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Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: First Replica Of Historic 1903 Wright Flyer To Be Displayed
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Dwayne Brown
Headquarters, Washington, DC April 28, 1998
(Phone: 202/358-1726)
Michael Mewhinney
Ames Research Center, Moffett Field, CA
(Phone: 650/604-3937)
RELEASE: 98-70
FIRST REPLICA OF HISTORIC 1903 WRIGHT FLYER TO BE DISPLAYED
The first full-scale replica of the historic 1903 Wright
Flyer arrived today at NASA's Ames Research Center, Moffett Field,
CA, in preparation for public display this spring and wind tunnel
tests next January.
The replica is scheduled for a two-week test in Ames' 80-foot
x 120-foot wind tunnel -- the world's largest. During the test,
project engineers will study the replica's stability, control and
handling at speeds up to 30 mph in the wind tunnel. Test results
will be used to compile an historically accurate aerodynamic
database of the Wright Flyer.
Constructed by a team of volunteers from the Los Angeles
section of the American Institute of Aeronautics and Astronautics
(AIAA), using plans provided by the Smithsonian, the replica
features a 40-foot-4-inch wingspan reinforced with piano wire,
cotton wing coverings, spruce propellers and a double rudder.
"I can't think of anything as exciting as using modern
technology to test a replica of the biplane that Orville and
Wilbur Wright flew for the first time ever in 1903 at Kitty Hawk,"
said Pete Zell, Ames' wind tunnel test manager. "NASA is here as
a resource for the public and to inspire young people. This
project seeks to educate and inspire youth; it's much more than
dollars and cents."
Although it will replicate the 1903 Wright Flyer in design,
size, appearance and aerodynamics, some changes have been made to
strengthen the plane when it is mounted in the wind tunnel.
The full-scale replica was built with precise data using
Smithsonian drawings from the original airplane. Data obtained
from testing on this full-scale replica will provide a sound
technical basis for improving the flying qualities and safety for
the second full-scale airplane -- yet to be constructed. In the
wind tunnel, the replica will be powered by a NASA electric motor.
"The work of the Wright Brothers founded the science and
technology of aeronautics, and their accomplishments form one of
the grandest chapters in history," said Jack Cherne, TRW engineer
and chairman of the Wright Flyer Project.
In contrast to the Wright brothers, who took less than a year
to build their biplane, AIAA volunteers have spent their Saturdays
for the past 18 years planning and assembling the replica.
It also has undergone special testing as a prerequisite for
entering the NASA wind tunnel. One stipulation was static
testing, in which more than three times the flight load (or more
than 3,000 pounds) was applied successfully. Another NASA
requirement was propeller system testing, recently completed at
Able Corp. in Yorba Linda, CA.
The replica has about $100,000 worth of donated materials
from companies such as Northrop Corp./Aircraft Division, Torrance,
CA, which also provided the project a home base for 15 years;
International Die Casting, Gardena, CA; McDonnell Douglas, Long
Beach, CA; Rockwell International, Downey, CA; and TRW Redondo
Beach, CA.
Upon completion of the wind tunnel tests, the replica will be
transported to Los Angeles, where it will be put on permanent
display in the lobby of the Federal Aviation Administration (FAA)
Western Pacific Regional Office in Hawthorne, CA, to provide a
valuable resource for the community and surrounding schools. The
lobby will soon be renamed the "FAA Flight Deck" Museum and
include a variety of other exhibits depicting the history of aviation.
Using the wind tunnel test data, a second Wright Flyer will
be built by the AIAA volunteers and flown on Dec. 17, 2003,
commemorating the 100th anniversary flight of Orville and Wilbur
Wright at Kitty Hawk, NC. During a recreation of the Wright
brothers' first flight, the replica will fly low and travel at
only 30 mph, the same speed flown by the Wright brothers, whose
flight only traveled 120 feet during its 12 seconds in the air.
Fred Culick, 63, of Altadena, CA, a private pilot and an
aeronautics professor at the California Institute of Technology,
Pasadena, CA, will be the first to fly the airplane; he will
control it while lying on his stomach.
Orville and Wilbur Wright were responsible for a host of
aviation inventions, including wing warping, which provides
lateral control and allows an airplane to bank left or right.
They also invented the forward stabilizer, which controls the
airplane's up and down movement, and the moveable rear rudder,
which enables the pilot to counteract unwanted turns.
Further information about the Wright Flyer is available on
the AIAA Wright Flyer homepage at:
http://www.alumni.caltech.edu/~johnlatz/1903.html
-end-
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=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: MGS Views Mars Pathfinder Landing Site
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From the Mars Global Surveyor Home Page:
http://mars.jpl.nasa.gov/mgs/msss/camera/images/4_25_98_pathfinder_release/ind
ex.html
Mars Global Surveyor
Mars Orbiter Camera
Pathfinder Landing Site Observed by Mars Orbiter Camera
Mars Global Surveyor Mars Orbiter Camera Release: MOC2-46A, -46B, -45
Mars Global Surveyor Mars Orbiter Camera Image ID: 577743128.25603
P256-03
576946243.23703
P237-03
(A)[Image] (B)[Image]
(C)[Image]
To view images, click on image size links, below
(A) Viking Orbiter image of location of Pathfinder landing site landmarks
(mercator projection, scale 30 m (100 feet) per pixel) (GIF = 475 KB)
(B) MOC 25603, showing Pathfinder site at roughly 6.6 m (21.5 feet) per
pixel (GIF = 724 KB)
(C) MOC 23703 and 25603, showing "Big Crater" in stereoscopic viewing at
roughly 5m (16.4 feet) per pixel (JPG = 238 KB). Note: stereo effect is seen
when right eye views through red filter.
CAPTION
On its 256th orbit of Mars, the camera on-board the Mars Global Surveyor
spacecraft successfully observed the vicinity of the Pathfinder landing
site. The images shown above include a Viking image at roughly 30 m (100
feet) scale, and a portion of the MOC image reproduced at a scale of 6.6 m
(21.5 feet) per pixel. Also included is a stereoscopic image pair in
anaglyph format, made from the overlapping area of MOC 25603 and 23703. This
image is reproduced at a scale of 5 m (16.4 feet) per pixel. Image 23703 was
acquired on 13 April at 7:50 AM PDT; Image 25603 was acquired on 22 April at
1:11 PM PDT. The P237 observation was made from a distance of 675 km while
the P256 measurement was made from 800 km. The viewing angle for 23703 was
21.2њ, for 25603, 30.67њ, giving an angular difference of about 9.5њ. Owing
to the relief on "Big Crater," this relatively small angular difference was
in this case sufficient to show good stereo parallax.
The resolution of the MOC image that covered the Pathfinder landing site
(MOC 25603) was about 3.3 m or 11 feet per pixel. The Pathfinder lander and
airbags form a roughly equilateral triangle 5 m on a side. Noting that the
camera has not yet been focussed (it needs to be in the stable temperature
conditions of the low altitude, circular mapping orbit in order to achieve
best focus) and the hazy atmospheric conditions, the effective scale of the
image is probably closer to 5 m (16.4 feet). Thus, the scale of the image
was insufficient to resolve the lander (more than one pixel is needed to
resolve a feature). In addition, the relatively high sun angle of the image
(the sun was 40њ above the horizon) reduced the length of shadows (for
example, only a few boulders are seen), also decreasing the ability to
discriminate small features. Work continues to locate intermediate-scale
features in the lander and orbiter images in the hope of identifying the
precise landing site based on these comparisons.
Malin Space Science Systems and the California Institute of Technology built
the MOC using spare hardware from the Mars Observer mission. MSSS operates
the camera from its facilities in San Diego, CA. The Jet Propulsion
Laboratory's Mars Surveyor Operations Project operates the Mars Global
Surveyor spacecraft with its industrial partner, Lockheed Martin
Astronautics, from facilities in Pasadena, CA and Denver, CO.
Hа сегодня все, пока!
=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: Surprises from SOHO include tornadoes on the Sun [1/2]
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European Space Agency
Press Information Note Nr 15-98
Paris, France 24 April 1998
Surprises from SOHO include tornadoes on the Sun
The Sun has tall gyrating storms far larger and faster than tornadoes on the
Earth. This unexpected finding is among the latest results from the solar
spacecraft SOHO, to be announced at a European Space Agency press briefing
on 28 April. British scientists discovered the solar tornadoes in images and
data from SOHO's scanning spectrometer CDS. So far they have detected a
dozen such events. They occur most frequently near the north and south poles
of the Sun and are almost as wide as the Earth.
Steady windspeeds of 15 kilometres per second and gusts ten times faster
(which means 500,000 kilometres per hour) occur in the solar tornadoes. For
comparison, tornadoes on the Earth blow at 400-500 kilometres per hour. The
solar measurements are made by the Doppler effect -- the same principle as
that used by police radars to detect speeding motorists. The observed
wavelength of emission from hot oxygen atoms changes according to whether
the gas is moving towards the detector or away from it, and the CDS
instrument is very sensitive to these variations.
One of SOHO's main tasks is to trace the sources of the wind from the Sun
that pervades the Solar System. Gusts and shocks in the solar wind buffet
the Earth's environment, causing auroras and magnetic storms and endangering
satellites and power supplies. The newly discovered tornadoes may contribute
to the solar wind, especially to a fast windstream that emanates from
relatively cool parts of the solar atmosphere called coronal holes.
"We see the hot gas in the tornadoes spiralling away from the Sun and
gathering speed," says David Pike of the Rutherford Appleton Laboratory, UK,
who is co-discoverer of the solar tornadoes with Helen Mason of Cambridge
University. "These spectacular events in the Sun's atmosphere must have
widespread effects. Our next step will be to try to relate the solar
tornadoes to observations of the fast solar wind farther out in space, as
seen by other instruments in SOHO."
Built in Europe for the European Space Agency, SOHO carries twelve sets of
instruments provided by European and American investigators, and it was
dispatched into space on 2 December 1995 by a NASA launcher. SOHO is a
project of international cooperation between ESA and NASA.
Other news items concerning SOHO, included in what follows, are:
* The threat to technology from the increasingly active Sun.
* An explanation of why the Sun's atmosphere is so hot.
* A puzzle about why the Sun's thermonuclear core seems too cool.
* The Sun's game of tennis with alien atoms.
The Sunspot Bug
SOHO's scientists gathered at the Rutherford Appleton Laboratory this week,
on the second anniversary of full scientific operations which began in April
1996. They are celebrating the decision by ESA and NASA to extend their
mission to 2003. This means that SOHO, having observed the Sun in its
quietest state in 1996, will also see it at its most tumultuous, when the
count of dark sunspots on the Sun's face rises to a maximum around the year
2000.
During the last sunspot maximum, in 1989-91, solar storms caused power
failures in Canada and Sweden and destroyed or damaged several satellites.
Some computers crashed as a result of impacts by solar particles. Since then
the human species has become more dependent upon satellites and computers,
and advanced microchips are more vulnerable to the Sun's electromagnetic
effects and particles. To the Millennium Bug, a problem involving software
in the transition to the year 2000, one must add the physical threat of the
Sunspot Bug.
SOHO is the world's chief watchdog for the Sun. From a special vantage point
1.5 million kilometres out in space, where the Sun never sets, the
spacecraft observes solar activity for 24 hours a day. Its images go to the
regional warning centres of the International Space Environment Service,
which alert engineers responsible for power systems, spacecraft and other
technological systems to impending effects on the Earth's environment.
Western Europe is served from Paris-Meudon where forecasters obtain, every
day, SOHO's images of the whole Sun at four wavelengths from the extreme
ultraviolet imaging telescope EIT. Developed and operated by a French-led
consortium, EIT is like a weather satellite for the Sun. Its images reveal
the scenes of intense activity in the Sun's atmosphere that can trigger
solar flares and mass ejections.
SOHO's visible-light coronagraph LASCO, provided by a US-led team,
demonstrated in April 1997 its special ability to spot a mass ejection
heading towards the Earth, where it caused a mild storm. CELIAS (currently
under Swiss leadership) is the solar-wind instrument on SOHO, which confirms
the arrival of a mass ejection 30-60 minutes before it reaches the Earth. By
measuring the speed and density of the material ejected from the Sun, CELIAS
gives a clear warning of the likely severity of the storm.
As the solar storms increase in ferocity and frequency in the next year or
two, so will SOHO's importance in this regard. It is the flagship of a
multinational fleet of spacecraft monitoring the Sun and its effects. Other
members of the fleet include the ESA-NASA Ulysses solar-polar spacecraft and
the forthcoming ESA-NASA flotilla of four satellites, Cluster II, to observe
and interpret effects in the Earth's vicinity. In all of this work, the
monitoring of the Sun goes hand-in-hand with fundamental research and
discovery.
"The scientific surprises announced today illustrate SOHO's special role,"
says Roger Bonnet, ESA's director of science. "To make sense of the Sun, and
if possible to forecast the storms and long-terms changes which affect our
technology and our weather on the Earth, are urgent tasks for space
research. While SOHO provides early warnings of solar outbursts, it also
looks for unknown and basic features of the Sun that may make forecasting
better. In SOHO the distinction between "useful" and "fundamental" science
is abolished."
The Sun's super-hot and dynamic atmosphere
SOHO has recently solved part of a long-standing mystery about the Sun,
according to Eric Priest of St Andrews University, UK, who reviewed its
achievements in fundamental studies of the Sun's atmosphere at today's press
briefing. For more than half a century, scientists have known that the
atmosphere reaches temperatures of millions of degrees C, compared with less
than 6000 degrees at the Sun's visible surface. How does the atmosphere
become so astoundingly hot?
"SOHO casts doubt on one leading theory of the atmospheric heating, and
confirms another," says Priest. "We have checked the idea that magnetic
waves might be responsible. We have been able to observe for the first time
some of the proposed waves, but they fade out before they reach the hottest
part of the atmosphere. On the other hand we now have plenty of evidence
that at least part of the heating comes from a clash of magnetic field
lines. They tangle like spaghetti in the solar atmosphere and reconnect,
causing thousands of explosions every day that release energy into the
atmosphere. The beauty and elegance of this theory is that it explains a
wide variety of different phenomena in a natural way."
The evidence includes an ever-changing carpet of outgoing and ingoing
magnetic fields on the Sun's visible surface. US scientists using SOHO's
MDI/SOI instrument have discovered that the pattern of the magnetic carpet
changes completely every 40 hours. That implies a continual rearrangement of
loops in the atmosphere, by magnetic reconnections. The resulting explosions
appear as jets of gas detected by SOHO's SUMER instrument, and as bright
spots called blinkers in the CDS instrument.
The newly-found solar tornadoes also figured in Priest's review of SOHO's
achievements. They reveal just how dynamic the atmosphere is, and may well
be an important cause of the solar wind. One of SOHO's specified tasks is to
trace the origins of the solar wind and the accelerators that drive it out
into the Solar System in all directions.
The coronal holes from which the fast solar wind emanates are concentrated
towards the Sun's poles. In these regions the local magnetic field creates
no barrier to hot gas leaving the Sun and attaining a windspeed of 750
kilometres per second. By contrast, the magnetically congested equatorial
zone is the source of a relatively slow and variable solar wind of around
400 kilometres per second.
In an early result from SOHO, members of the US-led team for the ultraviolet
coronagraph UVCS detected a remarkable acceleration of oxygen atoms leaving
the Sun from the relatively cool coronal holes, the source of the fast wind.
The team suggests twisting magnetic waves as the driver. These are possibly
related to the tornadoes.
As for the slow wind, the visible-light coronagraph LASCO observes many
large and small mass ejections leaving the Sun, propelled by major and minor
explosions. Several mass ejections can occur almost simultaneously at widely
scattered places in the Sun's equatorial zone. LASCO team members in the UK
consider that the mass ejections contribute an important fraction of the
slow wind, and that the material can undergo acceleration at a wide range of
distances from the Sun.
Hа сегодня все, пока!
=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: WDC-A R&S Launch Announcement 12931: STS 90
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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 12931
COSPAR/WWAS USSPACECOM NUMBER
SPACECRAFT INTERNATIONAL ID (CATALOG NUMBER) LAUNCH DATE,UT
STS 90 1998-022A 25297 17 APRIL 1998
DR. JOSEPH H. KING, DIRECTOR, WDC-A-R&S.
[PH: (301) 286 7355.
E-MAIL: KING@NSSDCA.GSFC.NASA.GOV
24 APRIL 1998, 13:00 UT]
Further details with be in the next SPACEWARN Bulletin
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
SPACEWARN home page: http://nssdc.gsfc.nasa.gov/spacewarn/
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=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: WDC-A R&S Launch Announcement 12932: Globalstar 5 - 8
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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 12932
COSPAR/WWAS USSPACECOM NUMBER
SPACECRAFT INTERNATIONAL ID (CATALOG NUMBER) LAUNCH DATE,UT
GLOBALSTAR 5 1998-023A 25306 24 APRIL 1998
GLOBALSTAR 6 1998-023B 25307 24 APRIL 1998
GLOBALSTAR 7 1998-023C 24308 24 APRIL 1998
GLOBALSTAR 8 1998-023D 24309 24 APRIL 1998
DR. JOSEPH H. KING, DIRECTOR, WDC-A-R&S.
[PH: (301) 286 7355.
E-MAIL: KING@NSSDCA.GSFC.NASA.GOV
28 APRIL 1998, 15:00 UT]
Further details will be in the next SPACEWARN Bulletin
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
SPACEWARN home page: http://nssdc.gsfc.nasa.gov/spacewarn/
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=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: Engineering, Art Come Together In DS-2 'Spider'
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From The "JPL Universe"
April 17, 1998
Engineering, art come together in DS2 'spider'
By SUZANNE D'MELLO, New Millennium Program outreach coordinator
In January 1999, Deep Space 2's twin probes will take off for
Mars riding piggyback aboard the Mars Polar Lander spacecraft.
The experimental mission is designed to test a number of
advanced, miniature instruments and systems inside the probes to
see if they can perform experiments beneath Martian soil after
surviving crushing impacts on landing and extremely cold
temperatures.
On their journey to the red planet, each probe will be housed
in a protective shell that will be attached to the larger
spacecraft with a device called a "spider," which is part of an
overall attachment structure. The spider is so-called because its
curved, three-legged frame resembles the body of that arthropod.
What is striking about this seemingly fragile piece of
aluminum is that it's not only functional hardware--needing to
withstand the extreme conditions of launch and travel into deep
space--but with its spare, elegant, Art Deco-like form, is
industrial design at its most beautiful.
Satish Krishnan, 23, who designed the spider, was just a few
months out of college when assigned the task by DS2's mechanics
lead engineer, Tom Rivellini, in late 1996. Rivellini provided
Krishnan with an initial concept, which required that the egg-
shaped shell be held on to at three, equidistant points.
With a preliminary design of a three-pronged structure in
hand, Krishnan worked closely with Rivellini, structural
analysts Darshan Sutharshana and Faz Keyvenfar, manufacturing
engineer Bob Moncada, machinist Nelson Leiva, and DS2's graphics
designer, Frank Ramirez, during the year it took to complete the
part. "This had to be a collaboration from the very start,"
Krishnan pointed out. "The very nature of this part required it."
Heavily constrained by issues of cost and manufacturability
while working concurrently in JPL's "faster, better, cheaper"
era, he adapted his design several times on the advice of the
others. The single most important question that Krishnan faced in
creating the spider was whether to make it one part or three. "We
knew that making the spider a single part would be very
difficult," he said, "but assembly of three parts would have been
a nightmare because of the tolerance mismatches we'd have to
contend with--tolerance is the degree of precision required in a
dimension. So we decided to bite the bullet and make it a single
part."
"This is the toughest part I've ever worked on," admitted
Moncada, who added, "The part wouldn't have been as rigid or
strong if it had been three pieces, and this was the cleanest,
easiest way to mount the shell inside the spider."
Making the spider a single part was not that much easier a
task, either. The finished spider, which weighs a mere 590 grams
(1.3 pounds), had to be crafted out of a giant, 250-kilogram
(550-pound) billet of aluminum.
Why such a large chunk? Detailed drawings hadn't yet been
created when Krishnan decided to make the device a single part
instead of three. Ordering a large billet of metal ensured that
engineers would have plenty of material to work with once
Krishnan figured out the outer dimensions of the spider.
Leiva machined the spider into its final shape using the
process of "undercutting" to hollow out the legs of the spider.
Undercutting, a process invented by JPL engineer Don Bickler for
the Mars Pathfinder mission, is an innovative way of hollowing
out a piece of metal without having to cut it in two. Bickler
used the process for the Sojourner rover's "rocker bogie"
suspension system, which allowed the rover to negotiate the
Martian terrain with its system of joints that rotated and
conformed to the contour of the ground.
To drill holes in the precise locations that Krishnan had
pinpointed in the legs of the spider, Leiva used a series of fine
tools, knowing that if he was off by even an infinitesimal amount
the part wouldn't be functional. At one point he even had to
contend with having the material move while he tried to machine
it. After consulting with materials engineers the problem was
solved, and Leiva completed the spider in October 1997.
The device has since successfully passed all its tests and
Krishnan is very pleased with its design. "I think when you look
at this part, what makes it interesting is the method we used to
hollow it out," he said. "I don't think it would have actually
looked as neat if we had used an alternative method."
Though Krishnan may be indebted to Bickler for the aesthetics
of his design, he also has Leiva's extraordinary craftsmanship to
thank for producing an industrial device that is a perfect blend
of functionality and beauty.
####
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=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: STARDUST Update - April 28, 1998
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STARDUST Status Report
April 24, 1998
Ken Atkins
STARDUST Project Manager
The spacecraft assembly effort this week was focused on completing most of
the remaining power harness wrapping for protection in space, completing the
Whipple cometary dust shields for the solar arrays, continuing preparations
to install the flight solar arrays on the spacecraft, and interface testing
of the power electronics and navigation camera.
Work also moved ahead on completing the installation of the Cometary and
Interstellar Dust Analyzer (CIDA) electronics and installation and checkout
of the spacecraft's central computer.
We also completed some final testing on the Sample Return Capsule (SRC)
indicating it is essentially complete and ready for mating with the carrier
spacecraft. With the camera installation, all flight instrument electronics
and the flight Dust Flux Monitor (DFM) are now on the flight spacecraft.
We also received the star cameras this week. These are used to determine the
spacecraft's attitude in deep space. The team also performed some practice
comet encounter simulations involving the CIDA and the navigation camera,
with software simulations for the Inertial Measurement Units (IMUs) and the
Dust Flux Monitor (DFM). Things are beginning to come together as a system.
The project delivered aerogel samples to the California Science Center in
Los Angles on Thursday for an extended display in the museum's "Future
Applications" area.
For more information on the STARDUST mission - the first ever comet sample
return mission - please visit the STARDUST home page:
http://stardust.jpl.nasa.gov
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=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: Mars Global Surveyor Prepares To Enter Solar Conjunction Period
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From The Mars Global Surveyor home page:
http://mars.jpl.nasa.gov/mgs/target/solarconj.html
MGS Prepares to Enter Solar Conjunction Period
[Image] [Image]
Overhead View of Earth & Mar Global Surveyor's View
Mars of the Sun & Earth
[Image]
Line of Sight Between Earth and Mars
During solar conjunction, the Sun gets in
between the Earth and the MGS spacecraft,
severely limiting communications. In the
above picture, MGS is on the verge of
entering the solar conjunction period.
The Mars Surveyor Operations Project is in the process of preparing the Mars
Global Surveyor spacecraft for the solar conjunction period which begins on
April 30 and ends on May 26. The beginning of the solar conjunction period
marks the end of the first Science Phasing Orbit (SPO-1) period during which
data was acquired. During the interval around solar conjunction the Sun will
obscure the line of sight between Earth and Mars, making it virtually
impossible to receive radio signals from the spacecraft.
The Sun is a strong source of electromagnetic activity, and it wreaks havoc
with the spacecraft's radio signal, essentially reducing the spacecraft's
data rate to Earth to zero for the period centered around conjunction.
Mission planners and telemetry engineers define this problem area as
occurring when the Sun-Earth-MGS angle is less than 7 degrees; a relatively
"quiet" Sun can mean that data can be successfully returned at angles as
small as 3-5 degrees.
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=SANA=
Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: Future Mars Probe Joins All-Canadian Rocket Mission
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Future Mars probe, ozone research, and student experiments join all-Canadian
rocket mission
The Canadian Space Agency's ACTIVE rocket mission will launch into space on
Tuesday, April 28 at 8:00am EDT carrying a payload supporting two of
Canada's most ambitious space science projects -- the future Mars Probe,
Canada's first mission to Mars scheduled for launch in the summer of 1998;
and OSIRIS, widely considered to be the world's most advanced ozone
measuring instrument.
The ACTIVE payload will be launched from the SpacePort Canada commercial
rocket range, located just outside Churchill, Manitoba. As part of the
mission, CSA has arranged for local students from Churchill to also fly
their own ozone-research experiments onboard the rocket.
Bristol Aerospace Limited of Winnipeg will supply a Black Brant 9 rocket to
take the CSA payload into space at a speed of approximately 3,500 km/hr to
an altitude of 360km. Bristol was also responsibe for the design and
development of the payload support systems for the integration and test off
the CSA science experiments and for range integration/test and launch
support activities.
A Test Run for Canada's First Mission to Mars
The Auroral Composition and Toroidal Ion Velocity Experiment (ACTIVE) is an
opportunity to test Canada_s first scientific instrument to Mars, scheduled
for launch from Japan in July 1998. Onboard the Japanese spacecraft
Planet-B, the CSA's Thermal Plasma Analyser (TPA) will sample the Martian
atmosphere upon its arrival in late 1999, measuring energetic particles
similar to those that cause the Northern Lights above Canada. These data
will help scientists better understand Earth's own atmospheric systems and
help prepare for future human trips and possible colonization of the Red
Planet. A prototype of the TPA instrument was refurbished for the ACTIVE
mission, which will test the Mars probe and at the same time make important
contributions to science closer to home. The ACTIVE principal investigator
is Dr. Greg Garbe, University of Calgary and the TPA principal investigator
is Dr. Andrew Yau, University of Calgary.
A Piece of the World's Most Ambitious Ozone Research Project
The POSSEX/MOZE suite of CSA instruments is designed to work in conjunction
with Canada's most ambitious ozone-research project -- OSIRIS (Optical
Spectrograph and Infra-Red Imaging System), scheduled to launch on a Swedish
scientific satellite in March 1999. POSSEX will measure the polarization of
the scattered sunlight in the atmosphere using four photometers. Results
from this experiment will be used to provide more thorough analysis of the
OSIRIS data. The MOZE experiment is a student project to measure ozone
concentration as a function of altitude.The principal investigator for the
OSIRIS experiment is Dr. Ted Llewellyn, University of Saskatchewan and the
principal investigator for POSSEX is Dr. Wayne Evans, Trent University.
A GPS Test Flight by Calgary Company
In addition, the ACTIVE mission will test a prototype global positioning
system from Novatel of Calgary that will provide accurate positional
information of the rocket throughout its flight.
Student Activities
As part of its Space Education and Awareness outreach program, the Canadian
Space Agency has arranged for the participation of students from Churchill's
Duke of Marlborough High School.
The student portion of the rocket payload, named MOZE (Measurement of Ozone
Experiment), will measure ozone concentration in the atmosphere as a
function of altitude. It will use two photometers of the same type as the
CSA's POSSEX experiment, but with different filters.
Under the direction of science teacher Doug Isaak, the Churchill science
students have been working on a number of mission-related projects about the
atmosphere, space and the environment. The students, from grades seven to
10, have been "consulting" with mentors Dr. Wayne Evans of Trent University
and Dr. Ted Llewellyn of the University of Saskatchewan, who together are
among Canada's leading ozone researchers. The students received a pre-flight
visit and "briefing" from Dr. Llewellyn in late March.
As part of their research, the Churchill students visited Ottawa in February
to meet with representatives from the Canadian Space Agency and Routes Inc.,
the Kanata-based space-engineering firm that developed the ozone instruments
for this mission. In March, the students visited Bristol Aerospace in
Winnipeg for a tour of their facilities and to "inspect" their payload
during its integration into the Bristol Black Brant 9 rocket being used for
the ACTIVE mission.
The students will see the cumulative sum of their efforts take off at the
April 27 launch at SpacePort Canada, near Churchill. During a post-launch
reception, students will make a public presentation based on the real-time
data collected from the ACTIVE launch.
For more information:
Isabelle Hudon
Manager, Media Relations
Canadian Space Agency
(514) 926-4350
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Дата: 30 апреля 1998 (1998-04-30)
От: Alexander Bondugin
Тема: Asiasat Lunar Swingby - WHY?
Привет всем!
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New Item: Asiasat-3 to perform lunar flyby to try to reach usable orbit.
Question: It's bold, imaginative, and impressive, but - why?
Asiasat-3 was stuck in a 12-hour geosync transfer orbit last December 25 when
the Proton launch vehicle's fourth stage failed to perform its apogee kick
burn. The burn would have partially circularized the orbit and a subsequent
payload burn would have completed circularization.
For Asiasat details see Hughes's web page,
www.hughespace.com/factsheets/601/asiasat_3/asiasat_3_3S.html
Orbital basics:
A satellite in a 200-km circular orbit is travelling 7789 m/sec.
To raise its apogee to the geosync altitude requires a velocity of 10,238 m/s.
That's a delta-V of 2450 m/s.
To perform a lunar fly-by requires about 10,970 m/s.
That's a delta-V of 3180 m/s. Only 1% less than the next step.....
To escape Earth's gravity requires 11,010 m/s.
That's a delta-V of 3221 m/s.
For the geosync transfer, the transfer orbit results in the satellite reaching
geosync altitude with a velocity of 1597 m/s.
Circular orbital velocity at geosync altitude is 3075 m/s (escape velocity at
this altitude is 4312 m/s).
To circularize its orbit at geosync altitude requires a delta-V of 1480 m/s.
If a plane change is required, it must also be performed at apogee. From a 52
degree inclination transfer orbit, that requires approx 1000 m/s.
Both burns (posigrade to circularize and out-of-plane to shift inclination) can
be performed simultaneously with a single burn which is the root-sum-square of
the two burns. For a 52 degree inclination this is about 1800 m/s.
For the lunar variant to GEO from a 200-km circular parking orbit,
two burns are required:
Insert to translunar, add 3180 m/s to the 7789 circ velocity.
Brake into geo on return from lunar distance, subtract 1130 m/s.
Asiasat was already in a geosync transfer orbit (approx 200 by 40,000) with
perigee velocity of 10,238 m/s. This required an additional 730 m/s to reach
lunar fly-by. Adding in the return braking burn (1130) gives a total delta-V
for this maneuver plan of 1860 m/sec.
Performing a straight apogee kick and plane change burn, recall, costs only
1800 m/s. The two maneuvers therefore are approximately equivalent in delta-V
requirements. There appears to be no delta-V advantage to the lunar variant.
Question: If Asiasat-3 has the onboard delta-V to do the lunar fly-by plan, it
would have had enough to do a direct insertion at apogee. Why didn't Asiasat-3
perform that burn in December?
If the target orbit is not a circular geosync orbit, the braking burn may be
performed at a greater altitude, and so wouldn't be as much. Perhaps Asiasat is
aiming at a 24-hour geosynchronous but non-stationary orbit, say 25,000 by
55,000 km eccentric.
Alternately, operators didn't realize they had adequate delta-V in December,
and by the time they did, the Asiasat's 12-hour parking orbit had shifted (the
line of apsides had rotated) so that the apogee was too far from the intended
equatorial plane.
This will be cleared up in the Hughes press conference tomorrow, I expect.
Using lunar flyby for geosync insertion was discussed in my article in OMNI in
July 1984 (I don't know of any earlier publication of it but I'd be surprised
if somebody hadn't thought of it and documented it long before), although I
concentrated on the military threat from a killer satellite in reverse geosync.
It would get there using a lunar swingby, and would threaten all assets in the
whole arc. I recall discussing it with Marty Jenness and other MPAD trajectory
experts and we saw there might even be advantages to going into direct geosync
orbit for launches from high latitudes where the plane change was costly. In
1989 I informally discussed this option with Yuri Smetanin, the director of the
Zenit booster program at the Yuzhnoye Corporation in Dnepropetrovsk.
Other Russians also re-invented this maneuver, in a 1995 study to place Yamal
commercial communications satellites into GEO by using Molniya-booster
launchings from Plesetsk and a lunar flyby. This was published in the 1996 book
"RKK Energiya 1946-1996". Page 484 has a schematic of the trajectory plan.
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