Ten Top Tips Learnt Working for a Small Remote Sensing Company

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

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

I am approaching the end of my year at Pixalytics, and this blog is summary of what I’ve learnt from working for a small commercial remote sensing company.

The work itself has been a real blessing for me. Remote sensing product development was just the role I had been looking for, so I took it on with relish. During the year I have spent time researching, and supporting the product development of, flood mapping using SAR imagery, vegetation time series and light pollution.

I’ve learnt a huge amount over the past twelve months, and here are my top ten tips on researching & developing remote sensing products:

  1. Keep in mind who your stakeholders are and exactly what they require.
  2. Ensure your ground site is really covered by the satellite image, as coverage tends to be diagonal rather than straightforward latitude and longitude square and can miss a site altogether.
  3. Practise program version control at all times!
  4. Check the images you are using are the best ones for your requirements, i.e., not 16 day composites when daily images are more suitable and available; stopping you wasting a day downloading the wrong images!
  5. Write down problem solving routines, so next time you can do it for yourself!
  6. It’s always important to run pilots and streamline programming. This will save time and effort, and help verify that your end product is statistically robust.
  7. Write down what you find and keep good records of your algorithms and programming, so that you don’t duplicate work.
  8. Write technical notes on your work, so that programs can be easily shared, reviewed and run by others.
  9. Allow sufficient time before deadlines for reviewing and reworking.
  10. Make notes on the data you are using as you go along, including source, dates, locations and any company/organisation credits needed.

These are all lessons I’ll be taking with me when I leave, whether in commerce or academia.

It’s also been an insight into how a business is run, via these activities and hearing (one side!) of Sam’s teleconferences. Plus I’ve been involved in valuable encounters with the Environment Agency on products and have attended conferences, and given a presentation at one, on behalf of Pixalytics.

Plymouth has also been fun to explore. I’ve enjoyed visiting the various arts venues all over the city together with the galleries and museums, festivals and excellent cuisine.

Many thanks to Sam and Andy at Pixalytics for giving me this opportunity. I’m sad to leave and have enjoyed my time here.

Blog written by Dr Louisa Reynolds.

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.

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.

It’s World Space Week!!

world-space-week-logoDid you know it’s World Space Week? It occurs between the 4th and 10th October each year, because:

  • On 4th October 1957 the first human-made Earth satellite, Sputnik 1, was launched; and
  • On 10th October 1967: The Treaty on Principles Governing the Activities of States in the Exploration and Peaceful Uses of Outer Space, including the Moon and Other Celestial Bodies was signed – see previous blog for more details.

This annual international celebration aims to inspire everyone about space, encourage young people to get involved in science, technology, engineering and maths and to demonstrate the benefits, and use, of space technology. The first World Space Week occurred in 2000, and each year has a specific theme.

2016 World Space Week
We’re really excited this year as the theme is ‘Remote Sensing: Enabling our Future’. It’s celebrating Earth Observation (EO), and highlighting the variety of EO missions in space and the applications which use their data.

There are over 1,000 events taking place all over the world to celebrate remote sensing, and they are all listed on the World Space Week website. It seems as though Brazil is holding the most events this year, a whopping 159! Have a look through and see if there is anything you’d like to go to. If not, create your own event –

  • Spend a night looking at the stars.
  • Use Google Earth to look at your local area from space.
  • Get some friends together and watch classic space films.
  • Build your own spacecraft – Both ESA and SSTL have cut out models you can use.


Competition Image courtesy of ESA.

Competition Image courtesy of ESA.

Here at Pixalytics, we couldn’t let the Remote Sensing theme go by without getting involved. So we’ve decided to run our first ever Twitter competition!! The prize is a copy of our book ‘Practical Handbook of Remote Sensing’, which guides complete beginners through the process of finding, downloading, analysing and applying remote sensing data. We’ll post the book, free of charge, anywhere in the world!

The competition has now closed. Thanks to everyone who entered.

The location was Angkor Wat in Cambodia, read more about the site our next blog.

The Day the Lights Dimmed

According to the paper published by Falchi et al in June 2016 around 80% of the world’s population suffer from light pollution. The paper, ‘The new world atlas of artificial night sky brightness’, further noted that in Europe and the USA over 99% of people experience skyglow.

Skyglow is one part of light pollution, and refers to the brightening of the night sky over inhabited areas. The prominence of this feature was demonstrated last week in Puerto Rico when a large fire in the Aguirre Power Plant, in the area of Sanlinas, caused the lights to dim across the island.

The fire began when a power switch overheated causing an oil tank to explode. The resulting fire spread over a three acre area and effected power generation and cut off water supplies. Around one and half million people lost power equating to over 40% of the island’s population and 350,000 people were cut off from water.

This power loss gave a spectacular example of the skyglow effect, as it was possible to produce comparable night time pictures from satellites. Pictures twenty-four hours apart were taken by the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard the Suomi NPP satellite. In a recent blog on the Rio Olympics, we described the instrument in detail.

Image of Puerto Rico, acquired on 21st September 2016 from the VIIRS instrument. Data courtesy of NASA/ NASA’s Earth Observatory

Image of Puerto Rico, acquired on 21st September 2016 from the VIIRS instrument. Data courtesy of NASA/ NASA’s Earth Observatory

On the right is the ‘before image’ acquired at 2.50am local time on the 21st September. On the North coast, just to the right of centre, the bright white concentration shows the light from the capital city, San Juan. This city is the centre for manufacturing, finance and tourism for the island, and the site of its key seaport. Light can also be seen around the edge of the island, which effectively maps the islands interstate highways. The power outage affected the whole island including the westerly cities of Mayagüez and Aguadilla, the southern coastal city of Ponce and Humacao on the east coast.

Image of Puerto Rico, acquired on 22nd September 2016 from the VIIRS instrument. Data courtesy of NASA/ NASA’s Earth Observatory

Image of Puerto Rico, acquired on 22nd September 2016 from the VIIRS instrument. Data courtesy of NASA/ NASA’s Earth Observatory

Compare this with the ‘after image’ to the right which was taken approximately twenty four hours later at 2.31am on the 22nd September. Power had already started coming back on by this point, but only 130,000 were connected in the first twelve hours, and so there is still a major outage. The concentration around San Juan is reduced significantly, as are the lights mapping the interstate highways. All the areas are still identifiable, but the reduction in skyglow is apparent and obvious.

Whilst the pictures of cities and islands at night can be amazing, light pollution does have negative impacts on both us and the natural world – particularly nocturnal wildlife.

These images demonstrate the impact of skyglow, and we should all look to try and reduce the amount of light pollution in own lives, cities and countries.

Earth observation: Launches Gone, Launches Due & Launches Planned

Artist's rendition of a satellite - 3dsculptor/123RF Stock Photo

Artist’s rendition of a satellite – 3dsculptor/123RF Stock Photo

September is a busy month for Earth observation satellites, and so here is a round-up of the month.

Launches Gone
The Indian Space Research Agency (ISRA) launched the INSAT-3DR weather satellite on September 8th into a geostationary orbit. It carries a multi-spectral imager capable of collecting data in six wavebands: visible, shortwave and midwave infrared, water vapour and two thermal bands. Taking an image every 26 minutes it will be used to monitor cloud patterns and storm systems, collecting data about outgoing longwave radiation, precipitation estimates, Sea Surface Temperature (SST), snow cover and wind speeds.

The second major launch took place on September 15th, from Europe’s Space Centre in French Guiana, when five new Earth observation satellites were put into orbit.

  • Four of these satellites, SkySats 4, 5, 6 & 7, were launched for the commercial company Terra Bella – which is owned by Google. It’s reported that they have informally named these satellites after the Star Wars characters: R2D2, Luke, C3PO and Leia! These small satellites provide 90 cm resolution for panchromatic images and 2 m for visible and near infrared wavebands. They also offer video acquired at 30 frames per second with a resolution of 1.1 m.
  • In addition, this launch brought a new country into the Earth Observation satellite owning family, as Peru launched PeruSAT-1 which will be operated by their military authorities. This satellite is in a 695 km sun-synchronous low Earth orbit and will provide imagery in the visible light wavebands with a 70 cm resolution. The data is expected to help study forest health, monitor illegal logging and gold mining, and provide support with natural disasters. However, the details of who can access to the data, the cost and how to access it are still to be made public.

Launches to Come
Last week we said DigitalGlobe’s WorldView-4 satellite was due to launch on the Friday. The problem of having a blog go live before an event means you can be wrong, and on this occasion we were! Friday’s launch was postponed for two days due to a leak during the propellant loading. Unfortunately, a wildfire then broke out near the Vandenburg Air Force base, and the launch had to be postponed a second time. It is hoped it will go ahead before the end of the month.

Following on from INSAT-3DR, ISRA is due to launch another four satellites in the last week of September including:

  • India’s ScatSat, a replacement for the Oceansat-2. Carrying OSCAT (OceanSat-2 Scanning Scatterometer) it will offer data related to weather forecasting, sea surface winds, cyclone prediction and tracking satellite. The data collected will be used by organisations globally including NASA, NOAA and EUMETSAT.
  • A second Earth observation satellite on the launch is Algeria’s first CubeSat – AlSat Nano. It was designed and built at the Surry Space Centre by Algerian Graduate students, as part of joint programme between the UK Space Agency and the Algerian Space Agency. It will carry a camera, magnetometer and will be testing an innovative solar cell which is one tenth of a millimetre thick.

Launches Being Planned
The next country to join the Earth Observation community could well be North Korea. It was reported this week that they had carried out a successful ground test of a new rocket engine which would give them the capacity to launch various satellites, including Earth Observation ones.

Airbus Defence and Space also announced plans this week for four Earth observation satellites to be launched in 2020 and 2021. These will provide very high resolution imagery and continuity for the existing two Pléiades satellites.

As we’ve previously discussed, the trend in launches continues apace for the Earth observation community.

Space is Hard Work!

Pictures showing Sentinel-1A’s solar array before and after the impact of a millimetre-size particle on the second panel. The damaged area has a diameter of about 40 cm. Data courtesy of ESA>

Pictures showing Sentinel-1A’s solar array before and after the impact of a millimetre-size particle on the second panel. The damaged area has a diameter of about 40 cm. Data courtesy of ESA>

Space is unpredictable. Things don’t always go as planned. Over the last few weeks some of the difficulties of working in space have been highlighted.

Gaofen 10
The start of September did not go well for the satellite industry with two failed launches. Firstly, the Chinese Gaofen 10 Earth observation satellite launched on the 31st August onboard the Long March 4C rocket did not appear to have achieved its orbit. The lack of certainty about this is because no official announcement has been made by Chinese authorities, despite pictures of debris appearing on social media the following day. Gaofen-10 was believed to be carrying a multi-polarized C-band SAR instrument and was intended to be part of the China High-Resolution Earth Observation System (CHEOS), joining the existing seven orbiting Gaofen satellites to provide real-time global Earth observations.

The explosion of the SpaceX Falcon rocket on the Cape Canaveral Launchpad received significantly more mainstream media attention than Gaofen 10. This was partly due to the fact it was a SpaceX rocket, and partly because the satellite it carried was going to be used by Facebook. When you have two of the US’s most well-known technology gurus involved, it was bound to grab the headlines.

No-one was hurt, but the satellite was destroyed by the explosion that occurred whilst the rocket was being loaded with fuel; investigations continue into the cause of this. It was an Israeli communication satellite called Amos 6, whose main purpose was the delivery of television channels. However, Facebook also had an agreement to use the satellite to provide internet connectivity to sub-Saharan Africa.

Sentinel-1A Struck in Space
ESA recently confirmed that the Copernicus Sentinel-1A satellite was hit by a millimetre-size particle on one of its solar wings on the 23rd August. The impact caused slight changes to the orientation and orbit of the satellite, although it hasn’t impacted performance.

Engineers were able to activate the onboard cameras, which provided a clear picture of the impact site on the solar panel, which can be seen in image at the top of the blog. The damaged area is approximately 40 centimetres wide, which is consistent with the impact of a fragment of less than 5 millimetres. This damage has reduced the power generated by the solar wing, although the loss will not impact performance as current power generation remains higher than what the satellite requires for routine operations.

It’s not clear whether Sentinel-1A was stuck by space debris or a micrometeoroid. Given the amount of space debris up there significantly larger than 5 millimetres, the potential damage that could be done to satellites is massive!

Back in STEREO
On a more positive note, last month NASA re-established contact with a satellite after a gap of almost two years. In 2006 NASA launched a pair of twin Solar TErrestrial RElations Observatory (STEREO) satellites to provide data about the sun’s solar flares and coronal mass ejections. Contact was lost with STEREO-B (so called because it was orbiting behind STEREO-A; the A signified it was ahead!) on the 1st October 2014 during a routine test. Since that time NASA has been working to re-establish contact with STEREO-B, and amazingly did so on the 21st August 2016!

Having made contact the team are assessing the satellite, and its components, with the hope of bringing it back to working order in the near future.

Close-up of the Philae lander, imaged by Rosetta’s OSIRIS narrow-angle camera on 2 September 2016 from a distance of 2.7 km. The image scale is about 5 cm/pixel. Philae’s 1 m-wide body and two of its three legs can be seen extended from the body. Image courtesy of ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Close-up of the Philae lander, imaged by Rosetta’s OSIRIS narrow-angle camera on 2 September 2016 from a distance of 2.7 km. The image scale is about 5 cm/pixel. Philae’s 1 m-wide body and two of its three legs can be seen extended from the body. Image courtesy of ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/ INTA/UPM/DASP/IDA.

Philae Located!
A second discovery after lost contact is ESA’s Philae Lander! This was the robot that made a historic landing on Comet 67P/Churyumov–Gerasimenko in November 2014, as part of the Rosetta mission. Unfortunately, Philae bounced away from the intended landing site and after a short period of operation, communications were lost. There was brief resurrection in July 2015, before silence returned.

Amazingly, last week the resting site of Philae was finally located with Rosetta’s high resolution camera. It is stuck in a dark crack on the comet surface, explaining why its solar powered batteries were unable to be recharged.

Philae will be joined later this month by the Rosetta probe itself, as it will be crash landed onto the comet. Cameras and chemical sensors will be operating throughout the descent which is planned to take place on the 30th September bringing to end this historic comet chasing mission.

Onward Despite Difficulties
DigitalGlobe’s WorldView 4 satellite is due to be launched on Friday, 16th September aboard an Atlas V rocket from Vandenberg Air Force Base. Like WorldView 3 this satellite should provide imagery with a spatial resolution of 31 cm in panchromatic mode and 1.24 m in multispectral mode.

This shows that despite all of the ups and downs of the last few weeks, the satellite industry keeps moving forward!

Gathering of the UK Remote Sensing Clans


The Remote Sensing & Photogrammetry Society (RSPSoc) 2016 Annual Conference is taking place this week, hosted by the University of Nottingham and the British Geological Society. Two Pixalytics staff, Dr Sam Lavender and Dr Louisa Reynolds, left Plymouth on a cold wet day on Monday, and arrived in the Nottinghamshire sunshine as befits RSPSoc week. The conference runs for three days and gives an opportunity to hear about new developments and research within remote sensing. Both Sam and Louisa are giving presentations this year.

Tuesday morning began with the opening keynote presentation given by Stephen Coulson of the European Space Agency (ESA), which discussed their comprehensive programme including the Copernicus and Earth Explorer missions. The Copernicus missions are generating ten times more data than similar previous missions, which presents logistical, processing and storage challenges for users. The future vision is to bring the user to the data, rather than the other way around. However, the benefits of cloud computing are still to be fully understood and ESA are interested in hearing about applications that couldn’t be produced with the IT technology we had 5 years ago.

After coffee Sam chaired the commercial session titled ‘The challenges (and rewards) of converting scientific research into commercial products.’ It started with three short viewpoint presentations from Jonathan Shears (Telespazio VEGA UK), Dr Sarah Johnson (University of Leicester) and Mark Jarman (Satellite Applications Catapult), and then moved into an interactive debate. It was great to see good attendance and a lively discussion ensued. Sam is planning to produce a white paper, with colleagues, based on the session. Some of the key points included:

  • Informative websites so people know what you do
  • Working with enthusiastic individuals as they will make sure something happens, and
  • To have a strong commercial business case alongside technical feasibility.
Dr Louisa Reynolds, Pixalytics Ltd, giving a presentation at RSPSoc 2016

Dr Louisa Reynolds, Pixalytics Ltd, giving a presentation at RSPSoc 2016

Louisa presented on Tuesday afternoon within the Hazards and Disaster Risk Reduction session. Her presentation was ‘A semi-automated flood mapping procedure using statistical SAR backscatter analysis’ which summarised the work Pixalytics has been doing over the last year on flood mapping which was funded by the Space for Smarter Government Programme (SSGP). Louisa was the third presenter who showed Sentinel-1 flood maps of York, and so it was a popular topic!

Alongside Louisa’s presentation, there have some fascinating other talks on topics as varied as:

  • Detecting and monitoring artisanal oil refining in the Niger Delta
  • Night time lidar reading of long-eroded gravestones
  • Photogrammatic maps of ancient water management features in Al-Jufra, Libya.
  • Seismic risk in Crete; and
  • Activities of Map Action

Although for Louisa her favourite part so far was watching a video of the launch of Sentinel 1A, through the Soyuz VS07 rocket’s discarding and deployment stages, simultaneously filmed from the craft and from the ground.

Just so you don’t think the whole event is about remote sensing, the conference also has a thriving social scene. On Monday there was a tour of The City Ground, legendary home of Nottingham Forest, by John McGovern who captained Forest to successive European Cup’s in 1979 and 1980. It was a great event and it was fascinating to hear about the irascible leadership style of Brian Clough. Tuesday’s event was a tour round the spooky Galleries of Justice Museum.

The society’s Annual General Meeting takes place on Wednesday morning; Sam’s presentation, ‘Monitoring Land Cover Dynamics: Bringing together Landsat-8 and Sentinel-2 data’, is in the Land Use/Land Cover Mapping session which follows.

The start of RSPSoc has been great as usual, offering chances to catch up with old remote sensing friends and meet some new ones. We are looking forward to rest of the conference and 2017!

Earth observation satellites in space in 2016

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

Earth Observation (EO) satellites account for just over one quarter of all the operational satellites currently orbiting the Earth. As noted last week there are 1 419 operational satellites, and 374 of these have a main purpose of either EO or Earth Science.

What do Earth observation satellites do?
According to the information within the Union of Concerned Scientists database, the main purpose of the current operational EO satellites are:

  • Optical imaging for 165 satellites
  • Radar imaging for 34 satellites
  • Infrared imaging for 7 satellites
  • Meteorology for 37 satellites
  • Earth Science for 53 satellites
  • Electronic Intelligence for 47 satellites
  • 6 satellites with other purposes; and
  • 25 satellites simply list EO as their purpose

Who Controls Earth observation satellites?
There are 34 countries listed as being the main controllers of EO satellites, although there are also a number of joint and multinational satellites – such as those controlled by the European Space Agency (ESA). The USA is the leading country, singularly controlling one third of all EO satellites – plus they are joint controllers in others. Of course, the data from some of these satellites are widely shared across the world, such as Landsat, MODIS and SMAP (Soil Moisture Active Passive) missions.

The USA is followed by China with about 20%, and Japan and Russia come next with around 5% each. The UK is only listed as controller on 4 satellites all related to the DMC constellation, although we are also involved in the ESA satellites.

Who uses the EO satellites?
Of the 374 operational EO satellites, the main users are:

  • Government users with 164 satellites (44%)
  • Military users with 112 satellites (30%)
  • Commercial users with 80 satellites (21%)
  • Civil users with 18 satellites (5%)

It should be noted that some of these satellites do have multiple users.

Height and Orbits of Earth observation satellites
In terms of operational EO satellite altitudes:

  • 88% are in a Low Earth Orbit, which generally refers to altitudes of between 160 and 2 000 kilometres (99 and 1 200 miles)
  • 10% are in a geostationary circular orbit at around 35 5000 kilometres (22 200 miles)
  • The remaining 2% are described as having an elliptical orbit.

In terms of the types of orbits:

  • 218 are in a sun-synchronous orbit
  • 84 in non-polar inclined orbit
  • 16 in a polar orbit
  • 17 in other orbits including elliptical, equatorial and molniya orbit; and finally
  • 39 do not have an orbit recorded.

What next?

Our first blog of 2016 noted that this was going to be an exciting year for EO, and it is proving to be the case. We’ve already seen the launches of Sentinel-1B, Sentinel-3A, Jason-3, GaoFen3 carrying a SAR instrument and further CubeSat’s as part of Planet’s Flock imaging constellation.

The rest of the year looks equally exciting with planned launches for Sentinel-2B, Japan’s Himawari 9, India’s INsat-3DR, DigitalGlobe’s Worldview 4 and NOAA’s Geostationary Operational Environmental Satellite R-Series Program (GOES-R). We can’t wait to see all of this data in action!

How many satellites are orbiting the Earth in 2016?

Image courtesy of ESA Note: The debris field shown in the image is an artist's impression based on actual data. However, the debris objects are shown at an exaggerated size to make them visible at the scale shown

Image courtesy of ESA
Note: The debris field shown in the image is an artist’s impression based on actual data. However, the debris objects are shown at an exaggerated size to make them visible at the scale shown

This is our annual update on the satellites currently orbiting the Earth.

How many satellites are orbiting the Earth?
According to the Index of Objects Launched into Outer Space maintained by United Nations Office for Outer Space Affairs (UNOOSA), there are currently 4 256 satellites currently orbiting the planet, an increase of 4.39% compared to this time last year.

221 satellites were launched in 2015, the second highest number in a single year, although it is below the record of 240 launched in 2014. 2016 may fall slightly short, as to date only 126 launches have occurred this year. The increase in satellites orbiting the Earth is less than the number launched last year, because satellites only have limited lifespans. The large communication satellites have expected lifetimes of 15 years and more, whereas the small satellites, such as CubeSat’s, may only have expected lifespans of 3 – 6 months.

How many of these orbiting satellites are working?
The Union of Concerned Scientists (UCS) details which of those orbiting satellites are operational and it is not as many as you think! According to their June 2016 update, there are currently only 1 419 operational satellites – only about one third of the number in orbit. This means there is quite a lot of useless metal hurtling around the planet! This is why there is a lot of interest from companies looking at how they capture and reclaim space debris, with methods such as space nets, slingshots or solar sails proposed.

What are all these satellites doing?
According the UCS data the main purposes for the operational satellites are:

  • Communications with 713 satellites
  • Earth observation/science with 374 satellites
  • Technology Demonstration/Development with 160 satellites
  • Navigation & Global Position with 105 satellites; and
  • Space Science with 67 satellites

It should be noted that some satellites do have multiple purposes. We will discuss the operational Earth observation satellites in more detail next week.

Who uses the satellite directly?
It’s interesting to note that there are four main types of users listed in the UCS database, although 17% of the satellites have multiple users we are concentrating on the main user:

  • 94 satellites listed with civil users: These tend to be educational institutes, although there are other national organisations also included. 46% of these satellites have a purpose of technology development, whilst Earth/Space science and observation account for another 43%.
  • 579 with commercial users: Commercial organisations and state organisations who want to sell the data they collect. 84% of these satellites focus on communications and global positioning services; of the remaining 12% are Earth observation satellites.
  • 401 with Government users: Mainly national Space organisations, together with other national and international bodies. 40% of these are communications and global positioning satellites; another 38% focus on Earth observation. Of the remainder space science and technology development have 12% and 10% respectively.
  • 345 with military users: Again communications, Earth observation and global positioning systems are the strong focus here with 89% of the satellites having one of these three purposes.

Which countries have launched satellites?
According to UNOOSA around 65 countries have launched satellites, although on the UCS database there are only 57 countries listed with operational satellites, again some satellites are listed with joint/multinational operators. The largest are:

  • USA with 576 satellites
  • China with 181 satellites
  • Russia with 140 satellites

The UK is listed as having 41 satellites, plus we’re involved in an additional 36 satellites that the European Space Agency has.

Remember when you look up!
Next time you out at look up at the night sky, remember that there is over two million kilograms of metal circling the Earth between you and the stars!