This project holds the source code for the 3D and 2D animations used in http://sankara.net/chandrayaan3.html. That page shows an animation of the orbit of the ISRO Chandrayaan 3 mission.
I created this animation for educational purposes. It has the following features:
- Real-world orbit data and predictions based on information available from JPL/NASA HORIZONS interface
- Rendering of the orbit in 2D and 3D
- Rendering of the orbit with either Earth or Moon at the center
- Rendering of the orbit with views locked on Earth, Moon, or the spacecraft
- Views aligned with J2000 reference axes
- Information on all earth bound and moon bound maneuvers (engine burns)
- Realistic textures for Earth and Moon in 3D mode
- Astronomically correct rendering of sunlight on Earth and Moon, poles, and polar axes
- Various animation controls for education - camera controls (pan, zoom, rotate), timeline controls, visibility controls
- A Joy Ride feature which lets you fly along with Chandrayaan 3
The animation has 2D and 3D rendering modes.
The 2D mode uses SVG and D3 JS. Planetary orbits are rendered as ellipses based on orbital elements. Spacecraft orbits are rendered using line segments using position data.
The 3D mode uses THREE JS.
JQuery and JQueryUI are used for control and information panels.
Orbit data is fetched offline from JPL/NASA HORIZONS. This data in CSV format is processed a bit and converted into JSON format for use in the animation. A few astronomy functions are based on Steve Moshier's routines.
The Perl script orbits.pl is used to fetch orbit data during development time from NASA JPL HORIZONS web interface.
The script supports the following options:
--phase=[geo|lunar] # geocentric or selenocentric phase -- defaults to geo
--data-dir=<datadir> # place to save orbit data files -- defaults to .
--use-cache # use orbit data retrieved and saved earlier -- optional
Raw orbit data obtained from JPL is stored into the following files:
ho-<id>-elements.txt # orbital elements for one instant of time
ho-<id>-vectors.txt # co-ordinates for a period of time
Orbital elements are also stored here (though they aren't used at present):
ho-<id>-orbit.txt # orbital elements for one instant of time
Orbit data for use by the JavaScript is written in JSON format in a time-stamped directory under data-fetched:
geo-cy3.json # contains all geocentric orbit data (elements and vectors)
lunar-cy3.json # contains all selenocentric orbit data (elements and vectors)
The site consists of the following three sets of files:
chandrayaan3.html # HTML page
cy3.js # JavaScript handling animation
astro.js # A few astronomy support functions
cy3.css # CSS for the web page
whatsnew-cy3.html # What's new page
geo-cy3.json # contains all geocentric orbit data
lunary-cy3.json # contains all selenocentric orbit data
d3.v3.min.js
ephemeris-0.1.0.min.js (https://github.com/mivion/ephemeris)
jquery.dialogextend.min.js
jquery-ui-1.10.3.custom.min.js
jquery-1.9.1.js
three.min.js
TrackballControls.js
css/ui-darkness/images/*
css/ui-darkness/*.css
images/* (earth and moon textues for a few sources)
ga.js # Google analytics
At present the page can be hosted statically. There are no server components needed. However, to prevent browsers from complaining about CORS, one may use a tiny web server like Mongoose to test the local site.
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"Chandrayaan-2 in flight configuration" (https://skfb.ly/6SoMv) by tashtego is licensed under Creative Commons Attribution (http://creativecommons.org/licenses/by/4.0/).
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Jon D. Giorgini for helping with the JPL/HORIZONS interface and data. He was very responsive whenever I mailed him my queries. He has been of great help since 2013 for the Mars Orbiter Mission until now for the Chandrayaan 3 mission.
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Members of the Bangalore Astronomy Society (http://bas.org.in/) for their valuable feedback
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Members of the Reddit r/isro (https://www.reddit.com/r/ISRO/) community for their valuable feedback
The code base needs a rewrite. The very first release was for the Mars Orbiter Mission launch in 2013. Minor changes were made later to support MOM Mars orbit insertion and the Pluto flyby of New Horizons.
After a gap of 6 years, this was been modified again in 2019 to support the Chandrayaan 2 mission. The major changes were for 3D support. In that process, the code quality has degraded.
After another gap of 4 years, it has now been prepped for Chandrayaan 3.
The rewrite will focus on present-day JavaScript tooling, better abstraction, better separation of concerns (2D vs. 3D, model vs. rendering, etc.), extensibility (how does one extend the code for a new mission easily merely by changing configurations), performance (decrease the load time; improve rendering smoothness; on-demand loading of high resolution LRO textures), and responsive UX. The current UX is not too great mobile screens.