Questions tagged [time]

How passage of time impacts space exploration activities.

40
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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 ...
32
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5answers
40k 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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4answers
16k 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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3answers
20k 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 ...
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 ...
16
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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 ...
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 ...
15
votes
3answers
495 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 (...
15
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1answer
380k 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,...
14
votes
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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4answers
935 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 ...
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
3k 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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4answers
2k 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
15k 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!
10
votes
1answer
198 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
votes
2answers
932 views

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
votes
4answers
8k 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 ...
9
votes
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 ...
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
votes
2answers
11k 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 (...
8
votes
1answer
750 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. ...
6
votes
2answers
1k 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
votes
1answer
243 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,...
6
votes
3answers
844 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 ...
6
votes
1answer
173 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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0answers
78 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-...
6
votes
0answers
328 views

Which astronaut has experienced the largest relativistic shift in time (relative to the 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 ...
5
votes
2answers
1k 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
votes
1answer
90 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
votes
3answers
189 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
votes
1answer
212 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
votes
1answer
574 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 ...
3
votes
3answers
846 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
votes
3answers
454 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
votes
1answer
209 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
293 views

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

For reference: https://en.wikipedia.org/wiki/Zond_5 It is now clear that when we are in space for a long time, our body loses some mass. The question I want to ask is, how much time is needed for a ...
3
votes
2answers
198 views

Can the TLE epoch be listed as in the future? How?

Can the epoch time of a TLE be in the future? Context: ISS TLE from Heavens Above 1 25544U 98067A 18193.60071450 .00016717 00000-0 10270-3 0 9013 2 25544 51.6401 252.0472 0003848 304.4303 ...
3
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1answer
163 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
votes
2answers
859 views

How to calculate Coordinated Mars Time (MTC)?

I'm trying to figure out how to calculate Coordinated Mars Time (MTC). Can it be calculated directly from Earths current time/date, or calculated from the current Mars Sol Date (MSD)? From this wiki ...
3
votes
3answers
345 views

How far can you travel until you can't get back to where you started?

I searched for this question but couldn't find it, so I'm asking. Lets just ignore turning into a liquid at high accelerations and the fact that an object with mass cannot travel at the speed of light ...
2
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3answers
168 views

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 ...
2
votes
1answer
226 views

A laser can propel a spacecraft to 20% of light speed, time shorter on spacecraft?

So I recently learned about a project about using lasers on Earth to propel a spacecraft to 20% of light speed for interstellar traveling. So this brings an interesting question, how much shorter ...
2
votes
1answer
95 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 ...
2
votes
1answer
199 views

What happened to time in 1962? (JPL Horizons changes displayed time from UT1 to UTC for dates starting in 1962)

I was viewing some observer output from JPL's Horizons while writing this answer and I saw this annotation. "Prior to 1962, times are UT1. Dates thereafter are UTC". Presumably users of JPL's ...
2
votes
1answer
139 views

Tesla Near Mars Orbit

When will the Tesla Roadster come into a near Mars orbit as shown in the SpaceX simulation shown in Elon Musk's tweet? Is it 10 years, 20 years or when?
1
vote
4answers
1k views

Where can the term “Sol” used?

Alright, I know that "Sol" is used on Mars to count days. But is the sun called: "Sol"? And can you use that term on Earth as well? The reason for the question is that the term "sol" is used in two ...