LIVE: TanDEM-X launch - June 21, 2010

[tonthomas]

Contact with Troll station worked.

Thomas

[Lewis007]

Launch pic posted at the DLR site:

[Lewis007]

Here's another launch pic (after staging), from the DLR TanDEM-X blog page.

[jacqmans]

Converted Russian ICBM Takes German Satellite into Orbit

21.06.2010


A converted Russian intercontinental ballistic missile took Germany's TanDEM-X satellite into orbit on Monday, a military spokesman said.
The RS-20B carrier rocket lifted off from the Baikonur space center in Kazakhstan at 6:14 Moscow time [2:14 GMT].
This is the 16th launch of an international satellite under the Dnepr program involving Russia, Ukraine, Kazakhstan and Turkmenistan, which converts RS-20 ICBMs (classified by NATO as the SS-18 Satan) into carrier rockets to put satellites into low Earth orbit. Around 50 satellites have been put into orbit so far.
"The RS-20B rocket took the TanDEM-X satellite into orbit," Col. Vadim Koval said.
The 1,350-kg TanDEM-X satellite, with a life span of five years will survey Earth's land surface several times during its mission. The primary objective of the mission is to generate a consistent global digital elevation model of an unprecedented accuracy.
Russian-Ukrainian joint venture Kosmotras uses launch pads at the Baikonur space center in Kazakhstan and Russia's Strategic Missile Forces facilities equipped for RS-20 launches.
The RS-20 is the most powerful ICBM in the world. It was first launched in 1973 and is still in service with Russia's Strategic Missile Forces.

http://www.roscosmos.ru/

[jacqmans]

The Earth in 3D - German radar satellite TanDEM-X launched successfully
21 June 2010

Germany's second Earth observation satellite, TanDEM-X, was launched successfully on 21 June 2010 at 04:14 Central European Summer Time (CEST, at 08:14 local time) from the Baikonur Cosmodrome in Kazakhstan. Atop a Russian Dnepr rocket, the satellite, weighing more than 1.3 tons and five metres in length, started its journey into orbit. At 4.45 CEST first signal was received via Troll ground station in the Antarctic.

The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) manages TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) via its ground segment, and is responsible for mission operations and for generating and utilising the scientific data. "TanDEM-X is a key German project and will provide us with a homogeneous 3D elevation model of the Earth which will be an indispensable aid for a great many scientific and commercial avenues of enquiry," said DLR Chairman Prof. Dr Johann-Dietrich Wörner at the launch event held in the German Space Operations Center (GSOC) at the DLR site in Oberpfaffenhofen. "This mission demonstrates Germany's expertise in satellite-based radar technology and is, in particular, the outcome of a consistent focus in the national space programme. Also, TanDEM-X demonstrates a successful public-private partnership," stressed Prof. Wörner.

Public-private partnership

TanDEM-X is being run as a public-private partnership (PPP) between the DLR Astrium GmbH, with DLR funding coming from the German Ministry of Economics and Technology. Infoterra GmbH, a subsidiary of Astrium, is responsible for the commercial marketing of the TanDEM-X data. Astrium GmbH in Friedrichshafen built the satellite and is sharing the costs for its development and operation. The TanDEM-X mission has a total cost of 165 million Euros. DLR is contributing 125 million Euros and the European space company Astrium is contributing 40 million Euros.

TanDEM-X and its twin satellite, TerraSAR-X, will fly in formation

Together with its twin satellite TerraSAR-X, in space since 2007, TanDEM-X will survey the entire land surface area of the Earth - a total of 150 million square kilometres - several times over. It will accomplish this from an altitude of 514 kilometres within three years. "This will be the first time we will ever have had a globally standardised 3D digital elevation model of Earth, and with a measuring point density of 12 metres, it will be incredibly accurate," said Prof. Dr Alberto Moreira, Science Director of the TanDEM-X mission and Director of the DLR Microwaves and Radar Institute.

Today, for large areas of Earth, there are only approximate, non-standardised or incomplete elevation models, and it is these gaps that the TanDEM-X mission is designed to fill. To accomplish this, TanDEM-X and TerraSAR-X will fly just a few hundred metres apart and will constitute the first configurable synthetic aperture radar (SAR) interferometer in space.

With a conventional SAR, the radar on the satellite transmits microwave pulses that are reflected by the surface of the Earth and received back by the radar. The distance between the satellite and the Earth's surface is calculated from the time it takes the signals to return. Since the satellite is moving around the Earth, the radar 'illuminates' a strip along the ground, which gives the radar its synthetic aperture, much larger than its real one.

With SAR interferometry, a geographical area is imaged from two different viewing positions, giving different perspectives. This is similar to the way humans use their two eyes to get an accurate, 3D image. The two 'radar eyes' are on the satellite duo TanDEM-X and TerraSAR-X, and produce an interferogram from the different distances the signals have to cover; elevation data is derived from this

Within three years, this will create a gigantic data record equivalent to the storage capacity of 200 000 DVDs. TanDEM-X is designed for a service life of at least five years and is scheduled to overlap the scheduled service life of TerraSAR-X for at least three of those years.

Satellite-based Earth measurement creates a globally homogeneous terrain model without interruptions at national borders or other inconsistencies (compared with aircraft-based measurements). Radar can see through bad weather and operates regardless of lighting conditions. Today, this process is without competitors and enjoys considerable respect, especially in the USA.

Tremendous variety of applications

Digital elevation models can be used in a huge range of applications. Geoscientific disciplines such as hydrology, geology and oceanography require precise and up-to-date information on the properties of the Earth's surface. Digital elevation models can help to make the exploitation of natural resources more efficient and can also help to optimise relief planning in the wake of natural disasters, as well as security deployments. Digital maps are also essential to reliable navigation: their precision needs to keep pace with the increasingly stringent requirements that govern global positioning.

Germany will be the first country in the world to have a digital elevation model of Earth, making it a globally unique data product. This can be used in initiatives and programmes such as the ZKI (Center for Satellite-Assisted Crisis Information at DLR), GMES (Global Monitoring for Environment and Security) and GEOSS (Global Earth Observation System of Systems), and may also be incorporated in security-related cooperation treaties and agreements.

Commercial customers around the world are looking forward eagerly to this TanDEM-X/ TerraSAR-X elevation model. As soon as it becomes available in 2013, remote observation and geoinformation experts from the private business sector, public sector authorities, defence and security facilities will benefit.

Data processing at the DLR in Oberpfaffenhofen – enhancement by Infoterra

A network of three TanDEM-X grounds stations (Kiruna in Sweden, Inuvik in Canada and O'Higgins in the Antarctic) is ready and waiting for the immense volume of raw data that the satellites will generate. This data will be processed in three main steps: initially, the data transmitted by TanDEM-X to these ground stations will be examined. Then the results will be evaluated at the DLR’s German Remote Exploration Data Center (DFD) in Oberpfaffenhofen and processed into raw versions of elevation models. The global digital elevation model is then generated by a unit known as the mosaicking and calibration processor. The data records for the global elevation model will amount to 15 terabytes and will be available about four years after the launch of TanDEM-X.

Adaptation of the elevation model to the needs of commercial users and its worldwide marketing will be handled exclusively by Infoterra GmbH. As part of the data enhancement process, Infoterra will further process the raw data supplied by the satellite system to meet the requirements of its various customers. It is standard practice to edit out anomalies known as 'spikes' (abnormal peak readings caused by interference), offsets (which radar shadows can produce, especially in mountainous terrain) and areas of surface water (assurance of standard water levels and the correct angle of downhill gradient for rivers).

http://www.dlr.de/en/desktopdefault.aspx/tabid-1/117_read-25113/

[Nicolas PILLET]

A fantastic video from Roskosmos !!!

http://www.youtube.com/watch?eurl=http%3A%2F%2Fwww.youtube.com%2Fuser%2Ftvroscosmos&v=1NZh2as9sOs&feature=player_profilepage

[Space Pete]

BBC News: "German TanDEM-X satellite returns first images".
http://news.bbc.co.uk/1/hi/science_and_environment/10422511.stm

[Nicolas PILLET]

This picture was taken shortly before launch. Do you know what they do with this cone-shaped object ?

[tonthomas]

This picture was taken shortly before launch. Do you know what they do with this cone-shaped object ?

Closing the used launch canister before removing it from the silo?

[Space Pete]

TanDEM-X delivers first 3D images
22 July 2010

On 22 July 2010, researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) facility in Oberpfaffenhofen published the first 3D images from the TanDEM-X satellite mission. Just one month after the launch of TanDEM-X (TerrraSAR-X add-on for Digital Elevation Measurement), which took place on 21 June 2010, DLR researchers have created the first digital elevation model – almost a week ahead of schedule. A group of Russian islands in the Arctic Ocean was selected for the first test.

Precise to a few centimetres

This first elevation model shows amazing views of the icy Russian October Revolution Island, the largest island of the Severnaya Zemlya group. Details such as the height of the glaciers and individual moving ice sheets have never before been measured from space with a precision of a few centimetres. In addition, the height of a vast ice cap in the centre of the island is mapped accurately. Until now, there has been no data of this quality about this strange world. The Shuttle Radar Topography Mission, the international mission by NASA, DLR and other space agencies that flew in 2000, could not observe these polar regions – they are very important for climate research.

3D images by 'squinting'

In order for 3D images and elevation models to be obtained, TanDEM-X must fly in close formation with its twin satellite, TerraSAR-X, which has been in orbit since 2007. This way, the two satellites can image the same regions of Earth’s surface from different viewing angles. Close formation flying is yet to be achieved. Nevertheless, DLR researchers were able to generate the first 3D images by waiting for the optimum time when the two satellites – in their near-polar orbits – were very close together.

The ground tracks – the orbits of the two satellites projected onto the Earth’s surface – cross at the North Pole. When both satellites fly over this imaginary intersection at slightly different times, they come close to one another. On 16 July 2010, the researchers used this special arrangement and generated the first elevation model with the satellites 370 kilometres apart. Because this distance is still comparatively large, the radar experts had to reach deep into their bag of tricks and make the fullest use of the flexibility of the satellites. In order to simultaneously image the same area with both satellites, the antennas were not oriented perpendicular to the ground, but were tilted to one side. The two antennas ‘squinted’ to view the same point on Earth. The data obtained using this special antenna pointing was then transmitted to the ground.

"We are relieved that these first acquisitions have worked so well. This means that already at this first stage, the interaction between the two satellites is functioning correctly, the orbits are controlled accurately and our ground systems are also working well," said Gerhard Krieger, the TanDEM-X System Engineer — he had the idea for this particular experiment.

Starting point for further elevation models

The first successful experiment is the starting point for more 3D images. Close approach of the satellites also allowed acquisition of test images at lower latitudes. Shortly after the first acquisition, the opportunity arose to image a 50 x 30 kilometre area in the southern Russian region of Kalach on Don, about 100 kilometres northwest of Volgograd. This area was the target of the very first TerraSAR-X radar acquisition.

"This new elevation data give an idea of the Digital Elevation Model products that will be available from the TanDEM-X mission. For the first time, one sees the small height differences in roads, field boundaries and rivers. This opens up fantastic prospects for the application of this data – for example, for the prediction of flooding areas in the event of a disaster," said the DLR engineer responsible for processing the elevation model data, Thomas Fritz.

Slowly converging in space

In the meantime, the distance between TerraSAR-X and TanDEM-X has been reduced to 20 kilometres and this will be maintained for the next few months. Extensive system tests and calibration activities will be carried out during this time. Close formation flying will begin in the autumn of 2010. The distance between the two satellites will first be brought to 500 metres and then, for the period during which the elevation models are being recorded, it will be reduced to 200 metres.

DLR is implementing the TanDEM-X mission with funds from and on behalf of the German Federal Ministry of Economics and Technology (Bundesministeriums für Wirtschaft und Technologie; BMWi) in a public-private partnership with Astrium GmbH.


Accompanying images can be found at www.dlr.de/en/DesktopDefault.aspx/tabid-1/117_read-25845

[Space Pete]

TerraSAR-X and TanDEM-X flying in close formation.

The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and the space company Astrium have recently taken an important step forward in their mission to create a three-dimensional map of the world. On 14 October 2010, the radar satellite TanDEM-X moved into close formation with its 'twin', TerraSAR-X. Before this, the two satellites were orbiting 20 kilometres apart - a flight time of almost three seconds. Now, there are only 350 metres separating the pair, which means their antennas are able to acquire radar images of the same area simultaneously. The objective of the mission is to create a high-precision, three-dimensional digital elevation model of Earth's land surface. The project needs the satellites to operate in parallel for a period of three years. The transition to close formation flight marks the beginning of the final preparatory stage of the TanDEM-X mission. The routine operations phase is due to start in early January next year.

"This is uncharted territory"

The TerraSAR-X and TanDEM-X orbit trajectories, patented by DLR researchers, are like the strands of a double helix - they circle around one another without crossing. The team of scientists based in DLR Oberpfaffenhofen took just three days to carry out the approach in preparation for the final formation flight. "First, we had to manoeuvre TanDEM-X to reduce its orbital period, so that the satellite could 'catch up', reducing the 20 kilometre gap between it and TerraSAR-X. After two further manoeuvres we brought the distance between the pair down to 350 metres," explains DLR flight dynamics expert Ralph Kahle.

The reduced distance between the satellites means that the two radar systems can be synchronised for the first time. TerraSAR-X and TanDEM-X can also monitor each other's 'health' via an inter-satellite link. "This is completely uncharted territory. Never before have two satellites worked in such close formation over a period of several years," says Manfred Zink, Project Manager for the TanDEM-X Ground Segment. Eckard Settelmeyer, Director of Earth Observation and Science at Astrium, adds: "This dual mission will give another boost to satellite-supported applications and science."

Radar satellites working in synchronisation

The close formation flight marks the bistatic phase of the TanDEM-X mission. The two radar satellites no longer work independently, but in synchronisation. One satellite transmits the radar signals needed for image acquisition, but then both satellites receive the signals reflected from the ground. "Only in this bistatic mode can we get the image quality we need for the global elevation model. It marks an important milestone in the mission," says Zink. Working in close formation, TerraSAR-X and TanDEM-X's antennas complement one another like a pair of eyes. The combination of both radar images will no longer suffer from temporal changes between subsequent acquisitions over water or forest areas, and the combined sets of data can be processed into high-quality elevation models.

There are also energy-related benefits to this recording method. Because of the power consumption and build-up of heat, a radar satellite has a limit to the length of time for which it can transmit. However, in bistatic mode, TerraSAR-X and TanDEM-X share the transmission task. This means that the DLR scientists can use double the acquisition time that is available with one satellite.

Final preparations for the global elevation model

The comprehensive testing program for the TanDEM-X mission is expected to run until the end of 2010; then, the acquisition of data for the global elevation model can begin. In the current phase, DLR researchers will ensure that the close formation flight is optimised, the bistatic recordings are being captured correctly and the image processors are working as specified. With the successful transition to close formation flight, DLR is close to the operational phase of the TanDEM-X satellite mission.

About the mission

TanDEM-X is being implemented as a public-private partnership between the German Aerospace Center (DLR) and Astrium GmbH, with funding from the German Federal Ministry of Economics and Technology (Bundesministerium für Wirtschaft und Technologie; BMWi). DLR is responsible for the scientific use of TanDEM-X data, planning and managing the mission, controlling the two satellites and generating the digital elevation model. Astrium built the satellites and is sharing the costs of development and operation. As with TerraSAR-X, Infoterra, a subsidiary of Astrium, is responsible for the commercial marketing of TanDEM-X data.


www.dlr.de/en/desktopdefault.aspx/tabid-1/117_read-27086

[Space Pete]

The satellites have 'eye contact'.

This is the moment we have been anticipating for a long time; TerraSAR-X and TanDEM-X finally have 'eye contact'. The final manoeuvre to adjust the close formation was performed on 13 October. Now, the two satellites are orbiting at a distance of less than 400 metres from one another.

Over the last three months, the space operations centre has successfully demonstrated safe and precise formation flying of TerraSAR-X and TanDEM X with a distance of 20 kilometres between them. Now, we have approval for close formation flight and, for the first time, simultaneous radar observations are possible – without which the joint mission objective, a 3D elevation model of Earth's land surface, cannot be achieved.

The change in the formation change, which was implemented within a period of three days, is shown in the diagram above: both satellites are flying away from the observer – into the image plane – and Earth's surface is 514 kilometres below them. Once per orbit around Earth, which takes about 95 minutes, TanDEM-X (TDX) moves in a counter-clockwise elliptical path relative to TerraSAR-X (TSX). The green ellipse shows the initial formation, which was used during the period of 22 July to 10 October. The third dimension – the separation of the satellites in the direction of flight – is not shown; this was 20 kilometres. As a result of the orbital manoeuvres performed by TanDEM X, the relative path changed first to the red ellipse, then to the black, the to the magenta, and finally to the blue curve. The horizontal separation was gradually reduced from 1305 to 362 metres and the vertical separation increased from 300 to 400 metres.

During the first manoeuvre (green-red transition), the orbit altitude was changed so that the orbital period of TanDEM-X was shortened by 87 milliseconds. TanDEM-X was therefore moving slightly faster than TerraSAR-X and eliminated the 20-kilometre lead held by TerraSAR-X within two days. The approach was made at a 'snail's pace', with a relative speed of about 0.4 kilometres per hour; by comparison, a pedestrian moves at about five kilometres per hour. The path show by the blue ellipse will now be maintained for the duration of the bistatic instrument calibration phase.

Special attention was paid during the approach to the Inter-Satellite Link (ISL), a data transfer connection between TerraSAR-X and TanDEM-X. At the beginning of the approach phase, the ISL was activated in order to experimentally determine at what distance the first data could be transmitted – an interesting task for the team in the control room. On 13 October at 03:00 hrs, the first connection was achieved; while TanDEM-X was in contact with the DLR ground station at Inuvik, data sent from TSX to TDX could be viewed for the first time. At that time, the satellites were five kilometres were apart. With decreasing distance, the data transmission has become more stable and the link's full functionality was demonstrated.

This laid the foundation for a further innovation – the TanDEM X Autonomous Formation Flying (TAFF) system could finally be activated. The TAFF flight software, which was developed at DLR / German Space Operations Center, continuously obtains orbit information from TerraSAR-X over ISLs, which it filters, together with orbital parameters from TanDEM-X and thus determines the relative orbital position – in the simplest case, a distance measurement. Deviations from the target formation are determined and communicated via telemetry to the operations team. In a long test phase, TAFF must now be proven. If it functions reliably and accurately, in future TAFF will carry out the daily manoeuvres that are performed using the cold gas thrusters for precise alignment of the satellite formation.


www.dlr.de/blogs/en/desktopdefault.aspx/tabid-5919/9754_read-268

[Space Pete]

TanDEM-X and TerraSAR-X – imaging Etna while flying in formation.

First synchronised elevation model for radar satellite pair.

The TanDEM-X and TerraSAR-X satellite pair have acquired their first image of Earth’s surface, synchronised to the microsecond, while flying over Mount Etna in Italy. Scientists at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) have used the data to create a three-dimensional digital elevation model with an unprecedented elevation accuracy down to two metres. The image, taken while the satellites were flying just 350 metres apart, is the first in the world to be made by satellites flying in such a close formation.

The image shows Mount Etna on the east coast of Sicily. On the left of the image, in the foothills of the volcano, the city of Catania is visible as a collection of white points. This three-dimensional view of the volcano was generated from data recorded by TanDEM-X and TerraSAR-X. This was acquired using bistatic radar, where one of the satellites transmits a radar signal to Earth and the two satellites receive the reflection of this signal simultaneously. In this way, a highly accurate three-dimensional terrain model is created on a 12-metre grid. A similar recording technique was used in the Shuttle Radar Topography Mission (SRTM) in February 2000. However, in this case only 60 percent of Earth's surface was imaged, and at a coarser grid spacing of 30 to 90 metres.

Satellite pair captures detail from space.

Comparison of the TanDEM-X elevation model with data acquired ten years previously by SRTM demonstrates the improvement in precision; the difference between the elevations measured today and the SRTM elevation data is represented in colour on a TanDEM-X radar image of the area surrounding Mount Etna. In the area of the actual crater especially and along the flanks of the volcano there are differences of up to 30 metres.

This is partly down to the greater accuracy of the elevations measured by TanDEM-X and TerraSAR-X; as they flew over at an altitude of over 500 kilometres, the two radar satellites were able to detect detail on Etna that SRTM could not resolve. The other reason is that the volcano and its environs have changed over the course of the years; for example, to the south (left in the image) a lava flow from 2001 can be seen. The modern images use a finer measurement grid and enable geodynamic processes to be monitored. To create the three-dimensional elevation model of the entire land surface of Earth, the two satellites will fly over and image every area multiple times.

New images of the Eyjafjallajökull volcano.

Changes to Icelandic volcano Eyjafjallajökull are also visible in the two satellites' new elevation model. As they flew overhead, TanDEM-X and TerraSAR-X got sight of the volcano – whose ash cloud caused flight bans across Europe in spring 2010 – and took precise measurements of the rugged landscape of rock and ice. The colours indicate the height of the terrain; the peaks of the volcanoes are shown in white, while the lowlands where the melt water flows in spring are shown in green. The volcano’s crater, which was exposed from beneath the ice by its activity, is easily recognisable. To the right, another volcano, Katla, is ‘slumbering’ beneath a massive ice cap. The indentations visible in the ice indicate that this volcano is also active and that its ice cap is melting and collapsing as a result. Areas such as Iceland are being mapped in elevation for the first time by the radar satellites flying in formation, as the elevation model created by SRTM only reached 60 degrees latitude.

Patented discoveries.

In creating three-dimensional digital elevation models with this level of accuracy, the German Aerospace Centre and Astrium GmbH have broken new ground: among other things they have patented processes used by the satellites to exchange data for the synchronisation of their radar pulse. These ensure that TanDEM-X and TerraSAR-X are precisely synchronised to the microsecond as they record the same areas.

Until now, DLR researchers had been letting the two satellites look at the Earth asynchronously, while they were still flying 20 kilometres from each other. In this way they created around 2000 elevation models of different regions. The elevation models being produced now, however, have been processed using data captured synchronously by the satellites. To automatically calculate the 3D elevation models, DLR has developed algorithms specifically for the mission. “Processing the bistatic pairs of data is a big challenge. Everything must match up exactly in order to reach this level of precision. All sorts of data can affect the algorithms, from synchronisation signals to millimetre-accurate orbital calculations,” says DLR processing engineer Thomas Fritz. "All the systems involved, from calculating and planning the imaging to processing the elevation data have worked perfectly," confirms Birgit Schättler, who is responsible for commissioning the ground segment.

Future applications.

The adjustable flight formation and bistatic technique used by the two radar satellites make it possible for the data acquired to be analysed for a wide range of research on Earth. For example, bodies of water can be imaged without a problem for the first time. This involves the satellites synchronously generating an image of the area. In an initial successful test, DLR researchers observed the islands of Franz Josef Land in the Arctic Ocean. As if frozen in time, even the wave pattern of the sea can be recognised in the elevation model of the island group. Oceanography or climate researchers can also use such images to precisely analyse ocean currents, for example. In this image the highest areas are coloured white – the colour scheme thus roughly corresponds to the formation of ice on the islands.

Milestone on the way to a 3D elevation model of the Earth.

The first images taken in close flying formation form the foundation of the mission objective; from 2011 the two satellites will spend three years systematically measuring the entire surface of Earth multiple times with great precision. The radar satellites can observe the 150 million square kilometres of Earth’s surface around the clock, without interruption from the weather and clouds. The data acquired can be used for mapping the landscape, city planning and navigation, as well as for mission planning in disaster areas. It can also be used for scientific research in glacial, earthquake or volcanic regions.

Public-private partnership.

The DLR is responsible for the scientific use of the TanDEM-X data, planning and executing the mission, controlling the two satellites and generating the digital elevation model. Astrium built the satellites and contributed to the cost of their development and deployment. As with TerraSAR-X, Infoterra GmbH, a subsidiary of Astrium, is responsible for the commercial marketing of the TanDEM-X data.

The TanDEM-X mission is being operated by the German Aerospace centre (DLR) with funding from the German Federal Ministry for Economics and Technology (Bundesministerium für Wirtschaft und Technologie; BMWi), in the form of a public-private partnership with Astrium GmbH.


Photos: www.dlr.de/en/desktopdefault.aspx/tabid-1/117_read-27181

[wsl2005]

http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10293/427_read-19509/year-all/#/gallery/24514

New 3D world map – TanDEM-X global elevation model completed