# Questions tagged [frames]

Usage and transformations of frames of reference

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### Definition of ECL50 coordinate frame?

Is there a document with the definition of the "ECL50" frame? It was used at least in the Voyager and Ulysses missions. I have seen in literature people saying "ECL50 is the same as ...
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### GCRS and ICRS Frame in Optical Observations from near earth

Lets say I am trying to observe the night sky. My telescope has a pointing direction. I want to compare the RADecs of each star with another. Now I have 4 cases. My telescope is on a satellite ...
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### Rates of change of Euler angles to angular velocity of a rotating coordinate system

I am trying to implement the conversion between TEME and GCRF frames following the same procedure as done in SPICE. After digging into CSPICE's code, this transformation is performed through the ...
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### Are ECI and ECEF Frames, and Do They Belong to the Geocentric Equatorial Coordinate Systems?

I'm completely confused about the difference between geocentric equatorial coordinate systems, ECI, and ECEF. David Vallado, in his book 'Fundamentals of Astrodynamics and Applications,' mentions that ...
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### Perifocal to ECI using Argument of Latitude

Suppose a satellite is orbiting Earth in a circular orbit. I know the following orbital elements: Inclination i, RAAN (Ω), Semi-major axis a (or orbit radius given that it is a circular orbit) ...
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### ISS (ZARYA) TLE to Latitude Longitude Conversion

I am trying to take TLE of ISS (ZARYA) and get the latitude longitude and height. I am aware the TLE is in TEME~(True Equator Mean Equinox) frame. This means that the TLE was generated considering the ...
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### Spacecraft attitude: rotation between ECI, LVLH, and Body frames

I'm starting to study spacecraft attitude control and I'm quite confused about the attitude representation in different frames. By reading a bunch of textbooks and papers, I understood that I can ...
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### Is this a typo in the Python Skyfield API? "International Coordinate Reference Frame (ICRF)"?

In the Python Skyfield library there is a position object skyfield.positionlib.ICRF, in the documentation it states: An (x,y,z) position and velocity oriented to ...
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### How do I convert from one local NED frame to another?

A little bit of background in case you are interested. I am running a re-entry simulation, and I am dealing with two different reference frames. The one with the higher fidelity dynamics is in the ...
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### Are the TLE of a satellite computed with the ECI or ECEF?

I want to compute the distance of a certain satellite, given the TLE, to a ground station in the earth. I have the latitude, longitude and altitude of the ground station. But I don't know if the TLEs ...
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### Conversion of velocity vectors between ICRF frames with different central objects

Following the very nice answers to this question, I am trying to implement an appropriate procedure for change of central body during orbit propagation. The very interesting thesis by Mana Vautier ...
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### How can we determine the most appropriate central body for orbit propagation?

I have recently been experimenting with expanding my numerical propagator to satellites that orbit central bodies other than Earth. I started with the Moon (using GRGM1200B gravity model), and found ...
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### Conversion of acceleration in inertial frame to non-inertial rotating frame

Let's take as example frames the GCRF (inertial, Earth-centered, non rotating) and ITRF (non-inertial, Earth-centered, rotating). Previous questions have discussed the conversion of position and ...
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### Conversion of velocity vector in ITRF to GCRF

As explained in the answer to this question, IERS technical notes give a clear procedure to convert coordinates between the GCRF and ITRF frames. However, I believe these refer only to position ...
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### What is the inertial heliocentric reference system used by NASA JPL to calculate the ephemerides of Near Earth Objects?

I'm using the website of NASA JPL Horizon system at this link Small-Body Database Query to download a database of orbital elements for NEOs (asteroids and comets). Although I checked the Horizons ...
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### What is different between Hill frame and LVLH frame in satellite?

What is different between Hill frame and local-vertical, local-horizontal (LVLH) frame in satellite? I add one figure to show this two frame. reference of figure: Weiss, Avishai, Uroš V. Kalabić, ...
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### What is the rationale behind NORAD's use of TEME?

The most popular catalog of Earth-orbiting objects is NORAD’s. The catalog provides the so-called « two-line elements » (TLE) which essentially are computed orbital parameters of a catalogued object, ...
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### How is the Celestial Ephemeris Pole (CEP) exactly defined?

I am currently trying to understand the definition of the True Equator Mean Equinox (TEME) frame. I found a very nice explanation in @NgPh's answer to Can someone explain to me the TEME reference ...
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### Why does targeting in the VNB frame lead to a different maneuver magnitude than targeting in an inertial frame?

In GMAT, I set up a targeter (this script) to compute an impulsive maneuver in an inertial frame. The differential correcter finds a maneuver of 3.1161 km/s . If I change the impulsive maneuver to be ...
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### How to find a vector's elevation angle with respect to a point on Earth?

tl;dr: Spacecraft's antenna should point to a ground station but there is a pointing error. I want to express the error as a vector rather than a simple angle that a dot product provides, so that I ...
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### Calculating body frame X vector's look direction in GEO (NED) frame from roll, pitch and yaw data, is this correct?

I have roll, pitch and yaw angle values for a LEO satellite. Satellite orbit frame and spacecraft body frame are defined as LVLH. The satellite position and velocity are given in ECI/GEI frame. I have ...
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### The appropriate reference frame for the interplanetary missions

In the JPL Horizons there are Earth mean equator and ecliptic reference planes. The ecliptic is an apparent path of the Sun's ...
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### Usage of the coordinate systems in orbit propagation

For the orbit propagation in ECI coordinate system, considering the effects of zonal harmonics and Sun/Moon perturbations the following procedure was formed: Convert the state vector to ECEF ...
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### How to calculate the speed of rotation of a given point on the Earth's WGS84 ellipsoid, about its axis?

Launches often happen near the equator in order to take advantage of Earth's rotation speed. This is why more launches are towards the East than towards the West. How can one calculate the speed of ...
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### What is the difference between GCRS and J2000 frames?

What is the difference between GCRS and J2000 frames? Which is commonly used worldwide in satellite communications? I've read a statement here, that ...
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### Reference frames - why do I need to convert to Geocentric Equatorial State Vector to solve equation of motion?

I am asking this question in relation to an example shown in the 'Orbital Mechanics for Engineering Students' book by Howard Curtis (third edition) pp659 example 12.1. The example is demonstrating how ...
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