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Agriculture with
the view from above

How satellite data ensure better yields

The Earth is supposed to nourish a continuously increasing number of people. At the same time, there is a growing conscience and the wish for “healthy” food, sustainably and environmentally friendly cultivated and harvested. Fertiliser and pest control are supposed to be used sparingly or better: not to be used at all – but this in turn will reduce the yields. A dilemma?

No, since there are some other options for optimising yields without stressing the soils beyond all measures: the control of irrigation and drainage, growth monitoring, and the increasingly sparing, more precise use of fertilisers, for example. Or bringing in the yield with a precision down to one metre.

Earth observation via satellites renders that possible and delivers data, images, and information to farmers helping them to make more economical use of their land. In addition, research is conducted on how agriculture can function anywhere – even in space. This enables agriculture in new places, without additional land consumption.

Precision farming needs satellite data. Fields are different. In some places, the soil is more fertile and needs less fertiliser, in some places, the water supply is better, on another field, plants inherently ripen faster.

In today’s precision farming, thanks to satellite navigation data farm machinery detects precisely how much fertiliser has been applied in what places and how rich the harvest was in each area of the field so that optimisation measures can be taken for the next year.

DLR is working on automated monitoring of soil condition and plant growth with radar data, among others within the envisaged satellite project Tandem-L, to enable farmers to respond earlier to weather and climate changes. The image shows radar data from Wallerfing in Bavaria.

Yield estimates, maps of crop sequencing, plant parameters – for all this, an app made in Germany is available, supported by DLR: AGRO-DE. This project enables easy use of processed remote sensing data by farmers for the first time. The data mainly originate from the Sentinel-2 satellite of the European Earth observation programme Copernicus.

The image shows a hyperspectral cube of a forested area: each pixel contains a detailed reflection spectrum.

How plants feel: So-called “hyperspectral” images elucidate biochemical and biophysical parameters of plant growth. For example, they make the chlorophyll and water content visible. The German satellite EnMAP will acquire such data from space in future. This enables improved field crop classification, better yield forecasts, and a more precise control of plant growth.

The image shows the growth of rice on fields at the Turkish-Greek border in the space of time from July to September 2012.

How does rice grow? On which surfaces does rice grow faster? In which places would more or less fertilisation be needed? Where is cultivation not worthwhile? The growth of rice plants can be monitored by the DLR satellite mission TanDEM-X – with a precision in the centimetre range.

If fields could talk: wet fields, low yield. From space you can detect (e.g. partly with data of the German RapidEye satellite, the European Sentinel satellites, or, in future, with the German EnMAP satellite) where the biomass of a field is below average. In this way, for example, negative effects of too wet soil become visible and can give valuable advice to farmers on whether a drainage system could improve the yield. Satellite data also precisely show which plants grow how well and fast. This information enhances harvest forecasts and informs you about places you possibly might need to seed again just in time. ESA is funding the supplier talkingfields which is a joint project of Vista GmbH, PC-Agrar GmbH, Land-Data Eurosoft and LMU Munich.

From agriculture to farming in space

How much nutrition can be yielded on 12.5 square metres within nine and a half months? In an ordinary greenhouse: 400 kilogrammes of tomatoes. And in the Antarctic, in dark winter? Without sunlight? With artificial light only and with energy consumption being as low as possible? Even there, an astonishing 268 kilogrammes of cucumbers, salad and tomatoes are feasible. This is proven by the DLR project EDEN-ISS at the Antarctic station Neumayer III of the Alfred Wegener Institute, where the plants grow in a nutrient solution without soil. For the overwintering team at the station, fresh vegetables were a mood elevator since normally fresh food is not served there. Something like that will someday also apply to inhabitants of the Moon. They will have to cultivate foodstuff themselves on site to avoid dependency on deliveries from Earth.

For them, DLR developed a foldable 30-square metre version of this greenhouse. It is sufficiently small to be carried as payload on a launcher. This new type of foodstuff cultivation in self-sufficient containers is also very interesting for other cold regions as well as for deserts and cities.

Methane: highly harmful, underexplored

Methane is 25 times as harmful for the climate as CO₂ – and its content in the atmosphere is increasing rapidly, for which humans are directly or indirectly responsible: rice fields, cattle industry, mining, rubbish dumps, energy production, or defreezing of permafrost areas. All these are sources of methane. In addition, there are natural sources like swamps, fenlands, termites, forests, and the seas. The knowledge on the total extent of the problem is still fragmentary today – but we learn something new very quickly thanks to satellite observation.

This is where satellites will detect methane

Fire and ice: defreezing permafrost soils present a big problem. Since the Pleistocene, biomaterials have been freezing there – and are defreezing now because of the human-made global warming. Melting water puddles are generated, at the bottom of which bacteria decompose old plant residues. In this way, methane is produced – lots of it. From space, we will be able for the first time to quantify the total extent of this source.

Methane from the fenlands: fenland plants take in CO₂ from the air when growing. When they die back, the carbon keeps joined. However, methane is generated through biological decomposition processes in the fenlands that fumes. At the surface, fenland moss grows that lives in symbiosis with bacteria: the bacteria feed on methane; the moss prefers the residual CO₂. And how does that affect the climate? We will know soon. Yet today it is certain: drained fenlands are harmful to the climate in any case, since under the influence of oxygen (i.e. when the water is gone), CO₂ is being produced.

Methane from the seas: in 2014, 550 hitherto unknown sources of methane were detected on the US east coast, mostly in a depth of 250–600 metres. Practically, the methane is joint there as frozen methane ice. However, the methane ice is melting due to seasonal or long-term warming, and the methane gas rises to the surface. This phenomenon has been hardly researched on and is presumably happening in many places. Hopefully, thanks to satellites, we will get to know more details soon in this field as well.

Methane from abandoned coal mines: low oxygen content, organic material, and microbes – the “breeding ground“ for methane. It also finds its way into the atmosphere from the vent shafts of abandoned tunnels. When shafts with a high output of methane will be identified from space soon, the gas can be contained, combusted, and used for energy production (this is already being done in some places, for example in Herne). The CO₂ generated in this process is considerably less harmful to the climate than unburned CH₄.

LIDAR: technology from space flight

With the aid of the LIDAR technology (LIDAR = Light Detecting and Ranging), the MERLIN satellite will detect methane. Laser light is emitted, reflected or scattered by an object (gas cloud, or soil), and the light returning to the LIDAR instrument is registered. By measuring the time elapsed between transmission and reception of the laser pulse, the distance between the LIDAR instrument and the reflecting object can be determined.

The wave length of the emitted and returned light will reveal the composition and thus the type of the reflecting object – for example methane.

In space flight, LIDAR was first on board in 1971 for the Apollo 15 moon landing mission (the first with a lunar rover). With its help, a map of the lunar surface was drawn up.

LIDAR in everyday life

Inspection of natural gas pipelines: The same technology that is embedded in MERLIN – remote sensing of methane by means of infrared laser light – is already on the move on board a helicopter. In this way, even the smallest leakages on natural gas pipelines can be detected and repaired at a very early stage. Instead of combing and inspecting eight kilometres of pipeline a day, up to 50 kilometres per hour can be inspected from a helicopter equipped with the CHARM system (CH₄ Airborne Remote Monitoring). It was developed by Adlares GmbH in cooperation with the German Aerospace Center (DLR) on behalf of Open Grid Europe.

LIDAR in the car: Are self-driving cars the trend of the future and the guarantor for smooth traffic flow? Many companies currently bank on that. There are two different approaches, both based on LIDAR.
Approach no. 1: LIDAR on every car to scan the environment in real time.
Approach no. 2: LIDAR for mapping. The map service HERE measures streets by LIDAR vehicles with a precision of two centimetres. Thanks to this data, forthcoming autonomous vehicles will need less measuring technology on board.

LIDAR on the roadside: There might be some people who do not exactly like the achievements from space flight: speeders, for example. When the police are standing on the roadside with a laser gun, they use LIDAR technology to measure the speed. On the contrary, craftsmen and do-it-yourselfers highly appreciate LIDAR, as, for example, included in the small handheld range finders that replace the tedious folding out of the folding metre stick.

The pilot’s anxiety at the microburst: “Microbursts” are strong winds near the ground, a big threat during the landing of an aircraft. The company Leosphere offers compact LIDAR systems for airports that precisely detect winds in a circuit of ten kilometres. For more safety in aviation.

A “backup” for buildings: Natural disasters, wars, or simply the ravages of time do not spare even World Cultural Heritage sites. The CyArk project aims to measure 500 World Cultural Heritage sites by LIDAR technology and to create 3D backups – this is called “digital preservation”. In case of disaster, it would at least be possible to reconstruct these sites in full detail. Or you simply visit them on the monitor at home. Pompeii, for example, which sadly goes more and more ruinous.

LIDAR in archaeology: The temples of Angkor Wat in Cambodia are huge, 800-year old, well preserved constructions – despite the housing consisting of clay huts that are completely gone except for some small hills. However, they could not be detected for a long time in the heavily vegetated rain forest. Until researchers flew over the region with a helicopter – and were able to recognise and map the housing structure for the first time thanks to air-borne LIDAR measurement. The sensation: Angkor Wat is four times larger than previously assumed. The bonus: the discovery of Mahendraparvata, the lost town of the first king of the Khmer.

CO₂ and CH₄:
the main causes of climate change

Global warming is speeding up as never experienced before in Earth’s history. For the first time, humans are the main cause: since mid of the 19th century, an ever increasing amount of – man-made – greenhouse gas has ascended into the atmosphere. This is the reason why less heat can escape from Earth to space. The two most important greenhouse gases are CO₂ with 72 per cent (carbon dioxide, mainly from coal-fired power stations, industry, and road traffic) and CH₄ (methane) with 18 per cent. However, methane is 25 times more harmful to the climate than CO₂.

MERLIN: a Franco-German contribution to overcome the climate change

The MERLIN mission has been the first Franco-German project in the field of Earth observation since the year 1994. It has been agreed upon by both nations within the framework of the Franco-German Ministerial Council in February 2010. Taking this step, the two largest space- faring nations in Europe decided to make a perceptible contribution to research on the causes of climate change through their space agencies CNES and DLR.

Permafrost soils are defreezing; fenlands are emitting gas – with MERLIN watching. The Franco-German mini-satellite MERLIN (Methane Remote Sensing LIDAR Mission) is supposed to monitor methane in the Earth’s atmosphere over a period of three years starting in 2024. With the aid of a LIDAR instrument (Light Detecting and Ranging), it will trace and monitor greenhouse gas in the Earth’s atmosphere from an altitude of about 500 kilometres. The aim is to draw up a world map of methane concentrations – to precisely identify the sources and the places in which methane is withdrawn from the atmosphere. First methane data from the troposphere are already delivered by the Copernicus satellite Sentinel-5P, although not with active LIDAR technology but with passive sensors.

LIDAR on board

MERLIN will be equipped with a further developed LIDAR system. It is capable of measuring the quantity and distribution of methane in the Earth’s atmosphere, during the day, at night, or straight through thin cirrus clouds. For measuring the concentration of gases, light pulses are emitted on two wave lengths (“colours”) close to each other. One of these wave lengths is absorbed by the trace gas searched for, the other is not. From the difference of the two signals scattered back from the ground to the satellites, the methane concentration can be determined very precisely.

The satellite will once orbit the entire Earth within a month and search for natural and man-made sources of methane. 50 times per second, the laser beam is transmitted to Earth and received. The measuring values recorded by MERLIN can be re-calculated by scientists with the help of data on wind speeds and directions to draw up global methane “movement maps“.

Technological development from Germany

The technologies for the LIDAR instrument to be installed on MERLIN come from German industrial enterprises and research institutions. Within different projects funded by German Space Agency at DLR and ESA, technologies for future LIDAR instruments have been developed and tested by, among others: Airbus Defence and Space (Ottobrunn), SpaceTec GmbH (Immenstaad), Hoerner & Sulger (Schwetzingen) as well as by the Fraunhofer Institute for Laser Technology (Aachen) and the DLR Institute of Atmospheric Physics (Oberpfaffenhofen). The programmes for processing MERLIN data as well as the control of the MERLIN instrument are developed by the DLR Remote Sensing Technology Institute (Oberpfaffenhofen) and SciSYS GmbH (Bochum).

On the German side, the scientific responsibility for the instrument is assumed by the LIDAR department of the DLR Institute of Atmospheric Physics (IPA) in Oberpfaffenhofen. It already develops and operates aircraft-based LIDAR systems for measuring e.g., wind speed, water steam, methane, or the carbon dioxide content of the atmosphere. The methane and carbon dioxide LIDAR CHARM-F developed by the IPA is based on the same measurement principle as MERLIN. It is deployed on the DLR research aircraft HALO thus ensuring that this measuring method for the MERLIN mission can be tested beforehand.

Strong cooperation with France

The French space agency CNES will be in charge of the entire system and the satellite bus as well as the operation of the satellite and the launcher. As a platform for this purpose, CNES is developing the so-called MYRIADE Evolution Platform. So, the MERLIN platform will become the prototype for a new series of future high-performance minisatellites. A scientific concept study and a technical feasibility study have been successfully conducted jointly by CNES and German Space Agency at DLR in the years from 2010 to 2012. In the next step, a technical design for the satellite system will be drawn up. The launch of MERLIN is scheduled for 2024. Both nations jointly see to the payload ground segment and the scientific evaluation of the methane data.

Launch	2024
Orbit altitude	approx. 500 km
Type of orbit	low polar sun-synchronous orbit
Satellite mass	430 kg
Satellite size	approx. 160 x 450 x 160 cm with unfolded solar panels
Satellite bus	MYRIADE Evolution (from France)
Instrument	Methane LIDAR (from Germany)
Measurement principle	Integrated Path Differential Absorption (IPDA)
Instrument mass	approx. 150 kg
Energy consumption LIDAR	approx. 150 W
Laser wave lengths	1645.552 nm (on)/1645.846 nm (off)
Pulse energy laser	9 mJ
Pulse rate laser	approx. 20 Hz (double pulse)
Data rate	approx. 300 kbps
Data volume per orbit	approx. 1,6 Gbit
Mission duration	3 years

The CO2M satellites: humans or nature – who causes carbon dioxide and methane, and where?

How are carbon dioxide and methane globally distributed? Where are they emitted and to what extent? Where are the hot spots? Where do plants act particularly strongly as “hollows” through photosynthesis? This is what the ESA satellites of the CO2M mission are supposed to investigate starting 2025. The resolution of the satellite images will be sufficiently high to analyse even gas plumes of individual power plants or industrial plants. In this way, we will get a clear picture showing which greenhouse gases are anthropogenic and to what extent – these are unsurpassed data worldwide that never existed before.

Key preparatory work for this mission comes from research by Bremen University. The new satellites will be based on the CarbonSat concept of the Institute for Environmental Physics (IUP). The scientists will continue to be committed to the development of the CO2M system. The CarbonSat concept has been supported by DLR.

The funding for the construction of the CO2M satellites is provided by the Copernicus programme.

Agriculture with the view from above