Starlink Satellites, 04 January -
24 April 2020
Starlink is a group of thousands of satellites being deployed by SpaceX into low Earth orbit to provide broadband Internet access. A test flight took place in February 2018 and deployment began, in groups of 60, in May 2019. Because of the test flight, the launch number is one greater than the constellation number, thus the second launch group deployed constellation Starlink 1, and so on.
Second Launch Group, Nigel Evans, 04 January 2020
The second set of 60 Starlink satellites, launched on 11 November 2019, was well-placed for observation in early January 2020. The night of 04 January was clear with a first quarter Moon, but not particularly transparent. The main group of satellites passed virtually overhead. I was able to record 41 of them, including three slightly out-of-plane with the main group, along with several other satellites that passed through the field-of-view (and two aircraft).
In the animation below, the Starlink satellites pass from 2 o'clock to 8 o'clock. Most were invisible to the naked eye in the moonlit sky, but two were very very prominent, with brightness similar to the stars in Cassiopeia.
Fourth Launch Group, Nigel Evans, 12 & 19 February and 16 March 2020
By mid-February 2020, satellites from the fourth Starlink launch on 29 January 2020 had come to visibility in the mornings. The morning of 12 February, although very cold, presented an opportunity to image the objects. The satellites came out of the Earth's shadow at an altitude of about 20°, close to the Moon. The main group consisted of 31 satellites, all in a line with a typical spacing of about 12 seconds. It was possible to see at least 10 satellites at the same time - the sight of them moving as one relative to the stellar background was quite surreal! Towards the end of the pass, one of the satellites was moving visibly faster than the others and overtook another. Currently, most of the satellites are in a circular orbit at an altitude of about 340 km, orbiting the Earth 15.75 times a day, climbing towards an operational altitude of 500-550 km. Starlink 1179 is in a lower orbit of 279x291 km, circling the Earth 15.95 times a day, so appearing to travel 1.3% faster.
I attempted to video the passage of the satellites through the border of Corona Borealis - Serpens. Equipment used: Sony A7S camera, driven, 100 mm telephoto lens at f/2, ISO 16,000. Some acceleration of the event was needed to reduce the size of the video file. The satellites are nominally in the same orbit, but our perspective from the rotating Earth gives the impression that they sweep through a band of the sky. The impact of all the satellites, flashing through the fields-of-view of the telescopes around the word, as shown in the image, remains to be seen.
On the morning of 19 February it was again clear and I took the opportunity to record the passage virtually overhead of the Starlink 3 constellation. I used a fish-eye lens to record the passage. Although the satellites are launched in groups of 60 into a low earth orbit, they start to spread out as they propel themselves into their working orbit at an altitude of 550 km. On 19 February, the main group contained 28 satellites that passed in about 8 minutes. The movie below captures most of the satellites from approximately 05:40:30 to 05:49:50 UT. The still frame, taken at 05:47:11 UT shows 14 satellites. Equipment used: Canon 60Da camera, 8 mm fish-eye lens f/4, ISO 3200, 2 s exposures.
On 16 March, there was an excellent opportunity to catch a train of satellites from Starlink 3 passing directly overhead. Forty of the 60 satellites passed over in a group, one every 25-27 seconds or so, with eight visible at any one time. At this time the objects were mainly in an intermediate circular orbit at an altitude of 380 km.
The video below was taken using a driven mount. The evening sky was not particularly clear, with cirrus cloud present. Use of a fish-eye lens meant that aircraft were a major problem, and removing them from the video was tedious!
Fifth Launch Group, Nigel Evans, 12 March 2020
The morning of 12 March was not very clear, the Moon was up and it was very, very windy, but it was the first opportunity to record the latest constellation of Starlink satellites from the 5th launch on 17 February. The main pack (about 44 satellites out of 60) passed by in an 18-minute window. They were mostly 25-27 seconds apart, not as close as some earlier launch groups have been, but it was still possible to see six or more at once. All bar one object could be identified using the prediction from heavens-above.com: the exceptional object moved like all the others but there was no associated prediction. All the satellites passed close to the star Pherkad (γ Ursae Minoris, magnitude 3.05) which most of them matched in brightness.
I normally use a driven mount when recording Starlink satellites, but I forgot to switch it on initially! As a result, the stacked composite near the beginning of the video shows star trails.
Fifth Launch Group, Mike Whybray, 21 April 2020
My video of the Starlink5 passage on 21 April is below. The two brightest stars in the lower left are Castor and Pollux. The video starts at 21:00 BST. It is cropped and resampled from a sequence of full frame images taken with a Canon 550D using a Samyang 14 mm lens at F4, 2 s exposures.
Sixth Launch Group, Nigel Evans, 07, 19, 20 & 21 April 2020
In early April I finally saw Starlink satellites in the sixth launch group. Conditions were mixed: the atmosphere was cool, calm, silent and still, but the sky was hazy and moonlit with cirrus clouds. I set a camera running, taking images to make a time-lapse movie. I had intended to set up a second camera in video mode, but eventually concluded that conditions did not warrant it.
Usually, with the camera running, I watch the satellites pass overhead, but this time I could not see them. Nevertheless, the camera recorded them together with some additional "features" including a large brightness gradient across the field of view and moving cirrus clouds. (I have removed the gradient in the second part of the video, to give a much more pleasing appearance.)
I don't know why the satellites were so faint. Towards the end of the video, Starlink 80 (placed in orbit in the first launch) can be seen passing above the path of the sixth launch group, and appearing much brighter. Curiously, heavens-above.com does not include magnitude estimates for the sixth launch group, whereas it does for all the others.
By 19 April, heavens-above.com was providing magnitude estimates for Starlink 5, indicating that the satellites would be exceptionally bright. I recorded the passage that night, half expecting another disappointment. Unfortunately, I was late in starting, so missed the first few satellites. I was stunned by how bright the satellites appeared, some appearing roughly as bright as Regulus.
The video below has not been polished - I have not removed the aircraft, nor labelled the satellites.
The passage of the Starlink 5 constellation on 20 April was much different; in fact it was a disappointment! I recorded the passage, using exposures of two seconds, rather than four seconds used on 19 April, other details being the same. In the 20 minute interval from 22:00 - 22:20 BST, some 42 Starlink satellites passed through Ursa Major but a video shows only seven and a multiple exposure only 10.
The passage on 21 April occurred during evening twilight. This made it tricky to record because of the variation in background light level as night fell, necessitating more sophisticated processing of the images than had previously proved necessary! In the video below, the left hand pane is a view of the sky as night falls: it is difficult to see the satellites as the Sun is only 9° below the horizon. (However, dust on the sensor is very clear!) The image was captured using a fish-eye lens with a very wide field of view, showing a wide variation in brightness across the sky. The right hand pane shows the sequence of differences between each frame and a running nine-frame median, highlighting moving objects against a much flatter background.
Seventh Launch Group, Nigel Evans, 22 & 24 April 2020
The seventh launch of Starlink satellites was unexpectedly moved forward to 20:30:30 BST on 22 April 2020. This provided an excellent opportunity to witness the first pass of the carrier rocket some 20 minutes after lift-off in the evening twilight. As the satellites are released some 15 minutes after launch, they were expected not to have separated sufficiently from the rocket to be individually visible.
I imaged the passage with a 600 mm telephoto lens on a tripod with a video head. Predictions for Ipswich showed that the rocket would pass close to Venus, a bright marker in the evening sky. Having found the rocket next to Venus, it came closer and rose to higher and higher altitude making it harder and harder to keep in the field-of-view. As it passed nearly overhead at an altitude of 74°, I could no longer follow it.
It's difficult to obtain good results tracking a moving object with a long telephoto lens and, indeed, the rocket appears to dance all over the frame. So I have picked through the video, keeping all the frames where the image is reasonably still, then centred them manually, and turned them into a video. Unfortunately, the time difference between frames is not fixed!
The video shows initially two Starlink objects, a long one and a point below and to the right and, much further to the right, Venus. The point is the carrier rocket. The long streak is a stack of 60 satellites, not individually resolved, after being released by the launch rocket. As they come closer the odd stars fly by from the top of the frame. Near the satellites some stray objects start to flash into view - they are retention rods that held the satellites in place on the carrier. The stack of satellites appears to rotate, but this is an effect of perspective as they pass overhead. Then I lose them before finding them again. By now the stack of satellites and the carrier are back-lit and have become one object again due to foreshortening, but four retention rods are clearly seen as separate items.
Below the video is a composite of selected frames, showing the evolution of the Starlink train as it passed overhead.
Opportunities were initially limited to see the Starlink 6 constellation once it had been placed into orbit. However, an opportunity arose in the evening twilight of 24 April. Visually, I could not see anything, but a video showed a train of satellites low down in the SW. The video below is a 7 s clip of the original recording, cropped 50% both horizontally and vertically. The lower pane is a contrast-stretched version of the original (cropped): the satellites are still somewhat hard to see. The upper pane is a sequence of differences between individual frames and a running median of nine frames.
I then applied further processing to individual frames of the video, all 1500 of them, to produce the still images below the video. The upper still is sum of individual frames, showing a trail effect, with the satellites following one another through the sky. The lower still is a stack of 25 frames (one second's worth) aligned on the satellites. (The fact that they are moving at slightly different rates makes it not possible to achieve good results stacking a larger number of frames.) It shows 36 distinct satellites, with one or two looking like unresolved multiples. This aligns with the fact that the 60 satellites of the constellation have separated into a group of approximately 40 followed about a minute later by another of approximately 20.