View Rosetta's comet
Introduction
View Rosetta’s comet is an interactive tool that allows you to view comet 67P/Churyumov-Gerasimenko using a 3D shape model derived from images taken with Rosetta’s navigation camera, NAVCAM. This page describes some of the features of the tool, provides some background to the main components of the tool, and outlines its current status.
Version 1 (beta) of the View Rosetta’s comet was released on 13 August 2015.
System requirements
This interactive 3D visualisation tool is supported only by WebGL compatible browsers and graphics cards. Further information about WebGL is available here.
General features of the tool
In version 1 of the tool, you can explore the surface of the comet as seen by the NAVCAM, and view and download some of the best images of the comet that are available in the ESA Archive Image Browser.
Currently, the tool supports two shape models (see below for further details about these models). By default, the tool loads with the Malmer shape model but you can choose to load the ESA NAVCAM shape model by selecting this alternative from the horizontal options panel.
Using the mouse you can zoom in and out, rotate the comet, and pan across the screen. Note that in version 1, you can rotate the view 360 degrees in the horizontal direction, with only limited rotation in the vertical direction. Rotation around the comet’s natural rotation axis can be turned on with the Comet Rotate option. At any stage you can return to the default perspective by clicking on Reset View.
Scientists have identified a number of different geological regions on the surface of comet 67P/C-G. These can be highlighted on the Malmer model by clicking on Comet Regions and choosing from the menu that subsequently appears.
The Display Observations option allows you to toggle blue spheres that represent points along Rosetta’s trajectory. Click on any of these to see NAVCAM images taken from that position; follow the links to access the full-size images from the ESA Archive Image Browser. Note that in version 1, the comet orientation is not synchronised with the images.
Some simple changes to the lighting in the scene can be made using Light Options.
Notes on specific elements of the tool
Rotating comet
By turning on Comet Rotate, the comet can be made to rotate around its natural rotations axis. In version 1 of the tool, the rotation is not synchronized with the spacecraft trajectory. This means that the orientation of the comet model will not automatically match the view seen in the NAVCAM images, although the user can of course use the navigation controls (zoom, pan, rotate) to manually change the perspective to match the image view.
Observation points
The blue spheres represent points along the trajectory of the Rosetta spacecraft from which the images have been taken. The distances, relative to the comet centre, have been calculated using the position data in the original FITS file headers.
Lighting
You can adjust the lighting in the scene by using the Light Options. The option Ambient light adjusts the intensity of the light; by adjusting the Theta and Phi variables, it is possible to emulate the effect of sunlight incident from different azimuthal (theta) and polar (phi) angles.
Shape models
Two comet shape models are provided in version 1 of the tool. These have been created for different purposes and with different sets of NAVCAM images, and for these reasons they differ in some aspects.
ESA NAVCAM shape model
ESA’s Rosetta Flight Dynamics Team regularly produce comet shape models to use in planning navigation around this oddly-shaped comet. You can read more here about how they construct their models, using techniques such as silhouette carving and stereophotoclinometry.
The ESA NAVCAM shape model used in version 1 of the tool was generated from NAVCAM images of the comet obtained during the close orbit phase in September and October 2014. The files for this model are available to download from here. (Note that the version of the shape model shown in the tool has been optimised to reduce the file size.)
A new ESA NAVCAM shape model will be provided with each new release of NAVCAM images in the Archive Image Browser. The comet viewer will be updated to take account of these.
Malmer shape model
Mattias Malmer developed a comet shape model based on NAVCAM images that were released via the Archive Image Browser in May 2015 as well as images that have been posted on the Rosetta blog. Malmer constructed his model using a combination of three techniques: silhouette carving – mostly for the dark southern hemisphere regions; stereo correlation, which is more suited to capturing large scale variations; and photoclinometry (shape from shading), which works well for capturing fine details. Regions of the comet that had not been imaged were smoothed out for aesthetic reasons. The files for this model are available to download from here (zip file).
In addition to the shape model, Malmer also used the NAVCAM images to generate a texture file for the surface. This is divided into 19 regions coinciding with the distinct geomorphological boundaries that had been identified in January 2015.
NAVCAM images
The images that can be accessed using this tool are all available from the ESA Archive Image Browser. Version 1 of the comet viewer tool provides access to images from 1 August 2014 to 13 January 2015. As new NAVCAM images are added to the browser, these will also be accessible from the viewer.
Reporting errors or bugs
We are aware of some bugs or features in this beta version of the tool, including one in the navigation that affects vertical scrolling. We will endeavour to fix these as quickly as we can.
To report problems with the tool or bugs, please send a message, with subject ‘comet viewer’, to esa.science@esa.int outlining what the problem is and what browser/platform you are using. We will do our best to rectify these problems in the next version of the tool.