Good information Dan, We learn a lot! I think that whole amateur radio satellite comunity are looking forward to have a "chance" and bring back HEO or MEO satellite. Another like FO-29 for me was good enough :)
Best regards, Fabiano CT7ABD On Sun, Jul 6, 2014 at 8:03 AM, Daniel Schultz <[email protected]> wrote: > >I noticed that after the last Dnepr launch, it's upper stage was raised > >to an apogee of 1454 km, putting it in a 1454 km x 609 km orbit with a > >97.9 degree inclination, in order to avoid collision with any of the 37 > >satellites it released. > > >There are, however, no legally binding requirements regarding debris > mitigation. > > > International agreement requires that objects in orbits lower than 2000 km > must exit that region within 25 years after end of mission. Objects in > orbits > above 2000 km can remain there for longer than 25 years in a "disposal > orbit", > but only a few missions have the excess propulsion capacity to reach that > orbit. Some US Government missions have disposed of upper stages to a > higher > orbit to avoid the need to issue a Notice to Airmen concerning the falling > debris hazard. At least one polar orbiting weather satellite launch sent > the > upper stage on an Earth escape trajectory for disposal. > > It would seem that the Dnepr orbit is still too low to satisfy the > international requirement. > > >In the case of amateur transponder satellites they can be assumed to have > an > >operation lifetime of 40+ years (think OSCAR-7), as I recall debris > mitigation > >suggests re-entry within 25 years of the end of mission. For amateur > transponder > >satellites this might imply 65 years in orbit. > > NASA is considering a revision to this policy to specify a total lifetime > in > LEO of no more than 30 years regardless of mission lifetime. > > Other interesting facts from Scott Hull's July 1 colloquium at NASA Goddard > include: > > 1. There are about 22,000 objects larger than 10 centimeters in the NORAD > database, an estimated 500,000 objects between 1 and 10 centimeters which > are > too small to track, and millions of objects less than one centimeter. The > Chinese Fengyun 1C disintegration in 2007 produced about 2850 trackable > pieces > of debris. The new S-band space fence will be capable of tracking objects > larger than 5 centimeters when it becomes operational in 2018. > > 2. There are about 4000 dead satellites on orbit, and about 1000 active > satellites. > > 3. The debris population has peaks at 750, 900 and 1400 km. You would have > to > go to Saturn to find a worse debris environment than that of a 750 km Low > Earth Orbit. Science missions can be difficult when you live in a > minefield. > > 4. Most spacecraft disintegrations are caused by battery and pressure > vessel > explosions. Nickel hydrogen batteries are most susceptible to explosion but > NiCd and lithium ion batteries can also explode. A lithium ion battery must > NEVER be recharged after it has been fully drained. Rocket bodies left in > GTO > are subject to explosion when the perigee height dips low enough to begin > atmospheric heating, which can cause remaining fuel in the tanks to > explode. > Modern mission design requires that batteries be disconnected from solar > arrays and fully discharged and pressure tanks vented to space at the end > of > the satellite mission. > > 5. Space is still pretty big. We have been lucky so far. Statistics predict > another eight or nine major collisions in the next 40 years with just the > current population of debris. > > 6. The movie "Gravity" did have a science adviser, and they did get a few > things right, namely that there were no loud sounds when the debris struck > the > shuttle, and objects with lower area to mass ratio arrived first. > Nevertheless > most NASA folks still consider the movie to be a comedy. If you have the > DVD > there is an additional 20 minute documentary video about orbital debris on > the > disk. > > For more information see http://orbitaldebris.jsc.nasa.gov/faqs.html#6 > > 73, Dan Schultz N8FGV > > > > > > > > > > _______________________________________________ > Sent via [email protected]. 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 [email protected]. 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
