Space – An Integrated Tool of Polar Research
Bo Andersen, Norwegian Space Centre
The viewpoints expressed in this article are solely those of the author and cannot be attributed to the Norwegian Scientific Academy for Polar Research. The Academy hopes that our Newsletter can stimulate debates among our members and partners, which may be edited and posted on our web-site.
Space, the high mountains, the deep oceans and the Polar Regions are the most hostile environments that humanity has moved into. This hostility is caused by the remoteness, the extreme environments as well as fundamental logistic issues. Polar research attacks fundamental problems in Earth System Sciences, both concerning issues of global change that have the largest effects in polar areas and issues concerning amplification mechanisms of global change. Diminishing Arctic sea ice and potential changes in the thermohaline circulation are but two such issues. The vastness of the Polar Regions excludes the possibility of having extensive and dense distribution of in situ measurement stations.
Using space as an observing platform gives unique opportunities to observe towards the Earth as well as the rest of the Universe. For the understanding of terrestrial processes, the rest of the Universe is on the short term, mainly the Sun and the solar system. We know that the Earth has been bombarded by objects of different sizes, these have on the long term clearly influenced its surface and habitat. The output of the Sun, including both radiation and electrical charged particles are the main external drivers in climate change. The Sun drives the climate and a main question is whether the variability of the Sun is a dominant driver of climate change in our lifetimes. The only direct measurements with sufficient accuracy of solar change can only be done from space. The on going measurements of the Sun from space, clearly indicates that we currently cannot blame solar variability for the observed climate change.
Observing the Earth from space give the unique possibility to achieve global homogenous and unambiguous measurements. In the last half century an steadily increasing number of Earth Observing satellites have been launched and operated. The sophistication of these measurement systems are globally becoming very high to answer fundamental Earth System Science questions. Several of these missions are designed for observational parameters of great importance to polar research.
The majority of Earth observation missions go in polar orbiting orbits. This implies that the spatial coverage and timeliness of the observation is clearly highest in the Polar Regions. For many missions this means update of observations from every 100 minutes to a few days, depending on the type of observation. When a satellite can observe a region, the satellite can be observed from the ground. On this background, the largest ground station for polar orbiting satellites have been established by Norway (KSAT) at 78 degrees northern latitude. From this station polar orbiting satellites can be communicated with on every orbit.
Svalbard is the high latitude site where surface measurements from satellites can be accessed in near real time. The data from the observations can be transmitted to the ground stations as they are acquired. On an operational basis Norway does this with both satellite radar data (SAR) and vessel monitoring using the transmitted AIS information. Concerning research the near real-time information has not been utilized fully yet. However, the extensive spatial coverage is there for the taking, but has not yet been integrated closely into the existing data streams for the surface based observations. On the basis of this Earth Observation measurements are an integral part of the SIOS (Svalbard Integrated Earth Observing System) infrastructure project. The satellite owners can get calibration and validation of their instruments and the scientist can use this information to measure areas that are logistically and environment wise inaccessible. A clear and mutual win-win situation for the scientists using both space and surface based observations.
The large space organizations have provided many satellites of fundamental importance to polar research that are in operation now. These measure sea ice cover, thickness, and movement glacial mass balances, sea surface height, temperature and salinity as well as velocities of glacial movement.
The majority of the fleet of satellites, both now and previously, are experimental satellites for specific types of measurements. This is a problem concerning measurements of long-term changes in the polar region and elsewhere. The polar researchers only have information during the years a single satellite is operational and there is no guarantee for continuation of the measurements.
Concerning some measurements like sea ice cover and radar imaging there is a large number of satellites that can cover for each other. Luckily both NASA/NOAA and ESA/EU have understood the importance of guaranteed long term measurements and plan to a specific subset of important parameters until about 2035. The mainly weather driven measurements of NOAA and EUMETSAT also plan continuous observations in the same timeline. The EU Copernicus observation system will provide guaranteed measurements with overlapping launches on consecutive versions of the six Sentinel satellites.
It is clear that in addition to a healthy competition within the science and technological areas, there is a broad collaboration between the major space agencies concerning civilian Earth Observation. For the required comprehensive observation needs related to the Earth System, no nation has neither the funds, scientific nor the technological capabilities to do all the required missions by themselves.
The scientific “one of a kind” missions can in general be very useful for specific polar science questions, but have lesser impact on the observation of long-term changes. Experience fro the European Space Agency (ESA) have clearly shown that important measurements on the experimental satellites can migrate into new operational systems. Several instruments on the ERS and ENVISAT missions have resurfaced as payloads of the space segment of the operational Copernicus system. Similar phenomena is also seen in the US NASA/NOAA configuration.
The last decade has seen a growing global acceptance that to understand the mechanisms and consequences of global change, long-term consistent measurements are required.
It is clear that the satellite information has been the essential observational input to describe the sharp decline of the Arctic Sea Ice Cover since the observations started in 1979. There is an international set of missions that now provide continuous observations that will continue beyond the foreseeable future. The same applies to the sea surface temperature and height. ESA/EU, JAXA, Canada, as well as Germany and Italy have operational SAR systems that give detailed coverage and resolution of the polar sea ice. This is essential for the understanding of melting, drift and discharge from the polar regions.
The Norwegian Polar Institute expedition (N-ICE) use these measurements together with in-situ observations to get a full picture of the detailed information of the sea ice in the broader regional picture. This combination is an excellent example of mutual benefit for the involved parties. The figure shows the path of the frozen inn vessel Lance in an image from the Canadian Radarsat-2 mission..
The scientists on Lance are doing extensive surface measurements that will compared with the measurements the different frequency SAR instruments. Apart from giving the overall details of ice movements explaining the drift of the vessel, the scientists and satellite owners learn to understand the details of their satellite measurements to better understand the transformation of measured signals to physical parameters at the surface.
In spite of an increased understanding and funding will from major space agencies, there are several important measurements of global change in the polar regions that are not secured in the long run. The long-term gravitational measurements for mass balance measurements of glaciers and ice caps is one such area. Also the measurements of sea ice thickness constitute an area that has been measured intermittently by NASA and ESA, but there is currently no plans to ensure long term continuous measurements.
Satellite observations cannot provide all types of observations needed in polar research. There are clearly continuous needs for in situ measurements concerning the details at the surface and in the oceans, specifically within the life sciences. Apart from the ability of providing broader and more consistent polar wide measurements, are there other areas where polar research can learn from space experimentation?
Clearly, for detailed measurements a large number of in situ instrumentation is required, but much of the currently available instruments are large, heavy and require a lot of power. Many have also to be permanently manned to a great expense. The low power and mass allowances in space missions should be used for autonomous multiple measurements of the atmosphere, surface as well as subsea. This has been started with simple instrumentations in the international buoy network. However this should be expanded to more parameters. As an example, some scientists have the opinion that for autonomous instruments in sensitive and remote areas, new developments should look at this as if it was on Mars. This has to be done in order to utilize the latest capabilities concerning mass, measurement techniques and communication bandwidth needs.
For the automated systems the only communication system that are really global and can cover the user needs, are satellite systems. At latitudes below 74 degrees there is acceptable bandwidth available, north of this there is only relative narrow band systems available with the Iridium system. It is clear that sophisticated measurement systems may need much broader bandwidth than what is available now or is planned in the near future. This should be looked into by the nations that are active in the high Arctic.
Concerning space and polar research there are some important conclusions and recommendations to be made:
- Space is essential for major parts of polar research due to data coverage and timeliness.
- In many areas there should be a closer integration with in-situ measurements by making the space information adaptable to the rest of the scientific community.
- Autonomous instruments in the high arctic require better and cheaper communication services.
- New instruments should be developed as if they should be placed on Mars and not in remote areas of the Earths Polar Regions.