Eyes on the Aurora Part 1: What is an All-Sky Camera?

Guest post by Aurorasaurus Ambassador Jeremy Kuzub

This article is the first of three about how researchers and citizen scientists record and explore years of auroral activity using all-sky cameras, keograms, and software visualizations.

What if you could stand under the aurora-filled night sky and watch everything from horizon to horizon, all night, every night, for years on end. You would probably get a very good feel for aurora behaviour. You’d learn to understand the movements and patterns and ‘language’ of the light.

With this knowledge, you might see similar patterns in the aurora of other planets like Jupiter or Saturn and maybe even planets in other solar systems. The language of the aurora’s motion and light doesn’t stop with Earth. If you speak it, you speak part of the bigger language of space weather.

Of course, standing outside every night for years on end is not all that practical. Your eyes can’t even take in the whole sky at once – they are not sensitive enough, and most of the sky is always behind you.  This is why researchers and citizen scientists use a special type of camera called an ‘all-sky camera’.

Photo and diagram of an all-sky camera, a metal cylinder with a clear dome on top. In the clear dome are pieces labeled "Weather protection dome" and "fish-eye lens", while in the cylinder are pieces labeled "optional filter[s] and optics", "re-imaging objective lens," "CCD digital camera," and "data storage, networking".

An all-sky camera positioned under a clear dome, part of the THEMIS network of imagers. Instrument-grade all sky cameras are fully calibrated for lens, filter and imager characteristics so that the resulting images can be mapped back to aurora location and intensity. (Image credit: “The THEMIS array of ground based observatories for the study of auroral substorms”)

All-sky cameras are designed to be the best possible aurora watchers. This means they must unblinkingly capture all of the sky at once. To do this, an all sky camera is fitted with a “fish-eye” lens that has a 180-degree field of view, wide enough to see the sky from horizon to horizon when pointed straight up. The camera system can be calibrated so that any part of the sky can be matched to a location above Earth. Here is is what a single frames looks like:

A circular image on the left shows a daytime sky ringed with trees, while a circular image on the right shows a nighttime sky with aurora.

An all-sky camera’s view of the night sky, with its “fish-eye” lens pointed straight up. North is toward the top of the image, south at the bottom. East and West are reversed because the camera is looking up, like a person lying on their back looking up. The ground is the edge of the circular view, with the trees around it. The image on the left includes clouds and moon, the image on the right shows an auroral substorm overhead. (Image credit: AuroraMAX with author’s annotations)

All-sky cameras take hundreds of photos each night that can be assembled into time-lapse movies which show the aurora motion in fast-forward, making a whole night of activity seem like a few minutes of a swirling colour.

Green bands of aurora dance in animation across a circular all-sky image

An all-sky camera image sequence can be assembled into a timelapse movie of activity at about 100 times normal speed. The whole aurora event is a swirling crystal ball of colour. (Image credit: snippet from an AuroraMAX video)

 

To get the most out of these images, researchers synchronize them with other science instruments. If all the instrument data is played back at the same time, we can start to really understand the music of space weather. Let’s look at an example of data from a magnetometer (a very sensitive compass) synchronized with an all-sky camera located in Yellowknife, NWT. Can you spot the relationship between the burst of magnetic activity and the ‘substorm’ of auroral activity?

An animated all-sky image is synchronized to a four-part plot labeled "Yellowknife (YKC) magnetic variation (northward, eastward, downward, intensity)

A synchronized view of changes in Earth’s magnetic field with an all-sky camera image of the aurora near the same location in Yellowknife. The magnetometer data is from the CANMOS network station YKC, showing magnetic deflection from typical values as an aurora substorm enters the expansion phase. (Image credit: All-sky camera images from AuroraMAX. Magnetometer plot from Natural Resources Canada)


This was one of the first fundamental discoveries about the aurora–they are intimately linked with the changes in Earth’s magnetic field. The only force that can disturb Earth’s magnetic field in this way is the solar wind of charged particles from the sun. What you see is evidence that the sun and Earth are coupled by a complex interaction of space weather.

The Big Picture: All-Sky Camera Networks

When you are learning about the Earth and space weather, you have to think big. Thinking big means not just synchronizing your instruments to each other, but to many similar instruments over a very wide area. The first big project to explore the aurora across many countries was during the International Geophysical Year of 1957-1958.  International researchers cooperated to install a network of more than one hundred all-sky cameras across Scandinavia, North America, and many other locations. Each camera could see nearly 500km in any direction, and their fields of view overlapped to create a global  view of the Earth rotating under the auroral oval.  Studying this global mosaic led to the discovery that auroral activity is synchronized across thousands of kilometers (see “The Development of the Auroral Substorm” by Syun-Ichi Akasofu) . This is evidence of powerful, rhythmic energy releases in Earth’s magnetosphere. Researchers named these build-ups and releases of energy ‘Auroral Substorms’. They were a message in the language of the aurora that all-sky cameras helped us find.

Over an outlined map of North America are superimposed multiple all-sky image animations, showing the cameras' coverage across the continent under the auroral oval

The THEMIS all-sky camera network creates a mosaic view of activity across thousands of kilometers. Explore the University of Calgary Auroral Imaging Group’s THEMIS all-sky camera and data archive at https://www.ucalgary.ca/aurora/projects/themis. (Video credit: NASA/Goddard Space Flight Center Scientific Visualization Studio, https://youtu.be/yKzUb-hJmTc)

The original all-sky cameras were film based. Someone had to collect and develop the film, match up frames to those from other cameras and other instruments manually. It took a huge amount of manual work and dedication. Imagine what those researchers would think of today’s all sky camera networks like MIRACLE and THEMIS. They use far more sensitive digital imagers that can record the whole visible spectrum like a human eye, or filter wavelengths of auroral light emitted by specific kinds of particle interactions. With advanced custom software and data systems, the circular images from the cameras are automatically combined into mosaics that cover most of the auroral zone. Researchers and citizen scientists can review these nightly archives and match them up with other data from spacecraft, ground instruments and aurora chaser photos. There really is a bigger picture to assemble from all these data sources. Only when they all work together can we piece together the chain of events that powers and shapes the aurora.

Explore All sky Camera Video

As part of public science outreach, The University of Calgary’s Auroral Imaging Group maintains the AuroraMAX camera in Yellowknife, NWT, and the associated website in cooperation with Astronomy North and the Canadian Space Agency. This is an uncalibrated full-color all-sky camera that provides  real-time images approximately every 5 seconds. The site also features a deep archive of nightly time-lapse videos. For example, here is the night of March 1, 2019 which had active aurora conditions and a clear sky. 

Three images of the keogram index page on smartphones give a preview of browsing the site online

Try browsing the AuroraMAX archive using the keogram index and viewer app at apps.jufaintermedia.com/keogramindex (Image credit: Jeremy Kuzub)

Inspired by the AuroraMAX archive, I wrote a mobile-friendly web app that lets you explore their video archive. Years of aurora activity can be quickly browsed using a “keogram index”, a collection of images that capture each night’s entire auroral activity as a single image. Selecting a specific night will take you to a virtual first-person view of that night’s aurora video, where you can stand under the aurora like you were actually there. Try it at apps.jufaintermedia.com/keogramindex

This is the first of a series of three posts, which will focus on all-sky cameras, keograms, and visualizations. Keep an eye on the Aurorasaurus blog and social media for Eyes on the Aurora Part 2: “Keograms” and Part 3: “Visualization” .

Jeremy’s Bio

Jeremy Kuzub is an interactive software simulation developer and aurora photographer based in Ottawa, Canada. He has created an aurora visualization web app to explore years of AuroraMAX public outreach video of Yellowknife aurora, which can be viewed at apps.jufaintermedia.com/keogramindex

More to Explore

Space Physics in the Earliest Days, as I Experienced”, Syun‐Ichi Akasofu

Dynamic Morphology of Auroras”, Syun‐Ichi Akasofu

The Development of the Auroral Substorm”, Syun‐Ichi Akasofu

The AuroraMAX website, an amazing resource with years of all-sky camera imagery

Explore the University of Calgary Auroral Imaging Group’s THEMIS all-sky camera and data archive

All about the THEMIS project, a linked set of all-sky imagers and keograms for auroral research

Astronomy North northern sky outreach and education website with aurora forecasts

Why Auroras Erupt”, NASA Visualization Explorer

Rockets, Radar, and Computers: The International Geophysical Year”, NOAA

Thomas Jacquin has posted instructions and software for making and running your own all-sky camera:
Instructables Wireless All Sky Camera Instructions

Swedish Institute of Space Physics all-sky-camera portal

References

The THEMIS array of ground based observatories for the study of auroral substorms

The THEMIS Mission (Book)

THEMIS Canada website

MIRACLE Project site

THE ALIS Project

Hyperspectral all-sky imaging of auroras

THEMIS Mosaic Movies, Auroral Imaging Group, University of Calgary

The Kjell Henrikson Observatory site

All-Sky camera, Norwegian Centre for Space Weather

NASA – The History of Auroral Substorms

Svalbard All-Sky Imager Data

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