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.

Filter by
Sorted by
Tagged with
1
vote
1answer
52 views

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 ...
5
votes
1answer
286 views

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 ...
2
votes
1answer
107 views

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 ...
0
votes
0answers
38 views

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 ...
10
votes
1answer
663 views

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 ...
9
votes
1answer
238 views

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: ...
1
vote
1answer
50 views

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 ...
14
votes
1answer
2k views

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 ...
38
votes
6answers
15k views

Given small computational resources, how was navigation implemented? (Not samples of old guidance software)

Update: I really wanted to know how spacecraft navigation (not guidance) computers worked, given small computational resources. I have asked in another question and edited this question to limit ...
1
vote
0answers
39 views

Have lunar (or martian) rovers exploited shadows, perhaps for terrain comprehension or obstacle avoidance?

This answer proposes that light bars would be better than a single headlight for night time navigation on the Moon because a single headlight will generate hard shadows. Considering this is exactly ...
1
vote
1answer
94 views

How do small, spin stabilized launchers follow a rhumb line?

This concise answer to What exactly is rhumb-line control in the context of a launch trajectory? explains the concept in the context of the SS-520 nanosatellite launch vehicle (which "doesn't exist"). ...
3
votes
1answer
482 views

What exactly is rhumb-line control in the context of a launch trajectory?

The conference paper SS-520 Nano satellite launcher and its flight result SSC18-IX-03 from the 32nd Annual AIAA/USU Conference on Small Satellites linked in this answer describes the use of rhumb-line ...
23
votes
2answers
7k views

How did astronauts using rovers tell direction without compasses on the Moon? [duplicate]

I read that the astronauts who used Lunar rovers used heading indicators, which typically use compasses, for direction. How, on the Moon, did their equipment tell the direction of travel, presuming a ...
4
votes
2answers
113 views

Help understanding exactly how an atomic clock facilitates “self-driving spacecraft” when paired with an onboard camera?

The TechCrunch article NASA details Deep Space Atomic Clock and other tests launching on SpaceX Falcon Heavy says: Jill Seubert, Deep Space Navigator for NASA, explained that this is the world’s ...
2
votes
1answer
119 views

How does an onboard atomic clock help interplanetary navigation?

On 2019 June 22, JPL will launch and test the accuracy of an onboard atomic clock. Its FAQ says that it will improve interplanetary navigation because for the ship to determine its position, instead ...
2
votes
1answer
80 views

Satellite mission design/performance requirements to attitude/orbit control design specifications

Are there any good sources that discuss: the steps involved in deriving attitude/orbit control design specifications, from satellite mission design/performance requirements?
1
vote
1answer
144 views

Is there any kind of research on *sub*-orbital rendezvous-ing with a space tug outside the atmosphere?

The key difference with a plain old-fashioned orbital rendezvous would seem to be that there'd be limited time to only briefly match velocities and trajectories: Let's say a vehicle launched from ...
4
votes
1answer
210 views

Celestrak GLONASS TLE's showing satellite numbers not listed in the GLONASS constellation, others missing

For a project, I'm retrieving TLE information live from http://celestrak.com/ and using them to simulate satellite orbits. The TLE's for the GLONASS constellation (http://celestrak.com/NORAD/elements/...
12
votes
1answer
341 views

When did Houston figure out where the Eagle had landed?

Between starting the descent burn three seconds late, and having to avoid landing in a boulder field, the Apollo 11 descent module almost completely missed the target landing ellipse. During Apollo ...
6
votes
1answer
180 views

Spacecraft Navigation

Reading fascinating things about New Horizon's journey in the Kuiper Belt, I asked myself the following question: how can one know the spacecraft's position and speed, and with which precision? Of ...
6
votes
2answers
130 views

A gedanken on being able to navigate back to Earth

Imagine a sphere centered at Earth with a radius of 4 light years. Suppose we pick a random point on the surface of this sphere and drop someone, let us say, "Joe" there. Will Joe be able to come back ...
1
vote
0answers
85 views

How can New Horizons reliably approach Ultima Thule over a huge distance? [duplicate]

How did New Horizons navigate to Ultima Thule over 80 million miles from Pluto given the chaotic effect of gravity (from unpredictable local and distant matter) on New Horizons and the fact that the ...
4
votes
3answers
321 views

Why doesn't New Horizons have a tracking function

Dr. John Spencer mentioned in the live feed for the Ultima Thule flyby they're taking a series of LORRI shots along a precomputed path hoping to capture the KBO. What were the obstacles to equip the ...
2
votes
0answers
130 views

How presise could 2 satellites “thread the needle” in orbit?

I have a question about using a magnetic field to propel 2 satellites off each other while traveling in opposite directions on the same orbital plain to intersect either 2:1 or 1:1 on each orbit ...
6
votes
1answer
706 views

What coordinate system was used for the Apollo missions?

This is specifically about the Apollo missions, which are not touched in this related question. Did they use one coordinate system throughout the entire mission, or did they switch depending on the ...
11
votes
5answers
745 views

Is it possible to navigate space travel with no computer?

From launch to land could a person travel in space with only mechanical devices like a sextant? With enough experience what would be the minimum devices needed? Which vehicle currently would be easier ...
4
votes
0answers
417 views

Why would someone use Modified Rodrigues Parameters over Quaternions for spacecraft attitude estimation? And vice versa?

I see quite some papers on spacecraft attitude determination and control, that rely on quaternions. While some others rely on MRPs. The advantage that I see so far is that... for quaternions, the ...
5
votes
1answer
168 views

Has a cubesat in LEO determined its orbit and position using only terrestrial cameras plus the Sun? (no GPS, starcam, uplink, magnetic sensors, etc.)

From LEO, a cubesat with several reasonable cell phone-like cameras (or better) can image the Earth and it seems straightforward for some standard pattern recognition algorithms to find the sunlit ...
3
votes
1answer
101 views

Help understanding BepiColombo's weak capture at Mercury's L1 and need for delta-differential one-way range measurements

This four-minute BBC podcast Mission to Mercury: BepiColombo spacecraft ready for launch highlights several challenges of the BepiColombo mission, including its orbital-mechanical aspects and is worth ...
4
votes
1answer
153 views

What brand and model is the hand-held sextant tested on the ISS?

Astronaut Alexander Gerst is testing an hand-held sextant on the ISS in the context of the experiment Sextant Navigation for Exploration Missions, see picture below. What is the brand and model of ...
2
votes
1answer
413 views

How was the Apollo IMU calibrated?

Both the command and lunar modules of the Apollo spacecraft has navigation systems with inertial management units. IMUs are known to drift over time. How were they recalibrated? My answer below ...
1
vote
6answers
533 views

How would blockchain be integrated into spaceflight? Have any methods been proposed yet?

Blockchain offers a way of keeping track of information such that its authenticity can be verified and it can not easily be falsified. In a space environment with an increasing number of both active ...
3
votes
0answers
79 views

How are Hayabusa2's target markers deployed?

This presentation talks about 'target markers' which are five soft, reflective balls that are released onto the asteroid's surface prior to landing. They allow the probe to more precisely locate the ...
2
votes
0answers
119 views

What is the nature of the sextant tests on the ISS for Orion cis-lunar emergency navigation?

According to the NASA Johnson video Space to Ground: A Star to Steer By: 08/10/2018: A tool that once helped sailors cross vast oceans for centuries is now being put to the test in space. The crew ...
8
votes
1answer
943 views

Machine Learning and Classical Navigation, Guidance and Control in Space Exploration

Due to the increasing availability of large quantities of data and computational power, machine learning (ML) is providing increasingly better results in various fields. Much research has been done on ...
9
votes
1answer
444 views

Does the “17” really mean anything with respect to GNSS orbits being rational factions of a sidereal day?

This answer suggests that the orbital periods of the four large GNSSS contstellations are linked to the sidereal rotation period of the earth by rational numbers with 17 or 34 as the denominator in ...
1
vote
3answers
232 views

What is a gyrocompass and how might one be used by a planetary rover?

In comments and links therein below the question How does Curiosity know how to point and move it's high gain antenna in real time? there is mention of a gyrocompass. I am aware that gyros can be ...
5
votes
1answer
1k views

Was the Apollo sextant used (or tested) to determine position while in Earth orbit?

The video Apollo Program Guidance and Navigation System 79974 explains that the spacecraft's sextant could be used together with the navigation computer to determine a position fix while in Earth ...
6
votes
3answers
718 views

Soyuz has a Space Periscope?

The image Photo ID: ISS049-E-003166 can be found in Flikr and Wikimedia Commons as well as in Spaceflight Now. There is a long (perhaps 1 meter?) green structure that is sticking out from the side of ...
3
votes
1answer
224 views

Is NICER/SEXTANT the first civilian “spacecraft” to determine it's own position in space without GPS or uplinked data?

Computers on board spacecraft can determine their positions using a combination of uplinked data from the ground and for those closer to Earth, GPS/GNSS. (See this answer and this question for ...
6
votes
1answer
117 views

Inexplicable Offset in Satellite Laser Ranging (SLR) observations

I am struggling with the implementation of a Satellite Laser Ranging (SLR) validation tool. The situation is as follows: I am provided with a framework which gives me the position of a SLR ...
6
votes
1answer
393 views

Navigating in space with only cameras

I'd like to figure out how to determine where something is in space (solar system) based only solely on measurements that can be preformed on location visually/with a camera. Let's say I'm floating in ...
5
votes
0answers
169 views

GPS Receiver Autonomous Integrity Monitoring (RAIM) - parity space method

I am trying to understand RAIM. My teacher explained three RAIM methods, I will just quote all of them because I think that the jargon might not be consistent. Maximum separation / Position ...
2
votes
1answer
675 views

Does Venus have a north star or south star?

I am trying to figure out how you would navigate on Venus. On Earth you can use Polaris as a North Star to find north. Would there be a star on the Venus sky which could function as either a north ...
5
votes
5answers
514 views

How might Earth's location be referenced in stellar terms?

Apologies if this has been asked before using terminology for somebody more familiar with the subject matter. I've searched but cannot find an answer. Assuming space travel was possible (to other ...
1
vote
2answers
83 views

What's a good source of information on determining spacecraft positions via radio?

I'm willing to spend a decent amount on a textbook, but please tell me about cheap or free sources as well.
5
votes
1answer
210 views

What determines if a star tracker blends two stars that are close to each other?

If two stars are very close to each other, a star tracker could identify the pair as a single star, with a magnitude and position different from both stars. This obviously impairs the software's ...
2
votes
3answers
303 views

When was stereoscopic photography first used intentionally on solar system body?

I have stumbled across the fascinating page Photogrammetric Analysis Of Apollo 11 Imagery: New camera-station map with improved locations at the following website: https://www.hq.nasa.gov/alsj/a11/...
1
vote
2answers
265 views

Satellite Position

The Voyager 1 took one last photograph in 1990 and after that, the camera equipment was shut off for power saving. However, the estimates of where the photo was taken in space vary by many hundreds of ...
9
votes
1answer
453 views

How do we define geographical coordinates on non-spheroid celestial bodies?

On Earth, we can use latitude and longitude to fairly accurately describe a single point on the surface of the earth. This works because the earth is, for all intents and purposes, a sphere. It got me ...