Power Interruption Today

The SDO.gsfc.nasa.gov website will be unavailable today from 7:00 am - noon ET while work on the electrical supply to the building takes place.

Station Keeping Maneuver #17 is Today

SDO will perform Station Keeping (or Delta-V) Maneuver #17 today between 2200-2250 UTC (6:00-6:50 p.m. ET). This maneuver is used to keep SDO inside its box in the geosynchronous belt. SDO thrusters will expel 82 grams of propellant to complete the maneuver.

During the maneuver science data may be missing or blurry.

Comet Offpoint Test Looked Great!

The comet offpoint test SDO ran very smoothly yesterday. Here is an AIA 171 Å image from 1441 UTC (10:41 am ET). The image of the Sun has been shifted back to the middle of the frame so the offpoint doesn't look so jarring in the daily movies.

If this had been a real comet observation the scientists would want to examine the missing right-hand side for the comet tail. AIA 171 Å was our best channel for looking at the comets.

My thanks to the SDO Flight Operations Team for making the test look easy.

Comet Offpoint Test, August 8, 2018

Tomorrow morning, from 1430-1505 UTC (10:30-11:05 ET), SDO will perform a comet offprint test maneuver. This is only a test, there is no comet that will be visible. However, it has been almost 6 years since we performed such a maneuver and its good to keep in practice. We only get a day or two notice when a Kreutz sun-grazing comet might be visible. This test allows us to put the instructions in a easy to access location for the next comet.

The Sun will appear to shift to the left during the test. That means it is useful for Kreutz comets in July and August, when the comets appear to come from the right and pass across the face of the Sun. Some science data, such as magnetograms and Dopplergrams, will not be produced while the Sun is shifted from the center of the images.

When a sun-grazing comet arrives, we will be ready to go comet watching!

Today's Maneuver and Schedule for the rest of 2018

Today at 1500 UTC (11:00 am ET) SDO will perform the HMI roll. The spacecraft rolls once around the axis pointed towards the Sun to provide calibration information for the instruments. These measurements are also used to learn how round the Sun is.

Here are other planned maneuvers through the rest of 2018.

• 07/18 @ 1945 UTC (3:45 pm ET) - Momentum Management #32
• 07/21 @ 0433 UTC (12:33 am ET) - Handover Season Starts with First Handover
• 07/25 @ 1230 UTC (8:30 am ET) - EVE Cruciform
• 08/08 @ to be determined - Simulated comet observation
• 08/12 @ 0710 UTC (3:10 am ET) - Fall 2018 Eclipse Season Starts
• 08/15 @ 2225 UTC (6:28 pm ET) - Station Keeping #17
• 09/04 @ 0654 UTC (2:54 am ET) - Fall 2018 Eclipse Season Ends
• 09/09 @ 2030-2130 UTC (4:30-5:30 pm ET) - Lunar Transit, 92% obscuration
• 09/10 @ 0152-0241 UTC (9:52-10:41 pm ET) - Lunar Transit, 34% obscuration
• 09/18 @ 0405 UTC (12:05 am ET) - Last Handover Completes & Handover Season Ends
• 11/07 @ 2024-2116 UTC (3:24-4:16 pm ET) - Lunar Transit, 44% obscuration
• 12/12 @ to be determined - Momentum Management #33

The pair of Lunar Transits on September 9th and 10th are separated by approximately 4 hours 22 minutes, so they are considered separate events. However, the relative motion of SDO and the Moon cause what could be a single transit to split into two. We will discuss this more as we approach the transits.

The sun and moon will be separated by 0.604° on August 21, 2018. (The Sun is 0.5° across, so the Moon is not in the field of view of the SDO images.) This is not close enough to be flagged as a transit, but the proximity may be of interest.

Today's Maneuvers

Today SDO is performing the EVE Field of View and HMI Flatfield calibration maneuvers. Between 1315 and 1910 UTC (9:15 am - 3:10 pm ET) SDO will move in patterns about the Sun. Science data may be unavailable at these times or blurry. Here is an AIA 193 Å image from 1354 UTC with the bottom right corner of the Sun cutoff by SDO pointing away from the center of the Sun.

Annie Scott Dill Maunder, Solar Physicist

The Royal Greenwich Observatory (RGO) dedicated a new telescope on June 25, 2018, returning a tradition of observations to London. The telescope is called the Annie Maunder Astrographic Telescope (AMAT), in honor of Annie Maunder, a famous solar and stellar astronomer who worked at RGO from 1891 until the 1930’s.

The RGO is best known to solar scientists as the place where sunspot pictures were made from 1874 until 1976. Those photographs have been used by many scientists to understand how sunspots behave. Having photographs allows us to go back and remeasure the sunspot properties to see if something was missed.

Annie Maunder studied the Sun at RGO. She worked with her husband (E. Walter Maunder) for many years. After they were married she was unable to get paid for her work but continued her research into the Sun, sunspots, and whether the Sun affected our climate.

Along the way, she helped develop the Butterfly Diagram (1904 and 1922), wrote a popular book on the Sun (1908), and examined the Maunder Minimum, the period from 1645 to 1715 when few sunspots were seen and the climate in England was colder than average (1894). She traveled to far-flung places and photographed solar eclipses, all at a time when women were not supposed to do such things. Her outstanding research led to her election as a fellow of the Royal Astronomical Society in 1916, the first female ever to be admitted to the Society.

The original butterfly diagram appeared in the Monthly Notices of the Royal Astronomical Society in 1904 and again in the 1908 book The Heavens and Their Story. Here is the 1904 version, copied from the journal article. It is easy to see that sunspots follow a pattern. They start at higher latitudes at the beginning of the cycle and form at lower and lower latitudes as the sunspot cycle continues. There is nothing special about solar maximum either (the two thick lines mark solar maximum for Solar Cycles 12 and 13.) Sunspots continue to appear closer to the equator until solar minimum. Then the cycle repeats.

I used the RGO sunspot reports collated by David Hathaway to generate a modern butterfly diagram. The thick dashed line shows when RGO stopped taking data in 1976 and the US Air Force tool over. The data set continues until 2016 when Hathaway retired. Each sunspot cycle is a little different, but they all share the high latitude to low latitude progression.

We still use the butterfly diagram to study the Sun. Any paper studying the solar dynamo will probably include one just to show how well their model works. We also can use helioseismology to generate butterfly diagrams inside the Sun. These show that sunspot cycles start much earlier than sunspots can measure.

My thanks and appreciation to Annie Maunder. Please go and use the AMAT at RGO soon!