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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Why does the Psyche Spacecraft use cold gas thrusters?
In a recent article on SpaceNews they write
[There exist] nitrogen cold-gas thrusters that orient the spacecraft.
This seems like an odd choice for me, considering it is a multi year mission that ...
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How often does a CubeSat leverage its ADCS?
I'm wondering how often an Earth observation-focused CubeSat (6U - 27U) would leverage its onboard Attitude Determination and Control System (ADCS).
Would it be employing its ADCS to optimize every ...
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What does "reaction" in "reaction control system" and "reaction wheel" refer to?
I have a basic understanding of how RCS and reaction wheels work, but I can't figure out what "reaction" refers to in their names.
Is it referring to how a craft's attitude "reacts"...
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How to "turn off" ADCS system to monitor orientation after firing MDT's?
I've been tasked in a hypothetical mission of determining if an Attitude Determination and Control System (ADACS) can be "turned off" during MEMS Digital Thruster (MDT) firings so that the ...
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How to select the right magnetic torquers to desaturate a wheel?
I want to select actuators for a micro-satellite (around 40 kg) orbiting in LEO.
I proceeded in calculating the maximum disturbance torques that affect my spacecraft and selecting proper reaction ...
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Understanding the difference between pointing knowledge, pointing accuracy and pointing stability?
In terms of specifications for satellite Attitude Determination And Control System (ADCS) hardware, my understanding is that pointing knowledge is for attitude determination, whereas pointing accuracy ...
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Inserting optical elements into a ring laser gyroscope to sense all three axes
Ring laser gyroscopes (RLGs) leverage the physics of ring laser interferometers and the Sagnac effect to sense rotation in a single plane. My understanding of RLGs is that they are independent systems ...
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Need advice to set up reaction wheel cluster in lab
I am thinking of having a reaction wheel cluster set up in a physics lab for educational purposes. I would like to find out what the available options to me are. Here are some more specifics:
I see ...
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What guidance algorithm does Falcon 9 use during powered descent and landing?
The SpaceX Falcon 9 does a powered touchdown with a rocket thrust higher than mass, so is not able to establish a low altitude hover and final descent as used by the Apollo lander. Instead it needs to ...
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How accurate is the TLE which is generated by STK?
Generating TLE data using STK through the Trajectory Sampling method of 1 day with a time step of 60 seconds. How to increase the accuracy?
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What is the minimum number of thrusters required to control attitude, propulsion and spin?
What is the minimum number of thrusters required to control attitude, propulsion and spin?
The first part of this problem (attitude) was asked in What is the minimum number of RCS thrusters capable of ...
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How do I simulate a magnetometer and get an attitude?
I consider that I have a single magnetometer (i don't know if I need more), how can I model that sensor? This was my idea:
Consider a random unit length vector $\textbf{m}$ which is the magnetic field ...
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Rotation and orientation of James Webb's mirror from ground stations
There are definitely pre-determined plans in the agenda of the James Webb telescope to take images from the universe, but if there is a need for any reason (intentional or emergency) to change the ...
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Attitude determination during launch and landing
Rockets contain accelerometers and gyroscopes to measure changes in velocity and angular rates.
Gyroscopes detect changes of the orientation in space (=attitude). You can integrate these changes to ...
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Gyros for long term attitude control
James Webb telescope is limited to a 10 year service life by its fuel, as I understand it.
While propellant would be required to translate the craft for orbital maneuvering, could pure attitude ...
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What is wrong with Voyager 1 attitude data telemetry? Is there a test version of the computer available?
There is a problem with Voyager attitude data telemetry.
While the spacecraft continues to return science data and otherwise
operate as normal, the mission team is searching for the source of a
...
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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 ...
user39728
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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 ...
user39728
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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) ...
user39728
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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 ...
user39728
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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?...
user39728
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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 ...
user39728
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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 ...
user39728
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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 ...
user39728
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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 ...
user39728
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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 ...
user39728
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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 ...
user39728