Дата: 03 февраля 1998 (1998-02-03)
От: Alexander Bondugin
Тема: Cassini Update - January 30, 1998
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Cassini Significant Event Report
For Week Ending 01/30/98
MSO Significant Events input for week of Friday 01/23 through Thursday 01/29:
Spacecraft Status:
The Cassini spacecraft is presently traveling at a speed of approximately
120,000 kilometers/hour (~75,000 mph)
and has traveled approximately 260 million kilometers (~163 million miles)
since launch last October 15.
The most recent Spacecraft status is from the DSN tracking pass on
Thursday, 01/29, over Goldstone. The Cassini
spacecraft is in an excellent state of health and is operating nominally,
with the C6 sequence executing onboard.
Inertial attitude control is being maintained using the spacecraft's
hydrazine thrusters (RCS system). The spacecraft
continues flying in a High Gain Antenna-to-Sun attitude. It will maintain
the HGA-to-Sun attitude, except for
planned trajectory correction maneuvers, for the first 14 months of flight.
Communication with Earth during early cruise is via one of the spacecraft's
two low-gain antennas; the antenna
selected depends on the relative geometry of the Sun, Earth and the
spacecraft. The downlink telemetry rate is
presently 40 bps.
Spacecraft Activity Summary:
From Friday, 01/23, through Saturday, 01/24, there were no changes in
spacecraft configuration.
On Sunday, 01/25, the Off-Sun Time Constraint was set for the C6 sequence.
This limit, based on the range from
the spacecraft to the sun, is adjusted approximately every two months, for
thermal reasons, as Cassini travels along
its interplanetary trajectory.
From Monday, 01/26, through Tuesday, 01/27, there were no changes in
spacecraft configuration.
On Wednesday, 01/28, the Solid State Recorder (SSR) record and playback
pointers were reset, according to plan.
This housekeeping activity, done approximately weekly, maximizes the amount
of time that recorded engineering
data is available for playback to the ground should an anomaly occur on the
spacecraft.
On Thursday, 01/29, the Articulated Reaction Wheel Mechanism (ARWM) was
unlatched successfully, according
to plan. The Articulated Reaction Wheel is a spare device which can be
aligned with the appropriate spacecraft axis,
should it be needed to replace a failed prime unit later in the mission.
(Thrusters, rather than reaction wheels, are
used during early cruise for controlling spacecraft attitude.)
Also on Thursday, the spacecraft's active vector was updated in the
Inertial Vector Table. This housekeeping
activity, which updates the vectors between the spacecraft and the Sun,
Earth, and other bodies, is performed every
few months.
Upcoming spacecraft events:
Events for the week of 01/30 through 02/05 include: a reset of the SSR
pointers (02/03), and an SSR Flight
Software Partition maintenance activity (02/02 and 02/03).
DSN Coverage:
For the next month or so, there will be an increase in DSN coverage for
Navigation purposes, as the second and
third Trajectory Correction Maneuvers (TCMs) approach. Over the past week
Cassini had 4 track periods (01/22,
01/25,01/27, 01/28). In the coming week there will be 8 DSN passes, Friday
to Saturday (01/30-01/31), 3
additional passes on Saturday, (01/31), Monday, (02/02), Tuesday, (02/03),
Wednesday, (02/04), and Thursday
(02/05).
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Дата: 03 февраля 1998 (1998-02-03)
От: Alexander Bondugin
Тема: Mars Surveyor 98 Update - February 1, 1998
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1998 MARS SURVEYOR PROJECT STATUS REPORT
FEBRUARY 1, 1998
John McNamee
Mars Surveyor 98 Project Manager
The 1998 Mars Surveyor orbiter is 312 days from launch and the lander is 335
days from launch (as of 2/1/98). The following provides a summary
description of the current Project status as of February 1, 1998.
Orbiter Integration and Test
The orbiter spacecraft has been fully assembled and checked out
functionally. Major tests successfully completed include the Deep Space
Network (DSN) Compatibility Test, the Bus Functional Test (BFT), Mission
System Test #1 (MST #1), and the modal survey. Descriptions of the Bus
Functional Test and the Mission System Test are included on the attachment.
The Pressure Modulator InfraRed Radiometer (PMIRR) flight instrument is
integrated and all interfaces and functionality have been verified. The Mars
Color Imager (MARCI) electrical interface unit (i.e., electrical equivalent
camera less optics) is integrated and interfaces are verified. The flight
camera is on schedule for integration in February prior to thermal vacuum
testing. The refurbishment of the orbiter flight processor and power
distribution and drive unit ATLO Test Units is complete and all orbiter
electronics are in their final flight configuration. The orbiter is in the
Reverberant Acoustics Lab (RAL) at Lockheed Martin in Denver and is being
prepared for acoustic testing.
The current schedule for the orbiter is:
2/17/98 - Start Acoustic Test
2/26/98 - Start ElectroMagnetic Interference/Compatibility Tests (EMI/EMC)
4/3/98 - Start Thermal Vacuum Testing
9/3/98 - Ship to Kennedy Space Center (KSC)
12/10/98 - Launch
The schedule maintains 71 days of margin prior to shipment and 20 days of
margin at KSC. Significant mass margin for the orbiter exists with
essentially all elements weighed. Recent orbit insertion analyses indicate
that by utilizing just a portion of the expected margin at launch to further
fill the hydrazine and ox tanks will allow the orbiter to insert directly
into a 15 hour or shorter period orbit. This provides significant margin
against aerobraking uncertainties and increases the probability that the
orbiter will be in place to support the lander at lander arrival.
Lander Integration and Test
The lander spacecraft is fully integrated electrically and all interfaces
have been verified. Major tests successfully completed include the Deep
Space Network (DSN) Compatibility Test and the Bus Functional Test (BFT). In
addition, the lander to orbiter UHF relay was tested successfully using both
spacecraft in the high bay at LMA. Installation of the lander science
payload is in process. The flight Lidar, Meteorology package, Surface Stereo
Imager, Robotic Arm, and Robotic Arm Camera, have been installed on the
spacecraft and functional testing is in progress. The flight Mars Descent
Imager will be installed next week and the flight Thermal and Evolved Gas
Analyzer experiment will be installed in June prior to landed configuration
Thermal Balance testing. The lander is in the high bay facility at Lockheed
Martin and will be moved to the Reverberant Acoustics Lab in March for the
start of environmental testing.
The current schedule for the lander is:
3/21/98 - Start Acoustic Test
3/31/98 - Start EMI/EMC Tests
5/4/98 - Start Cruise Thermal Vacuum Test
6/23/98 - Start Landed Thermal Balance Test
10/14/98 - Ship lander to KSC
1/3/99 - Launch
The current lander schedule maintains 41 days of margin prior to shipment
with 20 days of margin at KSC.
Significant mass margin for the lander exists with full tanks and most
elements weighed. In all likelihood the lander will be well below the
maximum design mass providing significant margin against launch vehicle
performance shortfalls, entry heating limits, parachute deployment limits,
and landing site elevation uncertainties.
Bus Functional Test
The purpose of the Bus Functional Test (BFT) is to verify the end-to-end
core command and control functionality in an integrated vehicle
configuration. The major parts of the test include complete testing of
uplink and downlink command and data capability (data rates, file sizes,
etc.), non-volatile memory read and write functionality, and test of the
Command and Data Handling Module Interface Card (C-MIC) functions which
control heartbeat, fault recovery, and vehicle state. Also, end-to-end
phasing of the Attitude Control Subsystem from sensor inputs through
actuator commands is tested in a quasi-closed loop manner. The BFT is
conducted on both A&B sides of the hardware. Some miscellaneous functions
also will be verified as part of the BFT, including voltage drop
verification throughout the longest harness cable run, launch event
detection logic, and critical command aliveness functions to be used in
later tests. The BFT represents a major milestone in the integration and
test phase of development.
Mission System Test
The Mission System Tests (MST), which consist of the System Aliveness Test
(SAT), the Mission Profile Test (MPT), and Sequence Verification Test (SVT),
are run before and after each environmental test and after the spacecraft is
shipped to KSC. The SAT is a standard, multiple use test that will be run as
the first part of each MST. It's purpose is to demonstrate continuity of the
electrical signal and power paths, meaning that all components are
operational and able to receive commands and send telemetry. The
significance of this first SAT is in demonstrating that the spacecraft has
achieved a fully integrated system of software and hardware and to establish
the baseline data for subsequent runs of the SAT. Unlike earlier subsystem
level tests on the spacecraft, this end to end test was performed without
the aid of ground support equipment and thereby establishes a higher level
of verification of the hardware / software interfaces. Orbiter MST #1 also
includes a limited mission profile test (MPT).
For more information on the Mars Surveyor 98 program,
please visit the Mars Surveyor 98 home page:
http://mars.jpl.nasa.gov/msp98/
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Дата: 03 февраля 1998 (1998-02-03)
От: Alexander Bondugin
Тема: Cambridge Conference Digest - February 2, 1998 [1/2]
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CAMBRIDGE CONFERENCE DIGEST, 02/02/98
(1) RAMPINO'S NEW PAPER ON THE SHIVA HYPOTHESIS
(2) LOOKING AT ASTEROID 1620 GEOGRAPHER
(3) THE NUMBER DENSITY OF MAIN-BELT ASTEROIDS
(1) RAMPINO'S NEW PAPER ON THE SHIVA HYPOTHESIS
From: Michael Rampino <rampin@is3.nyu.edu> wrote:
Benny:
Here is a summary of the Shiva article:
The Shiva Hypothesis: Impacts, Mass Extinctions, and the Galaxy
Michael R. Rampino
NASA, Goddard Institute for Space Studies
New York, NY 10025
and New York University
New York, NY 10003
The discovery by Walter and Luis Alvarez and their colleagues at the
University of California at Berkeley of anomalous concentrations of
the rare element iridium in a thin clay layer at at the
Cretaceous/Tertiary (K/T) boundary in a rock outcrop near the town
of Gubbio, Italy, almost twenty years ago, triggered an upheaval in
the geological sciences. The intervening years have seen a
remarkable confirmation of the Alvarez group's hypothesis that the
unusual traces of iridium were the fingerprint of dust created by
the collision of a huge asteroid or comet with the Earth, and that
the occurrence of the tell-tale clay layer at the precise time that
the dinosaurs and some 75% of life on the planet disappeared was no
mere coincidence. This proposal culminated in the discovery of a
giant 65-million year old impact crater in the Yucatan, widespread
evidence of massive tsunami in the Caribbean/Gulf of Mexico region
at the same time, and spectacular deposits derived from storms of
rock debris blasted out of the crater that were investigated during
recent Planetary Society expeditions to Belize in Central America.
The convergence of evidence for impact at the Cretaceous/Tertiary
(K/T) boundary has led to renewed interest in mass extinctions and a
recognition of their importance as a major driving force in the
evolution of life on Earth. The K/T mass extinction is but one of a
number of mass extinction events recorded in the fossil record, and
in fact was not the most severe. Could impacts be responsible for
the recurrent mass extinctions seen in the geologic record? A few
years ago such a suggestion would have seemed far-fetched, but
recent evidence is converging on the conclusion that mass
extinctions coincided with comet or asteroid impacts, and that
periodic comet showers, triggered by the Solar System's motions
through the Milky Way Galaxy may provide a general theory to explain
impact-related mass extinctions. The cyclic extinctions are followed
by explosive evolution of the surviving species that re-filled the
many life niches emptied by the global catastrophe, so we have named
this idea the "Shiva Hypothesis", after the Hindu deity of cyclic
destruction and renewal.
One of the most intriguing findings in the study of extinctions has
been that of a possible cycle of these mass die offs. Analyses of
the extinction record by Dave Raup and Jack Sepkoski revealed an
underlying cycle of about 26 million years in the mass extinctions
of the last 250 million years (the best-dated part of the record),
and recent work on an improved and better dated extinction data base
with Bruce Haggerty at NYU reveals that a cycle of 26 to 30 million
years persisted through the entire 540 million year record. Raup and
Sepkoski's original findings prompted Richard Stothers of NASA's
Goddard Institute for Space Studies and me, and independently Walter
Alvarez and Rich Muller at Berkeley, to analyze the record of impact
craters, and we detected a similar cycle in the occurrence of large
impacts on the Earth. Furthermore, it seems that clusters of
craters of similar ages are closely correlated with the mass
extinction episodes. These results suggest that many impact events
on Earth were part of a periodic, most likely from showers of
comets, leading to periodic mass extinctions.
If a 26 or 30 million year periodicity in mass extinctions and
impacts is real, then it may be related to a known astronomical
cycle-the motion of the Solar System up-and-down through the plane
of the disk-shaped Milky Way Galaxy. Astrophysicists have determined
that the Solar System revolves around the center of the Galaxy about
once every 220 million years, and as it does so the Solar System
bobs up and down like a horse on a carrousel through the dense,
central portion of the galactic disk. In this cycle, the Sun and
planets pass through the dense region packed with stars and clouds
of interstellar gas and dust every 26 to 30 million years.
Stothers and I first suggested that passage of the Solar System
through the galactic plane could lead to gravitational disturbance
of some of the trillions of comets that orbit the Sun in the
so-called Oort Cloud, resulting in periodic showers of comets in the
inner Solar System. Recent work by astrophysicist John Matese and
colleagues at the University of Southwestern Louisiana has confirmed
that the pull of the combined mass of the material in the galactic
disk is sufficient to induce a hail of comets during our passage
though the central plane. Like Shiva, the Hindu Destroyer/Creator,
the cyclic impacts bring an end to one world, and allow the
beginning of a new one. With the Chicxulub impact 65 million years
ago, the Mesozoic world, populated by giant dinosaurs and flying
reptiles, gave way to the modern world of mammals and birds.
This cycle of doom has relevance to the present-day impact hazard,
as the Solar System passed through the Galaxy's central plane in the
last few million years, and by some accounts a barrage of comets
recently dislodged from the Oort Cloud should be approaching the
planets now. A few impact/extinction events may be out of phase with
the 30 million year galactic cycle, but it is expected that some
comet and asteroid impacts would occur independently of the periodic
perturbation of Oort Cloud comets.
These exciting new findings from astronomy, geology, and the
history of life point to a general theory relating mass extinctions,
and perhaps other geologic events, to the impacts of large comets
and asteroids on the Earth. In this view, mass extinctions of life
occur as discrete pulses, marked by abrupt mass mortality on land
and in the oceans, decimation of plant life, major environmental
perturbations shown by changes in carbon isotopes, and climatic
changes shown by oxygen-isotope shifts. The mass extinctions are
commonly followed by a period of rapid evolution of surviving
species, with newcomers filling the many niches abandoned en-masse
by the victims of global disaster.
In a growing number of cases, the times of mass extinction have
been found to be marked by evidence of great asteroid or comet
impacts, in the form of large, dated impact craters, and widespread
layers rich in iridium, shocked minerals, and glassy microtektites.
It may be that all of the major, and many of the minor, breaks in
the geologic record were caused by impacts of objects of various
sizes. The underlying periodicity of about 30 million years that
seems to pervade the record of these events may well be related to
showers of comets from the Oort Cloud triggered as the Solar System
passes through the galactic plane. Thus the impact hypothesis of
mass extinctions, which began with study of a thin clay layer at
Gubbio, has grown in theoretical and observational support,
culminating in an important unifying concept in the earth sciences.
Michael R. Rampino
Earth & Environmental Science Program
New York University
100 Washington Square East
New York, NY 10003
(212) 998-3743 Office Phone
(212) 995-3820 Office Fax
(212) 242-0929 Home Phone
(212) 255-2739 Home Fax
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Дата: 03 февраля 1998 (1998-02-03)
От: Alexander Bondugin
Тема: Cambridge Conference Digest - February 2, 1998 [2/2]
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(2) LOOKING AT ASTEROID 1620 GEOGRAPHER
V.V. Prokofeva*), L.G. Karachkina and V.P. Tarashchuk:
Investigations of oscillations in the brightness of Asteroid 1620
geographer during its approach to the Earth in 1994. ASTRONOMY
LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS, 1997, Vol.23,
No.6, pp.758-767
*) UKRAINIAN ACADEMY OF SCIENCE, CRIMEAN ASTROPHYS OBSERV, P-O
NAUCHNYI, UA-334413 CRIMEA,UKRAINE
Comprehensive investigations were conducted of Asteroid 1620
Geographer during its approach to the Earth in 1994. A frequency
analysis of fine photometric effects and oscillations in its
brightness was performed using data from a catalog of photometric
observations of asteroids. This analysis confirms the monolithic
nature of the very elongated body of the asteroid. In addition to
the known rotation period of the asteroid, periods of 0(d).8 and
2(d).8 are detected, as well as multiples of these periods. The
observed periodicity suggests that the first of these periods is
associated with free precession of the rotation axis of the
asteroid, while the second is due to forced precession with
precession angle 3 degrees +/- 1 degrees. The free precession could
have arisen either during the formation of the asteroid or during a
collision with another body. The presence of forced precession
and the fact that Geographer is associated with a meteor shower
is consistent with the possible existence of modest-sized
companions. Copyright 1998, Institute for Scientific Information Inc.
(2) DID COSMIC IMPACT HIT EARLY CHINESE?
S.L. Guo*), W. Huang, X.H. Hao and B.L. Chen: Fission track dating
of ancient man site in Baise, China, and its significances in space
research, paleomagnetism and stratigraphy. RADIATION MEASUREMENTS,
1997, Vol.28, No.1-6 SISI, pp.565-570
*) INSTITUE OF ATOMIC ENERGY, POB 275 96, BEIJING 102413, PEOPLES
REPUBLIC OF CHINA
A large number of artifacts (stone tools) have been discovered in
Baise (Bose), Guangxi, China in recent years. They show that ancient
man were living in the south of China during very ancient times.
During excavation, tektites were discovered in the same layer of
deposits as the stone tools. The structure of the layers of deposits
in this site was never disturbed, which is the evidence that the
stone tools were left behind by the ancient man at the time when the
tektites fell on the earth, which were slowly covered over by layers
of deposits. Fission track dating has been carried out on tektites.
The age of the tektites is 0.732 +/- 0.039 Ma, which is also the age
of the ancient man in Baise, Guangxi, China. The annealing degree of
spontaneous fission tracks in the tektite was investigated by
measuring track diameters. A correction of age for track fading
has been made by track diameter technique. According to current
understanding, tektites were formed by the impact of falling
asteroids or comets on the earth's surface. The dating shows that a
big impact occurred on the earth 0.732 Ma ago. The coincidence of
the age of the tektites with the age of geomagnetic polarity
reversal (similar to 0.73 Ma) from the Matuyama Epoch to the Brunhes
Epoch proposes a plausible explanation that the possible cause of
the geomagnetic polarity reversal is due to the big impact of space
objects falling onto the earth. The result of the dating also set up
a standard for inferring the ages of the deposits in South China as
well as in South-East Asia where laterite (red soil) deposits exist
in the entire region. Copyright 1998, Institute for Scientific Information Inc.
(3) THE NUMBER DENSITY OF MAIN-BELT ASTEROIDS
C.I. Lagerkvist and J.S.V. Lagerros: The number density of main-belt
asteroids. ASTRONOMISCHE NACHRICHTEN, 1997, Vol.318, No.6,
pp.391-393
ASTRONOMICAL OBSERVATORY, BOX 515, S-75120 UPPSALA, SWEDEN
In this paper we have studied how the number density of asteroids
varies as a function of the mean distance from the sun.
Copyright 1998, Institute for Scientific Information Inc.
THE CAMBRIDGE-CONFERENCE NETWORK
The Cambridge-Conference List is a scholarly electronic network
organised by Dr Benny J Peiser at Liverpool John Moores University,
United Kingdom. It is the aim of this international network to
disseminate the latest information and research findings related
to i) geological and historical neo-catastrophism, ii) NEO research
and the hazards to civilisation due to comets and asteroids, and
iii) the development of a planetary civilisation capable of
protecting itself against cosmic disasters. For further information
about this network and how to subscribe, please contact
Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on the Cambridge-Conference Network is for
scholarly and educational use only. The attached information may
not be copied or reproduced for any other purposes without prior
permission of the copyright holders.
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