On September 30, 2016, after a two-year mission, Rosetta crashed into the surface of comet Tchouri. After a year, ESA published one last photo taken before the final loss of contact.
Even without excitement, earthlings discovered a few dozen minutes after its broadcast, the last images of the European Space Agency spacecraft, which were taken at 23.3-26.2 meters from the sea. The location was named Sais.
Then it was over. The damaged Rosetta fell asleep behind a comet, not so far from the Philae probe that left Earth with it twelve and a half years earlier.
How was the last Rosetta photo reconstructed?
After a year of the events, ESA publishes the photo taken by the space probe.
Even if it's a bit confusing, you can discern different elements of the terrain.
The resolution is 2 mm per pixel and the photo covers about one meter, so Rosetta was then about 19.5 meters from the ground.
Why didn't we see that before?
The truth is that this image is a reconstruction that the Osiris camera team made from the last telemetry packages transmitted by Rosetta.
"Later, we found some telemetry packages on our server and thought, 'wow, that might give another picture,'" comments Holger Sierks, head of the instrument.
After three packets (it took six to make a picture), the transmissions stopped.
It is then from the 12,228 bytes received that the team worked to model the image, making it recognizable, as opposed to automated software processing.
And that, therefore, is for the greatest pleasure of our eyes .
Why can't we see stars in photos of astronauts on space or moon walks?
Photo: Bob Behnken
The stars are not visible because they are very faint. Astronauts in their white spacesuits look quite bright, so they must use short shutter speeds and large f/stops so as not to overexpose the photos. With these camera settings, however, the stars do not appear.
The same thing happens if you try to take a picture of someone under a dark, starry sky. To get the person perfectly exposed, you should use a flash or some other light source and set your camera accordingly.
When you do that, there is no way to see the stars in the background. To see the stars, you need long exposures and wide open apertures. But with those settings, the subject of the image would look dark and blurry.
Astronauts have taken many photos of the stars in orbit, and many of them are available on NASA's website, but, unfortunately, not with space-walking astronauts in the foreground. Just like the Rosetta probe.