# Questions tagged [time]

How passage of time impacts space exploration activities.

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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 | ...
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### Orbit Determination from Position and Velocity

I'm working on a game, somewhat similar to KSP (no building rockets, just beautiful orbital acrobatics). It's in a "small" star system, radius of 6 AU, and it features celestial bodies ...
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### Are there multiple types of UTC time?

I have been checking in detail the specifications of RINEX navigation files version 3.05, and something in the definition of the header of these navigation files caught my attention. One of the lines ...
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### TLE propagation, I don't understand which time should I use in (t - t_0)?

I'm trying to plot ground tracks with the help of TLE data. However, there are some equations that contain "times", and I can't understand which time I should use and format. Like for ...
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### Why would astronauts need a wristwatch and a separate timer?

Watching this image used in this question Why would astronauts in SpaceX's Crew Dragon need two separate timing devices: one portable digital timer, and one wristwatch, rather than carrying into orbit ...
1 vote
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### How long would it take before we use up all the ice in the asteroid belt? [closed]

Lets say that we have an interplanetary society using the ice from asteroids to convert it into rocket fuel, how long would it take before we have used up all the ice on the asteroids. Conditions: We ...
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1 vote
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### How to calculate Local Time of Ascending Node (LTAN)

I have a time series of satellite position, $\mathbf{r}(t_i) = (r_i,\theta_i,\phi_i)$ representing geocentric radius, colatitude and longtiude at universal times $t_i$. I want to compute the Local ...
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### How fast could we go back to Uranus and Neptune?

Since SpaceX is making everything so much cheaper to launch into space. If we launch a pair of orbiters to Uranus and Neptune, how fast could they get there? They could be really light and small, so ...
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### Which programs are used to calculate delta V and launch dates to get to other objects?

I have noticed that many people here have used different programs to calculate the launch dates and delta V to get to other planets. For example: https://space.stackexchange.com/a/59585/44505 https://...
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### At what Mars-time did Perseverance land?

The Perseverance rover landed February 18, 2021 at 20:55 UTC, Earth-time. What time was it on Mars when Perseverance landed?
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### What is the difference between Quartz Clock and Atomic Clock?

I want to know why an atomic clock is more accurate than a quartz one? I understand that the atomic clock can give time to the nanosecond, say it is 10:30:24.123456789. If we have 1GHz quartz clock, ...
1 vote
172 views

### Does NASA use UTC for all their missions?

During Apollo 11 launch they said "Liftoff, we have a liftoff, 32 minutes past the hour", which is 01:32 p. m. or 13:32. This is UTC time, because Apollo 11 happened at 08:32 EST. The ...
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### How old is the use of "L minus" to denote the number of days before launch?

In the SpaceX Inspiration4 Launch broadcast at about T-01:31:05 (91 minutes before launch) the term "L minus five" is used. While "T-minus" is a ...
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### What time format does Voyager twitter use?

Lately I saw this strange date format in a Voyager 2 tweet: Sister ship @NASAVoyager is 21 hrs 19 mins 00 secs of light-travel time from Earth (2021:247:120000:1L) Of course I understood that first ...
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### Could a satellite use a Miniature Atomic Clock (MAC) to provide GPS services?

I've been investigating GPS satellites and I got curious about onboard atomic clocks. I found this following paper on the concept of a CubeSat GPS constellation using Chip-Scale Atomic Clocks, and ...
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### How long would it take for air to completely leak from a spacecraft?

If a spacecraft of volume V was leaking air of density rho as a mass flow rate of m-dot can you calculate the time for all the air to leak out using (rho x V)/m-dot? rho would decrease and m-dot ...
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### How do we get to Mars in a week (7 days)?

Looking at the times that are quoted to go to Mars (months) makes me wonder what speed do we need to get there in a week? Chemical rockets can get to ~4.5 Km/s, thermal nuclear rockets is about twice ...
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1 vote
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### Can anybody recommend a 'good' book to learn about black holes? [closed]

I am really interested in learning about black holes, and tbh I know absolutely nothing about them. But I am really eager to learn about them. So I'm searching for books that can teach me in easy ...
79 views

### Science Contest Topic (space exploration)

I'm thinking of entering the Breakthrough Junior Challenge. It is a global science video contest in which participants have to explain a hard science/math topic in a 3 min video. Right now I'm ...
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1 vote
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### Time in Space (1 year in space, 7 years on earth?) [closed]

I heard that in certain parts in space, time will move faster than on earth. So they say 1 hour is 7 years on Earth. So what I would like to ask is if you have 1 hour in space, would you age the same ...
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### What time zone is used for JPL tests?

The JPL ASPIRE test video has a time code for the launch. Day Of Year:Hour:Minute:Second.Microsecond. What's the time zone?
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### How to convert GPS time to TAI time to UTC time?

I had naively assumed that GPS time and TAI were the same thing until I saw this answer: https://space.stackexchange.com/a/22244/12508 I know that there are differences between Terrestrial Time (TT) ...
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1 vote
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### Does Perseverance have a gnomon on it?

Though How many sundials, Sun compasses and gnomons are there on solar system bodies? is as yet unanswered, Wikipedia's https://en.wikipedia.org/wiki/MarsDial currently tells us that only the ...
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### How will Lucy "make use" of a deep space atomic clock?

The entry for Lucy in Wikipedia's Selection of Discovery Mission 13 and 14; Finalists says: The mission will make use of the Deep Space Atomic Clock.81 81https://www.universetoday.com/122822/...
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### Computation of Barycentric Dynamical Time using SPICE's definition

I've written a high fidelity time management library (hifitime, currently in Rust, Python interface planned) which converts between time systems (TT, TAI, UTC, etc.) and time representations (...
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### Has anyone seriously considered a space-based time capsule?

It seems likely to me that with climate change, pandemics, economic downturns, nuclear or biological warfare that our civilisation could quite easily lose the ability to get into orbit. We could even ...
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### How are Experienced and Observed Mission Elapsed Times defined? (EMET & OMET)

To the question titled What timezone would be used for interstellar travel? this currently unsourced answer currently says in toto: I suspect any interstellar travel will have relativistic effects (...
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### Skyfield, how to use https:// instead of ftp://?

Using skyfield I get the error : OSError: cannot get ftp://cddis.nasa.gov/products/iers/deltat.data because <urlopen error ftp error: TimeoutError(10060, 'Ein Verbindungsversuch ist fehlgeschlagen, ...
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### Updating of TAI

In spaceflight keeping track of time between systems widely separated in space (e.g. people on Earth vs spacecraft in deep space) and/or time, moving at substantial relative velocities and in ...
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### How Much Time Did We Have to "Duck and Cover" From an ICBM Launch Only 666 Miles Away? [closed]

During the Cuban Missile crisis I was stationed at Fort Wainwright, Alaska. As it had on many other occasions during the "cold war," our battle group began those infamous, "13 Days" by going on alert. ...
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### How does time work on other planets?

I’m a game developer making a space-based game. I want to implement a system where the time is different depending on the planet. I think this would work like time zones, but to be honest, I’m not ...
214 views

### What specific event determined the "end" of a shuttle mission?

We've had several questions about when a mission officially "begins". But what about when a mission officially "ends"? The Apollo Flight Journal stops the mission clock at splashdown. What was the ...
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### Will transit time render Mars disease free?

It's going to take us a few months to travel to mars in our spaceships. Will the relatively small size of the ship combined with a few months of "isolation" result in Mars being disease free until ...
121 views

### What schedule do Curiosity operators follow so Mars Time does not negatively impact their performance and health?

In the Choosing Mars-Time: Analysis of the Mars Exploration Rover Experience paper (2004), the NASA Ames Human Factors group recommends that those working on the Mars Exploration Rover mission should ...
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### How are Spacecraft Event Times (SETs) managed; to what timescales are they linked?

Spacecraft Event Time explains the importance of remembering just how darn slow light is; it takes minutes, hours, and in a few cases almost a day for light to travel one way between humans and their ...
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### When did Curiosity land in the Martian Darian calendar?

The New York Times' Why Mars Needs Leap Days, Too “I daresay there have been more different proposals for Mars calendars than there are different calendars for the Earth,” said Michael Allison, a ...
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### Astronauts and Time Dilation

Do astronauts experience any effects of time dilation? Based on my (very limited) understanding, both a change in speed and in gravity should have an effect - and astronauts experience both. The ...
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### New Year's Celebration on the ISS

When/what time zone do astronauts aboard the ISS celebrate the new year? Bonus: How many NYE's can astronauts aboard the ISS celebrate, counting only when the new year starts in the time zone they'...
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### What time is NASA using for Horizons web output?

Here's an example of some output from JPL's Horizons web interface. NASA does not (appear to) specify which GMT is at those hours that the specific transits occurred, or at least I can't find it. ...
310 views

### Please explain the time reference shown in shuttle launch engineering video

Many shuttle launch engineering videos show an apparent time reference to the right of the frame as red numbers counting up rapidly. For example, from the amazing video "Ascent". Assuming this is ...
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### Converting UT1/UTC to Julian Date

I am reading about the algorithms to convert from date and time format to Julian Date from the Fundamentals of Astrodynamics and Applications by Vallado (4th Edition) p183. My question is ...
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### UTC timestamp format for launch vehicles

Has anyone ever seen UTC timestamps of the format xxx:HH:mm:ss.sss? What are the three x's at the front. For reference, this timestamp belongs to an upcoming launch in June of 2019.
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### How did Shuttle computers internally represent time?

How was time represented in the five AP-101 general-purpose computers of the Space Shuttle? How many bits? Encoded as a plain binary count? Split into hours, minutes, seconds, subseconds? Binary-...
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### How would 2 spacecraft be launched to be in sync in opposite directions?

How would 1 spacecraft be launched to have a prograde orbit and the another be launched retrograde to have a mirrored orbital path around the sun or otherwise? Would the 2 spacecraft launch together ...
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### Instead of approaching Mars from behind can we approach Mars from the front of its orbital path? [closed]

Nine months is what google maps said to get to Mars. I would like to know if fuel was no expense how long could we get to Mars other than the method below? Is the 9 months and the method just what our ...
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### What is a safe speed in space for spacecraft?

Does traveling fast as possible shortening the duration of the mission lessen chances of collision or mechanical failure, or does traveling slower in space in some way safer?
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### Apollo Missions - Travel time to moon [duplicate]

I must be missing something - escape velocity is about 25,000mph. The distance to the moon about 240,000 miles. That computes to about a 9 hour flight. Why did it take 3 days for Apollo missions to ...
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### Constant Acceleration in Space. How much time for a given distance?

I have been researching a lot and can't make any sense of it all, so I am trying my luck here. I want to program a simple formula that gives me the travel time in space. I have a constant thrust of ...
1 vote