GeoLog

photography

Geosciences column: Making aurora photos taken by ISS astronauts useful for research

Geosciences column: Making aurora photos taken by ISS astronauts useful for research

It’s a clear night, much like any other, except that billions of kilometers away the Sun has gone into overdrive and (hours earlier) hurled a mass of charged particles, including protons, electrons and atoms towards the Earth.  As the electrons slam into the upper reaches of the atmosphere, the night sky explodes into a spectacular display of dancing lights: aurora.

Aurora remain shrouded in mystery, even to the scientists who’ve dedicate their lives to studying them. Photographs provide an invaluable source of data which can help understand the science behind them. But, for aurora images to be of scientific value researchers need to know when they were taken and, more importantly, where.

You’ve got to be in the right place at the right time to catch a glimpse of the elusive phenomenon. In the Northern Hemisphere, aurora season peaks in autumn through to winter. Geographically, the best chance of seeing them is at latitudes between 65 and 72 degrees – think the Nordic countries.

That is unless you are an astronaut on the International Space Station (ISS), in which case, you’ve got the best seat in the house!

The orbit of the ISS means it skims past the point at which aurora intensity is at its peak, which also happens to be the point at which they look their most spectacular. Its orbital speed means it can get an almost global-scale snapshot of an aurora, passing over the dancing lights in just under 5 minutes.

Not as much is known about Aurora Australis (those which occur in the southern hemisphere) as we do about the Northern Lights (visible in the northern hemisphere), because there are far less ground-based auroral imagers south of the equator. The ISS orbit means that astronauts photograph Aurora Australis almost as frequently as Aurora Borealis, helping to fill the gap.

Testament to the privileged viewpoint is the hoard of photographs ISS astronauts have amassed over time – perfect for scientists who study aurora to use in their research.

Time-lapse shot from the International Space Station, showing both the Aurora Borealis and Aurora Australis phenomena. Credit: NASA

Except that, until recently, the ISS photographs were of little scientific value because they aren’t georeferenced. The images are captured by astronauts in their spare time using commercial digital single lenses reflector cameras (DSLRs), which can’t pinpoint the location at which the photographs were taken – they were never intended to be used in research.

Now, researchers at the European Space Agency (ESA) have developed a method which overcomes the problem. By mapping the stars captured in each of the photographs and the timestamp on the image (as determined by the camera used to take the photograph), the team are now able to geolocated the images, giving them accurate orientation, scale and timestamp information.

Despite the success, it’s not a straightforward thing to do. One of the main problems is that the timestamps aren’t always accurate. Internal clocks in DSLRs have a tendency to drift. Over the period of a week they can be out by as much as a minute, making it difficult to establish the location of the ISS when the image was captured. This has implications when creating the star map, as the location of the station is used as a starting point.

To resolve the issue, aurora images which also include city lights can be aligned to geographical maps using reference city markers to get a timestamps accurate to within one second or less. In the absence of city lights, images which also capture the Earth’s horizon are aligned with its expected position instead. The correction works best if both city lights and the horizon can be used.

Errors are also introduced when the star maps can’t be fully resolved (due to the original image being noisy, for example) and because the method assumes that auroras originate from a single height, which isn’t true either.

detailed comparison between the ISS image plotted in Fig. 11 (b) and the contemporaneous image acquired by the SNKQ THEMIS ASI (a) . The original ISS image is plotted in (c) . Red and blue symbols trace the locations of the j shaped arc and northern edge of the main auroral arc, respectively, derived from their locations in the THEMIS image. The features are marked with the same coloured arrows in (c) . The magenta arrows point out a vertical feature projected very differently in (a) and (b) .

A detailed comparison between an ISS image of aurora (a) plotted and (b) the contemporaneous image acquired by the SNK THEMIS ASI [ground-based]. The original ISS image (a) is plotted in (c). For more detail see Riechert, et al., 2016.

Comparing images of an aurora on 4 February 2012, captured both by the ISS crew and a ground-based instrument, has allowed the researchers to test the accuracy of their method. Overall, the results show good agreement, but highlight that the projection of the ISS images has to be taken into account when interpreting the results.

Now, a trove of thousands of Aurora Borealis and Australis photographs can be used by researchers to decipher the secrets of one the planet Earth’s most awe-inspiring phenomenon.

By Laura Roberts Artal, EGU Communications Officer

 

References:

Riechert, M., Walsh, A. P., Gerst, A., and Taylor, M. G. G. T.: Automatic georeferencing of astronaut auroral photography, Geosci. Instrum. Method. Data Syst., 5, 289-304, doi:10.5194/gi-5-289-2016, 2016.

Automatic georeferencing of astronaut auroral photography: http://www.cosmos.esa.int/web/arrrgh

The research was accomplished using only free and open-source software. All the images processed to date are made freely available at htttp://cosmos.esa.int/arrgh, as is the software needed to produce them.

Announcing the winners of the EGU Photo Contest 2016!

Announcing the winners of the EGU Photo Contest 2016!

The selection committee received over 200 photos for this year’s EGU Photo Contest, covering fields across the geosciences. Participants at the 2016 General Assembly have been voting for their favourites throughout the week  of the conference and there are three clear winners. Congratulations to 2016’s fantastic photographers!

 Glowing_Ice. Credit:  Vytas Huth (distributed via  imaggeo.egu.eu). Ice on Jokulsarlon beach in Iceland. Ice calving off the Breidamerkurjokull, one of the glaciers comprising the Vatnajokull, the largest glacier in Iceland. The is retreating rapidly, and in the process has created a large glacial lagoon known for its spectacular icebergs.

Glowing_Ice. Credit: Katharine Cashman (distributed via imaggeo.egu.eu). Ice on Jokulsarlon beach in Iceland. Ice calving off the Breidamerkurjokull, one of the glaciers comprising the Vatnajokull, the largest glacier in Iceland. The is retreating rapidly, and in the process has created a large glacial lagoon known for its spectacular icebergs.

 'Living flows'. Credit:  Marc Girons Lopez (distributed via  imaggeo.egu.eu). River branches and lagoons in the Rapa river delta, Sarek National Park, northern Sweden. The lush vegetation creates a stark contrast with the glacial sediments transported by the river creating a range of tonalities.

Living flows’. Credit: Marc Girons Lopez (distributed via imaggeo.egu.eu). River branches and lagoons in the Rapa river delta, Sarek National Park, northern Sweden. The lush vegetation creates a stark contrast with the glacial sediments transported by the river creating a range of tonalities.

 'There is never enough time to count all the stars that you want.' . Credit:  Vytas Huth (distributed via  imaggeo.egu.eu). The centre of the Milky Way taken near Krakow am See, Germany. Some of the least light-polluted atmosphere of the northern german lowlands.

‘There is never enough time to count all the stars that you want.’ . Credit: Vytas Huth (distributed via imaggeo.egu.eu). The centre of the Milky Way taken near Krakow am See, Germany. Some of the least light-polluted atmosphere of the northern german lowlands.

In addition, this year, to celebrate the theme of the EGU 2016 General Assembly, Active Planet, the photo that best captured the theme of the conference was selected by the judges. The winner is the stunning ‘Mirror Mirror in the sea’, by Mario Hopmann! Congratulations! Scroll to the top of this post to view Mario’s image.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Last chance to enter the EGU Photo Contest 2016!

Last chance to enter the EGU Photo Contest 2016!

If you are pre-registered for the 2016 General Assembly (Vienna, 17 -22 April), you can take part in our annual photo competition! Winners receive a free registration to next year’s General Assembly! But hurry, there are only a few days left to enter!

Every year we hold a photo competition and exhibit in association with our open access image repository, Imaggeo and our annual General Assembly. There is also a moving image competition, which features a short clip of continuous geoscience footage. Pre-registered conference participants can take part by submitting up to three original photos and/or one moving image on any broad theme related to the Earth, planetary and space sciences.

How to enter

You will need to register on Imaggeo to upload your image, which will also be included in the database. When you’ve uploaded it, you’ll have the option to edit the image details – here you can enter it into the EGU Photo Contest – just check the checkbox! The deadline for submissions is 1 March.

Last chance to enter the EGU Photo Contest!

From top left to bottom right, Erosion Spider by John Clemens, Icebergs at Night in the Antarctic by Eva Nowatzki, Star Trails in Rocky Mountain National Park by Martin Snow, MicROCKScopica – Symplectite in Granulite by Bernardo Cesare (distributed via imaggeo.egu.eu).

Some finalists from the 2014 Photo Competition. From top left to bottom right: Erosion Spider by John Clemens, Icebergs at Night in the Antarctic by Eva Nowatzki, Star Trails in Rocky Mountain National Park by Martin Snow, MicROCKScopica – Symplectite in Granulite by Bernardo Cesare (distributed via imaggeo.egu.eu).

If you are pre-registered for the 2015 General Assembly (Vienna, 12 -17 April), you can take part in our annual photo competition! Winners receive a free registration to next year’s General Assembly! But hurry, there are only a few days left to enter!

Every year we hold a photo competition and exhibit in association with our open access image repository, Imaggeo and our annual General Assembly. There is also a moving image competition, which features a short clip of continuous geoscience footage. Pre-registered conference participants can take part by submitting up to three original photos and/or one moving image on any broad theme related to the Earth, planetary and space sciences.

How to enter

You will need to register on Imaggeo to upload your image, which will also be included in the database. When you’ve uploaded it, you’ll have the option to edit the image details – here you can enter it into the EGU Photo Contest – just check the checkbox! The deadline for submissions is 1 March.