August 20, 2014 at 10:55How not to get lost on the comet Churyumov-Gerasimenko
- Transfer
Original article published 2014/08/15 17:30 UTC
Rosetta almost completed its first original triangular orbit in front of a comet. (It turns out that the apparatus’s maneuvers do not take place around the comet’s center of mass, but around the point located on its illuminated side.) Every day we get views of the nucleus from different positions. Stunning relief details are everywhere, but in this insane world, it’s really difficult to navigate, so it’s hard to say if I look at the same objects in different photographs. I found out that many observers have the same problem, and decided to try to collect some images that will help us navigate Rosetta’s new home!
This attempt would be much easier if the objects on the surface had names, but of course, there are no official names and titles; Rosetta has just arrived and mapping will take some time. It is tempting to give names to various features of the relief, but it is somewhat arrogant and will become completely useless when official names appear. Therefore, I will give descriptions to talk about some of the objects that interest me, and I hope in the future, I will be able to give them official names.
First, let's see how a comet rotates in space. The comet consists of large and small lobes connected by a narrow isthmus. The axis of rotation of the comet is located at the point where a large fraction is connected to the isthmus. The coordinate system for the comet has already been designated, with the north and south poles at the points where the axis of rotation leaves the nucleus. A large fraction is the prime meridian, and a small fraction is the 180th. Let's see how the coordinate grid lays on the comet's surface in this animation:
ESA / Rosetta / DLR / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA
Geography and sunlight on comet Churyumov-Gerasimenko
So, if we look at the left side of the animation, we will see a color image of the comet. We will not pay attention to green spots; look at the red and yellow areas. These colors indicate how often different areas of the comet are illuminated by the sun. Red areas are almost always lit. You can see that there are two poles of eternal light, one on each of the lobes. If some part is always lit, that is, areas that are constantly in the shade. Most of the comet above 30 degrees north latitude is always lit. Therefore, we do not see that part of the comet that is below 30 degrees south latitude.
From the animation it becomes clear that if you take any photo of the comet and arrange it so that the light goes as if from above, then the north will also be from above. The only time this does not work is when Rosetta removes the north pole itself.
Of course, looking at the latest pictures from NavCam, I realized that most of them are looking at the pole. Here are all the photos taken by NavCam during the first round. The top row is a pole shot, so I placed them so that a small fraction (180 degrees longitude) was at the top. The bottom row is made at a slight angle, so I arranged them so that the north was approximately on top. (Not sure which row to place the top-right photo on.)
ESA / Rosetta / NavCam / Emily Lakdawalla
NavCam images of comet Churyumov-Gerasimenko from Rosetta's first orbit
Now we are a little oriented and can take yesterday's image from the OSIRIS camera. In fact, this is a pair of images, left and right stereo pair. This is the first image of a comet that covers the entire OSIRIS camera review. OSIRIS has the largest detector outside the Earth at the moment: it's a 4 megapixel camera, each image with a side of 2048 pixels. Take your red-blue glasses and enjoy the 3D view, or just view the left or right image separately.
ESA / Rosetta / DLR / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA
Churyumov-Gerasimenko in 3D, August 7, 2014
What are we looking at? We look through a large share towards a small share. The north pole is tilted slightly to the left.
I see three completely different types of terrain. The first is a very, very smooth surface. In my opinion, it looks like a mantle hiding something under it. In one place, I noticed something similar to an impact crater on it. I think that there were other impact craters, the edges of which are smeared or destroyed.
In some places there are cobblestone fields. There is one particularly noticeable field on the isthmus. I already said that I will give only descriptions, but it seems I will never get rid of the thought that this chain of cobblestones looks like a necklace.
On some images from NavCam you can also see a group of strange vertical furrows. In some places, they look as if they are on top of the smooth surface of the isthmus; in other places they seem to be slightly covered by him, bulging out of it.
But the surface that really attracts attention is a place on the wall of a small lobe that looks towards the isthmus. It is striped or ribbon. I would not say that it is layered. This is a pronounced surface with folds, small ridges and depressions. Several intersecting surfaces are possible. You can see the transverse folds on the steep slopes, which begin from a smoother surface and to the pole of light in a small fraction. This surface consists of a fairly coherent material that creates impressive silhouettes against a black space background.
Here is a more general view with NavCam.
In other places, the comet is also replete with objects with high round edges. Surprisingly round. It’s hard for me to imagine how such high round edges can be made, unless it is impact craters.
But if these are impact craters, then a lot has happened to them since they formed. See what an interesting object at the top on the ridge.
Starting on Sunday, Rosetta will go into a slightly lower orbit, about 80 km, and the rest of August will conduct observations from this altitude. Stay in touch!
PS Moved to the Cosmonautics hub. Thanks to all!
PPS I will be glad to error messages in PM.
Rosetta almost completed its first original triangular orbit in front of a comet. (It turns out that the apparatus’s maneuvers do not take place around the comet’s center of mass, but around the point located on its illuminated side.) Every day we get views of the nucleus from different positions. Stunning relief details are everywhere, but in this insane world, it’s really difficult to navigate, so it’s hard to say if I look at the same objects in different photographs. I found out that many observers have the same problem, and decided to try to collect some images that will help us navigate Rosetta’s new home!
This attempt would be much easier if the objects on the surface had names, but of course, there are no official names and titles; Rosetta has just arrived and mapping will take some time. It is tempting to give names to various features of the relief, but it is somewhat arrogant and will become completely useless when official names appear. Therefore, I will give descriptions to talk about some of the objects that interest me, and I hope in the future, I will be able to give them official names.
First, let's see how a comet rotates in space. The comet consists of large and small lobes connected by a narrow isthmus. The axis of rotation of the comet is located at the point where a large fraction is connected to the isthmus. The coordinate system for the comet has already been designated, with the north and south poles at the points where the axis of rotation leaves the nucleus. A large fraction is the prime meridian, and a small fraction is the 180th. Let's see how the coordinate grid lays on the comet's surface in this animation:
ESA / Rosetta / DLR / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA
Geography and sunlight on comet Churyumov-Gerasimenko
So, if we look at the left side of the animation, we will see a color image of the comet. We will not pay attention to green spots; look at the red and yellow areas. These colors indicate how often different areas of the comet are illuminated by the sun. Red areas are almost always lit. You can see that there are two poles of eternal light, one on each of the lobes. If some part is always lit, that is, areas that are constantly in the shade. Most of the comet above 30 degrees north latitude is always lit. Therefore, we do not see that part of the comet that is below 30 degrees south latitude.
From the animation it becomes clear that if you take any photo of the comet and arrange it so that the light goes as if from above, then the north will also be from above. The only time this does not work is when Rosetta removes the north pole itself.
Of course, looking at the latest pictures from NavCam, I realized that most of them are looking at the pole. Here are all the photos taken by NavCam during the first round. The top row is a pole shot, so I placed them so that a small fraction (180 degrees longitude) was at the top. The bottom row is made at a slight angle, so I arranged them so that the north was approximately on top. (Not sure which row to place the top-right photo on.)
ESA / Rosetta / NavCam / Emily Lakdawalla
NavCam images of comet Churyumov-Gerasimenko from Rosetta's first orbit
Now we are a little oriented and can take yesterday's image from the OSIRIS camera. In fact, this is a pair of images, left and right stereo pair. This is the first image of a comet that covers the entire OSIRIS camera review. OSIRIS has the largest detector outside the Earth at the moment: it's a 4 megapixel camera, each image with a side of 2048 pixels. Take your red-blue glasses and enjoy the 3D view, or just view the left or right image separately.
ESA / Rosetta / DLR / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA
Churyumov-Gerasimenko in 3D, August 7, 2014
What are we looking at? We look through a large share towards a small share. The north pole is tilted slightly to the left.
I see three completely different types of terrain. The first is a very, very smooth surface. In my opinion, it looks like a mantle hiding something under it. In one place, I noticed something similar to an impact crater on it. I think that there were other impact craters, the edges of which are smeared or destroyed.
In some places there are cobblestone fields. There is one particularly noticeable field on the isthmus. I already said that I will give only descriptions, but it seems I will never get rid of the thought that this chain of cobblestones looks like a necklace.
On some images from NavCam you can also see a group of strange vertical furrows. In some places, they look as if they are on top of the smooth surface of the isthmus; in other places they seem to be slightly covered by him, bulging out of it.
But the surface that really attracts attention is a place on the wall of a small lobe that looks towards the isthmus. It is striped or ribbon. I would not say that it is layered. This is a pronounced surface with folds, small ridges and depressions. Several intersecting surfaces are possible. You can see the transverse folds on the steep slopes, which begin from a smoother surface and to the pole of light in a small fraction. This surface consists of a fairly coherent material that creates impressive silhouettes against a black space background.
Here is a more general view with NavCam.
In other places, the comet is also replete with objects with high round edges. Surprisingly round. It’s hard for me to imagine how such high round edges can be made, unless it is impact craters.
But if these are impact craters, then a lot has happened to them since they formed. See what an interesting object at the top on the ridge.
Starting on Sunday, Rosetta will go into a slightly lower orbit, about 80 km, and the rest of August will conduct observations from this altitude. Stay in touch!
PS Moved to the Cosmonautics hub. Thanks to all!
PPS I will be glad to error messages in PM.