I used to be familiar with the various choices out there for orbital mechanics simulation software. Alas, those days are gone. What are the choices today, preferably sorted by platform?
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To add to @Erik's list:
GMAT — Cross platform, Free. NASA open source product.
FreeFlyer — PC, commercial. Probably AGI's biggest competitor.
The Java Astrodynamics Toolkit — Cross platform, free. Another open source product, more of a software library than a full-fledged simulation environment.
Orbit designer — Android, free. Not even close to the same ballpark of these other packages, but might be a fun way to play around with different orbits. Edit: I actually just downloaded this and I'm absolutely hooked. Highly recommended. (Caveat: I'm a nerd for things like this, and it may in fact be a rather boring app for most people).
Here are the options I'm aware of off the top of my head:
Apart from these serious software mentioned above there is an interesting game with quite realistic orbital calculations, quite suitable for teaching kids about space: Kerbal space program.
As for AGI non-free version is a lot more powerful.
Shameless plug for Tudat (TU Delft Astrodynamics Toolbox)...
If you're looking for something that allows you a lot of freedom to set up and play with simulations, you might want to consider an open-source C++ project I've been working on for the last few years as part of my PhD. Most of the graduate students in my group use it, so a lot of effort has gone into it.
As far as games/simulations go, I have stumbled upon Orbiter. Seems to have quite a few add-ons and a forum. Unfortunately, works under Windows only.
Orekit is the best space mechanics tool I know. Developed in Java (cross-platform), Orekit is a space dynamics open source library, based on Common Apache Math.
Despite the fact it has no visualisation tool so far, the different force model it contains make it a really good choice if your plan is to solve accurate flight dynamics problem.
Orekit includes all available IERS convention for frame definition. It includes orbit propagators of 3 types :
- Analytical (Kepler, Eckstein-Heschler, SDP4/SGP4 with 2006 corrections)
- Numerical (with customizable force models)
- semi-analytical propagation based on Draper Semianalytic Satellite Theory (DSST) with customizable force models.
For information, you'll find on the same address above the Rugged add-on. Rugged is a sensor-to-terrain mapping tool which takes into account Digital Elevation Models (DEM) in its line of sight computation. It is a free software intermediate-level library written in Java and implemented as an add-on for Orekit.
Here are some of the features Orekit provides :
Time
high accuracy absolute dates
time scales (TAI, UTC, UT1, GPS, TT, TCG, TDB, TCB, GMST, GST ...)
transparent handling of leap seconds
Geometry
frames hierarchy supporting fixed and time-dependent (or telemetry-dependent) frames
predefined frames (EME2000/J2000, ICRF, GCRF, ITRF93, ITRF97, ITRF2000, ITRF2005, ITRF2008 and intermediate frames, TOD, MOD, GTOD and TOD frames, Veis, topocentric, tnw and qsw local orbital frames, spacecraft body, Moon, Sun, planets, solar system barycenter, Earth-Moon barycenter)
user extensible (used operationally in real time with a set of about 60 frames on several spacecraft)
transparent handling of IERS Earth Orientation Parameters (for both new CIO-based frames following IERS 2010 conventions and old equinox-based frames)
transparent handling of JPL DE 4xx (405, 406 and more recent) and INPOP ephemerides
transforms including kinematic combination effects
composite transforms reduction and caching for efficiency
extensible central body shapes models (with predefined spherical and ellipsoidic shapes)
cartesian and geodesic coordinates, kinematics
Spacecraft state
Cartesian, Keplerian (including hyperbolic), circular and equinoctial parameters
Two-Line Elements
transparent conversion between all parameters
automatic binding with frames
attitude state and derivative
Jacobians
mass management
user-defined associated state (for example battery status, or higher order derivatives, or anything else)
Propagation
analytical propagation models:
Kepler
Eckstein-Heschler
SDP4/SGP4 with 2006 corrections
numerical propagation with:
customizable force models:
central attraction
gravity models (automatic reading of ICGEM (new Eigen models), SHM (old Eigen models), EGM and GRGS gravity field files formats, even compressed)
atmospheric drag (DTM2000, Jacchia-Bowman 2006, Harris-Priester and simple exponential models) and Marshall solar Activity Future Estimation
third body attraction (with data for Sun, Moon and all solar systems planets)
radiation pressure with eclipses
solid tides, with or without solid pole tide
ocean tides, with or without ocean pole tide
general relativity
multiple maneuvers
state of the art ODE integrators (adaptive stepsize with error control, continuous output, switching functions, G-stop, step normalization ...)
computation of Jacobians with respect to orbital parameters and selected force models parameters
serialization mechanism to store complete results on persistent storage for later use
semi-analytical propagation based on Draper Semianalytic Satellite Theory (DSST) with customizable force models:
central body with full gravity model
third body attraction
atmospheric drag
radiation pressure with eclipses
tabulated ephemerides:
file based
memory based
integration based
unified interface above analytical/numerical/semianalytical/tabulated propagators for easy switch from coarse analysis to fine simulation with one line change
all propagators can be used in several different modes:
slave mode: propagator is driven by calling application
master mode: propagator drives application callback functions
ephemeris generation mode: all intermediate results are stored during propagation and provided back to the application which can navigate at will through them, effectively using the propagated orbit as if it was an analytical model, even if it really is a numerically propagated one, which is ideal for search and iterative algorithms
handling of discrete events during integration (models changes, G-stop, simple notifications ...)
predefined discrete events:
eclipse (both umbra and penumbra)
ascending and descending node crossing
apogee and perigee crossing
alignment with some body in the orbital plane (with customizable threshold angle)
raising/setting with respect to a ground location (with customizable triggering elevation)
date
altitude crossing
target detection in sensor field of view (circular or dihedral)
complex geographic zones traversal
impulse maneuvers occurrence
possibility of slightly shifting events in time (for example to switch from solar pointing mode to something else a few minutes before eclipse entry and reverting to solar pointing mode a few minutes after eclipse exit)
Attitude
extensible attitude evolution models
predefined laws:
central body related attitude (nadir pointing, center pointing, target pointing, yaw compensation, yaw-steering)
orbit referenced attitudes (LOF aligned, offset on all axes)
space referenced attitudes (inertial, celestial body-pointed, spin-stabilized)
tabulated attitudes
Orbit file handling
loading of SP3-a and SP3-c orbit files
loading of CCSDS orbit data messages
Atmosphere models
tropospheric delay (modified Saastamoinen)
geomagnetic field (WMM, IGRF)
Customizable data loading
loading from local disk
loading from classpath
loading from network (even through internet proxies)
support for zip archives
support from gzip compressed files
plugin mechanism to delegate loading to user defined database or data access library
Localized in several languages
English
French
Galician
German
Greek
Italian
Norwegian
Romanian
Spanish
PyEphem provides scientific-grade astronomical computations for the Python programming language. Given a date and location on the Earth’s surface, it can compute the positions of the Sun and Moon, of the planets and their moons, and of any asteroids, comets, or earth satellites whose orbital elements the user can provide. Additional functions are provided to compute the angular separation between two objects in the sky, to determine the constellation in which an object lies, and to find the times at which an object rises, transits, and sets on a particular day.
The numerical routines that lie behind PyEphem are those from the wonderful XEphem astronomy application, whose author, Elwood Downey, generously gave permission for us to use them as the basis for PyEphem.
This script prints out where the Jovian moons are around Jupiter for the next few days.
import ephem
moons = ((ephem.Io(), 'i'),
(ephem.Europa(), 'e'),
(ephem.Ganymede(), 'g'),
(ephem.Callisto(), 'c'))
# How to place discrete characters on a line that actually represents
# the real numbers -maxradii to +maxradii.
linelen = 65
maxradii = 30.
def put(line, character, radii):
if abs(radii) > maxradii:
return
offset = radii / maxradii * (linelen - 1) / 2
i = int(linelen / 2 + offset)
line[i] = character
interval = ephem.hour * 3
now = ephem.now()
now -= now % interval
t = now
while t < now + 2:
line = [' '] * linelen
put(line, 'J', 0)
for moon, character in moons:
moon.compute(t)
put(line, character, moon.x)
print str(ephem.date(t))[5:], ''.join(line).rstrip()
t += interval
print 'East is to the right;',
print ', '.join([ '%s = %s' % (c, m.name) for m, c in moons ])
3/2 12:00:00 g e J i c
3/2 15:00:00 ge J i c
3/2 18:00:00 g e J i c
3/2 21:00:00 g e J i c
3/3 00:00:00 g e J i c
3/3 03:00:00 g e Ji c
3/3 06:00:00 g e i J c
3/3 09:00:00 g e i J c
3/3 12:00:00 g e i J c
3/3 15:00:00 g ie J c
3/3 18:00:00 g i e J c
3/3 21:00:00 g i e J c
3/4 00:00:00 g i e c
3/4 03:00:00 g Jie c
3/4 06:00:00 g J ie c
3/4 09:00:00 g J ie c
East is to the right; i = Io, e = Europa, g = Ganymede, c = Callisto
Here's a few other things out there as well depending on what you're looking for...
While not a simulator for orbital mechanics, I found this Trajectory Browser from Nasa to be interesting.
More game-like is the LEO launcher app and the launch simulator.
There's the JPL 3d simulator and the Near-Earth-Object Simulator (both web based). There is also a JPL SSD simulator and here's some quick start instructions. Like so:
For *nix (linux, unix) systems there is also the FERMI toolset with an overview here.
Popular and Free game is orbital simulator in 3-d mentioned by deer hunter.
iTraject might be very useful for learning orbital mechanics. Its numerical solver makes it very flexible. It also uses very precise astronomical algorithms for celestial positions. You can actually set your initial date, predict when your vehicle will be in Moon's SOI with analytical calculations, and make a flyby around the Moon. Moreover, you can get ground station, epoch and keplerian elements parameters with current time.
here a video: http://www.youtube.com/watch?v=msCEdOq5WhI
You could try Stellarium for locating most celestial objects from the earth frame. AFAIK, it works very well on Linux, and is available for OS X and Windows as well.
Eric Stoneking / NASA Goddard Space Flight Center share '42' as the (mostly harmless) spacecraft dynamics simulation
It's cross platform, has various capabilities, and is a neat tool overall.
GODOT is a more recent/modern option. It's actively developed and used by ESA both for active operations as well as analysis for future missions.
Check out Saber Astronautics' PIGI. https://saberastro.com/
By far the best graphics and great ease of use, awesome for visualizing orbits on all the planets.
Their casual license starts at just $15 a month, so worth looking at. PC and Mac.