Questions tagged [attitude]

Questions on ascertaining, predicting, and controlling spatial orientation and rotation of spacecraft, and on forces that affect spatial orientation.

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RTN to ECI conversion of acceleration

The problem I am working is one of orbit determination. I am adding some virtual accelerations to a an Earth centered LEO satellite in the RTN frame, which is attached to the satellites' center of ...
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PIR application as a sun sensor

Is there any history or merit to using a PIR (Pyroelectric ("Passive") InfraRed Sensor) as a sun sensor for determining the attitude or position of a Satellite?
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How accurately can you determine time from planetary/star positions?

I was reading this question which has to deal with the accuracy of on-board atomic clocks. In the question it mentions multiple times that only recently did we start including accurate enough clocks ...
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How often do reaction wheels require desaturation, normally?

I'm sure the answer to this question is, "it depends" but I'm hoping for a ballpark number here. Let's assume you design a smallish satellite to point at the earth while orbiting. You have the ...
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ECI to LVLH transformation [duplicate]

I am working on a transformation of ECI coordinates to LVLH (Local Vertical Local Horizontal) coordinates in order to calculate satellite maneuvers. Does anybody know how should I approach the problem?...
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Is the gyroscopic effect created by high rpm turbo-pumps an issue for rocket attitude control?

Is the gyro effect taken into consideration in the control strategy or is it somehow mitigated?
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What fractions of the time did Skylab spend in Earth-oriented and Sun-oriented attitudes?

The Introduction section of NASA Technical Memo TM-X-64628 Angular momentum desaturation for Skylab using gravity gradient torques begins: The Skylab Apollo Telescope Mount (ATM) experiments ...
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Could the Voyager spacecraft be spin-stabilized to keep their high gain antennas pointing towards the Sun (and therefore Earth)?

A suggestion has been made that the Voyagers may run out of propellant and so may not be able to maintain pointing near the Earth for communications. According to @BowlOfRed's answer: Although the ...
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How many times would two astronauts have to run around Skylab to turn it by 10 arc minutes?

This answer to the question starts with: This video may help to answer your question. Starting at about 00:24, you can see an astronaut running around the "exercise wheel" of Skylab (an early NASA ...
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What type of Kalman filters are preferred for satellite ADCS systems; what are the tradeoffs?

Are Unscented Extended Kalman filters (UEKF) preferred over Multiplicative Extended Kalman filters (MEKF) in satellite ADCS systems? What are the trade-offs for these two filters? I have read that ...
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How does gravity-gradient stabilization work?

I understand there is a stabilizing force due to gravity gradient. What I'm unsure about is the stabilization part. How does it work? It looks like to me that this tidal force would just make the ...
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When reading “the writing on the wall” in the ISS, which way is up?

This answer to the question Is there really no difference between up and down in ISS? says: ISS does have a sort of 'up and down', deliberately created as part of the design. All the modules ...
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Could you use magnets to orient in space?

If I had a tiny satellite with a magnet orbiting Earth (or another body with a magnetic field), could I use this magnet to adjust my attitude? I'm thinking it could be used in sort of the same way as ...
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Falcon 9: engines stabilize spin

On CRS-16, the landing Falcon 9 booster entered a spin rotation due to a stalling grid fin hydraulic pump. According to Musk, the engines stabilized the spin. How is this possible? The main engines ...
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ITAR regulation on reaction wheels

I'm performing a design exercise for the design of attitude control system using reaction wheels as control actuators. During the analysis, I noticed few interesting options from suppliers in the US. ...
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131 views

Algorithm for minimum thruster usage to control three axes

In order to control 3 axes, the spacecraft has 4 thrusters. These thruster's torques can divide the space around the spacecraft into four regions. Consequently, by eliminating one of the thrusters, we ...
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What's the sudden pitching of Rocket Lab's It's Business Time launch at separation?

In today's Rocket Lab launch of the It's Business Time mission, there was a substantial and swift change in attitude upon stage separation. It looks scary. I understand that The first stage of a ...
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Why would someone use Modified Rodrigues Parameters over Quaternions for spacecraft attitude estimation? And vice versa?

I see quite some papers on spacecraft attitude determination and control, that rely on quaternions. While some others rely on MRPs. The advantage that I see so far is that... for quaternions, the ...
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Typical 1U CubeSat Detumbling time determination using passive control?

I would like to be able to estimate roughly how long it takes for a 1U cubesat using a permanent magnet for passive control to detumble after the deployment at about 550 km. Assuming there is some ...
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How can gimbal lock occur with three perpendicular reaction wheels?

I understand how gimbal lock is a serious risk in case of CNG where the axis of rotation change in operation, and as they become coplanar you lose degrees of freedom, the respective axis duplicating ...
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Are robot arms ever used for attitude control in space?

Motion of a robotic arm mounted on a spacecraft presents an interesting challenge from a control perspective. A robot arm, such as Canadarm (space shuttle) and Canadarm2 (ISS), has significant mass ...
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Attitude control systems with only reaction wheels

With reaction wheels it is common to use actuators such as Thrusters and magnetorquers, to account for the saturation of the reaction wheels due to secular/non-cyclic disturbances. However, these ...
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Verify solar radiation torques on a satellite

I'm creating a design support system for Attitude control design of a spacecraft. For the attitude simulator, I have made a function to compute the solar radiation torque acting on the satellite which ...
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What is the Lux value of the Sun and Earth in Low Earth Orbit (altitude=400 km)?

I'm the Attitude Control System team lead on a cube satellite project, and we're trying to use cheap lux sensors to determine the body sun vector (vector adding the lux from each sensor). I want to ...
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Falcon fairing half - between separation and parachutes deployment

How does Falcon fairing half behaves in atmosphere before parachutes deployment? What is its free fall attitude in atmosphere? Is the fairing's attitude stable (with some wobbling, but without ...
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What sensors or combination of sensors do rockets use during takeoff for their orientation?

I know that after using up rockets and before reaching final orbit, satellites use Earth, Sun, Star trackers to find the absolute position depending on the application and orbit. After that, they use ...
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What attitude have past and modern manned spacecraft maintain(ed) relative to Earth?

I hope this question is not too broad. It is inspired by another question. We know that ISS keeps its nadir pointing to Earth's surface. What about other manned spacecraft? Do/did they have ...
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Have any vehicles used asymmetrically variable thrust for active stabilisation? [duplicate]

Have there been any tests or attempts at developing a propulsion system that uses variable thrust for attitude control (particularly during launch)? Conventional systems often use fully gimballed ...
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Attitude requirements for inter-satellite laser communication

Previous questions have address the beam divergence angles and the expected signal attenuation for laser communication between spacecraft. However, I was wondering what is a typical receiver aperture ...
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What is the difference between dual-spin spacecraft and hybrid(attitude control) spacecraft?

The definition from this source is "Two classes of spacecraft bring together the advantages of having momentum bias and yet provide a non-spinning base for accommodation of payload elements and ...
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What is a non-propulsive vent?

I just hear the term "non-propulsive vent". Is it a thing, a vent that does not cause propulsion? Or is it an event, where a vent of some unwanted gas has occurred which did not result in a ...
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Spacecraft Horizon Sensors for Lunar orbit

Recall that "traditional" horizon sensors for Earth missions utilize the IR wavelength regime since this can reveal a good contrast between the cold space and the warm Earth-limb edge. If we were to ...
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Spacecraft Inertial Data

I am a developer of motion analytics algorithm. Having been using a 9 Dof IMU strap-down onto human and land vehicles for this algorithm. Would be interested to run my algorithm of a spacecraft IMU ...
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Atomic (Quantum) Inertial Sensor

In relation to the question I was looking for the perfect sensor that would help me achieve perfect non rotating spacecraft. My search made me look for exotic phenomenon that can be utilized for such ...
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Using what technology one can keep a spacecraft truly non rotating

Inspired by the question I thought maybe a photon thruster can be used for precisely giving thrust to maintain spacecraft attitude. But soon I realized that for high precision attitude control, one ...
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Attitude and orbit thrusters catalog

Typically, when trying to adjust simulation parameters (of orbit control, attitude control...) to real world values in order to validate algorithms with comparisons with past and current mission ...
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Angled thrusters on the Soyuz 2.1a?

I saw a satellite launch recently (launch link) which used the Soyuz 2.1a rocket. Shortly after the launch I observed 4 symmetrical thrusters at an angle to the main thrust line. Is this for ...
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Can you turn in space without propulsion?

Say an astronaut is floating perfectly still inside their spaceship. Can they rotate themselves by stretching out their arms and twisting one way, then pulling in their arms to their sides and ...
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Finding reference quaternion of a satellite in orbit

How can i find the reference quaternion of a satellite after it has detumbled? I need the quaternion to be able to successfully actuate my payload, which in this case will be a hyperspectral imaging ...
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Change a Spacecraft's attitude from 3 - axis stabilised to spin stabilised?

I am essentially trying to "spin up" a s/c, so it spins about 1 axis at a known spin - rate. I then need to figure out how much time it will take to do that, and how much force required (which I ...
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Did Tiangong-1 turn the engines on?

The following graph shows the Tiangong-1 radius vector at the perigee, semi-major axis and apogee (scaled to 6371 km just to show an approximate altitude) and its orbit eccentricity: I used the SGP4 ...
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Initial attitude determination after deployment

Suppose that I am launching a cubesat into space. Let the cubesat be launched from the P-POD deployer. Since the satellite will have a huge velocity, hence the detumbling mode will be operating. As ...
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Inexplicable Offset in Satellite Laser Ranging (SLR) observations

I am struggling with the implementation of a Satellite Laser Ranging (SLR) validation tool. The situation is as follows: I am provided with a framework which gives me the position of a SLR ...
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How does Voyager 1 keep track of its orientation?

With the Voyager 1 attitude correction all over the news (related: How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters?), I wonder with what instrument such ...
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How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters?

There are several popular news items about the recent test of Voyager 1's Trajectory Control Thrusters to see if they can be used for attitude control to facilitate communication with Earth. The ...
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In what circumstance would it be useful for a satellite’s angular velocity to differ from its reference frame’s angular velocity?

Casually reading “orbital mechanics for engineering students” on rigid body attitude dynamics, i see the following passage: $$M_{net}=\dot{H}_{rel} + \Omega\times H$$ Keep in mind that, whereas $\...
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Did any rockets use differential throttling instead of gimbal?

It seems the standard approach to control of rockets during launch is either vernier thrusters, or gimbals on the main engines. Sure that works, and is quite efficient, but I wonder about a simpler ...
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Would Mayak's large solar reflector have produced a stable attitude, or more likely start tumbling or rotating?

update: Answers to Two week mark; has Mayak (Маяк) been spotted yet? Reflector deployed? Astronomy “ruined”? indicate that the reflector did not deploy successfully (more at Mayak, a magnitude -10 (...
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Xenon vs Hydrazine, “Should I Stay or Should I go?” Dawn mission decisions

edit 2: There seems to have been some announcement/extension by NASA (20-Oct-2017), possibly this will shed more light on the issues in this question. edit 1: Several months have passed since this ...
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Does the Hubble telescope use a “simple” PID-controller for its pointing control system?

I am wondering whether the Hubble Space Telescope uses a "simple" PID controller like this: Or is it using another type of control system that may be much more complex?