Tumbling Launch Debris in Orbit
When the last stage of a rocket separates from a spacecraft, forces often cause a tumbling motion about one or more axes of the rocket. Telescopic observations on this page appear to confirm a long-accepted theory that is explained here - namely that rockets that show (naked eye) a regular flashing pattern, probably rotate about their short body axis. If you observe a flashing satellite in the night sky, then there is a good chance that you actually see a tumbling rocket stage. However there are plenty of satellites that show a flashing pattern as well, for instance malfunctioning satellites that lost their stability. Additionally there are also several rocket upper stages that do not appear to tumble or do not tumble anymore and orbit the Earth in a stable attitude. Due to the harsh degree of difficulty, detailed high resolution observations of tumbling objects in orbit are very rare, even in today's digital era. The following telescopic observations are among the best I have obtained so far regarding rocket stages and other launch debris that is tumbling in Earth orbit.
I was interested in recording tumbling rocket debris since I started doing spacecraft imaging. As soon as I was able to capture telescopic images of smaller satellites I started photographing spent upper stages of Soyuz, Progress and other launches that passed favorably and often showed spectacular rotational behave around their own axes. It turned out to become an extremely interesting and especially pioneering field to practice. All observations are done with the same manual tracking technique as I use for general satellite and ISS imaging. However, the tracking can be much more challenging due to the large difference between a minimum and a maximum in the brightness curve. As the rocket tumbles around, alternately the short sides and long sides of the body are illuminated by the sun. During a minimum, the rocket can disappear out of view as it is too dim to be seen. The trick that I learned throughout the years is to manually keep the right tracking speed until you can pick up the object again. The rockets and fairings are often in very low orbits causing high angular speeds which makes the tracking even more challenging.
My first successful telescopic registration of a tumbling rocket, the upper stage from the Soyuz TMA-19 on June 17, 2010
Tumbling Solar Panel Cover - SpaceX Dragon CRS-8 Launch
On April 9, 2016, I obtained images of a tumbling solar panel cover in orbit, jettisoned after the SpaxeX Dragon CRS-8 launch on April 8. Two covers were identified as objects 2016-024B and 2016-024C and were passing with an interval of around 1 minute. Routinely 2 covers can be seen after a Dragon launch together with the capsule and the upper stage of the Falcon 9 rocket. I successfully captured the tumbling motion of object 024B as presented below. This in fact was my first successful registration of orbiting and tumbling launch debris other then separated rocket stages. Photographing smaller launch debris as solar panel covers is particularly difficult due to the small size of these launch items.
Rare captures of the tumbling motion of a Dragon solar panel cover captured with a 10 inch telescope. Right: Processed frames of the panel from the video
Soyuz Rocket Upper Stages
The rocket upper stages of the regular Progress and Soyuz launches to the International Space Station have turned out to be suitable objects to study tumbling motion as in this case the tumbling is present routinely. The upper stage of the Soyuz-U rocket will usually stay in a very low Earth orbit of less then 200 kilometers for 2 days after launch while it sinks significantly in the last orbits before it burns up in the atmosphere. The low altitude can result in relatively detailed observations of the rocket and its tumbling motion. A disadvantage of these observations in very low orbit is the very high angular speed that cause the tracking of these objects to be very challenging. Regularly there are also other interesting possibilities to observe spent rockets and their tumbling behave in orbit. In 2011, I observed a Zenit rocket second stage while it crossed the sky. Telescopic observations of this pass resulted in spectacular views of the rotational behave while it crossed the field of the camera several times.
Tumbling Egyptsat 2 Rocket
On April 16, 2014 the spy satellite Egyptsat 2 lifted up on a Soyuz-U rocket from Baikonur. On June 24, I captured images of the Soyuz third (upper) stage in orbit after I observed it visually several times. The distance at the time of imaging was 729 kilometers while its altitude was 688 kilometers above the ground. The range of over 700 kilometers is a challenging distance for an object the size of an upper stage. Nevertheless, the resulting videos of the passing Egyptsat rocket are among the clearest to show tumbling motion of the Soyuz third stage in orbit so far.
Videos of the tumbling Egyptsat 2 (Soyuz-U) rocket seen from 729 kilometers distance taken on June 24, 2014 with a 10 inch telescope
Set of unprocessed raw frames of the tumbling Egyptsat rocket showing 2 long sides and 2 short sides
Same set of frames but with an unsharp mask processing applied
Spectacular Tumbling Zenit Rocket
On July 18, 2011 the Russian radio telescope Spektr-R lifted off on a Zenit rocket from Baikonur. On August 2, 2011 there was a pass of the Zenit second stage that was released in an orbit of 177 by 447 kilometers. The Fregat upper stage brought the telescope to a final orbit of 10.651 by 338.541 kilometers. With a length of 10 meters, the Zenit second stage is a bigger and more spectacular object to observe in low Earth orbit then a Soyuz upper stage that can be observed more frequently. Already for the naked eye, the Zenit stage was flashing dramatically while it was passing in a favorable northern route across the sky. The rare opportunity ended in a telescopic imaging session with spectacular results. While tracking the rocket manually, it crossed the camera field several times and detailed observations of the tumbling motion around the rocket's axes were recorded. A closer analysis of the frames revealed a rotation period of far below 0.5 second for the 10 meter long object. This incredible observation is explained in Amazing Observation of Space Debris.
Very rare capture of a tumbling Zenit 2nd stage of the Spektr-R launch, crossing the field of my 10 inch telescope. The telescope was intentionally pointed to
the rocket, but it is very rare to capture tumbling motion in just a few frames. Every single frame shows a different stage in the tumbling motion of the rocket
Another pass of the tumbling Zenit 2 second stage Spektr-R rocket through the telescope field. We see rotation about the rocket short axis as the rocket
shows alternately its long and short sides. Note also the brightness variations between the different stages in the rotation caused by different illumination.
The Oldest Tumbling Rocket Body in Earth Orbit?
In 2010, I came across a remnant of the Aureole-2 satellite launch on December 26, 1973. The observations showed this Kosmos-3M rocket upper stage clearly tumbling. This is remarkable for an object that is almost 40 years in Earth orbit. So far I haven't obtained any new observations of this object since the 2010 session but it is very convincingly that it is still tumbling in the years following this observation. The tumbling as observed in 2010 occured at a slow rate, note that the animated gif of the video frames as shown below is significantly accelerated. Although the image resolution from this session is not particularly good due to poor seeing, small object size and altitude, the tumbling motion is clearly visible.
Aureole-2 (Kosmos-3M) rocket tumbling captured on June 29, 2010. Left: Still frames showing maximum and minimum brightness