Post by Andrei Tchentchik on Jul 8, 2019 17:34:01 GMT 2
(.#239).- First shot of Rosetta's comrade.
First shot of Rosetta's comrade.
By Tristan Vey - Published 04/03/2015 at 18:08
The shadow of the probe Rosetta measures 50 meters long and 20 wide on the surface of the comet Churyumov-Guerassimenko.
In mid-February, the European spacecraft flew over just six kilometers above sea level, taking a cliché where we can see its shadow on the surface.
On February 14, 2015, the European probe Rosetta approached only 6 km from the surface of the comet Tchourioumov-Guerassimenko. A little more than two weeks later, as the spacecraft returned as expected at a more reasonable altitude of about 90 km, scientists broadcast a first image captured by the Osiris camera during this dangerous razor.
Each pixel of this shot represents 11cm of the surface. This is almost twice as good as the photographs taken in October when the spacecraft was in close orbit at 10 km (the previous "record"). It was then necessary to map the surface of the comet 4km in diameter with the greatest precision possible in anticipation of the release on the surface of the little robot Philae a month later.
This time, the researchers wanted, among other things, to take finer details of the surface and to measure the albedo, ie the amount of reflected light, with precision. For this, they placed Rosetta exactly between the Sun and the comet.
We can see the shadow of the probe on the surface and a halo of more intense light around this spot (which measures 20 meters by 50). This shadow is not very clear: we do not clearly distinguish the shape of Rosetta. On Earth too, the shadow of an airplane at several kilometers of altitude forms a diffuse spot. This phenomenon is related to the distance of the object from the surface on which the shadow is projected and the size of the light source, as summarized in this infographic published by the European Space Agency:
Credits: ESA / ATG medialab (probe) ESA / Rosetta / NAVCAM (comet).
The luminous halo around the shadow comes from a phenomenon called "opposition effect". In the eyes of an observer with the Sun in the back, the shadows formed by the asperities of the ground are hidden by the asperities themselves. On the contrary, the further one gets away from the main shadow, the more these tiny shadows become visible, making the image darker.
In addition to shooting, scientists are also expecting a lot of data from this overview. Rosetta had to fly over very active areas to recover grains of matter ejected a short time ago. Measurements of the magnetic field as a function of altitude were also in the program.
If the results of these measurements are not yet known, the scientists considered them to be crucial enough to take the risk of such an over-flight. At this distance, the slightest hazard, an unexpected jet of gas or technical damage, could have had dramatic consequences. The probe could as well have crashed as lose sight of the comet. In both cases, the mission would have been completed. This is fortunately not the case.
F I N .
First shot of Rosetta's comrade.
By Tristan Vey - Published 04/03/2015 at 18:08
The shadow of the probe Rosetta measures 50 meters long and 20 wide on the surface of the comet Churyumov-Guerassimenko.
In mid-February, the European spacecraft flew over just six kilometers above sea level, taking a cliché where we can see its shadow on the surface.
On February 14, 2015, the European probe Rosetta approached only 6 km from the surface of the comet Tchourioumov-Guerassimenko. A little more than two weeks later, as the spacecraft returned as expected at a more reasonable altitude of about 90 km, scientists broadcast a first image captured by the Osiris camera during this dangerous razor.
Each pixel of this shot represents 11cm of the surface. This is almost twice as good as the photographs taken in October when the spacecraft was in close orbit at 10 km (the previous "record"). It was then necessary to map the surface of the comet 4km in diameter with the greatest precision possible in anticipation of the release on the surface of the little robot Philae a month later.
This time, the researchers wanted, among other things, to take finer details of the surface and to measure the albedo, ie the amount of reflected light, with precision. For this, they placed Rosetta exactly between the Sun and the comet.
We can see the shadow of the probe on the surface and a halo of more intense light around this spot (which measures 20 meters by 50). This shadow is not very clear: we do not clearly distinguish the shape of Rosetta. On Earth too, the shadow of an airplane at several kilometers of altitude forms a diffuse spot. This phenomenon is related to the distance of the object from the surface on which the shadow is projected and the size of the light source, as summarized in this infographic published by the European Space Agency:
Credits: ESA / ATG medialab (probe) ESA / Rosetta / NAVCAM (comet).
The luminous halo around the shadow comes from a phenomenon called "opposition effect". In the eyes of an observer with the Sun in the back, the shadows formed by the asperities of the ground are hidden by the asperities themselves. On the contrary, the further one gets away from the main shadow, the more these tiny shadows become visible, making the image darker.
In addition to shooting, scientists are also expecting a lot of data from this overview. Rosetta had to fly over very active areas to recover grains of matter ejected a short time ago. Measurements of the magnetic field as a function of altitude were also in the program.
If the results of these measurements are not yet known, the scientists considered them to be crucial enough to take the risk of such an over-flight. At this distance, the slightest hazard, an unexpected jet of gas or technical damage, could have had dramatic consequences. The probe could as well have crashed as lose sight of the comet. In both cases, the mission would have been completed. This is fortunately not the case.
F I N .
