Orbital perturbations

Simplified perturbations models

Simplified perturbations models are a set of five mathematical models (SGP, SGP4, SDP4, SGP8 and SDP8) used to calculate orbital state vectors of satellites and space debris relative to the Earth-centered inertial coordinate system. This set of models is often referred to collectively as SGP4 due to the frequency of use of that model particularly with two-line element sets produced by NORAD and NASA. These models predict the effect of perturbations caused by the Earth’s shape, drag, radiation, and gravitation effects from other bodies such as the sun and moon. Simplified General Perturbations (SGP) models apply to near earth objects with an orbital period of less than 225 minutes. Simplified Deep Space Perturbations (SDP) models apply to objects with an orbital period greater than 225 minutes, which corresponds to an altitude of 5,877.5 km, assuming a circular orbit. The SGP4 and SDP4 models were published along with sample code in FORTRAN IV in 1988 with refinements over the original model to handle the larger number of objects in orbit since. SGP8/SDP8 introduced additional improvements for handling orbital decay. The SGP4 model has an error ~1 km at epoch and grows at ~1–3 km per day. This data is updated frequently in NASA and NORAD sources due to this error. The original SGP model was developed by Kozai in 1959, refined by Hilton & Kuhlman in 1966 and was originally used by the National Space Surveillance Control Center (and later the United States Space Surveillance Network) for tracking of objects in orbit. The SDP4 model has an error of 10 km at epoch. Deep space models SDP4 and SDP8 use only 'simplified drag' equations. Accuracy is not a great concern here as high drag satellite cases do not remain in "deep space" for very long as the orbit quickly becomes lower and near circular. SDP4 also adds Lunar–Solar gravity perturbations to all orbits, and Earth resonance terms specifically for 24-hour geostationary and 12-hour Molniya orbits. Additional revisions of the model were developed and published by 2010 by the NASA Goddard Space Flight Center in support of tracking of the SeaWiFS mission and the at the Jet Propulsion Laboratory in support of Planetary Data System for navigational purposes of numerous, mostly deep space, missions. Current code libraries use SGP4 and SDP4 algorithms merged into a single codebase in 1990 handling the range of orbital periods which are usually referred to generically as SGP4. (Wikipedia).

Video thumbnail

(ML 13.6) Graphical model for Bayesian linear regression

As an example, we write down the graphical model for Bayesian linear regression. We introduce the "plate notation", and the convention of shading random variables which are being conditioned on.

From playlist Machine Learning

Video thumbnail

Numerically Calculating Partial Derivatives

In this video we discuss how to calculate partial derivatives of a function using numerical techniques. In other words, these partials are calculated without needing an analytical representation of the function. This is useful in situations where the function in question is either too co

From playlist Vector Differential Calculus

Video thumbnail

PDE FIND

We propose a sparse regression method capable of discovering the governing partial differential equation(s) of a given system by time series measurements in the spatial domain. The regression framework relies on sparsity promoting techniques to select the nonlinear and partial derivative

From playlist Research Abstracts from Brunton Lab

Video thumbnail

B27 Introduction to linear models

Now that we finally now some techniques to solve simple differential equations, let's apply them to some real-world problems.

From playlist Differential Equations

Video thumbnail

Convolution

Convolution In this video, I introduce the notion of convolution and give an example and some applications. It is a very way of multiplying two functions that is useful analysis and PDEs. Here is the demo I showed: https://phiresky.github.io/convolution-demo/ Convolution Intuition: http

From playlist Partial Differential Equations

Video thumbnail

(ML 7.7) Dirichlet-Categorical model (part 1)

The Dirichlet distribution is a conjugate prior for the Categorical distribution (i.e. a PMF a finite set). We derive the posterior distribution and the (posterior) predictive distribution under this model.

From playlist Machine Learning

Video thumbnail

(ML 7.8) Dirichlet-Categorical model (part 2)

The Dirichlet distribution is a conjugate prior for the Categorical distribution (i.e. a PMF a finite set). We derive the posterior distribution and the (posterior) predictive distribution under this model.

From playlist Machine Learning

Video thumbnail

Essential Cosmological Perturbation Theory by David Wands

PROGRAM : PHYSICS OF THE EARLY UNIVERSE - AN ONLINE PRECURSOR ORGANIZERS : Robert Brandenberger (McGill University, Montreal, Canada), Jerome Martin (Institut d'Astrophysique de Paris, France), Subodh Patil (Instituut-Lorentz for Theoretical Physics, Leiden, Netherlands) and L Sriramkumar

From playlist Physics of The Early Universe - An Online Precursor

Video thumbnail

The Problem of Traffic: A Mathematical Modeling Journey

How can we mathematically model traffic? Specifically we will study the problem of a single lane of cars and the perturbation from equilibrium that occurs when one car brakes, and that braking effect travels down the line of cars, amplifying as it goes along, due to the delayed reaction ti

From playlist Cool Math Series

Video thumbnail

33. Electronic Spectroscopy: Franck-Condon

MIT 5.61 Physical Chemistry, Fall 2017 Instructor: Professor Robert Field View the complete course: https://ocw.mit.edu/5-61F17 YouTube Playlist: https://www.youtube.com/playlist?list=PLUl4u3cNGP62RsEHXe48Imi9-87FzQaJg This lecture covers intermolecular interactions, electronic spectrosco

From playlist MIT 5.61 Physical Chemistry, Fall 2017

Video thumbnail

Michal KOWALCZYK - Kink dynamics in the $\phi^4$ model...

Kink dynamics in the $\phi^4$ model: asymptotic stability for odd perturbations in the energy space We consider a classical equation $\[\phi_{tt}-\phi_{xx}=\phi-\phi^3,\quad (t,x)\in\RR\times\RR\] known as the $\phi^4$ model in one space dimension. The kink, defined by $H(x)=\tanh(x/{\sqr

From playlist Trimestre "Ondes Non linéaires" - June Conference

Video thumbnail

Least squares method for simple linear regression

In this video I show you how to derive the equations for the coefficients of the simple linear regression line. The least squares method for the simple linear regression line, requires the calculation of the intercept and the slope, commonly written as beta-sub-zero and beta-sub-one. Deriv

From playlist Machine learning

Video thumbnail

Cosmological Perturbation Theory (Lecture 1) by David Wands

PROGRAM PHYSICS OF THE EARLY UNIVERSE (HYBRID) ORGANIZERS: Robert Brandenberger (McGill University, Canada), Jerome Martin (IAP, France), Subodh Patil (Leiden University, Netherlands) and L. Sriramkumar (IIT - Madras, India) DATE: 03 January 2022 to 12 January 2022 VENUE: Online and Ra

From playlist Physics of the Early Universe - 2022

Video thumbnail

(ML 10.6) Predictive distribution for linear regression (part 3)

How to compute the (posterior) predictive distribution for a new point, under a Bayesian model for linear regression.

From playlist Machine Learning

Video thumbnail

04 1 Local Sensitivity Analysis

Local sensitivity analysis

From playlist QUSS GS 260

Video thumbnail

Introduction to Resurgence, Trans-series and Non-perturbative Physics II by Gerald Dunne

Nonperturbative and Numerical Approaches to Quantum Gravity, String Theory and Holography DATE:27 January 2018 to 03 February 2018 VENUE:Ramanujan Lecture Hall, ICTS Bangalore The program "Nonperturbative and Numerical Approaches to Quantum Gravity, String Theory and Holography" aims to

From playlist Nonperturbative and Numerical Approaches to Quantum Gravity, String Theory and Holography

Video thumbnail

Hossein Mobahi: "Differential Operators for Generating Structured Adversarial Examples"

High Dimensional Hamilton-Jacobi PDEs 2020 Workshop II: PDE and Inverse Problem Methods in Machine Learning "Differential Operators for Generating Structured Adversarial Examples" Hossein Mobahi - Google AI Abstract: Adversarial examples are created by adding a small perturbation to an i

From playlist High Dimensional Hamilton-Jacobi PDEs 2020

Video thumbnail

Wei Wu -- Massless phases for the Villain model in dimension 3 and greater

The XY and the Villain models are mathematical idealization of real world models of liquid crystal, liquid helium, and superconductors. Their phase transition has important applications in condensed matter physics and led to the Nobel Prize in Physics in 2016. However we are still far from

From playlist Columbia Probability Seminar

Video thumbnail

(ML 10.7) Predictive distribution for linear regression (part 4)

How to compute the (posterior) predictive distribution for a new point, under a Bayesian model for linear regression.

From playlist Machine Learning

Video thumbnail

Galaxy Bias Loops by Roman Scoccimarro

Program Cosmology - The Next Decade ORGANIZERS : Rishi Khatri, Subha Majumdar and Aseem Paranjape DATE : 03 January 2019 to 25 January 2019 VENUE : Ramanujan Lecture Hall, ICTS Bangalore The great observational progress in cosmology has revealed some very intriguing puzzles, the most i

From playlist Cosmology - The Next Decade

Related pages

Perturbation (astronomy) | Orbital state vectors