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.

SpaceX
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

RSPSOC

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!

Spinning Python in Green Spaces

2016 map of green spaces in Plymouth, using Sentinel-2 data courtesy of Copernicus/ESA.

2016 map of green spaces in Plymouth, using Sentinel-2 data courtesy of Copernicus/ESA.

As students, we are forever encouraged to find work experience to develop our real-life skills and enhance our CV’s. During the early period of my second year I was thinking about possible work experience for the following summer. Thanks to my University department, I was able to find the Space Placements in INdustry (SPIN) scheme. SPIN has been running for 4 years now, advertising short summer placements at host companies. These provide a basis for which students with degrees involving maths/physics/computer science can get an insight into the thriving space sector. I chose to apply to Pixalytics, and three months later they accepted my application in late March.

Fast forward a few more months and I was on the familiar train down to Plymouth in my home county of Devon. Regardless of your origin, living in a new place never fails to confuse, but with perseverance, I managed to settle in quickly. In the same way I could associate my own knowledge from my degree (such as atmospheric physics, and statistics) to the subject of remote sensing, a topic which I had not previously learnt about. Within a few days I was at work on my own projects learning more on the way.

My first task was an informal investigation into Open data that Plymouth City Council (PCC) has recently uploaded onto the web. PCC are looking for ways to create and support innovative business ideas that could potentially use open data. Given their background, Pixalytics could see the potential in developing this. I used the PCC’s green space, nature reserve and neighbourhood open data sets and found a way to calculate areas of green space in Plymouth using Landsat/Sentinel 2 satellite data to provide a comparison.

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

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

There were a few challenges to overcome in using the multiple PCC data sets as they had different coordinate reference systems, which needed to be consistent to be used in GIS software. For example, the Nature Reserves data set was partly in WGS84 and partly in OSGB 1936. Green space is in WGS 84 and the neighbourhood boundaries are in OSGB 1936. This meant that after importing these data sets in GIS software, they wouldn’t line up. Also, the green space data set didn’t include landmarks such as the disused Plymouth City airport, and large areas around Derriford Hospital and Ernsettle. Using GIS software I then went on to find a way to classify and calculate areas of green space within the Plymouth city boundary. The Sentinel-2 which can be seen above, has a higher spatial resolution and allowed me to include front and back gardens.

My green space map for 2016 created from Sentinel 2 data is the most accurate, and gives a total area of green space within the Plymouth neighbourhood boundary of 43 square kilometres, compared with 28 square kilometres that PCC have designated within their dataset. There are some obvious explainable differences, but it would be interesting to explore this deeper.

My second project was to write computer code for the processing and mosaicking of Landsat Imagery. Pixalytics is developing products where the user can select an area of interest from a global map, and these can cause difficult if the area crosses multiple images. My work was to make these images as continuous as possible, accounting for the differences in radiances.

I ended up developing a Python package, some of whose functions include obtaining the WRS path and row from an inputted Latitude and Longitude, correcting for the difference in radiances, and clipping and merging multiple images. There is also code that helps reduce the visual impact of clouds on individual images by using the quality band of the Landsat 8 product. This project took up most of my time, however I don’t think readers would appreciate, yet alone read a 500 line python script, so this has been left out.

I’d like to take this opportunity to thank Andrew and Samantha for giving me an insight into this niche, and potentially lucrative area of science as it has given me some direction and motivation for the last year of my degree. I hope I’ve provided some useful input to Pixalytics (even if it is just giving Samantha a very long winded Python lesson), because they certainly have done with me!

 

Blog written by:
Miles Lemmer, SPIN Summer Placement student.
BSc. Environmental Physics, University of Reading.

Night-time Treats

This image of Rio de Janeiro was acquired on the night of July 20, 2012 by the VIIRS instrument aboard the Suomi NPP satellite. Data courtesy of NASA/NASA’s Earth Observatory.

This image of Rio de Janeiro was acquired on the night of July 20, 2012 by the VIIRS instrument aboard the Suomi NPP satellite. Data courtesy of NASA/NASA’s Earth Observatory.

The Opening Ceremony of the Rio Olympics featured a plane taking off from the Maracanã Stadium and treating us to a fantastic night flight over Rio. It was a beautiful sequence to celebrate the famous Brazilian aviator Alberto Santos-Dumont, for us at Pixalytics it led to a conversation about the beauty of night-time satellite imagery!

Currently, the best source of night-time imagery comes from Visible Infrared Imaging Radiometer Suite (VIIRS) which is one of five instruments aboard the Suomi National Polar-orbiting Partnership satellite launched on 28 October 2011. Although, if you look on Twitter you’ll also see a huge number of night-time images taken by astronauts aboard the International Space Station. This data has been used as the basis of the Cities at Night citizen science project whose aim is to create a Google maps style map of the world – as the astronauts are using cameras to take photos of the places that interest them, and there is no georeferencing information, citizens identify the cities pictures.

In contrast VIIRS is an orbiting satellite and so continually collecting calibrated and georeferenced data of the whole globe. In the day VIIRS is collecting optical and temperature data over both the land and ocean, while at night it collects temperature data and the night-time imagery using the 750 m spatial resolution Day/Night Band (DNB). Working through both the night and day, the DNB needs to be calibrated through several orders of magnitude in brightness to accommodate the dramatic contrast between solar reflection and the darkness of night. Its forerunner was the uncalibrated Operational Linescan System (OLS) on the Defense Meteorological Satellite Program (DMSP) satellites, whose primary aim was to study clouds, but when its data was declassified in the 1970s it generated a lot of interest in low light night-time observations.

The DNB VIIRS images, like the one at the top of the blog, show hubs of human activity and the road arteries that connect them, and so are of special interest to the Campaign for the Protection of Rural England who use these types of maps to protect dark skies. It also enables calculations of light pollution to be made, together with indications of the associated carbon emissions. The DNB can pick up many different phenomena. For example, aurorae are visible, as well as gas flares, volcanic activity, the lights of ships, sea ice and climatological monitoring of clouds. It’s even possible to see thunderstorms, although individual lightning flashes are hard to make out in these snapshots, the glow inside clouds caused by them are evident as bright strips with DNB imagery as seen in this image from over Louisiana, USA on 4 April 2012 (Miller et al., 2013).

Another interesting discovery in 2012 was the presence of a faint ‘nightglow’ in the upper atmosphere on moonless night over the Pacific. The DNB team were aiming to collect scenes of complete darkness for calibration purposes, but they found clouds were still clearly visible. This was due to an assortment of photochemical reactions, especially of the molecule fragment hydroxyl, which allows this nightglow to pick up subtle atmospheric phenomena such as gravity waves and the tops of anvil clouds.

Here we’ve gone from an aviation image inspired from 1903 to modern satellites, all via the Rio Olympics. It’s amazing where space can take you!

 

Blog written by Dr Louisa Reynolds and Andrew Lavender from Pixalytics Ltd.

Rio Olympics from space

Rio de Janeiro, Brazil, acquired on the 13th July 2016. Image courtesy of Copernicus/ESA.

Rio de Janeiro, Brazil, acquired on the 13th July 2016. Image courtesy of Copernicus/ESA.

The Opening Ceremony of the 2016 Summer Olympics takes place on Friday and so we’ve decided to revive our highly infrequent blog series ‘Can you see sporting venues from space?’ Previously we’ve looked for the Singapore and Abu Dhabi Formula One Grand Prix Circuits, but this week we’re focussing on the Rio Olympic venues.

Rio de Janeiro
The Games of the XXXI Olympiad will take place from the 5th to the 21st August in the Brazilian city of Rio de Janeiro. It is expected that more than ten thousand athletes will be competing for the 306 Olympic titles across 37 venues, 7 of which are temporary venues and 5 are outside Rio. The remaining twenty-five are permanent venues within the city, and 11 have been newly built for the Olympics and Paralympics. It is these permanent venues that we’ll see if we can spot from space!

The image at the top of the blog shows the Rio area, and you’ll notice the dark green area in the centre of the image which is the Tijuca National Park containing one of the world’s largest urban rainforest. It covers an area of 32 km².

Spatial Resolution
Spatial resolution is the key characteristic in whether sporting venues can be seen from space, and in simplistic terms it refers to the smallest object that can be seen on Earth from that sensor. For example, an instrument with a 10 m spatial resolution means that each pixel on its image represents 10 m, and therefore for something to be distinguishable on that image it needs to be larger than 10 m in size. There are exceptions to this rule, such as gas flares, which are so bright that they can dominate a much larger pixel.

We used the phrase ‘simplistic terms’ above because technically, the sensor in the satellite doesn’t actually see a square pixel, instead it sees an ellipse due to the angle through which it receives the signal. The ellipses are turned into square pixels by data processing to create the image. Spatial resolution is generally considered to have four categories:

  • Low spatial resolution: tend to have pixels between 50 m and 1 km.
  • Medium spatial resolution: tend to have pixels between 4 m and 50 m.
  • High spatial resolution: tend to have pixels between 1 m and 4 m.
  • Very high spatial resolution: tend to have pixels between 0.25 m to 1 m

Clearly with very high resolution imagery, such as that provided by commercial Worldview satellites owned by DigitalGlobe, can provide great images of the Olympic venues. However, as you know we like to work with data that is free-to-access, rather than paid for data. We’ve used Sentinel-2 data for this blog, which has a 10 m spatial resolution for its visible and near infra-red bands via the multispectral imager it carries.

Can we see the Olympic venues from space?
In our earlier parts of this infrequent series we couldn’t see the night race from the Singapore circuit, but we did identify the Abu Dhabi track and red roof of the Ferrari World theme park. So can we see the Olympics? Actually we can!

Image courtesy of Copernicus/ESA.

Image courtesy of Copernicus/ESA.

On the image to left, you’ll notice two bright white circles, one in the middle of the image and the second to the south-east. The bright circle in the middle is the Olympic Stadium which will be hosting the athletics and stands out clearly from the buildings surrounding it, to the South East is the Maracanã Stadium which will stage the opening and closing ceremonies together with the finals of the football tournaments.

Image courtesy of Copernicus/ESA.

Image courtesy of Copernicus/ESA.

In the bottom left of the image is small triangular shape which is location for the Aquatics Stadium, Olympic Tennis Centre, the Gymnastic and Wheelchair basketball arena, and the Carioca arenas which will host basketball, judo, wrestling and boccia. The bottom of the triangle juts out into the Jacarepagua Lagoon.

Image courtesy of Copernicus/ESA.

Image courtesy of Copernicus/ESA.

In the top left of the image, you can see the runway of the military Afonsos Air Force Base and north of the air base are a number of other Olympic venues, however these are hard to spot within their surroundings – these include the Equestrian Centre, Hockey Centre, BMX Centre, Whitewater canoe slalom course and the Deodoro stadium which will host the Rugby 7s and modern pentathlon.

It is possible to see the Olympic venues from space! Good luck to all the athletics competing over the next few weeks.

History Comes Around

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

Remote sensing is a relatively young industry, but it doesn’t mean we don’t have history. We do. We shouldn’t it, and were reminded why this week as we bounced back through time.

We noticed an introductory tweet yesterday from the Earth Resources Observation and Science Centre (EROS) History Project established by the US Geological Survey. This project has created an amazing online archive of information about its involvement in remote sensing that contains documents, and videos, from 1960s/70s to the current day. A few of the archive items that caught our attention were:

News Release from United States Department of the Interior on the 21st September 1966 with the title ‘Earths Resources To Be Studied From Space’. What struck us was how the phrases could be from today.

  • ‘gathering facts about the natural resources of earth’
  • ‘the time is now right and urgent to apply space technology towards the solution of many pressing natural resources problems being compound by population and industrial growth’
  • ‘An opportunity to collect valuable resource data and use it to improve the quality of our environment’

Equally, the sessions from 1973 Management & Utilization of Remote Sensing Data Symposium, organized by the American Society of Photogrammetry, could easily be describing a current conference:

  • Role of Remote Sensing in Resource Management & Planning
  • Hydrological and Environmental Applications
  • Future Sensor and Information Handling Systems
  • Agricultural and Forestry Applications

We loved the 1980 User Frustrations with Landsat, which noted data quality issues like:

  • Desert scenes have no contrast
  • There’s no underwater detail in the image
  • The image is striped!

A reminder in the news release from 15 March 1989 on how close the world came to losing the Landsat archive. This release rescinded the order, made two weeks earlier, to shutdown Landsat 4 & 5 and to provide funding until a policy review of Landsat could be completed.

The archive is a wealth of interesting details about the history of US remote sensing, including the amount of data collected over the years to the more mundane, but no less fascinating, descriptions of the furniture required to set up EROS in the first instance! We’d highly recommend you have a look at this archive – although be warned, I lost a few hours in there whilst writing this blog!!

This week is also a big anniversary for Landsat-1 which was launched on the 23rd July 1972, and the first satellite image from it was received on the 26th July 1972 beginning the 44 year archive. It’s also the Landsat Science Team’s 2016 Summer meeting this week in South Dakota, and amongst the topics of discussion are future sensor capabilities for Landsat 10 – showing not much has changed from 1973!

Although remembering the past is important, it’s vital that we also look forward to the future. At the Landsat Science Team meeting, it was noted the target launch date for Landsat 9 is the 15th December 2020, and as discussed above they are already talking about Landsat 10!

Gliding Across The Ice

ESA’s Earth Explorer CryoSat. Image courtesy of ESA/AOES Medialab.

ESA’s Earth Explorer CryoSat. Image courtesy of ESA/AOES Medialab.

There’s been a flurry of reports in the last couple of weeks, reporting melting ice and retreating glaciers in Greenland and the Himalayas respectively.

A paper by McMillan et al (2016), titled ‘A high-resolution record of Greenland mass balance’ and published in Geophysical Research Letters earlier this month, highlighted that Greenland’s melting ice has contributed twice as much to sea level rise than in the previous twenty years. The research used CryoSat-2 radar altimetry between 1 January 2011 and 31 December 2014 to measure elevation changes in the Greenland ice.

The main instrument on ESA’s CryoSat-2 satellite is a Synthetic Aperture Radar (SAR)/Interferometric Radar Altimeter known as SIRAL, although also carries a second version of this instrument as a back-up. The SIRAL instrument has been enhanced to detect millimetre changes in the elevation of both ice-sheets and sea-ice. It sends out bursts of radar pulses, with an interval of 50 μs between them, covering a 250 m wide strip of the Earth and measures the time of the return signal to determine the height of the satellite above the Earth. It requires a very accurate measurement of its position to calculate this, and so it also carries a Doppler Orbit and Radio Positioning Integration by Satellite (DORIS) instrument to determine its orbit.

The research team discovered that the Greenland Ice Sheet lost an average of 269 ± 51 Gt/yr of snow and ice during the investigative period, which compared well with other independent measurements from sensors such as the Gravity Recovery and Climate Experiment (GRACE) satellite and results from climate models. This snow and ice loss corresponds to a 0.75 mm contribution to global sea-level rise each year.

It was reported this week that research undertaken by the Indian Space Research Organisation, Wadia Institute of Himalayan Geology and other institutions have revealed that the majority of the glaciers in India are retreating; albeit at different rates. Using remote sensing data up to 2006, the study looked at 82 glaciers in the Bhagirathi and Alaknanda river basins and found that there had been an overall loss of 4.6% of the glaciers within the region. The Dokriani glacier in Bhagirathi is retreating between 15 and 20 metres per year since 1995, whereas the Chorabari glacier in the Alaknanda basin is retreating 9-11 metres per year.

It’s interesting to read the retreating glacial picture alongside the research published by Schwanghart et al (2016), titled ‘Uncertainty in the Himalayan energy–water nexus: estimating regional exposure to glacial lake outburst floods’, in Environmental Research Letters. Here the research team completed the first region wide risk assessment of floods from glacial lakes, even though this only covered around a quarter dams in the Himalaya’s. The study mapped 257 dams against more than 2,300 glacial lakes within the region and found that over 20% of the dams are likely to be overwhelmed with flood water as rock systems that surround glacier-fed lakes fail. Due to the hydro-electric power needs of the region, more dams have been built in recent years, putting them closer to glacier-fed lakes.

The potential danger of this issue is demonstrated by the collapse of Zhangzangbo, a glacier-fed lake in southern Tibet, in 1981 where 20 million cubic meters of floodwater damaged hydroelectric dams and roads causing damage of approximately $4 million.

These three reports also show the potential danger melting ice and glaciers pose both locally and globally. Remote sensing data, particularly from satellites such as CryoSat-2, can help us monitor and understand whether this danger is increasing.