Astrodynamics - Science topic

I'm looking for suggestion to publish a manuscript in a free journal.

Thank you for your help.

Hi, I use two models to calculate the atmosphere density during a satellite orbit propagation. The two models are NRLMSISE-00 and DTM-2000. To feed the models I'm using Space Weather Data provided by Celestrak (https://celestrak.com/SpaceData/SW-Last5Years.txt). I was surprised the see that both adjusted and observed data are provided in this file. I found that observed data must be used for NRLMSISE-00 model. However, I didn't see any information about which type of data to use (i.e., adjusted or observed) for DTM-2000. Does anyone have the answer or a reference?

Hello, I am a Master's student studying Astrodynamics.

I am using Machine Learning to estimate future Orbital Element of satellites.

Recently, I found that True Longitude, Mean Longitude, and Argument of Latitude show almost linear form, and I would like to find information about this.

Is there a paper or journal related to this result?

And can I consider these as linear?

Astrodynamics

Apart from the fact the it Is impossible to known the position of movement object (Heisenberg principle), spacecraft are acted upon by influential gravitational forces which tend deviate the direction of the vehicle and generate lots of induce drag. Beside every body is in motion . do is it to determine the location and speed of spacecraft?

I am trying to determine the equilibrium points in the astrodynamics system, but the equilibrium condition is a highly nonlinear system of equations. I have tried the 'fsolve' in Matlab, but it is very sensitive to the initial guess of the solution and is lack of robustness. So I am wondering whether there is any better solver in Matlab or any other software package.

It is well known that for a typical halo orbit around L1 or L2 libration point in circular restricted three-body problem its monodromy matrix has eigenvalues of the following form:

It is also well known that eigenvectors associated with lambda1 and lambda2 linearly approximate directions along the unstable and stable invariant manifolds, respectively. What about other lambdas?

As I understand, the compex pair (lambda5 and lambda6) is associated with a two-dimensional invariant subspace in which vectors rotate by the angle rho, where lambda5 = exp(i*rho). Am I right?

What about lambda3 and lambda4? Since the system of equations in CR3BP is Hamiltonian and autonomous, each periodical orbit has at least 2 eigenvalues equal to +1. So, in our case, the algebraic multiplicity is 2. What about geometric multiplicity? As I understand, there is at least one eigenvector, assotiated with 1, it is the direction along the orbit. Is it true that another independent eigenvector (if any) is directed along the family of halo orbits?

It is well known that there are periodical three-dimensional orbits around L1 and L2 libration points in circular restricted three-body problem called halo orbits. Existence of these orbits is justified numerically: anybody can state a system of nonlinear equations (conditions of symmetry and orthogonality to the xz plane) and solve it numerically to obtain a solution with high precision. But is there any analytical proof that these periodical orbits exist, mathematically?

As I know, existence of the Lyapunov orbits in CR3BP is a consequence of the Lyapunov's centre theorem:

But why halo orbits exist? Why there is an energy level at which there is a bifurcation from the planar Lyapunov orbits that gives rise to halo orbits?

Fundamentally, we can address the key initial parameters in planetary formation, dynamics, and evolution as being astrophysical in nature. These astrophysical parameters lead to specific geologic and atmospheric conditions of every planet or moon. In a search for the most fundamental quantities that determine the characteristics of a planetary surface and atmosphere, I have devised the attached categories and list of parameters. My question is, which of these are the most fundamental and influential to the evolution of a planet or moon? Has the magnitude of importance of these fundamental quantities been tested? Most importantly: what mostly dictates how a planet become its unique set of conditions? Some qualities are guaranteed to be more imprint in some scenarios than in others, but which are the most common, and how do they manifest together into a unique planetary body? For example: changes in what parameters lead to what different planetary outcomes?

There is a chance that since the moon's gravity is strongest at that point this will minimize the orbital decay. The satellite could also be placed to periodically pass through the high tide to reduce on orbital decay.

Can my idea work?

I have gone through the extensive work of Laplace and Guass in this field however most of the material i have found is not compact enough to deduce numerical results and ends up in a number complex equations. I am unable to get a hold of the step to solve the problem numerically. Any help would be much appreciated. Thanks.

When a magnet is deployed in a satellite approaching the Earth's magnetic poles there is an attraction that accelerates the spacecraft. The magnet should be disabled on approaching the magnetic pole to prevent the satellite dipping into the Earth's atmosphere.

Any satellite containing a magnet can be deorbited since there will always be an attraction on it towards the magnetic poles that will cause it to move to a given magnetic pole and dive into the Earth's atmosphere.

A magnetic spacecraft placed at a certain distance from the Sun for example  will align itself with the Sun's magnetic field and will slowly drift towards the Sun due to the magnetic attraction. This opens up another possibility for space travel.

How feasible is my proposal?

Do the Flying saucers contain giant wheels as a century fuse (e.g. to create artificial gravity – by spinning at high-speed)?

Is the shape of a saucer (i.e. shape of magnifying or convex lens) is ideal shape for deflecting space debris (e.g. to minimize damage)?

If mankind wish to travel to nearby planets such as Mars, don’t we need to study the reasons or possible advantages for saucer shape?

I am not saying, aliens travelled to Earth. But we all know that the most popular shape for the UFO is Flying saucers.

I like to know pros and cons and thoughts who have done more investigation. I am just a curious bystander. I saw a small bit on returning of US astronaut after nearly spending one year in the space. Also the news mentioned that, it would take about 1 year just to reach Mars.

This is the weekend, so wish to explore something fun and interesting. If UFO contains a gain-wheel/centrifuge. How many hours a day should we need to run the gain-wheel/centrifuge to maintain healthy bone mass density?

Of course, it is possible to run the gain-wheel/centrifuge at different speeds in order to exert different weight (e.g. ranging from 0.5G or 1.5G). Of course, such power consumption can be meat by a mini nuclear power plant. I am sure, such advanced civilizations could have developed such mini nuclear power plant.

Best Regards,

Raju Chiluvuri

can any one tell me how to calculate the rotation curves in early -type galaxies (elliptical-lenticullar)? can I use the same equation for spiral galaxies?

What is the approximated value of the area-to-mass ratio of a spent rocket upper stage on GTO used in the launch of a GEO satellite? 0.005 m^2/kg or larger?

Maybe invention, or practical applications with good outcomes such ascommercially success, or perhap discoveries.

How is the trajectory known with the comet losing debris (as the weight must be a factor) in the perihelion around the sun before it comes close to Earth. Will the comet slow down or speed up in it perihelion around the sun?

I am interested to approach non-conservative perturbations from the point of view of a "canonical formalism". I am really curious what references on this topic might be found in the literature.

In the case of general relativity the change in coordinate can give rise to fictitious perturbations, for which we can use gauge invariant variables or we can also choose a specific gauge. My question is how to decide which gauge is suitable for a particular problem?