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!

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!

Ocean Colour Cubes

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

It’s an exciting time to be in ocean colour! A couple of weeks ago we highlighted the new US partnership using ocean colour as an early warning system for harmful freshwater algae blooms, and last week a new ocean colour CubeSat development was announced.

Ocean colour is something very close to our heart; it was the basis of Sam’s PhD and a field of research she is highly active in today. When Sam began studying her PhD, Coastal Zone Color Scanner (CZCS) was the main source of satellite ocean colour data, until it was superseded by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) that became the focus of her role at Plymouth Marine Laboratory.

Currently, there are a number ocean colour instruments in orbit:

  • NASA’s twin MODIS instruments on the Terra and Aqua satellites
  • NOAA’s Visible Infrared Imager Radiometer Suite (VIIRS)
  • China’s Medium Resolution Spectral Imager (MERSI), Chinese Ocean Colour and Temperature Scanner (COCTS) and Coastal Zone Imager (CZI) onboard several satellites
  • South Korea’s Geostationary Ocean Color Imager (GOCI)
  • India’s Ocean Colour Monitor on-board Oceansat-2

Despite having these instruments in orbit, there is very limited global ocean colour data available for research applications. This is because the Chinese data is not easily accessible outside China, Oceansat-2 data isn’t of sufficient quality for climate research and GOCI is a geostationary satellite so the data is only for a limited geographical area focussed on South Korea. With MODIS, the Terra satellite has limited ocean colour applications due to issues with its mirror and hence calibration; and recently the calibration on Aqua has also become unstable due to its age. Therefore, the ocean colour community is just left with VIIRS; and the data from this instrument has only been recently proved.

With limited good quality ocean colour data, there is significant concern over the potential loss of continuity in this valuable dataset. The next planned instrument to provide a global dataset will be OLCI onboard ESA’s Sentinel 3A, due to be launched in November 2015; with everyone having their fingers crossed that MODIS will hang on until then.

Launching a satellite takes time and money, and satellites carrying ocean colour sensors have generally been big, for example, Sentinel 3A weighs 1250 kg and MODIS 228.7 kg. This is why the project was announced last week to build two Ocean Colour CubeSats is so exciting; they are planned to weigh only 4 kg which reduces both the expense and the launch lead time.

The project, called SOCON (Sustained Ocean Observation from Nanosatellites), will see Clyde Space, from Glasgow in the UK, will build an initial two prototype SeaHawk CubeSats with HawkEye Ocean Colour Sensors, with a ground resolution of between 75 m and 150 m per pixel to be launched in early 2017. The project consortium includes the University of North Carolina, NASA’s Goddard Space Flight Centre, Hawk Institute for Space Sciences and Cloudland Instruments. The eventual aim is to have constellations of CubeSats providing a global view of both ocean and inland waters.

There are a number of other planned ocean colour satellite launches in the next ten years including following on missions such as Oceansat-3, two missions from China, GOCI 2, and a second VIIRS mission.

With new missions, new data applications and miniaturised technology, we could be entering a purple patch for ocean colour data – although purple in ocean colour usually represents a Chlorophyll-a concentration of around 0.01 mg/m3 on the standard SeaWiFS colour palette as shown on the image at the top of the page.

We’re truly excited and looking forward to research, products and services this golden age may offer.

Ocean Colour Partnership Blooms

Landsat 8 Natural Colour image of Algal Blooms in Lake Erie acquired on 01 August 2014. Image Courtesy of NASA/USGS.

Landsat 8 Natural Colour image of Algal Blooms in Lake Erie acquired on 01 August 2014. Image Courtesy of NASA/USGS.

Last week NASA, NOAA, USGS and the US Environmental Protection Agency announced a $3.6 million partnership to use satellite data as an early warning system for harmful freshwater algae blooms.

An algae bloom refers to a high concentration of micro algae, known as phytoplankton, in a body of water. Blooms can grow quickly in nutrient rich waters and potentially have toxic effects. Shellfish filter large quantities of water and can concentrate the algae in their tissues, allowing it to enter the marine food chain and potentially causing a risk to human consumption. Blooms can also contaminate drinking water. For example, last August over 40,000 people were banned from drinking water in Toledo, Ohio, after an algal bloom in Lake Erie.

The partnership will use the satellite remote sensing technique of ocean colour as the basis for the early warning system.  Ocean colour isn’t a new technique, it has been recorded as early as the 1600s when Henry Hudson noted in his ship’s log that a sea pestered with ice had a black-blue colour.

Phytoplankton within algae blooms are microscopic, some only 1,000th of a millimetre in size, and so it’s not possible to see individual organisms from space. Phytoplankton contain a photosynthetic pigment visible with the human eye, and in sufficient quantities this material can be measured from space. As the phytoplankton concentration increases the reflectance in the blue waveband decreases, whilst the reflectance in the green waveband increases slightly. Therefore, a ratio of blue to green reflectance can be used to derive quantitative estimates of the concentration of phytoplankton.

The US agency partnership is the first step in a five-year project to create a reliable and standard method for identifying blooms in US freshwater lakes and reservoirs for the specific phytoplankton species, cyanobacteria. To detect blooms it will be necessary to study local environments to understand the factors that influence the initiation and evolution of a bloom.

It won’t be easy to create this methodology as inland waters, unlike open oceans, have a variety of other organic and inorganic materials suspended in the water through land surface run-off, which will also have a reflectance signal. Hence, it will be necessary to ensure that other types of suspended particulate matter are excluded from the prediction methodology.

It’s an exciting development in our specialist area of ocean colour. We wish them luck and we’ll be looking forward to their research findings in the coming years.

Goodbye HICO, Hello PACE – Ocean Colour’s Satellite Symmetry

HICO™ Data, image of Hong Kong from the Oregon State University HICO Sample Image Gallery, provided by the Naval Research Laboratory

HICO™ Data, image of Hong Kong from the Oregon State University HICO Sample Image Gallery, provided by the Naval Research Laboratory

Ocean colour is the acorn from which Pixalytics eventually grew, and so we were delighted to see last week’s NASA announcement that one of their next generation ocean colour satellites is now more secure with a scheduled launched for 2022.

Unsurprisingly the term ocean colour refers to the study of the colour of the ocean, although in reality it’s a name that includes a suite of different products, with the central one for the open oceans being the concentration of phytoplankton. Ocean colour is determined by the how much of the sun’s energy the ocean scatters and absorbs, which in turn is dependent on the water itself alongside substances within the water that include phytoplankton and suspended sediments together with dissolves substances and chemicals. Phytoplankton can be used a barometer of the health of the oceans; in that phytoplankton are found where nutrient levels are high and oceans with low nutrients have little phytoplankton. Sam’s PhD involved the measurement of suspended sediment coming out of the Humber estuary back in 1995, and it’s remained an active field of her research for the last 20 years.

Satellite ocean colour remote sensing began with the launch of NASA’s Coastal Zone Colour Scanner (CZCS) on the 24th October 1978. It had six spectral bands, four of which were devoted to ocean colour, and a spatial resolution of around 800m. Despite only having an anticipated lifespan of one year, it operated until the 22nd June 1986 and has been used as a key dataset ever since. Sadly, CZCS’s demise marked the start of a decade gap in NASA’s ocean colour data archive.

Although there were some intermediate ocean colour missions, it was the launch of the Sea-viewing Wide Field-of-view (SeaWiFS) satellite that brought the next significant archive of ocean colour data. SeaWiFS had 8 spectral bands optimized for ocean colour and operated at a 1 km spatial resolution. One of Sam’s first jobs was developing a SeaWiFS data processor, and the satellite collected data until the end of its mission in December 2010.

Currently, global ocean colour data primarily comes from either NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the twin Aqua and Terra satellites, or the Visible Infrared Imaging Radiometer Suite (VIIRS) which is on a joint NOAA / NASA satellite called Suomi NPP. MODIS has 36 spectral bands and spatial resolution ranging from 250 to 1000 m; whilst VIIRS has twenty two spectral bands and a resolution of 375 to 750 m.

Until recently, there was also the ONR / NRL / NASA Hyperspectral Imager for the Coastal Ocean (HICO) mission on-board the International Space Station. It collected selected coastal region data with a spectral resolution range of 380 to 960nm and 90m spatial resolution. It was designed to collect only one scene per orbit and has acquired over 10,000 such scenes since its launch. However, unfortunately it suffered during a solar storm in September 2014. Its retirement was officially announced a few days ago with the confirmation that it wasn’t possible to repair the damage.

In the same week we wave goodbye to HICO, NASA announced the 2022 launch of the Pre-Aerosol and ocean Ecosystem (PACE) mission in a form of ocean colour symmetry. PACE is part of the next generation of ocean colour satellites, and it’s intended to have an ocean ecosystem spectrometer/radiometer called built by NASA’s Goddard Space Flight Centre and will measure spectral wavebands from ultraviolet to near infrared. It will also have an aerosol/cloud polarimeter to help improve our understanding of the flow, and role, of aerosols in the environment.

PACE will be preceded by several other missions with an ocean colour focus including the European Sentinel-3 mission within the next year; it will have an Ocean and Land Colour Instrument with 21 spectral bands and 300 m spatial resolution, and will be building on Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument. Sentinel-3 will also carry a Sea and Land Surface Temperature Radiometer and a polarimeter for mapping aerosols and clouds. It should help to significantly improve the quality of the ocean colour data by supporting the improvement of atmospheric correction.

Knowledge the global phytoplankton biomass is critical to understanding the health of the oceans, which in turn impacts on the planet’s carbon cycle and in turn affects the evolution of our planet’s climate. A continuous ocean colour time series data is critical to this, and so we are already looking forward to the data from Sentinel-3 and PACE.

Home from Hawaii

I got back to a ‘cold’ UK on Saturday afternoon after spending last week at Ocean Sciences 2014.  It was a fantastic conference with over 5,600 attendees.  My scientific highlights were:

The Surface Ocean Layer Atmosphere Study (SOLAS) session on Monday where speakers presented research on the sea surface microlayer (the top 1 mm of the ocean); this layer is important so we can understand the transfer of compounds, such as carbon dioxide, and particles from the ocean to the atmosphere and vice versa that are critical to our interpretation of the climate.

On Tuesday afternoon it was the Optics and Light in the Particle-Laden Coastal Ocean session, with presentations focused on understanding the acoustic and optical signatures of particles, including their shape, from multi-angular measurements and Lidar (laser) profiling of a phytoplankton bloom.

My key session was obviously Optical Remote Sensing of Freshwater, Estuarine and Coastal Environments on Wednesday. I gave a presentation on Multi-Sensor Ocean Colour Atmospheric Correction for Time-Series Data.  Atmospheric correction is the removal of the atmosphere’s signal from data so only the water-leaving radiance signal is left; it allows data to be compared between days irrespective of the weather conditions of that day – so an image taken on a hazy day will look like it was taken on a clear day.

HICO™ Data, image of Hong Kong from the Oregon State University HICO Sample Image Gallery, provided by the Naval Research Laboratory

HICO™ Data, image of Hong Kong from the Oregon State University HICO Sample Image Gallery, provided by the Naval Research Laboratory

Other interesting talks from this session included Tiit Kutser’s presentation on comparing in-situ measurements with MERIS data for dissolved organic carbon and iron concentrates in Lake Malaren in Sweden, Keping Du’s retrieval algorithm for phycocanian, a pigment within cyanobacteria, within Taithu lake in China, Heidi Dierssen’s optics of seagrass for remote sensing and I also really enjoyed my mentee Guangming Zheng’s presentation on suspended sediment within Chesapeake Bay, off the west coast of America – this took me back to my PhD that focussed on the suspended sediment plume from the River Humber.

Finally, there were great presentations by Curt Davis and Nick Tufillaro on the Hyperspectral Imager for the Coastal Ocean (HICO) mission. It’s an experimental mission that’s designed to sample the coastal ocean; one 50 x 200 km scene per orbit at a spatial resolution of around 90 m. The image on the right shows a HICO example.

On top of these oral sessions, I also spent time in the exhibition, poster sessions and some of the evening events.  My last event on the Thursday evening was about getting involved in the European Commission’s Horizon 2020 Research programme – so if anyone needs an Earth Observation specialist partner for their bid, get in touch!

Settling in at the 2014 Ocean Sciences Meeting

My beach reading spot!

My beach reading spot!

I’m feeling a bit guilty writing this with everyone in the UK still experiencing the wet wintery weather, as I’m in Honolulu, Hawaii at the 2014 Ocean Sciences Meeting. I arrived around midnight last Friday and spent Saturday morning relaxing on the edge of Waikiki beach looking out to sea, watching people go by and reading a book; and I’d recommend Mr Penumbra’s 24-Hour Bookstore by Robin Sloan as a great story if you’re interested technology, cryptography or old books!

Ocean Sciences 2014 opened with a welcome reception on Sunday evening and an interesting key note address by Polynesian explorer Elizabeth Kapu’uwailani Lindsey entitled ‘Bringing the Wisdom of the “Elders” Together with Modern Science for the Future of the Environment’.  During the evening I did try to try track down the three people I’m mentoring at this conference – Elaine, Guangming and Navid. However, as there are over 5,000 attendee’s there were a lot of people to search through!

I finally sat down with my mentees at breakfast on Monday morning. The meeting’s mentoring program is an interesting concept designed to help novice conference attendees get the most value out of their experience.

Yesterday we met up at Navid’s poster to discuss his work on modelling internal waves, at lunch we discussed Elaine’s poster on climate data services and tomorrow Guangming is presenting a talk on the turbidity maximum in Chesapeake Bay in the same session as I’m presenting my ocean colour atmospheric correction work. This is a great element about going to scientific conferences, meeting people to discuss their research and interests. Some are new acquaintances and some I’ve known for a long time. My first time attendance at this meeting (also in Hawaii) was in 2006.

Today I’ve also been to a session on particles in the coastal ocean, and this evening it was Philanthropic Investment in Ocean Research. Tomorrow I’ve got a really busy day as I’m speaking, I’ll give you an update on the second half of the conference next week!

A little addendum I noticed while finishing this post is that Satellite Applications Catapult yesterday published its response to UK Space Innovation and Growth Strategy Space Growth Action Plan. I’ve downloaded it, and it will form part of my next beach reading session!