges from the room, written in Chinese, that correctly answers the questions or conversational cues in the sentence submitted. The assumption could be made that inside the room is someone that can speak Chinese.

Instead, inside the room is a human who cannot speak Chinese but is equipped with manuals that exhaustively provide the appropriate Chinese characters to produce in response to those received. The argument holds that an appropriately programmed computer (the person in the room) could pass the Turing Test (by producing convincing Chinese) but would still not have an intelligent mind that we would regard as human intelligence (by understanding Chinese).

The Chinese Room

A computer in the boardroom

If we want computers to make business decisions and even have equal voting rights on a company board, what would it have to do in order for the other board members to have confidence in its decisions?

Part of the challenge of the Turing Test is syntax versus semantics. Compare the sentences “Fruit flies like bananas” and “Time flies like an arrow”. The sentence structure is similar but the meaning is entirely different, making it a linguistic challenge.

Even a very simple conversation relies upon a substantial amount of linguistic knowledge and understanding. Consider the following questions:

• What was the result of the big match last night?

• I have K at my K1, and no other pieces. You have only K at K6 and R at R1. It is your move. What do you play? (these chess moves are from Turing’s original paper)

• What book do you think of if I say 42?

These might seem easy for humans to understand, but are challenging for a computer. Thankfully, a computer making business decisions is not faced with such a general task as the Turing Test. But if we are serious about having a computer as a full member of a company board, what are the hurdles that need to be addressed? Here is a (almost certainly not complete) list.

1. Access to LOTS of data: An automated approach to decision-making will require the use of big data. Company reports and accounts, economic data such as share prices, interest rates and exchange rates, and government statistics such as employment rates and house prices would all be obvious inputs. More subjective data such as newspapers, social media feeds and blogs might also be useful. Peer-reviewed scientific papers might also provide insight. Of course as always, the challenge with big data is to process the large quantities of data that will be be of different types (figures, text, charts), stored in different ways, and have missing elements.

2. Cost: Much of the data required is likely to generate significant costs. Social media feeds may be free (but not always), but stock market information, company accounts, government data, scientific papers and so on are generally commercial products that must be paid for. In addition, there is the cost of developing and maintaining the system. The algorithm is likely to require continual development by highly skilled analysts and programmers.

3. Complexity: Big data algorithms will be central to the boardroom decision support algorithm, but they will be underpinned by advanced analytics, many of which we are only just starting to understand and develop. To have a real impact there is likely to be some research required which would require staff with the relevant skills.

So, are we really at a point where a computer could take its place on the board? Technically it’s possible but the costs to develop and maintain, as well as subscribe to the data that is required, probably means that it is not within the reach of most companies and I suspect that the money would be better spent on a human decision maker – at least for now.

Why it is so hard to predict where and when earthquakes will strike

There is currently no technique that could have helped Nepal predict when the recent earthquake would strike. AP/PA/Niranjan Shrestha

Can earthquakes ever be predicted? This question is timely after the magnitude 7.8 earthquake that struck Nepal recently. If authorities had more warning that the earthquake was coming, they may have been able to save more lives.

While Nepal is a documented area of previous seismic activity, at the moment there is no technique that provides predictions of sufficient clarity to allow for evacuations at short notice. So if we cannot predict these events now, are there avenues of research to provide useful predictions in the future?

The key word here is “useful”. It is possible to make long-term forecasts about future earthquake activity, partly by using the past record of earthquakes as a guide. There is no reason to believe that a region of the Earth is going to behave differently in the next few thousands of years from its pattern over the same range back in time. In the short term, seismologists can draw on data from recording stations, with records going back roughly 40 years on a global scale.

Within hours of a major earthquake there are estimates of its epicentre, magnitude (the amount of energy released), the depth at which it originated, the orientation of the geological fault that caused it and the direction in which it moved. The event in Nepal was a thrust fault, meaning that the upper part of the Earth was shortened by a few metres, with the rock lying above the fault plane moving southwards over the rock lying beneath it.

Gathering the data

Information about past earthquakes comes from a number of sources, not least historical records. But such records are incomplete, even in earthquake-prone countries with long traditions of documenting natural disasters, such as China and Iran. Other lines of evidence are available, including measuring and dating the offsets (movements caused by earthquakes) of man-made or natural features that can be accurately dated, such as the walls of a castle or a city. Faults cutting the Great Wall of China have been documented in this way.

Seismologists also dig trenches across faults known or suspected to be active, and can recover rocks and sediments affected by earthquakes. These events can dated, for example by radiocarbon analysis of plant remains disturbed by the faulting.

Seismologists can assess earthquakes by measuring how much they move geological features. flickr/US Geological Survey, CC BY

By combining the earthquake ages with the size of the damaged areas, it is possible to understand earthquake patterns over hundreds or even thousands of years. Scientists use this information as a guideline for future behaviour, but it is clear that the faults do not slip after the same period of time between earthquakes (the recurrence interval).

Nor does a fault necessarily rupture in the same place in successive earthquakes. An earthquake releasing stress along one fault segment may place more stress on an adjacent region, thereby increasing the earthquake likelihood in that area. This may occur soon after the original event, which explains the phenomenon of aftershocks. Nepal has already seen aftershocks of a magnitude greater than six, and is likely to see more.

Global hotspots

Instrumental and historical records combine to make a global picture of earthquake activity. There are, unfortunately, many danger areas. Eurasia bears the brunt, because of the collision of the Indian and Arabian plates with the rest of Eurasia. Therefore China, Iran, Pakistan and India all share Nepal’s susceptibility to large earthquakes. Other danger areas lie along the margins of the Pacific and Indian oceans, where one plate slides under another in a process called subduction. Earthquakes at such plate boundaries can cause devastating tsunamis, like in Japan in 2011.

Areas where tectonic plates slide under one another are earthquake hotspots.

Newer lines of research include precise measurements of the movement of a fault during earthquakes and the motion of the Earth’s surface between earthquakes. Across the Himalayas there is around 20mm of convergence (shortening) every year, roughly half of the overall convergence between the Indian and Eurasian plates. The remainder is accommodated further north, in ranges such as the Tian Shan and the Tibetan Plateau. In other words, every year a person in Siberia becomes roughly 40 mm closer to a person in central India, as the Earth’s crust deforms across the broad region between them.

This strain builds up over time and is released in an earthquake like the snapping of an elastic band. Faster strain, longer faults and greater strength in the upper part of the Earth in a particular region can all lead to larger earthquakes. The Himalayas feature a deadly combination of these factors, leading to very large events of the kind experienced on April 25.

It is not sensible to be naively optimistic about improvements in earthquake prediction, but all research on the past and present behaviour of active faults is to be welcomed. It is timely that the UK’s Natural Environment Research Council has just announced funding for research into earthquakes and resilience to earthquakes.

How we identified weird and wonderful 'Jurassic platypus' dinosaur

Calm down, I'm a vegetarian. Gabriel Lio, Author provided

When the platypus was discovered in very late 18th century, its bizarre features that appeared to be a mash-up of other animals perplexed naturalists. Now a creature from the past that would have looked like strange mix of unrelated dinosaurs has been discovered. And our research suggests that it belonged to a hitherto unknown lineage of herbivores that lived around 145m years ago, in the Jurassic period.

I was part of the international team that identified this strange creature by analysing bones enclosed in ancient rocks. Our research, published in the journal Nature, reveals that the Chilesauraus was relatively small – a fully grown adult would have measured about 3.2 metres. We discovered this by investigating four whole skeletons and several other bones – a task that was not particularly difficult as the bones were well preserved. In fact, only a few skull bones and the end of the tail remain undiscovered.

Chileosaurus' teeth suggest it was a vegetarian. Fernando Novas, Author provided

The creature had leaf-shaped teeth, which means it was most likely a plant eater. Other signs were the robust legs, which resemble those of other herbivorous dinosaur groups, and the morphology of the pelvis that allowed to increase the gut capacity for processing plant material. Chilesaurus was the most common species of the braided river system in which it lived alongside with primitive crocodiles and large long-necked dinosaurs.

A genealogical puzzle

Identifying what the dinosaur looked like was not the most challenging of the research, but it was very difficult to figure out which dinosaur group it belonged to – an issue we spent many late nights discussing. We were completely astonished by the fact that each part of the skeleton that was cleaned out from the surrounding rock resembled a different group of dinosaurs.

The well-preserved skeleton Gabriel Lio, Author provided

Its skull and neck look like those of primitive long-necked dinosaurs like Plateosaurus; the vertebrae resemble those of primitive meat-eating theropods such as Dilophosaurus; the pelvis is very similar to that of ornithischian dinosaurs such as Iguanodon; and the hand has only two well-developed fingers as in Tyranosaurus Rex, but with a longer arm.

However, there is no possibility that Chilesaurus is simply made up of different dinosaur bones, because we found four partial skeletons. Working partly in Buenos Aires, Argentina, and partly in Birmingham, our team compared the bones to those of other dinosaur groups. Eventually we decided through different analyses that Chilesaurus belongs to a completely unknown lineage of dinosaurs that acquired herbivore habits from carnivorous ancestors. Chilesaurus is the first herbivorous theropod (a lineage that includes mainly predatory dinosaurs) from the southern hemisphere.

We believe that the new dinosaur is a primitive tetanuran – a group of theropods that includes Megalosaurus, Allosaurus, Tyrannosaurus and birds – but not Carnotaurus and other early dinosaurs.

The first bones were found by geologist Manuel Suarez and his seven-year old son. The study took four years and the analyses were conducted during the second half of last year.

A Chilesaurus of our times

Who are you calling weird? daniel.baker/flickr, CC BY-ND

A bizarre combination of features like that seen in Chilesaurus can also be seen in living animal species, such as the platypus, which is a mix of duck, beaver and otter. Some naturalists even considered it a hoax. But animals such as Chilesaurus and the platypus can be explained by an evolutionary process called convergence evolution, in which two unrelated species or groups acquire similar characteristics because of living in similar environments or having a similar behaviour.

Similarly, the bizarre anatomy of Chilesaurus will probably open a heated discussion about its relationships. Ultimately, the discovery reveals how much data is still completely unknown about dinosaurs and that there is still much waiting to be discovered in the rocks that tell the story of our planet in deep time.

Telescopes on the ground may be cheaper, but Hubble shows why they are not enough

Bye, Earth telescopes! You will never reach my level. ESA, CC BY-SA

Observatories on Earth are cheaper than telescopes in space. They are also improving rapidly – when the European-Extremely Large Telescope starts its observations in nine years, it will be able to provide images 16 times sharper than those taken by the Hubble space telescope. But while it may seem hard to justify investment in space telescopes, the ground-breaking discoveries made by Hubble have taught us just how valuable they are.

Hubble, which was the world’s first space-based optical observatory, has made amazing discoveries in all aspects of astronomy, from flashes of aurora on planets and moons in our solar system to the evolution of galaxies billions of light years away.

Observations by Hubble helped determine the rate of expansion of the universe in a Nobel prize-winning study. We have witnessed stars being born in nurseries like the Eagle nebula and exploding as supernovae. Hubble has also captured a powerful jet emerging from a black hole at the centre of another galaxy.

Picture of the globular cluster Messier 2, taken by Hubble. ESA/Hubble & NASA, CC BY

These discoveries come at a price. The Hubble mission cost $1.5 billion at its launch in 1990 and the maintenance costs have also been sky-high. The eagerly-anticipated first pictures taken by Hubble were disappointingly blurry. The 2.4 m diameter mirror inside the telescope was slightly flawed so the light was not focusing correctly. Installation of an optics system to correct this problem was the target of the first Hubble servicing mission, carried out by space shuttle astronauts over five days of spacewalks in 1993. Four further servicing missions were carried out from 1997 to 2009 to upgrade and replace scientific instruments, power and guidance systems, and each mission had associated risks and expense. Since the end of NASA’s Space Shuttle programme there has been no way to carry out further servicing.

Space telescopes are not getting any cheaper. The successor to Hubble, the James Webb telescope, has been plagued by a number of delays and rising costs. As it prepares for launch in 2018, it will have cost about $8bn to build, launch and commission.

Earth v space

One significant advantage of building on the ground is that the size of the telescopes can be much larger than can be carried into space. Telescopes on our own planet have also made amazing discoveries, such as the Gemini telescope observing Jupiter’s two giant red spots brushing past one another in the planet’s southern hemisphere. The Keck observatory has detected water vapour in the atmosphere of a planet orbiting another star. The European Southern Observatory telescopes tracked stars orbiting the black hole at the centre of our galaxy to understand the formation of the stars and their interaction with the black hole.

However, ground-based telescopes aren’t cheap either. Work has already begun on the European Extremely Large Telescope, sited in Chile’s Atacama desert, with a cost estimated to be over €1 billion and with annual operating costs of €50m. But this is still less than Hubble and James Webb.

Artist’s impression of the European Extremely Large Telescope European Southern Observatory/flickr, CC BY-SA

When E-ELT observations start in 2024, the state-of-the-art correction for atmospheric distortion will allow it to provide images 16 times sharper than those taken by Hubble. With technological advancements like this it may seem hard to justify the expense and risk of future space-based telescopes.

However, the simple fact is that if we choose to only observe from the ground we will make ourselves blind to a wide variety of astronomical phenomena and potential discoveries. These include some of the universe’s most energetic events, such as gamma ray bursts.

The main reason for this is that the atmosphere of our planet does not hold back space telescopes. While the atmosphere lets through visible light, to which our eyes are sensitive, it absorbs light at some other wavelengths so we can never see it from the ground. In addition, turbulent motion in the atmosphere blurs the light travelling through it, causing objects to twinkle and appear fuzzy. Another problem with ground-based telescopes is that they are subject to local weather conditions, and high clouds can ruin the chance of making any useful observations.

The Very Large Telescope in Chile is about to get competition from the E-ELT. ESO/G. Lombardi (glphoto.it), CC BY-SA

From its vantage point above the atmosphere, Hubble avoids these effects and can produce high-resolution images over a broad spectrum. The scientific value of these observations is evident in that applications by scientists for observing time on Hubble last year were oversubscribed by a factor of five. It has also been an important source of scientific papers. According to a survey by the European Southern Observatory last year, Hubble has produced between 650 and 850 papers per year since 2005 – which is far more than any of ESO’s ground-based telescopes.

Complementary contributions

The investment in astronomical telescopes, whether in space or on the ground, has to be justified by the scientific return – and in selecting new facilities it is fundamentally the science which drives the decision. Having worked with telescopes both on the ground and in space, I feel that science ultimately needs both. But in a world of limited funds we can’t have it all. International co-operation is therefore the key, whether it is about placing a new telescope in another country or providing an instrument for a mission led by another space agency.

The value of the observations made by telescopes based both on the ground and in space can be measured not just by the scientific results in understanding the near and far universe, but also in the inspiration that these images and discoveries provide.