Going Around, Coming Around: Returning Interplanetary 'Space Debris'

See http://www.fatemag.com/2005_11art1.html for the UFO view.

I personally favor SLA panels as the culprits,
throwing in a significant 'solar sailing' to confuse
the ballistic track-back calculations.

Jim Oberg wrote:

See http://www.fatemag.com/2005_11art1.html for the UFO view.

I personally favor SLA panels as the culprits,
throwing in a significant 'solar sailing' to confuse
the ballistic track-back calculations.




The big problem with the reasoning of that article is the way they are
estimating the size of objects based on their brightness- they see the
object, then give a size estimate based on the average albedo range of
asteroids.
But it the object is a rocket stage the albedo is probably going to be
far higher as it is probably white or silver in coloration (or in the
case of some of the Soviet ones green or gray) and what you are looking
at is a lot, lot, smaller than what you think it is.
What you would want to do is examine the reflection spectrum of the
object and determine what the surface you are seeing the sunlight
reflected off of is made of....IIRC, didn't one of these mystery objects
show that it was covered in titanium-based white paint when checked out
in this way, and that pretty well nailed it down as a S-IVB stage from
one of the Apollo flights?

Pat

In message , Pat Flannery
writes


Jim Oberg wrote:

See http://www.fatemag.com/2005_11art1.html for the UFO view.

I personally favor SLA panels as the culprits,
throwing in a significant 'solar sailing' to confuse
the ballistic track-back calculations.



The big problem with the reasoning of that article is the way they are
estimating the size of objects based on their brightness- they see the
object, then give a size estimate based on the average albedo range of
asteroids.
But it the object is a rocket stage the albedo is probably going to be
far higher as it is probably white or silver in coloration (or in the
case of some of the Soviet ones green or gray) and what you are looking
at is a lot, lot, smaller than what you think it is.
What you would want to do is examine the reflection spectrum of the
object and determine what the surface you are seeing the sunlight
reflected off of is made of....IIRC, didn't one of these mystery
objects show that it was covered in titanium-based white paint when
checked out in this way, and that pretty well nailed it down as a S-IVB
stage from one of the Apollo flights?

Pat
J002E3 is thought to be Apollo 12's S-IVB
http://www.space.com/scienceastronomy/moon_impact_020916.html
Isn't there a LM ascent stage in heliocentric orbit, too?

Jonathan Silverlight wrote:

J002E3 is thought to be Apollo 12's S-IVB
http://www.space.com/scienceastronomy/moon_impact_020916.html
Isn't there a LM ascent stage in heliocentric orbit, too?


Apollo 10's "Snoopy" is in solar orbit.

Pat

That article mentions reactivating the old ALSEPS, in so far as I know
thats impossible

In message . com,
writes
That article mentions reactivating the old ALSEPS, in so far as I know
thats impossible


It's a bit optimistic - they were on their last legs when they were
turned off in the 1970s and they've had a lot of heat-cold cycles since
then!
I don't have time to check now, but isn't it thought that the rocket
_didn't_ crash, but it's in an orbit that causes it to leave the
Earth-Moon system and to come back in about 30 years?

"Jim Oberg" wrote in message
...
See http://www.fatemag.com/2005_11art1.html for the UFO view.

I personally favor SLA panels as the culprits,
throwing in a significant 'solar sailing' to confuse
the ballistic track-back calculations.

My analysis of published brightness observations of 1991 VG reveals a
standard magnitude of 6.3 (1000 km range, 90 deg phase angle), which is
about 3 magnitudes fainter than expected of an S-IVB stage:

http://satobs.org/seesat_ref/1991_VG/1991_VG.jpg

If 1991 VG is space hardware of Earthly origin, then its standard magnitude
is indicative of moderate size. For example, it is about as bright as the
current generation of DMSP and NOAA LEO weather satellites, which are about
7 m long and 2 m in diameter. It is about 1 magnitude fainter than a typical
Agena upper stage, which is about 6 m long and 1.5 m in diameter.

The S-IVB stage is 18.7 m long and 6.6 m in diameter, which I estimate would
have resulted in a standard magnitude of about 3. Skylab, a heavily modified
S-IVB had an observed standard magnitude of about 1.7, but it was a good
deal longer than a plain S-IVB, so std mag 3 seems about right for the
latter.

The SLA was 8.5 m high, 3.9 m dia at the top, and 6.6 m dia at the bottom.
Each panel is 8.6 m long, and its cross-section is 2.8 m wide at the top and
4.7 m wide at the bottom. It seems too large to account for 1991 VG, but its
shape is complex, so detailed modeling of its optical characteristics would
be necessary to be certain. (Beyond my ability.)

Ted Molczan

Thanks for sharing these valuable insights on outerspacesights.



"Ted Molczan" wrote in message
...
"Jim Oberg" wrote in message
...
See http://www.fatemag.com/2005_11art1.html for the UFO view.

I personally favor SLA panels as the culprits,
throwing in a significant 'solar sailing' to confuse
the ballistic track-back calculations.

My analysis of published brightness observations of 1991 VG reveals a
standard magnitude of 6.3 (1000 km range, 90 deg phase angle), which is
about 3 magnitudes fainter than expected of an S-IVB stage:

http://satobs.org/seesat_ref/1991_VG/1991_VG.jpg

If 1991 VG is space hardware of Earthly origin, then its standard
magnitude is indicative of moderate size. For example, it is about as
bright as the current generation of DMSP and NOAA LEO weather satellites,
which are about 7 m long and 2 m in diameter. It is about 1 magnitude
fainter than a typical Agena upper stage, which is about 6 m long and 1.5
m in diameter.

The S-IVB stage is 18.7 m long and 6.6 m in diameter, which I estimate
would have resulted in a standard magnitude of about 3. Skylab, a heavily
modified S-IVB had an observed standard magnitude of about 1.7, but it was
a good deal longer than a plain S-IVB, so std mag 3 seems about right for
the latter.

The SLA was 8.5 m high, 3.9 m dia at the top, and 6.6 m dia at the bottom.
Each panel is 8.6 m long, and its cross-section is 2.8 m wide at the top
and 4.7 m wide at the bottom. It seems too large to account for 1991 VG,
but its shape is complex, so detailed modeling of its optical
characteristics would be necessary to be certain. (Beyond my ability.)

Ted Molczan

"Ted Molczan" wrote in message
...
"Jim Oberg" wrote in message
...
See http://www.fatemag.com/2005_11art1.html for the UFO view.

I personally favor SLA panels as the culprits,
throwing in a significant 'solar sailing' to confuse
the ballistic track-back calculations.

My analysis of published brightness observations of 1991 VG reveals a
standard magnitude of 6.3 (1000 km range, 90 deg phase angle), which is
about 3 magnitudes fainter than expected of an S-IVB stage:

http://satobs.org/seesat_ref/1991_VG/1991_VG.jpg

If 1991 VG is space hardware of Earthly origin, then its standard
magnitude is indicative of moderate size. For example, it is about as
bright as the current generation of DMSP and NOAA LEO weather satellites,
which are about 7 m long and 2 m in diameter. It is about 1 magnitude
fainter than a typical Agena upper stage, which is about 6 m long and 1.5
m in diameter.

The S-IVB stage is 18.7 m long and 6.6 m in diameter, which I estimate
would have resulted in a standard magnitude of about 3. Skylab, a heavily
modified S-IVB had an observed standard magnitude of about 1.7, but it was
a good deal longer than a plain S-IVB, so std mag 3 seems about right for
the latter.

The SLA was 8.5 m high, 3.9 m dia at the top, and 6.6 m dia at the bottom.
Each panel is 8.6 m long, and its cross-section is 2.8 m wide at the top
and 4.7 m wide at the bottom. It seems too large to account for 1991 VG,
but its shape is complex, so detailed modeling of its optical
characteristics would be necessary to be certain. (Beyond my ability.)

I should add that the above SLA cross-sections are its largest.Its smallest
are about 0.6 m at the top and 1 m at the bottom. On average, its dimensions
are about 8.6 m x 3.8 m x 0.8 m, which I estimate would result in a standard
magnitude of about 5. This kind of estimate is accurate to within about 1
magnitude, so it is similar enough to 1991 VG to be interesting.

As for the effect of SRP (solar radiation pressure), each SLA panel's mass
is about 460 kg, resulting in an area to mass ratio of about 0.07 m^2/kg
through the largest cross-section. The comparable value for an S-IVB stage
is about 0.01 m^2/kg, so the SLA panels seem likely to be much more strongly
affected by SRP than an S-IVB. I do not know whether or not the absolute
difference in SRP would be sufficient for an SLA to account for 1991 VG's
orbit. A more fundemental question: could any of the SLA panels have escaped
their highly elliptical Earth orbit?

Ted Molczan

"Ted Molczan" wrote:

A more fundemental question: could any of the SLA panels have escaped
their highly elliptical Earth orbit?

Good catch. I'd been thinking that the SLA panels would have behaved
like the stage they came from - except the panels are released right
after TLI, which for all flights mean a free return trajectory at that
point.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL