Observing the Boeing CST-100 Starliner OFT-2 and the ISS just hours before docking.

 

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The image above shows the International Space Station ISS (the brightest trail) beying chased by the Boeing CST-100 Starliner OFT-2 (the fainter trail), in evening twilight of May 20, some 4 hours before docking of the two objects.

The image was taken with a Canon EOS 80D fitted with a Samyang 1.4/35 mm lens set at F2.0, and is a 1-second exposure at ISO 200, taken in deep evening twilight (sun at -8 degrees below the horizon). The Coma Berenices star cluster is visible at lower left. The very faint satellite just left of the image center is the European weather satellite METOP-C (2018-087A).

The Boeing CST-100 Starliner is the much plagued crew-rated vehicle that is the second US post-Shuttle spaceraft capable of transferring crew to and from the ISS.  

Orbital Flight Test 2 (OFT-2) was launched on 19 May 2022 from Cape Canaveral in Florida with an Atlas V rocket. It docked to the ISS on 21 May 2022 at 00:28 UT. It is the first successful flight test of the vehicle, following the drama of OFT-1 in December 2019 and several postponements of the OFT-2 flight following reviews into the cause of the failures in 2019. It was uncrewed during this test flight.

I observed two visible passes last night, one in deep evening twilight around 20:36 UT (22:36 CEST), some 4 hours before docking, and a second near 22:12 UT (00:12 CEST), some 2 hours before docking. The imagery with this blog post is from the first, twilight pass.

During the first pass the two objects were both visible with the naked eye (even in strong twilight): the ISS of course being very bright, and the Starliner as a fainter object of magnitude +2 to +1 just behind it. The two objects chasing each other made for a very fine sight!

Below is a video I shot with a Canon EOS 80D and Samyang 1.4/35 mm set at F2.0, during the 20:36 UT pass, showing the pair descending to the eastern horizon, with the Starliner just behind ISS (watch it full-screen, it is a HD video):

 

At about 00:12 in the video, another fast moving object, briefly flaring brightly, is visible in the lower right corner, above the chimney. This is a left-over piece of hardware (the "trunk", 2021-103B) from the Crew Dragon Endurance mission. It was making its last few revolutions around earth, reentering later that night at 3:48 UT over the NE Pacific.

Below is a 140-frame stack of the relevant part of the video. Note how the trail of the Crew Dragon debris (trunk) at right is clearly longer than that of ISS and Starliner, due to it being in a much lower orbit (~150 km, versus ~420 km for ISS and Starliner) and hence moving faster over the sky. It briefly flared brightly, as can be seen:

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Below is another image of the Starliner - ISS duo, this time a 1/4th second exposure separating them a bit better:

 

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During the second pass at 22:12 UT, the Starliner and ISS were even closer. They were no longer separable as distinct objects by the naked eye or in my camera imagery: but they were two distinct objects in 10 x 50 binoculars, very close together, the Starliner this time just in front of the ISS. Their real separation distance at that time was in the order of 100 meters. It was a spectacular view!

The Boeing CST-100 Starliner will undock from the ISS and return to earth for a parachute landing on May 25.