Hello Group, the Seagrave dome is back in service. There was a problem
with the bearing case on the base of the dome, which has since been
repaired.

Please consider helping out during a public night!

Clear Skies

Tracey

Isn't some of the wood beneath the slit degraded?
Was this a quick fix or are there more substantial repairs needed?

Thanks
Bob F.



--- In skyscrapers_rias@yahoogroups.com, "T Haley" <thaley1968@...>
wrote:
>
> Hello Group, the Seagrave dome is back in service. There was a
problem
> with the bearing case on the base of the dome, which has since been
> repaired.
>
> Please consider helping out during a public night!
>
> Clear Skies
>
> Tracey
>

Here is an updated article about the search for Planet X, the tenth
planet beyond the planet Pluto.

http://www.space.com/scienceastronomy/080618-planet-x.html


Other "planets" beyond Pluto that have actually been found.  Eris is
slightly larger than Pluto and this one in the link below is smaller
than Pluto:

http://www.space.com/scienceastronomy/quaoar_discovery_021007.html


...and more hypothetical "planets" may actually exist:

http://www.space.com/scienceastronomy/astronomy/outer_planets_991014.h
tml

http://www.space.com/spacenews/archive04/kuiperarch_120604.html


   Bob N.

Thanks Bob.

Have you ever attempted to image any of these outer solar system objects?


Jim

--- In skyscrapers_rias@yahoogroups.com, "starman361" <bob_napier@...>
wrote:
>
> Here is an updated article about the search for Planet X, the tenth
> planet beyond the planet Pluto.
>
> http://www.space.com/scienceastronomy/080618-planet-x.html
>
>
> Other "planets" beyond Pluto that have actually been found.  Eris is
> slightly larger than Pluto and this one in the link below is smaller
> than Pluto:
>
> http://www.space.com/scienceastronomy/quaoar_discovery_021007.html
>
>
> ...and more hypothetical "planets" may actually exist:
>
> http://www.space.com/scienceastronomy/astronomy/outer_planets_991014.h
> tml
>
> http://www.space.com/spacenews/archive04/kuiperarch_120604.html
>
>
>   Bob N.
>

Hello all

         While I was visiting Pete Peterson's observatory last week, he was
imaging (for astrometry) an asteroid 20 miles diameter at 150 million miles
distant from earth.  The math shows he is more than capable of following up on
any coordinates showing promise for "planet X' and other bodies.  I will forward
this to him as well.


Roger

[Non-text portions of this message have been removed]

The Camp SureFire event is scheduled for next Thursday, July 17th with
a starting time of around 9:00PM. We still need volunteers for this
event.

It will be held at the YMCA Camp Westwood that is located at 2093
Harkney Hill Road in Coventry RI. This is a prime spot and I can
guarantee we will have a dark sky with minimal light pollution.

We need volunteers for this event...


Also mark your calendar for another event on August 15th. We will have
a group of scouts visiting us at Seagrave.

Bob Forgiel

A big thanks to everyone that attended last night's event.
Lynne couldn't thank us enough and wanted to be sure you all knew how grateful
she was.

We'll save the malfunctioning automatic sprinkler story for a cloudy night.

Thanks everyone
Bob Forgiel


---- Bob Forgiel <bforgiel@...> wrote:
> The Camp SureFire event is scheduled for next Thursday, July 17th with
> a starting time of around 9:00PM. We still need volunteers for this
> event.
>
> It will be held at the YMCA Camp Westwood that is located at 2093
> Harkney Hill Road in Coventry RI. This is a prime spot and I can
> guarantee we will have a dark sky with minimal light pollution.
>
> We need volunteers for this event...
>
>
> Also mark your calendar for another event on August 15th. We will have
> a group of scouts visiting us at Seagrave.
>
> Bob Forgiel
>

Below is the news release from the IAU.  This dwarf planet,
named "Makemake" is currently the fourth largest and was discovered
by Michael Brown, of Cal Tech.  Michael Brown is also the discoverer
of ERIS (2003 UB313), "the tenth planet", and other large dwarf
planets.

Links for more information are at the end of the email.

   Bob Napier

*******************************************************************

International Astronomical Union
Paris, France

For more information, please contact:

Dr. Edward L.G. Bowell
IAU Division III President
Lowell Observatory, USA
Tel: +1-928-774-3358

Mike Brown
Professor of Planetary Astronomy
California Institute of Technology
Phone: +1-626-395-8423

Lars Lindberg Christensen
IAU Press Officer
ESA/Hubble, Garching, Germany
Phone: +49-89-32-00-63-06

Jul 19, 2008

News Release: IAU0806

Fourth dwarf planet named Makemake

The International Astronomical Union (IAU) has given the name
Makemake to the newest member of the family of dwarf planets -- the
object formerly known as 2005 FY9 -- after the Polynesian creator of
humanity and the god of fertility.

Members of the International Astronomical Union's Committee on Small
Body Nomenclature (CSBN) and the IAU Working Group for Planetary
System Nomenclature (WGPSN) have decided to name the newest member of
the plutoid family Makemake, and have classified it as the fourth
dwarf planet in our Solar System and the third plutoid.

Makemake (pronounced MAH-keh MAH-keh) is one of the largest objects
known in the outer Solar System and is just slightly smaller and
dimmer than Pluto, its fellow plutoid. The dwarf planet is reddish in
colour and astronomers believe the surface is covered by a layer of
frozen methane.

Like other plutoids, Makemake is located in a region beyond Neptune
that is populated with small Solar System bodies (often referred to
as the transneptunian region). The object was discovered in 2005 by a
team from the California Institute of Technology led by Mike Brown
and was previously known as 2005 FY9 (or unofficially "Easterbunny").
It has the IAU Minor Planet Center designation (136472). Once the
orbit of a small Solar System body or candidate dwarf planet is well
determined, its provisional designation (2005 FY9 in the case of
Makemake) is superseded by its permanent numerical designation
(136472) in the case of Makemake.

The discoverer of a Solar System object has the privilege of
suggesting a name to the IAU, which judges its suitability. Mike
Brown says: "We consider the naming of objects in the Solar System
very carefully. Makemake's surface is covered with large amounts of
almost pure methane ice, which is scientifically fascinating, but
really not easily relatable to terrestrial mythology. Suddenly, it
dawned on me: the island of Rapa Nui. Why hadn't I thought of this
before? I wasn't familiar with the mythology of the island
so I had to look it up, and I found Makemake, the chief god, the
creator of humanity, and the god of fertility. I am partial to
fertility gods. Eris, Makemake, and 2003 EL61 were all discovered as
my wife was 3-6 months pregnant with our daughter. I have the
distinct memory of feeling this fertile abundance pouring out of the
entire Universe. Makemake was part of that." WGPSN and CSBN accepted
the name Makemake during discussions conducted per email.

Makemake holds an important place in the Solar System because it,
along with Eris and 2003 EL61, was one of the objects whose discovery
prompted the IAU to reconsider the definition of a planet and to
create the new group of dwarf planets. Visually, it is the second
brightest transneptunian object, following after Pluto, and is bright
enough to be seen through a high-end amateur telescope (a peak
magnitude of roughly 16.5). Mike Brown explains:
"The orbit is not particularly strange, but the object itself is big.
Probably about 2/3 the size of Pluto."

The other three dwarf planets are Ceres, Pluto and Eris. However,
Ceres is not a member of the distinctive plutoid group because its
orbit is smaller than Neptune's (Ceres is located in the asteroid
belt between Mars and Jupiter).

The word Makemake is Polynesian in origin and is the name of the
creator of humanity and the god of fertility in the mythology of the
South Pacific island of Rapa Nui or the Easter Island. He was the
chief god of the Tangata manu bird-man cult and was worshiped in the
form of sea birds, which were his incarnation. His material symbol
was a man with a bird's head.

Notes

The IAU is the international astronomical organisation that brings
together almost 10,000 distinguished astronomers from all nations of
the world. Its mission is to promote and safeguard the science of
astronomy in all its aspects through international cooperation. The
IAU also serves as the internationally recognised authority for
assigning designations to celestial bodies and the surface features
on them. Founded in 1919, the IAU is the world's largest professional
body for astronomers.

Links

* Information about Pluto and the other dwarf planets
http://www.iau.org/public_press/themes/pluto/
* IAU website
http://www.iau.org/
* Scientific paper estimating the size of Makemake
http://arxiv.org/abs/astro-ph/0702538v1

[NOTE: An image supporting this release is available at
http://www.iau.org/static/archives/images/screen/iau0806a.jpg
(107KB) ]

BTW, guess who has an office just down the hall from Mike Brown at
CalTech, the discoverer of Makemake and other dwarf planets?

Some of you may remember Patrick Morrissey who was a very active
Skyscrapers' member back in the days when he was a student at Brown
University.
Now Dr. Patrick is a rocket scientist and astronomy instrument
designer and works on the Galex Mission - GALexy Evolution eXplorer,
NASA's ultral violet astronomy satellite.

You can read Patrick's bio and his early association with Skyscrapers
here:

http://www.galex.caltech.edu/about/pmorrissey.html

   Bob Napier


--- In skyscrapers_rias@yahoogroups.com, "starman361"
<bob_napier@...> wrote:
>
> Below is the news release from the IAU.  This dwarf planet,
> named "Makemake" is currently the fourth largest and was discovered
> by Michael Brown, of Cal Tech.  Michael Brown is also the
discoverer
> of ERIS (2003 UB313), "the tenth planet", and other large dwarf
> planets.
>
> Links for more information are at the end of the email.
>
>   Bob Napier
>
> *******************************************************************
>
> International Astronomical Union
> Paris, France
>
> For more information, please contact:
>
> Dr. Edward L.G. Bowell
> IAU Division III President
> Lowell Observatory, USA
> Tel: +1-928-774-3358
>
> Mike Brown
> Professor of Planetary Astronomy
> California Institute of Technology
> Phone: +1-626-395-8423
>
> Lars Lindberg Christensen
> IAU Press Officer
> ESA/Hubble, Garching, Germany
> Phone: +49-89-32-00-63-06
>
> Jul 19, 2008
>
> News Release: IAU0806
>
> Fourth dwarf planet named Makemake
>
> The International Astronomical Union (IAU) has given the name
> Makemake to the newest member of the family of dwarf planets -- the
> object formerly known as 2005 FY9 -- after the Polynesian creator
of
> humanity and the god of fertility.
>
> Members of the International Astronomical Union's Committee on
Small
> Body Nomenclature (CSBN) and the IAU Working Group for Planetary
> System Nomenclature (WGPSN) have decided to name the newest member
of
> the plutoid family Makemake, and have classified it as the fourth
> dwarf planet in our Solar System and the third plutoid.
>
> Makemake (pronounced MAH-keh MAH-keh) is one of the largest objects
> known in the outer Solar System and is just slightly smaller and
> dimmer than Pluto, its fellow plutoid. The dwarf planet is reddish
in
> colour and astronomers believe the surface is covered by a layer of
> frozen methane.
>
> Like other plutoids, Makemake is located in a region beyond Neptune
> that is populated with small Solar System bodies (often referred to
> as the transneptunian region). The object was discovered in 2005 by
a
> team from the California Institute of Technology led by Mike Brown
> and was previously known as 2005 FY9 (or
unofficially "Easterbunny").
> It has the IAU Minor Planet Center designation (136472). Once the
> orbit of a small Solar System body or candidate dwarf planet is
well
> determined, its provisional designation (2005 FY9 in the case of
> Makemake) is superseded by its permanent numerical designation
> (136472) in the case of Makemake.
>
> The discoverer of a Solar System object has the privilege of
> suggesting a name to the IAU, which judges its suitability. Mike
> Brown says: "We consider the naming of objects in the Solar System
> very carefully. Makemake's surface is covered with large amounts of
> almost pure methane ice, which is scientifically fascinating, but
> really not easily relatable to terrestrial mythology. Suddenly, it
> dawned on me: the island of Rapa Nui. Why hadn't I thought of this
> before? I wasn't familiar with the mythology of the island
> so I had to look it up, and I found Makemake, the chief god, the
> creator of humanity, and the god of fertility. I am partial to
> fertility gods. Eris, Makemake, and 2003 EL61 were all discovered
as
> my wife was 3-6 months pregnant with our daughter. I have the
> distinct memory of feeling this fertile abundance pouring out of
the
> entire Universe. Makemake was part of that." WGPSN and CSBN
accepted
> the name Makemake during discussions conducted per email.
>
> Makemake holds an important place in the Solar System because it,
> along with Eris and 2003 EL61, was one of the objects whose
discovery
> prompted the IAU to reconsider the definition of a planet and to
> create the new group of dwarf planets. Visually, it is the second
> brightest transneptunian object, following after Pluto, and is
bright
> enough to be seen through a high-end amateur telescope (a peak
> magnitude of roughly 16.5). Mike Brown explains:
> "The orbit is not particularly strange, but the object itself is
big.
> Probably about 2/3 the size of Pluto."
>
> The other three dwarf planets are Ceres, Pluto and Eris. However,
> Ceres is not a member of the distinctive plutoid group because its
> orbit is smaller than Neptune's (Ceres is located in the asteroid
> belt between Mars and Jupiter).
>
> The word Makemake is Polynesian in origin and is the name of the
> creator of humanity and the god of fertility in the mythology of
the
> South Pacific island of Rapa Nui or the Easter Island. He was the
> chief god of the Tangata manu bird-man cult and was worshiped in
the
> form of sea birds, which were his incarnation. His material symbol
> was a man with a bird's head.
>
> Notes
>
> The IAU is the international astronomical organisation that brings
> together almost 10,000 distinguished astronomers from all nations
of
> the world. Its mission is to promote and safeguard the science of
> astronomy in all its aspects through international cooperation. The
> IAU also serves as the internationally recognised authority for
> assigning designations to celestial bodies and the surface features
> on them. Founded in 1919, the IAU is the world's largest
professional
> body for astronomers.
>
> Links
>
> * Information about Pluto and the other dwarf planets
> http://www.iau.org/public_press/themes/pluto/
> * IAU website
> http://www.iau.org/
> * Scientific paper estimating the size of Makemake
> http://arxiv.org/abs/astro-ph/0702538v1
>
> [NOTE: An image supporting this release is available at
> http://www.iau.org/static/archives/images/screen/iau0806a.jpg
> (107KB) ]
>

--- In skyscrapers_rias@yahoogroups.com, "starman361" <bob_napier@...>
wrote:
>
> BTW, guess who has an office just down the hall from Mike Brown at
> CalTech, the discoverer of Makemake and other dwarf planets?
>
> Some of you may remember Patrick Morrissey who was a very active
> Skyscrapers' member back in the days when he was a student at Brown
> University.
> Now Dr. Patrick is a rocket scientist and astronomy instrument
> designer and works on the Galex Mission - GALexy Evolution eXplorer,
> NASA's ultral violet astronomy satellite.
>
> You can read Patrick's bio and his early association with Skyscrapers
> here:
>
> http://www.galex.caltech.edu/about/pmorrissey.html
>
>   Bob Napier
>
>

Good find Bob, thanks for the link.

GALEX observations are also the subject for many of the NASA Space
Place articles that we receive from JPL for our newsletter.

On the subject of "Plutoids" I wonder if anyone is interested in
tracking and imaging these objects?

It is 2.25 miles WNW of Seagrave, $100k for 18 acres on 3 lots:
http://www.riliving.com/PropSearch/lndformdetails.asp?MLSid=550049&indiv=1

What do planetary mission controllers eat and what does the Dawn
spacecraft "eat" to propel itself through space to these
protoplanets, Vesta and Ceres in the asteroid belt?  Read the article
below to find out.  It is a lengthy read, but interesting and written
with a bit of humor.

   Bob Napier

*****************************************************************


http://dawn.jpl.nasa.gov/mission/journal_7_27_08.asp

Dawn Journal
Dr. Marc Rayman
July 27, 2008

Dear Dawnminants,

Dawn continues its flight through the solar system with all systems
functioning well. It is vitally important that the spacecraft is
reliably staying on course and on schedule, gently and steadily
thrusting with the bluish glow of its ion propulsion system; yet that
doesn't lend itself to the sorts of spine-tingling, heart-pounding,
hair-raising, planet-shattering logs for which Dawn is famous (at
least
among immigrants from brown dwarf systems reading these reports in the
vicinities of active galactic nuclei). So let's turn out attention to
consider a particular aspect of flying a mission with ion propulsion.

We crave power!!

Perhaps that requires a bit more detailed consideration...

Engineers are developing a method to determine how much power the
solar
arrays can produce. It might seem odd
that with the spacecraft having been in interplanetary flight for 10
months, engineers don't already know the answer. (Other facts might
seem
odd as well, such as the phrase "nihil ad rem" being in this sentence.
This log will address only one oddity however.)

When the spacecraft was at Earth's distance from the Sun, shortly
after
launch, the solar arrays would have been able to supply more than 10
kilowatts, enough to operate about 10 average homes in the US (and
nearly as much as your correspondent's cat Regulus generates when Mr.
Vacuum Cleaner emerges from his closet). Dawn cannot use that much
electrical power, but as it pushes deeper into space, the weaker
illumination by the Sun will yield less power. The craft's two solar
array wings, each about 2.3 by 8.3 meters (more than 7 by 27 feet),
were
designed to be large enough to meet the needs of the power-hungry ion
propulsion system plus all other spacecraft systems even in orbit
about
dwarf planet Ceres. To thrust at nearly twice Mars' average distance
from the Sun, Dawn carries the most powerful solar arrays ever used on
an interplanetary mission.

The only way to measure the power of the arrays is for the spacecraft
actually to pull the power from them, and its ability to do that is
limited. When thrusting at full throttle and using all systems
normally,
Dawn consumes 3.2 kilowatts. Even now, traveling farther from the Sun
than Mars ever ventures, the solar arrays
can provide about 4 kilowatts. If the spacecraft activated all of its
nonessential components, it still could not draw this much power. That
leaves engineers without an accurate determination of the full
potential
of the arrays.

Of course, engineers thoroughly tested the electrical power system
before launch, including each of the 11,480 solar cells and all other
components, and from that they constructed a mathematical simulation
of
the arrays. But laboratory measurements do not perfectly reproduce
conditions in space, so the computational model has some uncertainty.
In-flight measurements are needed to improve their simulation of how
much power the solar arrays can furnish at different distances from
the Sun.

Who cares how much power is available? Well, first and foremost, our
readers do! After all, you've gotten this far (and even farther right
now) in this log, so you must have some reason for spending otherwise
good time reading about the solar arrays. The Dawn project appreciates
your interest, and we want to provide the information you apparently
seek, even though we have no idea why you suddenly are eager to
understand the solar array performance.

As it turns out though, there is another reason for establishing the
true capability of the solar arrays. As explained in many (but fewer
than 10,001) previous logs, Dawn's unique mission is possible only
through the persistent use of its ion propulsion system. Rather than
thrusting for minutes, as most spacecraft do, Dawn will thrust for
years
As power diminishes in the dim depths of
space, Dawn must throttle its ion thruster to lower power (and lower
thrust) levels.

Because the throttle level depends on how much power is available, to
formulate the details of the craft's trajectory and other plans for
the
mission, engineers require knowledge of how much power the arrays will
provide at any distance from the Sun. After all, it is misleading to
think of ion thrusting as an ion propulsion subsystem function;
rather,
it is a spacecraft system function, requiring most subsystems to
operate
together. Apart from the inevitable (and quite unpredictable) glitches
and anomalies on the spacecraft and appearances of cake in mission
control, and contrary to many people's preconceived notions, since
well
before launch the greatest technical uncertainty in the planning of
Dawn's flight has been what the solar array power will be. So far,
mission engineers have incorporated a reasonable, but conservative,
estimate into the solar array simulation, but to refine the plans,
they
need to verify or correct the numbers.

Although the arrays produce more power than can be measured now, they
would produce less power if they were not pointed directly at the Sun.
That could reduce their output low enough to allow the spacecraft to
draw as much power as the arrays could generate in that orientation,
providing the calibration measurement that is needed. (Engineers would
extrapolate to reveal how powerful the arrays would be when Sun-
pointed
at different distances.) As is usually the case in controlling
interplanetary spacecraft, the details make such a test much less
simple
than it might appear at first blush.

With the normal switching of heaters on and off throughout the
spacecraft, the total power consumption fluctuates, and that could add
"noise" to the data, making the results harder to interpret and less
accurate. If the spacecraft tried to draw more power than the solar
arrays could produce, the battery would temporarily make up the
difference but, depending upon the circumstances, protective software
onboard would intervene to turn some systems off and place the
spacecraft in safe mode. While that would
not threaten the health of the spacecraft, it would threaten the solar
array calibration. (By the way, the battery can store only enough
energy
to operate the spacecraft for about an hour. The solar arrays keep it
charged for its occasional use.)

The solar array calibration working group (a runner up in the highly
competitive Least Cool Dawn Team Name Contest) devised a method to
calibrate the solar arrays that accounted for all these and many other
considerations, including the solar panel thermal equilibration time
and
the dependence on temperature of the power vs. voltage curve, high
voltage down converter phase margin, the solar array voltage set
point,
power processor unit undervoltage trips, the voltage-temperature
control
loop for the battery on the low voltage bus, and spacecraft safety
even
in the event of an unrelated anomaly during the test.

While conceptually simple (rotate the solar arrays by a certain angle
and measure how much power the spacecraft can draw), the calibration
proved complex enough that a somewhat simplified test was deemed
appropriate. The objective was to verify how the spacecraft would
operate in the test conditions before committing to the full
calibration. The plan was to execute the test on July 21, and if
everything went perfectly, the final version would be attempted the
next
day. Last year, when the planning for this began, it was decided to
schedule a backup opportunity late in 2008 in case the first time did
not yield the desired data. (In addition, the calibration will be
repeated occasionally over the course of the mission to monitor
changes
in the solar array characteristics, ensuring the power predictions
remain accurate.)

Because electrical power is essential to the operation of all
subsystems, a test of this nature calls for all subsystem personnel to
scrutinize spacecraft telemetry for symptoms of unpredicted and
infelicitous behavior. All commands were contained in a single file
transmitted to the spacecraft, and immediate intervention would not be
physically possible, as radio signals revealing the condition of the
spacecraft would take nearly 18 minutes to reach Earth, and commands
sent in response would require the same time to travel back to the
spacecraft. Nevertheless, the team needed to be prepared to take
action
in the very unlikely case a problem developed, so two key measures
were
put in place: all stations in mission control were at the ready, and
pizza was provided to help fill the gaps in this early-evening test
while radio signals raced across the solar system.


The result: overall the test went well, although there was unexpected
spacecraft behavior and unexpected toppings on the pizza. For the
former, no response was required by the flight team, as the spacecraft
executed all the commands correctly and returned to its normal
configuration at the end. The test yielded only a partial set of
calibration data however, apparently because some of the
reconfigurations of the electrical power system and the ion propulsion
system for the purposes of the test led to a few responses that were
not
anticipated. The spacecraft transmitted a large volume of supporting
data, which will take longer to digest than the pizza, and when the
satiated engineers have finished, they will determine what
modifications
to make for a new test. A future log will describe the next test and
any
corresponding changes in the food delivered to mission control.

Turning their attention on July 22 to a different topic, the team
modified software in one of the many computers onboard. In January,
with neither permission nor warning, a
subatomic particle traveling through the solar system hit a sensitive
electronic component on the spacecraft, triggering a quick sequence of
events that culminated in the spacecraft entering its safe mode. Since
then, programmers have developed a way to prevent space radiation that
reaches that particular circuit from having the same effect. With the
updated software, now the only consequence would be a notice to
controllers that the device was hit, and the spacecraft would not need
to enter safe mode or interrupt its activities.

The solar array test and the software change were conducted during a
planned 2-day pause in thrusting. On schedule on July 23, Dawn resumed
propelling itself with xenon ions. Once again the special lights
adorning a wall in mission control were turned on, emitting a blue
glow
to remind everyone who visits or works there of the probe's patient
pursuit of intriguing and unexplored worlds in the asteroid belt.

As Dawn travels through space, Earth and the Sun grow more remote.
Although the journey will never bring it near the part of the solar
system it used to consider home, we will see in the next log that its
path to Vesta and then to Ceres is not as direct as some might expect.
As part of the explanation, the log also may reveal something about
this
mispelling.

Dawn is 324 million kilometers (202 million miles) from Earth, or more
than 885 times as far as the moon and 2.14 times as far as the Sun.
Radio signals, traveling at the universal limit of the speed of light,
take 36 minutes to make the round trip.
http://dawn.jpl.nasa.gov/mission/journal_7_27_08.asp

Dawn Journal
Dr. Marc Rayman
July 27, 2008

Dear Dawnminants,

Dawn continues its flight through the solar system with all systems
functioning well. It is vitally important that the spacecraft is
reliably staying on course and on schedule, gently and steadily
thrusting with the bluish glow of its ion propulsion system; yet that
doesn't lend itself to the sorts of spine-tingling, heart-pounding,
hair-raising, planet-shattering logs for which Dawn is famous (at
least
among immigrants from brown dwarf systems reading these reports in the
vicinities of active galactic nuclei). So let's turn out attention to
consider a particular aspect of flying a mission with ion propulsion.

We crave power!!

Perhaps that requires a bit more detailed consideration...

Engineers are developing a method to determine how much power the
solar
arrays can produce. It might seem odd
that with the spacecraft having been in interplanetary flight for 10
months, engineers don't already know the answer. (Other facts might
seem
odd as well, such as the phrase "nihil ad rem" being in this sentence.
This log will address only one oddity however.)

When the spacecraft was at Earth's distance from the Sun, shortly
after
launch, the solar arrays would have been able to supply more than 10
kilowatts, enough to operate about 10 average homes in the US (and
nearly as much as your correspondent's cat Regulus generates when Mr.
Vacuum Cleaner emerges from his closet). Dawn cannot use that much
electrical power, but as it pushes deeper into space, the weaker
illumination by the Sun will yield less power. The craft's two solar
array wings, each about 2.3 by 8.3 meters (more than 7 by 27 feet),
were
designed to be large enough to meet the needs of the power-hungry ion
propulsion system plus all other spacecraft systems even in orbit
about
dwarf planet Ceres. To thrust at nearly twice Mars' average distance
from the Sun, Dawn carries the most powerful solar arrays ever used on
an interplanetary mission.

The only way to measure the power of the arrays is for the spacecraft
actually to pull the power from them, and its ability to do that is
limited. When thrusting at full throttle and using all systems
normally,
Dawn consumes 3.2 kilowatts. Even now, traveling farther from the Sun
than Mars ever ventures, the solar arrays
can provide about 4 kilowatts. If the spacecraft activated all of its
nonessential components, it still could not draw this much power. That
leaves engineers without an accurate determination of the full
potential
of the arrays.

Of course, engineers thoroughly tested the electrical power system
before launch, including each of the 11,480 solar cells and all other
components, and from that they constructed a mathematical simulation
of
the arrays. But laboratory measurements do not perfectly reproduce
conditions in space, so the computational model has some uncertainty.
In-flight measurements are needed to improve their simulation of how
much power the solar arrays can furnish at different distances from
the Sun.

Who cares how much power is available? Well, first and foremost, our
readers do! After all, you've gotten this far (and even farther right
now) in this log, so you must have some reason for spending otherwise
good time reading about the solar arrays. The Dawn project appreciates
your interest, and we want to provide the information you apparently
seek, even though we have no idea why you suddenly are eager to
understand the solar array performance.

As it turns out though, there is another reason for establishing the
true capability of the solar arrays. As explained in many (but fewer
than 10,001) previous logs, Dawn's unique mission is possible only
through the persistent use of its ion propulsion system. Rather than
thrusting for minutes, as most spacecraft do, Dawn will thrust for
years
As power diminishes in the dim depths of
space, Dawn must throttle its ion thruster to lower power (and lower
thrust) levels.

Because the throttle level depends on how much power is available, to
formulate the details of the craft's trajectory and other plans for
the
mission, engineers require knowledge of how much power the arrays will
provide at any distance from the Sun. After all, it is misleading to
think of ion thrusting as an ion propulsion subsystem function;
rather,
it is a spacecraft system function, requiring most subsystems to
operate
together. Apart from the inevitable (and quite unpredictable) glitches
and anomalies on the spacecraft and appearances of cake in mission
control, and contrary to many people's preconceived notions, since
well
before launch the greatest technical uncertainty in the planning of
Dawn's flight has been what the solar array power will be. So far,
mission engineers have incorporated a reasonable, but conservative,
estimate into the solar array simulation, but to refine the plans,
they
need to verify or correct the numbers.

Although the arrays produce more power than can be measured now, they
would produce less power if they were not pointed directly at the Sun.
That could reduce their output low enough to allow the spacecraft to
draw as much power as the arrays could generate in that orientation,
providing the calibration measurement that is needed. (Engineers would
extrapolate to reveal how powerful the arrays would be when Sun-
pointed
at different distances.) As is usually the case in controlling
interplanetary spacecraft, the details make such a test much less
simple
than it might appear at first blush.

With the normal switching of heaters on and off throughout the
spacecraft, the total power consumption fluctuates, and that could add
"noise" to the data, making the results harder to interpret and less
accurate. If the spacecraft tried to draw more power than the solar
arrays could produce, the battery would temporarily make up the
difference but, depending upon the circumstances, protective software
onboard would intervene to turn some systems off and place the
spacecraft in safe mode. While that would
not threaten the health of the spacecraft, it would threaten the solar
array calibration. (By the way, the battery can store only enough
energy
to operate the spacecraft for about an hour. The solar arrays keep it
charged for its occasional use.)

The solar array calibration working group (a runner up in the highly
competitive Least Cool Dawn Team Name Contest) devised a method to
calibrate the solar arrays that accounted for all these and many other
considerations, including the solar panel thermal equilibration time
and
the dependence on temperature of the power vs. voltage curve, high
voltage down converter phase margin, the solar array voltage set
point,
power processor unit undervoltage trips, the voltage-temperature
control
loop for the battery on the low voltage bus, and spacecraft safety
even
in the event of an unrelated anomaly during the test.

While conceptually simple (rotate the solar arrays by a certain angle
and measure how much power the spacecraft can draw), the calibration
proved complex enough that a somewhat simplified test was deemed
appropriate. The objective was to verify how the spacecraft would
operate in the test conditions before committing to the full
calibration. The plan was to execute the test on July 21, and if
everything went perfectly, the final version would be attempted the
next
day. Last year, when the planning for this began, it was decided to
schedule a backup opportunity late in 2008 in case the first time did
not yield the desired data. (In addition, the calibration will be
repeated occasionally over the course of the mission to monitor
changes
in the solar array characteristics, ensuring the power predictions
remain accurate.)

Because electrical power is essential to the operation of all
subsystems, a test of this nature calls for all subsystem personnel to
scrutinize spacecraft telemetry for symptoms of unpredicted and
infelicitous behavior. All commands were contained in a single file
transmitted to the spacecraft, and immediate intervention would not be
physically possible, as radio signals revealing the condition of the
spacecraft would take nearly 18 minutes to reach Earth, and commands
sent in response would require the same time to travel back to the
spacecraft. Nevertheless, the team needed to be prepared to take
action
in the very unlikely case a problem developed, so two key measures
were
put in place: all stations in mission control were at the ready, and
pizza was provided to help fill the gaps in this early-evening test
while radio signals raced across the solar system.


The result: overall the test went well, although there was unexpected
spacecraft behavior and unexpected toppings on the pizza. For the
former, no response was required by the flight team, as the spacecraft
executed all the commands correctly and returned to its normal
configuration at the end. The test yielded only a partial set of
calibration data however, apparently because some of the
reconfigurations of the electrical power system and the ion propulsion
system for the purposes of the test led to a few responses that were
not
anticipated. The spacecraft transmitted a large volume of supporting
data, which will take longer to digest than the pizza, and when the
satiated engineers have finished, they will determine what
modifications
to make for a new test. A future log will describe the next test and
any
corresponding changes in the food delivered to mission control.

Turning their attention on July 22 to a different topic, the team
modified software in one of the many computers onboard. In January,
with neither permission nor warning, a
subatomic particle traveling through the solar system hit a sensitive
electronic component on the spacecraft, triggering a quick sequence of
events that culminated in the spacecraft entering its safe mode. Since
then, programmers have developed a way to prevent space radiation that
reaches that particular circuit from having the same effect. With the
updated software, now the only consequence would be a notice to
controllers that the device was hit, and the spacecraft would not need
to enter safe mode or interrupt its activities.

The solar array test and the software change were conducted during a
planned 2-day pause in thrusting. On schedule on July 23, Dawn resumed
propelling itself with xenon ions. Once again the special lights
adorning a wall in mission control were turned on, emitting a blue
glow
to remind everyone who visits or works there of the probe's patient
pursuit of intriguing and unexplored worlds in the asteroid belt.

As Dawn travels through space, Earth and the Sun grow more remote.
Although the journey will never bring it near the part of the solar
system it used to consider home, we will see in the next log that its
path to Vesta and then to Ceres is not as direct as some might expect.
As part of the explanation, the log also may reveal something about
this
mispelling.

Dawn is 324 million kilometers (202 million miles) from Earth, or more
than 885 times as far as the moon and 2.14 times as far as the Sun.
Radio signals, traveling at the universal limit of the speed of light,
take 36 minutes to make the round trip.

Our next event will be for the Cub Scouts and will be held at Seagrave
Observatory on Friday August 15th.

In place of our normal star party, we are now offering a program aimed
specifically for the cub scouts obtaining their Astronomy Belt Loop and
Academics Pin.

A presentation has been added that is based specifically on the scout
requirements.

Thanks to those whom donated binoculars, we have added an observing station that
will consist of a table setup with the donated binoculars. We will need a
volunteer from our membership to demonstrate how to use and focus binoculars to
the first group. This volunteer will then supervise as the scouts demonstrate
how to use binoculars to the next group arriving at that station.

The scouts are required to interview an amateur astronomer so we are encouraging
them to ask the scope operators a few question in the form of a mini group
interview. The volunteers should be ready for a few basic questions.

Before I get to the part where I ask of volunteers, , , If anyone else has an
old pair of binoculars to donate, it would be helpful.

Now,, If anyone wants to volunteer for our first scout program, please shoot me
an email or get in touch with me during this Friday's meeting.

Thanks

Bob Forgiel

--- In skyscrapers_rias@yahoogroups.com, <bforgiel@...> wrote:
>
> Our next event will be for the Cub Scouts and will be held at
Seagrave Observatory on Friday August 15th.
>
> In place of our normal star party, we are now offering a program
aimed specifically for the cub scouts obtaining their Astronomy Belt
Loop and Academics Pin.
>
> A presentation has been added that is based specifically on the
scout requirements.
>
> Thanks to those whom donated binoculars, we have added an observing
station that will consist of a table setup with the donated
binoculars. We will need a volunteer from our membership to
demonstrate how to use and focus binoculars to the first group. This
volunteer will then supervise as the scouts demonstrate how to use
binoculars to the next group arriving at that station.
>
> The scouts are required to interview an amateur astronomer so we are
encouraging them to ask the scope operators a few question in the form
of a mini group interview. The volunteers should be ready for a few
basic questions.
>
> Before I get to the part where I ask of volunteers, , , If anyone
else has an old pair of binoculars to donate, it would be helpful.
>
> Now,, If anyone wants to volunteer for our first scout program,
please shoot me an email or get in touch with me during this Friday's
meeting.
>
> Thanks
>
> Bob Forgiel
>

Bob I will be there, but I will come in my usual capacity of setting
up my own scope. I hope that we break out of this crazy weather
pattern by then.

The event we had scheduled for the cub scouts on August 15th has been
rescheduled for Saturday, September 6th. It will also be a public night but
between the lunar phase, time and school nights, we didn't have much of a
choice. Since it's also a public night and the 16" is down, we should try and
have a few members scopes setup.

Also, , , ASSNE has invited us to join them at the WaterFire in Providence this
Saturday, August 23rd. Glenn and myself will be attending and we also invite any
Skyscraper whom would like to join us.

ASSNE could still use a few more scopes or volunteers to help out. Obviously
ten's of  thousands of people attend the WaterFire. Contact Pete Peterson if you
can join us. If your not sure of Pete's email address you can  let Glenn or
myself know and we'll pass it along.

Hope to see you all at both events even if it's just for moral support.

Thanks
Bob Forgiel

ASSNE has invited us to help with the Providence  WaterFire this Saturday,
August 23rd.  We could still use additional scopes. Thus far Glenn and myself
are the only skyscrapers attending so if you can help out I'm sure it we be
greatly appreciated.

Pete has provided the following details:

ASSNE/SKYSCRAPER Waterfire Viewing of 23 Aug 08
HERE’S THE PLAN

Weather: It’s been clear so long I don’t remember what clouds look like. 
Forecast continues to be great!

Here’s the lineup

Committed scopes
George with his 8" SCT
Matt & Jeff Hill with the club 8" SCT
Bruce with his 10" SCT
Pete with his 12" SCT.
Skyscraper Bob Forgiel with his 8" SCT
Bob Sikes with his 8" SCT
Skyscraper president Glenn Jackson with his 8" SCT
Joe Almeida with his 10" SCT

Committed Volunteers for crowd pre-briefing and crowd control
Kevin Pilkington as a coordinator
skyscraper Steve Hubbard as coordinator  Sue is coming too.
Bob Zoglio as a coordinator
Spence Blakely as a coordinator

Timing: You should arrive at 5:45 as things get VERY BUSY as fire time
approaches.  We need 2 non-scope volunteers to be at the unloading point at 5:30
to provide security for the equipment.
Scope operators - please plan on arriving at 5:45 pm, but no later than 6:00 pm.
Once all the scopes are collected on the sidewalk and everybody has parked their
vehicles, we’ll carry the scopes in about 120’ toward the river to our
viewing area.  The non-scope staff guys will serve as security at both ends
while the scopes are being moved.  We’ll knock off sometime between 10:30 and
11:00pm depending upon weather, the crowd, visibility of objects and how tired
we are.  The fires will light off at sunset - 7:33, but we probably won’t be
able to start viewing Jupiter until 8.

Public Donations:  Usually ASSNE will split donations with Waterfire 50/50. 
However this year all donations received on Saturday will go to Waterfire. 
There will be a donation jar at the entrance to the viewing area.  The total
take typically runs $300 to $600.  Obviously the coordinators will need to keep
an eye on this jug.

Procedures:
We will be set up on the footbridge immediately north of the College Street
bridge and the bridge will be closed to all other activity.  The west end of the
bridge will be roped off.  Volunteers manning the table at the east end will be
controlling entrance to the scopes.

The coordinators manning the table will spell the scope operators, but their
primary function will be to educate the public regarding Jupiter & the Galilean
moons - explaining what features people should be looking for when they view
through a telescope.  I’ll make up hundreds of small info sheets for
distribution.

Security:
The bridge is roped off and closed to everyone but us and our guests.  We can
not allow strangers to be freely wandering around the viewing area.  When you
are ready to host, walk to the gate and pick up the next person or family group.
Walk them to your scope, and let them view.  Usually a minute will suffice for
them to spot whatever features you point out.  And they usually have a short
attention span, which is good.  Because the lines will get very long if we take
longer than a minute.  Once your guest or family group is done, escort them out
the gate and pick up the next in line.  It is very important that we have no
unescorted strangers on the bridge with us.  If you need to leave the bridge and
you have no one to run your scope, remove your eyepiece to effectively shut down
the scope.


Directions:

To get there from Rt 195 coming west couldn't be easier.  Just take Exit 2
(South Main Street).  We’re viewing on South Main Street.  This exit dumps you
directly onto South Main.  The College Street intersection where we’ll be
collecting the scopes is at the first red light you’ll encounter.  It’s
about 1/2 mile from the exit ramp, and my blue Ford Ranger pickup will be parked
on the left just before or after the traffic light.  As you approach you'll see
a park on your left  and the columns of the court house on your right.  Once you
reach the park, you’re close.  So if you see a space along the curb - grab it.

For those of you coming Rt 95 from the north, stay in the left hand lane once
you’re in the city and exit left onto Rt 195 East.  Ease to the right as soon
as you’re on 195 East and take Exit 2 (Wickenden  Street).  At the bottom of
the ramp is a light at the intersection with Wickenden Street. This is a curious
and confusing intersection.  You will turn left at the light, but there are 2
left hand roadways going under a bridge, one immediately after the other, side
by side and separated by a divider.  Take the second left hand roadway and stay
to the left.  This roadway only runs 200 feet before it takes a 90° turn to the
left and there’s a stoplight where you intersect Wickenden from the other
direction.  Turn left onto Wickenden, going back toward the direction you came
from, only get to the right and take the FIRST right.  This is South Main Street
– and we’re unloading just up the street.  Immediately after the South Main
Street turn is another turn with a big sign saying 195 West and leading back up
onto the highway.
After turning onto South Main (about ½ mile or so from the turn) you'll see a
park on your left, the columns of the court house on your right, and the first
traffic light you’ll encounter on South Main directly ahead.  If you see a
space along the curb once you reach the park, grab it.  My blue Ford Ranger
pickup (marking our gathering point) will be parked on the left just before or
after the first traffic light. The sidewalk next to my pickup is our scope
unloading point.

Unloading  Plan on dropping scopes off at my pickup truck and then parking your
car.  You can either double park for a minute or you can swing onto the blocked
off section of College Street.  By 5:30 pm there will be astronomy equipment in
the truck bed and someone guarding the equipment.

For late arrivals – we’ll be set up about 120 feet in from the South Main
Street and about 40 feet west of College Street.  South Main Street is one way
(running northwest) and College street is the first red light that you’ll
encounter.

Parking for Waterfire
If we gather in front of the red light instead of behind it, once you've
unloaded, you can drive up College Hill.  Go 500’ thru the first light on
Benefit Street.  About another 150' past the light you'll find a Brown U parking
lot (lot #52) on your right where you can park.  Brown is opening this lot for
us.  The driveway into the lot runs up a steep incline for about 30 feet and the
parking gates should have been left open for us.  PLEASE PUT A PIECE OF PAPER
WITH “WATERFIRE TELESCOPES” WRITTEN

This is a fun family event and we've already got a dozen volunteers.
But it's not to late to join us.  You don't need a scope to
participate.  Y'all come, hear?

Pete Peterson
401-245-4068
pete@...

We achieved a number of objectives on Saturday night.

The feedback from the public and from Waterfire left all participants
feeling great.  A number of family members attended and they appeared
to have had a wonderful time as well.

Bringing Skyscrapers and ASSNE together so we got to know each other a
bit and enjoy the company new fellow astronomers.  (We've done a couple
of minor things together before but this was a biggie

Making the look up and be aware.

And finally, recruiting new members.  I was running one of the 8 scopes
on the bridge, and met 6 people who are either astronomy hobbists or
wanted to get involved.  An unassuming gentleman named Hiro explained
that he was an unaffiliated stargazer living in Wickford and he owned a
small Japanese telescope.  Perhaps I recognized the brand.  Takahashi?

Photos and a writeup on the event may be found at
http://assne.org/board/viewtopic.php?t=1482

I have dual membership, and seeing how well Skyscrapers and ASSNE
integrated I'm hopefull that we'll see a lot more joint activity in the
future.

Pete Peterson

http://dawn.jpl.nasa.gov/mission/journal_8_24_08.asp

Dawn Journal
Dr. Marc Rayman
August 24, 2008

Dear Dawnivores,

The Dawn spacecraft continues to make good progress on its adventure t
unlock scientific secrets hidden deep in the main asteroid belt,
between Mars and Jupiter. Its path to that distant realm of the solar
system is now bringing it closer to the Sun, and thanks in part to
all the thrusting it has accomplished with its remarkable ion
propulsion system, it has recently achieved its lowest speed so far
in the mission. To understand this enigmatic behavior, read on!

As most of you who have read about or visited the solar system know,
the asteroid belt is much farther from the Sun than Earth is. Dawn
passed outside the orbit of Mars in June, but it
has not yet traveled far enough from the Sun to reach asteroid Vesta,
its first destination. Dwarf planet Ceres, Dawn's second target,
resides still farther in the depths of space. So readers with
memories that extend as far back as the previous paragraph may wonder
why Dawn apparently is backtracking, now approaching the Sun.

Despite the many innovations that make this project so fascinating,
the Dawn team has not yet discovered how to travel backwards in time.
(If it had, while writing this log, we would be able now to prevent
the misspelling that occurred while
writing the last log.) To see why Dawn seems to be reversing course,
both heading toward the Sun and traveling more slowly now than at the
beginning of its mission, we need to consider some of the principles
that govern space travel.

Your correspondent offered some comments on these concepts in a log
for a different interplanetary mission, Deep Space 1. If not
for some unexpected legal issues with certain species in spiral
galaxies capable of abstract thought, we would simply reprint that
material here. Instead, we shall consider some of the same ideas but
with different words.

The goal of this text is to provide only a gist of some of the
fundamentals. In an act of selfless charity to help our hungry friends
the Numerivores of Q2237+0305, this log will include more numbers
than usual. It is not necessary to study them in detail; some readers
may find them helpful and others may feel free to gloss over them. In
any case, we can provide an absolute guarantee that by the end, with
even a casual comprehension of this material, the interested reader
would not find even the doctorate level examinations from the
prestigious Galactic Institute of Space Travel (known to many
as "the prestigious Galactic Institute of Space Travel") to be
difficult.

The overwhelming majority of craft humans have sent into space have
remained in the vicinity of Earth, accompanying that planet on its
annual revolutions around the Sun. The satellites of Earth (including
the moon) remain bound to it by its gravity. As fast as they seem to
travel compared to residents of the planet, from a solar system
perspective, their incessant circling of Earth means their paths
through space are not very different from Earth's itself. Everything
on the surface and in Earth orbit travels around the Sun at an
average of around 30 kilometers/second (67,000 miles/hour),
completing one full solar orbit every year. To undertake its
interplanetary exploration and travel elsewhere in the solar system,
Dawn needed to break free of Earth's grasp, and that was accomplished
by the rocket that carried it to space last year. Dawn and its
erstwhile home went their separate ways, and the Sun became the
natural reference for the spacecraft's position and speed on its
travels in deep space.

Despite the enormous push the Delta II rocket delivered (with
affection!) to Dawn, the spacecraft still did not have nearly enough
energy to escape from the powerful Sun. So, being a responsible
resident of the solar system, Dawn remains faithfully in orbit around
the Sun, just as do Earth and the rest of the planets, asteroids,
comets, and other members of the Sun's entourage.

Whether it is for a spacecraft or moon orbiting a planet, a planet or
Dawn orbiting the Sun, the Sun orbiting the Milky Way galaxy, or the
Milky Way galaxy orbiting the Virgo supercluster of galaxies (home to
a sizeable fraction of our readership), any orbit is the perfect
balance between the inward tug of gravity and the inexorable tendency
of objects to travel in a straight path. If you attach a weight to
string and swing it around in a circle, the force you use to pull on
the string mimics the gravitational force the Sun exerts on the
bodies that orbit it.
The effort you expend in keeping the weight circling serves
constantly to
redirect its path; if you let go of the string, the weight's natural
motion would carry it away in a straight line (ignoring the effect of
Earth's gravity).

The force of gravity diminishes with distance, so the Sun's pull on a
nearby body is greater than on a more distant one. Therefore, to
remain in orbit, to balance the relentless tug of gravity, the closer
object must travel faster, fighting the stronger pull. The same
effect applies at Earth. Satellites that orbit very close (including,
for example, the International Space Station, less than 400
kilometers from the surface)
must streak around the planet at about 7.7 kilometers/second (more
than 17,000 miles/hour) to keep from being pulled down. The moon,
orbiting 1000 times farther above, needs only to travel at about 1.0
kilometers/second (less than 2300 miles/hour) to balance Earth's
weaker grip at that distance.

Notice that this means that for an astronaut to travel from the
surface of Earth to the International Space Station, it would be
necessary to accelerate to quite a high speed to rendezvous with the
orbital facility. But then once in orbit, to journey to the much more
remote moon, the astronaut's speed eventually would have to decline
dramatically. Perhaps speed tells an incomplete story in describing
the travels of a spacecraft, just as it does with another example of
countering gravity.

A person throwing a ball is not that different from a rocket
launching a satellite (although the former is usually somewhat less
expensive and often involves fewer toxic chemicals). Both represent
struggles against Earth's gravitational pull. To throw a ball higher,
you have to give it a harder push, imparting more energy to make it
climb away from Earth,
but as soon as it leaves your hand, it begins slowing. For a harder
(faster) throw, it will take longer for Earth's gravity to stop the
ball and bring it back, so it will travel higher. But from the moment
it leaves your hand until it reaches the top of its arc, its speed
constantly dwindles as it gradually yields to Earth's tug. The
astronaut's trip from the space station to the moon would be
accomplished by starting with a high speed "throw" from the low
starting orbit, and then slowing down until reaching the moon.

The rocket that launched Dawn threw it hard enough to escape from
Earth, sending it well beyond the International Space Station and the
moon.
Indeed, the spacecraft is now more than 1 million times farther away
than the station. Dawn's maximum speed relative to Earth on launch day
was so high that Earth could not pull it back. As mentioned in an
earlier log, Dawn was propelled to 11.46
kilometers per second (25,600 miles per hour), well in excess of the
space station's orbital speed given 3 paragraphs above. But it remains
under the Sun's control.

If the spacecraft had never operated its ion propulsion system, it
would have coasted away from the Sun (even while Earth continued
circling the Sun on its own), slowing down the entire time, reaching
the top of its interplanetary arc on July 2, 2008. Then, at almost
242 million kilometers (150 million miles) from the Sun, as it
succumbed to the massive star's pull, it would have begun its inward
fall.

Many solar system residents find measuring distances in millions of
kilometers (or miles) to be inconvenient, so it is common to use the
"astronomical unit" (AU). The average
distance between Earth and the Sun, nearly 150 million kilometers (93
million miles) is defined to be 1 AU. So Dawn would have reached
almost 1.62 AU from the Sun without thrusting.

After that, the probe would not have fallen all the way back to the
Sun, ending in a useless blaze. Because it departed from Earth, which
was already orbiting the Sun, and not from a stationary platform, it
began with energy adequate to keep it at Earth's orbit. Upon allowing
the Sun to pull it back, it would come only to about that same orbit,
reaching a minimum distance of 1.00 AU from the Sun on April 1, 2009.
So Dawn would have been in an elliptical solar orbit, ranging from
1.00 AU to 1.62 AU.
It would have traveled faster and faster as it swooped to its smallest
distance and then slowed down again as it sailed back out to the
largest distance, much like a person on a swing, slowing near the
top, speeding through the lowest point, and then repeating that
pattern. The change in speed with distance is an essential
characteristic of all orbits.

Now think again of the ball you throw. If it had a tiny propulsion
system to help it along its way, that extra boost would propel it
higher, supplementing the energy you imparted to it when it left your
hand. Unlike a powerful rocket that accelerates as it ascends, if the
additional thrust were low, it might not be able to completely counter
the slowing from Earth's gravity, but it might help reach a higher
altitude before beginning its fall.

As Dawn's famously efficient ion propulsion system has given it a
delicate but steady push on its flight away from the Sun, the
spacecraft has been able to resist the Sun's incessant pull longer.
Instead of turning back in early July, Dawn flew outward until August
8. Even with all the thrusting, it was constantly slowing down, and
when the Sun's gravity overwhelmed it, it began its inward flight.
But by then the ion thrusting had changed the shape of its elliptical
orbit so it would not fall back as far as Earth's orbital distance.
If it undertook no more thrusting after August 8, it would come back
only to 1.16 AU from the Sun, reaching that distance on June 14,
2009. As we will see in future logs, it will not have the opportunity
to drop even that close to the Sun however, because ion propulsion
continues modifying its orbit. In addition, on approximately February
18, 2009 (the exact date and time depend on the progress of future
thrusting), the probe will pass by Mars, and the gravitational
deflection will cause still more changes to its orbit around the Sun,
which eventually will take it to the asteroid belt.

On September 27, 2007, some 2 minutes after it had separated from its
rocket, Dawn reached its highest speed relative to the Sun for the
entire mission. At that time, it was traveling at about 38.95
kilometers/second (87,130 miles/hour). Earth (and its residents,
including this writer) were moving around the Sun at the more
leisurely pace of 29.70 kilometers/second (66,440 miles/hour).

So what has been the effect of Dawn's thrusting since then? By August
8 it had expended about 55.4 kilograms (122 pounds) of xenon
propellant, some for tests during the initial checkout phase of the
mission and most with the specific intent of altering its orbit
around the Sun. If this were solely for the purpose of accelerating
(as it is usually described, in these logs and elsewhere) without the
complex patterns involved in orbital dances, the effect would have
been to increase Dawn's speed by 1.38 kilometers/second (3090
miles/hour). But because of the way forces and velocities work in
space travel, in pushing Dawn away from the Sun,
allowing it to travel "higher" before the Sun pulled it back, the ion
propulsion system helped Dawn continue away from the Sun until, on
August 8, it was more than 1.68 AU from the omphalos of the solar
system. By then, its speed had fallen to 20.77 kilometers/second
(46,460 miles/hour). At the same moment Dawn was orbiting the Sun at
that rate, distant Earth was racing in its orbit at 29.38
kilometers/second (65,710 miles/hour).

When Dawn began coming back in toward the Sun, it was in a different
part of the solar system from where it would have been had it never
applied its ion propulsion system to so patiently yet persistently
change the orbit the Delta rocket left it in. In the absence of any
ion thrusting, the spacecraft would have been 0.45 AU (68 million
kilometers or 42 million miles) away from its actual location on
August 8.

Dawn will rendezvous with Vesta in about 3 years. To match that
asteroid's orbit around the Sun, our robotic explorer will have to
continue tuning its orbital parameters so that it will be almost 2.3
AU from the Sun while traveling at about 20 kilometers/second (45,000
miles/hour), farther and slower than its current orbit or that of its
quondam planetary domicile.

Achieving the required speed and distance alone is not enough to
ensure Dawn can slip into orbit around Vesta, but we will consider
other aspects of this problem in a future log. In the meantime, we
can think of the general problem of flying elsewhere in space as
similar to climbing a hill. For terrestrial hikers, the rewards of
ascent come only after doing the work of pushing against Earth's
gravity to reach a higher elevation. Similarly, Dawn is climbing a
solar system hill with the Sun at the bottom. It started from Earth,
at 1 AU in elevation; and its first rewards await it higher up that
hill at 2.3 AU, where Vesta, traveling at only about two thirds of
Earth's speed, keeps its records of the dawn of the solar system.
Ceres is still higher up the hill, moving even more slowly to balance
the still weaker pull of the Sun.

If this were only a climb, it would be easy to stop at the correct
spot on the solar system hill. This simple analogy fails us here
though, because everything is in orbital motion. With a big enough
rocket, or gravitational boosts, it would not be hard to throw Dawn
hard enough that it would fly out to Vesta or beyond, and some other
spacecraft have coasted past that distance from the Sun. But to enter
orbit, Dawn must precisely match Vesta's path around the Sun, joining
it for a portion of the asteroid's regular 3.6-year circuit around
the Sun, just as Earth's natural and human-made satellites stay with
it throughout its 1-year orbit. That is part of the reason the
spacecraft needs ion propulsion.
The ion propulsion system allows Dawn not only to carry its scientific
instruments up that hill but also to "stop" on the slope, neither
falling back toward the Sun nor coasting by the asteroid. When a
subsequent log addresses what more is required than speed and
distance,
we will see why this is more difficult than it may appear. (And as we
surely will have a link from that log to this one, on behalf of all
present readers, we send greetings from the past to you future
readers.)
We are confident that in meeting this great challenge, should Dawn
remain healthy, it will be a shoo-in in the next solar system
Olympics, aiming not for a bronze medal, nor for one of silver or
gold but rather for the most highly coveted: the xenon medal.

We promised near the beginning that for those who completed this
arduous log (perhaps a challenge even greater than Dawn's
interplanetary journey), the examinations at the prestigious Galactic
Institute of Space Travel would not prove difficult. The reason is
simple: there is no such organization; we made it up. Nevertheless,
following Dawn's long and ambitious journey does not require mastery
of the concepts touched upon here. All that really is needed is the
desire to learn more about the cosmos, to share in one of humankind's
bold adventures to explore the unknown as we set our sights on
extraordinarily distant goals and aspire to something well beyond the
confines of our humble home in the universe.

Dawn is 352 million kilometers (219 million miles) from Earth, or 955
times as far as the moon and 2.33 times as far as the Sun. Radio
signals, traveling at the universal limit of the speed of light, take
39 minutes to make the round trip.

I was shocked to hear this on the news this morning.  As someone who
hails from the town of Burrillville with aspirations of one day
returning there, this is scary news:

http://www.telegram.com/article/20080904/NEWS/809040699/1116

As we all know, the maximum speed of light in a vacuum is about 186,000
miles per second.

If light slows down when say going through air or glass (or any
transparent subtance), it is supposed to then speed up again when it
gets out of that subtance.
     For example.  Light goes through the atmosphere and then goes out
into the vaccum of space, it then picks up to its normal cruising speed
of 186,000 m/p/s.  At least from what I understand.
     The question is, if that is so, where is the energy coming from to
re-accelerate it back up to its normal cruising speed?  That seems to
go against the Law of Concervation of Energy.

   Bob N.

Hello, Bob.

Find a copy of Richard Feynman's "QED".  All will be revealed...

Tony


starman361 wrote:
>
> As we all know, the maximum speed of light in a vacuum is about 186,000
> miles per second.
>
> If light slows down when say going through air or glass (or any
> transparent subtance), it is supposed to then speed up again when it
> gets out of that subtance.
> For example. Light goes through the atmosphere and then goes out
> into the vaccum of space, it then picks up to its normal cruising speed
> of 186,000 m/p/s. At least from what I understand.
> The question is, if that is so, where is the energy coming from to
> re-accelerate it back up to its normal cruising speed? That seems to
> go against the Law of Concervation of Energy.
>
> Bob N.
>
>

Checking the listings this week, this particular property is still
available, and at the reduced asking price of 89900.  Seems too good a
good deal.  Anyone interested?

http://www.riliving.com/PropSearch/lndformdetails.asp?MLSid=550049&indiv=1

Recent observations posted on the MPML Yahoo discussion group
indicate the impact probability is at least 99% and will occur
somewhere over northern Africa or southern Europe.  The possible
impact time is estimated to be about 10:46 EST Oct. 6.

The note below was posted on the ATMoB discussion group.

   Bob N.

*****************************************************************

Rock From Space To Burn Up Over Africa
This is an AstroAlert from Sky & Telescope.
October 6, 2008

----------------------------------------------------------------------
----------

A very tiny asteroid, not much more than 10 feet across, will enter
Earth's atmosphere over Sudan in Africa tonight, October 6-7, 2008,
near 2:46 Greenwich Mean Time. Most likely it will burn up before
hitting the ground, but it could produce a spectacular fireball, or
bolide, in the night sky equivalent to the explosion of about a
kiloton of TNT.
These are the assessments of astronomers Andrea Milani of NEODyS in
Italy and Steve Chesley (Jet Propulsion Laboratory). They are
concerned that eyewitnesses might misinterpret the event as some type
of hostile military action. Says Milani, "The earlier the public
worldwide is aware that this is a natural phenomenon, which involves
no risk, the better."

The first observatory to capture images of 2008 TC3 (as it's now
designated) were Richard Kowalski and colleagues of Mount Lemmon
Observatory in Arizona, about 12 hours ago. Confirming measurements
were quickly secured by amateur astronomer James McGaha at Sabino
Canyon Observatory near Tucson, and then by Gordon Garrad and others
at Australia's Siding Spring Observatory and also Christopher Jacques
and E. Pimentel using the Global Rent-a-Scope site in Moorook, near
Melbourne.

First to point out that the incoming object was heading right for a
collision with Earth's atmosphere was Bill Gray of Project Pluto, in
a post earlier today to the Minor Planet Mailing List. Canadian
amateur Andrew Lowe has independently calculated the object's point
of entry to be over Sudan.

The object's entry might be visible as far north as southern Europe
and the Middle East. Its location in the sky, however, is completely
dependent on an observer's geographic location. As further details
become known, be sure to look at the online version of this
AstroAlert at SkyandTelescope.com/AstroAlert for possible updates.


Roger W. Sinnott
Senior Editor
Sky & Telescope
rsinnott@...

More info from a NASA news release:

   Bob N.

********************************************

http://neo.jpl.nasa.gov/news/news159.html

Small Asteroid Predicted to Cause Brilliant Fireball over Northern
Sudan
Don Yeomans
NASA/JPL Near-Earth Object Program Office
October 6, 2008

A very small, few-meter sized asteroid, designated 2008 TC3, was found
Monday morning by the Catalina Sky Survey from their observatory near
Tucson Arizona. Preliminary orbital computations by the Minor Planet
Center suggested an atmospheric entry of this object within a day of
discovery. JPL confirmed that an atmospheric impact will very likely
occur during early morning twilight over northern Sudan, north-eastern
Africa, at 2:46 UT Tuesday morning. The fireball, which could be
brilliant, will travel west to east (from azimuth = 281 degrees) at a
relative atmospheric impact velocity of 12.8 km/s and arrive at a very
low angle (19 degrees) to the local horizon. It is very unlikely that
any sizable fragments will survive passage through the Earth's
atmosphere.

Objects of this size would be expected to enter the Earth's atmosphere
every few months on average but this is the first time such an event
has been predicted ahead of time.

**********************************************************

--- In skyscrapers_rias@yahoogroups.com, "starman361"
<bob_napier@...> wrote:
>
> Recent observations posted on the MPML Yahoo discussion group
> indicate the impact probability is at least 99% and will occur
> somewhere over northern Africa or southern Europe.  The possible
> impact time is estimated to be about 10:46 EST Oct. 6.
>
> The note below was posted on the ATMoB discussion group.
>
>   Bob N.
>
> *****************************************************************
>
> Rock From Space To Burn Up Over Africa
> This is an AstroAlert from Sky & Telescope.
> October 6, 2008
>
> --------------------------------------------------------------------
--
> ----------
>
> A very tiny asteroid, not much more than 10 feet across, will enter
> Earth's atmosphere over Sudan in Africa tonight, October 6-7, 2008,
> near 2:46 Greenwich Mean Time. Most likely it will burn up before
> hitting the ground, but it could produce a spectacular fireball, or
> bolide, in the night sky equivalent to the explosion of about a
> kiloton of TNT.
> These are the assessments of astronomers Andrea Milani of NEODyS in
> Italy and Steve Chesley (Jet Propulsion Laboratory). They are
> concerned that eyewitnesses might misinterpret the event as some
type
> of hostile military action. Says Milani, "The earlier the public
> worldwide is aware that this is a natural phenomenon, which
involves
> no risk, the better."
>
> The first observatory to capture images of 2008 TC3 (as it's now
> designated) were Richard Kowalski and colleagues of Mount Lemmon
> Observatory in Arizona, about 12 hours ago. Confirming measurements
> were quickly secured by amateur astronomer James McGaha at Sabino
> Canyon Observatory near Tucson, and then by Gordon Garrad and
others
> at Australia's Siding Spring Observatory and also Christopher
Jacques
> and E. Pimentel using the Global Rent-a-Scope site in Moorook, near
> Melbourne.
>
> First to point out that the incoming object was heading right for a
> collision with Earth's atmosphere was Bill Gray of Project Pluto,
in
> a post earlier today to the Minor Planet Mailing List. Canadian
> amateur Andrew Lowe has independently calculated the object's point
> of entry to be over Sudan.
>
> The object's entry might be visible as far north as southern Europe
> and the Middle East. Its location in the sky, however, is
completely
> dependent on an observer's geographic location. As further details
> become known, be sure to look at the online version of this
> AstroAlert at SkyandTelescope.com/AstroAlert for possible updates.
>
>
> Roger W. Sinnott
> Senior Editor
> Sky & Telescope
> rsinnott@...
>

http://www.motorrepair.us/highres/index.html

http://news.bbc.co.uk/2/hi/health/7656528.stm

Friday, October 17th > Woman's Wilderness Weekend @ Alton Jones Campus

We have  had only one other Skyscraper that volunteered for the Woman's
Wilderness Weekend at Alton Jones.  Dave and myself cannot handle a group this
size by ourselves so we had no choice but to regrettably DECLINE from the
invitation. This event has been CANCELED.

Bob F.

---- bforgiel@... wrote:

There is still a spark of life in this event. If we can come up with a few more
scopes by mid day Thursday we might be able to pull this off. If you think you
can attend, send me an email with a # you can be reached at.

Bob Forgiel


---- bforgiel@... wrote:
> Friday, October 17th > Woman's Wilderness Weekend @ Alton Jones Campus
>
> We have  had only one other Skyscraper that volunteered for the Woman's
Wilderness Weekend at Alton Jones.  Dave and myself cannot handle a group this
size by ourselves so we had no choice but to regrettably DECLINE from the
invitation. This event has been CANCELED.
>
> Bob F.
>
> ---- bforgiel@... wrote:

This international event encourages everyone to go outside, look
skywards after dark, count the stars they see in certain
constellations, and report what they see online.  This Windows to the
Universe Citizen Science Event is designed to encourage learning in
astronomy!

http://www.windows.ucar.edu/citizen_science/starcount/

Below is a description of the event as posted on the ATMoB web site:

"Don't miss out on the worldwide star count October 20 - November
3rd, 2008.  For those who have not participated before, you don't
need a telescope - just go out and look up.   The number of stars
visible depends on the quality of the night sky.  You'll learn how to
measure the limiting magnitude of the night sky at your location,
report the data, and help contribute to a database measuring global
light pollution.  This is a useful project for teaching kids and
adults about the impact of artificial lighting on our environment.
Help raise awareness about the decreasing quality of our night skies
and the ongoing loss of our ability to study or simply enjoy the
night sky.   Investigate the economic and environmental impacts of
light in your town!"

   Bob N.