34
votes
Does the Voyager team use a wrapper (Fortran(77?) to Python) to transmit current commands?
In 2015, the last original Voyager engineer still on the project, retired. NASA specified that his replacement would have to know FORTRAN.
The software was updated regularly after launch:
The ...
- 126k
19
votes
Accepted
What computer programs does ITAR say I can or can not write, or share, or use in the US?
With the exception of model rockets made of paper, wood, or breakable plastic, that are passively stabilized, that have low thrust and low delta V, and that do not have guidance software, launch ...
- 73.2k
15
votes
How does the poliastro python package "Going to Mars with Python" example work? What's it really doing?
Full disclaimer: I'm the author and main developer of poliastro.
The most important step before doing anything is somehow retrieving the positions and velocities of the planets of the Solar System. ...
- 1,052
15
votes
Does the Voyager team use a wrapper (Fortran(77?) to Python) to transmit current commands?
The Voyager spacecraft are still being patched as of 2023.
The uplink is only 16 bits/second, just enough to send (simple) commands. How these commands are generated is irrelevant to the spacecraft. ...
- 14.1k
11
votes
Thrust and rotation strategy to circularize a standard GTO orbit using ion propulsion?
TL; DR: Trajectory optimization for continuous thrust is difficult and this field is very active in research.
2021 clarifications:
Methodology
For the least amount of fuel, the best is the thrust the ...
- 6,200
11
votes
Does the Voyager team use a wrapper (Fortran(77?) to Python) to transmit current commands?
I didn't work on Voyager, but can tell you that deep-space missions tend to retain the original ground hardware, software, language, and build environment, both for continuity/safety as well as budget ...
- 381
10
votes
Accepted
How to get earth-centered, earth-fixed coordinates from Skyfield?
Skyfield ≥1.34
The most recent versions of Skyfield introduce an explicit itrs reference frame that rotates with the Earth. You can learn about it starting here:
...
- 971
9
votes
Accepted
How to calculate the flight path angle, γ, from a state vector?
This is a problem that has plagued groups of people very knowledgeable about orbital dynamics but who learned using different textbooks: there are two different definitions of "flight path angle"!!
...
- 18.2k
8
votes
Accepted
Get dates when a satellite has performed maneuver from historical TLE data (python)?
For Python and TLE propagation using SGP4 one very handy option is https://rhodesmill.org/skyfield/
As you probably already know a TLE is a strange animal. It does not really contain proper orbital ...
- 149k
7
votes
Accepted
How to best think of the State Transition Matrix, and how to use it to find periodic Halo orbits?
The State Transition Matrix (STM)
The STM is a linearization procedure of a dynamical system. It can be used for any non-linear dynamical system and is used to approximate the dynamics of a system ...
- 6,200
7
votes
Accepted
How to solve the two-body problem in the ECI frame through numerical integration?
There are several ways to do this. The easiest and most straightforward is to break it into two sets by including velocity as a variable, and solve together.
Instead of a single second order ...
- 149k
7
votes
Why did my vis-viva math solution get so close despite being wrong? Under what conditions would it have been a good approximation?
First, you appear to have the following misunderstanding of the solar sail force vectors:
Tilt it at 45 degrees to make the thrust tangential
Thrust is not tangential at 45 degrees.
In fact, a ...
6
votes
Accepted
A software for orbit propagation, considering Moon, Sun and zonal harmonics
I would highly recommend NASA Goddard's GMAT (General Mission Analysis Tool). It is quite user friendly, has a number of tutorials, and has been used in spacecraft operations.
- 6,200
6
votes
Accepted
Python API for JPL Horizons?
callhorizons is depricated now and refers to the python library astroquery which now seems to be the way to go.
astroquery (GitHub, readthedocs) is "an astropy ...
- 206
6
votes
What formulas do I use to calculate the gravity and drag forces on an object ascending from Earth's surface?
One thing that may be tripping you up is that the d term in the gravitational formula is the distance between the centers of mass of the objects, not the altitude ...
- 167k
6
votes
How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time?
You're plotting the orbit of a geosynchronous satellite in active commercial use. At the scale you've drawn it, it has to overlap exactly, because variation smaller than you can see at this ...
- 7,778
6
votes
Python Libraries: Numerical Propagators and Access Calculations
Disclaimer: I'm the author and lead developer of poliastro. Happy to see many others are recommending it, though! :) I also work for Satellogic, the company that open sourced orbit-predictor.
I have ...
- 1,052
6
votes
Accepted
Has Skyfield or any other SGP4-capable open-source Python package yet wrapped/implemented the new, improved SGP4 (version 8+)?
The new SGP4 library comes with a Python wrapper in the same zip archive file (also Java, Matlab, and Visual Basic, and documentation for the C API), but it's not at all idiomatically Pythonic, since ...
- 7,778
6
votes
Modelling ISS orbit in GMAT
The reason my GMAT model was not giving the correct results was that I changed the Epoch without changing the TA - user @notovny pointed that out which was very helpful. I used TLE-tools to get the ...
- 141
6
votes
Calculating and Drawing the orbit of a body in a 2D gravity simulation in python
The easiest initial approach to this is probably to propagate your state forward in time steps, with a time delta small enough to have reasonable accuracy.
You can ...
5
votes
Accepted
"Pythagorean Three Body Problem" - need some points from an accurate solution for comparison
I just ran it, and mine look pretty much like those in the paper.
See some coordinates at the bottom.
Here are some {x,y} coordinates at the times in the left column:
...
- 58.5k
5
votes
Saving STK Scenario from Python app
Your variable root is of type IAgStkObjectRoot. If you search the Programming Interface Help, there are five save related ...
- 4,444
5
votes
Accepted
How to calculate position of GPS Satellite with transmitted ephemeris data?
You can find a C++ method contained in the source code of Andrew Holme homemade GPS receiver project. The method is called GetXYZ and is the EPHEM (ephemeris) namespace and looks as the following:
<...
- 121
5
votes
Python Libraries: Numerical Propagators and Access Calculations
Check out PoliAstro by Juan! It's got great visualisation tools in addition to its propagation. Plyades too, is a library for orbit propagation with visualisation. I have heard that there is a ...
- 343
5
votes
Simulating engine burn with scipy ode solve
For an instantaneous delta V, you definitely want to have the integrator stop exactly at the point in time where the change in velocity is to be applied. Dynamic step sized integrators stop where they ...
- 73.2k
5
votes
Accepted
How much delta-v have I used here? What's the "official" equation for delta-v from parametric thrust?
As $\Delta v$ is just change in velocity, we can just integrate the norm of the acceleration function over time:
$$\Delta v = \int|\mathbf{a}(t)| dt$$
You're out of luck getting a closed form of that ...
5
votes
Accepted
Skyfield, how to use https:// instead of ftp://?
Looks like this was an issue that was fixed and closed recently so try updating your copy of Skyfield to at least version 1.31.
- 2,506
5
votes
GMAT - Locating inter-spacecraft contact instead of spacecraft to ground station
I am not familiar with GMAT, but there is another route to solve this challenge using an extensively validated open-source solution.
You can use the Orekit Astrodynamics library to build one Moon-...
- 443
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