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 were the relative orientations of the Hubble Space Telescope's three star cameras, six rate gyros and four reaction wheels optimized for exactly?

Table 3. in paper Hubble Space Telescope Reduced-Gyro Control Law Design, Implementation and On-Orbit Performance; AAS 08-278 found in @OrganicMarble's answer seems to give the unit vectors where the ...
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Why do these two Hubble Space Telescope star cameras point in nearly the same direction, and what's the other window for?

The article in Forbes Former Astronauts Share Ways To Cope With Social Distancing & Isolation includes the following image of the Hubble Space Telescope. Question: I believe that those three ...
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How was DSCOVR “fixed” so that sufficiently dynamic attitude determination is gotten from star cameras?

The following from Space News indicate that a laser gyroscope failed and that software changes were developed and uploaded to the spacecraft bringing it back on line again recently: Software fix ...
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Control torque to a Reaction wheel that compensates for friction - need help understanding a working code

Reaction wheel in a s/c is driven by controller torque. However, since there is friction torque in RW, less than the reqd momentum change is achieved. Hence the control torque must be increased by ...
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What attitudes will Starlink satellites have in different orbits?

I'd like to simulate the visibility of the tens of thousands of satellites on Earth based on descriptions of the distribution of orbits and their segments illuminated by the Sun visible to locations ...
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Can we go anywhere in space with only THREE reaction wheels and ONE chemical thruster?

I had a discussion the other day with some of my peers and they were very keen on the fact the it is possible to change your orbit as desired using a single thruster and a three reaction wheels. The ...
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119 views

Can reaction wheels be used for detumbling?

During orbit insertion, the satellite can start with a high tip-off rate which requires detumbling. From what I have read, detumbling is usually done using magnetorquers. I was wondering if ...
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Does the “Tennis Racket Theorem” apply to the ISS? Does it rotate around its intermediate (unstable) axis?

Wikipedia's Tennis racket theorem begins: The tennis racket theorem or intermediate axis theorem is a result in classical mechanics describing the movement of a rigid body with three distinct ...
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How hard was it for the Shuttle to perform attitude control for the entire ISS? Did they have to calibrate?

This answer to the question How was the Space Shuttle Orbiter used for ISS Reboost? describes a procedure I never knew happened. When the shuttle was docked to the ISS it sometimes used its rear ...
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Why did Cassini have reaction wheels but Galileo, Juno and New Horizons don't?

Three gas giant planet orbiters are mentioned in this answer: Cassini - Uses Reaction Wheels and thrusters Galileo - Primarily managed via spinning the spacecraft and thrusters. Juno - Just ...
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Have magnetotorquers ever been used to spin-up a satellite?

Magnetotorquers are often used for momentum dumping of reaction wheels in smallsats, and they can use them as well for attitude control directly, per answers to Are there any modern cubesats or ...
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Are there any modern cubesats or smallsats that have relied only on magnetotorquers for attitude control?

This comment got me thinking... Question: Are there any modern cubesats or smallsats that have relied only on magnetotorquers for attitude control, sans reaction wheels or thrusters? Ideally an ...
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How does one impulsively null spacecraft nutation?

The Scott Manley video The Only Pilot to Shoot Down A Spacecraft - A Space Ace talks about the ASM-135 ASAT and its successful test launched from an F-15. He shows images from the page The F-15 ASAT ...
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Puzzler: which Apollo 8 astronaut would have been positioned furthest sunwards 20 minutes after lunar insertion?

This Classic @DavidHammen answer to the question Who has been the closest to/furthest from the Sun? says: This bodes well for an Apollo astronaut being the person closest to the Sun, but bodes ill ...
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How could Earth's magnetic field be used to determine a cubesat's attitude in LEO?

After reading this answer I thought that I'd read about a smallsat that used magnetometers to measure the Earth's magnetic field direction and magnitude along with a model for Earth's field and some ...
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Spacecrafts: NED frame to Orbit Frame or Body Frame Transformation

I calculate the geomagnetic field using IGRF model in Matlab. However, the output is in the NED coordinate frame and I want to tranform it into the Body frame. I've searched everywhere and I cannot ...
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How “hard” did Apollo 12 turn left just before it landed?

This answer to How much were the LMs maneuvered to their landing points? includes Figure 34 from Floyd Bennett's 1972 Apollo Experience Report - Mission Planning for Lunar Descent and Ascent; NASA TN ...
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What are “uncoupled attitude maneuvers” and why do them?

This answer to the question Apollo-11 delta-v “due to residual pressure in the docking tunnel pushing the spacecraft apart” detected as it happened? Was it corrected? quotes the following passage from ...
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What does it mean when the Voyagers “switch thrusters”?

The Gizmodo article NASA fights to keep the Voyager probes running after four decades says: As another example of the probes' need to adapt to circumstances to keep going, Voyager 2 has fired up ...
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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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What are Starlink's available momentum unloading strategies?

Today's Teslarati article SpaceX wants to offer Starlink internet to consumers after just six launches talks about the new website https://www.starlink.com/ shows several images from it, and tries to ...
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Are new precision gyroscopes used in spaceflight pretty much all optical?

Gyroscopes are used in spaceflight as parts of inertial systems to monitor spacecraft attitude. They are not absolute, they will drift slowly over time and so need occasional calibration via other ...
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Satellite mission design/performance requirements to attitude/orbit control design specifications

Are there any good sources that discuss: the steps involved in deriving attitude/orbit control design specifications, from satellite mission design/performance requirements?
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How are New Shepard's tilting fins and gimbaling nozzle used together (or separately) to control the rocket?

In the beginning of the video Blue Origin New Shepard self-landing rocket launch with 38 research payloads (5/2/2019) the announcer mentions that both the tilting fins and the BE-3 engine nozzle ...
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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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Maintenance manouvers for a Dawn-Dusk SSO?

I'm in charge of the ADCS for a class project, which consists on a 25U-cubesat, in a 650-km dawn-dusk Sun-synchronous orbit or SSO. What are the orbit correction/maintenance manouvers a spacecraft ...
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Flat-spin transition manoeuvre: why is the angular momentum not constant?

In an article by Rahn and Barba, in which a flat-spin transition manoeuvre is investigated, the following figure is presented: I'm trying to reproduce this figure by integrating the following coupled ...
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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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146 views

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 do 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 final descent how will InSight 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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381 views

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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280 views

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 algorithms. I have been using a 9 Dof strap-down IMU on human and land vehicles for these algorithms. I Would be interested to test my algorithms with IMU data ...
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What is a gyrocompass and how might one 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: ...