On 8/13/13 4:20 AM, Steve Willner wrote:
In article ,
"Richard D. Saam" writes:
Deceleration (aP) as well as radiation power half_life
should then be on the order of 87.7/4 or 21.9 years

You've lost me there. Radiative deceleration should be proportional
to power (according to the equation you quoted earlier), which
decreases exponentially according to the half-life.

but which half life are you indicating:
the RTG plutonium half life of 87.7 years
reflected in power equation
http://arxiv.org/abs/1204.2507v1 page 2
Qrtg(t) = 2^(-(t-t0)/87.74)*Qrtg(t0)
or the electrical half life of 87.7/4 or 21.9 years
http://arxiv.org/abs/1204.2507v1 table 1 data
Qelect(t) = 2^(-(t-t0)/21.9)*Qelect(t0)

The authors choose a subset
aP = n*Q/(pioneer mass *c)
of this more general equation
aP = F*stefan_constant*T^4*(4/(3*c))*pioneer area/pioneer mass
where n*Q = F*stefan_constant*T^4*(4/3)*pioneer asymmetric area

with two components
aP = nrtg*Qrtg/(pioneer mass *c) + nelect*Qelect/(pioneer mass *c)
with a well established finite element basis for
nelect*Qelect/(pioneer mass *c)
and
Qelect(t)=2^(-(t-t0)/21.9)*Qelect(t0)=Qelect(t0)*exp(-ln(2)(t-t0)/21.9)
but with no physical basis for
Qrtg(t) = 2^(-(t-t0)/87.74)*Qrtg(t0)= Qrtg(t0)*exp(-ln(2)(t-t0)/87.74)

The RTG component contribution to Pioneer deceleration (aPrtg) is
nrtg*Qrtg = F*stefan_constant*T^4*(4/3)*RTG_asymmetric_area

The RTG symmetrical design defines
RTG_asymmetric_area = 0 and therefore aPrtg = 0
Any RTG_asymmetric_area would be outside manufacturing tolerances
that perhaps or on the order of mm^2


These half_lives should be considered very accurate

Yes, half life is an intrinsic property of the Pu-238.

The point of the recent analysis was that the radiative model is
consistent with all known data, and there is no need for "new
physics" to explain the so-called Pioneer Anomaly. That doesn't
prove that no new physics exists, but it removes one piece of
evidence.

In
http://arxiv.org/abs/1204.2507v1
a detailed finite element radiative model
was applied to electrical power
with half life of 87.7/4 or 21.9 years
assuming the model daP/dt = -ln(2)(t-t0)/21.9.
The remaining aP 'constant with time' component
was modeled as daP/dt = -ln(2)(t-t0)/87.7
a modeling that can not be physically justified due to Pioneer design.
(A 87.7 year half life changes aP on the order of 20% over Pioneer life
for all intensive purposes represents a constant)
This 'constant with time' component on the order of 7E-8 cm/sec^2
cannot be linked to the internal physical nature of Pioneer
and can truly be considered the Pioneer anomaly
indicating a property of space through which the Pioneers travel.
This recent analysis
http://arxiv.org/abs/1204.2507v1
does not 'remove one piece of evidence'.
but unnecessarily stops investigation in this astrophysical area
at this important time
when 95 percent of the unknown universe is under investigation
as to identity
and all research avenues are needed as tools.

Richard D Saam