Friday, June 14, 2019

Listening to the Sun

Ever wish you could listen to SDO data? We have developed new ways to do just that!

This week the American Astronomical Society and the AAS Solar Physics Division had a joint meeting in St Louis. Astronomers and solar physicists got together to discuss our latest papers on understanding the Sun and universe.

Two of those papers were "Listening to the Sun" (by Kyle Ingram-Johnson, W. Dean Pesnell, and Kevin Addison) and "Listening to the Sun: the Sonification of Solar Harmonics Project" (by tim larson, Seth Shafer, and Elaine diFalco). Both papers allow you hear different kinds of SDO data. They were presented as iPosters, so they are available at the links below for others to read through and enjoy.

This paper converts several solar indices to sound before sonifying AIA images in three ways. You can listen to the entire image, small subsets of the image, and a series of images that shows a filament liftoff. We used a special math curve called a Hilbert curve to walk around the image and convert the pixels values into a set that can be then converted to sound. You should listen to the difference between the full image sonified with a Hilbert curve and sonified with a left-right scan. You will see a big difference.

The next paper shifts HMI sound waves from their very low frequency of about 3 mHz to about 3 kHz so you can hear the tones.

You are working to allow you to sonify images, both the entire image and as subsets, on the SDO website. Look for that new feature in the future.

Until then, please enjoy listening to the Sun!

Wednesday, May 1, 2019

Momentum Management Maneuver #34 Today

SDO will execute Momentum Management Maneuver #34 (MM#34) today from 1845-1915 UTC (2:45-3:15 pm ET). During a maneuver the science data may be unavailable or blurred.

Wednesday, April 24, 2019

SDO Maneuvers Today

SDO will execute two calibration maneuvers today. The EVE Field of View maneuver will run from 1315-1600 UTC (9:15 am-12 noon ET). The HMI/AIA Flatfield maneuver will then run from 1630-1907 UTC (12:30 pm-3 pm ET). During the maneuvers images may be blurred or absent. These maneuvers were delayed to provide data during the perihelion passage of the Parker Solar Probe earlier this month.

Thursday, April 4, 2019

SDO Plans for the Next Eight Months

Significant events in SDO's timeline are below. Calibration maneuvers are still being scheduled as we await the launch of CLASP-2 at White Sands and for the completion of the second perihelion pass of Parker Solar Probe.
  • 01 May 2019 @1845 UTC (1445 ET) – Momentum Management Maneuver #34
  • 19 Jul 2019 @0443 UTC (0043 ET) – First Handover Begins and Handover Season Starts (-Z HGA Active Prior)
  • 08 Aug 2019 @0709 UTC (0309 ET) – Fall Eclipse Season Starts
  • 12 Aug 20194 @TBD – Momentum Management Maneuver #35 (Tentative Date)
  • 28 Aug 2019 @2222 UTC (1822 ET) – Station Keeping Maneuver #19 (Tentative Date)
  • 01 Sep 2019 @0659 UTC (0259 ET) – Fall Eclipse Season Ends
  • 12 Sep 2019 @0515 UTC (0115 ET) – Last Handover Completes and Handover Season Ends (+Z HGA Active After)
  • 28 Sep 2019 @2043-2116 UTC (1643-1717 ET) – Lunar Transit - Video to follow
  • 11 Nov 2019 @1236-1802 UTC (0736-1302 ET) – Mercury Transit - Video to follow

Thursday, March 7, 2019

That's a Transit!

The long lunar transit SDO saw last night was quite a show. Here's a movie in AIA 171 Å from March 6, 2000 UTC, to March 7, 0400 UTC (March 6, 3:00-11:00 pm ET) showing the entire transit. The Moon touched the limb of the Sun at 2200 UTC and finally left the solar disk at 0207 UTC). During the transit the Sun moves in the frame as the spacecraft and telescopes cool and shiver in the lunar shadow.
Congratulations to the flight dynamics team for predicting a beautiful display of orbital mechanics.

Wednesday, February 27, 2019

Station Keeping Maneuver #18 Today

SDO will perform station keeping maneuver #18 (SK#18) today from 2225-2300 UTC (5:25-6:00 pm ET). During this time SDO data may be blurry or missing. These maneuvers are performed to keep SDO within the longitude limits assigned to our geosynchronous orbit. I'm sure our neighbors appreciate us staying inside the box!

Tuesday, February 19, 2019

Another Nifty Lunar Transit from SDO

The previously scheduled station-keeping maneuver is delayed until next week (February 27). It's time to talk the lunar transit of March 6-7, 2019.

From 2200 UTC on March 6,2019, until 0207 UTC on March 7 (5:00-9:07 pm ET, March 6) SDO will experience a lunar transit. The Moon will cover up to 82% of SDO's view of the Sun. This four-hour transit looks similar to the double transit of September 9-10, 2018, except that the shadow of the Moon is visible through the entire transit. Here is a movie from the Flight Operations Team that shows SDO, the Sun, and the Moon during the transit.

The Moon moves from lower left to upper right in the images during the first half of the transit and upper right to lower left for the second half. The first part of the transit is caused by SDO overtaking the Moon as SDO moves in the afternoon part of its orbit. (SDO orbits over the Mountain Time Zone of the USA so the transit happens from 3:00-7:06 MT.) SDO's velocity of about 3 km/s is faster than the Moon's of 1 km/s and SDO overtakes and moves past the Moon-Sun line. The second part of the transit happens as SDO moves into the dusk part of SDO's orbit around the Earth and is now moving mostly away from the Moon. The Moon's velocity takes it past SDO and the shadow appears to move from right to left across the Sun.
When I first saw this movie I thought we were going to talk about retrograde motion. Other planets, notably Mars, move in retrograde when the Earth moves between them and the Sun with our faster orbital velocity. But it isn't just that. The first part of the transit is like retrograde motion as SDO passes by the Moon-Sun line with its faster velocity and the Moon appears to move backwards. But the second part of the transit happens because SDO is moving mostly away from and even a little in the opposite direction of the Moon.
I created two videos to help understand what’s happening. The first shows why Mars appears to have retrograde motion and the second explains the extended lunar transits seen in September 2018 and March 2019.

Retrograde motion is the apparent backwards motion of an outer planet among the stars as the Earth moves past the line connecting the Sun and the outer planet. In this movie Mars is a red disk and the Earth is a blue disk moving in their orbits around the yellow disk of the Sun. A line is drawn connecting the Earth and Mars and extended out into space. A colored dot is drawn where an observer on the Earth will see Mars against the distant stars. The color of that dot then changes from red to blue as the Earth overtakes Mars in it's orbit. Those dots show that the path of Mars seen from Earth traces out a lazy Z in the stars. In this example the Z is centered about the time the Sun, Earth, and Mars are lined up.

The other video shows the situation for SDO's lunar transit on March 6. There is no line connecting SDO and the Moon, only the shadow of the Moon. SDO and the Moon are started at about the right times in their orbits and you can see the shadow line hits the grey disk of SDO as the satellite moves through the afternoon and dusk parts of the orbit. In the first part of the transit SDO moves across the black line from left to right across the Sun (so the Moon appears to move from left to right across the Sun.) During the second part of the transit SDO moves across the black line from right to left and the Moon moves in the opposite direction from the first.
During the total solar eclipse in August 2017 the Moon's shadow moved from the West coast of the US towards the East. This is because the speed of the rotation of the Earth (less than 0.5 km/s) is slower than the speed of the Moon. So the Moon overtakes the people on the rotating Earth. The shadow follows the Moon and moves from West to East, like the second part of the transit.
Although you can see the Moon throughout the movie SDO's instruments cannot see the Moon when it is not covering the Sun. The little white flash seen in the Moon is the word &ldquot;Moon&rdquot; being written by the software and then quickly covered. The boxes drawn on and around the Sun help the FOT run the spacecraft. The time is displayed in the lower left corner of the movie. The first seven numbers are the year (2019) and the day of year (065 and 066). The six numbers after the period are the hour, minutes, and second of UTC (2 numbers each).
One detail was left out of the discussion. A transit can only if the Sun, Moon, and SDO are in a line. The Moon's shadow has a small angle rather than the straight line in the movie. This means the model shown here is too simple, but it still explains why we see the long lunar transits with the Moon changing direction. Look at the FOT movie for a better simulation.

Once again, a lunar transit shows how complicated the motions of objects can appear even as they move along simple orbits.

Enjoy!