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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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What online courses teach you hands on AOCS GNC?

I am looking for online courses that teach you "attitude and orbit determination and control systems" and "guidance navigation and control" with a focus on satellites or space ...
7perpendicularlines's user avatar
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What could cause a satellite to tumble during operation?

Detumbling is a common problem and challenge for satellite operators during Launch and Early Orbit Phase (LEOP), with a common cause being a tip-off rate induced during separation with the launch ...
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Righting JAXA's SLIM Lunar lander using RCS

The SLIM lander was supposed to roll onto the side as part of the landing process but ended flamey end up. Which has impacted the ability of the vehicle to collect solar power, and probably other ...
GremlinWranger's user avatar
2 votes
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Which affordable magnetometer to purchase?

I am involved in a CubeSat team that will fly a mission in low earth orbit. I will be working on ADCS so would like to gain experience with the magnetometer. I am just not sure which one to buy. Is ...
BeauGeste's user avatar
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Understanding and breaking down pointing requirements

“< 1 deg, 3σ total angle pointing stability” - What does the 3sigma indicate? Does this mean that 99.7% of the total pointing error (which I assume is computed via a sim), is within 1 deg? If it ...
NewEngineer839292's user avatar
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Modeling Spacecraft Jitter from Reaction Wheel Imbalances

I am working on a project trying to model a satellite's pointing error caused by jitter from the reaction wheels. I have found a couple of papers (Paper 1 and Paper 2) which implement the simple model ...
Sam's user avatar
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17 votes
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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 ...
Hans's user avatar
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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 ...
spacegr33q's user avatar
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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"...
JAK Zero's user avatar
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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 ...
Blake Fielder's user avatar
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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 ...
martina p's user avatar
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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 ...
v_space's user avatar
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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 ...
Jonathan L.'s user avatar
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1 answer
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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 ...
Jan Lynn's user avatar
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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 ...
GremlinWranger's user avatar
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403 views

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 ...
Woody's user avatar
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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 ...
Hamzalihi's user avatar
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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 ...
Merlin's user avatar
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10 votes
3 answers
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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 ...
user50224's user avatar
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2 answers
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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 ...
RC_23's user avatar
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7 votes
1 answer
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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 ...
Uwe's user avatar
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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 ...
Ashvin's user avatar
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2 votes
1 answer
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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 ...
uhoh's user avatar
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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 ...
Massimiliano's user avatar
2 votes
2 answers
319 views

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 ...
uhoh's user avatar
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2 votes
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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 ...
lqope54's user avatar
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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 ...
qwe's user avatar
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1 vote
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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&...
uhoh's user avatar
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3 votes
1 answer
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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 ...
uhoh's user avatar
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1 vote
1 answer
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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 ...
uhoh's user avatar
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3 votes
1 answer
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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 ...
uhoh's user avatar
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3 votes
1 answer
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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, ...
uhoh's user avatar
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1 vote
1 answer
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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 ...
uhoh's user avatar
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4 votes
3 answers
454 views

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 ...
uhoh's user avatar
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6 votes
0 answers
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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 ...
uhoh's user avatar
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3 votes
1 answer
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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 &...
uhoh's user avatar
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4 votes
0 answers
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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 ...
Innovine's user avatar
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5 votes
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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 (...
uhoh's user avatar
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3 votes
1 answer
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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 ...
Niranjan's user avatar
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5 votes
1 answer
361 views

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 ...
uhoh's user avatar
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29 votes
2 answers
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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 ...
uhoh's user avatar
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4 votes
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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 ...
user avatar
0 votes
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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 ...
uhoh's user avatar
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3 votes
2 answers
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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 ...
user avatar
2 votes
1 answer
186 views

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 ...
user avatar
1 vote
0 answers
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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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3 votes
1 answer
330 views

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 ...
user avatar
2 votes
0 answers
55 views

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?...
user avatar
1 vote
1 answer
157 views

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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4 votes
0 answers
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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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