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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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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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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7 votes
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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 ...
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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 ...
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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
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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. ...
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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 &...
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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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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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4 votes
1 answer
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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 ...
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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 ...
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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?
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6 votes
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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 ...
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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 ...
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3 votes
1 answer
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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 ...
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2 votes
1 answer
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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 ...
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4 votes
1 answer
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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 ...
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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 ...
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7 votes
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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 ...
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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 ...
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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 ...
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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 ...
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4 votes
1 answer
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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 ...
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How did the automatic sextant on the late-1950's MIT Mars Probe work?

The reason MIT was chosen to develop the Apollo guidance computer was their Instrumentation Lab. They specialised in inertial navigation and had done impressive work on inertial navigation for ...
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7 votes
2 answers
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Perseverance Rover to drive carefully for months while helicopter hangs from underside?

The image below is cropped from the high resolution version of NASA's Mars Helicopter and Perseverance Rover PIA23824 and shows the helicopter in it's stowed position on the underside of the rover ...
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1 answer
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How to estimate that receiving GNSS signals Earth while orbiting the Moon will still provide locations to about 200 meters of uncertainty?

IEEE Spectrum's Can Astronauts Use GPS to Navigate on the Moon? NASA Scientists Say Yes says: Kar-Ming Cheung and Charles Lee of NASA’s Jet Propulsion Laboratory in California did the math, and ...
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How will NASA's software for autonomous navigation in cis-lunar space be tested; what information is processed, what outputs evaluated?

note: it's been a year and a half and Capstone is scheduled to be launched soon, so perhaps there is more information available now? NASA news item NASA Funds CubeSat Pathfinder Mission to Unique ...
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Could Apollo astronauts see other planets with the CM Scanning Telescope?

The Apollo Command Module had the Scanning Telescope for navigating, "Apollo astronaut located a specific star using a single-power, wide-field telescope." I'm not concerned whether it could ...
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RCS or Reaction Wheel for a 30kg cubesat

I am working on the design of a cubesat, it weighs approximately 30 kg and I am doing the Navigation and Guide Control system. I was wondering if I had some blueprint for some RCS or Reaction Wheels ...
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1 vote
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What is the precision attitude estimation strategy for satellites, under impulsive thrust manoeuvres?

Satellites mostly rely on star trackers and gyros for precision attitude knowledge. Under impulsive thrust manoeuvres, I expect the star trackers to blur and provide no attitude knowledge. What is the ...
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6 votes
1 answer
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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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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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Azimuth and elevation from satellite point of view [duplicate]

I have read for calculating azimuth and elevation from the Earth we use north east up reference frame. What reference frame is used for satellite to measure azimuth and elevation on the Earth? And ...
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10 votes
1 answer
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How would the state vector be updated in the Apollo Guidance Computer during coasting to/from the moon if communication with Earth was lost entirely?

This source https://www.hq.nasa.gov/alsj/alsj-average_g.html states that: From time to time, Houston could update the onboard SV using tracking and other available date; [sic] but, generally, it ...
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9 votes
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How did the star tracker on the Corona (Key Hole) satellite work?

The first Corona Photographic Surveillance Satellite was launched in 1959. Starting from the third mission, launched in 1961, the satellites were equipped with a star tracker. From Wikipedia: ...
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Mode during Apollo landing in cross pointer

In this Question the excellent answer explains from the handbook that the cross pointer input can be either from landing radar or PGNS or AGS. My question is which mode was choosen during the final ...
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14 votes
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Radar Altimeter in Space Shuttle

I was going throught the Space Shuttle Handbook, chapter Guidance and Navigation. In one of the Note boxes, it is written Radar altimeter altitude is not used for navigation or guidance. The ...
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Given small computational resources, how was navigation implemented? (Not samples of old guidance software)

Update 2 : The youtube vidoe How did NASA Steer the Saturn V answers this question and then some, a must watch. Update: I really wanted to know how spacecraft navigation (not guidance) computers ...
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