Space

ASIM is Key to Understanding Lightning and Energy in the Atmosphere

Just shy of a cubic meter, ASIM or the “Atmosphere-Space Interactions Monitor” does not take up a lot of space. However, the project led by Terma and the Technical University of Denmark (DTU) became the biggest space project in Denmark to date.

Written by: Dan D. V. Bhanderi
Space

Just shy of a cubic meter, ASIM or the “Atmosphere-Space Interactions Monitor” does not take up a lot of space. However, the project led by Terma and the Technical University of Denmark (DTU) became the biggest space project in Denmark to date.

In short, ASIM is an observatory or an off-earth piece of equipment used to measure upper atmospheric discharges and, among other things, red sprites.

We’ve had a talk with one of the significant figures involved in the ASIM project, Torsten Neubert, Senior Scientific Advisor at DTU Space.

This article focuses on some of the beginning of the ASIM project and one of the interesting discoveries ASIM has helped shed new light on in the past four years. Why, after all, is it that this small gadget is so important?

It All Began at Stanford University During a Thunderstorm

If you strategically position yourself on a mountain top during a thunderstorm, just high enough to look above the clouds, then you will experience a phenomenon known as a red sprite.

A red flashing light with a large-scale electronic discharge at an altitude of 50 to 80 kilometers.

Just as described, Torsten Neubert experienced a red sprite for the first time. It was during his time at Stanford University back in the late 1980s, and, even though sporadic visual reports of red sprites date back to the 1880s, he was among the first people to experience this phenomenon through a black-and-white camera lens.

It was a student that was testing a camera that was going to be used for observations in America. He tested the camera by looking over the prairie above thunderstorms. Then, he saw these flashes in images and he first thought, ‘Oh, something is wrong with the camera’." Torsten Neubert recalls.

This visual of this brief, but huge glimpse of light was the beginning of a journey of knowledge with the goal of understanding the phenomena (later known as red sprites.)

Once Torsten Neubert returned to Denmark, he could not help but wonder why the Danish Meteorological Institute wasn’t part of space projects focusing on meteorology research.

Back then space science was a bit far-fetched for the Danish Meteorological Institute, which at that time was independent from DTU. Nonetheless, as the thunderstorm project focused on a weather phenomenon, he believed the project would be of relevance for the institute.

A thought he could not dismiss. And with Terma on board as responsible for engineering and production, 20 years later, the dream became a reality.

Understanding The Onset of a Blue Jet Through High Time Resolution Sensors

On April 2, 2018, ASIM was launched on the CRS-14 Falcon-9/Dragon by SpaceX. And just 11 days later ASIM was installed on the ISS by a robotic arm.

At that point Terma had been involved with the project for 11 years.

But why is it interesting?

Everybody knows that thunderstorms generate lightning, and that lightning is a quick and dangerously high energy release, naturally drawing your eyes to the lightning of a thunderstorm. However, just above the lightning other phenomena are happening.

The three photometers on ASIM are measuring light in three different wave bands. Two of the photometers have very narrow bands that can pick up atomic and molecular lines that are emitted in the blue jets happening above thunderstorms, Torsten Neubert explains.

Blue jets are traveling 50 kilometers upwards (away from earth) in the opposite direction of the lightning. Blue jets might even go as far as the ionosphere (at an altitude of 85 kilometers).

These sensors have shed new light on how we understand the onset of the phenomena called blue jets. It is a significant finding that has been featured on the front page of Nature magazine.

By sampling data using the photometers taking images 100 thousand times a second, ASIM showed how, within one sample of blue jets, the amplitude of the signal goes through the roof and then it drops down. During the following 100 milliseconds the blue light will increase to its maximum.

“We knew about blue jets, but when it starts out, it starts out with a blue flash – 10 microseconds, enormous blue flash, and then the jet rises. That was a completely new finding,” Torsten Neubert explains.

Understanding basic physics is only as good as the models we use to gain that understanding. By using resources to understand lightning, we are one step closer to understanding the physics of the world.

As of today, lightning is still commonly known as a very long spark. But how do the electrons drift, and how does the behavior behind it work?

Thorsten Neubert, DTU Space and ASIM are determined to shed light on the physics behind lightning. Understanding the onset of blue jets is not just interesting in itself. They are bringing humanity one step closer to understanding how thunder and lightning develop inside a cloud.

This has only been one of many interesting findings ASIM has gathered more knowledge on.

ASIM has been featured on another Nature cover about the findings: Frequency Oscillations in The Main Peak of Magnetar Giant Flare, as well as a feature in Science magazine about the findings on the terrestrial gamma-ray flash and ionospheric ultraviolet emissions powered by lightning.

Learn more in our Podcast

If you want to learn more about ASIM and its scientific findings, listen to our podcast episode: A View from Above: Building ASIM – a High-Tech Observatory in Space.

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