Friday, 24 April 2020

Starlink Galore! [UPDATED]

click to enlarge

Last week was dominated by impressive - if worrying - displays of SpaceX Starlink satellites. Over several nights, objects from the 18 March 2020 launch (Starlink 5) made impressive passes in the sky. And on April 22, there was a new launch, Starlink 6, that could be well observed in the evening of the 22nd and 23rd, causing an impressive satellite 'train' on April 23.

In this blogpost I provide photographs, video, and descriptions.

The new launch on April 22 (Starlink 6)

On 22 April 2020 at 19:30 UT, SpaceX launched the 7th Starlink batch of 60 satellites, Starlink 6, from SLC 39A on Cape Canaveral. Some 23 minutes later, the newly launched objects made a pass over the Netherlands, in a blue twilight sky, and were well visible.

Just some seven minutes prior to this pass, and 15 minutes after launch, the payloads had been deployed from the Falcon 9 Upper Stage while the latter was over the Northern Atlantic.

With the naked eye, the Falcon 9, the just released satellites and the associated debris objects all looked like one bright object (mag 0 to -1) crossing the sky. In binoculars, they could be separated into multiple objects.

The photograph below is a stack of 12 photographs, 2.5 seconds exposed each with a Canon EOS 80D and EF 2.0/35 mm lens at F2.2, 400 ISO, showing it pass over my house in Leiden.

click to enlarge

In 10 x 50 binoculars, the view was spectacular. It consisted of a bright object (the Falcon 9 upper stage), slightly separated from another, elongated bright object (the clump of released satellites), and four fainter flashing objects surrounding them in a paralellogram shape. These were the four tumbling retaining rods that had held the satellite stack together before deployment.

Some of this is visible in this video I shot with the WATEC 902H and FD 1.8/50 mm lens. Falcon 9 and payloads still appear merged as one object here, but the retention rods are visible as separate objects:

The provisional orbit that I had calculated prior to the launch turned out to be quite good: the objects were only 28 seconds early on predictions and less than 0.5 degrees off-track at culmination.

The next night, April 23, saw a twilight pass of the satellites again, that by now had developed into a clear 'train' of objects. They were not as bright as in May 2019 with Starlink 0.1, but in 10 x 50 binoculars the moving string of 60 lights, some 10-15 degrees long, was impressive. While low in the west, in Orion, they briefly became bright and clearly visible to the naked eye for a few seconds, then they grew fainter and I turned to my binoculars to observe them.

My WATEC 902H video camera, this time equipped with a Canon EF 2.0/35 mm lens, captured the train passing in Hydra. The video gives a good impression of the view as it was visible in binoculars:

The next day, April 24, I also filmed the 'train'. This was a low pass (21 degrees maximum elevation) in twilight, at rooftop level, shot from the loft window of my home. Video withe the WATEC 902H and a 1.8/50 mm lens:

Starlink 5 passes, April 19-21

Earlier that week, we were treated on some spectacular, if eerie and worrying, displays of Starlink satellites from the previous launch, the Starlink 5 launch on 18 March.

(worrying, because of the implied impact on the night sky)

A month after launch, the objects from this launch are dispersing as they one-by-one are lifted to a higher orbit, but mid-April there was still a recognizable main group that took about 20 minutes to pass. When passing south of the zenith they are bright (but faint when passing north of the zenith, due to satellite orientation and sun-satellite-observer angles), on the first few passes even very bright (up to magnitude +0.5 for almost a full pass).

At any given moment during the pass of this group, there were 5-8 bright satellites moving in the sky at the same time, following each other in file, typically some 20 degrees apart. It was a very eerie sight reminiscent of a Science Fiction Movie: almost like the Mothership had unloaded the invasion fleet into earth orbit! The long duration, 20 minutes that satelite after satellite after satellite appeared in file, made it very impressive.

Here is a single photographic image from 19 April, showing 4 Starlink satellites traversing the sky (the fainter one that is somewhat off-set is already rasing its orbit). It is a 5 second exposure with an EF 2.0/35 mm lens on a Canon EOS 80D:

click image to enlarge

Below is a stack of 202 images from 21 April, showing 39 Starlink satellites that appeared over a 20-minute period. Note how the trails become fainter when located more north (image is looking west, so north is at the righthand side of the image). Also note the two flaring satellites:

click image to enlarge

Here are single images showing the two flaring satellites, Starlink- 1274 and Starlink-1309, flaring close to Pollux:

click image to enlarge

click image to enlarge

I used the 202 photographs, shot over a 19-minute period,  to create this time-lapse movie showing the steady stream of satellites:

This is another time-lapse video, from images from the deep-twilight pass of the previous night, 20 April:

Below are three more stacks of photographic images from April 19 and April 20 (the gaps in the trails are the brief moments between two consecutive photographs, hence the dashed appearance of the trails):

click image to enlarge
click image to enlarge
click image to enlarge

1 comment:

Shashank Shekhar said...

Hi, thanks for the detailed coverage! :) Could you please help me understand why they are dimmer when north of the zenith or overhead?

If a satellite is assumed to be a sphere, wouldn't its reflection be similar if the sun-sat-obs angle is the same (whether above or below the zenith)? And why is it dim when overhead, shouldn't it be brighter (being closer) like in lower latitudes?

I'm assuming this behaviour only applies to higher latitudes?

You're perfectly right about this, since this is what happened over UK this week, but I'm still unable to understand why.

Heavens Above also seemed to indicate bright passes where often nothing was actually visible over the UK.

Thanks a lot for any insight!