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.

World Record Satellite Launch

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

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

Next week the Indian Space Research Organisation (ISRO) plans to launch 104 satellites in one go aboard its Polar Satellite Launch Vehicle (PSLV-C37) that will take off from Satish Dhawan Space Centre in Sriharikota, India.

To give an idea of the enormity of what ISRO is attempting, the current world record for satellites launched in a single mission is 37 by Russia in 2014. In addition, over the last fifty years the average number of objects launched in space in an entire year is only 138, according to the Online Index of Objects Launched into Outer Space maintained by the United Nations Office for Outer Space Affairs (UNOOSA). Furthermore these figures reveal this single mission will exceed the number of objects launched into space for the twelve months of 1996 and for the years 2001 to 2006 inclusive.

This mission was originally planned to launch 83 satellites, then an additional 20 were added to the payload and finally a further nano-satellite was squeezed in. Of these 104 satellites, 3 will be Indian satellites and the remainder will be small satellites from countries including Germany, Israel, Kazakhstan, Netherlands, Switzerland, and the US.

One of the key challenges is to ensure that they do not collide. ISRO plans to achieve this by changing the degree of angle for each batch of satellites launched. It is expected that the entire batch of satellites will be launched within 90 minutes.

This launch is a really exciting one for the Earth Observation community because it includes:

  • Cartosat 2D is the next satellite in India’s Cartosat mission. These satellites carry both high resolution multi- spectral imagers and a panchromatic camera, and the mission focus is cartography. It has a sub-metre spatial resolution, a 10 km swath and a revisit period of four days. This is the primary payload, and will be the heaviest satellite on the launch vehicle at 730 kg.
  • Planet’s Flock 3p which consists of 88 satellites, and will be the largest constellation of satellites ever launched.

Planet was in the news last week as it confirmed it had completed the purchase of satellite imaging company Terra Bella from Google. Terra Bella’s SkySat’s fleet of high resolution satellites will complement the existing global coverage of Planet’s existing courser resolution fleet. When combined with the new satellites, this will help Planet to achieve their aim of imaging the entire globe every day. Thereby, offering a wide range of potential capabilities for Planet in the satellite data reseller/supplier market.

ISRO’s launch is currently scheduled for February 15th and will demonstrate a new level of efficiency for cubesats; something that is becoming increasingly important. We’ll be watching closely, and wish them luck.

Have you read the top Pixalytics blogs of 2016?

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

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

As this is the final blog of the year we’d like to take a look back over the past fifty-two weeks and see which blog’s captured people’s attention, and conversely which did not!

It turns out that seven of the ten most widely viewed blogs of the last year weren’t even written in 2016. Four were written in 2015, and three were written in 2014! The other obvious trend is the interest in the number of satellites in space, which can be seen by the titles of six of the ten most widely read blogs:

We’ve also found these blogs quoted by a variety of other web pages, and the occasional report. It’s always interesting to see where we’re quoted!

The other most read blogs of the year were:

Whilst only three of 2016’s blogs made our top ten, this is partly understandable as they have less time to attract the interest of readers and Google. However, looking at most read blogs of 2016 shows an interest in the growth of the Earth Observation market, Brexit, different types of data and Playboy!

We’ve now completed three years of weekly blogs, and the views on our website have grown steadily. This year has seen a significant increase in viewed pages, which is something we’re delighted to see.

We like our blog to be of interest to our colleagues in remote sensing and Earth observation, although we also touch on issues of interest to the wide space, and small business, communities.

At Pixalytics we believe strongly in education and training in both science and remote sensing, together with supporting early career scientists. As such we have a number of students and scientists working with us during the year, and we always like them to write a blog. Something they’re not always keen on at the start! This year we’ve had pieces on:

Writing a blog each week can be hard work, as Wednesday mornings always seem to come around very quickly. However, we think this work adds value to our business and makes a small contribution to explaining the industry in which we work.

Thanks for reading this year, and we hope we can catch your interest again next year.

We’d like to wish everyone a Happy New Year, and a very successful 2017!

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!!

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.

Remote Sensing and the DIKW Pyramid

DIKW PyramidSatellite remote sensing industry is evolving and anyone working in it needs to become familiar with the Data, information, Knowledge, Wisdom (DIKW) pyramid as this is one map, albeit simplistic, of the industry’s and our current journey.

Historically, satellite data was either sold as the original image or with a small amount of processing undertaken. If anyone wanted to do anything beyond basic processing, they had to do it themselves. However, things are changing.

According to a recent Euroconsult report, at least 3,600 small satellites will be launched over the next decade. The United Nations Office on Outer Space Affairs only lists 7,370 objects that have ever been launched into space, of which only 4,197 are still in orbit. We’re increasing the number of objects orbiting the Earth by 85% by smallsats alone, larger satellites will add even more.

The volume, variety and speed of this data collected by these satellites will present a step change not only in the type of applications companies will be able to offer, but, crucially, also in customer expectations – more and more they will be looking for added value.

One way of considering this is through the DIKW pyramid, which can be seen at the top of the blog, it’s credited to American organisational theorist Russell Ackoff in 1989, building on the ideas of Milan Zeleny two years earlier.

A simple summary of the pyramid starts with the collection of data which means nothing in its own right, it is simply data. Information is derived from data by asking the who, what, where, when and how questions. Knowledge is information to which expert skills and experience have been added to create more value – which is more profitable in a business context. Finally, wisdom is understanding what actions to take based on the knowledge you’ve gained.

Applying this to satellite remote sensing for agriculture, one example might be: data is the satellite data/image of the field. Information is knowing when the image was taken leading to where in the growing cycle the crop was. Knowledge is applying scientific algorithms to know the soil moisture, how much nutrients are in the soil or how much vegetation is present in various parts of the field. Wisdom is knowing what nutrients and fertilizers to apply, based on the knowledge gained, to improve crop yields.

A lot of Earth observation products are at the data or information level, with a few at the knowledge level, and even fewer at the wisdom level. Customers more and more want wisdom products, and they aren’t that interested in what was required to create them. When you add to this the additional types of geospatial information, e.g., optical and radar used together alongside airborne and in-field ground based measurements, the variety of open datasets and the new science and technological breakthroughs, things are going to look very different, very quickly.

We’d accept that the DIKW isn’t a perfect tool, nor a perfect representation of our industry, but it is simple, indicative and worth thinking about. We wrote about our intention to create products in an earlier blog. We’re a long way from the wisdom sector, but are hoping to be firmly within the knowledge sector and collaborating to create wisdom. It’s not easy and some companies will find it harder to do than others, but is going to be the future. How are you preparing?

Living Planet Is Really Buzzing!

Living planet rotating global in the exhibition area, photo: S Lavender

Living planet rotating global in the exhibition area, photo: S Lavender

This week I’m at the 2016 European Space Agency’s Living Planet Symposium taking place in sunny Prague. I didn’t arrive until lunchtime on Monday and with the event already underway I hurried to the venue. First port of call was the European Association of Remote Sensing Companies (EARSC) stand as we’ve got copies of flyers and leaflets on their stand. Why not pop along and have look!

The current excitement and interest in Earth observation (EO) was obvious when I made my way towards the final sessions of the day. The Sentinel-2 and Landsat-8 synergy presentations were packed out, all seats taken and people were crowding the door to watch!

I started with the Thematic Exploitation Platforms session. For a long time the remote sensing community has wanted more data, and now we’re receiving it in ever larger quantities e.g., the current Copernicus missions are generating terabytes of data daily. With the storage requirements this generates there is a lot of interest in the use of online platforms to hold data, and then you upload your code to it, or use tools provided by the platform, rather than everyone trying to download their own individual copies. It was interesting to compare and contrast the approaches taken with hydrology, polar, coastal, forestry and urban EO data.

Tuesday was always going to be my busiest day of the Symposium as I was chairing two sessions and giving a presentation. I had an early start as the 0800 session on Coastal Zones I was co-chairing alongside Bob Brewin –a former PhD student of mine! It was great to see people presenting their results using Sentinel-2. The spatial resolution, 10m for the highest resolution wavebands, allows us to see the detail of suspended sediment resuspension events and the 705 nm waveband can be used for phytoplankton; but we’d still like an ocean colour sensor at this spatial resolution!

In the afternoon I headed into European Climate Data Records, where there was an interesting presentation on a long time-series AVHRR above-land aerosol dataset where the AVHRR data is being vicariously calibrated using the SeaWiFS ocean colour sensor. Great to see innovation within the industry where sensors launched one set of applications can be reused in others. One thing that was emphasised by presenters in both this session, and the Coastal Zone one earlier, was the need to reprocess datasets to create improved data records.

My last session of the day was on Virtual Research, where I was both co-chairing and presenting. It returned to the theme of handling large datasets, and the presentations focused on building resources that make using EO data easier. This ranged from bringing in-situ and EO data together by standardising the formatting and metadata of the in-situ data, through community datasets for algorithm performance evaluation, to data cubes that bring all the data needed to answer specific questions together into a three- (or higher) dimensional array that means you don’t spend all your time trying to read different datasets versus ask questions of them. My own presentation focused on our involvement with the ESA funded E-Collaboration for Earth Observation (E-CEO) project, which developed a collaborative platform  where challenges can be initiated and evaluated; allowing participants to upload their code and have it evaluated against a range of metrics. We’d run an example challenge focused on the comparison of atmospheric correction processors for ocean colour data that, once setup, could easily be rerun.

I’ve already realised that there too many interesting parallel sessions here, as I missed the ocean colour presentations which I’ve heard were great. The good news for me is that these sessions were recorded. So if you haven’t be able to make to Prague in person, or like me you are here but haven’t seen everything you wanted there are going to be selection of sessions to view on ESA’s site, for example, you can see the opening session here.

Not only do events like this gives you to a fantastic chance learn about what’s happening across the EO community, but they also give you the opportunity to catch up with old friends. I am looking forward to the rest of the week!

Is the remote sensing market an urban legend?

Yeti footprints

Yeti footprints on ice – erectus/123RF Stock Photo

The remote sensing/Earth observation (EO) market is like the Yeti or the Loch Ness Monster – there are plenty of people out there who tell you it exists, but very few companies have seen it with their own eyes!

We work in a fast growing and expanding industry, at least according to the myriad of reports that regularly drop into our inboxes. For example, over the last few weeks we’ve had press releases such as :-

With all this growth everything in the remote sensing/EO industry is fantastic, right? Well, no actually! Despite the report announcements, lots of companies within the industry are struggling to locate this valuable market.

Historically, a lot of funding was provided by governments and space agencies in the form of grants or tenders to promote the use, and uptake, of EO data, which enabled companies to develop and grow. Whilst such sources of funding are still available; the maturing of the industry coupled with the global economic slowdown is starting to constrict this revenue stream, forcing more and more EO companies out in the commercial world looking for the fabled billion dollar market. This development is currently being supported by venture capital as the growth forecasts are encouraging investment, but how many of these companies will be able to transition into profit making businesses?

The Holy Grail for everyone is a reliable, consistent and expanding market for EO products and services, something that few businesses in our sector have successfully found. There are a variety of reasons why the market feels like an urban legend, including:

  • Lack of knowledge on the products wanted leading to supplier led, rather than consumer led, product development.
  • Lack of an existing market meaning that EO companies need to work hard on advertising to tell possible customers they exist and the benefits they can offer.
  • Monopolistic behaviour of governments/space agencies. These bodies have spent large sums to launch satellites and need to demonstrate value for money. For example, the European Commission’s Copernicus Programme recently announced its intention to develop agriculture products from Sentinel data. Rather than developing the market, this could potentially destroy the market for existing EO companies.

It’s clear that to get proof of a remote sensing/EO market, companies need to develop value for money products that customers want, demonstrate the benefits of satellite data as an information source and stand out from the other legend hunters!

Here at Pixalytics we’re in the process of packing our data, securing our satellite links and checking our geo-referenced maps, ready to set out onto our journey in search of the fabled market. To date, our businesses has focussed on bespoke specialised products for individual customers and now we’re also hoping to develop more standard products that can be processed on demand, or made available from a pre-processed archive.

Of course we don’t have all the answers of where to find the customers, what the right products are or the best way of making letting people know we exist and we can help them. Although having seen the cost of these industry reports, we’re starting to think that writing, and selling, remote sensing/EO market reports is where the real money is!

Over the next few months, we’ll use this blog to tell you about our journey, the mistakes we make and what we learn. As we get a glimpses into the market we’ll put it up here, although it might be grainy and indistinguishable – but then aren’t all urban legend pictures!

Sentinel-3 Sets Sail

Artist's view of Sentinel-3. Image courtesy of ESA–Pierre Carril.

Artist’s view of Sentinel-3. Image courtesy of ESA–Pierre Carril.

At 17.57 GMT yesterday (16th February 2016) Sentinel-3 set sail from the Plesetsk Space Centre in Russia, heading for its 814 km sun-synchronous low Earth orbit. Like all the other Sentinel launches, we were at home watching the live feed!

This is the third Sentinel launch of the European Commission’s Copernicus Programme, following Sentinel-1 and 2. Sentinel-3, like its predecessors, will be part of a twin satellite constellation with Sentinel-3B’s launch expected to be in 2017.

Sentinel-3 carries four scientific instruments:

  • Sea and Land Surface Temperature Radiometer (SLSTR) will measure temperatures of both the sea and land, to an accuracy of better than 0.3 K. This instrument has 9 spectral bands with a spatial resolution of 500 m for visible/near-infrared wavelengths and 1 km for the thermal wavelengths; and has swath widths of 1420 km at nadir and 750 km looking backwards. It’s worth noting that two thermal infrared spectral wavebands are optimised for fire detection, providing the fire radiative power measurement.
  • Ocean and Land Colour Instrument (OLCI) has 21 spectral bands (400–1020 nm) focussed on ocean colour and vegetation measurements. All bands have a spatial resolution of 300 m with a swath width of 1270 km.
  • Synthetic Aperture Radar Altimeter (SRAL) which has dual frequency Ku and C bands. It offers 300 m spatial resolution after SAR processing, and is based on the instruments from the CryoSat and Jason missions. This will be first satellite altimeter to provide 100% coverage of the Earth’s surfaces in SAR mode.
  • Microwave Radiometer (MWR) dual frequency at 23.8 & 36.5 GHz, it is used to derive atmospheric column water vapour measurements for correcting the SRAL instrument.

The scientific instruments are supported by four positioning/navigation instruments to ensure the satellite maintains its precise orbit.

Sentinel-3 will mainly be focussing on ocean measurements and will include the measurement of sea-surface height (similar to the recently launched Jason-3); however it will also measure sea surface temperature, ocean colour, surface wind speed, sea ice thickness and ice sheets. Whereas over land the satellite will provide indices of vegetation, measuring the height of rivers and lakes and help monitor wildfires.

Sentinel-3 is a very exciting satellite for us, as the data and products it will produce are very much within the wheelhouse of the services that Pixalytics offers. Sam’s background is in ocean colour, she’s world renown for atmospheric correction research and we offer a variety of agritech services including vegetation indices. You can probably now see why we’re so excited!

The satellite is currently in its commissioning phases where ESA tests the data produced by the sensors. This is undertaken in conjunction with a group of users, and Pixalytics is one of them! This phase is expected to last five months, after which the satellite will be transferred to Eumetsat and the data should be released.

Like all the data from the Copernicus programme, it will be offered free of charge to users. This will challenge organisations, like us, to see what innovative services we can offer with this new data stream. Exciting times ahead!

Reprocessing Data Challenges of Producing A Time Series

August 2009 Monthly Chlorophyll-a Composite; data courtesy of the ESA Ocean Colour Climate Change Initiative project

August 2009 Monthly Chlorophyll-a Composite; data courtesy of the ESA Ocean Colour Climate Change Initiative project

Being able to look back at how our planet has evolved over time, is one of the greatest assets of satellite remote sensing. With Landsat, you have a forty year archive to examine changes in land use and land cover. For in situ (ground based) monitoring, this is something that’s only available for a few locations, and you’ll only have data for the location you’re measuring. Landsat’s continuous archive is an amazing resource, and it is hoped that the European Union’s Copernicus programme will develop another comprehensive archive. So with all of this data, producing a time series analysis is easy isn’t it?

Well, it’s not quite that simple. There are the basic issues of different missions having different sensors, and so you need to know whether you’re comparing like with like. Although data continuity has been a strong element of Landsat, the sensors on Landsat 8 are very different to those on Landsat 1. Couple this with various positional, projection and datum corrections, and you have lots of things to think about to produce an accurate time series. However, once you’ve sorted all of these out and you’ve got your data downloaded, then everything is great isn’t it?

Well, not necessarily; you’ve still got to consider data archive reprocessing. The Space Agencies, who maintain this data, regularly reprocess satellite datasets. This means that the data you downloaded two years ago, isn’t necessarily the same data that could be downloaded today.

We faced this issue recently as NASA completed the reprocessing of the MODIS Aqua data, which began in 2014. The data from the MODIS Aqua satellite has been reprocessed seven times, whilst its twin, Terra, has been reprocessed three times.

Reprocessing the data can include changes to some, or all, of the following:

  • Update of the instrument calibration, to take account of current knowledge about sensor degradation and radiometric performance.
  • Appyling new knowledge, in terms of atmospheric correction and/or derived product algorithms.
  • Changes to parallel datasets that are used as inputs to the processing; for example, the meteorological conditions are used to aid the atmospheric correction.

Occasionally, they also change the output file format the data is provided in; and this is what has caught us out. The MODIS output file format has changed from HDF4 to NetCDF4 with the reason being that NetCDF is a more efficient, sustainable, extendable and interoperable data file format. A change we’ve known about for a long time, as it resulted from community input, but until you get the new files you can’t check and update your software.

We tend to use a lot of Open Source software, enabling our clients to carry on working with remote sensing products without having to invest in expensive software. The challenge is that it takes software provider time to catch up with the format changes. Hence, the software is unable to load the new files or the data is incorrectly read e.g., comes in upside down. Sometimes large changes, mean you may have to alter your approach and/or software.

Reprocessing is important, as it improves the overall quality of the data, but you do need to keep on top what is happening with the data to ensure that you are comparing like with like when you analyse a time series.