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(meteorobs) Excerpts from "CCNet 134/2000 - 18 December 2000"
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 18 December 2000
Date: Mon, 18 Dec 2000 14:24:15 -0000
CCNet 134/2000 - 18 December 2000
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[...]
(7) A SPORADIC ORIGIN FOR THE 29th NOVEMBER DAYLIGHT FIREBALL
Josep M. Trigo <trigo@exp.uji.es>
[...]
(9) CNUCE UNCONTROLLED RE-ENTRY CLASSIFICATION
Luciano Anselmo <luciano.anselmo@cnuce.cnrdot it>
[...]
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* LETTERS TO THE MODERATOR *
============================
(7) A SPORADIC ORIGIN FOR THE 29th NOVEMBER DAYLIGHT FIREBALL
>From Josep M. Trigo <trigo@exp.uji.es>
We would correct an important mistake appeared in a press release published
in CCNET the past December 11th. We suggested that the daylight 29th Nov.
fireball could be associated to the Leonids shower but it was a mistake due
to an incorrectnes on the calculated rise and set times of this radiant. In
fact, although the angular velocity and orientation would be adequate, the
Leonids radiant was a lot of degrees under the horizon when the fireball
appeared!. Considering this fact, our data suggests that this fireball had a
sporadic origin, probably coming from the apex source. Perhaps in next weeks
we can obtain detailed trajectories from other sites
to adjust its approx. radiant.
In connection with this mistake some people ask us on the possibility to see
a fireball when its radiant is under the horizon. It is practically
impossible but, sometimes, very active showers can produce extreme cases of
visible meteors (or fireballs) when its radiant is in or lightly (a few
degrees) under the horizon.
Josep M. Trigo-Rodrmguez
SPANISH PHOTOGRAPHIC METEOR NETWORK (SPMN)
Institut d'Estudis Espacials de Catalunya (IEEC)
Dept. Astronomy & Astrophysics, Univ. of Valencia
Dept. Experimental Sciences, Univ. Jaume I
Dept. Inorganic Chemistry, Univ. Barcelona
SPMN homepage: http://www.spmn.uji.es/
E-mails: trigo@exp.uji.es / jllorca@kripto.qui.ub.es
===========
(9) CNUCE UNCONTROLLED RE-ENTRY CLASSIFICATION
>From Luciano Anselmo <luciano.anselmo@cnuce.cnrdot it>
Dear Benny,
Perhaps you may be interested in a classification scheme of uncontrolled
satellite re-entries (see the attached document), introduced at CNUCE/CNR in
1995, to present the associated risk in a synthetic way.
Sometimes, a quantitative impact risk on the ground for a known spacecraft
may be evaluated, but the fine details of the satellite manufacture and very
complex software codes are needed to obtain accurate results. However, when
such information/tools are not available, the CNUCE classification can
provide a reasonable qualitative guess of the risk for each specific event.
Regards
Luciano Anselmo Phone: +39-050-315-2952
Spaceflight Dynamics Section Fax (G3): +39-050-313-8091
CNUCE Institute Fax (G4): +39-050-313-8092
CNR - Area della Ricerca di Pisa
Via Alfieri 1
Loc. San Cataldo - Ghezzano E-Mail: Luciano.Anselmo@cnuce.cnrdot it
56010 San Giuliano Terme CNUCE URL: http://www.cnuce.pi.cnrdot it/
Pisa - Italy CNR Area URL: http://www.area.pi.cnrdot it/
----------
CNUCE UNCONTROLLED RE-ENTRY CLASSIFICATION
(Space Debris Monitor, No. 4, CNUCE Institute, CNR, Pisa, Italy, April 1995)
Luciano Anselmo
In order to express the associated risk in a synthetic way, the re-entry in
the Earth's atmosphere of uncontrolled space objects is classified in terms
of mass categories and event classes. The re-entry category [M] is defined
by the following relationship:
m
M = Log_10 ---
100
where m is the mass of the space object in kg. Table 1 shows the CNUCE scale
in detail, together with an approximate risk descriptor. At present, the
re-entry events closely monitored are those with M 3 1.6, corresponding to a
space object mass of 4000 kg, or larger.
Table 1
CNUCE UNCONTROLLED RE-ENTRY SCALE
Category Risk
Descriptor
Mass [kg] Scale (M)
100 0 Negligible
1,000 1 Small
10,000 2 Minor
100,000 3 Moderate
1,000,000 4 Substantial
However, the space object mass is not sufficient to characterize a re-entry
event. Therefore, some re-entry classes were defined as well, as presented
in Table 2.
Table 2
CNUCE RE-ENTRY EVENT CLASSES
Re-entry Event Description
Class
Possible nuclear, biological or chemical contamination C
Complete object disintegration in the high atmosphere
D
Fall of large fragments (3 10 cm) on the ground
F
Object able to maintain its structural integrity during the re-entry S
CNUCE CLASSIFICATION EXAMPLES
7 Cosmos 1900: 1.6 CF
7 Salyut 7: 2.6 F
7 FSW-1 5: 0.8 S
7 TSS 1R: 0.8 D
REFERENCES
This note is based on a translation of "Classificazione dei Rientri", Space
Debris Monitor, No. 4, Istituto CNUCE, Consiglio Nazionale delle Ricerche,
Pisa, Italy, April 1995, p. 2.
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