Questions tagged [time]

How passage of time impacts space exploration activities.

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1answer
46 views

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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3answers
459 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.
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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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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 ...
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3answers
170 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 ...
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2answers
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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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3answers
970 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 ...
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1answer
138 views

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 ...
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Backwards time dilation paradox [closed]

We have a pair of atomic clocks. Let's call them clock A and clock B. We switch both of them on at the same time. Clock A will stay on Earth and clock B will go with the astronauts. Astronauts with ...
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1answer
228 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 ...
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2answers
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What is the date for a Mars file?

When a robot on Mars does something like take a picture, how does it date that file? I imagine that the responsible laboratory is a possible referential, correct? Is it possible / does it make sense ...
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How long to surpass Voyager satellite distances using modern technology? [duplicate]

NASA's JPL just recently acknowledged that Voyager II has now joined Voyager I in entering interstellar space after 41 years of space travel. This got me to wondering: when will we ever get to Alpha ...
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2answers
264 views

What is the delay of the YT live stream for ISS?

On YT, we can see a live stream from ISS. What is the delay here (given you have a modern high speed internet access)?
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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 ...
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1answer
202 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 ...
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1answer
201 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 ...
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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 ...
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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 ...
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2answers
95 views

Time when traveling around the speed of light [closed]

I heard that if you travel at the speed of light or faster (say, to the Kelper systems ) and come back, thousands of years may have passed but you haven't experienced more than a few. How is this ...
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2answers
201 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 ...
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1answer
226 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 ...
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1answer
127 views

2 Hubble telescopes looking at each other for a world CCTV? [closed]

As technology progresses could something like a Super Hubble see satellite the Earth to have a time delay to have any use? Super Hubble A (or a huge mirror) is 30 light minutes away looking at Earth ...
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1answer
765 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 ...
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1answer
140 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?
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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!
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3answers
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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 ...
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Which one is older light or stars? [closed]

I kind of feel that light is older than stars. But is there any scientific theory or hypothesis on it?
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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 ...
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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 ...
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1answer
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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 ...
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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 ...
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1answer
227 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 ...
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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 ...
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1answer
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Do the Voyager probes experience time moving faster due to relativity?

Time goes faster the weaker the gravitational field you are in as long as your velocity is constant. The Voyager probes have moved a long way from the sun and its planets so I presume time must be ...
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1answer
591 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 ...
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Juno to Jupiter Budget

Would the Juno program be more cost effective if the spacecraft took a direct flight to Jupiter rather than using gravitational pull from planets, which took nearly 5 years instead of say, 2 years? ...
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1answer
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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. ...
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1answer
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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 ...
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1answer
340 views

Local Time Calculation

How To Calculate Local Time Of A Sun Synchronous Orbit With A Given Altitude ( Say 600 km ) , Inclination ( 98 degrees ) ?
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Can we displace earth? [closed]

From the gravitation equation it is clear the earth gets pulled but we fall due to negligible mass. But, if each and every person on the earth takes a jet-pack and jumps to a height equivalent to 20 ...
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1answer
283 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,...
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1answer
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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 ...
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1answer
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How long does it take for a satellite to reach MEO? [closed]

I'm just wondering how long it takes satellites from launch to orbiting in MEO.
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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 ...
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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 ...
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1answer
173 views

Time dilation between Earth and a similar planet revolving around a supermassive Black hole [closed]

I was thrilled watching 'Interstellar'. It was only much later that I came to realize certain anomalies in the movie (like the scene in which McConaughey approaches the Gorgantua — his body ...
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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 ...
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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 - ...
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3answers
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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 ...
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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 ...