You're going into an environment that's
completely unforgiving. The temperatures
that we're seeing on the spacecraft
have not been seen by any other
spacecraft ever before. The scariest
thing about the Sun is the unknown. We
see it every day
but we see it from 93 million miles away.
This first perihelion were going into we
have very minimal contact - all we can
get is a tone. I'm going to be waiting on
the edge of my seat for those beacon
tones. The Sun facing side will be exposed to in excess of 2,500 degrees Fahrenheit
We're gonna go closer to the Sun than
any other spacecraft has gone before. We're
not going to do that once we're not
gonna do it twice - we're gonna do that 24
times - and that is terrifying. We really don't know what we're gonna find until we get
there. 
In 1958 Gene Parker had an idea that the
area around the Sun would behave in a
certain way. There are two really
overarching mysteries that we have
always wanted to study: why is the corona
hotter than the surface of the Sun? Why
is the solar wind continuously
accelerated? We are now in what we call
our encounter attitude the TPS is pointed
at the Sun and we will not leave that
attitude until we get back around the
backside of the Sun. So we keep the
thermal shield between the spacecraft
body and the Sun. We have designed the
spacecraft to be able to do the right
thing no matter what it sees. You can't
do Parker Solar Probe unless you're
willing to build a spacecraft that could take care of
itself; you can't build Parker Solar Probe
unless you can build a shield that could
withstand the thermal environment; you
can't do Parker Solar Probe unless you
can keep the power generation cool - and
all these things contain some level of
risk.
The Sun is a wideband radio source so
any spacecraft is either in front of the
Sun behind the Sun or near the Sun you
can't talk to it. Parker Solar Probe is
designed to transmit four different kinds of beacon tones A is a good beacon,
the fault management system is reporting
that all systems are nominal.
The other three tones mean that some
type of fault has occurred on board. We
will be mostly out of contact with the
spacecraft through encounter so the only
thing we will have is those beacon tones.
We will be all waiting for the call: "APL,
APL - I am Parker Solar Probe. I'm doing well, and I have surprises for you. The fear
and tension and stress is all going to
be focused on those last few minutes.
This truly is a mission of discovery.
