XRT observes a solar eclipse. Click the image to watch a movie of the eclipse or click here for the youtube link.
Mission to Capture a Sliver of the Sun
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Solar eclipses occur when the Moon comes across the straight line between the Sun and the Earth. On 29 March, 2025, the Moon traveled slightly North of this straight line and the shadow of the Moon barely covered the arctic area of the Earth. This gave the people down there the opportunity to see a partial solar eclipse on that day. This also gave the Hinode satellite, as it has a polar orbit with the period of about 90 minutes, 3 opportunities to dive into the shadow. This is the movie of XRT observations through the following 3 events. 09:20:05 UT (1st contact) -- 09:31:48 (4th contact) 10:46:17 UT (1st contact) -- 10:59:52 (4th contact) 12:15:18 UT (1st contact) -- 12:25:57 (4th contact) According to the above predictions, the deepest eclipse occurs in the 2nd event: Moon is supposed to cover more than 90% of solar disk at around 10:53 UT. While taking a footage of the entire process of the eclipse, we decided to capture the sliver of the Sun with a quality better than images of other periods. For the purpose of record and future reference, we describe below the preparation and results of our eclipse observation on 3/29. [preparation] As general notes, eclipses should be observed with ... - thinner filter (disk should be bright to see the Moon passage) - short/long fixed exposure pairs (AEC makes harder to correct saturation by composite) - cadence less than 30 sec for better movie (Moon moves fast!) - 4x4 binning, 512x512 pix sequence (to save telemetry & keep cadence) For this eclipse, 2x2 (1024x1024) images were specially inserted at the predicted max time (e.g, 10:52 UT for the 2nd event) to capture the deepest occulted Sun. The new XOB#1D2C was created for the 2nd event which has the deepest occultation at 10:53:05 UT. For the 1st and 3rd events, this XOB is a bit longer, but we can still use it by stopping it at the time the event is over. Below is the summary of this XOB: ---------------------------------------------------------------- XOB#1D2C: takes 20.46 min (duration) and 216 Mbits (data volume). Sub-A : G-band 1ms VLS on/off pair + dark Sub-B : [B1] Al_poly 4x4 512x512 45/256ms pair AEC0 20s cad.(first 11min) [B2] Al_poly 2x2 1024x1024 1.4sec fixed exp. 2 times (~10:53 UT) [B3] repeat [B1] (9 min) ---------------------------------------------------------------- Note that the eclipses on 3/29 occur in the time range overlapped with Hinode operations. The 2nd event, in particular, comes right after the pass of XRT table upload (10:22:46(AOS) - 10:34:01(LOS) at USC20). Hinode team decided to observe the eclipse events in the timeline uploaded on Thursday (3/27) by delaying the OP start to around 14UT. The eclipse XOB was therefore included in the 3/27 timeline and was uploaded once again in the timeline uploaded on 3/29 to keep it onboard after the XRT table upload. [results] Hinode survived the eclipse periods, XOB worked as prepared, and the quality of data is decent. So I'd say our eclipse observations were successful! The only negative side was that the eclipse events started 40-45 seconds earlier than the prediction: we consequently failed to take a shot of a sliver of the Sun with a 1024x1024 image. The prediction we received a few weeks ago told that the max occultation of the 2nd event will be at 10:53:05 UT but it actually occurred at around 10:52:21 UT. The Sun in our 1024x1024 images is therefore a little fatter than the 4x4 image obtained earlier (as seen in the top image). This is probably because of Hinode's orbital elements, slightly changed from the time when the prediction was made (3/11). The lesson learned is that we need the latest calculated prediction in order to capture the special moment with a special setting. Keywords: Eclipse, Full Disk Filters: Al_Poly |
(Prepared by Aki Takeda & Keiji Yoshimura)
The XRT instrument team is comprised of SAO, NASA, JAXA, and NAOJ.
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