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Questions tagged [navigation]

Topics that relate to orbit determination and flight path control. May also be used for navigation on the surface of celestial objects.

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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
2 votes
1 answer
51 views

Satellite Navigation: Measuring Velocity & Position

How is the position and velocity of a satellite measured from ground? Radar measurements could give us range and range rate which are scalar quantities (if I understand this correctly). But how could ...
G11's user avatar
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What are the likely issues and challenges in developing LTC: Coordinated Lunar Time?

In April of 2024, the US White House directed NASA to define a workable definition and operational plan for LTC: Coordinated Lunar Time. White House directs NASA to create time standard for the moon | ...
nealmcb's user avatar
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How long can inertial only navigation systems maintain landing accuracy in LEO?

Inspired by this question, pre GPS all space craft used inertial navigation with periodic fixes from the ground. Inertial systems will drift with time, so the longer between last fix and landing the ...
GremlinWranger's user avatar
6 votes
2 answers
167 views

How do modern space capsules ascertain their position during the communication blackout phase of reentry?

In this video recording of Orion's reentry, you can hear and see the RCS thrusters firing during the communication blackout phase. During the communication blackout, I would assume that GPS would not ...
phil1008's user avatar
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2 votes
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316 views

Why does NASA suit color coding not follow conventional navigation color coding?

Pictures of NASA spacesuits like the ones below of Neil Armstrong’s Apollo suit (from the Smithsonian) and Gemini suit usually show the right wrist connection red and the left blue. Color coding for ...
Woody's user avatar
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4 votes
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How do Inertial Navigation Systems compensate for their inability to measure gravitational acceleration?

Inertial Navigation Systems calculate position by measuring acceleration. But they are unable to measure gravitational acceleration since gravity always acts equally on the test mass and the ...
Woody's user avatar
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11 votes
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372 views

Using today's technology, is interstellar navigation possible?

I was watching this video essay discussion about space elevators, and on a bit of a tangent, the physicist talks about difficulties with interstellar missions, specifically comments about navigation ...
Dragongeek's user avatar
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Is there an authoritative source for which GNSS satellite transmits which signals?

I'm trying to algorithmically predict which signals from which GNSS satellites could be heard by a ground-based receiver (without actually looking at the recieved data; the idea is to be able to also ...
Martin Pecka's user avatar
2 votes
1 answer
205 views

How does JUICE navigate autonomously

Introduction To kick things off, I'd like to introduce myself as a 23-year-old novice learner when it comes to space exploration but I've been listening to astronomy-specific podcasts since 2022 and I'...
Navid's user avatar
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Hohmann Transfer - Adaptive Guidance Law

Is there an equivalent adaptive guidance law for the Hohmann transfer as there is with the initial ascent profile for a rocket launch (e.g. Powered Explicit Guidance)? This is for a personal project - ...
user49768's user avatar
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Guidance and control inputs in autonomous satellites

I would like to know which are the standard navigation data available on a small satellite (in LEO). In particular, I'm trying to understand which inputs I should consider for the Guidance&Control ...
Chicca's user avatar
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What was the function of the Apollo Sextant Beam Splitter?

Operation of the Apollo Sextant Beam Splitter The Apollo optical Sextant is used to update the vehicles State Vector. It is capable of sighting two celestial targets simultaneously and measuring the ...
T.A. Neal's user avatar
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Dilution of precision in different coordinates

Given the ranges $\rho^{(s)}_{R_x}=\sqrt{(x_{R_x}-X^{(s)})^2+(y_{R_x}-Y^{(s)})^2+(z_{R_x}-Z^{(s)})^2}$ between a receiver $R_x$ and an $s$-th satellite, where $s=1, 2, ... n$, one can construct the ...
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Which is more accurate, a Saturn V IU or an iPhone?

In a comment, I mentioned that a modern cell phone could do almost everything the Saturn V instrument unit could do. How true is that? In particular, which would provide more accurate data for an ...
Mark's user avatar
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4 votes
2 answers
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Apollo REFSMMAT components

In the snip above, under (b) Definition of REFSMMAT, there is a 3x3 Matrix depicted. Under (c) REFSMMAT Components, a list of the value of each of the 9 components of the 3x3 Matrix using Unit Vectors ...
T.A. Neal's user avatar
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Spacecraft localization beyond Earth orbit

How does a spacecraft localize itself after leaving earth orbit? In robotics you can either use known broadcasting information or do real-time position tracking(some type of SLAM) but I suspect that ...
FourierFlux's user avatar
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Why might Ingenuity be able to fly faster when it flies higher?

A 2022 March 15 NASA press release says: A recent software change already on the rotorcraft frees Ingenuity from its previously programmed maximum altitude of 50 feet (15 meters). The altitude gains ...
Camille Goudeseune's user avatar
2 votes
2 answers
84 views

Which is more accurate, the ellipsoidal height from SLR or GNSS?

Satellite Laser Ranging (SLR) and Global Navigation Satellite System (GNSS) both measure the ellipsoidal heights. Which measurement of ellipsoidal height is more accurate?
Astrolien's user avatar
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Precise Orbit Determination (POD) vs GNSS accuracy; seeking references

Precise orbit determination provides performances that are not currently achievable with GNSS systems. I cannot find information of the reason for this. I imagine different possibilities: Use of ...
AUP's user avatar
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Could Apollo's Sextant navigation use similar geometry as Marine Navigation?

Could Apollo's Sextant navigation for Cislunar Celestial Navigation use similar geometry as Marine Navigation? My grandfather would be familiar with the instrument in this astronaut’s hands, although ...
Woody's user avatar
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28 votes
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How will DART be able to hit a 170 meter rock dead-center at over 6000 m/s? What technologies will be use and how will they work together?

The DART spacecraft will ultimately be a kinetic energy impactor, using its 500 kg mass at a relative velocity of over 6000 m/s to slightly change its target 65803 Didymos's companion Dimorphos's ...
uhoh's user avatar
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5 votes
1 answer
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Just how preferable are afternoons for flying Ingenuity? Why?

JPL tweet links to mars.nasa.gov's Flying on Mars Is Getting Harder and Harder which explains that seasonal changes are lowering the density of the local atmosphere, presumably due to warmer seasonal ...
uhoh's user avatar
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1 answer
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Measurements processing order impact in Kalman filter

In sequential Kalman filters the measurements are processed as scalars one after the other. The sequence is somewhat: Compute innovation Compute Kalman gain (I consider for simplification a linear ...
AUP's user avatar
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7 votes
1 answer
219 views

Have various lunar rovers known their own position on the Moon? If so, how?

Given that there is no satellite navigation on the Moon, have lunar rovers figured out their current location on the surface of the Moon? If so, how? For the ones that have, did they send pictures ...
Bensas's user avatar
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1 answer
162 views

Lunar satellite navigation system

Inspired by some questions: Are People Actually Serious About Mining The Moon? How to estimate that receiving GNSS signals Earth while orbiting the Moon will still provide locations to about 200 ...
Fred's user avatar
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5 votes
1 answer
415 views

How is altitude measured in self-landing rocket stages?

Altitude must be a key metric for a self-landing rocket stage on landing approach. But where exactly does that measurement come from? And to what decimal place would it be accurate? I'm sure the ...
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19 votes
1 answer
1k views

Lunar Terrain Model in Apollo Guidance Computer

In the book Apollo Guidance Computer by Frank O’ Brian, on page 279, he talks about the lunar terrain model in the Apollo Guidance Computer, which has the several segments of the surface with slope. ...
zephyr0110's user avatar
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3 votes
1 answer
168 views

What causes a visual odometry failure?

Exploring the amazing Curiosity Analysts's notebook*, I came across the following in the "Sol 2931-2932 uplink report": However, the Sol 2929 drive was halted early (well short of location &...
0xDBFB7's user avatar
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7 votes
1 answer
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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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2 votes
1 answer
120 views

Could Ingenuity use the shadow of its legs for navigation to fly autonomously to the sample cache depot location?

It's summertime now in Jezero crater, and according to the HORIZONS Web-Interface the subsolar latitude for Mars varies between both the end of May and November 2021 from 18.5⁰ N to ~25.5⁰ N and back ...
Cornelis's user avatar
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1 vote
0 answers
42 views

How does the orbit determination accuracy depend on the measurement accuracy?

How does the measurement accuracy affect the orbit determination accuracy? Is there any analytical way to find that relation? E.g., 10m range measurement accuracy (1sigma) results in a 100m RMS error ...
Virtus's user avatar
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10 votes
4 answers
2k views

Most accurate attitude determination system in spacecraft?

It seems that IMUs suffer from integration errors that build up over time, so they are not the most accurate means of determining the attitude of your spacecraft. So what then would be the most ...
user avatar
3 votes
0 answers
54 views

Could a Mars rover reliably navigate using the local magnetic fields?

Mars does not have a global magnetic field which guides charged particles entering the atmosphere. Mars has multiple umbrella-shaped magnetic fields mainly in the Southern Hemisphere, which are ...
DrSheldon's user avatar
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3 votes
0 answers
67 views

Detailed description of space shuttle major and minor GNC loops

Warning: repetitive question ahead. Please skip if you're tired of splitting hairs on these things. Is there a detailed description of the major and minor GNC loops of the space shuttle? I've learned ...
user avatar
2 votes
0 answers
350 views

Falcon 9: Stable platform or strapdown IMU?

What type of IMU does the Falcon 9 use? Is it a stable platform aligned with a global frame by gimbals? Or is it a strapdown system fixed to the body of the rocket and therefore aligned not with a ...
user avatar
3 votes
1 answer
183 views

Was space shuttle position corrected for before orbital insertion?

The space shuttle derived its attitude and state vector primarily from its integrating accelerometers and rate gyros. Data from the accelerometers and rate gyros came in at a low rate (0.25-0.5 Hz, or ...
user avatar
2 votes
1 answer
134 views

How well could the New Horizons spacecraft localize itself in space in 3D using parallax?

NASA’s New Horizons Conducts the First Interstellar Parallax Experiment was exciting news, the spacecraft's computer, communication and camera all continue to work in the Kuiper belt due to rigorous ...
uhoh's user avatar
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2 votes
1 answer
179 views

How far would we have to get from the Solar system to be unable to recognize constellations?

So the question is simple. How many light years would we have to go from Earth until we would be unable to determine known constellations?
Vladislav Zalesak's user avatar
6 votes
1 answer
817 views

Guidance vs. Navigation vs. Estimation

I'm still confused over what exactly falls under the scope of Navigation, Guidance, and Estimation systems. Say I have a bunch of IMUs and use them to determine my position and orientation and my ...
user avatar
4 votes
0 answers
78 views

What's the current state of Venus orbital infrastructure?

As per this Wikipedia article there have been a total of 5 orbiters successfully deployed to Venus: Venera-15 Venera-16 Magellan Venus Express Akatsuki Of which only the Akatsuki seems to be ...
Krumuvecis's user avatar
3 votes
1 answer
128 views

What's the current state of Mars orbital infrastructure?

As per this Wikipedia article Mars currently has 6 operational artificial satellites: 2001 Mars Odyssey Mars Express Mars Reconnaissance Orbiter Mars Orbiter Mission Mars Atmosphere and Volatile ...
Krumuvecis's user avatar
2 votes
1 answer
151 views

Travel time from lunar orbit (EML2) to Jupiter using skyhook only?

I am doing background research for a science fiction story, and hoping someone can help with this navigational question. Voyager 2 reached Jupiter from Earth in about 2 years. However (if I understand ...
Crystal E's user avatar
4 votes
1 answer
131 views

Is pulsar timing a viable positioning system for solar system missions

I was reading one of the questions about a version of GPS around Mars, and I started wondering about a Solar system wide positioning system -- large satellites with accurate clocks and powerful ...
Steve Linton's user avatar
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3 votes
0 answers
94 views

How could you turn a satellite constellation into a SatNav system?

Apparently, the UK government wants to convert the OneWeb satellites into its own UK SatNav system, following Brexit which limits the UK's access to Galileo's Public Regulated Service [reports from ...
Dohn Joe's user avatar
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7 votes
1 answer
317 views

How did early inertial navigation systems handle vibration?

In the early ICBM-era rockets, it seems that inertial navigation accuracy was critical. How did these systems filter out the noise in the data due to the vibration of the rocket? If a fairly slow ...
Brad's user avatar
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2 votes
0 answers
106 views

How does Falcon 9 differ from Shuttle or Apollo inertial guidance?

I read a very detailed analysis of the Saturn V. From it I learned there is a computer and guidance "room" which is an extra slice of rocket stacked between the 2nd or 3rd launch stages and the the ...
eSurfsnake's user avatar
4 votes
1 answer
178 views

How can I generate Chebyshev cofficients from SPICE for J2000 Inertial to Moon ME Frame?

I want to extract the Chebyshev coefficients in order to be able to calculate the time-varying transformation from the ICRF / J2000 Inertial frame to the Moon ME (moon mean earth) frame. I know I can ...
Shen Ge's user avatar
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3 votes
1 answer
648 views

What is the math behind satellite star trackers?

I'm trying to understand how star trackers on satellites work and what math they use to determine attitude. For example, is there any trigonometry involved with the stars and how specifically does ...
Sayan Saha's user avatar
4 votes
1 answer
993 views

How does a space vehicle which carries Curiosity or Spirit rover reach a planet? [closed]

I don't know much science but was curious about it. So, what I've seen in movies is that there are lot of objects in the space and many other space items (made of rocks, moving stars etc.). So when ...
Vikas's user avatar
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