Brexit Biting for UK Space Industry

Artist's rendition of a satellite - mechanik/123RF Stock Photo

Artist’s rendition of a satellite – mechanik/123RF Stock Photo

UK companies involved in European Commission space programmes face an uncertain future according to media reports over the last week. The Financial Times reported that the European Commission wanted two key clauses in the contracts for work on the next part of the €10 bn Galileo Satellite Navigation System. These would allow the Commission to:

  • Cancel the contracts, without penalty, of any supplier who is no longer based in an European Union (EU) member state; and then
  • Charge that supplier all costs associated with finding their replacements.

Clearly, this poses a huge risk to UK companies given the fact that the UK has indicated its intention to leave the EU in 2019 by triggering Article 50. We wrote about the potential impacts of Brexit last year, and whilst we did pick up concerns over Galileo we didn’t see this coming!

Should the UK Space Industry be concerned?
Yes!

Despite reports to the contrary, this does not mean we are leaving the European Space Agency (ESA). We are very much remaining part of ESA, something that was confirmed at the ministerial in December. This solely relates to programmes owned, and funded, by the European Union (EU). However, it is concerning for two key reasons:

  • Anyone who has tried to negotiate contract terms with large governmental organisations will be aware that it tends to be a binary take it or leave it scenario. Therefore, if these clauses are in the contract, then it is highly likely companies will have to sign up to them to get the work.
  • It may not just be Galileo, the Copernicus Programme could be next. Copernicus is also an EU programme, and therefore it has to be a possibility that they may apply the same clauses to future Copernicus tenders. Galileo isn’t something Pixalytics is involved with, but if this was extended to Copernicus we’d be potentially impacted and would need to make choices.

What Can UK Companies Do?
The options are limited:

  • Bid anyway! Accept the potential financial risk, or hope that it will get resolved within the various Brexit negotiations. Given the size of these contracts, it will be a brave CEO who goes down this route.
  • Not bidding for any Galileo contract is probably the financially prudent option, but equally it removes a significant revenue stream.
  • Move to another European Country. I think there will be a number of companies who will be looking at moving some, or all, of their operations to another EU member state.

Any Causes For Optimism?
Not really, but there are tiny strands of hope.

  • Security – A key issue with Galileo is security. Currently, all EU members have agreements on security and when the UK leaves the EU, it leaves that agreement. Of course, security is just one of hundreds of agreements the UK will be hoping to discuss with the EU through Brexit negations. If security agreements are reached with the UK, maybe the position will change.
  • UK Election – Whilst writing this blog, the UK Prime Minister has announced a General Election in June. Parliamentary changes may influence the type of Brexit we have, but again it is highly unlikely.

It was fairly obvious, despite the contrary political rhetoric, that Brexit would have huge consequences on the UK’s relationship with Europe.

The UK’s space industry looks as though it will be at the forefront of those consequences. Forget 2019, the bite of Brexit is being felt today!

Remote Sensing Goes Cold

Average thickness of Arctic sea ice in spring as measured by CryoSat between 2010 and 2015. Image courtesy of ESA/CPOM

Remote sensing over the Polar Regions has poked its head above the ice recently.

On the 8th February The Cryosphere, a journal of the European Geosciences Union, published a paper by Smith et al titled ’Connected sub glacial lake drainage beneath Thwaites Glacier, West Antarctica’. It described how researchers used data from ESA’s CryoSat-2 satellite to look at lakes beneath a glacier.

This work is interesting from a remote sensing viewpoint as it is a repurposing of Cryosat-2’s mission. It’s main purpose is to measure the thickness of the ice sheets and marine ice cover using its Synthetic Aperture Radar (SAR)/Interferometric Radar Altimeter, known as SIRAL, and it can detect millimetre changes in the elevation of both ice-sheets and sea-ice.

The team were able to use this data to determine that the ice of the glacier had subsided by several metres as water had drained away from four lakes underneath. Whilst the whole process took place between June 2012 and January 2014, the majority of the drainage happened in a six month period. During this time it’s estimated that peak drainage was around 240 cubic metre per second, which is four times faster than the outflow of the River Thames into the North Sea.

We’ve previously highlighted that repurposing data – using data for more purposes than originally intended – is going to be one of the key future innovation trends for Earth Observation.

Last week, ESA also described how Sentinel-1 and Sentinel-2 data have been used over the last five months to monitor a crack in the ice near to the Halley VI research base of the British Antarctic Survey (BAS). The crack, known as Halloween Crack, is located on the Brunt ice Shelf in the Wedell Sea sector of Antarctica and was identified last October. The crack grew around 600 m per day during November and December, although it has since slowed to only one third of that daily growth.

Since last November Sentinel-2 has been acquiring optical images at each overflight, and this has been combined with SAR data from the two Sentinel-1 satellites. This SAR data will be critical during the Antarctic winter when there are only a few hours of daylight and a couple of weeks around mid-June when the sun does not rise.

This work hit the headlines as BAS decided to evacuate their base for the winter, due to the potential threat. The Halley VI base, which was only 17km from the crack, is the first Antarctic research station to be specifically designed to allow relocation to cope with this sort of movement in the ice shelf. It was already planned to move the base 23 km further inland, and this was successfully completed on the 2nd February. Further movement will depend on how the Halloween Crack develops over the winter.

Finally, the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) project was announced this week at the annual meeting of the American Association for the Advancement of Science. Professor Markus Rex outlined the project, which will sail a research vessel into the Arctic sea ice and let it get stuck so it can drift across the North Pole. The vessel will be filled with a variety of remote sensing in-situ instruments, and will aim to collect data on how the climate is changing in this part of the world through measuring the atmosphere-ice-ocean system.

These projects show that the Polar Regions have a lot of interest, and variety, for remote sensing.

Supporting Chimpanzee Conservation from Space

Gombe National Park, Tanzania. Acquired by Sentinel-2 in December 2016. Image courtesy of ESA.

Being able to visualise the changing face of the planet over time is one of the greatest strengths of satellite remote sensing. Our previous blog showed how Dubai’s coastline has evolved over a decade, and last week NASA described interesting work they’re doing on monitoring habitat loss for chimpanzees in conjunction with the Jane Goodall Institute.

Jane Goodall has spent over fifty years working to protect and conserve chimpanzees from the Gombe National Park in Tanzania, and formed the Jane Goodall Institute in 1977. The Institute works with local communities to provide sustainable conservation programmes.

A hundred years ago more than one million chimpanzees lived in Africa, today the World Wildlife Fund estimate the population may only be around 150,000 to 250,000. The decline is stark. For example, the Ivory Coast populations have declined by 90% within the last twenty years.

One of the key factors contributing to this decline is habitat loss, mostly through deforestation; although other factors such as hunting, disease and illegal capture also contributed.

Forests cover around 31% of the planet, and deforestation occurs when trees are removed and the land has another use instead of being a forest. In chimpanzee habitats, the deforestation is mostly due to logging, mining and drilling for oil. This change in land use can be monitored from space using remote sensing. Satellites produce regular images which can be used to monitor changes in the natural environment, in turn giving valuable information to conservation charities and other organisations.

In 2000 Lilian Pintea, from the Jane Goodall Institute, was shown Landsat images comparing the area around the Gombe National Park in 1972 and 1999. The latter image showed huge deforestation outside the park’s boundary. The Institute have continued to use Landsat imagery to monitor what is happening around the National Park. In 2009 they began a citizen science project with local communities giving them smartphones to report their observations. Combining these with ongoing satellite data from NASA has helped develop and implement local plans for land use and protection of the forests. Further visualisation of this work can be found here. The image at the top was acquired Sentinel-2 in December 2016 and shows the Gombe National Park, although it is under a little haze.

The satellite data supplied by NASA comes from the Landsat missions, which currently have an archive of almost forty-five years of satellite data, which is freely available to anyone. We also used Landsat for data in our Dubai animation last week. Landsat captures optical data, which means it operates in a similar manner to the human eye – although the instruments also have infrared capabilities. However, one drawback of optical instruments is that they cannot see through clouds. Therefore, whilst Landsat is great for monitoring land use when there are clear skies, it can be combined with synthetic aperture radar (SAR), from the microwave spectrum, as it can see through both clouds and smoke. This combination enables land use and land change to monitored anywhere in the world. Using the freely available Landsat and Sentinel-1 SAR data you could monitor what is happening to the forests in your neighbourhoods.

Satellite data is powerful tool for monitoring changes in the environment, and with the archive of data available offers a unique opportunity to see what has happened over the last four decades.

Earth Observation Looking Good in 2017!

Artist's rendition of a satellite - paulfleet/123RF Stock Photo

Artist’s rendition of a satellite – paulfleet/123RF Stock Photo

2017 is looking like an exciting one for Earth Observation (EO), judging by the number of significant satellites planned for launch this year.

We thought it would be interesting to give an overview of some of the key EO launches we’ve got to look forward to in the next twelve months.

The European Space Agency (ESA) has planned launches of:

  • Sentinel-2B in March, Sentinel-5p in June and Sentinel-3B in August – all of which we discussed last week.
  • ADM-Aeolus satellite is intended to be launched by the end of the year carrying an Atmospheric Laser Doppler Instrument. This is essentially a lidar instrument which will provide global measurements of wind profiles from ground up to the stratosphere with 0.5 to 2 km vertical resolution.

From the US, both NASA and NOAA have important satellite launches:

  • NASA’s Ionospheric Connection Explorer (ICON) Mission is planned for June, and will provide observations of Earth’s ionosphere and thermosphere; exploring the boundary between Earth and space.
  • NASA’s ICESat-2 in November that will measure ice sheet elevation, ice sheet thickness changes and the Earth’s vegetation biomass.
  • In June NOAA will be launching the first of its Joint Polar Satellite System (JPSS) missions, a series of next-generation polar-orbiting weather observatories.
  • Gravity Recovery And Climate Experiment – Follow-On (GRACE_FO) are a pair of twin satellites to extend measurements from the GRACE satellite, maintaining data continuity. These satellites use microwaves to measure the changes in the Earth’s gravity fields to help map changes in the oceans, ice sheets and land masses. It is planned for launch right at the end of 2017, and is a partnership between NASA and the German Research Centre for Geosciences.

Some of the other launches planned include:

  • Kanopus-V-IK is a small Russian remote sensing satellite with an infrared capability to be used for forest fire detection. It has a 5 m by 5 m spatial resolution over a 2000 km swath, and is planned to be launched next month.
  • Vegetation and Environment monitoring on a New MicroSatellite (VENµS), which is partnership between France and Israel has a planned launch of August. As its name suggests it will be monitoring ecosytems, global carbon cycles, land use and land change.
  • KhalifaSat is the third EO satellite of United Arab Emirates Institution for Advanced Science and Technology (EIAST). It is an optical satellite with a spatial resolution of 0.75 m for the visible and near infrared bands.

Finally, one of the most intriguing launches involves three satellites that form the next part of India’s CartoSat mission. These satellites will carry both high resolution multi- spectral imagers and a panchromatic camera, and the mission’s focus is cartography. It’s not these three satellites that make this launch intriguing, it is the one hundred other satellites that will accompany them!

The Indian Space Research Organisation’s Polar Satellite Launch Vehicle, PSLV-C37, will aim to launch a record 103 satellites in one go. Given that the current record for satellites launched in one go is 37, and that over the last few years we’ve only had around two hundred and twenty satellites launched in an entire year; this will be a hugely significant achievement.

So there you go. Not a fully comprehensive list, as I know there will be others, but hopefully it gives you a flavour of what to expect.

It certainly shows that the EO is not slowing down, and the amount of data available is continuing to grow. This of course gives everyone working in the industry more challenges in terms of storage and processing power – but they are good problems to have. Exciting year ahead!

Will Earth Observation’s power base shift in 2017?

Blue Marble image of the Earth taken by the crew of Apollo 17 on Dec. 7 1972. Image Credit: NASA

Blue Marble image of the Earth taken by the crew of Apollo 17 on Dec. 7 1972.
Image Credit: NASA

We’re only a few days into 2017, but this year may see the start of a seismic shift in the Earth Observation (EO) power base.

We’ve previously described how the sustainable EO industry really began this week thirty nine years ago. On 6th January 1978 NASA deactivated Landsat-1; it had already launched Landsat-2, carrying the same sensors, three years earlier and with guaranteed data continuity our industry effectively began.

Since then the USA, though the data collected by NASA and NOAA satellites, has led the EO global community. This position was cemented in 2008 when it made all Landsat data held by the United States Geological Survey (USGS) freely available, via the internet, to anyone in the world. This gave scientists three decades worth of data to start investigating how the planet had changed, and companies sprang up offering services based entirely on Landsat data. This model of making data freely available has been so transformational, that the European Union decided to follow it with its Copernicus Programme.

Landsat-1 and 2 were followed by 4, 5, 7 & 8 – sadly Landsat 6 never made its orbit – and Landsat 9 is planned for launch in 2020. The USA’s role EO leadership has never been in question, until now.

US President-elect Donald Trump and his team have already made a number of statements indicating that they intended to cut back on NASA’s Earth Science activities. There are a variety of rumours suggesting reasons for this change of approach. However, irrespective of the reason, slashing the current $2 billion Earth Science budget will have huge consequences. Whilst all of this is just conjecture at the moment, the reality will be seen after 20th January.

Against this America backdrop sits the Copernicus Programme, with the European Space Agency due to launch another three satellites this year:

  • Sentinel 2B is planned for March. This is the second of the twin constellation optical satellites offering a spatial resolution of 10 m for the visible bands. The constellation will revisit the same spot over the equator every five days, with a shorter temporal resolution for higher latitudes.
  • June is the scheduled month for the launch of the Sentinel 5 Precursor EO satellite to measure air quality, ozone, pollution and aerosols in the Earth’s atmosphere. This will be used to reduce the data gaps between Envisat, which ended in 2012, and the launch of Sentinel-5.
  • Sentinel 3B is due to launched in the middle of the year, and like 2B is the second in a twin satellite constellation. This pair is mainly focussed on the oceans and measure sea surface topography, sea and land surface temperature, and ocean and land colour. It will provide global coverage every two days with Sea and Land Surface Temperature Radiometer (SLSTR) and the Ocean and Land Colour Instrument (OLCI).

These launches will take give the Copernicus programme seven satellites collecting a wide variety of optical and radar data across the entire planet, which is then made freely available to anyone. It’s obvious to see what will fill any vacuum created by a reduction in Earth Science in the USA.

Depending on how much of the next US President’s rhetoric is turned into action, we may start to see the shift of the EO power base to Europe. Certainly going to be an interesting year ahead!

UK Government View On ESA and Space Industry

Artist's rendition of a satellite - paulfleet/123RF Stock Photo

Artist’s rendition of a satellite – paulfleet/123RF Stock Photo

This week we got a glimpse of the UK Government’s view on the space industry, with the publication of Satellites and Space: Government Response to the House of Commons Science & Technology Committee’s Third Report of Session 2016/17. The original report was published in June and contained a series of recommendations, to which the Government responded.

The timing is interesting for two reasons:

  • Firstly, it comes just before the European Space Agency (ESA) Ministerial Council taking place on Thursday and Friday this week in Lucerne. We highlighted the importance of this meeting in a recent blog.
  • Secondly, it has taken the Government five months to respond, something the Committee themselves were disappointed with.

The Government’s response has a number of insights into the future for the UK space industry. The full report can be seen here, but we wanted to pick out three things that caught our eye:

ESA
For us, and the ESA Ministerial, the most interesting comment was that the Government reaffirmed that the UK will remain a member of ESA after Brexit. It also noted that “The UK’s investment in the European Space Agency is an important part of our overall investment in space, from which we obtain excellent value.” Whilst the level of financial commitment to ESA won’t become clear until the Ministerial, the mood music seems positive.

Earth Observation
The role of the Space for Smarter Government Programme (SSGP) was highlighted, particularly in relation to helping the Department for Environment, Food and Rural Affairs use satellite data more. As part of SSGP we ran a successful Flood Mapping project during 2015/16. SSGP is running again this year, but given the importance placed on the programme on embedding space activities within Government it was disappointing not to see a further commitment beyond March 2017.

A business plan for a Government Earth Observation Service is currently being written, which is aimed at increasing the uptake of EO data within Government. We’ve not seen too much about this service yet, and will be very interested in the business plan.

Responding a question on harnessing the public interest in Tim Peake’s time in space, it was nice to see the work of the EO Detective highlighted. This is a fantastic project that raises awareness of the space industry in schools, and uses space/satellite imagery to help children explore topics such as climate change.

Small Satellites
“The Government intends to establish the UK as the European hub for low cost launch of small satellites.” It’s an interesting ambition; although it’s not completely clear what they mean by the term small satellites. As we described last week definitions are important.

On top of the three points above there were some words on funding for space related research; however these amounted to no more than an acknowledgement that various Government bodies will work together. There was also reference to the development of a new Space Growth Strategy, something we’ll talk more about in two weeks.

The Government’s response to this report was an interesting read, and whilst there are still a lot of unanswered questions it does hint at cautious optimism that they will support the space industry.

We were all on tenterhooks this week waiting the big announcements from the ESA Ministerial, and here are some of the headline outcomes:

  • Overall, ESA’s 22 member states plus Slovenia and Canada allocated €10.3 billion for space activities and programmes over the next five years. This includes an EO programme valued at €1.37 bn up until 2025.

Within this overall envelope, the UK has allocated €1.4 bn funding over five years, which equates to 13.5% of total. This includes:

  • €670.5 m for satellite technology including telecommunications, navigation and EO.
  • €376.4 m for science and space research
  • €82,4 m for the ExoMars programme.
  • €71 m for the International Space Station Programme
  • €22 m for innovate space weather missions

Our eye was, of course, drawn to the investment in EO and there is a little more detail, with the €670.5 m is:€60 m for the development of the commercial use of space data €228.8 m for environmental science applications and climate services through ESA’s EO programme, including:

  • Incubed – a new programme to help industry develop the Earth observation satellite technology for commercial markets
  • the Biomass mission to measure the carbon stored in the world’s forests
  • the Aeolus mission, measuring wind speed in three dimensions from space

Finally, it is worth noting Katherine Courtney, Chief Executive of the UK Space Agency, who commented, “This significant investment shows how the UK continues to build on the capability of the UK space sector and demonstrates our continuing strong commitment to our membership in the European Space Agency.”

High Noon for ESA Funding

Sentinel-2 Image of Plymouth from 2016. Data courtesy of Copernicus/ESA.

Sentinel-2 Image of Plymouth from 2016. Data courtesy of Copernicus/ESA.

The future direction of the space industry in Europe is set to be debated at the European Space Agency (ESA) Ministerial Council taking place at the start of December. It will look at the Space Strategy for Europe which we reviewed last week, and crucially will set ESA’s budget for the few next years.

The Council is the governing body of ESA and each of the 22 member states is represented, plus Canada. The Council is chaired by ESA’s Director General Jan Woerner, and he gave a press briefing in Paris earlier this week in advance of the meeting.

Sadly, I was unable to go to France for the meeting; but luckily Peter B de Selding from Space News was there and produced an excellent article which highlighted the key points including:

  • ESA is seeking an €11 billion settlement
  • Concern over the Norway’s proposed 75% contribution reduction
  • The ExoMars Programme, which hit the headlines earlier this year when the Schiaparelli lander crashed on its descend to the Mars surface, has a funding gap of €400 million.
  • €800 million is being sought to continue the collaboration with NASA on the International Space Station until 2024

The headline message on money is clearly the requested €11 billion settlement. In 2016 the ESA budget was €5.25 billion, of which almost 30% was income from the European Union (EU), Eumetsat and other programmes. The remaining 70% came from the contributions of each member state and Canada, and it is these future contributions that will be discussed at the Ministerial. This year the biggest contributor was Germany (€872.6 m), followed by France (€844.5 m) and Italy (€512 m) – between them these three accounted for almost 60% of the ESA member state budget.

For us, Pixalytics and the UK, there were a couple of interesting points. Firstly, ESA’s Earth Observation Envelope Programmes (EOEP-5) has had a 12.5% funding cut reducing their budget down to €1.4 bn for the period 2017 – 2025. It’s not currently clear what impact this reduction will, or will not, have on existing and planned activities.

Secondly, and for the second week running the blog has had to mention the B word. We’ve previously written about the fact that ESA and the EU are different organisations, and that Brexit does not directly impact our involvement with ESA – a point reinforced by the Director General at the briefing.

Indirectly though, Brexit impacts, if not dominates, the political and financial landscape of the country and as such will have affected the discussions surrounding our ESA contribution commitment. For example:

  • Dropping Value Of Sterling: The pound has dropped by over 13% since the EU Referendum, significantly increasing the cost to the UK of our ESA contribution which was €13.2 m in 2016.
  • Budget Pressures: In addition to the drop in the pound, the UK Space Agency has to compete with every other Government Department for funding. Given the current austerity financial approach, coupled with the additional costs of dealing with Brexit, money is tight.
  • Space Industry Profile: Every industry is currently fighting to get their agenda’s onto Government Minister’s desk to ensure they get then ‘best deal from Brexit’. Space is no different. We may not have the London centre of the financial sector or the emotional impact of the farmers and fisherman, but we are a strong and important part of the economy.

We need Ministers to understand our industry, and to ensure that they support us as much as possible. This means, as we said last week, that we need to give a positive commitment to our ongoing involvement with ESA and a strong financial contribution at the Ministerial in Lucerne on the 1st and 2nd of December.

We await the outcome with interest!

Remote Sensing: Learning, Learned & Rewritten

Image of Yemen acquired by Sentinel-2 in August 2015. Data courtesy of ESA.

Image of Yemen acquired by Sentinel-2 in August 2015. Data courtesy of ESA.

This blog post is about what I did and what thoughts came to mind on my three-month long ERASMUS+ internship at Pixalytics which began in July and ends this week.

During my first week at Pixalytics, after being introduced to the Plymouth Science Park buildings and the office, my first task was to get a basic understanding of what remote sensing is actually about. With the help of Sam and Andy’s book, Practical Handbook of Remote Sensing, that was pretty straightforward.

As the words suggest, remote sensing is the acquisition of data and information on an object without the need of being on the site. It is then possible to perform a variety of analysis and processing on this data to better understand and study physical, chemical and biological phenomena that affect the environment.

Examples of programming languages: C, Python & IDL

Examples of programming languages: C, Python & IDL

I soon realized that quite a lot of programming was involved in the analysis of satellite data. In my point of view, though, some of the scripts, written in IDL (Interactive Data Language), were not as fast and efficient as they could be, sometimes not at all. With that in mind, I decided to rewrite one of the scripts, turning it into a C program. This allowed me to get a deeper understanding of satellite datasets formats (e.g. HDF, Hierarchical Data Format) and improve my overall knowledge of remote sensing.

While IDL, a historic highly scientific language for remote sensing, provides a quick way of writing code, it has a number of glaring downsides. Poor memory management and complete lack of strictness often lead to scripts that will easily break. Also, it’s quite easy to write not-so-pretty and confusing spaghetti code, i.e., twisted and tangled code.

Writing C code, on the other hand, can get overly complicated and tedious for some tasks that would require just a few lines in IDL. While it gives the programmer almost full control of what’s going on, some times it’s just not worth the time and effort.

Instead, I chose to rewrite the scripts in Python which I found to be quite a good compromise. Indentation can sometimes be a bit annoying, and coming from other languages the syntax might seem unusual, but its great community and the large availability of modules to achieve your goals in just a few lines really make up for it.

It was soon time to switch to a bigger and more complex task, which has been, to this day, what I would call my “main task” during my time at Pixalytics: building an automated online processing website. The website aspect was relatively easy with a combination of the usual HTML, Javascript, PHP and CSS, it was rewriting and integrated the remote sensing scripts that was difficult. Finally all of those little, and sometimes not quite so little, scripts and programs were available from a convenient web interface, bringing much satisfaction and pride for all those hours of heavy thinking and brainstorming. Hopefully, you will read more about this development in the future from Pixalytics, as it will form the back-end of their product suite to be launched in the near future.

During my internship there was also time for events inside the Science Park such as the Hog Roast, and events outside as well when I participated at the South-West England QGIS User Group meeting in Dartmoor National Park. While it is not exactly about remote sensing, but more on the Geographic Information System (GIS) topic it made me realize how much I had learned on remote sensing in my short time at Pixalytics, I was able to exchange my opinions and points of view with other people that were keen on the subject.

A side project I’ve been working on in my final weeks was looking at the world to find stunning, interesting (and possibly both) places on Earth to make postcards from – such as one at the top of the blog. At times, programming and scientific research reads can get challenging and/or frustrating, and it’s so relaxing to just look at and enjoy the beauty of our planet.

It is something that anyone can do as it takes little knowledge about remote sensing. Free satellite imagery is available through a variety of sources; what I found to be quite easy to access and use was imagery from USGS/NASA Landsat-8 and ESA Sentinel-2. It is definitely something I would recommend.

Finally, I want to say “thank you” to Sam and Andy, without whom I would have never had the opportunity to get the most out of this experience, in a field in which I’ve always been interested into, but had never had the chance to actually get my hands on.

Blog written by Davide Mainas on an ERASMUS+ internship with Pixalytics via the Tellus Group.

Differences Between Optical & Radar Satellite Data

Ankgor Wat, Cambodia. Sentinel-2A image courtesy of ESA.

Ankgor Wat, Cambodia. Sentinel-2A image courtesy of ESA.

The two main types of satellite data are optical and radar used in remote sensing. We’re going to take a closer look at each type using the Ankgor Wat site in Cambodia, which was the location of the competition we ran on last week’s blog as part of World Space Week. We had lots of entries, and thanks to everyone who took part!

Constructed in the 12th Century, Ankgor Wat is a temple complex and the largest religious monument in the world. It lies 5.5 kilometres north of the modern town of Siem Reap and is popular with the remote sensing community due to its distinctive features. The site is surrounded by a 190m-wide moat, forming a 1.5km by 1.3km border around the temples and forested areas.

Optical Image
The picture at the top, which was used for the competition, is an optical image taken by a Multi-Spectral Imager (MSI) carried aboard ESA’s Sentinel-2A satellite. Optical data includes the visible wavebands and therefore can produce images, like this one, which is similar to how the human eye sees the world.

The green square in the centre of the image is the moat surrounding the temple complex; on the east side is Ta Kou Entrance, and the west side is the sandstone causeway which leads to the Angkor Wat gateway. The temples can be clearly seen in the centre of the moat, together with some of the paths through the forest within the complex.

To the south-east are the outskirts of Siem Reap, and the square moat of Angkor Thom can be seen just above the site. To the right are large forested areas and to the left are a variety of fields.
In addition to the three visible bands at 10 m resolution, Sentinel-2A also has:

  • A near-infrared band at 10 m resolution,
  • Six shortwave-infrared bands at 20 m resolution, and
  • Three atmospheric correction bands at 60 m resolution.

Radar Image
As a comparison we’ve produced this image from the twin Sentinel-1 satellites using the C-Band Synthetic Aperture Radar (SAR) instrument they carry aboard. This has a spatial resolution of 20 m, and so we’ve not zoomed as much as with the optical data; in addition, radar data is noisy which can be distracting.

Angkor Wat, Cambodia. SAR image from Sentinel-1 courtesy of ESA.

Angkor Wat, Cambodia. SAR image from Sentinel-1 courtesy of ESA.

The biggest advantage of radar data over optical data is that it is not affected by weather conditions and can see through clouds, and to some degree vegetation. This coloured Sentinel-1 SAR image is produced by showing the two polarisations (VV and VH i.e. vertical polarisation send for the radar signal and vertical or horizontal receive) alongside a ratio of them as red, green and blue.

Angkor Wat is shown just below centre, with its wide moat, and other archaeological structures surrounding it to the west, north and east. The variety of different landscape features around Angkor Wat show up more clearly in this image. The light pink to the south is the Cambodian city of Siem Reap with roads appearing as lines and an airport visible below the West Baray reservoir, which also dates from the Khmer civilization. The flatter ground that includes fields are purple, and the land with significant tree cover is shown as pale green.

Conclusion
The different types of satellite data have different uses, and different drawbacks. Optical imagery is great if you want to see the world as the human eye does, but radar imagery offers better options when the site can be cloudy and where you want an emphasis on the roughness of the surfaces.