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Aurora observation with ORCA®-Quest
Published on February 18, 2024
The Hosokawa Laboratory from the Department of Communication Engineering and Informatics at The University of Electro-Communications uses a high-sensitivity camera to observe auroras.Observation of auroras requires a high frame rate to capture morphology and dynamics, high sensitivity to detect dark auroras, low noise for smooth analysis of acquired images, and large sensor size for wide-field imaging. The ORCA-Quest qCMOSⓇ camera solves these problems.
We interviewed Prof. Keisuke Hosokawa about the reasons for introducing ORCA-Quest, his impressions of using it, and his prospects for future research.
About the research
Could you tell us about your research?
Our laboratory is imaging auroras using high-sensitivity cameras at multiple locations in Northern Europe and Alaska to observe the pulsating aurora, which pulsates with a period of a few to several tens of seconds.
The Pulsating Aurora Project started in 2015. We use a Hamamatsu Photonics EM-CCD camera (ImagEMⓇ) for high-speed, high-sensitivity imaging. We combine ground-based aurora imaging using this camera with observations from the European Incoherent Scatter (EISCAT) radar, the Arase (ERG) satellite. launched in December 2016, and the Pulsating Aurora rocket experiment (LANP mission) launched in 2022. Through this combined approach, we aim to elucidate the origin of pulsating aurora.
Skibotn Observatory, Norway
Prof. Keisuke Hosokawa
Problems in aurora imaging
What problems do you face when imaging auroras?
The main problems with aurora imaging are
- Sensitivity to detect dark aurora
- Spatial resolution for detailed observation of auroral morphology
- Camera noise negatively affects data analysis
First, regarding camera sensitivity, previously I used an EM-CCD camera (ImagEM) manufactured by Hamamatsu Photonics. The EM-CCD camera can capture images with extremely high sensitivity by multiplying the incident electrons, making it ideal for high-temporal-resolution aurora observations. However, the large pixel size and low pixel count of EM-CCD cameras limited the spatial resolution for wide-field observations, making it difficult to observe auroral morphology in detail.
As mentioned earlier, the spatial resolution of EM-CCD cameras was a limiting factor. Therefore, we were seeking a camera that could provide higher spatial resolution while maintaining sensitivity. When Hamamatsu Photonics introduced the high-sensitivity and high-resolution ORCA-Quest qCMOS camera, we were excited about the possibility of improving the spatial resolution of our imaging system.
Regarding camera noise adversely affecting data analysis, we need to use a camera with as little noise as possible, because any signals other than the aurora in the captured image will negatively affect the subsequent data analysis. EM-CCD cameras can improve the S/N by multiplying the signal. However, multiplying the signal adds a large noise called excess noise, which causes fluctuations in the background of the acquired image and makes image analysis difficult.
ORCA-Quest inside the dome of the Skibotn Observatory, Norway
Deciding factors for introducing ORCA-Quest
What were the deciding factors for choosing ORCA-Quest?
The most decisive factor in our decision to use ORCA-Quest was its extremely high resolution. While the EM-CCD camera has 512 × 512 pixels, ORCA-Quest has 4096 × 2304 pixels, which is much larger. In addition, each pixel is 4.6 μm × 4.6 μm, whereas the EM-CCD camera is 16 μm × 16 μm, so the ORCA-Quest can observe the aurora with a much higher spatial resolution than the EM-CCD camera. Although the imaging range has changed slightly, the spatial resolution is about 10 times better in images taken with the ORCA-Quest compared to the EM-CCD camera.
Regarding sensitivity, ORCA-Quest is slightly less sensitive than an EM-CCD camera with a large pixel size and an electron multiplication function, but it can detect even quite dark phenomena because the readout noise is very low. EM-CCD cameras can increase the signal by electron multiplication, but the excess noise had a bad effect on the analysis. On the other hand, ORCA-Quest does not generate excess noise because it does not use electron multiplication. In addition, readout noise and dark current noise are very low, so data analysis can be performed without being affected by noise, which is also attractive.
Observation examples
Curtain-shaped aurora
Data courtesy of Hosokawa Laboratory, Department of Communication Engineering and Informatics, The University of Electro-Communications, Dr. Keisuke Hosokawa
Scan mode: Ultra-quiet scan
Frame rate: 20 frames/s (2048 pixels × 1152 pixels)
Binning: 2 × 2
Wavy aurora
Data courtesy of Hosokawa Laboratory, Department of Communication Engineering and Informatics, The University of Electro-Communications, Dr. Keisuke Hosokawa
Scan mode: Ultra-quiet scan
Frame rate: 20 frames/s (1024 pixels × 576 pixels)
Binning: 4 × 4
Observation data management
Are you constantly running your camera to observe the aurora? How do you manage the data acquired by ORCA-Quest?
Since the occurrence of auroras is unpredictable, we typically capture images every night. This requires a large storage system to save the image data, but storage capacity is limited. We also need to transfer the observed data from the observation site to Japan via the Internet. Therefore, we want to minimize unnecessary data, such as images without auroras.
To achieve this, we are currently developing a program that uses AI for automatic classification. We plan to automatically classify images captured at night using AI during the daytime, keeping only the images containing auroras and deleting unnecessary data. The development of an AI for automatic classification (Tromsø-AI) is already well underway, and we plan to test it in a real observation site soon. By doing so, we can reduce the amount of unnecessary data and save storage space.
Furthermore, as a future development of AI-based observations, we aim to automatically detect not only the occurrence of auroras but also detailed information such as the type and brightness of auroras in real-time, and optimize camera parameters for image acquisition. For example, when fast-moving auroras appear, we would like to shorten the camera's exposure time to achieve high temporal resolution, and when very faint auroras appear, we would like to lengthen the exposure time or use binning to increase sensitivity.
Prospects for research
What are your future research plans?
For future research prospects, I am mainly considering the following:
- Elucidation of the role played by mesoscale auroras with spatial scales below 100 km
- Multidimensional data analysis using ground-based observation data from EISCAT_3D, the Arase satellite, , ORCA-Quest, etc.
- Construction of a multipoint optical observation network using multiple ORCA-Quests
Regarding point 1, the mechanisms of mesoscale auroras with fine structures could not be elucidated due to the insufficient spatial resolution of conventional cameras. With the introduction of ORCA-Quest, which has improved spatial resolution, combined with observations from the EISCAT_3D radar currently being developed through international collaboration, we aim to accelerate the elucidation of mesoscale aurora mechanisms.
Regarding point 2, in addition to the aforementioned ORCA-Quest and EISCAT_3D, by combining data from the Arase satellite, we can obtain aurora data from both ground and space perspectives, enabling a multidimensional analysis of aurora mechanisms.
However, to carry out point 2, all of the following conditions must be met:
- The Arase satellite must pass over the observation range of the camera and radar
- Aurora must be present when Arase passes over
- The weather must be clear (not cloudy) when the aurora is present
Since we cannot control the timing of aurora appearances or the weather, we are advancing point 3: the construction of a multipoint optical observation network using multiple ORCA-Quests. This will allow us to cover as wide an area as possible under the orbit of Arase. By placing three cameras at different locations and combining the observed data like a patchwork, we can observe a wide area. We have already purchased the cameras, so we are currently in the process of installing them and waiting for EISCAT_3D to become operational.
EISCAT_3D radar
Arase satellite
Image courtesy of (C)ERG science team
Researcher profile
Prof. Keisuke Hosokawa
Department of Communication Engineering and Informatics, The University of Electro-Communications, Hosokawa Laboratory, Professor
Mar. 2003
Department of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Ph.D.
Apr. 2004
Assistant researcher, Department of Information and Communication Engineering, The University of Electro-Communications
Apr. 2007
Assistant Professor, Department of Information and Communication Engineering, The University of Electro-Communications
Jun. 2012
Associate Professor, Department of Information and Communication Engineering, The University of Electro-Communications
Apr. 2019
Professor, Department of Computer and Network Engineering, The University of Electro-Communications
Apr. 2024
Director, Center for Space Science and Radio Engineering, The University of Electro-Communications
Related product
The ORCA-Quest 2 is a new qCMOS® camera, the successor to the ORCA-Quest with further advances such as faster readout speeds in extremely low-noise scan mode and increased sensitivity in the ultraviolet region.
Other case studies
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