I've seen several comments and reports stating the deployment was against the ISS velocity vector. Why do I see arissat out ahead of ISS by a few hundred miles? Keps are current, and 3 tracking programs are in agreement. Can someone provide enlightenment? tnx...:-)
Rich, N8UX.
With the speed reduction, the satellite drops to a lower orbit. The lower the orbit, the less time it takes to go around the Earth, hence it passes satellites in higher orbits.
John WA4WDL
-------------------------------------------------- From: "Rich Dailey" richdailey@windstream.net Sent: Monday, August 08, 2011 8:44 AM To: amsat-bb@amsat.org Subject: [amsat-bb] ARISSat deployment direction?
I've seen several comments and reports stating the deployment was against the ISS velocity vector. Why do I see arissat out ahead of ISS by a few hundred miles? Keps are current, and 3 tracking programs are in agreement. Can someone provide enlightenment? tnx...:-)
Rich, N8UX.
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
Rich,
Orbital dynamics are not all that intuitive. Hand waving answer: By kicking it off the tailgate, it was deployed into a _slightly_ lower orbit. You can see that showing up in your tracking programs as well. However, objects in lower orbits have shorter periods. At 370 km the ISS is about 90 minutes, while satellites at 36,000 km take a day, and are geosynchronous. In fact, as the nominal altitude of the ISS, a single kilometer change of height results in a 19 second difference per day in the AOS. That has been adding up.
73s,
Alan WA4SCA
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Rich Dailey Sent: Monday, August 08, 2011 7:44 AM To: amsat-bb@amsat.org Subject: [amsat-bb] ARISSat deployment direction?
I've seen several comments and reports stating the deployment was against the ISS velocity vector. Why do I see arissat out ahead of ISS by a few hundred miles? Keps are current, and 3 tracking programs are in agreement. Can someone provide enlightenment? tnx...:-)
Rich, N8UX.
_______________________________________________ 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
Thanks to John, Roland, and Alan for answering this. Makes perfect sense, I was having a head-scratching moment though. Enlightenment received and appreciated!
N8UX.
At 09:09 AM 8/8/2011, you wrote:
Rich,
Orbital dynamics are not all that intuitive. Hand waving answer: By kicking it off the tailgate, it was deployed into a _slightly_ lower orbit. You can see that showing up in your tracking programs as well. However, objects in lower orbits have shorter periods. At 370 km the ISS is about 90 minutes, while satellites at 36,000 km take a day, and are geosynchronous. In fact, as the nominal altitude of the ISS, a single kilometer change of height results in a 19 second difference per day in the AOS. That has been adding up.
73s,
Alan WA4SCA
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Rich Dailey Sent: Monday, August 08, 2011 7:44 AM To: amsat-bb@amsat.org Subject: [amsat-bb] ARISSat deployment direction?
I've seen several comments and reports stating the deployment was against the ISS velocity vector. Why do I see arissat out ahead of ISS by a few hundred miles? Keps are current, and 3 tracking programs are in agreement. Can someone provide enlightenment? tnx...:-)
Rich, N8UX.
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
On 8/8/11 6:09 AM, Alan P. Biddle wrote:
Rich,
Orbital dynamics are not all that intuitive.
That's absolutely right. Some historical trivia: even NASA tripped over this in the early days. When the Gemini IV crew tried to rendezvous with their spent booster, they kept missing. They were trying to fly the capsule as if it were an airplane, or maybe a boat floating on the water (only in 3D) but things just didn't work that way. Everything seemed to work in reverse, like that old Star Trek episode with the giant space amoeba.
participants (5)
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Alan P. Biddle -
jmfranke -
Phil Karn -
Rich Dailey -
Rich Dailey