EISCAT_3D Frequently Asked Questions
- What is EISCAT_3D?
- Why “_3D”?
- What is a phased array?
- How large is each phased array?
- What kind of transmitter is used?
- Why so much power?
- Where does the power come from?
- Is it dangerous?
- Can I look at the data?
- Who pays for this research facility?
- Where will EISCAT_3D be located?
- Why these locations?
- What happens to the results?
- Can EISCAT_3D see other things, like airplanes and satellites?
- Does EISCAT_3D measure Space Weather?
- Where can I learn more about EISCAT and EISCAT_3D?
What is EISCAT_3D?
EISCAT_3D will be a radar system for the scientific study of the Earth’s atmosphere and ionosphere. It will use a technique called Incoherent Scatter Radar (ISR) to measure basic physical parameters of the ionospheric plasma and upper atmosphere near the Earth. This kind of system supports the study of phenomena such as the aurora borealis (northern lights) and noctilucent clouds.
Why “_3D”?
Using separate stations in Norway, Sweden, and Finland, based on phased array technology, EISCAT_3D will be able to make three-dimensional measurements of the plasma densities and temperatures and the direction of motion of that plasma, among other things. This will provide scientists a more comprehensive view of the important physical processes. These measurements are also frequently combined with other techniques (such as optical images, riometry, and modelling) to provide a deeper view of the plasma.
What is a phased array?
A phased array antenna is a set of simple antennas which, when combined, act as a much larger antenna. The EISCAT_3D phased array antennas will each consist of approximately 10,000 simple antennas. The signals from the antennas will be combined electronically, which allows the radar to be steered very rapidly over much of the sky. In fact, it will easily look in more than 1000 different directions each second, and 100 different directions at any given instant, if the scientists so wish.
How large is each phased array?
The 10,000 antennas at each site will cover an almost circular area of roughly 70 meters in diameter. The core transmit site (near Skibotn, Norway) will also host 10 smaller antenna arrays for more precise measurements. The larger arrays will be enclosed in 100 m × 100 m fenced areas to protect the system from unwanted visitors (such as moose). The sites will also have small buildings to house some of the sensitive electronics.
What kind of transmitter is used?
EISCAT_3D will use a distributed solid-state transmitter, with 1000 W peak power (up to 250 W average power) on each active antenna. The goal of the first stage of the construction of the EISCAT_3D system is to have amplifiers on approximately 5000 of the antennas, yielding a peak power of 5 MW or an average power of up to 1.25 MW.
Why so much power?
The ISR technique bounces radio waves off of free electrons in the ionosphere. These electrons are extremely small and, as a result, high transmitter powers, large antennas, and sensitive receiver electronics are necessary to see any signal at all! Most of the transmitted signal passes right through the atmosphere and ionosphere and out into space, but the tiny bit that comes back tells us very much about the plasma!
Where does the power come from?
EISCAT_3D will be powered by electricity from the normal electric grid. A hydro-electric plant is located only a few kilometers from the planned core site in the Skibotn valley. UPS battery back-ups will protect the computers on the sites in case of power failures.
Is it dangerous?
No, the EISCAT_3D system is designed to protect both people and wildlife from exposure to high strength radio waves. There will be a metal fence around each array to protect the electronics and antennas from wildlife. Within the fenced area radio waves can be greater than international and local standards allow (which is why it is interlocked to turn off when maintenance personnel are inside the fence), but outside the fence the levels will be well below the allowed intensities. In fact, the system will use the fence itself to ensure that this is the case. Additionally, the system will be regularly tested by the relevant government agencies and by EISCAT to ensure that there is never a risk to people (or moose) that may stray close to the radar system.
Can I look at the data?
Plots of the measurements will be available for viewing on-line for the majority of experiments. For scientists to run their own experiments they must either be part of the EISCAT Scientific Association (through membership agreements between research councils and institutions) or by competing through a peer-review program. EISCAT only allows open scientific research programs to be run and operates solely in the civilian sector (no defence-related work is allowed).
Who pays for this research facility?
The EISCAT Scientific Association presently consists of six associate nations (China, Finland, Japan, Norway, Sweden, and the U.K.) and affiliated institutes (currently from Germany, South Korea, Ukraine and USA). These associates and affiliates jointly fund the operation of the radars. The hardware and development were funded via contributions from the EISCAT Associates and the European Union.
Where will EISCAT_3D be located?
The first stage of the construction of EISCAT_3D involves sites near Skibotn (Norway), Kaiseniemi (Sweden), and Karesuvanto (Finland). Future stages include more sites.
Why these locations?
The location of the three radar sites form an almost equilateral triangle, which is a good geometry for the radar system to obtain data about the ionosphere. The transmitter site is also located in an area with relatively little cloud cover, which is helpful when combining the EISCAT_3D radar measurements with optical measurements of, for instance, the aurora borealis.
What happens to the results?
The analysis and results obtained from the measurements are typically published in a variety of peer-reviewed scientific journals. The very large ‘raw’ data files remain the property of EISCAT, but the scientific results are provided to everyone with internet access.
Can EISCAT_3D see other things, like airplanes and satellites?
Yes, to some extent. However, the EISCAT_3D transmit array will be placed in a valley to limit the number of aircraft in its field of view. This is done because reflections from these objects are too strong and will hide the scientific data the system is interested in receiving. Satellites are a particular problem because they travel through the region of space that the radar is primarily interested in, so the reflections from satellites must be carefully removed. The system will also be able to see micro-meteors, which come from sand grain sized particles that fall into the top of the atmosphere all the time. This is another area of study by the EISCAT scientists.
Does EISCAT_3D measure Space Weather?
The term space weather refers to studies of how activity on the Sun and in the solar wind affects the space environment near the Earth. EISCAT_3D scientists will work on the research to understand how space weather comes about by making precise measurements of how the solar wind influences an important part of the near-Earth space environment (the auroral zone). It will be less useful for operational predictions of space weather events because those predictions require measurements closer to the sun.
Where can I learn more about EISCAT and EISCAT_3D?
The website of EISCAT Scientific Association (www.eiscat.se) contains information about the association and the radar systems.