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(meteorobs) Excerpts from "CCNet 102/2001 - 24 September 2001" [Deep Space 1!]
Plenty of news on probe Deep Space 1's exciting bypass of Comet Borrelly this
past Saturday. What a banner weekend for the study of comets - and so, we may
hope, for the study of meteoroid streams. No mention below of amateur Ralph
Pass's critical participation in the DS1 flyby... Oh, well - unlike for some
professionals perhaps, amateurs really do derive their greatest satisfaction
merely from contributing to human knowledge. Would you agree, Ralph? :)
Clear skies!
Lew Gramer
------- Forwarded Message
From: Benny Peiser <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet 102/2001 - 24 September 2001
Date: Mon, 24 Sep 2001 10:50:14 +0100
CCNet 102/2001 - 24 September 2001
"Deep Space 1 plunged into the heart of comet Borrelly and has lived
to tell every detail of it! The amazing little spacecraft was
fantastically successful in its encounter with the mysterious comet on
September 22. Many recent mission logs have described why this probably
would not work, but it did work, and it worked far far better than expected.
In fact, everything went so well on encounter day that my biggest
concern was the seismic risk to Southern California when thunderous
applause erupted in mission control upon the return of the images!
When we saw them, the room was just filled with almost unbridled elation."
Marc Rayman, SpaceDaily, 23 September 2001
"This year's Leonid meteor shower will be so big it poses a threat
to the thousands of satellites orbiting Earth. At least one satellite
could be shorted out when the Earth passes through the dusty trail of
the comet Tempel-Tuttle, astronomers predict. [...] "A direct impact of
even a single grain of dust could be catastrophic for a satellite,"
explains Mark Bailey of the Armagh Observatory, Northern Ireland. "The
particle would vaporize when it struck, creating a plasma," he says.
"This cloud of electrically charged gas could short-circuit the
satellite's delicate electronics".
Philip Ball, Nature Science Update, 24 September 2001
(1) A QUICK SNAP SHOT OF COMET SCIENCE IN DEEP SPACE
SpaceDaily, 23 September 2001
(2) SPACECRAFT CAPTURES COMET IMAGES
Yahoo! News, 23 September 2001
(3) DEEP SPACE 1 DEFIED ODDS, PHOTOGRAPHS COMET IN RISKY FLYBY
Space.com, 22 September 2001
(4) DEEP SPACE 1 MISSION STATUS
Ron Baalke <baalke@jpl.nasadot gov>
[...]
(6) NOVEMBER'S LEONID METEOR SHOWER COULD CAUSE COMMUNICATIONS HAVOC
Nature Science Update, 24 September 2001=20
[...]
======================================================================
(1) A QUICK SNAP SHOT OF COMET SCIENCE IN DEEP SPACE
>From SpaceDaily, 23 September 2001
http://www.spacedaily.com/news/deep1-01l.html
Unlike D1's flyby of the asteroid Braille in August 1999, SpaceDaily has been
assured that despite the delay in releasing the images, they are "sharp and in
focus", and that there are about 30 image in all.
by Marc Rayman
Pasadena - September 23, 2001
Deep Space 1 plunged into the heart of comet Borrelly and has lived to tell
every detail of it! The amazing little spacecraft was fantastically successful
in its encounter with the mysterious comet on September 22. = Many recent
mission logs have described why this probably would not work, = but it did work,
and it worked far far better than expected.
In fact, everything went so well on encounter day that my biggest = concern was
the seismic risk to Southern California when thunderous applause = erupted in
mission control upon the return of the images! When we saw them, the = room was
just filled with almost unbridled elation.
We had low expectations, so the enormity of the success was that much = more
wonderful. The tremendous excitement stems from being the very first = humans
ever to glimpse the secrets that this comet has held since the birth of = the
solar system.
In addition, after years of nursing this aged and wounded bird along -- = a
spacecraft not designed to explore comets, a probe that exceeded its objectives
more than 2 years ago -- after struggling to keep it going through long nights
and stressful days, to see it perform its = remarkably complex and risky
assignment so well was nothing short of incredible. I honestly did not think it
was up to the task. In fact, even though we = had strong indications during the
encounter that it was collecting the data = we wanted, I tried to keep everyone
from getting too excited. I felt we = had to accomplish two key tasks: 1) get
the science data from the spacecraft = to Earth, and 2) persuade ourselves we
weren't dreaming. We've now done = both!
The images and other data we collected from comet Borrelly are going to = make
great contributions to scientists' efforts to learn more about these intriguing
members of the solar system family. We're going to gain a = great deal of
completely new and absolutely fascinating insights into comets = and perhaps
into the origin and evolution of Earth.
This log is short because your correspondent is thoroughly exhausted. = The last
few logs describe what we hoped to accomplish, and one of the = great surprises
of the day is that we achieved everything we set out to. JPL = will be releasing
pictures and other information through its Media Relations Office in the coming
days.
There is a small chance there will be a new log later this week. More = likely
however, the next one will be early in November. Your loyal = correspondent is
scheduled to attend an international conference on space exploration in = just a
few days.
Following that will be some time to return to Earth after this cosmic = high,
and then the logs will resume with a more thorough description of this = truly
historic event. You will read about the exciting science, the = challenging
engineering, and the spectacular human drama that collectively add up = to a
truly astonishing success story.
And you will read about the end of the Deep Space 1 Extended Mission = and its
brief follow-on, which I like to call the Deep Space 1 Hyperextended Mission. So
there's more to come in the continuing exciting adventures = of Deep Space 1,
one of humankind's most wonderful ambassadors to the = cosmos.
Deep Space 1 is now 1.6 million kilometers, or 1 million miles, past = comet
Borrelly, and is nearly 1.5 times as far from Earth as the Sun is and = 575
times as far as the moon. At this distance of 220 million kilometers, = or 137
million miles, radio signals, traveling at the universal limit of the = speed of
light, take 24 and a half minutes to make the round trip.
Marc Rayman is the project manager for the Deep Space 1 program
Copyright 2001, SpaceDaily
======================================================================
(2) SPACECRAFT CAPTURES COMET IMAGES
>From Yahoo! News, 23 September 2001
http://dailynews.yahoo.com/h/ap/20010923/ts/comet_encounter_5.html
By ANDREW BRIDGES, AP Science Writer=20
LOS ANGELES (AP) - A NASA (news - web sites) spacecraft captured dozens = of
images of a comet during a weekend flyby, providing scientists only the second
glimpse ever of the core of one of the glowing bodies of dust = and ice.=20
Scientists said the Deep Space 1 probe flew within 1,360 miles of the = comet
Borrelly, capturing as many as 50 images of its nucleus at varying resolutions.
Scientists expect to receive the last images and other = data from the
spacecraft by Monday.=20
National Aeronautics and Space Administration officials say they will = not
release any images or data from the flyby until Tuesday. However, = scientists
gave hints of what the spacecraft saw and recorded, including pictures = of dust
and ice boiling off the comet's surface.=20
``This data set will make a significant contribution to the body of
knowledge we have about comets,'' Robert Nelson, the mission's project
scientist at NASA's Jet Propulsion Laboratory, said Sunday.=20
Scientists are interested in comets because they are thought to contain pristine
examples of the building blocks of our solar system from its = birth 4.5 billion
years ago.=20
The glowing veil of dust and gas that envelops Borrelly is perhaps as = big as
the Earth, but the comet's nucleus appears in the images to be just 2.5 miles
wide by 5 miles long, Nelson said.=20
Borrelly was at its most active during Saturday's flyby, kicking off material
that will give scientists clues about the comet's composition. = The encounter,
about 137 million miles from Earth, came about a week after = the comet's
closest approach to the sun on its seven-year orbital path.=20
Deep Space 1's instruments also measured ions, electrons, gases and Borrelly's
magnetic and electrical fields.=20
``We collected a large amount of data on this previously completely mysterious
body,'' said Marc Rayman, the mission's project manager. = ``It's going to take
some time to understand all the secrets this body may be hiding.''=20
Engineers had feared comet particles traveling at 36,900 mph would = batter or
destroy the aging probe, which completed its primary mission of testing = a
dozen innovative technologies two years ago. As of Sunday, preliminary = data
indicated the spacecraft remained in good health.=20
The European Space Agency's Giotto was the first and only other = spacecraft to
ever spy a comet nucleus when it flew past Halley in 1986.=20
In those images, Halley spewed fountains of ice and dust as the sun's = rays
warmed the comet's surface.=20
The encounter was a bonus for Deep Space 1, which is nearly out of fuel = and
will be turned off by NASA later this year.
On the Net:
Deep Space 1: http://nmp.jpl.nasadot gov/ds1/
Copyright 2001, Yahoo! News
======================================================================
(3) DEEP SPACE 1 DEFIED ODDS, PHOTOGRAPHS COMET IN RISKY FLYBY
>From Space.com, 22 September 2001
By Robert Roy Britt
Senior Science Writer
NASA's Deep Space 1 spacecraft defied deadly odds late Saturday, = dodging
potentially mission-ending comet dust while sucking down its final = drops of
fuel in making a successful flyby of comet Borrelly.
The craft snapped black-and-white photos of the comet's nucleus from = inside
the coma, a halo of dust grains and atomic material burned off the = comet by
the Sun. It is only the third time a spacecraft passed close enough to capture
images of a comet's nucleus.
Donald Yeomans, a comet expert at NASA's Jet Propulsion Laboratory, = said he
and his colleagues had gotten a sneak peak of about 30 images Saturday evening
and that full resolution versions would be downloaded from the spacecraft to
Earth overnight and into Sunday.
"These are really remarkable," Yeomans said in a telephone interview Saturday
night. "As expected, there were lots of surprises."
Yeomans couldn't say what those surprises were. The images will be = released at
a press conference in coming days. But he said they would be very important and
useful for the study of comets.=20
Some 30 ecstatic mission managers at JPL watched the images download = from a
craft that had succeeded in doing something it wasn't designed to do, = and
pulling it off after a long and battering trip that is near its end.
"There was sustained applause," Yeomans said.
Deep Space 1 passed approximately 1,250 miles (2,000 kilometers) from = the
comet while traveling at 36,900 mph (16.5 kilometers per second).=20
Twin Russian spacecraft, Vega 1 and Vega 2, imaged comet Halley in = March 1986.
The snapshots helped direct a Halley flyby later that same month = by the
European Space Agency's Giotto mission, which buzzed its target at = just 373
miles (600 km) away.
But Deep Space 1 was not designed for a comet flyby, and NASA had = worried that
dust might pummel the unprotected craft. It was a game of odds, = and the probe
appears to have sneaked between the widespread particles = unharmed.
"There was no evidence of a dust hit," Yeomans said.
The encounter took place at about 6:30 p.m. ET, roughly 125 million = miles (200
million kilometers) from the Sun, between the orbits of Earth and = Mars.
Signals confirming the successful encounter were received on Earth at = 6:43
p.m. ET, and data containing the first clues to the composition of the = comet
came a few hours after the close brush with the comet.
Researchers know very little about the composition of comets. But they = are
considered to be pristine representatives of the material that was = present
when the solar system formed.
The press conference may be scheduled for Tuesday, but that was not immediately
clear. [SPACE.com will provide continuing coverage as this = story unfolds and
the images are released.]
During the flyby of comet Borrelly, Deep Space 1 had also been = instructed to
take other measures of the icy rock. The probe was asked to produce = infrared
images that would help researchers explore the comet's surface. And = sensors
that monitor the ion propulsion were reprogrammed to listen for = magnetic
fields and plasma waves in and around the comet.
This data all appeared to be gathered and would be downloaded through = the
weekend, Yeomans said.
Other researchers have planned ground-based observations of comet = Borrelly, as
well as studies using the Hubble Space Telescope. They hope to = combine all the
data, along with what Deep Space 1 has gathered, to paint a = detailed picture
of the comet.
"The images and other data we collected from comet Borrelly so far will = help
scientists learn a great deal about these intriguing members of the = solar
system family," said Dr. Marc Rayman, project manager of Deep Space 1.
Several hours before the encounter, the spacecraft began observing the comet's
environment, JPL officials said. The action increased about an = hour and a half
before the closest approach, when for two minutes the = probe's infrared
spectrometer collected data that will help scientists = understand the overall
composition of the surface of the comet's nucleus.=20
Deep Space 1 took its first black-and-white image of the comet 32 = minutes
before the closest pass, and the best picture of comet Borrelly was = taken just
a few minutes before closest approach, according to plan, mission manager
said.=20
Two minutes before closest approach, ion and electron monitors that = were
originally designed to monitor the craft's engine were used instead to examine
dust and gas near the nucleus.=20
The flyby is one more feather in the cap for Deep Space 1, which = launched in
1998 and was designed to test a dozen futuristic technologies, = including its
high-tech ion engine. Science was never a primary goal of the mission.
Rayman had said before the flyby that besides the dust, he was = concerned that
the craft might run out of the fuel it uses to make small = adjustments to its
attitude and trajectory. And because of a previous failure to = its
star-tracking instrument, Deep Space 1 had to use the same camera that obtained
the comet images as a navigation device.
The craft has also been twice battered by solar storms. And it is = thought to
be very low on hydrazine, a fuel it uses to fire thrusters that adjust = its
attitude and direction.
Rayman, part of a team of about dozen people who now monitor the craft during an
extended mission period, said before the encounter that it's = as though Deep
Space 1 "is kept flying with duct tape and good wishes."
So how did it feel Saturday night?
"It was just tremendously exciting to see this aged and wounded bird = pull off
this remarkably complex and risky assignment so well," an exhausted Rayman said.
"I honestly did not think it was up to that task."
If the probe continues in good health, engineers will run its ion = engine
through a series of tests that were considered too risky before. The = tests may
cause the ion engine to fail. By late November, if the craft is = still
operating, NASA will cease communications with it.
Copyright 2001, Space.com
======================================================================
(4) DEEP SPACE 1 MISSION STATUS
>From Ron Baalke <baalke@jpl.nasadot gov>
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.nasadot gov
Deep Space 1 Mission Status
September 22, 2001=20
Deep Space 1's risky encounter with comet Borrelly has gone extremely = well as
the aging spacecraft successfully passed within 2,200 kilometers = (about 1,400
miles) of the comet at 22:30 Universal Time (3:30 p.m. PDT) = today.=20
"The images and other data we collected from comet Borrelly so far will = help
scientists learn a great deal about these intriguing members of the = solar
system family," said Dr. Marc Rayman, project manager of Deep Space 1 = at
NASA's Jet Propulsion Laboratory. "It's very exciting to be=20 among the first
humans to glimpse the secrets that this comet has held = since before the
planets were formed."=20
Signals confirming the successful encounter were received on Earth at = 3:43
p.m. PDT, and data containing the first clues to the composition of the comet
came a few hours after the close brush with the comet.=20
Mission managers confirmed that the spacecraft was able to use all four = of its
instruments at Borrelly. Data will be returned over the next few = days as the
spacecraft sends to Earth black-and-white pictures, infrared spectrometer
measurements, ion and electron data, and measurements of = the magnetic field
and plasma waves around the comet. Pictures of the comet = will be released
after they are all sent to Earth in the next few days.=20
Several hours before the encounter, the ion and electron monitors began
observing the comet's environment. The action increased about an hour = and a
half before the closest approach, when for two minutes the infrared spectrometer
collected data that will help scientists understand the = overall composition of
the surface of the comet's nucleus. Deep Space 1 began = taking its
black-and-white images of the comet 32 minutes before the = spacecraft's closest
pass to the comet, and the best picture of comet Borrelly was = taken just a few
minutes before closest approach, as the team had planned. = Two minutes before
the spacecraft whizzed by the comet, its camera was = turned away so that the
ion and electron monitors could make a careful = examination of the comet's
inner coma the cloud of dust and gas that envelops the = comet.
Scientists on Deep Space 1 hope to find out the nature of the comet's surface,
measure and identify the gases coming from the comet, and = measure the
interaction of solar wind with the comet.=20
Deep Space 1 completed its primary mission testing ion propulsion and = 11 other
advanced, high-risk technologies in September 1999. NASA extended = the mission,
taking advantage of the ion propulsion and other systems to undertake this
chancy but exciting encounter with the comet. More information can be found on
the Deep Space 1 home page at http://nmp.jpl.nasadot gov/ds1/
Deep Space 1 was launched in October 1998 as part of NASA's New = Millennium
Program, which is managed by JPL for NASA's Office of Space Science, Washington,
D.C. The California Institute of Technology manages JPL for NASA.=20
======================================================================
(6) NOVEMBER'S LEONID METEOR SHOWER COULD CAUSE COMMUNICATIONS HAVOC
>From Nature Science Update, 24 September 2001=20
http://www.nature.com/nsu/010927/010927-5.html
LEONIDS MAY SHORT SATELLITES
PHILIP BALL
This year's Leonid meteor shower will be so big it poses a threat to = the
thousands of satellites orbiting Earth. At least one satellite could be shorted
out when the Earth passes through the dusty trail of the comet Tempel-Tuttle,
astronomers predict.
Between 17 and 19 November there will be almost ten meteors per square kilometre
of sky - that's ten times more than in 1999, the most = spectacular of recent
showers. So say Peter Brown of the Los Alamos National = Laboratory and Bill
Cooke of NASA's Marshall Space Flight Center in the USA1.
The Leonids are Tempel-Tuttle's debris. The comet sweeps through the = inner
Solar System every 33 years. These particles, mostly smaller than a = grain of
sand, burn up brightly as they stream through the Earth's atmosphere at around
150,000 miles an hour.=20
"A direct impact of even a single grain of dust could be catastrophic = for a
satellite," explains Mark Bailey of the Armagh Observatory, Northern Ireland.
"The particle would vaporize when it struck, creating a = plasma," he says.
"This cloud of electrically charged gas could short-circuit the satellite's
delicate electronics".
On the trail
The comet's dust trail takes centuries to disperse. Meanwhile the Earth passes
through the dust on its yearly orbit around the Sun. Each return = of the comet
leaves a trail in a slightly different position, so our = planet can encounter
several streams in different stages of dissolution in close succession.=20
We enter the dust streams end-on so the meteors seem to issue from a = single
point in the sky, superimposed on the Leo constellation: hence their = name.
This year's Leonid shower will have two activity peaks.=20
At around 12.00 GMT on 18 November the Earth will pass through streams = left
behind in 1766 and 1799. About five hours later we will hit streams = from 1866,
1833 and three fainter ones from the seventeenth century.
It should be a spectacular show; but it is hard to predict how = spectacular. As
the comet trails get older, their exact location becomes more = difficult to
estimate. The first accurate Leonid activity prediction was made in = 1999: the
shower produced over 3,000 visible meteors per hour.
Brown and Cooke have estimated how the dust streams disperse over time, = for a
range of possible initial states. From observations of previous = Leonid
showers, they try to determine which of these initial states is the = best
guess. They calculate that the dust streams are broader and more = dispersed
than older 2001 forecasts predict, so the showers may be longer but = less
intense.
References
Brown, P. & Cooke, B. Model predictions for the 2001 Leonids and
implications for Earth-orbiting satellites. Monthly Notices of the Royal
Astronomical Society, 326, L19 - L22, (2001).
Copyright 2001, Nature News Service / Macmillan Magazines Ltd 2001
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