Imaging a pass of the Crew Dragon Demo-2, and a close fly-by of the Crew Dragon by USA 245! [UPDATED]

click photograph to enlarge

Yesterday May 30 at 19:22 UT finally saw the launch of the SpaceX Crew Dragon Demo-2 with astronauts Hurley and Behnken on board, returning a human spaceflight capability to the USA after nine years of having to hitch rides on a Russian Soyuz.

When the Crew Dragon first passed over the Netherlands some 23 minutes after launch (see map with the launch trajectory in  a previous post), the sun was still just above the horizon for my Leiden location. I nevertheless tried with binoculars, using the moon as a guide, but saw nothing.

But two hours after launch on the second revolution, near 21:18 UT, we did have a visible pass, albeit in late twilight and very low above the horizon: at a maximum elevation of only 9 degrees over the horizon and a range of almost 1200 km!

To observe this pass I went by bicycle to Cronesteyn Polder at the edge of Leiden, where I have an uninterupted view to the horizon, and set up my photo camera. First, at 23:14 local time (21:14 UT), I saw the ISS pass with the naked eye low on the southwest horizon. I then took to binoculars and waited for the Crew Dragon, which should pass somewhat lower in the sky some 4 minutes after the ISS.

I picked the Crew Dragon up in my 10 x 50 binoculars starting around 21:17:30 UT, while it was passing through Crater and Corvus. I watched it untill it entered Earth shadow at about 21:19:00 UT. It was not particularly bright, due to the low elevation and still bright sky background. By comparison to stars in Corvus I estimate it to have been magnitude +3 to +3.5, too faint at this elevation and with this sky brightness to be seen naked eye. It was at a range of almost 1200 km at that time, over Northern Spain!

Click photograph to enlarge

The image above shows the Crew Dragon during this pass. It is a stack of 45 exposures of 0.5 seconds each, with a Canon EOS 80D and SamYang 1.4/85 mm lens at F2.0, 500 ISO, 21:17:40 - 21:18:09 UT (May 30). Stars in the image belong to the constellations Crater and Corvus. The small breaks in the trail are the brief moments between the successive photographs that make up the stack.

The image below is another stack, this time of 52 photographs with the same camera setup, made between 21:18:25 - 21:18:59 UT. You see the Crew Dragon disappear in Earth shadow at the left end of the image. The image is slightly wobbly - my tripod was on a soft grassy surface. I like this image best though:

Click photograph to enlarge

It was pretty cool seeing the Crew Dragon, while knowing it was carrying two astronauts!

But it becomes even more interesting: in two images around 21:18:19 UT, I have another brighter satellite moving under a slant upwards in the opposite direction. You can see it in the upper right corner of this image (several lay observers saw this brighter satellite too and mistook it for the Crew Dragon):

Click photograph to enlarge

This object is the classified US KH-11 spy satellite USA 245 (2013-043A).

And as it turns out, it was really close to the Crew Dragon, and my image truely captures, within a few seconds, the actual moment of closest approach! This was serendipity, as I had not planned this and the presence of USA 245 took me by surprise.

Nominally, the minimum distance between USA 245 and the Crew Dragon during this fly-by was only 125 km with closest approach happening at 21:18:17 UT. USA 245 was flying this distance 'above' the Crew Dragon. Both objects were over northern Spain around the time of the flyby, with the point of closest approach over 43.40 N, 2.50 W, on the Basque coast.

There is some uncertainty in the actual fly-by distance (see below), but not much.

This is the output from a COLA analysis for this fly-by:

DATE      UT          SSC   NAME    TARGET      KM  
5/30/2020 21:18:16.99 39232 USA 245 CREW DRAGON 125.3

My analysis is based on CSpOC elset epoch 20151.85044152 for the Crew Dragon, and amateur elset 20146.86101776 for USA 245. There is some leeway in the exact time and distance of the flyby, for two reasons:

1)  from my observations, the Crew Dragon was some 3 seconds late on the used elset;

2)  the USA 245 elset epoch, based on amateur observations that include my own, was 5 days old. However, the sky position of USA 245 in the image is very close to the ephemeris, so the 5-day-old orbit nevertheless seems a good fit to reality.

Taking these points into account, I estimate that the uncertainty in the minimum distance between both objects is no more than 30 km, and only a few seconds in time.

In the map below, I have plotted the trajectories of both objects (I have accounted for the fact that the Crew Dragon was ~3 seconds behind on the elset in this map). USA 245 was moving nortwest-wards, the Crew Dragon southeast-wards.

Note that the USA 245 trajectory was situated some 125 km above that of the Crew Dragon. So to be clear, there was no danger of a collision. This is a safe distance.

click map to enlarge

 This is an animation of the close fly-by:




In fact, it could very well be that this close flyby was intentional, and that USA 245 was actually imaging the Crew Dragon at that moment.

USA 245 is a KH-11 electro-optical reconnaissance satellite: a satellite that resembles the Hubble Space Telescope and makes high resolution images of the earth surface (similar to this infamous one) with resolutions of 10 cm or better.

There have long been rumors, reported by amongst others NBC News, that KH-11 satellites were used to inspect the outside of Space Shuttles post-launch (e.g. that of the inaugural STS-1 flight) for tile damage. We also suspect that KH-11 satellites inspect X-37B's after launch, based on the odd jumps in launch times of the latter (see this analysis by Bob Christy).

So there is a real possibility that this close flyby of the Crew Dragon by USA 245 was intentional, and used to image the spacecraft to see if it was not damaged and everything deployed as it should.

UPDATE 1 June 2020 13:50 UT:

I am retracting the notion of intentionality of this encounter. Both Michael Thompson and I have done an extended analysis of potential KH-11 encounters with the Crew Dragon, where we looked at potential encounters had the Crew Dragon launched on the original launch date of 27 May.

There appear to have been no particularly close encounters would the Crew Dragon have launched on May 27, which calls into question the intentionality of the encounter on May 30.

That said: it is still possible that imaging of the Crew Dragon took place, as of course this would have been a perfect opportunity. I guess we'll never know. Unless, as someone put it to me in private, tongue in cheeck: "if they put it in a briefing, maybe Trump will tweet about it!". 

The analysis also found a second close encounter for May 30, with the KH-11 satellite USA 224 (2011-002A), on 30 May 20:07:50 UT, some 45 minutes (half a revolution) after launch, with a nominal miss distance of 105 km. This however was a pass where the Crew Dragon was in Earth shadow, so not illuminated (which does not preclude infra-red imaging however). COLA output for this encounter:

DATE      UT          SSC   NAME    TARGET      KM 
5/30/2020 20:07:50.30 37348 USA 224 Crew Dragon 105.4

The trajectory of the upcoming Crew Dragon Demo-2 launch, returning the US to crewed spaceflight

Photo: SpaceX

UPDATE: the Crew Dragon launch has been postponed to NET 30 May, 19:22 UT

Below is the original text and maps, which are however no longer valid!
New maps in a new, separate post.

If everything goes well, SpaceX and NASA will launch the Crew Dragon Demo-2 flight with astronauts Bob Behnken and Doug Hurley to the International Space Station on 27 May 2020. The launch is slated for 20:33:33 UT (note: some sources now say 20:33:31 UT), from LC-39A.

This is a historic flight, because after a 9-year hiatus it will return NASA to a crewed flight capacity. It is the first crewed flight launching from US soil on a US rocket since the Space Shuttle program ended in 2011. Over the past 9 years, US astronauts had to hitch a ride on Russian Soyuz spacecraft in order to get to space.

The Crew Dragon Demo-2 will fly this approximate flight trajectory, bringing it over Europe some 23 minutes after launch:

click map to enlarge

click map to enlarge

The times in the map above are in UT (GMT): for CEST add +2 hours; for BST add +1 hour. I created the maps using the (uncrewed) Crew Dragon Demo-1 test flight from March 2019 as a proxy.

Based on that same Crew Dragon Demo-1 flight, I estimate these orbital elements for the first orbit:


CREW DRAGON DEMO-2   
1 70000U 20999A   20148.85443285 -.00003603  11390-4  00000+0 0    03
2 70000  51.6423 089.9835 0122953  45.6251 315.4951 15.99554646    09 

estimated initial orbit for launch at 27 May 2020, 20:33:33 UT


You can use this so called TLE (for an explanation of these numeric lines click here) to make pass predictions and maps of the trajectory in your local sky for your own location, using prediction software like HeavenSat.

Be aware that it is approximate: so allow for a possible error of 1-2 minutes in the time it will pass in your sky, and a small cross-track error (I expect this latter to be less than 1 degree, i.e. less than two moon diameters).

Weather willing,  the Crew Dragon containing the astronauts and the Falcon 9 upper stage will be visible from much of Europe some 23 minutes after launch.

Northwest Europe has it pass in twilight, but Dragon's tend to be bright, so twilight should be no problem and the Dragon and Falcon 9 should be easily visible by the naked eye, except perhaps from the British Isles where it is still quite light.

I do advise using binoculars once you have located the spacecraft, as the Crew Dragon and the Falcon 9 upper stage will be close together, and with binoculars you will see them separately (you can see some photographs of a pass of a just launched Cargo-Dragon and its Falcon 9 upper stage from March this year in an earlier post here).

If you are lucky, you might even catch some small corrective thruster firings as small "puffs", like in this movie which I shot of a pass of the Dragon CRS-20 in March this year (look for the "puff" going upwards around 05:13:00 UT in the video):




(the two slowly varying objects astride the Dragon and Falcon 9 stage in the video above are the two ejected solar panel covers. The Crew Dragon does not have these, as far as I know).

The Falcon 9 upper stage will be deorbitted some 55 minutes after launch, over the southern Indian Ocean west of Australia.

photo: SpaceX

Below are my predicted sky tracks for a number of places in West and Central Europe, valid for launch on 27 May at 20:33:33 UT .

Times listed in the plots below are in local time (generally CEST, except for London which is BST). Please be aware that there is an uncertainty of about 1 to 2 minutes in the actual pass time!!! The track placement in the sky should generally be correct though. Bottom of the plots is either South or North, depending on the location (see the annotations on the plots).


Note added 25 May: the Heavens-Above webservice now provides you with custom predictions for the Crew Dragon for your observing site.

Amsterdam

Berlin

Brussels

London

Paris

Prague

Vienna

Hamburg

Lyon

Marseille

Munich

Reims

Strassbourg

[UPDATED & CORRECTED] Observing the SpaceX Dragon CRS-3, the ISS and two pieces of Dragon launch debris

CORRECTION (21/04/2014 12:55 UT): in the initial post, the two debris pieces were misidentified. "2014-022C" turned out to be 2014-022H, and "2014-022H" turned out to be 2014-022G.

click image to enlarge

Last Friday at 19:25 UT, SpaceX launched the Dragon CRS-3 commercial supply ship to the International Space Station ISS. It passed over Europe 20 minutes later but unfortunately I was clouded out in Leiden. In the middle and eastern parts of the Netherlands as well as elsewhere in Europe, observers were treated to a spectacular view of the Dragon, the Falcon upper stage, and two faint pieces of debris passing by as a thight group of objects.

SpaceX Dragon CRS-3
click image to enlarge

I was more lucky yesterday when the sky was clear and the Dragon and ISS made a late twilight pass culminating at approximately 26 degrees altitude in the SW near 20:06 UT (22:06 local time, sun at -12 deg.). The image above shows the Dragon CRS-3 due south already somewhat past culmination. It was easy to see with the naked eye, attaining magn. +1.5. Its brightness is more similar to a Progress or ATV then to the much fainter commercial Orbital Sciences Cygnus.

The Dragon was about 1m 12s behind the ISS, a visual distance of somewhat over 40 degrees. Pre-observation predictions based on elements a few hours old had put it in front of the ISS, so at first I was wondering whether I missed it. Then, as the ISS was descending towards the SE, I saw it approaching in the SW, chasing the ISS. A very fine sight!

The ISS passing the same sky area as the

earlier image, 1 min earlier

(click image to enlarge)

While I was photographing at the nearby city moat, I had also set up the video in my girlfriend's appartment, and this capture both objects as well: first the ISS, then a minute later the Dragon:




(the display says "GPS BAD" because my GPS time inserter failed to lock on a GPS satellite. I hope it is not broken...)

Apart from the Dragon and the ISS, I observed and photographically imaged a third debris object related to the launch. It is the object catalogued by JSpOC as 2014-022C/#39682. 2014-022H, #39687. It is either the jettisoned Dragon nose cone cover, or one of the solar panel covers   or possibly one of the Nanosat dispensers: I think it is too bright to be one of the several released nanosats itself. It was faint and slowly tumbling, alternating between invisibility and a max magnitude of about +3.5:

tumbling Dragon debris 2014-022H

(click image to enlarge)

[UPDATE:] Later I discovered a second piece of Dragon CRS-3 launch debris on my imagery. It is faint, irregular in brightness and present on two images, the best of which is this one from 20:04:07 UTC:

tumbling Dragon debris 2014-022G
(click image to enlarge)

This turns out to be the object designated 2014-022H, #39687  2014-022G, #39686. This is the other solar panel cover.

Cygnus OA-7 and Dragon CRS-11 chasing the ISS in a twilight sky

ISS and Cygnus OA-7. Click to enlarge

June 3, the launch date of SpaceX's Dragon CRS-11 cargo spacecraft to the International Space Station (ISS), was clouded out in Leiden, much to my frustration.

But yesterday evening was (sort of) clear, albeit with cirrus in the sky and a moon that was quite a nuisance. It allowed me to observe the ISS, the Dragon CRS-11, and Orbital ATK's Cygnus OA-7, which had de-coupled from the ISS a few hours earlier, making a low elevation pass (less than 35 degrees elevation) in the southern sky.

The image above shows the ISS (the bright object near the tree) and, as a faint trail, the Cygnus OA-7 (upper right corner, in the cirrus), descending towards the SE horizon.

Below is a better picture of Cygnus OA-7, shot 25 seconds later (ISS is already behind the tree here):

Cygnus OA-7. Click image to enlarge

Cygnus OA-7 passed ~25 seconds after the ISS. One minute later, ~1m 25s behind the ISS and on a slightly lower elevation track came another object: Dragon CRS-11:

Dragon CRS-11. Click image to enlarge

I did not expect the Dragon to be behind the ISS: I expected it somewhat in front of it. So initially I was miffed that I missed it (see below, this evening did not go quite well): to be surprised by it appearing behind the ISS!

This evening did initially not go well, but in a weird way eventually turned out fine.

A number of objects would pass in a short timespan of a few minutes: USA 276, the Dragon solar panel covers, Dragon, ISS, and somewhere nearby the ISS also Cygnus OA-7.

There were no post-ISS-release elements for the Cygnus yet, so its position would be a guess, although I reckoned it probably still was close to the ISS. Cygnus are usually faint (this time too) and only naked eye objects under favourable circumstances (usually, as this time, close to shadow ingress).

For Dragon, only a day old elements were available. These placed Dragon a few minutes in front of the ISS. As it no doubt would have manoeuvered during that day, I expected it to be closer to the ISS in reality, but that it was behind the ISS, that was a bit unanticipated.

The passes occurred in twilight (sun about 10 deg below the horizon). As obtaining new astrometric data on USA 276 (see story here for as to why) was important, I had set up the WATEC video camera to capture it, from the loft window (the only spot in my house where I can view that low south). That took  me longer than expected, as I initially had some trouble finding the target area in the video view (it was still deep twilight).

When I finally had found the target starfield through which USA 276 should pass, I discovered to my dismay that the pass was already imminent within minutes. As I could not visually observe through the same loft window, nor photograph, I had to be outside for that, at the city moat near my house which offers a view low south. So I grabbed my photo gear and ran outside. Arrived at the observing spot, I found that I already missed the opportunity to visually see and photograph USA 276 (luckily, the video camera in the loft window did film it). I also feared I had missed Dragon CRS-11, as I already could see the ISS approaching in the southwest. So I said a few strong words...

As ISS had passed the moon (which was a bloody nuisance, smack in the middle of the trajectory line) and was descending into the trees low in the south-southeast, I spotted a second, not too bright object chasing it (see first two images above). As I was photographing it and it descended into the trees, I re-aimed my camera hoping to catch it in a gap on the other (left) side of the tree.

Then I saw yet another object descend into the right side of the tree, and realised this was either Dragon or Cygnus. I initially thought, to my dismay, that it would be just outside my camera FOV. Luckily, back home later it turned out it still was in the FOV (I used a 35 mm lens).

The first, faint object on the same trajectory as the ISS some 25 seconds behind it I for this moment identify as Cygnus OA-7. The second, brighter one, on a trajectory just south of that of the ISS some 1m 25s behind it, I for the moment identify as the Dragon CRS-11.

Dragon CRS-20, 23 minutes after launch, with thruster firings

click image to enlarge

SpaceX launched the Dragon CRS-20 cargoship to the ISS this morning at 4:50:31 UT. Some 23 minutes after launch from SLC-40 at Cape Canaveral in Florida, it was visible from the Netherlands around 6:13 local time (5:13 UT) in morning twilight. There were some fields of clouds in the sky, but I nevertheless got a clear view of the four objects associated to the launch, all still closely together.

The image above is a 2-second exposure at 800 ISO which I took during the pass, using a Canon EOS 80D DSLR and a SamYang 1.4/85 mm lens. The image shows the trails of  four objects, two of which are tumbling. In the annotated image below, I identify what is what:

click image to enlarge

The Dragon cargoship, the Falcon 9 upper stage and the two solar panel covers were easy naked eye objects. The Dragon and Falcon 9 upper stage were very bright and steady, while the two solar panel covers slowly flashed alongside them. These solar panel covers varied in brightness between invisible (with the naked eye) and magnitude +1.5. The Falcon 9 upper stage and Dragon were about +1.5 to +2: with the naked eye, being very close together they seemed one object, while on the photographs they are clearly two.

The image below, taken a few seconds after the previous image, shows one of the tumbling, slowly flaring solar panel covers at its brightest, rivalling the Dragon and Falcon 9 upper stage in brightness:

click to enlarge

The slow regular flashing behaviour was nice to see: the two tumbling solar panel covers were alternating, when one of the two was bright, the other was faint (clearly visible in the image above and the video below). Due to the alternatingly flashing panel covers above and below the Dragon, it looked a bit like an aircaft.

I also captured a small part of the pass on video, using the WATEC 902H with a 1.8/50 mm lens on a fixed tripod in autonomous mode (I was outside myself witha sceond tripod and the photo camera). In this video segment (below), a thruster firing is visible as a cloudy upwards moving "puff"starting at 5:13:00 UT:



Dragon CRS-20 will berth to the ISS on Monday 9 March near 11:00 UT.

This was the last flight of a Dragon 1, and the concluding flight of a contract awarded in 2008. All future Dragon supply flights will be done by an updated model, the Dragon 2 as well as the crew-rated Crew Dragon variant of the latter.

The Mating Call of the CUCU [updated]

The ISS is seeing busy times. On July 20, Soyuz MS-13 was launched from Baikonur bringing a new crew to the ISS. Then, on July 25, SpaceX launched the Dragon CRS-18 cargoship to the ISS from Cape Canaveral, docking today (July 27). And it will get even busier: in a few days, currently slated for July 31,  a Progress cargoship will be launched from Baikonur towards the ISS as well.

Soyuz MS-13

As is usual these days, the Soyuz MS-13 launch from Baikonur on 20 July 2019 was a fast-track mission, launching at 16:28:21 UT (20 July) and docking at 22:48 UT, a mere 6 hours 20 minutes later.

One orbit before docking, near 21:05 UT, the Soyus-ISS pair was visible chasing each other in a still bright twilight sky over Leiden, the Netherlands, the two objects being some 20 degrees apart. In the image below, the leading bright streak is the ISS, the fainter trailing streak near the clouds is the Soyuz (enlarge the image to see it). Visually, the Soyuz was about magnitude +1 and easy to see:

click to enlarge

During the next pass, near 22:40 UT , they already were too close to visually separate, but I could hear the kosmonauts onboard the Soyuz talk (in Russian) at 121.75 MHz FM during this pass, only minutes before docking to the ISS at 22:48 UT. Here is a recording of the best part received:

 

The Mating Call of the CUCU

Only 5 days after Soyuz MS-13, on 25 July 2019, the SpaceX Dragon CRS-18 launched from SLC-40 at Cape Canaveral. The timing of the launch, 22:01:56 UT, was unfavourable for initial sightings from the European mainland (Ireland and western UK did have sighting opportunities) as it already was in earth shadow while passing over mainland Europe 20 minutes after launch.

The next night did see visible passes, that unfortunately for me in Leiden were clouded out. I did however detect related telemetry signals at 400.5 MHz during two passes (19:22 UT, in daylight; and again during the clouded out 20:59 UT pass).

The three peaks in the frequency diagram and broad yellow bands in the spectrogram below (from the 19:22 UT pass) are the CUCU signal. CUCU stands for the "COTS UHF Communication Unit":

CUCU signal on 400.5 MHz

CUCU is a duplex telemetry broadcast that allows the ISS to communicate with the Dragon and vice versa, homing it in for berthing. It is what you could call the 'mating call' of the pair. CUCU was not active right after launch during the first Dragon revolution (I listened), but was notably active the next day, as Dragon CRS-18 was slowly approaching and climbing towards the ISS.

The CUCU signal sounds like a humming noise and a regular sharp "Beep! Beep! Beep!". Below is an audio recording of the CUCU signal, from the 19:22 UT pass, roughly corresponding to the spectrum shown above:






Initially I thought this was the CUCU of DRAGON CRS-18 itself, but looking at the Doppler curve of the signal, it was actually the CUCU signal of the ISS calling out to the fledgling Dragon (HT to Cees Bassa for noting it corresponded to the ISS rather than DRAGON).

The spectrogram below shows the signal as received during the second pass, near 20:59 UT, with the characteristic Doppler S-curve. The diagram below it shows how this Doppler curve matches with the Doppler curve for the ISS at that time:

click to enlarge

click diagram to enlarge

This was the first time I have heard the CUCU mating call, and I was surprised by how strong the signal was. The reception was made with a homebrew 120-deg V-dipole antenna with ground plane reflector, optimized for 400 MHz, and an SDR dongle.


UPDATE 28 July 2019

Dragon CRS-18 docked to the ISS earlier today, near 14:00 UT. During the 18:33 UT and 20:09 UT passes (I did not monitor the third pass at 21:46 UT), there was again radio activity around 400.5 MHz connected to the ISS/Dragon. It was different in character than when the Dragon was still free-flying. Compare the spectrogram below, from the 20:09 UT pass, with thatfrom the previous day  above (note: the fuzzy band in this case is interference - the ISS/Dragon signals are the s-shaped lines):

click to enlarge

SpaceX Dragon CRS-6 and debris pieces, twenty minutes after launch

On 14 April 2015 at 20:10 UTC, one day late due to an aborted launch the day before, SpaceX launched a Falcon 9 rocket with the Dragon CRS-6 resupply mission to the ISS.

(click images to enlarge)

Falcon 9, Dragon CRS-6 and 2 debris pieces, 20 minutes after launch

I watched the live webcast of the launch, and then 20 minutes later I watched the Dragon craft make a pass through Orion low in the West, before entering Earth shadow.

With a pass so low in the west in the evening, I expected it to be faint, but it actually was easily visible by the naked eye reaching mag. +1.5 (about as bright as the brightest stars in Orion, barely fainter than Betelgeuse which it passed close by [edit: but see below...]). It was some 30-45 seconds late on Jon Mikel's estimated initial orbit.

My images show up to three additional, fainter objects (I did not see them visually) close to the Dragon (see image above which shows them al three). These are the two jettisoned solar panel covers, and either the jettisoned nose-cone or the Falcon 9 upper stage (probably the latter). Unlike the Dragon, which is steady, these three objects are irregular in brightness, as they are tumbling.

[edit 15 Apr 10:15 UT:  according to Cees Bassa the bright object is actually the Falcon 9 upper stage, the fainter object just above and very close to it the Dragon CRS-6, while the two flaring faint objects upper and bottom are the solar panel covers]

The image below is a stack (combination) of five images taken slightly earlier, showing the Dragon Falcon stage and the flashing (tumbling) debris pieces crossing the top of Orion (Betelgeuse is top left):

stack of five 2.5 second images separated by 10 seconds

Two other single shots from that sequence, showing  the debris pieces flashing up alongside the Dragon Falcon:

Dragon and ISS will berth on April 16 and I hope to have some opportunity to observe them close together.

(many thanks to Jon Mikel for his orbital estimate)

New attempt to launch the Crew Dragon on May 30: trajectory

screenshot from the May 27 live webcast

In an earlier post I discussed the SpaceX Crew Dragon Demo-2 launch. Originally slated for 27 May, it was postponed (with the astronauts already seated on board) because of bad weather: Tropical Storm Bertha more north on the US coast was the main culprit.

The new launch attempt will be on May 30 at about 19:22:45 UT (the subminute time comes from Spaceflight Now, not from an official SpaceX or NASA source, so is apocryphal). If that launch is scrapped to, the third backup date is May 31 near 18:59 UT.

As things currently (29 May 21:00 UT) stand, weather prospects are not that good for both these dates either, with currently a 50% chance of a weather violation on the 30th and 40% on the 31st: so perhaps we will see a scrub again.

Click map to enlarge

But in case the launch does happen on 30 May, the map above is the trajectory the Crew Dragon will fly on its first revolution (times on the map are in UT).

Some 23 minutes after launch, the Crew Dragon will pass over Europe, along this trajectory (times are inUT: add one hour to get BST and 2 hours to get CEST):

Click map to enlarge

Note the location of the day/night terminator...only eastern and southeastern Europe has sufficiently dark skies at that moment.

The launch time has shifted considerably forward compared to the May 27 original launch date, by about 1h 10m. As a result, the pass is no longer favourable for NW Europa, as the pass will be before sunset for the UK, and around sunset for coastal Europe.

Only longitudes east of say longitude 13 deg E will have a sufficiently dark sky to see it on the first revolution, so eastern and southeast Europe will have a prime seat this time.

Coastal western Europe and the UK might have, depending on your locality, a theoretical chance to see the second pass 1.5 hours later, near 21:18 UT. For most localities, that will however be a very low elevation pass though, often at a maximum elevation of les sthan 10 degrees.

At the end of this blogpost, I will provide some sky charts for several European localities for both those localities with a chance to see something of the first pass, and those who might theoretically catch the second pass.

The reason that the launch time is 1h 10m earlier on May 30 than on May 27, is that the launch time is instantanious as it is determined by the moment that the orbital plane of the ISS passes over the launch site. This time shifts back by 23m 22s each day, as is clear from this tabel in which I calculated orbital plane crossings over LC-39A (and is visualized in the illustrations below it):

ISS plane crossing over LC-39A:
-------------------------------
Date           UT   
27 May         20:36:52
28 May         20:13:30
29 May         19:50:09
30 May         19:26:47
31 May         19:03:26
-------------------------------

You can also see in the table that the actual launch time is a few minutes before the plane crossing. This has two main reasons.

One is that what is actually of relevance is the position of the orbital plane once the rocket reaches orbital height (a few minutes after launch).

The other is that the Crew Dragon initially is inserted into a ~200 km altitude orbit, which is only half the orbital altitude of the ISS. As a result, the Precession rate of the RAAN is faster than that of the ISS: so launch has to be somewhat earlier or otherwise, over the 19 hour flight, its RAAN would overshoot rather than match that of the ISS upon arrrival at the orbital altitude of the ISS.

The reason May 28 and May 29 were not chosen as backup dates, is because of a second consideration: the ISS has to be within a certain distance window to the launch site in order for the two (Crew Dragon and ISS) to meet up after 19 hours of flight. As it happens, and I am not sure that is deliberate or just a happy coincidence, this also means that on the chosen dates, docking will happen on the night-time side of the Earth (with launch on May 28 or 29 it would have happened on the daytime-side).

Below are a number of sky maps for localities that have a dark enough sky (generally: sun no less than 5 degrees below the horizon) to see the first pass, some 25 minutes (for eastern Europe) after launch near 21:46 CEST. Note that there is a time uncertainty of about 1 minute or so.

TLE's are provided below the maps.

NOTE: if you are not near one of these localities, then Heavens-Above provides you with predictions for your custom location. Please note however that Heavens-Above predictions for the second revolution (the 23:19 CEST pass over Europe) seem to be based on the TLE for the first revolution, resulting in a time difference of about 1 minute with my predictions below.(but also realise there is an uncertainty of 1-2 minutes in the estuimated orbit anyway).

Maps for locations in NW Europe might theoretically be able to see the Crew Dragon on its second revolution, near 23:18 CEST (22:18 BST), some 2 hours after launch. But in most cases this will be very low above the horizon. Please note that the time uncertainty is 1-2 minutes at least!

Here is an estimated TLE for the first revolution:

CREW DRAGON                                      initial orbit
1 70000U 20999A   20151.80474535 -.00003603  11390-4  00000+0 0    04
2 70000  51.6423 075.0039 0122953  45.6251 315.4951 15.99554646    01


And here is an estimated TLE for the second revolution:

CREW DRAGON                                      second revolution
1 70001U 20999A   20151.93029831 -.18507952  12289+0 -23808-1 0    05
2 70001  51.6233 074.5097 0096856  46.3995 314.2887 15.95177824    03