Spacecraft visiting the ISS


A place of orbital habitation like the International Space Station can not operate without regular traffic to and from the station. We can observe two types of spacecraft in the immidiate vicinity of the ISS, manned ships like the Russian Soyuz or American Crew Dragon and unmanned cargo ships. There are several types of cargo craft in rotation so these offer the best chances for observation. In most cases cargocraft are in docked position when we observe the ISS, in some rare opportunities we can see cargo vehicle and space station separated. Docked Soyuz or Progress capsules are sometimes well visible in high resolution images, depending on conditions like the location of the docked spacecraft, obstructions by other elements of the station, the observing angle, the illumination angle and of course the image quality. In good seeing it is possible to see a Progress or Soyuz vehicle without too much trouble when it is docked at the aft end of the Zvezda module. In contrast, when a capsule is docked at an Earth facing port, it is harder to recognize as we look at the short axis, and when it is docked at a zenith-(upward facing) port of the station, it is only visible from a certain (mostly lower) observing angle.

                                                                      The ATV-3 Edoardo Amaldi and solar panels, photographed on March 28, 2012


When a cargo ship is on its way to a space station it can be observed as a (much) fainter object in the same trajectory in the sky. Its brightness depends a lot on the type of spacecraft and the illumination. The retired European Automated Transfer Vehicle (ATV), as shown in the photo above, was in most cases a reasonable bright object while on the other hand a Progress can be pretty dim and a Cygnus can even be dimmer. Photography of these cargo craft in solo flight can be realized with the same imaging technique as generally used for smaller artificial satellites in low Earth orbit. Sometimes there is a chance to observe a cargo ship or a Soyuz shorty after launch and in the hours after the launch the spacecraft can often be seen in a lower orbit then that of its destination. This offers chances to acquire more detailed views although the higher angular speed of the lower orbit introduces other difficulties. In rare occasions it is possible to capture manned or unmanned traffic in one image with the space station while the two spacecraft are still separated. (see chapter HTV).


Progress Cargocraft  Progress M-06M

The Progress is the classic ISS cargocraft operated by Roscosmos in Russia. This is the unmanned version of the Soyuz spacecraft and looks basically the same. For ground-based imagery it can be interesting to note that the neck between the fuel compartment and the pressurized forward module is a bit thinner on the Soyuz then on the Progress. This would theoretically increase the chance to resolve the different modules on the Soyuz. Progress cargocraft are in flight since January 1978 when it made its maiden flight to the Salyut 6 space station. I was able to photograph different Progress ships, on their way to the ISS, during re-docking actions, or after undocking. On September 3, 2010, I took images of the Progress M-06M. In March 2019, I processed frames of this imaging session that remained untouched until then. The result below is in fact one of my best spacecraft images so far. The resolution achieved, is clearly beyond the resolution that is generally expected from a manually tracked 10 inch telescope.

  Left: The Progress M-06M cargo craft photographed on September 3, 2010 and processed in 2019. Right: Model for comparison. The spherical section on top contains the actual cargo

                                        Ground-based 10 inch Telescope                                                                          Model                                                                                                                               

SpaceX Manned Dragon - Crew Dragon

I obtained first images of the manned (crew) Dragon spacecraft in July 2020 on the Demo-2 mission. The Crew Dragon is generally docked at the Harmony forward docking port and therefore -thanks to this docking position - can be observed relatively easy with a telescope from the ground. The spacecraft manifests generally as a bright white object attached to the ISS. In favorable conditions, it is possible to resolve the conical shape of the capsule and the trunk as well and sometimes even smaller more exotic details. Resolving the aerodynamic fins attached to the trunk of the Crew Dragon is a challenge as they are at the limit of detail that can be resolved from the ground, but in favorable conditions it is not impossible.

              Below: Two cropped images of the docked Crew-1 Dragon, taken November 28, 2020. Note that the capsule and the trunk of the spacecraft can be seen separately

SpaceX Unmanned Dragon

The Dragon cargocraft from the private company SpaceX has become in recent years a grateful object to observe. I succeeded in resolving the shape of the capsule and some unidentified contrast structures several times. Due to a lack of spectacular detail in the unmanned Dragon, it's difficult to obtain really interesting detail such as is the case with the Dragon's rocket upper stage were it is possible to capture the rocket engine. (see page Rocket Stages and Rocket Engines). Due to the Earth-faced docking-location at the ISS, the Dragon is also no easy object to photograph when it is docked. So far I did not succeed to photograph the solar panels of the Dragon spacecraft but these often form a special difficulty due to an unfavorable observing/illumination angle. However, most solar panels are relatively easy to photograph if the angle and the illumination is favorable.

                                          The Dragon CRS-8 capsule photographed on April 9, 2016 from a range of 362 kilometers. Note the visible flattening on top.

                                                                             On April 18, 2014, the SpaceX Dragon CRS-3 cargo craft launched to the ISS.
                                                                                The capsule's shape with some structure is photographed here in the first
                                                                                          orbit passing over Europe (Netherlands) directly after launch.

Automated Transfer Vehicle (ATV)

The Automated Transfer Vehicle was an ISS cargo craft developed by the European Space Agency (ESA). Five successful missions supplied the ISS from 2008 to 2015. The ATV was an easy observable spacecraft thanks to its relatively large dimensions of 10,3 by 4,5 meters. In high resolution telescopic images it resolved relatively easily and it looked as an elongated object with specific structure. The 4 thin solar panels of the ATV were sometimes visible and sometimes completely absent in the images. The observing angle and illumination should be good to capture the 1 meter thin solar panels. During the operational period, I observed the ATV regularly when it was orbiting solo before or after docking. Several times I photographed also the vehicle when it was docked to the ISS thanks to its favorable location on the Zvezda Module.
Shown below are only some of the very best results of my ATV imaging sessions throughout the years. Results I obtained were also regularly published in the ESA ATV-blog.

                                        The ATV-5 with its thin solar panels videographed on August 5, 2014. Left: animation of 6 raw frames, right: stack of 6 frames.

                                                                          Unprocessed raw video                                   Frame stack


                            Below: The ATV-3 with solar panels captured on March 28, 2012 from a range of 402 kilometers. Left: part of the (raw) video, mid: image processing

                                               Processed telescopic image                                     Raw video                               Space based image



                                           When imaging cargo spacecraft or satellites in general, it is no guarantee that the solar panels will be visible at all.
                                           During many ATV-passes, apparently only the body was illuminated as in these images of the ATV-4 Albert Einstein
                                                     taken on June 8, 2013. Though, the elongated ATV body itself shows some segment structure

                                                                                 Animated gif made of 3 frames of the ATV-1 (Jules Verne) after undocking
                                                                               Compare the visible structure on the capsule with the images of ATV-4 above
                                                                                  The image was taken on September 27, 2008, 2 days before its reentry
                                         The ATV-1 Jules Verne docked at its location on the ISS Zvezda Module at the end of the station, photographed on July 30, 2008

H-II Transfer Vehicle (HTV)

The HTV Transfer Vehicle or Counotori is the cargo spacecraft developed and operated by the Japan Aerospace Exploration Agency (JAXA). Its size is comparable to that of the ATV and therefore it can reach a comparable brightness in the sky. A for astrophotographers important difference with the European ATV is that it has no deployed solar panels but the solar panels are wrapped around the cylinder. I was in the position to photograph the first  HTV (demonstration flight) that was launched in September 2009 in orbit before it was filmed by the camera's on board the ISS. The images were published by JAXA on their website in that time. HTV-flights are sheduled until 2020. For a docking to the ISS, a HTV spacecraft is grappled by the robotic arm Canadarm-2 and then berthed to the Harmony module. Although this docking place is on the Earth-facing side of the ISS, it is not very easy to photograph a docked HTV clearly because, seen from the ground, it is located in front of the other structures of the space station. A solo flying HTV can often produce bright flares during the pass. I managed to record 2 of these flares at telescopic resolution so far. A flare off the HTV-4 in 2013 but this was in poor seeing, and one off the HTV-9 in 2020 in good seeing which made it possible to see which part of the vehicle produces the flare.

 The HTV-9 and a flare (see movie) recorded on May 23, 2020. The approximate illumination angle could be estimated using the comparing image taken from the ISS-camera. 

                                                                      The HTV spacecraft with different sections (JAXA)


                                         Images below: The HTV-1 demonstration flight photographed on September 13, 2009 shortly after launch from a distance of 285 km
                                               Marked in the image are proposed sections of the HTV that could be made out in the image. Compare with the above graphic.

                                                    Telescopic color capture of a huge flare on the HTV-4 taken on August 8, 2013 in poor seeing conditions.
                                                               Although the shape of the module is barely visible due to the poor seeing, the color is striking

                               The HTV-1 cargocraft (the smaller object on top, left), captured shortly before docking in one video image together with the ISS on September 17, 2009