in his epic saga the inferno the italian
poet dante tells of ulysses the greek
hero who fought in the trojan war and
spent 20 adventurous years wandering the
earth before returning home
but as dante relates it ulysses bored
with domestic life set off on still
another voyage of discovery
a voids taught an uninhabited world
beyond the sun
in october of 1990 another ulysses will
begin an unprecedented voyage of
exploration
this modern ulysses is a spacecraft
bound for a region of our solar system
never before explored
the region above the sun's poles
stars
uncounted billions grace our night skies
but only one holds dominion over the
earth
it is the star we call the sun
the giver of light
of warmth
of life itself
the ancients called it the perfect fire
the sun is the only star we can see in
the daytime and the only one close
enough to study in detail
it therefore provides scientists a
unique window for the study of stars
and the complex processes that go on
within and around them
in recent decades astronomers aided by
increasingly sophisticated instruments
some earth-based some lofted into space
above earth's obscuring atmosphere
have found our sun to be an exceedingly
complex star with many faces
but scientists have never been able to
observe a most important region of the
sun its poles
even instruments on spacecraft are
unable to see over the top of this great
sphere
that's because until now we could study
the sun only from within the ecliptic
plane
an imaginary nearly flat plane in which
the earth and the other planets orbit
the sun
yet scientists think our understanding
of the sun would be vastly increased if
we could observe it from above its poles
that is the goal of ulysses a joint
mission between nasa and the european
space agency eason
willis meeks is american ulysses project
manager
ulysses is a one of a kind mission in
that it's the first time that we have a
chance to fly spacecraft over the sun's
poles to give us a look at the solar
system from that direction
we're also going to look at the total
sun's environment
we're studying something called a
heliosphere which is made up of all the
things influenced by our sun
it's a joint mission with nasa and the
european space agency the europeans
provide a spacecraft
we provide a launch vehicle and a launch
facility
the science investigations are split
right down the middle the instruments
there are nine of them hardware
instruments we provide half and the
europeans provide the other half
the mission will be flown from right
here at jpl
launch is scheduled for october 1990.
the american space shuttle discovery
will first carry ulysses into orbit
around the earth
there ulysses will be released from the
shuttle's cargo bay
after the shuttle has withdrawn to a
safe distance
two powerful rocket motors will fire and
send ulysses on its way
it will take nearly four years to get to
the sun
this long journey is made necessary by
the earth's own orbital motion around
the sun
dr edgar page european science
coordinator explains
well getting out of the ecliptic plane
is not very easy it requires a lot of
launch vehicle energy
and i suppose that's one of the reasons
we haven't done the mission before now
now what's the reason for this well most
normal launches
take advantage of the orbital velocity
of the earth they go along in the same
direction
but this time of course we can't do that
we have to get ourselves perpendicular
to the velocity of the earth we want out
of the ecliptic plane
now the energy available from even a
nasa shuttle launch is not sufficient to
do that so we have to ask for some help
and we get that from the giant planet
jupiter
we start from earth we go fast towards
jupiter
and then as we get close to jupiter
jupiter reaches out its gravity hand and
grabs us and pulls us around from its
north pole to its south pole and sends
us off
south of the ecliptic plain back towards
the sun
throughout the mission
nasa's deep space network will track
ulysses receiving data from previously
unexplored regions of our solar system
for analysis by earth-bound astronomers
scientists are sure to reap a rich
scientific harvest as ulysses and its
nine instruments explore previously
unreachable regions of the sun's domain
basically we're interested in uh
making observations over the poles of
the sun something which has never been
done before
we have a lot of reasons for
wanting to do that
and many reasons for thinking that
conditions
in that
particular region of space are going to
be very different than the kinds of
conditions we've been sampling over the
last 20 or 30 years
we have been making measurements
in a flat two-dimensional plane
when the object we're really trying to
understand is basically
three-dimensional
and the object of this mission now is to
extend our knowledge into that third
dimension
once we have that knowledge we'll be in
a better position to reevaluate the
complicated conditions that we find near
the solar equator
its mission will carry ulysses over both
of the sun's poles to probe the sun's
corona the diaphanous crown that we see
only during an eclipse
the solar wind a gale of charged
particles that stream away from the sun
and the tangled magnetic field which is
carried into space by the solar wind
finally some of ulysses instruments will
detect and measure cosmic rays coming
from the deeper reaches of our milky way
galaxy
the sun as we've come to know is far
from being the perfect fire the ancients
believed it to be
it is instead a seething thermonuclear
cauldron
vast quantities of energy burst from the
interior to create unimaginable turmoil
at the surface
and as the energy pours outward across
space it carries ever-shifting electric
and magnetic fields throughout the solar
system
what complicates matters even more is
that the sun rotates every 27 days
and material at the equator rotates
faster than material at the bones
as a result
the sun's magnetic and electrical fields
at the equator become tangled and
hopelessly complex
still more complexities arise in the
constantly shifting corona
even before spacecraft scientists
theorized that there was a strong
relation between the corona and the
solar wind
this relation became clear after
spacecraft made it possible to observe
the sun from above the earth's
atmosphere
that's when scientists discovered huge
tears in the corona
these coronal holes here seen as dark
patches are the source of the solar wind
low and high energy particles burst
outward from these vast regions at
speeds of up to a thousand kilometers
per second
solar wind particles move at many
different speeds and so the fast
particles bunch up behind the slower
ones and overtake them
the result is a traffic jam that snarls
the magnetic field lines around the
sun's equator into a tangle that twists
and knots and becomes ever harder to
understand
ulysses scientists will also study
particles that originate during solar
flares
solar flares are the most catastrophic
and energetic events on the sun
the particles they yield have extremely
high energies
these high energy particles explode
outward
leaping from one magnetic field line to
another further distorting the picture
around the sun's equator
but over the poles there should be less
turmoil and therefore greater simplicity
that simplicity should bring valuable
insight into processes in the corona
while ulysses is near the poles it will
also measure cosmic rays
particles from dying suns far more
distant than our own
cosmic rays are born in the cataclysm of
supernovas
old stars which suddenly explode with
unimaginable violence
hurled across space with incredible
energy cosmic rays bear the signature of
the events that formed
but cosmic rays entering the solar
system near the equator interact with
the solar wind and the sun's magnetic
field
as a result they are changed so
dramatically as to be nearly
unrecognizable
above the poles however cosmic rays
should change very little enabling us to
understand the messages of cosmic events
long past
i sometimes get asked why we do missions
like ulysses
well humans are curious beings and we
like to know what's over the next hill
so to speak
and just like in dante's story ulysses
went off to explore unknown lands
the ulysses spacecraft is our way of
exploring unknown regions of space
and our reward will be a better
understanding of the environment in
which the earth moves
and also a better understanding of that
star that means so much to us the sun
you