Questions tagged [orbital-elements]

Orbital elements are a set of parameters that uniquely identify a specific orbit.

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34
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3answers
48k views

How to programmatically calculate orbital elements using position/velocity vectors?

I would like to build some orbital mechanical software from scratch. I feel that this would be a great way to learn the steps required to calculate different Kepler orbital elements of an object, plot ...
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How (the heck) are military satellites with (apparently) classified TLEs still showing up on sat map websites?

As I first noted in this comment I couldn't get TLEs for the recently launched OFEQ-11 spy satellites from space-track.com. When I looked at Search Resuls: OFEQ 11 Satellite details 2016-056A NORAD ...
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2answers
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Nuances of the terms (mean / osculating / Keplerian / orbital) elements

I've been assuming that osculating, Keplerian, and orbital elements are all synonyms, with mean orbital elements just being these averaged over some time. However occasional comments make me suspect ...
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1answer
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Brouwer-Lyddane mean semi major axis bias

I'm using the software GMAT (General Mission Analysis Tool) (website, YouTube) for propagating spacecraft and calculating their Brouwer-Lyddane (BL) mean semi-major axis (SMA). I found out something ...
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2answers
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Where to look for historical or reconstructed orbit data for early NASA missions - Mercury-Atlas 6 for example

After reading this answer to How many earth stations had astronauts on-site during John Glenn's orbit in Friendship-7? I decided that for my own use I'd like to plot the orbit of Mercury-Atlas 6, the ...
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2answers
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What's a Brouwer-Lyddane mean semi major axis, or any other, for an orbit in a lumpy gravity field?

The really nicely written question Brouwer-Lyddane mean semi major axis bias describes the use of the software GMAT (General Mission Analysis Tool) (website, YouTube, giant PDF for TESS) for ...
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4answers
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Converting Orbital Elements to Cartesian State Vectors

Updated 2016-12-12 I'm writing an orbital mechanics program in Unity. I convert an orbiting object's position and velocity into orbital elements, then converting the orbital elements back into ...
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2answers
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What is the accuracy / uncertainty of Two Line Elements (TLEs)?

I use TLE sets supplied on this website to find the future position of satellites (well usually just the ISS) using the SGP4 propagation method implemented in C++. My question is: What is the ...
13
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4answers
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How to obtain UTC of the epoch time in a satellite TLE (two line element)?

I want to convert the epoch time of a TLE to UTC. At this moment I am less interested in explanations and history - I just want to know quantitatively, with certainty, how to convert. I'm confused ...
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2answers
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What is hyperbolic eccentric anomaly F?

I have no idea what this is and have been searching on the net but all I get is eccentric anomaly. The equation that relates hyperbolic eccentric anomaly F to its true anomaly $\theta$ is exactly the ...
6
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1answer
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What is this algorithm to calculate orbital state vectors?

I came across the following algorithm to calculate the cartezian vectors from the orbital elements: First calculate some coefficients that will be used in determining the position: $$ r_x' = a (\cos ...
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1answer
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How to calculate the time to apoapsis & periapsis, given the orbital elements?

I have the 6 orbital elements (excluding Time of Periapsis Passage, obviously), 2 state vectors, and a lot of other parameters like orbital period. I am looking to use them to calculate the time to ...
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How to get true anomaly from time?

An exercise that was left unsolved from last year's class gives me this equation : $$ t-t_{p} = \sqrt{\frac{a^3}{\mu}}*(\arcsin(X) - e*X) $$ where : $$ X = \frac{\sqrt{1-e^2}*\sin(v)}{1+e*\cos(v)}. $$...
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What is the highest inclination orbit ever attained from a Cape Canaveral launch?

The launch facilities at Cape Canaveral, FL are located at a latitude of about 28.5° N, so that puts a hard lower bound on inclinations from that site. I assume there are well-defined azimuth limits ...
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How to get velocity vector from GPS NMEA data?

I am writing a program to receive and interpret NMEA data from a GPS receiver. I am working with an Adafruit Ultimate GPS Receiver integrated with an Arduino. The $GPRMC NMEA Sentence contains the ...
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3answers
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Lowest possible lunar orbit and has any spacecraft achieved it?

Because the Moon has no atmosphere a spacecraft can theoretically cruise at a very low orbit. What is the lowest possible lunar orbit and which spacecraft achieved it? Was it the Lunar Module of ...
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2answers
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Calculating velocity state vector with orbital elements in 2D

I'm writing a little project that simulates an orbit by converting from initial state vectors $\vec{r}$ and $\vec{v}$ to Keplerian elements, then converting back to $\vec{r}$ and $\vec{v}$ from those ...
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2answers
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Can the Right Ascension and Argument of Perigee of a spacecraft's orbit keep varying by themselves with time?

I came across the orbital data for a low Earth orbit spacecraft and one thing which I am not able to understand is why does its Right Ascension of ascending node and Argument of Perigee keep changing ...
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2answers
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Osculating oscillations! What makes Akatsuki's eccentricity and inclination about Venus vary periodically?

Watching this animated GIF of Akatsuky's orbit I noticed that it seems to "walk" around Venus. Some orbital elements oscillate ~3-4 times a year, others drift and then slowly "step up ...
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1answer
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At which point would two GSO/GEO satellites with similar orbital elements be closest to each other?

While I was answering another question on How closely spaced are satellites at GEO I came to realize I can't really word it with much conviction how two close proximity satellites in GEO/GSO orbits ...
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1answer
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How to get semi-major axis from TLE?

This should be fairly straightforward, but, how do I get the semi-major axis (a) from at TLE. For example if I have the TLE: ...
5
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1answer
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How to calculate the orbital distance between 2 satellites given the TLEs

I have 2 LEO satellites with the same orbital plane with same inclination & longitude of the ascending node. I have the TLEs for each satellite. How do I calculate the orbital distance between the ...
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Why does NASA Horizons say that Earth inclination is not 0 at J2000 epoch?

I'm using NASA Horizons system to get Earth orbital elements with following settings: ...
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2answers
741 views

Deriving the changes in Keplerian Elements induced by small impulses

I'm trying to make derive a concise table of the effects on each Keplerian orbital element for a small impulse in the Radial, Tangential, or Perpendicular direction at periapsis or apoapsis, good to ...
4
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1answer
131 views

How satellite orbital vacancies are determined?

Before a new satellite is launched, its desired orbital altitude, inclination is determined. Now with thousands of satellites already in orbit at different altitudes, how do we know if our desired ...
4
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2answers
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Where can I find examples of orbital state vectors?

I'm currently trying to write a program that can calculate orbital trajectories. The goal is to take any orbital state vector (position, velocity) and convert it into Keplerian orbital elements, or ...
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2answers
766 views

From osculating to mean equinoctial elements and back

I'm struggling with orbital elements... I'm trying, at the same time as finding a clear definition to them, to write a piece of code to switch from osculator elements to mean equinoctial elements. I'...
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1answer
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Calculate True Anomaly at future point in time with hyperbolic orbits

Given: Semi Major Axis (negative) Eccentricity (>1) Argument of Periapsis Inclination Longitude of Ascending Node Current True Anomaly Mass of Central Body How can one calculate the true anomaly at ...
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1answer
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J2 long-period perturbations in the inclination

As a continuation of my previous post regarding the use of the software GMAT (General Mission Analysis Tool) (website, YouTube) for propagating spacecraft, I have an additional question. This time I ...
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3answers
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what does Check sum TLE mean?

I am doing a report on TLE's and I was looking up what the numbers mean. I found a very helpful site. See here: http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/SSOP_Help/...
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Why is the sidereal period of the Earth 362.392667 days?

Using JPL's Horizons API I can look at the orbital elements for the EM Barycenter wrt the Solar System Barycenter at J2000. The output looks like this: Watch for the PR (Sidereal orbit period) ...
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1answer
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How Local time of a sun synchronous orbit is related to Right ascension of ascending node?

My question may sound naive and hence would like to apologise if this question is already answered in same or other form in this forum. How does ...
5
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1answer
955 views

How are Two Line Elements (TLEs) obtained?

This question is a follow up of another question I have asked recently. For the sake of experiment I propagated the ISS's position (using SGP4) from epoch of first TLE to the epoch of next released ...
5
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1answer
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Keplerian Orbital Elements ↔ Cartesian ECEI with WGS84 Corrections

I'm trying to write code to go back and forth between equatorial KOE (Keplerian Orbital Elements) and ECEI (Cartesian). ECEI→KOE I found here: How to programmatically calculate orbital elements ...
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0answers
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Plotting satellite ground track with calculated latitude and longitude at a given moment

I have obtained the Classical Orbital Elements for a satellite on a given epoch, and now I would like to plot them on a 2D map. ...
3
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2answers
135 views

Generating JPL HORIZONS parameters for use with JPL HORIZONS itself

I want to be able to calculate RA/Dec for a given body with JPL HORIZONS, using a heliocentric specification of the orbital elements for a small solar system body (say, Apophis), but instead of using ...
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1answer
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Space rocket payload by inclination

I know that near the equator where the inclination is 0° it is easier to put payloads to low earth orbit because of the advantage of rotation speed of earth which saves more fuel. Saving more fuel ...
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2answers
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Are 3 points on an orbit enough to determine the shape of it in practice?

In a question about determining orbital elements from two points on an orbit, some discussion arouse regarding how many points are actually necessary, since two is not sufficient. Determining a conic ...
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1answer
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Is there a low Earth orbit with a 24-hour day night cycle?

Are there any possible low-Earth orbits that use precession to match Earth's day/night cycle? So like SSO, but specifically aimed to achieve a 24hr day/night in LEO. If so, what would its parameters ...
5
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2answers
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How significant is orbit propagator choice/error when considering a year-long satellite coverage simulation, and which is the most appropriate?

I'm currently considering a project to simulate the (Earth-seeing) coverage of 1 or more satellites over the course of a year. The point would be to compare how different orbits result in different ...
5
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1answer
899 views

Why is argument of periapsis defined in terms of longitude of ascending node?

According to the Keplerian system of orbital elements, a reference direction is given; the longitude of the ascending node is an angle with respect to that direction, and the argument of periapsis, ...
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1answer
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TLE SGP4 Coordinate Transformations

I am working on developing a user friendly SGP4 orbit propagator in C on a PIC24. I have extensively read Revisiting Spacetrack Report #3 and celestrak - there are a few outstanding questions I have....
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1answer
207 views

Why does the eccentricity of Venus's (and other) orbits as reported by Horizons vary based on the frame origin and basis?

I did try to think this through before posting, but I am going to need some explanation. In my (perhaps naïve) view, an ellipse will have the same eccentricity no matter what frame it is in. In ...
4
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1answer
277 views

Under what conditions can a non-resonant satellite stay hidden from an observer on the ground?

From the perspective of someone on the ground, a satellite is usually not above the horizon all the time. But can a satellite have such an orbit that it is never above the horizon? Such orbits clearly ...
3
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1answer
567 views

Geocentric latitude and longitude of sub-satellite point

I was trying to derive the expressions for the geocentric latitude and longitude of the sub-satellite point using Keplerian elements. The final equations connecting the combination of the Keplerian ...
3
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1answer
266 views

What is the angle between two orbits in the equatorial plane?

My orbit is in the equatorial plane. When i apply thrust in the y or x axis, it rotates around the focus or planet - see red and blue orbit in the image below. I know the the semi-major-axis and ...
3
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2answers
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Given an arrival date, is there a way to calculate the declination and right ascension of the arrival asymptote into Mars?

I am designing an Earth-Mars transfer. The launch window is 03-Jul-2026 (departure from Earth) & 22-Jun-2028 (Mars arrival). The declination and right ascension for the departure asymptote from ...
3
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1answer
64 views

Is it possible to represent an orbit with just a periapsis position and 2 angular velocities?

I was thinking of how complex the orbital elements are and got to wondering whether you can represent orbits in a more simple way. If you start with an ECI coordinate frame and you know the spherical ...
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2answers
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Does the James Webb Telescope have a Two Line Element set?

How do you track the position of the James Webb telescope? Does it have its own TLE, or...?
2
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1answer
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Orbital Component Abbreviations

I'm currently in the process of writing an SDK for the ESA's DISCOSweb API. I've come across these attributes on Orbital details. ...