JUICE Cesium Viewer
The JUICE Cesium Viewer is a web based tool for attitude and coverage visualization to support the detailed planning process of the Strategic Science Planning of the JUICE Science Operations Center.
Cesium Viewer is powered by Cesium and provides the capability to interactively display GIS products and Cesium scenes over the targets of the JUICE mission. The Cesium Viewer accepts the following formats:
GeoJSON
KML
CZML
A Video Tutorial is available as a complement to this user manual.
Overview
The JUICE Cesium Viewer is intended to support detailed operational scenario analysis by providing attitude and observation coverage in 3D and 2D space by taking advantage of the Cesium Platform, the open platform for software applications designed for 3D geospatial data.
the Cesium Viewer allows to explore the main bodies of the JUICE mission in high level of details and to load a scene that contains a JUICE model and its ephemerides (via SPICE Kernels) in order to be able to visualize a given trajectory and attitude of the spacecraft and its components. In addition, there is the possibility to load observation GeoJSON files that correspond to the geometry of the footprints of a given instrument timeline.
GeoJSON is a format for encoding a variety of geographic data structures which is adept for features and regions of interest of a given planetary body and also for the footprints of the observations of an instrument timeline.
The JUICE scenes and the footprint GeoJSON files are generated by the SOC during the Detailed Scenario planning process but can also be generated by using the cesium-script Python package with the adequate inputs.
Detailed Scenarios
Detailed Scenarios are extracted from the outcome of a science segmentation plan and are developed as detailed sizing case analysis for science operations: for specific challenging sections of the segmentation, in-depth analysis is needed in order to refine resources assumptions (attitude, power, data volume…). Those detailed analysis, as similar as possible to the real ones, performed at observation level are done in collaboration with the instrument teams and are integrated in the trajectory segmentation, ensuring its feasibility.
For these detailed scenarios an in-depth design and understanding of the JUICE spacecraft attitude and the observation coverage at different stages of the detailed scenario process is fundamental for the design of the science observations and high-level resources analysis. The JUICE Cesium Viewer is designed for that purpose.
Tool Audience
The main audience of Cesium Viewer are the Instrument Teams and the SOC Operations Scientists involved in the detailed scenario planning and science observations definitions.
Accessibility
Cesium Viewer is publicly accessible from the JUICE SOC Website
in Science Operations Planning Tools > Cesium Viewer. It
is also available from
JUICE Core System Toolkit menu in the
Cesium Viewer panel.
The tool is also directly available from Cesium Viewer.
User interface
The Cesium Viewer interface starts with a “Getting Started” page that provides guidance to the user on how to use the tool and provides a link to the tool introductory video. The tool displays the chosen celestial body on the center (Europa by default).
Choosing the Central Body
The central body can be changed by clicking on the top-left body icon. The available bodies are the ones relevant for JUICE operations: Callisto, Earth, Europa, Ganymede, Io, Jupiter, the Moon, and Venus.
Datasets Panel
On the left there is a button that opens the datasets panel. The dataset panel contains the currently displayed data sets (scenes and GeoJSONs) and allows the user to manually import data sets.
Browse available data by selecting “Explore catalogue” or click “Load data” to add your own data. Once you have added data to the scene, your active data sets are listed here in your workbench. The workbench will help you to interact with the data. In the workbench you can toggle data sets on and off, change their opacity and change styles, and navigate through dates and times, if the data supports this functionality.
When selecting “Explore catalogue” (for example for Europa) you will see different types of data available:
Scene (spacecraft icon): Spacecraft trajectory and attitude data
GeoJSON Observations (landscape icon): Instrument timeline observation footprints data
Topographic (map icon): IAU Topographic Nomenclature of the given body
Similarly these are the types of data you can load wth “Load data”. These data are described in better detail hereunder.
Scenes
Scenes provide you with the option to show/hide them, remove them, download the scene (in *.czml format), see
catalogue info, and also to open the scene panel with the S/C icon. The scene panel allows you to choose to display
the following items of the scene:
Model: JUICE S/C model
Path: JUICE S/C trajectory path
Sensors: JUICE Instruments Field-of-view (FOV) frustums as defined the the Instrument Kernels of the SPICE Kernels. Note that not all the FOVs are available
Ground-track: JUICE S/C ground-track on the central body. When activating the ground-track, it’s colormap can be chosen among the following geometrical quantities: Altitude, Phase, Emission, and Incidence.
Observations
Similarly to the scene data, Observations in GeoJSON format have the option to show/hide them, remove them, download the scene
(in *.geojson format, which can be read by many other applications), see catalogue info, and also to open the
GeoJSON panel with the landscape icon that allows you to assign a color to each footprint based on a colormap. The
colormap can be chosen among the following geometrical quantities: Altitude, Phase, Emission, and Incidence. In addition
the colormap can be related to a FOV in the case that the GeoJSON file contains multiple FOVs for different instruments
(or for the same instrument).
In addition, different palettes can be chosen for the colormap.
Topographic
Similarly to the scene data, Topographic data has the option to show/hide them, remove them, download the scene
(in *.geojson format, which can be read by many other applications), see catalogue info, and also to open the
color palette panel to assign a color to the landmarks.
Viewer Display
The viewer display is the central element of the Cesium Viewer and displays all the available elements of the tool. It’s usage is described in Using the Cesium Viewer. The display has:
a top-right menu,
a right menu,
bottom-right latitude/longitude display,
and bottom time controls,
the functionalities of which are described hereunder.
Display Controls
Pan view: Left click + drag
Zoom view: Right click + drag, or mouse wheel scroll
Rotate view: Middle click + drag, or CTRL + Left/Right click + drag
The controls with a touchpad are also outlined in the Help menu.
Bottom-right Latitude and Longitude Display
On the bottom-right of the display, there is a JUICE icon to the left of which the Latitude and Longitude of the cursor is provided when the cursor is on top the central body.
Time Controls
Whenever A Scene Data is loaded, time controls appear on the bottom of the display. These controls allow the user to control the time for which the spacecraft trajectory, attitude, and relevant projected data will be displayed. They consist on a wheel that displays the time speed factor and the date and that allows to control the time speed factor, start/pause the scene and to make time move forwards or backwards.
Next to the wheel there is a timeline bar, also with dates and with an icon that provides the current time of the scene, this icon can be moved across the timeline to select the time of interest.
On top of the timeline the altitude (km) and off-nadir (deg) are provided. Off-nadir is the angle in between the sub-spacecraft point on the central body and the spacecraft +Z axis.
Using the Cesium Viewer
This section provides some working examples of the Cesium Viewer not covered by the description of the tool and its user interface.
Exploring a Planetary Body
When the Cesium Viewer is started and a central body is selected the first obvious functionality is to explore the central body.
A feature of Cesium Viewer is that when you zoom in a central body if higher-resolution imagery is available, the user will see it being loaded (this is the case for Europa for example). By doing so and activating the lat/lon grid along with loading the IAU topographic nomenclature, Cesium viewer can be an adept tool to simply explore the planetary body.
If the IAU topographic nomenclature is loaded, points and areas of interest will be highlighted. These landmarks are also searchable. When clicking them a context menu will appear with information extracted from the GEOJson file providing a number of parameters of interest such as Feature Type Code, Diameter, Target, Coordinates, Feature type, etc.
JUICE Spacecraft Trajectory and Attitude Scene
One of the main functionalities of the Cesium Viewer is to display the trajectory and attitude of JUICE based on a Cesium Viewer “Scene”, this scene has been described in 40_cesium_viewer:Scene.
You can load a scene either by choosing from the catalogue of each central body (there are many scenes available for the main events of the planetary fly-bys) or by loading your own data. These data can be generated with the cesium-script Python package.
A scene contains the trajectory and attitude of JUICE as provided by a given SPICE meta-kernel for a start and stop time and with a given time step. Using Cesium Viewer for this purpose can be a complement for the usage of Cosmographia Plugin especially if the user prefers to use a web based tool that does not require a local installation.
When a scene is loaded, the center of the scene becomes the JUICE Spacecraft rather than the central body and the right icons allow the user to display the S/C trajectory, ground-track and a number of instrument FOV frustums. The center of the scene can be switched to the central body by using the Top-right Menu Home icon and back to the JUICE S/C by using the Right Menu rocket icon.
The description of the scene is available from the catalogue that is accessible from the red icon of the Right Menu.
JUICE Instrument Coverage Visualization
The other main functionality of the Cesium Viewer is to display and extract information from JUICE instrument’s footprints from a given set of observations.
You can load instrument footprints (in GeoJSON format) choosing from the catalogue of each central body (there are some observations available for the 7E1 Europa flyby) or by loading your own data. These data can be generated with the cesium-script Python package.
When a set of footprints, or observations are loaded they appear on the surface of the central body. You can edit their color by using the panel described in Observations. Note that the observation set can correspond to a single FOV of an instrument, several FOVs of an instrument, or even for several instruments. In cases where more than one FOV is present in the set, distinguishing the footprint colors by FOV can be useful.
When the footprints are in the display they can be selected with a left-click, by doing so a number of properties is displayed in a context menu. Additionally, the context menu has a camera icon that centers the view of the display on the given footprint. The available quantities are based on SPICE calculations and are the following:
Observation Date in UTC
Phase angle in degrees
Incidence angle in degrees
Altitude in Km
SPICE ID: Indicates the SPICE name or ID of the FOV
SPICE frame: Indicates the SPICE frame that the instrument field of view is defined from
Observation keyword (true if the GeoJSON contains an observation)
Using the observation footprint with the Cesium Viewer is complementary with the coverage analysis that one can perform with the Planetary Coverage Tool Python package and not only that but also both tools will be able to be used interchangeably in the near future.
Known Limitations
Polar Anti-Meridian observations: To avoid artifacts and miss-behaviors of Cesium, the feature crossing the anti-meridian is cut in two polygons (multi-polygon feature).
2D view performance: the performance when using the 2D equirectangular projection might be sub-optimal with some observations. This does not happen with the 3D and the pseudo-3D views.