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A Deeper Look at the SWAP Movie of the March 2015 Eclipse

To read about the PROBA2 eclipse observation campaign and see images of the eclipse, follow this link.

When ESA posted the video of SWAP’s observations of the March 20 solar eclipse on YouTube a number of viewers shared comments and questions about several unexpected aspects of what they saw. A few viewers were so surprised by what they saw that they even wondered if the images were really authentic. The images were most assuredly real, but nonetheless we on the PROBA2 team were likewise intrigued by similarly unexpected things that we saw in the observations.

Some of the questions commenters asked have straightforward — if not exactly simple — answers, while others required us to dig deeper and do some real research of our own to try to address them.

Among the questions raised in the comments were:

  • Why does the Moon move across the Sun from east to west, the opposite direction of motion from what viewers on the ground observed?
  • Why didn’t the Sun appear to rotate in the movies as it does in many movies from PROBA2 and other Sun-observing spacecraft?
  • Why did the Sun change so little during the movies? Shouldn’t there have been some dynamics visible in the corona?
  • Why did the movie play so quickly? Why were there so few frames showing the eclipse?

Let’s have a look at these questions to see what we can learn about the Sun, solar eclipses, and the PROBA2 spacecraft from them.

PROBA2 Views a Total Solar Eclipse - 2015

Updated (25 March 2015): On 2015 March 20, PROBA2 observed a total solar eclipse — twice! The spacecraft's orbit carried it through the darkest parts of the Moon's shadow two times, first between 08:28 and 08:53 UT and again between 10:24 and 10:50 UT. Eclipse chasers, scientists, media and members of the general public have been following our data closely, so we are collecting all of our results and data products in one place for quick access.

SWAP, an Extreme-Ultraviolet solar telescope, observes the solar corona in a passband centered on 17.4 nm. The structures we see in SWAP images have a temperature of approximately 1 million degrees. LYRA, an X-ray/Ultraviolet radiometer observes the total incoming light levels from the Sun in several wavelength bands.

More information about these instruments is available here: SWAP | LYRA.

Exciting press for SWAP

SWAP was recently featured in two ESA stories! SWAP took this week’s Space Science Image of the Week. The image is from 25 July 2014 and is reproduced below. It shows a large coronal-fan structure on the left side of the Sun.

Giving SWAP images a make over - novel image processing techniques

In 2014 Morgan and Druckmuller introduced a new image processing technique to reveal information at the finest scales of solar images, whilst maintaining enough of the larger-scale information to provide context.
Processed SWAP image

A Monster Active Region

Active Region 12209, the same region that gave us a half-dozen X-class solar flares during its last rotation across the Sun, is returning. Currently on the east limb, it is a spectacular sight for SWAP, the EUV imager on-board PROBA2.

SWAP's view of AR 12209 on the east limb of the Sun.


SWAP/PROBA2 Observes Partial Solar Eclipse

On Thursday, October 23, 2014, SWAP, an ultraviolet telescope onboard PROBA2, observed three separate passages through the Moon's shadow, meaning it witnessed three partial solar eclipses in a single day!

SWAP Observations of the 2014 October 23 Solar Eclipse

Recent Improvements to SWAP Image Calibration

Frequent users of SWAP data or watchers of SWAP movies may have noticed some unusual behavior in these images and movies in the last few days. We've been improving the spatial calibration of the data and our tests resulted in a few unusual images, but now that everything is finished you'll notice SWAP images look better and are easier to use than ever before.

Using the SpoCA segmentation suite to track long term variations in EUV observations

A recent paper by Verbeeck, C. et al. entitled "The SPoCA-suite: Software for extraction, characterization, and tracking of active regions and coronal holes on EUV images", in the journal Astronomy & Astrophysics, discusses a new software suite that can be used to track and segment different regions of the Sun from EUV images.



The long-awaited and much-hyped comet ISON surprised astronomers and solar physicists when it mysteriously failed to appear in images from extreme-ultraviolet (EUV) solar telescopes on Thursday. The SWAP solar telescope, on board the Belgium-based ESA mission PROBA2, conducted an extraordinary campaign to image ISON, but failed to detect any sign of the unusual comet.

No Clues from Comet ISON

Comet ISON raced past the Sun on November 28, but left no clues about its structure — or the structure of the solar corona — for extreme-ultraviolet (EUV) telescopes like SWAP that had been turned towards the unique comet in the hope of capturing images of its passage through perihelion.


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