Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Lunar Prospector Update - March 18, 1998
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Lunar Prospector Status Report #25
March 18, 1998 - 7:00 p.m. EST (4:00 p.m. PST)
The Lunar Prospector spacecraft continues to
perform nearly flawlessly, and all instruments are
collecting good data, according to Mission Control
at NASA's Ames Research Center. On the evening of
Thurs., March 12 (PST), the Moon (and the
spacecraft circling it) were participant to a
penumbral lunar eclipse, in which sunlight (shining
on the Moon) was partially blocked by the
positioning of the Earth relative to the Sun. In
general, a lunar eclipse takes place when the Moon
falls -- either partially or entirely -- into the
Earth's shadow. However, during what's called a
"penumbral" lunar eclipse, in which the Moon enters
an only partially darkened region of the Earth's
shadow (called the penumbra), the entire Moon is
thus only partially shadowed, dimming the lunar
surface, and consequently, diminishing solar array
current on an orbiting spacecraft. This is in
contrast to a "partial total" lunar eclipse, when
only a section of the Moon falls into the Earth's
completely shadowed region (called the umbra),
causing that wedge of the Moon to be completely
blocked from sunlight. (See Lunar Prospector Status
Report #21 for a diagram depicting penumbral lunar
eclipses). During the March 12 penumbral eclipse,
mission controllers noted a predictable decrease in
solar array current. In addition, Prospector's
battery showed a slight discharge before the
spacecraft entered its usual 46-minute eclipse
while traversing the night side of the Moon.
Recharge following the eclipse was nominal.
----------------------------------------------------
The current state of the vehicle (as of 4:00 p.m.
(PST) on Wed., March 18, 1998), according to
Mission Operations Manager Marcie Smith, is as
follows:
General
Spacecraft Orbit Number: 797
Data Downlink Rate: 3600 bps
Spin Rate: 11.95 rpm
Spin Axis Altitude: (see below)
Trajectory
Periselene: 84 km
Aposelene: 115 km
Period: 118 minutes
Inclination: 90.4 degrees
Occultations: 40 minutes in duration
Eclipses: 46 minutes in duration
----------------------------------------------------
On Fri., March 13 (PST), mission controllers reset
the spacecraft's spin axis approximately 2 degrees,
to position the Sun just above the top part of the
spacecraft, for reasons of thermal control (since
the booms are located on the bottom part of the
spacecraft, they could potentially shadow some of
the solar panels if the Sun were shining on the
bottom of the spacecraft).. Also on that day,
controllers trimmed the spin rate, in order to
correct for small changes which had perturbed it
during the orbit trim maneuver performed a week
earlier. The precise command timeline was as
follows:
Fri., March 13, 12:00 p.m. (PST)
Thruster heaters on
Fri., March 13, 12:04 p.m. (PST)
Maneuver parameters loaded
Fri., March 13, 12:26 p.m. (PST)
Thruster A1 and A4 fired (13 pulses) to adjust spin
axis 1.7 degrees
Fri., March 13, 12:31 p.m. (PST)
Thruster heaters on
Fri., March 13, 12:40 p.m. (PST)
Maneuver parameters loaded
Fri., March 13, 12:50 p.m. (PST)
Thruster T1 fired for 0.81 seconds
Fri., March 13, 12:51 p.m. (PST)
Thruster parameters resest
Mission controllers are still investigating the
results of the spin axis re-orientation by
reviewing spacecraft attitude (positioning) data
both before and after the maneuver. The spin trim
was exactly on target, adjusting the spin rate from
12.17 rpm to 11.95 rpm.
Alison Davis
Lunar Prospector Mission Office
NASA Ames Research Center
Moffett Field, Calif. 94035
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=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Cassini Update - March 20, 1998
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Cassini Significant Event Report
For Week Ending 03/20/98
Spacecraft Status:
The Cassini spacecraft is presently traveling at a speed of approximately
142,000 kilometers/hour (~88,000 mph) relative to the sun and has traveled
approximately 413 million kilometers (~257 million miles) since launch on
October 15, 1997.
The most recent Spacecraft status is from the DSN tracking pass on Thursday,
03/19, over Madrid. The Cassini spacecraft is in an excellent state of
health and is operating nominally.
The C6 sequence activities concluded Sunday, 03/15. The C7 sequence
activities began on Sunday, as planned. The C7 sequence will run through
Sunday, May 10.
Inertial attitude control is being maintained using the spacecraft's
hydrazine thrusters (RCS system). The spacecraft continues to fly 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:
On Friday, 03/13, and Saturday, 03/14, there were no changes in spacecraft
configuration.
On Sunday, 03/15, the two 44 Watt Infrared Optics decontamination heaters of
the Visual and Infrared Mapping Spectrometer (VIMS) instrument were turned
off, the requirement having been met to operate these heaters for the first
150 days of flight. These heaters have served to keep spacecraft outgassing
products, which decrease during the first few months of flight, from
accumulating on otherwise cold optical and radiative surfaces of the VIMS
instrument. Two lower power VIMS heaters were left on, continuing the
decontamination for the instrument at a lesser level.
On Monday, 03/16, there were no changes in spacecraft configuration.
On Tuesday, 03/17, 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.
Also on Tuesday, and extending into Wednesday, 3/18, the SRU-B
Decontamination mini-sequence was uplinked and executed. This activity heats
the stellar reference unit (SRU) radiator to eliminate any contamination
that may have accumulated early in flight. Following the heating period, the
radiator is allowed to cool; star data is then collected using the SRU to
verify proper functionality. Although both activities executed as planned,
the radiator heating on Tuesday fell short of the expected temperature; this
result is being analyzed by the thermal engineers. Star data was
successfully collected on Wednesday and is presently being analyzed. No
changes are needed to the upcoming SRU decontamination activity for SRU-A
(scheduled for 3/24 and 3/25).
Also on Wednesday, the now standard SSR Flight Software Partition
maintenance activity was performed. This activity repairs any SSR double bit
errors (DBEs) which have occurred in the code-containing portions of the
Flight Software partitions during the preceding period.
On Thursday, 03/19, there were no changes in spacecraft configuration.
Upcoming events:
Events for the week of 03/20 through 03/26 include: SSR Pointer reset
(03/20), AACS Mass Properties MRO prior to TCM #3 (03/24), uplink and
execution of SRU-A Decontamination (03/24 - 03/25), SSR Pointer reset
(03/26), and Huygens Probe Check-out #2 (03/26).
DSN Coverage:
Over the past week Cassini had 10 DSN tracks occurring daily from Friday
(03/13)through Thursday (03/19). In the coming week there will be 8 DSN
passes.
Science Office Activity Summary:
The last Cassini Facility Instrument Letter of Agreement has now been signed
by the Cassini Radio Science Team Leader and the Cassini Program Manager.
United States Geological Survey work orders are now in place for the
services of two more Cassini Science Team members, bringing the total to 35
of 37 science contracts or work orders now in effect. The remaining two,
also with USGS, are expected to be completed soon.
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Galileo - Countdown To Europa
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GALILEO - COUNTDOWN TO EUROPA
March 25, 1998
It is now 3 days and 19 hours to the Galileo spacecraft's next encounter
with Europa.
A special Countdown to Europa home page is now available on the Galileo
Home Page:
http://www.jpl.nasa.gov/galileo/countdown/
Launched in October 1989, Galileo entered orbit around Jupiter in December
1995, and completed its primary 2 year orbital tour around the
solar system's largest planet. Galileo has embarked on a two-year extended
mission, called Galileo Europa Mission (GEM). During GEM, Galileo will make
8 close flybys of Europa, four flybys of Callisto, and two close encounters
with Io provided the spacecraft is still alive.
The third encounter for GEM is scheduled for Europa on March 29, 1998 at
13:23 UT. With a diameter of 3,138 km, Europa is slighty
smaller than our own Moon and is the smoothest object in the solar system.
On Galileo's previous encounters with Europa, evidence of a possible ocean
were found, including the discovery of ice vocalnoes (non active),
probable icebergs, and salt deposits on the surface. Galileo will continue
its attempt to find additional evidence of a liquid ocean underneath Europa's
icy crust and look for signs of active volcanism on the moon's young surface.
On the upcoming encounter, the spacecraft will pass by Europa at a distance of
1,649 km, which is 124 times closer than Voyager's closest approach. Galileo
will focus on Mannann'an crater and Tyre macula. Observations of Io, Ganymede
and Callisto will also be taken.
Highlights of the Countdown to Europa home page:
o A virtual flyby of Europa with computer-generated approach images of
Jupiter and Europa displayed at the top of the home page. These images
are all updated every 5 minutes.
o Live Doppler plots of Galileo spacecraft radio signal as it received on
Earth. Watch the gravity of Europa change the frequency of the radio
signal in real-time. The Doppler plots will be updated every
minute on encounter day (March 29).
o Flyby animation of the Europa 14 flyby.
o The latest Galileo status reports reporting on the Europa 14 encounter.
o Fact sheets and Europa, Callisto and Io.
o A detailed timeline of events and sequences that the spacecraft will
perform for the Europa 14 encounter.
o Voyager 1 & 2 images of Callisto, Ganymede, Europa and Io.
o Hubble Space Telescope images of the Galilean satellites.
o Pioneer 10 & 11 images of Callisto, Ganymede, Europa and Io.
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ Pasadena, CA | The truth always turns out
/___| | | | ___/ | |/__ /| | to be simpler than you
|_____|/ |_|/ |_____|/ | thought. Richard Feynman
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=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: WDC-A R&S Launch Announcement 12926: Iridium 51
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COSPAR/ISES
WORLD WARNING AGENCY FOR SATELLITES
WORLD DATA CENTER-A FOR R & S, NASA/GSFC
CODE 633, GREENBELT, MARYLAND, 20771. USA
SPACEWARN 12926
COSPAR/WWAS USSPACECOM NUMBER
SPACECRAFT INTERNATIONAL ID (CATALOG NUMBER) LAUNCH DATE,UT
IRIDIUM 51 1998-018A 25262 25 MARCH 1998
..JOSEPH H. KING, DIRECTOR, WDC-A-R&S.
[PH: (301) 286 7355.
E-MAIL: KING@NSSDCA.GSFC.NASA.GOV
25 MARCH 1998, 22:40 UT]
Dr. Edwin V. Bell, II
_/ _/ _/_/_/ _/_/_/ _/_/_/ _/_/ Mail Code 633
_/_/ _/ _/ _/ _/ _/ _/ _/ NASA Goddard Space
_/ _/ _/ _/_/ _/_/ _/ _/ _/ Flight Center
_/ _/_/ _/ _/ _/ _/ _/ _/ Greenbelt, MD 20771
_/ _/ _/_/_/ _/_/_/ _/_/_/ _/_/ +1-301-286-1187
ed.bell@gsfc.nasa.gov
NSSDC home page: http://nssdc.gsfc.nasa.gov/
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=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: WDC-A R&S Launch Announcement 12927: Iridium 61
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COSPAR/ISES
WORLD WARNING AGENCY FOR SATELLITES
WORLD DATA CENTER-A FOR R & S, NASA/GSFC
CODE 633, GREENBELT, MARYLAND, 20771. USA
SPACEWARN 12927
COSPAR/WWAS USSPACECOM NUMBER
SPACECRAFT INTERNATIONAL ID (CATALOG NUMBER) LAUNCH DATE,UT
IRIDIUM 61 1998-018B 25263 25 MARCH 1998
..JOSEPH H. KING, DIRECTOR, WDC-A-R&S.
[PH: (301) 286 7355.
E-MAIL: KING@NSSDCA.GSFC.NASA.GOV
26 MARCH 1998, 13:50 UT]
Dr. Edwin V. Bell, II
_/ _/ _/_/_/ _/_/_/ _/_/_/ _/_/ Mail Code 633
_/_/ _/ _/ _/ _/ _/ _/ _/ NASA Goddard Space
_/ _/ _/ _/_/ _/_/ _/ _/ _/ Flight Center
_/ _/_/ _/ _/ _/ _/ _/ _/ Greenbelt, MD 20771
_/ _/ _/_/_/ _/_/_/ _/_/_/ _/_/ +1-301-286-1187
ed.bell@gsfc.nasa.gov
NSSDC home page: http://nssdc.gsfc.nasa.gov/
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=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: JPL Recruits Two Experts To Help Hunt For New Planets and Life
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: Jane Platt
FOR IMMEDIATE RELEASE March 5, 1998
JPL RECRUITS TWO EXPERTS TO HELP HUNT FOR NEW PLANETS AND LIFE
Two newly-arrived scientists at NASA's Jet Propulsion
Laboratory will play a key role in the search for planets around
other stars and the hunt for life beyond Earth. The appointments
highlight a new JPL initiative to unite scientists from various
disciplines, such as biology and astronomy, to study the
evolution of planets and life in the universe.
Dr. Didier Queloz, a Swiss astronomer who co-discovered the
first known planet around a star similar to our Sun, is a
distinguished visiting scientist at JPL for the next year and a
half. Dr. Kenneth Nealson has joined JPL as a senior researcher
in astrobiology, a new field whose goal is to understand how
planets and life co-evolve.
While at JPL, Queloz will continue his search for planets
and help the Lab develop sophisticated search technologies. His
work will benefit NASA's Origins Program, a series of planned
missions to study the formation of galaxies, stars, planets and
life. The program has gained momentum from discoveries by Queloz
and, subsequently, other astronomers, of several planets orbiting
stars beyond our Sun. Many scientists believe this raises the
odds that an Earth-like planet exists with suitable conditions
for life.
Queloz, a Swiss citizen, received his degree in physics in
1990 from the University of Geneva and worked on his doctoral
thesis at Geneva Observatory with Professor Michel Mayor from
1991 to 1995. Using the French Elodie telescope in Haute
Provence, France, they looked for signs of a Doppler shift in
nearby stars. As a star moves closer and then farther away from
Earth, the star's color shifts from red to blue. By detecting
this motion, astronomers can infer that the star is being tugged
by gravity from an orbiting planet.
"Back then, these experiments were considered a bit nutty,"
recalled Queloz. When Queloz and Mayor first detected a Doppler
shift from the star 51 Pegasus, Queloz said their first reaction
was, "We'd better check our instruments."
Even after they verified the instruments' accuracy, Queloz
and Mayor spent several weeks monitoring 51 Pegasus to confirm
the discovery. In July of 1995, they were confident enough to
buy a large cake and hold a celebration party in the south of
France for family and friends. Queloz and Mayor formally
announced their discovery, a Jupiter-sized planet orbiting 51
Pegasus, at an October 1995 scientific meeting in Florence,
Italy.
Queloz has received several honors, including the Swiss
Society for Physics' Balzers Award, the Bioastronomy Medal from
the International Astronomical Union, Commission 51, and a Best
Thesis in Science honor from a Swiss corporation, Vacheron
Constantin.
Queloz is continuing his hunt for new planets with the
Elodie telescope and its twin, Coralie, a Swiss telescope in La
Silla, Chile. But he and other astronomers face great challenges
in finding new and better ways to detect planets more like Earth.
Current techniques allow only for the detection of giant,
Jupiter-sized planets, which are considered unlikely candidates
for life.
While at JPL, Queloz will share his planet-finding
experience with engineers who are designing more advanced
technologies. Queloz is using a testbed interferometer at
Caltech's Palomar Observatory to run tests on stars and prepare
for an observing program. This work will help pave the way for
other Origins projects, including the W.M. Keck Observatory
interferometer in Hawaii, the Space Interferometry Mission, and
the Terrestrial Planet Finder, all being planned by NASA.
Interferometry combines and processes light from several
telescopes to simulate a much larger telescope, and holds great
promise as a tool in the search for Earth-sized planets. "I'd
like to play a role in future exploration by helping to define
interferometry techniques," Queloz said.
During his stay at JPL, Queloz is living in Pasadena with
his wife and their two children.
Until very recently, an astronomer like Queloz would have
had little if any interaction with a biological scientist like
Dr. Kenneth Nealson. But various disciplines, such as astronomy,
geology, biology and chemistry, are joining forces to study the
development of life on Earth and the prospects of life elsewhere.
Therefore, the work of scientists like Nealson and Queloz is
converging to form a broad, interdisciplinary approach.
"After all," said Nealson, "life is not a simple system and
no science operates in a vacuum. Younger students are studying
several disciplines to gain a more comprehensive view."
Nealson is part of this new wave of scientific training, as
a geobiology teacher and faculty associate in Caltech's geology
and planetary sciences division. At JPL, a division of Caltech,
Nealson has been appointed to head a new astrobiology unit.
Nealson said over the next few years, his astrobiology group will
develop an understanding of the way life and planets have
evolved, and will define the signatures of life.
"Not many foolhardy souls have ventured into this area,"
Nealson said. "After all, how can you find life if you don't
know what you're looking for? This is a very, very important
problem to be solved because right now we're not sure how to
distinguish life from non-life. Our goal is to develop tools to
make that distinction clearly."
In recent years, microbiologists have made startling
discoveries about the hardiness of life on Earth, studying living
organisms in thermal vents, acid lakes and other unlikely
environments. Nealson pointed out, "This has opened the eyes of
scientists to the notion that life could exist under seemingly
inhospitable conditions on other planets."
Astrobiologists will also study changes in Earth's chemical
composition over billions of years. They will then apply this
knowledge to other planets to look for "chemical signatures" that
might indicate that life has existed or could exist there.
Nealson said astrobiology will be useful for numerous space
missions, including the Mars sample return mission, scheduled to
bring back Martian rocks in the middle of the next decade.
Astrobiology will also benefit the Origins Program's Terrestrial
Planet Finder, which will look for Earth-like planets around
other stars and hunt for signs of life-sustaining chemicals.
Nealson said astrobiological studies may prove valuable in the
study of Jupiter's moon, Europa, which may have liquid oceans
under its frozen surface. This icy moon is currently being
studied by NASA's Galileo Europa Mission, and a new Europa
Orbiter has a planned launch in 2003.
Originally from West Liberty, Iowa, Nealson got his bachelor
of science degree in biochemistry in 1965 from the University of
Chicago. He earned his Ph.D. in microbiology from the University
of Chicago and did postdoctoral studies at Harvard University.
Nealson taught at Scripps Institution of Oceanography, San Diego,
CA, and at the Center for Great Lakes Studies, University of
Wisconsin, Milwaukee, WI. His honors include the Guggenheim
Fellowship for Sabbatical Leave in 1981, and an appointment as an
elected fellow in the American Academy of Microbiology, which he
received in November 1993.
Nealson and his wife live in South Pasadena, CA.
#####
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=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Don Yeomans To Lead US Science Team On Asteroid Lander Mission
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: Mary Beth Murrill
FOR IMMEDIATE RELEASE March 5, 1998
YEOMANS TO LEAD U.S. SCIENCE TEAM ON ASTEROID LANDER MISSION
Astronomer Dr. Donald K. Yeomans has been named project scientist for
the NASA portion of a joint U.S.-Japanese mission that will be the first
ever to send a lander and robotic rover to an asteroid, and return an
asteroid sample back to Earth.
Yeomans is a senior research scientist at JPL and supervisor of the
Laboratory's Solar System Dynamics Group, which is responsible for tracking
all the planets, natural satellites, comets and asteroids in the solar
system. He specializes in identifying the orbital paths of comets, asteroids
and other bodies. Yeomans will lead the work of the U.S. science team in
utilizing the scientific instruments on the tiny book-size rover being built
at JPL for the asteroid lander mission, which is called MUSES-C. The U.S.
and Japanese science teams will collaborate on the analysis of scientific
data returned by the spacecraft, including work on the asteroid sample that
will be brought back to Earth.
Scheduled for launch from Kagoshima, Japan on a Japanese M5 rocket in
January 2002, MUSES-C will be the world's first asteroid sample return
mission and will be the first space flight demonstration of several new
technologies. "MUSES-C" stands for Mu Space Engineering Spacecraft (the "C"
signifies that it is the third in a series). It is part of a series of
flight technology and science missions managed by the Institute of Space and
Astronautical Science of Japan (ISAS). NASA's Jet Propulsion Laboratory
(JPL) in Pasadena, CA, is managing the U.S. portion of the mission. Ross M.
Jones is the project manager at JPL.
Asteroid 4660 Nereus, a small, near-Earth asteroid nearly one mile in
diameter, is the target of the MUSES-C mission that will set a lander down
on the asteroid's surface, let loose a miniature rover to gather photos of
the terrain, and collect and return to Earth three samples from the
asteroid's surface. The lander and sample return vehicles are provided by
Japan and the rover is being provided by JPL. All three vehicles will be
combined as one package for flight to the asteroid.
Asteroids are thought to be remnants of the material from which the
inner solar system was formed 4.6 billion years ago. They are representative
of the fundamental building blocks that coalesced into the terrestrial
planets -- Mercury, Venus, Earth and Mars. Scientists want to study
asteroids because of the clues these small bodies may hold to the origin and
evolution of the solar system. Eventually, metal-rich asteroids could also
serve as resources for space mining and human exploration.
Yeomans is well-known for his precise orbit determinations of solar
system objects. He provided the accurate position predictions that led to
the first telescope sighting of comet Halley on its return visit to the
inner solar system in 1982. He provided the predictions that led to the
successful flybys of five international spacecraft past comet Halley in
March 1986. Yeomans also provided the position predictions for asteroids 951
Gaspra and 243 Ida that helped the Galileo spacecraft to make the first
close-up images of an asteroid. More recently, he worked with Dr. Paul
Chodas, also of JPL, to provide the accurate predictions for the impacts of
comet Shoemaker-Levy 9 with Jupiter in July 1994. Yeomans is currently a
science investigator on a NASA mission to fly past three different comets.
He is also the radio science team chief for NASA's Near-Earth Asteroid
Rendezvous (NEAR) mission, a spacecraft headed for an encounter with the
asteroid Eros.
Yeomans has been given seven NASA awards including an Exceptional
Service Medal in 1986. In addition, he was presented with a Space
Achievement Award by the American Institute of Aeronautics and Astronautics,
an award of appreciation by the Goddard Space Flight Center, Greenbelt, MD.
Asteroid 2956 was re-named 2956 in Yeomans' honor. He has authored four
books and more than 80 technical papers on comets and asteroids.
A native of Rochester, NY, Yeomans received his bachelor's degree in
mathematics in 1964 from Middlebury College in Middlebury, VT, and a
master's degree in 1967 and doctorate in astronomy in 1970 from the
University of Maryland. Yeomans and his wife, Laurie, have two adult
children and reside in La Canada-Flintridge, CA
JPL is a division of the California Institute of Technology.
#####
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=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: This Week on Galileo - March 9-15, 1998
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THIS WEEK ON GALILEO
March 9-15, 1998
After ending an uneventful period of limited communications, Galileo resumes
the processing and transmission of pictures and science information stored
on the spacecraft's onboard tape recorder. The data was acquired and stored
on the tape recorder during the spacecraft's close flyby of Jupiter's moon
Europa in Dec. 1997. The 2-1/2 week period of limited communications was
caused by solar conjunction, a period of time during which the sun passes
between the Earth and the spacecraft and solar activity causes radio signals
to and from the spacecraft to become noisy or garbled.
The data scheduled for processing and transmission to Earth this week
includes primarily information from the spacecraft's Near Infrared Mapping
Spectrometer's (NIMS) observation of the Pwyll impact crater region on
Europa. The NIMS information will allow scientists to learn more about the
different types of materials found in this region. To see what this region
looks like you can look for images taken by the spacecraft's camera that
were recently released on our home page. Other information scheduled for
transmission toward the end of this week includes data from the spacecraft's
suite of fields and particles instruments that will add to the repository of
information characterizing the interaction of Europa with the magnetic and
electric fields surrounding Jupiter. Finally, the camera team has scheduled
the processing and transmission of a picture of the Conamara Chaos region
and another picture of a region of mottled terrain.
If some of these information sets sound familiar, it is because they are
part of Galileo's normal period of re-processing and re-transmission of
observations that have previously been transmitted to Earth. This second
"pass" through the recorded data allows the science teams to fill up gaps in
information caused by transmission problems the first time around. The
second pass also provides the opportunity to replay portions of observations
that have been identified as particularly interesting or to simply add
additional data from a particular observation.
Also scheduled this week is a test of the spacecraft's attitude control
system. This test will provide engineers with information to help them
determine whether the attitude control system's anomalous behavior has
stabilized or is getting worse. Remember that the spacecraft performed a
close flyby of Europa just prior to the start of our period of limited
communications. During this flyby, the spacecraft was once again exposed to
Jupiter's intense radiation environment. Radiation is considered a leading
candidate as a cause of the hardware fault in one of the attitude control
system's gyroscopes, and which has led to the anomalous behavior. Limited
information contained in the spacecraft's normal engineering data set
suggests that the anomalous gyroscope behavior has not deteriorated.
At the end of this week, the spacecraft is scheduled to perform the next
flight path correction. This correction will fine tune the spacecraft's
orbit as it heads back toward the Jupiter system and another close encounter
with Europa.
For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:
http://www.jpl.nasa.gov/galileo/
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Galileo Update - March 25, 1998
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Galileo Europa Mission Status
March 25, 1998
NASA's Galileo spacecraft is sending to Earth the final
pictures and science information stored on its onboard tape
recorder during the December 1997 flyby of Jupiter's moon Europa.
These data include an observation of a region on Europa with
wedge-like features, which may indicate that a liquid ocean lies
under the surface, and another observation of volcanic activity
on Jupiter's moon Io. An observation by the photopolarimeter
radiometer is part of a series designed to look for hot spots
which might offer evidence that a heat source on Europa led to
the creation of a liquid ocean or slush.
The flight team is preparing for Galileo's next Europa
flyby, scheduled for Sunday, March 29, at an altitude of about
1,645 kilometers (1,022 miles). A flight path correction was
performed on Friday, March 13, and an attitude update was
performed Thursday, March 19. Both events went well, even though
they used the gyroscopes, the known cause of recent anomalous
behavior of the attitude control system. Precautions were taken
to prevent the gyroscope anomaly from affecting activities. The
flight team has decided the upcoming Europa flyby will be
performed without the gyros. This means there will be no way to
compensate for any wobble that may be present in the spacecraft's
spin axis, and instrument pointing and stability are likely to be
degraded somewhat. Only very minimal effects on images taken by
the spacecraft's camera are expected, with a somewhat greater
impact anticipated for another instrument, the near infrared
mapping spectrometer.
On Thursday, March 26, Galileo will perform its final flight
path correction before Sunday's Europa flyby, and the flight team
will send computer commands to control all spacecraft activity
during the encounter period. Regular maintenance of Galileo's
onboard tape recorder will be performed Friday.
Galileo's flight team is nearing completion of modifications
to the attitude control system flight software that would allow
the spacecraft to operate with only one gyro. Although this
won't be a complete "fix," it will eliminate the need for
workarounds currently being used for maneuvers and attitude
updates.
The recent anomalies may be caused by Galileo's long-term
exposure to Jupiter's intense radiation. The spacecraft
successfully completed its primary mission in December 1997 and
is now in its two-year extension, the Galileo Europa Mission.
The flight team will continue to monitor the radiation's impact,
but current plans include five more Europa flybys, four Callisto
encounters, and one or two of Io, depending on spacecraft health.
#####
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Planetary Society Honors Eugene Shoemaker
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Planetary Society Honors Eugene Shoemaker with
Comet and Asteroid Discovery
Grant Program Named for Astronomer Shoemaker
Supports Searches for Potentially Dangerous
Near-Earth Objects
One year ago today, this web site announced that
the Planetary Society had launched its Near-Earth
Object (NEO) Grant Program to help discover the
comets and asteroids known to be in our planet's
celestial vicinity. Since then, this ongoing
program has been dubbed the Gene Shoemaker
Near-Earth Object Grants -- to honor the late
comet and asteroid discoverer -- and the program
has given $35,000 to researchers from around the
world who search for asteroids and comets with
orbits close enough to Earth to pose a potential
hazard to our planet.
The first four recipients of the grants are now
putting their grants to work in NEO detection
efforts in the United States, Russia, and
Australia.
In the US, Walter Wild in Chicago, Illinois, and
Bill Holiday in Corpus Christi, Texas lead
searches that involve amateur astronomers. Wild,
an astronomer at the University of Chicago, leads
a group of amateur astronomers who are conducting
a NEO search from Yerkes Observatory in Wisconsin.
Amateur astronomer Holiday is using his grant to
upgrade his home-built rotating roof observatory.
Kirill Zamarashkin is the project coordinator for
a joint Russian-Ukrainian search program at the
Crimean Astrophysical Observatory. This research
team has used its Gene Shoemaker grant money to
help construct the first element of an automatic
complex to search for NEOs.
Based in Loomberah, New South Wales in Australia,
Gordon Garradd is using his Gene Shoemaker NEO
Grant to complete a 45-centimeter (18-inch)
Newtonian telescope and to acquire a larger,
higher-grade imaging sensor (a CCD, or charge
coupled device).
A recent report of Earth's impending close
encounter with an asteroid (featured in an earlier
headline article on this web site) emphasized the
importance of detecting the comets and asteroids
whose orbits might intersect Earth's. Astronomers
estimate that there are several thousand NEOs
larger than one kilometer and 150,000 to perhaps
100 million larger than 100 meters in size.
While various astronomical groups and NASA
advisory committees have made strong
recommendations to accelerate discovery of these
asteroids, government support for NEO search
programs remains very modest. Thus, the Planetary
Society's Gene Shoemaker Near-Earth Object Grants
help fill this funding gap.
The Planetary Society launched its Near-Earth
Object Grant Program to increase the rate of
discovery and to permit wider participation by
amateur observers; observers in developing
countries; and professional astronomers who, with
seed funding, could greatly increase the potential
of their programs to contribute significantly to
the search. The Society accepts applications for
these grants continuously.
To apply for a Gene Shoemaker Near-Earth Object
Grant, read the guidelines and fill out the
application form, which are provided on this web
site:
http://planetary.org/NEO/neo-guidelines.html
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Cassini Update - March 26, 1998
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Cassini Mission Status
March 26, 1998
Cassini's fault protection system worked as planned Tuesday after the
spacecraft detected a very small orientation difference between its two
stellar reference units, according to preliminary data received from the
spacecraft yesterday. The event has had no impact on the mission and all
planned activity for Cassini's Venus flyby next month remains on schedule.
The second stellar reference unit, part of Cassini's attitude and
articulation control subsystem, was in the process of taking over while the
first stellar reference unit was to undergo a routine maintenance "bake-out"
heating to remove normal post-launch contaminants from its aperture. This
was the first use of the second stellar reference unit, and as it began
operating, Cassini's attitude control software found a very small difference
in the orientation of the units. Sensing this difference, the computer that
controls the attitude control subsystem executed pre-programmed commands
that brought the spacecraft into a low-activity state to await instruction
from ground controllers. The spacecraft executed this response exactly as
designed and the spacecraft remains healthy, project officials said. Cassini
has remained in contact with ground controllers throughout, and engineering
data on the event and the spacecraft's overall operations were received
yesterday. Preliminary analysis indicates that the discrepancy was within
specifications, but that control limits were set too tightly, triggering the
preprogrammed commands that set the spacecraft in its low-activity state.
This problem is expected to be solved easily with an adaptation made to the
spacecraft's attitude and articulation control software.
By early this afternoon, ground controllers will have sent commands
to return the spacecraft to normal operations. Cassini remains on course for
its April 26 flyby of Venus, with the last fine-tuning of the flight path,
if it is needed, scheduled for early April. During its Venus flyby,
Cassini's radio and plasma wave science instrument will take advantage of
the opportunity to search for lightning in Venus's atmosphere.
Today, the spacecraft is approximately 17 million kilometers (about
10.5 million miles) from Venus and is traveling at a speed of about 143,000
kilometers (about 88,800 miles per hour). It has traveled about 440 million
kilometers (about 273 million miles) on its Saturn-bound trajectory since
launch on October 15, 1997.
#####
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Mars Global Surveyor To Attempt Imaging of 'Face' On Mars, Viking & Pa
Subject: Mars Global Surveyor To Attempt Imaging of 'Face' On Mars, Viking & Pa
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: Diane Ainsworth
FOR IMMEDIATE RELEASE March 26, 1998
MARS GLOBAL SURVEYOR TO ATTEMPT IMAGING OF FEATURES OF PUBLIC INTEREST
NASA's Mars Global Surveyor spacecraft is about to begin a summer-long set
of scientific observations of the red planet from an interim elliptical
orbit, including several attempts to take images of features of public
interest ranging from the Mars Pathfinder and Viking mission landing sites
to the Cydonia region.
The spacecraft will turn on its payload of science instruments on March 27,
about 12 hours after it suspends "aerobraking," a technique that lowers the
spacecraft's orbit by using atmospheric drag each time it passes close to
the planet on each looping orbit. Aerobraking will resume in September and
continue until March 1999, when the spacecraft will be in a final, circular
orbit for its prime mapping mission.
It will not be possible to predict on which orbit the spacecraft will pass
closest to specific features on Mars until Global Surveyor has established a
stable orbit and flight controllers are able to project its ground track.
This process should be completed in the next few days. The exact time of
observations and the schedule for the subsequent availability of photographs
on the World Wide Web are expected to be announced early next week.
"Global Surveyor will have three opportunities in the next month to see each
of the sites, including the Cydonia region, location of the so-called 'Face
on Mars,' " said Glenn E. Cunningham, Mars Global Surveyor project manager
at NASA's Jet Propulsion Laboratory, Pasadena, CA. "The sites will be
visible about once every eight days, and we'll have a 30- to- 50-percent
chance of capturing images of the sites each time."
Several factors limit the chances of obtaining images of specific features
with the high-resolution mode of the camera on any one pass. These factors
are related primarily to uncertainties both in the spacecraft's pointing and
the knowledge of the spacecraft's ground track from its navigation data. In
addition, current maps of Mars are derived from Viking data taken more than
20 years ago. Data obtained by Global Surveyor's laser altimeter and camera
during the last few months have indicated that our knowledge of specific
locations on the surface is uncertain by 1 to 2 kilometers (0.6 to 1.2
miles). As a result, the locations of the landing sites and specific
features in the Cydonia region are not precisely known.
In addition, the Mars Pathfinder and Viking landers are very small targets
to image, even at the closest distance possible, because they are the
smallest objects that the camera can see. The Cydonia features, on the other
hand, are hundreds to thousands of times larger and the camera should be
able to capture some of the features in that area.
Global Surveyor's observations of the Viking and Pathfinder landing sites
will provide scientists with important information from which to tie
together surface observations and orbital measurements of the planet. Data
from landing sites provide "ground truth" for observations of the planet
made from space.
As for the "Face on Mars" feature, "Most scientists believe that everything
we've seen on Mars is of natural origin," said Dr. Carl Pilcher, acting
science director for solar system exploration in NASA's Office of Space
Science, Washington, DC. "However, we also believe it is appropriate to seek
to resolve speculation about features in the Cydonia region by obtaining
images when it is possible to do so."
Information about Viking observations of the Cydonia region and a listing of
those images are available on the World Wide Web at
http://www.hq.nasa.gov/office/pao/facts/HTML/FS-016-HQ.html .
New images of the landing sites and Cydonia region taken by Mars Global
Surveyor will be available on JPL's Mars news site at:
http://www.jpl.nasa.gov/marsnews and on the Global Surveyor home page at
http://mars.jpl.nasa.gov . These sites will also carry detailed schedules of
the imaging attempts once they have been determined. Images will also be
available on NASA's Planetary Photojournal web site at
http://photojournal.jpl.nasa.gov .
So far in the aerobraking process, Global Surveyor's orbit has been reduced
from an initial 45-hour duration to less than 12 hours. During the
aerobraking hiatus, the spacecraft will be orbiting Mars about once every
11.6 hours, passing about 106 miles (170 kilometers) above the surface at
closest approach and about 11,100 miles (17,864 kilometers) at its farthest
distance from the planet. The pause in aerobraking allows the spacecraft to
achieve a final orbit with lighting conditions that are optimal for science
observations.
Mars Global Surveyor is part of a sustained program of Mars exploration,
managed by JPL for NASA's Office of Space Science, Washington, DC. Lockheed
Martin Astronautics, Denver, CO, which built and operates the spacecraft, is
JPL's industrial partner in the mission. Malin Space Science Systems, Inc.,
San Diego, CA, built and operates the spacecraft camera. JPL is a division
of the California Institute of Technology, Pasadena, CA.
#####
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: MGS Prepares To Photograph Landing Sites, Cydonia Regio [1/3]
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http://mars.jpl.nasa.gov/mgs/target/pressrel.html
MARS GLOBAL SURVEYOR COMPLETES FIRST AEROBRAKING PERIOD AND PREPARES TO
PHOTOGRAPH THE MARS PATHFINDER LANDING SITE AND FEATURES IN THE CYDONIA
PLAIN
The Mars Global Surveyor spacecraft is about to resume scientific
observations of the surface of Mars with its first objective to attempt to
photograph the Mars Pathfinder landing site, the features in the Cydonia
region, and the Viking lander sites. Surveyor is coming up on a period
beginning near the end of March and continuing for about a month in which
orbital and lighting conditions will be suitable for these observations.
The opportunities to see these targets from the Surveyor spacecraft will
occur in three clusters of two and a half days each during the next month.
Each target will be visible once in each cluster and the clusters will be
separated by eight days. It will not be possible to predict on which orbits,
and thus, on which days, the spacecraft will come closest to the targets
until after aerobraking has been terminated on Friday, March 27th. Then
several orbits of navigation tracking data have been obtained in order to
pin point Surveyor's new orbital characteristics.
The exact time of the observation opportunities and the schedule and process
for the release of the resulting photographs will be announced in a few
days. Within a few days before the actual observations, a detailed sequence
of the spacecraft's activities will be posted on this webpage, and the
project staff will provide a near real time commentary on the events as they
occur.
Surveyor's science instruments will be turned on again on Friday, March
27th, after having been off since February 20th when the orbital period
became too short for both science and aerobraking operations to be conducted
simultaneously. Now that aerobraking will be on hold for five months,
Surveyor can return to acquiring science data.
End of Aerobraking and Science Phasing Orbit
Transition Timeline
( Subject to change, depending on level of drag encountered )
Date Time Orbit Event A = apoapsis P = periapsis
3/23/98 A194 UP ABM to 0.1 N/m2 (0.5 m/s) Took orbit up to an
23:10 UTC aerobraking altitude where the dynamic pressure is 0.1 N/m2
so that aerobraking is slowed to more easily manage the
arrival at the target period of 11.6 hours. THIS EVENT HAS
BEEN COMPLETED IN A SATISFACTORY MANNER!
3/26/98 A201 ABX-1 (Aerobraking Termination Maneuver) (4.43 m/s) A
21:20 UTC bi-propellant main engine burn to terminate aerobraking by
raising the altitude of periapsis to 170 km establishing
the science phasing orbit
3/27/98 A202 Instrument Turn-On command window opens (shortly after A201
08:57 UTC apoapsis which is at 08:52)
3/28/98 P203 P202 First PERISCAN (Periapsis Science Acquisition) Pass.
02:24 UTC This will be the first time in the science phasing orbit
that science data will be acquired, and the start of the
six orbit period where the navigation baseline for targeted
opportunities will be established.
Science acquisition will continue until early September
when aerobraking will be resumed.
PHOTOGRAPHING THE FEATURES IN THE CYDONIA PLAIN
At the launch of the Mars Global Surveyor mission, NASA announced that it
would re-photograph the Cydonia region of Mars -- an area that contains a
number of features including the famous "Face on Mars" -- when Surveyor was
over that region during its mapping mission. In addition, NASA said it would
announce to the public when these opportunities would occur and when the
resulting pictures would be released. The opportunity to accelerate the
schedule of photographing these areas significantly before the mapping
period has been afforded by the recent modification of Surveyor's mission.
This modification was made to extend aerobraking for a year in order to
compensate for a structural weakness discovered in one of Surveyor_s solar
panels.
TARGETS FOR OBSERVATIONS
Mars Pathfinder landed last July 4th, deployed the Sojourner rover and
captivated world interest as it explored a small region in Aris Vallis. The
two Viking landers that NASA placed on the surface of Mars in 1976 conducted
inconclusive experiments to try to discover life in the Martian soil. The
Cydonia region has become notable from the discovery of an object that looks
much like a human face in several pictures taken by the Viking Orbiter
spacecraft over 20 years ago. Some researchers have proposed arguments that
the "Face" and other objects in its vicinity are artifacts of an extinct
civilization and have pressed NASA for further investigations of the region.
Latitude and Longitude of four targets located in East longitude
Target Latitude Longitude
Cydonia Region 41.0 North 350.5 East
Pathfinder 19.01 North 33.52 East
Viking 1 Lander 22.27 North 312.03 East
Viking 2 Lander 47.67 North 134.48 East
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: MGS Prepares To Photograph Landing Sites, Cydonia Regio [2/3]
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HOW THESE OBSERVATIONS WILL BE MADE
It is anticipated that Surveyor's ground track will not pass directly over
any of the targets so it will be necessary to rotate the spacecraft to sweep
the field of view of its cameras across the targets as the spacecraft
travels south from over the Martian north pole as the spacecraft gets closer
and closer to the surface Photographs will be taken as long, narrow strips
as the field of view is sweeping across the targets.
The orbital conditions chosen for the next five month period when Surveyor
will not be aerobraking offer a particularly advantageous pattern of near
overflights of these targets. Because of the position of the targets in
longitude around the planet (Viking 2 is 182 degrees to the east of Viking
1, Mars Pathfinder is 14 degrees to the east of Viking 1, and Cydonia is 24
degrees east of Viking 1) the near overflights will occur in clusters of
five orbits every 17 orbits. Surveyor's orbital period of 11.6 hours, which
is slightly less half a Martian day, causes the spacecraft's ground track to
alternate sides of the planet on consecutive revolutions. At every closest
approach to the planet or periapsis, the spacecraft is about 190 degrees to
the east of where is was one orbit ago and about 20 degrees to the east of
where it was two orbits ago.
These observations are termed "targeted" because mission controllers will
take extraordinary steps to try to assure that the selected targets are
within the high resolution camera's field of view. This is a difference
process than has been used in the past or will be used in the future to
collect images of Mars from Global Surveyor. The normal manner of acquiring
images and other science data is to point the instruments straight down at
the surface or to take science data as the instrument fields of view sweep
across the planet as the spacecraft performs maneuvers to accomplish
aerobraking. During the aerobraking hiatus last Fall, the instruments were
pointed straight down at the surface during the few minutes that the
spacecraft was closest to the planet.
During the two years of mapping that will start in March 1999, the
instruments will always point straight down at the planet's surface.
The photographs that have been acquired during the just concluding
aerobraking phase were acquired on each orbit, a few minutes after the
closet approach to the planet's surface and after aerobraking had completed,
as the spacecraft was being rotated from the aerobraking attitude to the
array normal spin attitude used during the rest of each orbit.
WHY ARE THESE OBSERVATIONS BEING MADE NOW?
Surveyor is just completing its first period of aerobraking -- a portion of
the mission in which the spacecraft skims through the top of the Martian
atmosphere at each closest approach to the planet in order to circularize
its orbit. Currently, Surveyor's orbital period has been reduced from its
initial 45 hour duration to under 12 hours. The orbital period will stay at
11.6 hours until early September when aerobraking will resume again for the
final five months of aerobraking to reach the exact orbital conditions
necessary to begin Surveyor's two year long mapping mission. During the
period without aerobraking, Mars will move around the Sun to a position
where the lighting of the Martian surface under Surveyor's flight path will
be optimum for the mapping observations.
The upcoming opportunities appear to be the best of the period because the
periapsis location will be migrating to higher latitudes and going over the
north pole later in the period, and thus, the distance to the targets will
be increasing. In the next few weeks the elevation of the sun will be
between 15 and 20 degrees at the high latitude targets (Cydonia and Viking
2) which will make for good imaging. The sun elevation will be between 40
and 45 degrees for the low latitude sites (Viking 1 and Mars Pathfinder)
which will make for acceptable imaging.
HOW WELL WILL WE BE ABLE TO SEE THE TARGET IN THE IMAGES?
For Example, the field of view of high resolution camera covers a width of 3
km (1.9 miles) when the camera is 400 km (249 miles) from its target. The
length of the image will be several kilometers (several miles). The
resolution, or smallest feature discernible in the image varies with the
distance to the target, but at this distance will be approximately 1.4
meters (4.6 feet). The Mars Pathfinder and Viking landers are about 2 meters
(6.6 feet) in diameter, or very close to the minimum resolution obtainable.
The features in the Cydonia region are on the scale of 1 to 2 km (0.6 to1.2
miles) and should be readily visible and may nearly fill the width of field
of view of the images. Until the exact orbit characteristics are known, we
will not know the exact distance to the targets. It could be further than
the 400 km quoted in the example above and the resolution would be poorer,
or it could be closer.
The Mars Pathfinder and Viking landers are very small targets, at the limit
of resolution of the camera, even at the closest distance. It will be an
extraordinary event if they are recognized in the images. Features in the
Cydonia region, however, being hundreds to thousands of times larger, will
be very easily seen, even at the more distant ranges, and while all features
in this area may not be within the field of view due the expected targeting
errors, there is a high probability that many will be seen with good
resolution. The best known location of the "Face" will be the target point
in Cydonia.
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: MGS Prepares To Photograph Landing Sites, Cydonia Regio [3/3]
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WHAT IS THE PROBABILITY THAT THIS IMAGING WILL BE SUCCESSFUL? OR ARE WE SURE
WE'LL GET THE PICTURES?
The probability that the targets of interest will be within the camera's
field of view varies between 30 and 50 percent. This is because there are a
number of sources of error or uncertainties associated with the targeting
process.
One such error source relates to how good the current maps of Mars are. As
all early explorers on Earth found, early maps contain many inaccuracies.
The data obtained by Surveyor's laser altimeter and cameras in the last few
months have indicated that locations of observed objects on the surface are
displaced 1 to 2 km (0.6 to 1.2 miles) from where the Viking era maps locate
them.
Another source of error is the accuracy with which the spacecraft's
trajectory is predictable. This involves where the ground track of the
flight path lies or will lie on the surface, and the time the spacecraft
will fly over or near the desired targets. The accurate prediction of the
ground track allows the mission controllers to decide how much to rotate the
spacecraft to point the camera, and the timing prediction will be used by
the camera operators to control when to record the image. In preparing the
Surveyor's sequences for these observations, mission controllers will use
the results of orbit computations made as near to the planned observation
time as possible in order to minimize this uncertainty.
In addition, some error is introduced by the planet's rotation translating
downtrack error into crosstrack error.
The last source of error is how accurately the spacecraft can be rotated and
pointed. The design specifications for Global Surveyor call for it to be
pointable with an accuracy of 10 milliradians ( 0.057 degrees), that is,
mission controllers should be able to point the instruments to within 10
milliradians (0.057 degrees) of a target. Experience with the spacecraft
indicates that it actually performs much better, and that a pointing
accuracy of 3 milliradians (0.017 degrees) is possible.
Combining these error sources together in the proper statistical manner with
the distance from the spacecraft to the targets tells us the probability
that the targets will be within the camera's field of view. This probability
varies from about 70% when the targets are 1000 km (621 miles) from the
spacecraft, to about 25% when the targets are 400 km (249 miles) from the
spacecraft.
WHY ARE THESE IMAGES IMPORTANT?
A great deal of scientific controversy rages over the interpretation of the
features seen in the Viking images of the Cydonia Plain. Additional
photographs with the much better resolution that Surveyor's camera will
provide and perhaps different lighting conditions can provide new
information to aid in the understanding of what is seen there.
In addition, the observations of the previous landing sites provide
scientists with important knowledge to tie together the observations made on
the surface from the landers with those made from orbit above the planet.
The Viking 1 Lander site is the first location on Mars where humans were
able to see and touch the Martian surface at a familiar scale. This site,
the following higher latitude Viking 2 Lander site and the Pathfinder site
play a large role in understanding the processes which have operated on the
Martian surface over time and the state of the surface and atmosphere at
present. These sites serve as "ground truth" locations where ideas developed
from orbital observations can be tested, verified and then extended to other
regions of Mars such as those we may wish to visit in the future.
Several examples of this use of the sites for ground truth illustrates their
significance. One of the results of the Viking Orbiter Infrared Thermal
Mapper experiment was a rock abundance map based on the observed change in
surface temperature over time (large rocks cool more slowly than sand or
dust). The only way to verify the results of this rock abundance map was
with the two Viking landing sites where, fortunately, numerous rocks were
present. Rock abundance knowledge helps in understanding the depositional
history of the surface and large rocks represent a landing hazard. Mars
Global Surveyor carries an advanced version of the Viking instrument called
the Thermal Emission Spectrometer (TES) which will be able to map rock
abundance at more than one hundred times higher spatial resolution than
Viking and the TES experimenters will have another site (Pathfinder) to use
to verify their deductions.
The high resolution mode of the Mars Orbiter Camera (MOC) carried by the
Mars Global Surveyor spacecraft is capable of returning images of objects as
small as 1.4 meters across. Some of the largest rocks in the area of the
landing sites may be visible and such rock or boulder fields have been seen
in MOC images at other locations on Mars. The careful surveys which have
been done of the distribution of rocks as a functions of rock size can now
be used with MOC images to estimate rock populations at other locations on
Mars.
THE CURRENT STATUS OF MARS GLOBAL SURVEYOR
The Global Surveyor spacecraft is in excellent health. For the next five
months, Surveyor will be maintained in an 11.6 hour period elliptical orbit
around Mars. Its closest point to the planet's surface will be 170 km (106
miles) and its furthest distance will be 17,864 km (11,100 miles).
WHAT'S NEXT AFTER THESE SPECIAL OBSERVATONS?
The observations described above will occur three times during the month of
April. Surveyor will continue to acquire science data from its other
instruments during the month. Then, during May, Mars, and hence Global
Surveyor will move behind the Sun as seen from Earth. During this period of
solar conjunction, communications with Surveyor will be greatly degraded.
Surveyor will cease science observations and will be put into a special
attitude to assure proper temperatures of the science instruments. For two
out of every eight hours it will point its high gain antenna to Earth to
conduct radio communications propagation experiments, and, for part of the
time, to allow mission controllers to monitor the spacecraft's health. At
the end of May, Surveyor will return to acquiring science data from all its
instruments.
Hа сегодня все, пока!
=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: Dust Devils Discovered In Mars Pathfinder Images
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Univerity of Nevada, Reno
Contact: Greg Bortolin (bortolin@scs.unr.edu)
702-784-6216
March 26, 1998
University of Nevada, Reno researchers make major discovery
in Mars images
Dust devils on the surface of Mars have been discovered in
images being examined by researchers at the University of
Nevada, Reno.
Mars' famous dust storms - which can be seen from backyard
telescopes and sensationally cover the red planet's surface
every several years - may be triggered by dust devils.
"Mars' atmosphere is extremely thin and very high wind
velocities are needed to pick up dust. These dust devils, or
mini-twisters, cause these high winds," said professor James
R. Carr of the Department of Geological Sciences at the
university's Mackay School of Mines.
Stephen Metzger, a doctoral student at Nevada, made the
discovery from Mars Pathfinder imagery, using methods
suggested by Carr. Metzger made the discovery in images
downloaded from the NASA Jet Propulsion laboratory in
Pasadena, Calif., using color filters.
By comparing and contrasting the Mars data with that from
arid regions on Earth, such as Nevada, Metzger said much can
be learned about local air pollution, acid rain and global
climate change.
"Dust devils were thought to have been discovered by the
Viking orbiter in 1976, but that was difficult to confirm,"
Carr said. "The significance of this discovery is that it
confirms the Viking discovery and shows that dust devils are
an important geological process on Mars. In fact, dust
devils may be the primary soil erosion process on Mars."
Upon making the initial discovery, Metzger contacted Timothy
Parker, a NASA scientist in Pasadena, and Jeff Johnson, U.S.
Geological Survey scientist, in Flagstaff, Ariz., for
verification and further image processing. Results of this
image processing were presented Tuesday, March 17, in
Houston at the Lunar and Planetary Science Conference.
After seeing these results at last week's international
gathering of planetary scientists in Houston, several NASA
science teams are eager to use the dust devil images in
their atmospheric science and geology research, Metzger
said.
NASA officials have credited Metzger and Carr as the first
researchers to discover the dust devils in Pathfinder
imagery. Metzger is a NASA Fellow, funded by the University
of Nevada System Space Grant Consortium. He also is involved
with the Desert Research Institute, a sister institution of
the University of Nevada, Reno.
An image showing the dust devils is available at this website:
http://www.unr.edu/nevadanews/vol2no118.htm
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=SANA=
Дата: 27 марта 1998 (1998-03-27)
От: Alexander Bondugin
Тема: The "Face On Mars"
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http://www.hq.nasa.gov/office/pao/facts/HTML/FS-016-HQ.html
The "Face On Mars"
Background: The Viking Images
The Viking missions to Mars in the late 1970s produced more information
about the Red Planet than had been gathered in all the previous centuries of
study by Earth-bound astronomers and observers. The primary mission of the
Viking program was to search for signs of life on the surface of Mars. Two
landers containing sophisticated biological laboratories studied soil
samples in a variety of tests which, it was hoped, would prove or disprove
the existence of life.
The results of these tests indicated that Mars contained no life, at least
at these landing sites. However, Viking gathered volumes of data on the
weather, soil chemistry and other surface properties and mapped the surface
using low-to-moderate resolution cameras on the two orbiters.
Shortly after mapping began in 1976 an interesting image taken by the Viking
1 Orbiter was received at the Jet Propulsion Laboratory, Pasadena, Calif.,
which contained a surface feature resembling a human or ape-like face. The
photo was immediately released to the public as an interesting geological
feature and dubbed the "Face on Mars." Shortly afterwards other photos of
the same area were taken, and some scientists believed that the formation
appeared to be a face due to the lighting angles as seen from the Orbiter.
Origin Of Features Examined
Over the years, some people began to raise questions about the origins of
the features. A few ideas and theories arose speculating that the features
may have been built by aliens in the distant past. These theories are based
largely on the results of computer photo enhancements and other analytical
techniques performed on the Viking images beginning in the early 1980s.
Most planetary geologists familiar with the set of photos, however,
concluded that the natural processes known to occur on Mars -- such as wind
erosion, Mars quakes, and erosion from running water in the distant past --
could account for the formation of the complicated fretted terrain of the
Cydonia region, including the face.
Because the entire data set includes only nine low-to-moderate resolution
photos, scientists say that there just is not enough data available to
justify what would be an extraordinary conclusion that the features are not
natural in origin (many scientists question whether images alone would be
enough to settle the matter). Such a proven discovery of extraterrestrial
life or artifacts would be one of the greatest discoveries in human history,
and, as such, demand the most rigorous scientific investigation.
However, despite the phenomenal nature of such a potential discovery, no one
in the scientific community -- either in the U.S. or worldwide -- has ever
proposed an investigation for a mission to study these features. Until more
data is gathered, many scientists consider the probability that the features
are anything other than natural in origin are just too low to justify the
major expenditure of public funds which such an investigation would entail
(more on this below).
What is agreed on is that a greater number of high resolution images of this
area should be gathered. Following the failure of the Mars Observer mission
in August, 1993, NASA proposed a decade-long program of Mars exploration,
including orbiters and landers. The program, called Mars Surveyor, would
take advantage of launch opportunities about every 2 years to launch an
orbiter and a lander to the Red Planet. The first mission, consisting of an
orbiter to be launched in 1996, will map the surface and take high- and
medium-resolution images of particular features on the Martian surface that
are of high interest. NASA intends to make observations of the Cydonia
region making the best effort feasible, either with the first orbiter or on
follow-on missions, to obtain images of the "face" and nearby landforms.
Quite aside from the interest generated by these curious features, Cydonia
has long been regarded as an area of high scientific importance, ever since
the first detailed images were returned by NASA's Viking spacecraft in the
late 1970s. The Cydonia region of Mars is part of the so-called fretted
terrain, a belt of landforms that circles Mars at about 30-40 degrees North
Latitude. In this region, the ancient crust of Mars has been intensely
eroded by weathering processes, leaving high remnants of older crust
surrounded by lower plains of eroded debris.
The landforms of Cydonia resemble in some respects those of terrestrial
deserts, but they probably have been shaped by a unique range of peculiarly
martian agencies: wind, frost and possibly running water in ancient times.
Deciphering the geological age and origin of this terrain will yield
important insights into the evolution of the martian surface, into the role
of ice and water in its development and into the nature of the martian
climate in times past.
Proposing Investigations
The selection of goals and scientific priorities for NASA to undertake on
future space science missions starts in the scientific and academic
communities, as well as within NASA. Scientific associations, such as the
National Academy of Science, determine the research priorities in any given
field of science. For instance, the most important questions remaining about
Mars include gaining an understanding of the amount of water on the planet;
mapping the surface in detail to gain a complete understanding of the
geological processes, history and composition; and gaining a global
understanding of the atmosphere, including climate and weather.
When NASA receives permission to proceed with a science mission, the Agency
publishes an Announcement of Opportunity (AO). The AO solicits interest in
providing high priority scientific investigations and instruments that will
be part of the new mission. The AO receives the widest possible circulation
throughout the university and research communities and industry.
Proposals are submitted and reviewed through a competitive peer review
process. In this process, scientists from various institutions and
organizations evaluate each proposal's scientific and technical merit, and
then rank the relative merit of each. NASA receives the reports of the
review panels and makes a final selection as to which instruments will be
built and actually flown. This rational selection process ensures that only
the most useful research, with a high probability of returning good science,
is done at taxpayer expense.
After selection, each Mars Surveyor Principle Investigator (PI) team will
develop its instrument, build it, test it and prepare it for launch and the
10-month journey to Mars. They are also charged with developing, testing,
and using the software required to properly calibrate their instrument's
data. Most of the scientists working on the various Mars Surveyor missions
will have several years invested in their instrument before the spacecraft
arrives at Mars and they can actually receive the bulk of the data they have
been waiting for.
Obtaining Images of the "Face" and Other Planetary Data
Since the release and subsequent widespread circulation of the 'face'
images, scientists and individual members of the public have freely drawn
their own conclusions about the nature and origin of this feature. NASA
encourages anyone seriously interested in this topic to obtain the photo(s)
and decide for themselves, just as every day many hundreds of independent
researchers and scientists make use of NASA-provided data on a variety of
subjects.
The most noteworthy image of the 'face' feature is available to the public,
for a nominal fee, through Headquarters and JPL. A photo catalogue can be
provided to select images.
The phone numbers for ordering photos are:
HQ: 202/358-1900
JPL: 818/354-5011
All imaging data obtained by the Mars Surveyor program, as well as other
types of data, will be deposited in open data archives. Two such archives
widely used are the Planetary Data System (PDS), an open archive accessible
to thousands of scientists and other individuals, and the National Space
Science Data Center (NSSDC) where images and other data will be readily
available to the general public (generally on CD-ROMs or as hard copy, as
appropriate), for a nominal charge that covers the materials and time needed
to produce the copies. For information about ordering copies of NASA science
mission images, including on CD-ROM format, contact the NSSDC at:
National Space Science Data Center
Request Coordination Center
Goddard Space Flight Center
Greenbelt, MD 20771
Telephone: 301/286-6695
Listed below are the photo numbers of every image taken by Viking of the
'face' feature and the surrounding Cydonia terrain. When ordering from the
data archive centers, refer to the Viking picno (photo number).
Sun
Picno Scale Emission Incidence Phase Elevation Period of
(m/pixel) (deg) (deg) (deg) Day
(deg)
035A7247.13 10.53 79.89 86.26 10.11 morning
070A1343.42 12.36 62.61 71.77 27.39 morning
561A25162.7 32.83 76.59 45.63 13.41 morning
753A33232.82 10.25 35.3 25.12 54.7 afternoon
753A34232.51 10.13 35.15 25.14 54.85 afternoon
814A07848.86 38.15 65.93 103.25 24.07 too low
257S69821.24 42.06 43.83 8.66 46.17 cloudy
673B54226.02 23.22 64.94 77.76 25.06 morning
673B56225.7 21.33 67.77 76.7 22.23 morning
NASA Headquarters
Public Affairs Office
Washington DC 20546-001
Email: eweigel@hq.nasa.gov
Document: FS-1995-08-016-HQ
Modified: August 1995
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