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Questions tagged [adcs]

Attitude Determination & Control Systems measure the attitude of a spacecraft and often execute measures to adjust the attitude with respect to the celestial sphere, reference bodies, or other spacecraft. They can be active including computations, or passive.

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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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Why does Orion's Jettison Motor, have four nozzles but eight Attitude Control Motors arranged in an octagon?

Spaceflight 101's Orion Spacecraft Overview shows the following tests for the escape system. Why are there eight ACS thrusters arranged octagonally? Is it just to reduce cosine losses or does this ...
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Did NASA tell the Skylab astronauts to “Stop running around!”?

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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How do we manage the residual magnetic moment of magnetorquer with a ferromagnetic core?

I'm currently working on a control algorithm, specifically in detumbling, for a 3U cubesat. I'm using magnetorquers for actuation and magnetometers to receive feedback. If I have no current passing ...
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Help with my tensor tension; how to derive and calculate this rigid body gravity gradient torque?

Tensors make me tense. Imagine a long thin rod in a circular orbit. The gravity gradient will produce a net torque on the rod whenever it is not oriented parallel, or perpendicular to the radius ...
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Help with Scott Manley's rigid body dynamics narration

I've just watched Scott Manley's video SpaceX's Water Landing Reveals Rocket "Secrets" (or, What We Learned from CRS-16) (again) and there's some rigid body dynamics in there where I'm not sure I am ...
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What are damper booms and how did they facilitate triaxial stabilization?

I'd never heard of DODGE until I saw it mentioned this answer as the source of the first full color "full Earth" image. The spacecraft's primary function however was to experiment with gravity ...
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How do Mars spacecraft control attitude on final descent and landing?

When I watch videos of probes landing on Mars after cutting the parachutes off, they show the lander doing final orientation adjustments before touching down. The engines don't seem to have a ...
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During its final descent, how will the InSight lander know cardinal directions in order to land with proper orientation?

As explained in @karthikeyan's answer the InSight lander will rely upon its landing system to orient the lander properly, so that once on the ground instruments such as the RISE antennas will be ...
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How are Voyager's 16 thrusters oriented?

@RussellBorogove's excellent answer to the question How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters? describes the locations and usage patterns of the 16 ...
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How did the X-15 control attitude above the Kármán line?

This interesting, archived page https://www.webcitation.org/618QHms8h?url=http://www.fai.org/astronautics/100km.asp which I found in this answer, says: In the early 1960´s, the U.S. X-15 Aircraft ...
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Does the Soyuz spacecraft really try to achieve attitude accuracy of 0.5° from GLONASS and GPS signals?

This answer mentions that the Wikipedia article Soyuz MS (Союз МС, the latest revision of the Soyuz spacecraft, evolution of the Soyuz TMA-M) says: Instead of relying on ground stations for orbital ...
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Current status of the use of GPS mutli-antenna time differentials for satellite attitude determination?

I am certain that I read a year or three ago about an unmanned satellite that was going to be testing a method of attitude determination that relied upon two (or more) separate antennas on one ...
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Hubble's one-gyro mode; how does it work for attitude control, stabilization, and slewing?

Space.com's Hubble Space Telescope Apparently in 'Safe Mode' After Gyroscope Failure says: "It’s true. Very stressful weekend. Right now HST is in safe mode while we figure out what to do. Another ...
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Has a spacecraft ever used a four gimbal gyroscope? Did Michael Collins get his Christmas wish?

The question Did Michael Collins ask for a fourth gimbal for Christmas? Is there a recording or transcript? mentions that Apollo 11 Command Module Pilot Michael Collins is said to have asked for a ...
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How can articulated spacecraft components increase the risk of gimbal lock?

This answer has got me baffled. In theory, yes. In practice, no. The problem is gimbal lock... There seems to be some risk of inducing gimbal lock if a spacecraft component of sufficient mass is ...
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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 principle behind Mariner 4's “Solar Pressure Vanes”? In what case(s) would they be effective?

The image below, found in this answer shows four "Solar Pressure Vanes" on Mariner 4. I've never heard of such a thing. I can imagine that it might have been thought to help favor the spacecraft's ...
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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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What is a gyrocompass and how might one be be used by a planetary rover?

In comments and links therein below the question How does Curiosity know how to point and move it's high gain antenna in real time? there is mention of a gyrocompass. I am aware that gyros can be ...
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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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Tradeoffs using a battery/motor/gyro versus tangential thrusters to spin a spherical shell in space?

Using the Humanity Star (see this answer for example for background/context), consider two possibilities for spinning a small spherical shell at a low rate, say perhaps in the neighborhood of 2 to 10 ...
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What is Rocket Lab's new Curie “Kick Stage”?

This reddit points to Rocket Lab's news page Rocket Lab successfully circularizes orbit with new Electron kick stage. It is named Curie, presumably after Marie? According to the Rocket Lab's article: ...
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Initial condition for SGP4 in satellites without GPS, before the uplink of TLE data

I believe that the SGP4 model for orbit estimation for LEO satellites uses TLE data as initial condition. Some CubeSats chose to use up-link TLE data than installing GPS. My question is for the case ...
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Effect of permanent magnet and solid core magnetorquer on magnetometer reading

Permanent magnet as passive stabilization and magnetorquer with solid core as active stabilization has been used over the year in satellites.But the would have magnetic field lines, wouldn't they ...
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How will GomX-4B manage angular momentum when using butane thrusters to move?

Phys.org's ESA's next satellite propelled by butane describes GomX-4B's butane powered cold gas thrusters, and how it will test them and use them to navigate to different distances from its partner ...
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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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Placement of Reaction Wheels in a nano satellite

The reaction wheels rotate the satellite only about the centre of mass.If the reaction wheels are not placed about the principal axes,Will the amount of torque produced be the same as when they are ...
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How does JAXA's “Int-Ball” manage airflow to optimally navigate inside the ISS?

above: From the BBC's Japan's zero-gravity space drone sends first pictures from ISS. This is JAXA's GEM internal ball camera, or "Int-Ball". Kawaii! It looks like it uses a three axis attitude ...
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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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Controller to reaction wheel interface

A typical controller generally gives control torques which should be applied about the axis of a satellite. How exactly is this torque applied using a reaction wheel? For example if control torques ...
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How well can the ISS attitude control system detect periods of astronaut activity?

The question Why doesn't ISS start to spin if people walk inside? is a good one partly because it has attracted several good, informative answers. One of them is particularly intriguing because it ...
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How do rate gyros measure yaw, roll and pitch rates?

I need some help in understanding how rate gyros are used for measuring rotation rates about the yaw, roll, and pitch directions. Suppose a gyro is used for measuring roll rate. How should the spin ...
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Why are the ISS attitude values shown on these two web sites so different?

Here are screen captures from two sites that seem to be showing approximately live - or at least changing - telemetry from the ISS. They both say the spacecraft attitude is shown in degrees. Looking ...
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Could the ISS stop rotating wrt the stars for a few days, then start again?

Suppose for some reason it was particularly advantageous to stop the ISS from rotating once per orbit, so that it maintained a constant attitude with respect to the stars (or the Sun) instead of with ...
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How well could the tether tension method of attitude control actually ultimately work for a cubesat system?

The phys.org new item Image: Small satellite deployed from the Space Station shows the cubesat craft Space Tethered Autonomous Robotic Satellite (STARS-C) being deployed from the ISS. A satellite ...
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Why are some reaction wheels sealed with low pressure gas, others with vacuum?

This answer and this answer address the question Do reaction wheels generally run in vacuum, or are they pressurized? Sealed or vented? and they both mention that sometimes momentum wheels are sealed ...
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Do reaction wheels generally run in vacuum, or are they pressurized? Sealed or vented?

Is there some general trend for the operating pressure of reaction wheels? I can imagine low to no pressure has obvious advantages of low to no drag (more drag requiring more power, beyond that ...
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Can gyroscopic stabilization be done without any rotating parts?

In the video linked in this answer the spacecraft is said to be "gyroscopically balanced" (at about 00:20). I'm going to ask about the terminology associated with the phrase "gyroscopic ...
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Does the way this experimental kill vehicle moves and thrusts suggest it contains inertia wheels?

This comment below this answer about 'spacecraft' or at least 'craft' that can maneuver near the surface of low gravity bodies links to this video about Lockeed Martin's Multiple Kill Vehicle. If I ...