Questions tagged [attitude-determination-and-control]

Sensors, systems, strategies, algorithms and mathematics relating to BOTH determining AND controlling the attitude (3D orientation) of spacecraft.

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Between two spacecraft, differential phase measurements are used to achieve high relative bearing accuracy. How is this done?

Based on my understanding, as spacecraft A transmits a signal to spacecraft B, multiple receivers on spacecraft B receive the signal. When spacecraft B changes its orientation, the phase differentials ...
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Does the Merlin vacuum engine on SpaceX's Falcon 9 gimbal?

SpaceX uses the Merlin Vacuum engine on the second stage of the Falcon 9 launch vehicle. Does the merlin vacuum engine gimbal or does the second stage uses only nitrogen cold gas thrusters for ...
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What do/will "quantum gyroscopes using nitro­gen-vacancy centers in diamond" for space applications actually look like, and how do they work?

The NASA page ELaNa 41 Mission has a section labeled QubeSat - University of California, Berkeley which says: QubeSat is a technology demonstration mission. It will test and character­ize the effects ...
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How the number of Sun sensors is chosen for a given spacecraft and mission?

I have to study an ADCS sensors suite and I am struggling to find a criteria to decide how many and in which directions the sun sensors shall be mounted, considering that they are coupled with star ...
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How can the proposed LUVOIR space telescope slew to different directions while keeping the sunshade in a fixed orientation? What compensates?

In this answer to Why does JWST have such a big Blind Spot? I mention that it moves as a rigid body; in order to change the direction the telescope is pointing the whole spacecraft slews, including ...
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General range of maximum RPMs used in reaction wheels in spacecraft?

I was wondering what would be the general range of RPMs used in Reaction Wheels (RW) on a satellite, and I have several closely related questions on this topic: It would definitely depend on the max ...
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How we can relate rotary inverted pendulum to a rocket system?

Initially I posted this question on EE Stack Exchange but I am also posting it here in Space Stack Exchange so I may get attention from a much related audience. I am interested in control systems ...
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Do Curiosity and Perseverance have gyrocompasses? Has any rover had one? If so, what kind and how do they work?

There is discussion of a gyrocompass in comments on the page How does Curiosity know how to point and move it's high gain antenna in real time? but so far I don't think there is a hard "Yes&...
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First hemispherical resonator used in spaceflight? First used on a deep space mission?

This answer to How exactly did Cassini provide rock-solid attitude control to enable high resolution low light imaging? (1.2 arcsec/pixel for narrow angle camera) says: Cassini was the first ...
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How exactly did Cassini provide rock-solid attitude control to enable high resolution low light imaging? (1.2 arcsec/pixel for narrow angle camera)

The extremely cool NASA JPL video Triumph at Saturn (Part I) is really worth a watch and/or listen. At about 45:45 it discusses the period after SOI (Saturn Orbit ...
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How will NEA Scout control its attitude during deep space flight & keep its camera steady without vibrations or damage to its 85 m² solar sail?

Phil Plait's Bad Astronomy's Fly Me to the Moon and Then to a Near-Earth Asteroid describes Near Earth Asteroid Scout (NEA Scout, or just Scout) a 6U cubesat that will be deployed from Artemis ...
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How (the heck) can thrusters alone stabilize New Horizons well enough to take high magnification 30 second long exposures in order to see +21 m objs?

Wikipedia's Long Range Reconnaissance Imager says that LORRI is a: ...telescope aboard the New Horizons spacecraft for imaging. LORRI has been used to image Jupiter, its moons, Pluto and its moons, ...
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What is this block of long, skinny rectangles in this New Horizons trajectory/operations simulation?

This answer to What do all these vectors point to in this New Horizons trajectory/operations simulation? begins: The software is definitely AGI's STK (notice the font and the states at the left top ...
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Did the ISS just turn upside-down? Nauka docking attitude maneuvers; did the cupola near pointing zenith and therefore show only black sky w/ stars?

This answer to Is the ISS going to yaw and assume the XPOP attitude for Nauka docking? contains lots of information on the attitude trajectory in yaw-pitch-roll space, but from those I can't envision ...
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Can a spacecraft be "too large to dock" to the ISS?

A comment below Is Starship planned to fly directly to the ISS without first stage? Is it even possible? says: to my best knowledge, the Starship will never be near the ISS. it is too large to dock ...
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Are the (relatively) new "all electric" satellite buses like the Boeing 702SP really all-electric? Are RCS and momentum unloading done with ions?

This answer to Can ion Thrusters be used for Reaction Control System? got me thinking about the new "all-electric" class of commercial satellite buses. Question: Are the (relatively) new &...
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How to reduce fuel consumption in an attitude-control PID

I've programmed a spaceship with thrusters, and an attitude control system with a PID controller for each axis. Although my spaceship movement is visually fine, my ship rotates to the target attitude ...
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Were Mariner 3 and 4 the only spacecraft to use "solar paddles" to stabilize attitude?

This one sentence nearly link-only answer to What is the principle behind Mariner 4's “Solar Pressure Vanes”? In what case(s) would they be effective? and the discussion below explain that Mariner 4 (...
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Attitude control of rockets with RD-107 engines

This question is specifically about the Soviet engine RD-107, (although it can be generalized) a version of which was clustered in Soviet rocket 8K71 which launched their "Sputnik". Each ...
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Could this three-thruster spherical spacecraft de-tumble itself with zero final velocity?

@Joshua's answer to What is the minimum number of RCS thrusters capable of stabilizing a satellite against an arbitrary rotation? begins: I know this question is old, but I randomly discovered a ...
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Why do Canopus Star Trackers track Canopus? Why not so Sirius?

Jupiter is magnitude −2.94 to −1.66 and Sirius is −1.46 and Venus stays between -3.8 and -4.8, while Canopus is only −0.74. (more negative is brighter) Question: Other than their namesake, why do ...
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Correcting Accelerometer Readings when Offset from Center of Mass: How?

A follow-up to an earlier question. So I've accepted that I need to correct my accelerometer readings for the accelerometer offset from the center of mass. The offset means that whenever the rocket ...
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Which nD accelerometer symmetric configurations on a cubical LEO spacecraft can serve as a makeshift 3D gyro resolving tumbling from tidal forces?

As they often do @DavidHammen's comment has got me thinking about the following question, which is a mathematical exercise rather than a realistic scenario. On a hypothetical large cubical spacecraft ...
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Jimsphere example data for wind speed/direction vs altitude?

I've added load relief to my thrust-vector controller (TVC) and would like to simulate it with some realistic wind data, ideally up to 80 km or higher. I know wind speed and direction would be ...
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Maximum lateral loads on space shuttle during launch?

The space shuttle TVC controller included an acceleration term which kicked in above 547 ft/s to alleviate side loads caused by wind shear, etc. The acceleration term basically allowed the shuttle to ...
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Name for PID control with acceleration term?

The space shuttle TVC controller used a PID control scheme with an acceleration term for load management at high dynamic pressures. The acceleration term would be ramped up at 547 ft/s (before max Q) ...
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Compensating for rotation when accelerometer not at center of mass?

It's dawned on me that the accelerometers of a rocket will generally not be at the center of mass. In part because the center of mass varies widely as fuel is consumed. This means the acceleration (or ...
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Space shuttle control: Holding attitude?

Suppose a space shuttle pilot pressed a button to hold the current attitude---whatever the current roll, pitch, and yaw might be. How would the attitude error be computed for use by the TVC controller?...
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Space Shuttle SRB Hydraulic Power Unit Controller Schematic: "One Shot" block, what is it?

The space shuttle SRB's Hydraulic Power Unit (HPU) provided hydraulic power to the booster's TVC system. This HPU controller schematic shows "One Shot" blocks that I'm suddenly curious ...
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Space Shuttle: What are the filters in the attitude error calculation?

Here's a schematic from the space shuttle training manuals showing how the "attitude" error signal used to drive the thrust vector controllers was determined. "Attitude" in quote ...
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When jettisoning heavy objects from the ISS e.g. 2.9 tons of batteries+, how much angular impulse does the station get? Corrective actions necessary?

Discussion below this answer to Why does it take so long for ISS garbage to fall out of orbit? addresses the jettisoning of the ~2.9 ton pallet full of used batteries full of nickel and other things. ...
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PID Control with Error Rotation Matrices?

I'm modeling a rocket with PID controllers for thrust vectoring. The PID controllers take in attitude errors as input, then output engine gimbal actuator commands. The attitude errors are individual ...
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Modeling attitude control: ramping/easing between attitude commands?

Say you switch from your current guidance program to a brand new program that commands your spacecraft to a different attitude. Assume the new attitude is a discontinuous step change from your ...
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6 votes
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RCS jet select algorithms (e.g. in space shuttle)?

I'm looking for a clear description of RCS jet selection logic. The space shuttle, for instance, had tens of RCS thrusters, only three of which would be called to fire at a time given a 3D attitude ...
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Why two engines on stage 2 of New Glenn if it's disposable?

From a controls perspective, two engines is nice, as it's the minimum required for roll control. A single engine would give you just pitch and yaw control, so you'd need a separate system just for ...
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How much do the Voyagers' attitudes drift over time? How often are their thrusters used for attitude control?

@Hobbes' answer to Voyager 1's tape recorder and other angular momentum management issues says: There are no reaction wheels on Voyager [...] Voyager is not spin-stabilized. It used thrusters for ...
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Reaction Wheels may be Worse than they Appear?

Most players of Kerbal Space Program live and die by their reaction wheels that turn electricity into momentum that allows you to point your spacecraft in any which way a lot like RCS that uses ...
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2 answers
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What causes GAIA rotational axis to precess the way it does? How exactly is this accomplished?

The GAIA spacecraft rotates at 1 degree per minute about its axis, scanning two telescopes looking 106.5 degrees apart but imaging on the same focal plane around a circle every 6 hours. The rotation ...
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Has the ISS ever "flown upside down"? Has the cupola ever "looked up"?

For a spacecraft in low Earth orbit let's call the zenith direction (vector away from Earth) "up". For most of its life I think the ISS has orbited with it's "up side" pointed &...
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What is the fastest that ParkinsonSat spun? Did it vary with solar activity?

Why would photon pressure be needed to keep ParkinsonSAT Spinning? explains that it was equipped with surfaces that resulted in a sunlight-induced torque which have ...succeeded in keeping the ...
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What is the "pendulum rocket fallacy" as it relates to analogizing a pencil balanced on a finger to maintaining attitude of a hovering rocket?

I've received comments that explain to me that the analogy between rocket attitude control during a hovering maneuver and the act of balancing pencil on the end of a finger is a helpful and good one; ...
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Falcon 9 Flipover Direction?

Consider a Falcon 9 at MECO. The rocket's close to 30 deg relative to the local horizon, down from the 90 deg it had at launch. Stage 1 separates and flips more or less 180 degrees for the return ...
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Attitude control with cold gas thrusters

Consider the cold gas thrusters on a Falcon 9. There are two thruster pods on stage 1 and two on stage 2. Each pod has four orifices to fire along the x, y, and z axes of the scacecraft. By varying ...
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Are bicomplex numbers including tessarines ever used in spaceflight (as an alternative to quaternions)?

The answer to What are quaternions and how are they used to represent spacecraft dynamics? gives us a thorough overview of the topic and is worth a good read. I saw the HNQ Why are quaternions more ...
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Earth magnetic field vector in ECEF

I've this problem... I want to express the earth magnetic field vector in ECEF reference frame. As now I've just found some models for computing these values related to the earth magnetic field: D: ...
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What was the normal function of the (coax?) crosshairs used during the Apollo 13 famous manual burn?

What crosshairs were used to maintain an attitude during the famous manual trajectory correction burn during Apollo 13's return to Earth? What was their normal function? This is all I can hear in the ...
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How exactly do "commanded delta-v burns" work in practice? (e.g. OSIRIS-REx)

Reading this answer to Could the uncertain mass of the OSIRIS-REx sample affect the trajectory of the return capsule? I infer that traditionally deep space spacecraft are sent timed commands for burns ...
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How do Falcon-9's cold gas thruster maneuvers account for the center of mass changes due to "floating fuel shifts"?

The Art of Engineering video How SpaceX Lands Rockets with Astonishing Accuracy after 07:19 explains: Cold Gas Thrusters The falcon 9 is equipped with a total of ...
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pitch, yaw and roll

Imagine a spacecraft in space, which is required to dock with other. Presume that it needs to "pitch" by X degrees, "yaw" by Y degrees, and "roll" by Z degrees (although &...
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What is the formula for the gain factor of a ferromagnetic core for a torquer coil rod?

I am an undergraduate who is currently designing an actuation system for a CubeSat, more specifically a PCB magnetorquer. (with 2 ferromagnetic core coils and one air core) I made an excel sheet that ...
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