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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 ...
George X.'s user avatar
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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 ...
NIKITA SEHRAWAT's user avatar
5 votes
1 answer
202 views

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 ...
Rafa's user avatar
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2 votes
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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 ...
ed190's user avatar
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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) ...
Suraj's user avatar
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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 ...
zephyr0110's user avatar
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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 ...
Chicca's user avatar
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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 ...
KDecker's user avatar
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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 ...
alexmesa's user avatar
1 vote
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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 ...
DaDSPGuy's user avatar
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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 ...
Rafa's user avatar
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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 ...
Rafa's user avatar
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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, ...
u1997's user avatar
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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, ...
Ng Ph's user avatar
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8 votes
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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 ...
Rafa's user avatar
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4 votes
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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 ...
Ceren's user avatar
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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 ...
Ceren's user avatar
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Difference between rotated frame and rotating frame

Suppose we have a spacecraft orbiting around Earth and we neglect all effects of Earth's $z$-axis motion, i.e., no wobble, precession, or nutation. For simplicity, we only assume a rotation rate $\...
Josh Pilipovsky's user avatar
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Converting J2000 to ECEF?

Say I get the orbital elements for the ISS from JPL Horizons. Say that data is expressed in J2000, an inertial frame. I want to express it in ECEF. This is a simple rotation transform. All I need is ...
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2 answers
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How to find ECI coordinates for a circular orbit

Suppose a satellite is orbiting Earth in a circular orbit, of which I know the inclination $i$, the right ascension of the ascending node $\Omega$, the semi-major axis $a$ (or orbit radius given that ...
cholo14's user avatar
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Coord. system:collection of charts (local homeomorphisms to ℝ𝑛) for differentiable manifold 𝑀, frame:section of tangent vector fiber bundle over 𝑀

This answer to Are ECI and ECEF both frames and/or coordinate systems? Is there a difference? (which asks about the difference between coordinate systems and frames) says: In the language of pure ...
uhoh's user avatar
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Space shuttle Initial ADI frame Before Switch to LVLH?

The space shuttle crew switched the ADI frame to LVLH as soon as the roll maneuver was completed. They waited for that time because the LVLH frame is in mathematical gimbal lock (singularity) when ...
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1 vote
1 answer
139 views

Which reference frame for space shuttle PEG orbital insertion?

Which frame were the space shuttle's orbital insertion attitude targets specified in? The shuttle had three frame choices: LVLH, INRTL, and REF (an inertial frame whose attitude the crew could lock in ...
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5 votes
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LVLH frame based on inertial velocity or relative (ground) velocity?

The LVLH frame is widely used in rockets during launch. The space shuttle crew used it in its attitude readings beginning very early after launch, meaning it was very reliable as soon as the rocket ...
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4 answers
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Are ECI and ECEF both frames and/or coordinate systems? Is there a difference?

I don't know really know the difference between a frame and a coordinate system. I'd proposed ECEF and ECI tags, do we need them? Frames seems to be the standard in meta but there is concern so any ...
uhoh's user avatar
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2 votes
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Satellite tracking telescope integrated program in Matlab

How can I get a comprehensive, integrated MATLAB program to set up and capture SGP4 output for telescope mounting? I am currently receiving state vectors from the SGP4 program, which include the ...
mehrdad afian's user avatar
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80 views

Why does Gravity Simulator's rendering of TESS' orbit look like a pretzel? How can I unpretzefy it?

Below is a screen shot from the amazing Gravity Simulator driven by our own @HappyKoala. If you haven't seen it recently go check it out now, then come back in 30 minutes and read the rest of my ...
uhoh's user avatar
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2 votes
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362 views

J2000 to current ECI transformation matrix

I want to find the transformation matrix that converts an ECI frame at some time 't' (lets say t = 1st January 2020) to J2000 ECI frame (that is ECI frame at noon of 1st January 2000). From what I ...
Ayush Mehta's user avatar
2 votes
0 answers
66 views

Earth's Axial Precession and Frame Change [duplicate]

Is Earth's Axial Precession and change in Axial tilt values significant enough to be considered while writing Rotation matrix that converts Body frame into ECEF frame and also while propagating Orbit ...
Ayush Mehta's user avatar
2 votes
1 answer
117 views

Could the orbit of a satellite place it on the z-axis of the ECI coordinate frame (x=y=0)?

It is mostly a hypothetical question; I assume the answer is no, but I am looking for any data to contradict my claim that there are none or at most only one satellite at a time which could ever ...
tdMJN6B2JtUe's user avatar
4 votes
1 answer
313 views

Orbit Elliptical Fitting

Question: Given a set of XYZ (3D) coordinates in the Earth-fixed frame, after converting them to the inertial frame, how do I perform orbit fitting in the least-squares sense (meaning minimising all ...
Samuel Low's user avatar
9 votes
3 answers
2k views

Building the ISS LVLH frame in ECEF/ITRF coordinates

I am trying to calculate the International Space Station (ISS) LVLH (Local-Vertical-Local-Horizontal) base vectors expressed in the ECEF/ITRF frame at a given time. The point is then to calculate the ...
Dji enne's user avatar
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2 votes
1 answer
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LVLH to ECI Conversion

I'd like to transform LVLH coordinates to ECI coordinates. I've been looking at academic papers and other answers on here and other websites and have only seen the transformation in the other ...
orbitalmechanicsnoob's user avatar
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Does the arrow in this STEREO trajectory animation point heliocentric prograde, or towards the Sun?

This answer links to the NASA GSFC page Orbits of the two STEREO spacecraft. The first video shows the two STEREO spacecraft use two and three passes by the Moon to leave Earth orbit and enter into an ...
uhoh's user avatar
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3 votes
0 answers
353 views

Computing the local orbital frame vector directions and angles of gyroscope direction in the satellite

In the context of the study of a cubesat (little satellite), I am asked to define the local orbital frame and compute the local orbital frame vector directions as a function of time (...
youpilat13's user avatar
3 votes
1 answer
296 views

Determining the spacecraft position vector with respect to ICRF frame for Venus flyby

For an interplanetary mission design to Saturn, I have considered doing multiple gravity assists starting with Venus. I am using the JPL Horizons ephemeris and ESA Lambert Solver. I have the velocity ...
Suraj's user avatar
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5 votes
1 answer
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What's the best way to understand different relative coordinate systems?

I've been reading a lot about the different coordinate systems: Topocentric (From a local observer on the surface, not the center) Geocentric (From the center of a celestial body) Perifocal (From the ...
Magic Octopus Urn's user avatar
1 vote
0 answers
432 views

How to define a body-centered ICRF/J2000 frame in SPICE?

I am trying to define a reference frame in SPICE that is Centered on a particular body, for example Mars, and with axes parallel to J2000/ICRF After going through the required reading for reference ...
user avatar
4 votes
2 answers
2k views

Conversion of GCRF to ITRF

I have to convert the $[r,v,a]$ vector from GCRF frame to the ITRF frame (and vice versa), complying with the precession, nutation and polar motion. How to calculate the ...
Leeloo's user avatar
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2 votes
1 answer
253 views

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 ...
Leeloo's user avatar
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10 votes
1 answer
2k views

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 ...
Leeloo's user avatar
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6 votes
3 answers
14k views

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 ...
Ed Rojas's user avatar
7 votes
1 answer
8k views

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 ...
Leeloo's user avatar
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2 votes
1 answer
446 views

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 ...
BeB's user avatar
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4 votes
4 answers
8k views

SGP4 TEME frame to J2000 conversion

I've got familiar with the SGP4 model. The problem which I faced is that, the results are in TEME frame. How to convert the TEME to J2000? Would be glad also, if you suggest a method in ...
Tarlan Mammadzada's user avatar
3 votes
1 answer
615 views

Satellite Positions in ICRF

For a project I need precise satellite positions in ICRF. After doing some searching I was not able to determine any online resource which provides such time series. In detail I am interested in the ...
lenxn's user avatar
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