[amsat-bb] Re: Multiple satellite launches (rates?)
> The following link is of Picodragon and 2 other satellites > being released from ISS. There is a picture and short video. > http://amsat-uk.org/tag/picodragon/ Looking at the video, my uncalibrated eyeball counts the deployment rate at about ½ meter per second? Ie, in the first second of video, the 3 cubes move about the same distance as their overall combined length. And in 2 seconds about the same again. Using the still photo at the top of the page, I estimate about 10cm of additional spacing between the 3 cubesats total or about ½ meter for this overall length. Of course there is some parallax difference between the two views, but my guess is about 1/2m per second if the frame-timer in the video is a rough guess. But this is the ISS launcher which might be different from the PPOD launchers on the Dnepr and Minotaur. Just guessing of course.. Bob, Wb4aPR -original message - Doesn’t much matter when they are released, they still are all in the same orbit more or less for quite a while. Even if the springs release them at 1/2 meter per second, they are all going at 7000 meters per second so it takes days for them to separate very much. Let’s see, at ½ meter per second separation, then they are 100’ apart after the first minute, 1 mile after the first hour. And not until they are a few miles apart can NORAD distinguish them enough to start getting good tracks on them. By then it is impossible to know which is which. Hence the guessing game until each owner decides which object best fits his downlink experience. Continuing on, they will be 24 miles apart after the first day where they will be about 5 seconds apart when tracked from the ground. After a week, then maybe 175 miles and ½ minute apart. After a month, maybe 750 miles and 2 minutes apart. After a year, maybe 9000 miles and 30 minutes apart. And finally, after about a year and a half, they will be half an orbit or about 45 minutes apart, beyond which, they start getting closer again… Something like that unless I screwed up… Bob ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: Multiple satellite launches
Thanks for that explanation Bob. The members of the Eagle-2 ($50sat) team were having this discussion last night and none of us knew the answer. Now we do ! We were trying to determine when using the UNISAT-5 keps would no longer be valid for $50sat. - Howie AB2S ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: Multiple satellite launches
Bob The following link is of Picodragon and 2 other satellites being released or launched. There is a picture and short video. http://amsat-uk.org/tag/picodragon/ 73 John KC0BMF On Mon, Nov 25, 2013 at 9:54 AM, Robert Bruninga wrote: > Ø When there is a launch of several satellites in a single payload, > several cubesats for example, I assume they release each at > different locations on the deployer trajectory. Preliminary keps are based > on the trajectory when each is released? > > Ø Otherwise if they were released all at once, how would NORAD know which > is which? > > > Doesn’t much matter when they are released, they still are all in the same > orbit more or less for quite a while. Even if the springs release them at > 1/2 meter per second, they are all going at 7000 meters per second so it > takes days for them to separate very much. > > > > Let’s see, at ½ meter per second separation, then they are 100’ apart > after the first minute, 1 mile after the first hour. And not until they > are a few miles apart can NORAD distinguish them enough to start getting > good tracks on them. By then it is impossible to know which is which. > Hence the guessing game until each owner decides which object best fits his > downlink experience. > > > > Continuing on, they will be 24 miles apart after the first day where they > will be about 5 seconds apart when tracked from the ground. After a week, > then maybe 175 miles and ½ minute apart. After a month, maybe 750 miles > and 2 minutes apart. After a year, maybe 9000 miles and 30 minutes apart. > And finally, after about a year and a half, they will be half an orbit or > about 45 minutes apart, beyond which, they start getting closer again… > > > > Something like that unless I screwed up… > > > > Bob > ___ > Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: Multiple satellite launches
Ø When there is a launch of several satellites in a single payload, several cubesats for example, I assume they release each at different locations on the deployer trajectory. Preliminary keps are based on the trajectory when each is released? Ø Otherwise if they were released all at once, how would NORAD know which is which? Doesn’t much matter when they are released, they still are all in the same orbit more or less for quite a while. Even if the springs release them at 1/2 meter per second, they are all going at 7000 meters per second so it takes days for them to separate very much. Let’s see, at ½ meter per second separation, then they are 100’ apart after the first minute, 1 mile after the first hour. And not until they are a few miles apart can NORAD distinguish them enough to start getting good tracks on them. By then it is impossible to know which is which. Hence the guessing game until each owner decides which object best fits his downlink experience. Continuing on, they will be 24 miles apart after the first day where they will be about 5 seconds apart when tracked from the ground. After a week, then maybe 175 miles and ½ minute apart. After a month, maybe 750 miles and 2 minutes apart. After a year, maybe 9000 miles and 30 minutes apart. And finally, after about a year and a half, they will be half an orbit or about 45 minutes apart, beyond which, they start getting closer again… Something like that unless I screwed up… Bob ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
