The Helioseismic and Magnetic Imager (HMI) on SDO observes the sun through a glass window. The window can change shape in response to temperature changes, and does so dramatically and quickly when it doesn't directly feel the sun's heat.
\"You've got a piece of glass looking at the sun, and then suddenly it isn't,\" says Dean Pesnell, the project scientist for SDO at NASA's Goddard Space Flight Center in Greenbelt, Md. \"The glass gets colder and flexes. It becomes like a lens. It's as if we put a set of eye glasses in front of the instrument, causing the observations to blur.\"
To counteract this effect, HMI was built with heaters to warm the window during an eclipse. By adjusting the timing and temperature of the heater, the HMI team has learned the best procedures for improving resolution quickly. Without adjusting the HMI front window heaters, it takes about two hours to return to optimal observing.
Over the two years since SDO launched in 2010, the team has brought the time it takes to get a clear image down from 60 minutes to around 45 to 50 minutes after an eclipse. \"We allocated an hour for these more blurry images,\" says Pesnell. \"And we've learned to do a lot better than that. With 45 eclipses a year, the team gets a lot of practice.\"
SDO will enter its next eclipse season on March 3, 2013.", "items": [], "extra_data": {} }, { "id": 348003, "url": "https://svs.gsfc.nasa.gov/11111/#media_group_348003", "widget": "Single image", "title": "", "caption": "", "description": "Comparison of HMI Continuum images immediately after an eclipse, and then after the sensor has re-warmed.", "items": [ { "id": 316605, "type": "media", "extra_data": null, "title": null, "caption": null, "instance": { "id": 471766, "url": "https://svs.gsfc.nasa.gov/vis/a010000/a011100/a011111/HMI_Blur_Comparison.jpg", "filename": "HMI_Blur_Comparison.jpg", "media_type": "Image", "alt_text": "Comparison of HMI Continuum images immediately after an eclipse, and then after the sensor has re-warmed.", "width": 2048, "height": 1024, "pixels": 2097152 } }, { "id": 316607, "type": "media", "extra_data": null, "title": null, "caption": null, "instance": { "id": 471768, "url": "https://svs.gsfc.nasa.gov/vis/a010000/a011100/a011111/HMI_Blur_Comparison_web.jpg", "filename": "HMI_Blur_Comparison_web.jpg", "media_type": "Image", "alt_text": "Comparison of HMI Continuum images immediately after an eclipse, and then after the sensor has re-warmed.", "width": 320, "height": 160, "pixels": 51200 } }, { "id": 316608, "type": "media", "extra_data": null, "title": null, "caption": null, "instance": { "id": 471769, "url": "https://svs.gsfc.nasa.gov/vis/a010000/a011100/a011111/HMI_Blur_Comparison_thm.png", "filename": "HMI_Blur_Comparison_thm.png", "media_type": "Image", "alt_text": "Comparison of HMI Continuum images immediately after an eclipse, and then after the sensor has re-warmed.", "width": 80, "height": 40, "pixels": 3200 } }, { "id": 316609, "type": "media", "extra_data": null, "title": null, "caption": null, "instance": { "id": 471770, "url": "https://svs.gsfc.nasa.gov/vis/a010000/a011100/a011111/HMI_Blur_Comparison_web_searchweb.jpg", "filename": "HMI_Blur_Comparison_web_searchweb.jpg", "media_type": "Image", "alt_text": "Comparison of HMI Continuum images immediately after an eclipse, and then after the sensor has re-warmed.", "width": 320, "height": 180, "pixels": 57600 } }, { "id": 316606, "type": "media", "extra_data": null, "title": null, "caption": null, "instance": { "id": 471767, "url": "https://svs.gsfc.nasa.gov/vis/a010000/a011100/a011111/HMI_Blur_Comparison.tif", "filename": "HMI_Blur_Comparison.tif", "media_type": "Image", "alt_text": "Comparison of HMI Continuum images immediately after an eclipse, and then after the sensor has re-warmed.", "width": 2048, "height": 1024, "pixels": 2097152 } } ], "extra_data": {} }, { "id": 348004, "url": "https://svs.gsfc.nasa.gov/11111/#media_group_348004", "widget": "Single image", "title": "", "caption": "", "description": "Full resolution HMI continuum image from September 25, 2012 at 07:26:17 UT. 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Any spacecraft observing the sun from an orbit around Earth has to contend with such eclipses. But SDO's orbit is designed to minimize their occurrence as they also cause a temporary blurring of images in one of its instruments. The most recent eclipse season took place September 6-29, 2012. As Earth entered and exited SDO's field of vision, its advanced imaging instruments captured partial views of the sun at multiple wavelengths. Solar scientists do not get much use from these images, though atmospheric researchers may be able to gain some insights by observing the sun's light as it moves through Earth's atmosphere. Watch the video to see images of Earth passing between the sun and SDO. || ", "release_date": "2012-11-08T00:00:00-05:00", "update_date": "2023-05-03T13:52:38.834187-04:00", "main_image": { "id": 470945, "url": "https://svs.gsfc.nasa.gov/vis/a010000/a011100/a011124/cover-1024.jpg", "filename": "cover-1024.jpg", "media_type": "Image", "alt_text": "See how Earth interrupts NASA's constant watch of the sun.", "width": 1024, "height": 576, "pixels": 589824 } } ], "sources": [], "products": [], "newer_versions": [], "older_versions": [], "alternate_versions": [] }