30 years with ALOMAR

If you’ve visited Andøya during winter and clear skies, you might have noticed the easily recognizable green light beams, or maybe you have seen the characteristic octagonal building at the top of the mountain. This is the ALOMAR Observatory, located on the mountain Ramnan on Andøya, 379 metres above sea level. This year marks the observatory’s 30th anniversary.

ALOMAR is an abbreviation for Arctic Lidar Observatory for Middle Atmosphere Research. The observatory is operated by Andøya Space and was created as an international collaboration between Norway and Germany. Today researchers from Norway, Germany, Spain and the United States monitor and map processes in the atmosphere from ground level up to 100 km.

the characteristic octagonal building ALOMAR, located at the mountain top. Surrounded by lots of snow and the ocean in the background.
The characteristic octagonal building, ALOMAR.

On June 16th 2024, it is 30 years since the observatory was formally opened by at that time, the German Minister of Research, Paul Krüger, and the Norwegian State Secretary in the Ministry of Environment, Børre Pettersen. Since then, the data from ALOMAR have contributed in well over 500 scientific publications, and made important contributions to climate research. So how did a high-tech research observatory actually come about at the top of Ramnan, 379 meters above sea level?

The story of ALOMAR begins

The story of ALOMAR begins a few years before it was built at Ramnan. As early as 1984, the first atmospheric lidar was installed at Andøya Space, in a building close to Oksebåsen where the headquarter is located today. The measurements were mainly made as a supplement to rocket campaigns, to verify desired research conditions and weather observations in order to safely launch rockets.

An older picture of a military green building with green grass in the surroundings and mountain behind.
The old lidar building, located in Oksebåsen.

In the years that followed, a number of interesting experiments were carried out, and the experiments showed that the lidar had great scientific potential for measurements in the atmosphere. When it was decided that the lidar observatory would be further developed, the choice of location was very important. It became natural to choose a location close to Andøya Space, in order to have access to the technical expertise and to be able to contribute to the research that was already taking place in the north. At the same time, sea spray and sand were a problem at the current location, so the new location had to be further away from the shoreline.

On the mountain Ramnan, just above Oksebåsen, the Norwegian Armed Forces and the, at that time, Norwegian Telecommunications already had a station with a road connection and power supply. The location was considered well suited for a future research observatory, and the foundation stone for the building was laid by, at that time, the Norwegian Minister of Foreign Affairs Johan Jørgen Holst in the summer of 1993. On June 16th, 1994, the building was formally opened.

An older man putting a foundation stone into the ground, with concrete around the hole.
The foundation stone was laid.

A slightly different construction process

ALOMAR currently measures both temperature and winds, as well as the concentration of aerosols and ozone in our atmosphere. This is to be able to monitor and map processes in the middle layers of the atmosphere.

ALOMAR was mainly built to house lidar systems, and when building a research observatory where lidar measurements are the main activity, the construction process is slightly different than when building a normal building. When ALOMAR was built, they started in the middle and worked their way outwards. The heart of ALOMAR is the telescope hall, where laser beams are emitted into the atmosphere using mirrors. The light that comes back is captured by the telescopes, and has often hit water droplets, ice crystals, aerosols and air particles on its way.

The telescope hall is the heart of the building, both because it is physically located in the center of the building, but also because it is the main room for the lidar measurements.

Two large telescopes seen from above, pointing up towards the sky.
The telescope hall seen from above.

Lidar measurements

A lidar is an optical remote sensing technique that is based on the backscattering of light. Lidar uses light in the same way that radar uses radio waves, and the term lidar is also used for the measuring instrument itself.

When lidar measurements are made from ALOMAR, a 7×7 meter skylight opens at the rooftop to be able to release the two laser beams from the RMR lidar. RMR stands for Rayliegh-Mie-Raman, and was built by German, British and French scientists. The outer walls around the room are insulated so that heat from offices and laboratories will not seep into the hall, and the cold from outside will not cool down the rest of the building when it is open.

The lasers, computers and optical components are located in the laboratories around the telescope hall to avoid temperate fluctuations and high humidity. Laser light is sent through openings in the wall into the telescope hall, and the light that comes back from the atmosphere is sent into fiber cables that go on to the detector rooms where they process the data.

The RMR lidar can be used to routinely observe winds and temperatures from 30 to 80 kilometers when the sky is clear. This can be used to measure noctilucent clouds (NLCs), polar stratospheric clouds (PSCs), and to update, correct or confirm standard atmospheres. One can also study wave activity and the dynamic state of the atmosphere. Such studies are very important for understanding the radiation and energy balance in the atmosphere and thus the development of Earth’s climate.

A sky filled with northern lights, mountains on the ground and to laser beams up in the sky.
The lidar beams from Alomar.

Instruments at ALOMAR

Today, ALOMAR houses lidar, radars, sun photometer, brewer, GUV, riometer, radiosonde station, ceilometer and camera systems. All the instruments provide their datasets that can give important information about the atmosphere. In addition, you can combine the data from several instruments, and get even better and more comprehensive information. For example, by combining the information from the sun photometer and lidar. The sun photometer can measure the intensity of solar rays at different wavelengths, while the lidar can provide information about the height and thickness of aerosol particles. By using the information from both instruments, it is possible to say something about the distribution of particles at altitude, which can provide information about the air above Andøya.

ALOMAR is also involved in several research projects where the instruments are used, among other things, to calibrate and validate satellites that pass over Andøya, to compare measurements made by the satellites and by the instruments on the ground.

Important piece of the puzzle

Over the past 30 years, large amounts of data have been collected from ALOMAR. Climate research is more and more important, and the data from ALOMAR can be an important piece of the puzzle about the atmosphere in Arctic regions.

The celebration of the 30th anniversary is done with many future plans of measurement and projects with data from ALOMAR.

More information

For more information, contact Andøya Space Sub-Orbital