Small sats are vital to Australia’s space industry – and they won’t be space junk



File 20180514 178746 19xb9y.jpg?ixlib=rb 1.1
Small satellites are launched to Low Earth Orbit – and then eventually burn up.
from www.shutterstock.com

Michael Smart, The University of Queensland

Today the federal government released its response to the review of Australia’s Space Capability.

Among the details regarding the establishment of Australia’s first space agency, and a national space industry strategy, it is clear that small satellites will have a place in our space future.

The following recommendations were marked as “supported” or “supported in principle”:

  • Australia should […] take advantage of the global space technology paradigm
    shift towards constellations of miniaturised spacecraft for communications and Earth observations

  • […] the Agency [should facilitate] regulatory approval processes for small satellite launch facilities in Australia and the launch of Australian satellites overseas.

But won’t all these new satellites just make the current space junk problem even worse?

Luckily, the answer is no. And it’s due to the satellite “self-cleaning zone” that surrounds Earth.




Read more:
Trash or treasure? A lot of space debris is junk, but some is precious heritage


How satellites stay in orbit

For a satellite to remain in orbit around Earth, it must have a velocity of at least 7.9km per second, and must not drop below approximately 200km altitude in any part of its orbit.

If its velocity or its orbit is too low, it will be drawn back to Earth by a combination of gravity and atmospheric drag.

Another key aspect of a satellite’s orbit is its inclination relative to the Equator. Equatorial orbits – when the orbit is around the Equator – have zero inclination. Polar orbits, on the other hand, pass over both the north and south poles, and have an inclination of 90 degrees.

Other orbits sit at inclinations between 0° and 90°. The orbit of the international space station, for example, has an inclination of 51.6°. So it passes over the parts of Earth that are within 51.6° of latitude north and south of the Equator. Its orbit has an average altitude of 400km. (For comparison, the radius of the Earth is 6,378 km.)

The orbit of the International Space Station.

Low orbits for small satellites

Until about the year 2000 almost all useful satellites (ones that performed functions such as communications or weather observation) were big – weighing as much as 10,000kg. They also tended to be in orbits with altitudes greater than 2,000km.

This has changed due to the rapid development of micro-scale, low-power electronics that we all use every day in our mobile phones. Satellites can now weigh just hundreds of kilograms and perform the same function in terms of communications and earth observation.

There is also a movement (including in Australia) towards even smaller satellites called “cubesats”, weighing less than 20kg, which have limited capability and life. One implication of this smaller size is the need to be close to Earth.

Modern small satellites are all in Low Earth Orbit, with altitudes less than 1,000km. For example, a company called Planet has a constellation of about 200 satellites which supply images of almost anywhere on the planet on a daily basis.

Polar (blue) and inclined (red) orbits around Earth.

The self-cleaning zone

Despite the fact that the edge of Earth’s atmosphere is generally considered to be at 100km altitude, in reality it reaches much higher. In practice, any satellite in Low Earth Orbit will eventually be slowed down by impacts with air molecules and will return to Earth in a fiery re-entry. This may seem like a significant limitation for small satellites. But actually it is extremely helpful.

Due in part to their size limitation, most small satellite have a useful life of between one and five years. After this time a replacement satellite with the latest technology must be launched. If it wasn’t for the fact that Low Earth Orbit is a self-cleaning zone, the small satellite revolution would clog up the space around us with junk.

So when you hear about another planned constellation of hundreds of satellites, don’t worry too much. So long as they are in Low Earth Orbit, and most likely they will be, the Earth’s “vacuum cleaner” will clean up after us.

But what about the International Space Station? It is also in the Low Earth Orbit zone – so its orbit needs to be continuously maintained, which requires significant reserves of fuel. At some point, however, it will suffer the same fate as the much smaller Chinese space station Tiangong-1 and make a fiery re-entry.


The Conversation


Read more:
China’s falling space station highlights the problem of space junk crashing to Earth


Michael Smart, Professor of Hypersonic Aerodynamics, The University of Queensland

This article was originally published on The Conversation. Read the original article.

China’s falling space station highlights the problem of space junk crashing to Earth



File 20180322 54875 7h0mw5.png?ixlib=rb 1.1
China’s Tiangong-1 space station is due to hit Earth, and Australia is in the crash landing zone.
Cindy Zhi/The Conversation, CC BY-ND

Brad E Tucker, Australian National University

Any day now, the Chinese space station Tiangong-1 is expected to fall back to Earth – but it’s uncertain where it will crash land. We know that Australia is in the potential zone, and we have been hit before by a falling space station.

But Tiangong-1 is just one of many pieces of space junk left orbiting our Earth.

The United Nations Office for Outer Space Affairs (UNOOSA) says more than 8,000 objects have been launched in to space, with 4,788 currently still in orbit around the Earth.




Read more:
60 years in orbit for ‘grapefruit satellite’ – the oldest human object in space


With every launch, even more space junk is produced ranging from the rocket boosters, to flakes of paint and the satellites themselves. In 2009 an old communication satellite crashed into a new one, creating thousands of pieces of smaller debris.

By some estimates, the amount of space junk is in the hundreds-of-thousands to millions of pieces and this interactive illustration shows some of them.

An illustration of some of the space junk left orbiting Earth.
ESA/ID&Sense/ONiRiXEL, CC BY-SA

From a heavenly place

Tiangong-1, or “Heavenly Palace”, was China’s first space station – a small version of the International Space Station – and was launched in September 2011. Weighing a bit more than 8 tonnes, about 10 metres long and 3 metres in diameter, it was the first of three planned space stations.

An illustration comparing the Tiangong-1 with a US school bus.
Aerospace Corporation

After delays in Tiangong-2, the Tiangong-2 and Tiangong-3 were merged and Tiangong-3 was launched in 2016. Tiangong-1 has subsequently not been in use and was always designed to come down back to Earth.

But where will it crash land?

A drop in the ocean

Halfway between New Zealand and South America in the Pacific Ocean is one of the most un-inhabited places on the Earth. This is the ideal location to have large pieces come back down, as the risk to lifeforms is minimal.

While most of these objects will break up into smaller bits, choosing a remote location then further minimises the risk of these bits.

In this part of an ocean there are literally hundreds of parts of automated space vehicles, rocket boosters, and even the Russian Space Station Mir, which splashed down east of Fiji in March 2001.

When you look at maps of satellite and space junk re-entry, the majority go straight over Australia and New Zealand. That is because re-entry starts roughly between 80km and 100km above the ground, takes around 15 to 20 minutes, and creates debris footprints hundreds-to-thousands of kilometers wide.

Therefore in order to hit the target of the southern Pacific Ocean, it must start over Australia and New Zealand.

But there’s one important feature that makes Tiangong-1 different in all of this: it is out of control, according to China’s space agency.

Crashed in Australia

If you were around in 1979 and happened to be in Western Australia, you might have a unique souvenir – part of the NASA space station Skylab, which re-entered near the southern town of Esperance.

An overhead view of the Skylab space station.
NASA

While most missions now plan on re-entry, this was not always the case and Skylab did not have a good plan for coming back to the Earth. It was designed for a nine-year lifetime, but no clear manoeuvrability was built to re-enter at a specific point.

As news came out that it was going to re-enter, and it was not clear where, there was a varied response. Some people staged Skylab parties, others operated safety measures (such as air raid siren preparedness in Brussels).

After it hit WA, the local Shire of Esperance issued NASA with a cheeky A$400 littering fine for scattering debris across its region. It was eventually paid in 2003 – not by NASA, but by a US radio presenter and his listeners who raised the funds.

NASA fined for littering when Skylab fell near Esperance, WA.
Flickr/Amanda Slater, CC BY-SA

So in 2016 when China notified UNOOSA that Tiangong-1 was uncontrolled in its point of re-entry, this made scientists pay attention. Of course this made the public and media take notice, causing a bit of a panic in some coverage.

Don’t panic!

Every day, hundreds of tons of debris, both human and natural (i.e. meteors), hit the Earth. Even those that survive re-entry and land pose a minute risk. Keep in mind, most of the Earth is unpopulated – from the oceans to vast deserts and land, nearly all people are safe.

The total surface are of the Earth is over 500 million square-kilometres. Even if a piece of space junk leaves a 1,000 square-kilometre debris field, that is only 0.0002% of the Earth’s surface.

A graphic showing how Tiangong-1 could break up as it crashes back to Earth, but where will it crash?
Aerospace Corporation

In fact, the Aerospace Corporation has calculated the odds of getting hit by Tiangong-1 parts at 1 million times LESS than winning the lotto.

Map showing the area between 42.8 degrees North and 42.8 degrees South latitude (in green), over which Tiangong-1 could reenter. You are many more times likely to win the lotto then getting hit by a piece of space debris from it.
ESA, CC BY-SA

Now that you know you don’t have to worry, if you do end up being in a path that can see re-entry, you will see a show not unlike in the 2013 movie Gravity.

SPOILER ALERT: Don’t watch if you don’t know the ending of Gravity.

What are we doing about it

Of course the question has to be asked – what are we doing to both solve the junk already in space and prevent more? Well, lots actually.

A large source of space junk is all the rocket boosters and engines that are still up there and can be seen re-entering. If you remember the excitement in February around the Space X Falcon 9 Heavy launch, one of the huge reasons for excitement was that those rockets come back down safely, making them re-usable and not another piece of space junk.




Read more:
Australia’s back in the satellite business with a new launch


Making satellites smaller not only means they are cheaper and quicker to build, but at the end of their life they can break up even more in the atmosphere, eliminating the possibility of large pieces surviving and landing.

And for all those small bits out there, Electro-Optic Systems (EOS) and Mount Stromlo Observatory are part of the Space Environment Research Centre (SERC) which is planning to build a laser system capable of safely de-orbiting small bits of space junk

The ConversationSo don’t worry about Tiangong-1 or other space junk hitting you, we’re on it.

Brad E Tucker, Astrophysicist, Australian National University

This article was originally published on The Conversation. Read the original article.

Trash or treasure? A lot of space debris is junk, but some is precious heritage



File 20170919 32071 1a2xfcz
The Telstar 1 satellite inspired a chart-topping pop tune, the iconic black-and-white hexagonal Adidas soccer ball, and maybe even a Doctor Who creature, the Mecanoids.
National Physical Laboratory

Alice Gorman, Flinders University

Most of us will never have the opportunity to travel into space. But we can feel connected to it in other ways.

Above us right now, and every day, are extraordinary old satellites from the 1950s and 1960s, orbiting at speeds of 7-8 kilometres per second.

They’re part of our space heritage.

Deciding which parts of this heritage should stay, and which should be on a “hit list” for removal, is the tricky bit.


Listen: Speaking with: Canadian astronaut Chris Hadfield


Cultural heritage is defined as “things from the past and present, worth preserving for present and future generations”.

In recent decades there has been a movement to recognise the heritage of the modern world, including the Cold War, aviation, mass manufacturing, computing, and space exploration.

This includes space junk in Earth orbit.

This first day cover shows the Syncom 2 and 3 satellites, used to televise the 1964 Tokyo Olympic Games. They also provided telecommunications in the Vietnam War.
Image courtesy of Don Hillger and Garry Toth, University of Colorado,

Orbiting heritage

Space junk is the archaeological record of the Space Age, in which everyday life on Earth has come to depend on satellite services such as telecommunications.

The junk includes spacecraft with high levels of cultural significance, such as:

  • Vanguard 1, the oldest human object in orbit
  • Telstar 1, the first active telecommunications satellite
  • Syncom 3, the first geostationary satellite, and
  • NigComSat 1, Nigeria’s first telecommunications satellite.
The Vanguard Adrift Twitter account is part of Project Adrift, a multimedia art work based on space junk.
ProjectAdrift

In the future, these spacecraft may be the targets of orbital debris clean-up.

We do have to get rid of some of this stuff before Earth orbit becomes too dangerous. But heritage values should be considered in any proposal to actively remove space junk. The location of these spacecraft in orbit is part of their cultural significance, and many are low collision risks.


Read more: ‘Jewelled’ LAGEOS satellites help us to measure the Earth


How do we make sure that significant cultural heritage in orbit isn’t lost, without exacerbating the debris problem?

Methods used on Earth include heritage listing, cultural heritage management plans, and mitigation strategies. These can also be applied in space – but some adaptations are necessary.

The problem with heritage lists

Numerous space places on Earth – like rocket launch sites and satellite tracking antenna – have been heritage listed under national or state heritage legislation.

The Casshorn antenna is part of the heritage-listed OTC Earth Station at Carnarvon, Western Australia.
OTC/Colin Mackellar

However, nations can’t place their orbital heritage on a national heritage register, even though they legally own it. The Outer Space Treaty (OTS) states that space is the “province of all mankind” [sic]. Applying heritage legislation could be interpreted as extending a national jurisdiction into space, and thus making a territorial claim in contravention of this principle.


Read more: The outer space treaty needs adaptation


The UNESCO World Heritage List can’t be used to safeguard orbital heritage either, even for spacecraft which have “outstanding universal value”.

The World Heritage Convention does not cover “moveable” objects like our high-speed space junk. And despite its name, the World Heritage List is dependent on nations nominating properties: it is rooted in the nation-state.

Working with what we’ve got

The answer may be to turn to Non-Governmental Organisations (NGOs) or other international organisations, which can’t assert national interests in space. The Inter-Agency Space Debris Co-ordination Committee, with 13 member space agencies from across the world, could play a lead role in managing research and processes.

But why not adapt an existing list? While not providing legal protection, these lists do lend “moral weight”. For example, the American Institute of Aeronautics and Astronautics maintains a Historic Aerospace Sites list, which includes Tranquility Base on the Moon.

The United Nations Office of Outer Space Affairs has a register of all objects launched into space, the European Space Agency keeps the DISCOS database of space debris, and the International Council on Monuments and Sites could provide expert heritage advice.

The most dangerous satellite in orbit

We could also do it in reverse. A number of satellites consistently appear on hit-lists for urgent removal. Among them are Midori-2, Metop-A, Metop-B, COBE and the number one risk, Envisat.

Launched in 2002 for Earth observation, Envisat is one the largest spacecraft in orbit. Contact was lost in 2012, but it is likely to remain in orbit for another 150 years.

Artist’s impression of Envisat.
ESA

Some predict that collisions with Envisat could generate enough debris to trigger the self-sustaining cascade of collisions dubbed the Kessler Syndrome. For Envisat, cultural significance is never going to outweigh the risks.

A Cultural Heritage Management Plan for the satellite would start with a significance assessment. Ideally, the satellite would be fully recorded before its de-orbit, so that this documentation could be used for further research. However, this is not feasible at present.


Read more: Powerful and ignored: the history of the electric drill in Australia


Instead, we could propose an offset. The idea is that a loss in one area is “offset” by preserving or investing in an area of equivalent environmental or heritage value.

A heritage offset may involve an effort to gather and curate associated documentation on Earth; to collect oral histories about the satellite; and to locate components, models, prototypes, or fragments which survive re-entry. This ensures that maximum information about Envisat remains for those studying 21st century human activities in orbit.

The common heritage of humanity

Heritage isn’t an optional extra in space. It helps preserve the cultural diversity of humankind, as recommended in the 1977 UNESCO Declaration on the Responsibilities of Present Generations towards Future Generations.

Recognising the orbital heritage of countries or groups usually marginalised in space exploration fosters an inclusive approach to space.

Heritage allows us to explore relevant principles for international agreements on mitigating orbital debris, which are progressing far too slowly given the urgency of the problem.

But most importantly, protecting culturally significant spacecraft enables people on Earth to feel connected to space as the common heritage of humanity.


The ConversationThis article is based on a paper presented at the 68th International Astronautical Congress taking place this week in Adelaide, South Australia.

Alice Gorman, Senior Lecturer in archaeology and space studies, Flinders University

This article was originally published on The Conversation. Read the original article.