Questions tagged [time]

How passage of time impacts space exploration activities.

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41
votes
3answers
9k views

Have we attempted to experimentally confirm gravitational time dilation?

Mark Adler wrote in an answer to a different question that We would expect that Voyager 1's local time is faster than Earth time by about one part in one hundred million. I don't think that ...
35
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5answers
46k views

How does GPS receiver synchronize time with GPS satellites?

GPS satellites transmit time values regularly, but if we put in consideration the time delay between the satellite and the receiver, the time value received wouldn't be accurate insofar as I know GPS ...
28
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3answers
3k views

What does NASA mean when they use the term 'PDT (ERT)'

In a graphic describing Cassini's final approach to Saturn NASA lists the timestamps as 4:55 am PDT (ERT). What does this mean? I am assuming that PDT mean pacific time, but I can't find out what ERT ...
27
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3answers
25k views

Determining orbital position at a future point in time

This might come of as a millionth-time award winner beginner question, but since I'm not familiar with either correct terms or designations, I'll put this question in my own language, since I'm not ...
27
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4answers
17k views

What time zone is used on ISS to define a day?

What time zone is used on ISS to define when a day starts? Is it the same as mission control? Do Russian cosmonauts use a different time zone respect to European and American astronauts?
25
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2answers
3k views

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'...
21
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4answers
4k views

How do launches avoid leap seconds? Why?

A short comment in the BBC Crowd Science audio program Does Time really Exist?'s discussion of the slow divergence between UTC and TAI (IAT) (coordinated time and international atomic time) says that ...
17
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7answers
3k views

How can we transmit a date to another species?

I thought about this the other day. We often send messages to outer space hoping that someone picks them up. How could you explain to aliens that we sent this satellite about 13.8 billion years after ...
17
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2answers
2k views

Do the Voyager space probes perform time synchronization regularly?

According to JPL: http://voyager.jpl.nasa.gov/mission/weekly-reports/ Voyager 1 travels at a velocity relative to the Sun of 19.03 km/s (or 0.000063478 c, or a time difference of ~ 0.0005 seconds per ...
16
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3answers
504 views

How would time measurement be done over great distances?

Already on earth the time is a bit of a problem with the time-zones. It is not that big a problem though, since we all "travel" at (nearly) the same speed. Not so in space. With the time dilatation (...
16
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1answer
403k views

The true meaning of Sol regarding time on Mars

I'm writing a story about Mars and I'm really confused as to how one should use the word 'Sol when talking about the passage of time there. For example, Would one say to a colleague: "Today is Sol 345,...
15
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2answers
4k views

How are GPS satellite clocks synchronized with each other in the earth's frame of reference?

I have been looking at different threads. It seems like the receiver clock on Earth doesn't have to be synchronized with the satellite clocks. But I believe the satellite clocks need to be ...
14
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1answer
1k views

Scott Kelly age vs Twin's

Scott Kelly just returned from nearly a year of orbiting the Earth in the space station. How much younger is he than his twin, now that he has spent a significant amount of time, traveling at high ...
13
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7answers
3k views

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 ...
13
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4answers
1k views

Day versus night launches

Most launches that I've seen have occurred during the day. But I've also seen a couple of missions that have been launched at night. Are there any specific advantages or disadvantages to a day launch ...
12
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4answers
8k views

What decides if a launch has to be done instantaneously or during a window?

What determines if a launch has to be done instantaneously or has a launch window of minutes or hours? To what parts is it about celestial and ground issues? Just one example of alleged switching ...
11
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3answers
3k views

How much faster (or slower) would it be for a new probe to reach Pluto?

New Horizions just reached Pluto after almost a decade in space. That means it was launched with technology that is well over a decade old (when you factor in planning and construction time). If we ...
11
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4answers
11k views

How to obtain UTC of the epoch time in a satellite TLE (two line element)?

I want to convert the epoch time of a TLE to UTC. At this moment I am less interested in explanations and history - I just want to know quantitatively, with certainty, how to convert. I'm confused ...
11
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4answers
3k views

Has an interplanetary date/time system been established yet?

Obviously, with no humans living permanently off-planet yet, Earth-style dates and times are the most common system is use, and reasonably so. And it helps that Mars's day is almost the same length ...
10
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3answers
2k views

If the Alcubierre Warp Drive was used to travel to Alpha Centauri, how much time would pass on Earth?

If the Alcubierre Warp Drive was used to travel to Alpha Centauri, how much time would pass on Earth? Per this article, it would take merely days to travel there. Say a ship travels there, spends a ...
10
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2answers
14k views

Would a Moon resident age differently than someone living on Earth?

Say there were a base on the Moon with people living/studying there. Would they age differently than those on earth due to a change in speed through space? Does the Moon move faster through space (...
10
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1answer
2k views

What kind of time regiment/schedule do ISS astronauts have?

On Earth people's lives are usually dictated by a 24-hour rhythm (with about 8 hours of sleep each night). As far as I know this rhythm is determined by chemical processes in the human body which are ...
10
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2answers
16k views

How long will it take for Starman to get to Mars?

How long will it take for the Starman to get to Mars? I'm following the incredible launch of the Heavy Falcon and Starman, and would like to know. Thanks!
9
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2answers
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Which Earth time zone most closely matches the ISS astronauts' daily schedule? [duplicate]

The astronauts on the International Space Station have a daily schedule, particularly when they are asleep versus awake. Which Earth time zone is closest to their daily schedule? What time zone is ...
9
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1answer
2k views

How much light is there on the way from Earth to Proxima Centauri?

I want to know how much light is there for a spacecraft that flies from earth to Proxima Centauri. I know there's the sun but what happens after the spacecraft leaves the solar system? Are there stars ...
9
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1answer
256 views

Problems as a result of clock drift that have occurred in space?

I was reading this question about the clock drift on the Apollo missions and am sure that a drift of 1 second / day on some of the longer missions would likely result in a mission failure due to the ...
9
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1answer
265 views

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-...
8
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3answers
1k views

Is space mining and development as shown in the television show “The Expanse” realistic?

In the television show "The Expanse", we see the Solar System having been partially colonized and developed during the 23rd century. The spacecraft in the show appear to depend on conventional ...
8
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3answers
2k views

How would we communicate over light years?

Anyone who has been in an email conversation where the chain split into different threads, or has been in chat where they receive two diverging comments requiring a response before a reply to the ...
8
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1answer
1k views

How long would it take to travel to Proxima b?

Proxima b is an Earth-like (i.e. rocky) planet, in orbit around the star Proxima Centauri, approximately 4.243 light years from Sol, our home star. If I had a space vehicle capable of accelerating ...
8
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1answer
1k views

How is gravitational time dilation experienced by spacecraft near Jupiter such as Juno

I understand (I think) that a vehicle on or near a planet with greater mass - such as the Juno probe entering Jupiter's orbit soon- will experience time slightly slower relative to us on Earth. ...
7
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1answer
355 views

How far from earth have atomic clocks (or ultra-stable oscillators) been placed and monitored?

The various flavors of GPS satellite constellations use atomic clocks on each satellite. As far as I know, all of the constellations are "shells" of circular MEO orbits in 3 to 6 planes, 20,000 to 25,...
7
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0answers
451 views

Which astronaut has experienced the largest relativistic shift in time (relative to Earth's surface)?

Following this answer and then this question (where I've linked to Cosmonaut Sergei Krikalev; the World's Most Prolific Time Traveller) I've noticed that currently Krikalev does not hold the precisely ...
6
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2answers
2k views

Is GPS time at least “really close” to TAI (International Atomic Time)?

@DavidHammen's answer got me thinking. GPS time "comes from" (US Naval Observatory) a whole bunch of atomic clocks, in space and on Earth. TAI or International Atomic Time also comes from a whole ...
6
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1answer
188 views

What time of events is given for probes a long way away from Earth?

Philae is to land on 67P/Churyumov-Gerasimenko today at 17:02 CET. The comet is currently 3.409AU away from Earth. That means signals from the lander take a little over 28 minutes to reach Earth. Does ...
6
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1answer
92 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 ...
5
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1answer
403 views

Why did the Zond 5 tortoises lose body mass so quickly?

It is well-known that when we are in space for a long time, our bodies lose some mass. My question is how much time would be needed for a person to lose 10% of their body mass? The tortoise inside ...
5
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2answers
2k views

Time, UTC, Julian Date, TLE epoch - how are they related quantitatively?

I am trying to understand the relationship (quantitatively) between JulianDate, UTC, and the epoch of Two Line Elements. It's a deep subject, especially if you include relativity, and a long subject - ...
5
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1answer
93 views

Synchronizing spacecraft communication

When NASA is giving commands to a distant spacecraft like Juno, how is that done in terms of timing and protocol? For example do they: give a command to burn for 15 seconds upon receiving the ...
5
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3answers
264 views

Has any other term been used for a solar day on a solar system body besides “sol” on Mars?

My interest was piqued by this question and answer. For several reasons NASA needed to refer frequently and extensively to a Martian solar day, and "sol" became the nom du jour. There have been ...
4
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1answer
131 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 ...
4
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1answer
357 views

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 ...
4
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1answer
389 views

Martian Names for the Year and Month Time Units

A Martian day unit is called a Sol. A week is supposedly still 7 days/sols. Have there been any (real or fictional) suggestions for new names for other time units like the Martian year? How about ...
4
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1answer
1k views

How would people measure time on Venus?

On earth we can divide our day into 24 hours, and 365 days in the year. I am trying to imagine how people living on airships above the cloud-tops would think about time on Venus given that a single ...
4
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1answer
195 views

How did NASA refer to dates and times of a mission in the 1970s?

Back in the 1970s, how did NASA describe when an event happened during a mission? For example, when Mariner 10 did its fly-by of Venus, how did the Mariner team refer to that moment in time? Did ...
3
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3answers
2k views

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 ...
3
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3answers
493 views

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.
3
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1answer
920 views

Time dilation between Mars and Earth due to different mass

I am not sure I understand the Time dilation correctly but if mass has dirrect impact on time...than lets consider cosmological event - one orbit of planet Earth around Sun. This event will person on ...
3
votes
1answer
116 views

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 ...
3
votes
1answer
60 views

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 ...