Four Lunar Transits April-July 2025

SDO will see 4 lunar transits between April and July 2025. Two look like the Moon is just brushing by the Sun and one is pretty nice looking.
There are lunar transits on April 27, 2025 and April 28, 2025. Here are the movies from the SDO Flight Operations Team.

April 27; Moon covers 23% of the solar disk.

April 28; Moon covers 2% of solar disk.

May 25; Moon covers 4% of solar disk.

July 25; Moon covers 62% of solar disk.

The fourth will be the longest and deepest transit in the first half of 2025.

Eclipse Day Transit was not as Exciting as the Total Solar Eclipse

On April 8, 2024, people along a path from Mexico thru the USA and into Canada were treated to a total solar eclipse. SDO waited until much later in the day (actiually the next day in the UT timezone) and saw this glancing lunar transit.

The Moon covered about 5% of the solar disk at 09-Apr-2024, 03:36 UTC (08-Apr-2024, 11:36 ET). It is an interesting problem to understand why the motion of SDO in its geosynchronous orbit above the Mountain timezone against the lunar velocity later in the day allowed the transit many hours after the eclipse on the ground. Perhaps the next post will explore those details.

You should check out the spectacular photos of the total solar eclipse. There was at least one prominence visible to my eyes on the limb.

09 April 2024 Lunar Transit (08 April for North America)

On April 8, 2024, a large swath of North America will enjoy a Total Solar Eclipse from Mazatlán up through Texas to Maine and the Maritime Provinces of Canada. Although those along the path of totality will enjoy a beautiful view of the solar corona, SDO will only see a short, almost glancing transit of the Moon across the Sun long after the TSE ends. The SDO transit starts at 03:29 UTC on 9 Apr 2024 (10:29 pm EDT on 8 Apr 2024), 7 hours after the TSE ends on the ground.

Here is a movie from the SDO Flight Dynamics Team showing the transit.

The transit will only cover 5% of the solar disk.

If you live in Mexico, USA, or Eastern Canada, please go watch the Total Solar Eclispe. They are a wonderful way to see the Sun in a different light.

18 Jun 2023 Lunar Transit

Between 0557--0612 UTC (01:57--02:12 ET) on 18 Jun 2023, SDO is experience a brief lunar transit. The Moon will cover about 3% of the Sun, but because it will pass over the top diode SDO will leave science mode during the transit.

Here is the Flight Ops Team movie of the transit

I hope everyone is enjoying SDO's view of the Sun as we near the maximum of Solar Cycle 25!

20 May 2023 Lunar Transit and the Long-term Predicts for the 3rd Quarter of 2023

The 2023-094 FDS Quarterly (Long-Set) Predicts have been delivered. They include events through 05 Nov 2023. The highlights are:

• 20 May 2023, 0222--0306 UTC (22:22--23:06 ET) - LunTran_2023140_3dc_82pshdw
• 18 Jun 2023, 0557--0612 UTC (01:57--02:12 ET) - LunTran_2023169_1dc_3pshdw
• 21 Jun 2023, TBD - Tentative date for Momentum Management Maneuver #47
• 04 Jul 2023, 1148 UTC (07:48 ET) - Handover Season Starts with First Handover (-Z HGA Active Prior)
• 20 Jul 2023, 0725 UTC (03:25 ET) - Eclipse Season Starts
• 26 Jul 2023, TBD - Tentative Date for Station Keeping Maneuver #27
• 04 Aug 2023, 1913--1919 UTC (15:13--1519 ET) - Solar RFI
• 05 Aug 2023, 1910--1918 UTC (15:10--1518 ET) - Solar RFI
• 06 Aug 2023, 1909--1916 UTC (15:09--15:19 ET) - Solar RFI
• 15 Aug 2023, 0248 UTC (22:48 ET) - Handover Season Ends with Completion of Last Handover (+Z HGA Active After)
• 16 Aug 2023, 0659 UTC (02:59 ET) - Eclipse Season Ends
• 05 Nov 2023, 0200 ET - Daylight Saving Time Ends, GSFC Local Time now UTC-5:00

(All dates and times in parentheses are GSFC Local time.)

Here is a movie of the predicted 20 May 2023 lunar transit:

And here is what a daily movie shows for that date:

Lunar Transit on June 29, 2022

Tomorrow, June 29, 2022, the Moon will transit the Sun between 0519 and 0554 UTC (01:19 and 1:54 am ET). At its peak the Moon will cover about 67% of the Sun. SDO science data will be unavailable during the transit.

Here's a movie of the transit from the SDO Flight Operations Team.

This transit occurs while SDO is in the midnight sector of its orbit. That means the motions of the Moon and SDO combine to make this a short transit, lasting about 35 minutes.

Enjoy!

Tomorrow is the First SDO Lunar Transit of 2021

January 13, 2021, will see the Moon pass across the face of the Sun between 0556 and 0625 UTC (00:56 and 1:25 am ET). Here's a movie of the transit from the SDO Flight Operations Team.

This transit occurs while SDO is near the midnight sector of its orbit. That means the motions of the Moon and SDO combine to make this a short transit, lasting only about 30 minutes.

Enjoy!

SDO Lunar Transit, October 16, 2020

Just two weeks ago the Full Moon and Mars had a bright conjunction in the night sky. Tomorrow the New Moon will glide between SDO and the Sun for a 47 minute lunar transit. Here's the SDO FOT movie of the transit.

The transit starts at 1906 UTC (3:06 pm ET) and ends at 1953 UTC (3:53 pm ET), so it's at a perfect time for watching in the US. The Moon will cover at most about 44% of the solar disk. More important to SDO, it will cover two of the fine-guidance sensors (the red squares in the movie). This means our view of the Sun may jitter a bit during the transit, but SDO will recover soon after the Moon moves off the disk.
Enjoy the transit, and keep watching the planets Mars, Venus, and Jupiter as they move across the evening sky.

Lunar Transit Last Night!

Yesterday, from 6:00--8:33 pm, the Moon moved between SDO and the Sun. These lunar transits happen a few times each year. Here is the FOT movie of the event, produced last year. The transit covered a maximum of 57% of the Sun.

And here is a 60-hour movie in AIA 171 Å. There are three eclipses of the Sun by the Earth near 0700 UTC on February 22, 23, and 24. The lunar transit starts at 2300 UTC on February 23 and lasts until 0133 UTC on the 24th.

Lunar transits are one interesting feature of life in a geosynchronous orbit.

Lunar Transit on September 28, 2019

SDO will experience a lunar transit on September 28, 2019. Here is a movie from the Flight Operations Team that shows SDO, the Sun, and the Moon during the transit. This transit lasts from 2044-2115 UTC (4:24-5:16 pm ET) and covers at most about 7% of SDO's view of the Sun.
The Moon moves from left to right during this transit. That makes it an SDO-overtake transit.

During the transit SDO will be in inertial mode with the fine-guidance system turned off. Images may jiggle around a little bit, but will continue to be observed and recorded.
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 "Moon" being written by the software and then quickly covered. The boxes drawn around and on 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 (271). The six numbers after the period are the hour, minutes, and second of UTC (2 numbers each).
The next SDO Transit will be the Mercury Transit on November 11, 2019. We will have a webpage dedicated to the transit.
Enjoy!

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.

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!

Happy 9th Anniversary SDO!

Nine years ago today, at 10:23 am ET, SDO rose into the sky atop an Atlas V 401 launch vehicle. Since that day SDO has returned over 350 million images of the Sun, produced over 3000 scientific articles, and allowed millions to enjoy the Sun. Solar Cycle 24 was just starting in 2010. SDO watched it grow to maximum in 2014 and now the Sun is often spotless.

Here is a summary slide of what SDO saw. The AIA 193 Å shows the lower corona and the HMI magnetogram shows the surface magnetic field. We try to understand the Sun by watching what happens at the poles. The dark areas near the North and South poles in the October 2010 and February 2019 193 Å images are the polar coronal holes. They have disappeared by solar maximum (the February 2014 images). The magnetograms show how the Sun's magnetic field gets more complicated at maximum and quite simple at minimum. What happens in the poles at solar minimum seems to be one of our best predictors of future solar activity.

SDO data is the basis of accurate models of the solar corona. Machine Learning algorithms are being used to squeeze even more information out of our 12 PB of data. We are looking forward to another lengthy lunar transit next month and the Mercury transit in November.

You can make your own SDO Anniversary movie at our website sdo.gsfc.nasa.gov or the Helioviewer website.

Happy Anniversary SDO!

Lunar Transit on November 7, 2018

SDO will experience a lunar transit on November 7, 2018. Here is a movie from the Flight Operations Team that shows SDO, the Sun, and the Moon during the transit. This transit lasts from 2024-2116 UTC (3:24-4:16 pm ET) and covers at most about 44% of SDO's view of the Sun.

The Moon moves from left to right during this transit. That makes it an SDO-overtake 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 "Moon" being written by the software and then quickly covered. The boxes drawn around and on 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 (2018) and the day of year (311). The six numbers after the period are the hour, minutes, and second of UTC (2 numbers each).

The next SDO Lunar Transit will be on March 6, 2019. That one will also be a double transit similar to the one in September 2018.

Enjoy!

The September 9-10 Double Lunar Transits

SDO will experience a double lunar transit on September 9 and 10, 2018. Here is a movie from the Flight Operations Team that shows SDO, the Sun, and the Moon during the transits. During the first transit, from 2030-2130 UT (4:30-5:30 pm ET) on September 9, the Moon will cover up to 92% of SDO's view of the Sun. The second transit lasts from 0152-0241 UT on September 10 (or 9:52-10:41 pm ET on September 9 for those of us on the East coast of the USA.) Only 34% of the Sun will be covered by the Moon.

The Moon moves from left to right during the first transit and right to left for the second. The first 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.) 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 transit happens after SDO has moved into the evening part of the orbit and is now moving mostly away from the Moon in SDO's orbit around the Earth. The Moon's velocity takes it past the Sun and the shadow appears to move from right to left.

During the total solar eclipse last year 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. That means the motion of the Moon overtakes the motion of the Earth. The shadow follows the Moon and moves from West to East, like the second 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 "Moon" being written by the software and then quickly covered. The boxes drawn around and on 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 (2018) and the day of year (252 and 253). The six numbers after the period are the hour, minutes, and second of UTC (2 numbers each).

When I first saw this movie I thought we were going to talk about retrograde motion. Other planets, especially Mars, move in retrograde as the Earth moves past them with our faster orbital velocity. But it isn't just that. The first 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 transit happens because SDO is moving mostly away from and a little in the opposite direction of the Moon.

This double transit shows how complicated the motions of objects can appear even as they move along simple orbits.

Enjoy!

Today's Lunar Transit

It was a lovely fall day in Maryland. A perfect day for a lunar transit! Here's an AIA 171 Å image showing the Moon blocking a slice of the Sun.

EVE Field of View and AIA/HMI Flatfield Maneuvers today

The wobbling images tell us that another round of calibration maneuvers has started. Today we have the EVE Field of View and AIA/HMI flatfield maneuvers from 1315-1910 UTC (9:15 a.m.-3:10 p.m. ET).
Next Wednesday SDO will perform the EVE cruciform.

On October 19 we will have another lunar transit. A little deeper than the one on August 21, but still not a total eclipse. Here is the movie showing what it will look like.

Remainder of 2017 Maneuvers and two Lunar Transits

The next set of SDO maneuvers and other niceties has been released.

• July 5, 1818 UTC 1320-1920 UTC (10:20 am ET - 3:30 pm ET) - EVE FOV and HMI/AIA Flatfield
• July 12 - HMI Roll Maneuver
• July 19 - EVE Cruciform Maneuver
• July 23, 1818 UTC (2:18 pm ET) - Handover Season Starts (HGA +Z slew from storage)
• July 24, 0449 UTC (00:49 am ET) - First Handover Begins
• July 26, 1940 UTC (3:40 pm ET) - Momentum Management Maneuver #30
• August 16, 0709 UTC (3:09 am ET) - Eclipse Season Starts
• August 21, 1927-1955 UTC (3:27-3:55 pm ET) - Lunar Transit
• August 30, 2241 UTC (6:41 pm ET) - Station Keeping Maneuver #15
• September 9, 0650 UTC (2:50 am ET) - Eclipse Season Ends
• September 25, 1942 UTC (3:42 pm ET) - Handover Season Ends (HGA -Z slew to storage, +Z Active)
• October 19, 1941-2025 UTC (3:41-4:25 pm ET) - Lunar Transit (26% coverage)
• December 20, Momentum Management Maneuver #31 (tentative)

The movie for the lunar transit has been updated. It isn't changed very much, but it's a nice finale to the Great American Eclipse taking place across the United States that day. From 1927-1955 UTC (3:37-3:55 pm ET) on August 21 the Moon will block up to 14% of the Sun.

Today's Lunar Transit

SDO had another visit from the Moon today, as it passed between SDO and Sun.

Here are two AIA 193 images showing the Moon moving onto and roughly maximum coverage.

Always nice to see another member of the solar system paying a visit. See you again in August!

A Movie of the August 21, 2017, Lunar Transit

Here is a video showing the lunar transit SDO will see on August 21, 2017. While some in the United States will see a Total Solar Eclipse, SDO will see only a glancing transit an hour after the Moon's shadow leaves the US and goes over the Atlantic Ocean.