Astronomy and Sky Website of Martin Lewis

STS-133 Spacewalk Image

This page gives details of an ISS image I took in March 2011 which not only shows the Space Shuttle Discovery, but which I believe also shows astronaut Steve Bowen riding the end of the ISS’s manipulator arm during the second spacewalk of the mission. The image was featured in The Sun Online, the SPA website and the astronomy blog Skymania.

The Image

The ISS image was taken during an evening pass on the 2nd March 2011. During this pass, the Space Shuttle Discovery, participating in mission STS-133, was docked to the ISS and the second spacewalk (EVA) of the mission was in progress. 

This image together with similar ones, can be seen in the ISS and Shuttle gallery of this website.

In this pass the ISS went almost directly overhead (altitude=88°) from where I was observing (St Albans, UK) and the seeing conditions were good. Later inspection of the video showed that I had been fortunate to get a nice sequence of about 30 consecutive frames over a period of ~0.5 secs when the ISS was at approximately a 41° altitude and a distance of about 527km. The sequence enabled me to generate a good clear stacked image of the ISS, looking back at the Space Shuttle Discovery docked onto the far end of the ISS and with the Shuttle’s loading bay doors opened.

Although this site’s ISS and Shuttle gallery shows other images I have taken where the Shuttle is docked to the ISS, this particular one is unique in that I believe it also shows details of an EVA (Extra Vehicular Activity) session, more commonly known as a spacewalk, in progress. 

Observations of astronauts seen from the surface of the earth are very rare. Reasonable claims have been made by prolific ISS imager, Ralf Vanderbergh, in particular, but it is generally accepted that the image taken by legendary imager, Thierry Legault, on 28th Feb 2011, also from STS-133 and 2 days before my image, is the first undeniable photograph of an astronaut in orbit taken from the surface of the earth. It should be noted in the context of my image, that Ralf Vanderbergh also claims to have imaged the same spacewalk from the Netherlands only a couple of minutes after my image was taken. Further details on his image can be found on his website.

The evidence I present below supports my claim that the image does indeed show the astronaut Steve Bowen and the end of the ISS’s manipulator arm during the second EVA of the STS-133 mission. Thierry Legault, one of the world’s greatest ISS imagers, states on the Bad Astronomy website that;

After careful examination of Martin Lewis’s image, my opinion is that he has detected, not the astronaut (alone), but the block containing the astronaut, the joint at the end of the arm and the visible part of the final leg of the arm. His image looks sound, free of artifacts and well supported by NASA data analysis.

The Evidence

My claim of showing a spacewalk in progress is a bold one. Answering the following questions will help in teasing out the evidence;

Q1. Where precisely was EVA astronaut Steve Bowen at the time my image was taken?

Q2. Does my image show something at his location?

Q3. Would I have had an unobscured view of the astronaut from my location?

Q4. Was there any other part of the ISS or Shuttle at that same location which I might have confused with the astronaut?

Q5. Was Steve Bowen in shade or darkness at the time of my image?

Q6. From my viewpoint was a significant portion of the sunlit side of Steve Bowen on show?

Q7. Can I identify other features on the ISS or Shuttle of a similar size to an astronaut?

Q8. Have I just imaged the end of the ISS arm and not the astronaut?

Q9. If Steve Bowen was riding the ISS arm during the spacewalk, why can’t it be seen on the image when we can clearly see the Shuttle arm?

Q10. Can the position of the Sun’s reflection on the bottom of the Columbus Lab be a useful reference to help decide matters?

Fortunately, there is a huge amount of information available on the web that can be used to help answer these questions. As well as the very useful NASA site, tremendous sources of information have been the forum, NASA TV on YouTube and the full downloadable NASA videos of this EVA.

Please feel free to jump ahead to the answer to Q10 which gives the conclusion to my investigation, then go back to the answers earlier questions to see the other evidence I gathered on the way.

Q1. Where precisely was EVA astronaut Steve Bowen at the time my image was taken.

A.  My image was taken at 18h47m31secs UT. Figures 1a and 1b show that just before and just after my shot, astronaut Steve Bowen was located beyond the end of the Columbus Lab and level with the Lab’s lower half.

Figure 1a. The NASA image above was taken from astronaut Steve Bowen’s helmet mounted camera (camera #19 indicated at bottom RH corner of image) at 18h46m59secs. This was 32secs before I took my image and shows him beyond and level with the lower half of the Columbus Lab that you see on the LHS of the shot. Steve is holding a camera at this time.
Figure 1b. This second NASA image, also taken with helmet camera #19, was taken at 18h48m22secs, some 51secs after my shot, and still shows Steve in the same position.

Q2. Does my image show something at his location?

A.  Figure 2 below identifies the main parts of the ISS and Shuttle, together with where I claim the astronaut is located. I identify an object beyond the Columbus Lab and level with its lower edge as being the astronaut on the end of the ISS’s manipulator arm.

Figure 2. Annotated version of my ISS image detailing features visible, including the believed location of astronaut on the end of the ISS arm end. It may be quite difficult to recognise the individual parts of the spacecraft in my image, despite my annotations. Reference to the annotated NASA image, figure 3, should make things clearer.
Figure 3. Labelled view of ISS from Shuttle taken by departing Shuttle at end of the previous mission, STS-132.

It should be noted that although the perspectives are similar, my image is taken from a shallower angle than that in figure 3 and this gives more foreshortening of the main body. The NASA image also does not show the Shuttle attached. It also does not show the Leonardo module, which was attached in STS-133 mission or the ATV2 Johannes Kepler spacecraft which arrived just before Discovery. For a fully labelled artist’s impression of the state of the ISS during STS-133, with all the various spacecraft docked to the ISS named, see my useful guide in this page’s supplementary page. Another useful exploded diagram with other parts labelled can be found on the same page.

Q3. Would I have had an unobscured view of the astronaut from my location?

A.  In my image you are looking up at an acute angle to the underside of the main body of the ISS and looking back at the Shuttle (see ahead to figure 5). The fact my image was taken during a pass that went from due west to due east passing almost directly overhead makes the geometry quite easy. Everything is then in one plane and I can perform some useful calculations to give further insights. 

By measuring the foreshortening of the length of the main body of the ISS compared to its width, or, as another method, by measuring the apparent width of the ISS compared to its maximum width when directly overhead, one can calculate that the ISS must have been at an altitude of approx. 41° above the horizon in my image and approx. 53 secs before it passed close to the zenith (see figure 7).  

From the understanding of what exactly my viewpoint was when my image was taken, one can look at some NASA frames grabbed from the EVA2 video and understand that indeed I would have had a clear and unobscured view of the astronaut riding the ISS’s manipulator arm. The right-hand NASA frame below, figure 4b, shows the astronaut in the position I imaged him. Note, however, it is the left-hand frame, figure 4a, that gives much better clarity of the other various ISS and Shuttle parts.

Figure 4a. NASA EVA2 video frame taken a short while before my shot, showing a clear general view of the end of Columbus Lab with Steve Bowen moving towards it on the end of ISS manipulator arm. My viewpoint in St.Albans is effectively looking up from the lower left-hand side of this image.
Figure 4b NASA video frame badly affected by solar glare but taken at approx. 18h47m28secs, within a few seconds of when I took my shot. This clearly shows Steve Bowen on the ISS arm at the right-hand edge of the frame, beyond the end of the Columbus Lab. Unfortunately, in this section of the video the astronaut is bisected by the edge of the frame so only part of him can be seen. The sun is off the right-hand edge of the frame and you can trace back the rays at the edge of the frame to find its location. (See an enhanced version of this image in figure 9)

Figure 5 below gives further clarity of the geometry, showing my viewing direction on NASA artist’s impression of the Shuttle docked to the ISS during STS-133. On this figure I have marked my relative viewing direction, looking up and back at the ISS with a clear view of the site just beyond the edge of the Columbus Lab where Steve Bowen was working.

Figure 5. Artist’s impression of Shuttle docked to ISS with relative perspectives and positions shown.

Q4. Was there any other part of the ISS or Shuttle at that location which might be confused for an astronaut?

A.  I hope from the above images you can see that from my viewing direction there is no other part of the ISS or Shuttle which would be at the location that I have placed the astronaut. The only thing that could be at this location is Steve Bowen riding the ISS’s manipulator arm. 

Further evidence for this is given in figure 6 which shows that there was an ‘extra’ feature in my image that corresponds to the location of Steve Bowen and this feature was absent at other times when he was known not to be at this location.

Figure 6. Comparison of my image with image from 2 days earlier identifying ‘extra’ feature by Columbus Lab. This figure also uses a NASA image from the previous shuttle mission (part from figure 3) to help to identify other features in the vicinity of the ‘extra’ feature seen in my image (upper right here).

Q5. Was Steve Bowen in shade or darkness at the time of my image?

A.  He was in sunlight at the time my image was taken as examination of figure 1b shows sunlight on his left-hand glove. Additionally, in figures 1a & 1b the end of the Columbus Lab is also seen in sunlight and in figure 4b we clearly see light from the sun off the right-hand side of the frame. This sunlight would be illuminating Steve’s right-hand side.

This pass was from west to east, passing close to the local zenith and at the time my image was taken the sun was almost due west. This means that the sun was aligned very well with the main body of the ISS in azimuth. 

As far as solar altitude goes, the sun was 11° below my local horizon. As the ISS was tipped at 4° to me at the point in its circular orbit when I imaged it, this means that the sun was 7° below the horizontal  from the ISS. These calculated altitude and azimuth positions of the sun fit in well with the evidence in figure 4a which show the sun off the right hand edge of the frame and slightly below the Shuttle.

The geometry of the situation at the time of my image is summarised in figure 7.

Figure 7. Geometry of ISS, Sun and observer when I took my image.

Q6. From my viewpoint, was a significant portion of the sunlit side of Steve Bowen on show?

A.  A significant portion of the area of Steve Bowen that was directly illuminated by the sun was indeed on show from my viewpoint. The evidence for this is outlined below;

The visibility of a small object like an astronaut in orbit depends both on its surface brightness and its angular size. Can we understand what portion of the white space-suited Steve Bowen I would have seen that would have been directly illuminated by the sun and hence much brighter than his unlit side? To answer this we need to understand not only my viewing direction relative to the astronaut but also where the sun was located.  We also need to know his body orientation and posture at this time.

We know the sun’s direction and my viewing direction from the answer to Q5 and figure 7, but to know Steve’s orientation and posture we need to delve a little deeper.

The video frames I show in figures 1a and 1b show that Steve Bowen was pretty much face-on to the side of the docked Shuttle with his chest parallel to the main body of the ISS. A NASA pre-flight simulation showing Steve’s approximate position relative to the Columbus lab at this scheduled part of the EVA is given in figure 8 below. In this figure I have marked the direction of the sun and my viewing direction (the shadow and lighting direction in this picture is incorrect, but ignore that- it is just the geometry I am showing). With these angles the sun would have been directly on Steve’s right-hand side and a little below him. I would be viewing from Steve’s left-hand side and well below him.

Figure 8. NASA pre-flight simulation of the point in EVA2 where Steve Bowen is by the Columbus Lab. This is useful to illustrate the geometry of situation (all the angles in one plane).

If the sun had been directly behind Steve, from my viewing direction, then I would be have been very unlikely to have seen him. Then his illuminated side would have been on exactly the side facing away from me and from my direction he would have only been indirectly illuminated by sunlight bouncing off other reflective parts of the ISS or from light from the retreating day lit side of the earth. You can see that such indirect lighting is actually enough to make the white face of the Shuttle visible, even though it is completely in shadow, but this is a much larger target than an astronaut. We need to have been able to see a significant area of his spacesuit fully illuminated by the sun to stand a chance of picking out such a small target from the surface of the earth.

We know, however, that the sun was not directly behind him at the time my image was taken. The angle between myself, the ISS, and the sun was not 180° but only 128° as seen in figure 7. (At this angle if the ISS had been replaced by a white sphere then it would have looked like a moderately fat crescent). 

In order to know what portion of Steve Bowen I would have seen which was directly illuminated by the sun, we need to know the geometry but we also need to know his posture and his orientation. 

In figure 9, below, I have taken the 8 sec NASA video sequence  from which I took figure 4b and combined its 173 frames (which were almost unchanging) in the image processing package Registax 6. This has allowed me to reduce the frame noise and introduce some mild wavelet processing to bring out the details in the image, especially of Steve Bowen and the ISS arm.  (For the record the video sequence used for this commenced at 27m32secs into Pt3 of the downloadable STS-133 EVA2 NASA video).

Figure 9. Details brought out in figure 4b with image processing and features marked allowing us to see Steve Bowen’s posture and orientation.

From close study of this image and some section of the EVA2 video taken around this time, I now understand Steve’s orientation and posture at the time I took my shot. Details are given in the figures 10 and 11 below, which are composites of zoomed in portions from the figure above and frames from the EVA2 NASA videos.

In figures 10 and 11 we can again see that Steve Bowen is facing the side of the Shuttle in a position similar to that in the simulation in figure 8 and what was predicted from looking at figures 1a and 1b. He is clearly in a sitting posture, leaning back slightly. I can identify his kit bag by his left-hand knee, as well as his elbow, calves, boots and the bottom end of his life-support pack.

Figure 10. Two different shots of Steve Bowen 22secs before and 57secs after I took my shot showing his orientation and posture at this time. Steve Bowen is in a sitting position on the end of the arm and leaning back slightly

To see a clip from the EVA2 video I used to create the right-hand image above, where Steve clearly moves his outstretched arm, see the video at the bottom of the supplementary images page

Figure 11. Identification of parts of Steve Bowen from figure 9 and shown again in figure 10.

In the posture and orientation we have found for him and with the geometry shown in figure 7 and 8, the sunlight would have been lighting up the underside of his thighs, his rump and the bottom of life support pack, all of which are visible from where I was located. Given my viewing direction then, a significant portion of the area of Steve Bowen would indeed have been directly illuminated by the sun.

Q7. Can I identify other features on the ISS or Shuttle of a similar size to an astronaut?

A.  As I stated in my answer to Q6, the visibility of a small object in orbit depends critically on its surface brightness, angular size and its shape and orientation. Just because something is the same size as an astronaut is no guarantee that it will have a similar visibility. This is a difficult line of investigation to pursue with the amount of data available.

Q8. Have I just imaged the end of the ISS arm and not the astronaut?

A.  Figure 9, backed up by figure 8, shows that the end of the ISS arm is just below the astronaut and would also have been in sunlight if Steve Bowen was in sunlight. The bulk of the arm would, however, have been in the shadow of the Shuttle. 

Figure 12 below is an image from an EVA in early 2008 showing the ISS arm with an astronaut working on the end of it at the end of the Columbus Lab. This is a very useful image showing the relative sizes of each and as the working location is similar the ISS arm and knuckle orientations will be similar to the situation when I imaged the ISS. 

Knowing the geometry of the situation from the analysis above in Q6 it seems likely that the following would apply;
-Arm tip.  Only illuminated on far side so no fully illuminated part visible from my perspective
-Arm tip joint.  Underside sunlit and so visible from my perspective
-Arm knuckle pair.  This part of the arm would be visible from my viewpoint but whether or not the underside was sunlit would have depended on the exact angle it was at.  The angle at the time of my shot is unclear from figure 9, which is the best image I have of it.

Figure 12. Astronaut Stanley Love operating at end of ISS arm during STS-122 in 15th Feb. 2008 showing relative sizes of end of ISS manipulator arm, astronaut and Columbus Lab.

Stanley is fitting part of the SOLAR external payload to the upper (zenith) bracket of the Columbus Lab only a few days after the Lab was installed. This payload was still in position whilst STS-133 was in progress. It is sunlight reflected off this bracket and especially the underside of the external payload module, that I believe is the spot identified as C in figure 6. A better view of this bracket with the attached SOLAR payload can be found near the bottom of the supplementary images page.

Further analysis of the arm visibility is given below in the answer to Q10.

Q9. If Steve Bowen was riding the ISS Arm during the spacewalk, why can’t it be seen on the image when we can clearly see the Shuttle Arm?

A.  Although the Shuttle arm (SRMS) is clearly seen in my image the ISS arm (SSRMS) is not visible; the two arms are of a similar diameter and are both white, so why can’t both be seen? 

Mainly this difference in visibility is because almost the whole of the ISS arm is in the shadow of the Shuttle whilst the almost the whole of the Shuttle arm is in full sunlight. The end few metres of the ISS arm, however, projects beyond the end of Columbus Lab and should be out of the shadow and in full sunlight.   

The difference in the visibility of portions of the two different arms in full sunlight must be linked with the different angles of the two arms. The diameter and the reflectivity of both is similar but the angles are different and this will have a strong bearing on what fraction of the sunlit side I would see from my perspective. Without more data on the exact angles of the arms it is hard to fully understand why we can’t see any sign of the main part of the ISS arm. Having said this there is ample evidence to say that although it does not show on my image, the ISS arm is clearly positioned below the Columbus Lab at the time my image was taken.

Q10. Can the position of the Sun’s reflection on the bottom of the Columbus Lab be a useful reference to help decide matters?

A.  From answers to earlier questions I now know enough to calculate the position of the strip of sunlight reflecting off the metallic finish of the cylindrical body of the Columbus Lab. This information can be a very useful positional reference to support the claim that the extra feature in my image is either Steve Bowen alone or Steve Bowen and the end of the ISS arm.

In figure 13 I have drawn side-on and end-on views of the position and shape of Steve Bowen and the ISS arm relative to the end of the Columbus Lab. This drawing is based particularly on figure 9, which is a close-up view of the configuration taken at the time of my shot. The proportions of the ISS arm and astronaut in these new drawing are also based on NASA images, particularly figure 12, where the arm and astronaut are clearly shown at a similar scale to the end of the 4.5m diameter Lab. 

Figure 13. Estimated/calculated end-on and side-on views of Columbus Lab, astronaut and ISS arm end.

To help with the generation of figure 13 one can get a good understanding of the correct relative position of Steve Bowen by referring to figure 9 but also by reference to Steve’s helmet-mounted camera shot shown in figure 1a.  The viewpoint in that image allows us to see that his head was just level with the right-hand edge of the Lab and just below its mid-line. We already know his posture and orientation from an earlier question and the only bit of information we are now missing to fully define his position is his linear distance from the end of Columbus Lab.  Fortunately, one can use the information in figure 1a to calculate this. This is done by comparing the relative angular sizes of objects in the shot, knowing their real dimensions and from knowing their distances from a from end of the Lab.  For this calculation I picked the circular disc at the centre of the Lab and the white section just below the black nose cone of the Shuttle as my two reference objects.  Some research gave me both their real sizes and distances from the end of the Columbus Lab and some A-level algebra and trigonometry was then used to give a value for the distance between the end of the Columbus Lab and Steve’s camera as 2.55m.

With the side-view and end-views of Columbus, ISS arm end and astronaut established, and having a good understanding of which areas of the scene would have been directly illuminated by the Sun as seen from my viewpoint (see answers to Q6 and Q8), one can then go on to generate a very useful final drawing that gets us much closer to definitively answering our key question of what I really saw of the EVA.

This new drawing, figure 14, is graphically calculated from the side and end-view drawings and is the view of the scene drawn from the perspective of my viewpoint in the UK, at 44° to the body of the ISS.  It shows where I calculate the bright spots of light would be including the reference strip of sunlight glinting off the body of Columbus.  This is the spot of light whose location I am most certain about being the easiest to calculate.  Effectively this is a close-up drawing of the scene I imaged and makes up for the fact that no close-up photo exists taken from the direction I imaged it, at the time I imaged it.

Figure 14. Calculated view of region around end of Columbus Lab based on views in figure 13 and the known geometry of the situation.

The angled view above is reproduced again below, but this time beside a massively enlarged section of the same area taken from my ISS image. This section of my shot has been scaled-up enormously to exactly match the scale of the drawing and also rotated so the two orientations match as accurately as possible (by making the ISS truss assembly in my shot also horizontal). To maximise details in this very localised portion of my shot I actually regenerated my ISS image, this time concentrating not on overall fidelity of Shuttle and ISS, but carefully selecting frames to stack based solely on the quality of just this section of each frame.

Figure 15. Calculated view versus real view. Drawing on left shows Lab, astronaut and arm end with estimated bright areas. Image on right is enlarged section from my image scaled and rotated to match the drawing and showing where bright spots really were.

In the final figure of this investigation I have superimposed the drawing onto the enlarged section from my image. I have used the reflection of the sun, glinting off the metallic side of the Columbus Lab as a ‘known’ reference bright spot to enable me to accurately line up the two images.

Figure 16. Estimated/calculated view (drawing) overlaid onto my real (pixellated) view and lined-up with reference to where the sun’s reflection is on the side of the Columbus Lab.

This is a very pleasing image for me as it shows a good match between where the predicted bright spots should be and where the bright spots really were in my image. Remember that the perspective drawing has been carefully deduced from the supporting evidence I have gathered, not created retrospectively from my image. The matching was done as the final step and the fact that they do match is, I believe, vindication of my workings.

After carrying out this investigation, I believe that I can now confidently say that;

My image shows, as a discrete spot, the combined light of astronaut Steve Bowen and the last part of the ISS arm he was riding during the EVA. 

I cannot say, however, that I have captured the light of the astronaut alone which would have been the most satisfying outcome of this investigation.

I hope you have enjoyed reading my notes on this investigation which was carried out for my own personal satisfaction. Please do contact me at if you have questions that you think I might be able to answer relating to this page.