[amsat-bb] Dnepr Upper Stage Apogee

[Fabiano Moser]

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 <n8fgv at usa.net> 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
>
>
>
>
>
>
>
>
>
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