Outage and EVE Cruciform

AIA images have been sporadically available this week as AIA recovers from a computer failure and we work out alternate paths to create the images posted to the Sun Now and Sun Today websites. At this time some images are being posted at a 3-minute cadence rather than the normal 15-minute cadence. If this causes a problem when browsing the images please use the NTH option to display every 5th image. We are sorry for any inconvenience.

Yesterday we ran the EVE cruciform. Some images are missing and others are cropped or partial as the spacecraft moves along the path needed to help calibrate the EVE instrument.

Maneuvers and Images

Today we start several calibration maneuvers, one each week for three weeks. First is the HMI Roll, scheduled to run for 7.5 hours starting at 1800 UTC (2 pm ET). Data will flow during this maneuver, whose purpose is to measure the optical properties of the HMI and AIA instruments. Although in the past we have seen the Sun flip over during the roll, the processing of the images should remove this effect. After that we have:

October 19: 1315 UTC (9:15 am ET) EVE Field of view; 1630 UTC (12:30 pm ET) HMI/AIA Flat-Field

October 26: 1830 UTC (2:30 pm ET) EVE Cruciform (4.5 hours)

October 27: Fall handover season ends

SDO Weekly Report for October 7, 2011

The Flight Operations Team monitored the end of eclipse season on 10/4. The FOT postponed lowering the spacecraft bus voltage to accommodate a request from the Atmospheric Imaging Assembly (AIA) team to provide more heater power for a 36 hour bake-out of ATA #4. The bake-out was performed successfully on 10/4-10/5. The bus voltage was reduced on 10/6 to the normal full sun voltage to maintain the battery at 60% state of charge.

Unexplained Outage of He II 304 Images

ATA #4 of AIA was heated to drive off contaminants that have been building up. Both the 304 and 94 Å channels were unavailable Tuesday evening and most of Wednesday.

Sorry for the inconvenience.

German-American Day 2011 and the Discovery of the Solar Cycle

Today, October 6, 2011, is German-American Day, when we celebrate the arrival of German immigrants in Philadelphia in 1683. Germans have worked in physics for many years. Joseph Fraunhofer discovered the spectral lines in the Sun we call Fraunhofer lines. We measure the brightness, Doppler shift, and magnetic field effects of those spectral lines on SDO to study solar activity. At left we show the spectrum near the iron line at 6173 Å used by HMI to measure the velocity and magnetic field at the surface of the Sun. The slight motion to the left and right is what happens as the surface moves back and forth.


Another German, Heinrich Schwabe, wrote down the number of black specks he saw on the Sun for almost 20 years. When plotted we see the number of spots rising and falling with about a 10 year cycle. Schwabe had discovered the solar cycle. Here is a plot of Schwabe's data from his article Sonnen-Beobachtungen im Jahre 1843. The rise and fall can be seen in the crosses that show the number of spots in each year. I drew a sine curve with a 10 year period so you can see what Schwabe announced. Also called the 11-year sunspot cycle, we still measure the number of spots and produce the Sunspot Number. Along the way we have invented many more ways to measure spectra and active regions.

Happy German-American Day!

Help us find a comet

We are posting these videos for public review and would like your help in locating a comet that maybe visible from the AIA telescopes. At 2011/10/01 13:25, a sun-grazing or Kreutz comet could be seen by LASCO C2 (see first video) barreling towards the sun. At 2011/10/01 18:12, it entered the occulting disk and we believe the AIA telescopes may have viewed the comet stepping across the face of the sun. For the highest quality videos right click on the links below the videos and save them to your computer. This video posted on youtube is an example of what you're looking for. If you do find our missing comet tweet your finds to @NASA_SDO.

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Do sun-grazing comets cause CMEs? Check out http://sungrazer.nrl.navy.mil/index.php?p=news/comets_cmes for some thoughts about the coincidences between comets, occulter disks, and CMEs.


AIA 171


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Link to youtube version


AIA 193


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Link to youtube version


AIA 211


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Link to youtube version