Imaging some splendid passes of HTV-9 (Kounotori-9) and Cygnus NG-13

It are very busy times at the International Space Station. Spaceships come and go.

First, on May 11, the US cargoship Cygnus NG-13 was released from the ISS, three months after berthing to it. This cargoship had been launched on 15 February 2020 and berthed on 18 February. After its release from the ISS two weeks ago, it is currently free-flying to do experiments. It will perform a controlled reentry over the southern Pacific on 29 May.

On 20 May at 17:31 UT, the Japanese cargoship HTV-9 (Kounotori-9) was launched. It berthed to the ISS on 25 May. This provided the opportunity to see two ISS cargoships, one departing and one arriving, in the sky last week.

And it continues: we are in anticipation of the Crew Dragon Demo-2 launch, on May 27 if weather cooperates (see my previous blogpost), bringing to astronauts to the ISS.

Both Cygnus NG-13 and HTV-9 made some splendid evening passes last week. Weather was clear on most days, allowing me to observe and photograph several passes, often two on one evening. Through Twitter, I managed to get a lot of people to go out and watch the passes. HTV's are very bright and distinctly orange objects, easily visible with the naked eye even in deep twilight and from an urban environment. So they are ideal objects to get people out and watch.

HTV-9 was a spectacular sight on every pass. It reached magnitude 0 to -1, with a very distinct orange colour that is due to the orange thermal foil it is wrapped in. It was also prone to producing brief bright flares to magnitude -2 to -3. It did this on almost every pass, sometimes multiple times. here is an example, from May 21:

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Below are a number of photographic stacks I made during these HTV-9 passes (gaps in the trails are the brief periods between successive photographs in the stack). The first image showing another flare: the second bright satellite crossing the path of HTV-9 in the third image is Resurs P1. Note the orange colour, especially apparent in the second image. Visually, the orange colour was even more profound than in these images (where they have washed out a bit due to the brightness of the trail).

Click to enlarge

Click to enlarge

Click to enlarge

Cygnus NG-13 was much fainter than HTV-9. During a  good pass it would reach magntude +3, but often was below naked eye visibility. Here is imagery from one of the brighter passes, on May 19 when it reached magnitude +3:

click to enlarge

Click to enlarge

Click to enlarge

Click to enlarge