The famous Dr. Steel

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    From:  Daniel Fischer             Submitted:  17 Dec 91 18:39:00  

 Subject:  The famous Dr. Steel on 1     Status:  Public

Received:  No                             Group:  ALIEN (37)

RE: The famous Dr. Steel on 1991 VG [Forwarded]

From: dfi@specklea.mpifr-bonn.mpg.de (Daniel Fischer)

Date: 17 Dec 91 17:39:15 GMT

Organization: Max Planck Institut fuer Radioastronomie

Message-ID: <1991Dec17.173915.29359@mpifr-bonn.mpg.de>

Newsgroups: sci.astro,sci.space,alt.alien.visitors

From DIS@aaocbn.oz.au Tue Dec 17 05:49:11 1991 ...

... did I get the following paper which he asked me to post to the net:

==========================================================================

                A ROCK OR A ROCKET?

On November 6th astronomers operating the Spacewatch telescope at Kitt

Peak in Arizona found what was at first assumed to be a small rocky 

asteroid.  It was given the code-name 1991 VG.  More recent observations

from Chile

have indicated that this body, which raised a flurry in the world's media

when it flew close (on an astronomical scale) by the Earth on December 5th,

may in fact be an old rocket body returning to our planet's vicinity.

Spacewatch, operated by Tom Gehrels, Jim Scotti and David Rabinowitz

(University of Arizona) is a relatively small (91 cm aperture) telescope

which has been fitted with a large CCD array and programmed to search

for objects such as asteroids and comets which approach the Earth.  They do

this by letting the sidereal rotation of the Earth cause the instrument

to scan across

the sky, with the same area being returned to later, and again once more as

a check.  Any objects which have moved between scans are picked up by the

software, and the operator may then make a visual inspection of the data and

calculate a preliminary orbit for the new-found object.  Especially for the

fainter detections many of the orbits turn out to be geocentric, a

piece of man-made debris being indicated.  However some very small asteroids

have been discovered in this way: 1991 BA last January (the closest-ever

observed miss of our planet, at 170,000 km) and 1991 TU in October (at

750,000 km).  1991 VG is the second-closest observed fly-by, at 450,000 km,

or just further away than the Moon.  All three of these objects were estimated

to be about 5--10 metres in size, and are therefore the smallest 

and intrinsically-faintest items ever

observed telescopically above the atmosphere.

However, 1991 VG was soon realized to be in an unusual orbit for an asteroid:

its path is very similar to that of the Earth, being almost circular

(eccentricity 0.08), the size of its orbit just 5\% larger than that of

the Earth (so that it takes just a few weeks longer than a year to circuit

the Sun), and, critically, an extremely small inclination to the ecliptic,

the plane of the Earth's orbit.  The latter parameter has a value

(about a quarter of a degree only) which is consistent with a man-made

spacecraft.  Initial computations by Brian Marsden (Harvard-Smithsonian

Center for Astrophysics) indicated that it might be an upper stage from the

U.S. Centaur rocket which put the German Helios 1 satellite into a

heliocentric orbit in December 1974, since tracing the orbit of 1991 VG

back in time showed a close approach about then.  A Soviet craft

was also a possibility.  However, as better astrometric data for 1991 VG

came in it was possible for its orbit to be improved, and Marsden found

that he could not identify a close approach to the Earth since the

beginning of the space age, and so the `rocket' option was discounted.

Since there are about a billion asteroids of this size or larger believed to

orbit in the inner solar system, the chances are that some of them will have

orbits very similar to the Earth, and in fact these are much more likely

to be detected by telescopes like Spacewatch.  From the opposite point of

view a calculation of the probability of a collision by such an object with

our planet indicates that its lifetime against such an event is only about

250,000 years, which means that it must have arrived in its present orbit

in the astronomically-recent past.  Marsden suggested that it might be

an object which had spent most of its life in a so-called `Trojan' orbit,

having exactly the same orbital period as the Earth but keeping 60 degrees

ahead or behind of the planet at all times, until it recently slipped that

mooring.  Many Trojan asteroids are seen in association with Jupiter, and

in 1990 a Mars Trojan was discovered.

However, close to the fly-by of 1991 VG Richard West (European Southern

Observatory) collected time-resolved images of the object using the Danish

1.54 m telescope in Chile: the path taken at that time was over the South

Pole and therefore out of the reach of most northern telescopes.  He found

that the brightness of 1991 VG varies rapidly and has a period of about 

7--8 minutes, with several extremely bright flashes being detected.  These

are as expected for a rotating, shiny spacecraft which occasionally

renders a specular reflection in the direction of the viewer.  Such a short

period also seems inconsistent with a natural rocky asteroid, since it

is unlikely that such an object of 5--10 m diameter could have a spin

period of less that one hour without flying apart: its cohesive strength would

be too low.  In addition the relative 

brightnesses in different regions of the visible

spectrum were essentially solar, warranting for a colourless object rather

than a reddish asteroidal reflection spectrum.  West concludes that

1991 VG is most likely an artificial object rotating about more than one

axis.

This being the case it opens up a problem for dynamicists: if 1991 VG

is indeed the Centaur rocket body launched in 1974 then how has its orbit

been perturbed so as to bring it back to our vicinity now?  One possibility

is that excess fuel has escaped and therefore had a rocket-effect

without being ignited.  It also seems inevitable that it will also soon

be claimed as being an alien spacecraft left by extraterrestrial visitors,

even though science will undoubtedly be able to provide a plausible

solution.  If it is a rocket then 1991 VG also provides an example of 

mankind's ability to

pollute not only his own planet and immediate space environment, but 

interplanetary space as well: the prevention of such pollution was the

subject of a resolution of the International Astronomical Union at its

General Assembly in Buenos Aires last August.

So is 1991 VG a rock or a rocket?  An answer to this may be

gained over the next week when Steve Ostro (Jet Propulsion Laboratory) 

attempts to get radar echoes from it using the giant radar

at Arecibo (Puerto Rico).  An attempt from Goldstone (California) on

December 12th was unsuccessful.  The radio

reflection properties of metal are very different to those of rock, so

that a spacecraft would give a much stronger echo; its structure would

also affect the returned polarization.  Even then the answer may not

be  definitive since it is known that many asteroids, like meteorites,

are made of nickel-iron.

Is it so unlikely that a spacecraft would come back to Earth?  In fact,

using the orbit of 1991 VG prior to the recent encounter (a = 1.05 AU,

e = 0.075, i = 0.22 deg) the chance of this object hitting the Earth

converts to a lifetime of only 250,000 years (other Earth-crossing asteroids

have lifetimes more like 100 million years).  Increasing the cross-section

to that having a radius equal to the miss distance of 450,000 km implies

that an object in such an orbit would fly-by the Earth by that distance or

less once per 20 years or so: pretty frequent.

Duncan Steel,

Anglo-Australian Observatory,

Coonabarabran, NSW.

From DIS@aaocbn.oz.au Tue Dec 17 13:20:36 1991

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Date: Tue, 17 Dec 91 23:17 EST

From: DIS@aaocbn.oz.au

Subject: NOT HELIOS 1?

To: p515dfi@mpirbn.uucp

X-Vms-To: IN%"p515dfi@c1a.mpifr-bonn.mpg.de"

Status: R

                                               1991 December 17th.

Dear Daniel,

Thanks for the message.  I believe that Brian Marsden identified a

COSMOS craft from earlier in 1974 as a possibility, but at that time

he was looking for returns around that time (prior to a good orbit for

1991 VG being available).  Now no return to the Earth's vicinity is

found purely from gravitation: some have looked at the possibilities

of radiation pressure for a large hollow object (or a panel), or fuel

escaping.  It is not possible, it seems, to  narrow down to a candidate

if the year (even) when the object was last close to the Earth is not known.

I believe that the Helios 1 booster is still listed in the Satellite

Situation Report (i.e. return to Earth's surface NOT indicated) although

I will need to check on that tomorrow.

Duncan Steel

=====================================================================

  

Dr Duncan Steel,

Anglo-Australian Observatory,

Private Bag,

Coonabarabran, NSW 2357,

Australia.

 

"dis@aaocbn.oz.au" or "dis@aaocbn.anu.edu.au" or "PSI%AAOCBN.OZ.AU::DIS"

 

Telephone:  +61 (0)68 426 314 (AEST is 10 hours ahead of GMT/UT)

            +61 (0)68 426 220 (home)

Fax:        +61 (0)68 842 298

 

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