Preflight Interview: Kevin Kregel
we get into details about this flight, I want to know a little
bit about you. Why did you want to become an astronaut?
on Long Island, I was inspired by the early astronauts that were
going to the moon in the Apollo, the Gemini and the Mercury missions.
Grumman Aerospace is big on Long Island and so it was covered
very highly there. So it's something I've always wanted to do
since I was a little child. I aspired to go the same route as
the original astronauts and that is why I became an Air Force
test pilot, got an engineering degree, and applied to the program.
me an overview of your career that got you to where you are right
off by going to the Air Force Academy and graduated in 1978. I
went on to pilot training and flew F-111s over in England. I did
an exchange tour with the Navy and flew 86s at Whidbey Island
and did a carrier tour on the USS Kitty Hawk. The Air Force selected
me to go to test pilot school, but they sent me to the Navy test
pilot school at Patuxent River. I did that for a year, and then
I went down to Eglin Air Force Base and did flight tests on F-15,
F-15E and F-111 airplanes. Then in 1990 I left the service and
got hired by NASA as an instructor pilot and test pilot here at
the Johnson Space Center flying in aircraft ops, flying T-38s and the Shuttle Training Aircraft. Then I was fortunate enough
in 1992 to be selected as an astronaut.
for me what you'll be doing during this flight. What are your
primary responsibilities as the Commander?
As the Commander,
my primary responsibility is to make sure that we get into orbit
safely and get home safely and that the mission is conducted in
a very thorough and efficient manner. Those are my prime responsibilities.
This is, as you know, a 24-hour mission, so we're splitting ourselves
up into Red and Blue Shift. There will be myself on the Red Shift.
My Pilot, Dom Gorie, will be on the Blue Shift. We have some maneuvers
that we have to do to keep ourselves in a circular orbit, so we'll
each be performing those various times throughout the mission.
shuttle mission will look back at the Earth using radar interferometry
to acquire topographic data. What is radar interferometry?
If you want
to think of that in simplistic terms, we're trying to get a 3D
image of the Earth to build a three-dimensional topographic view
of the Earth. How we will do that is we have one big radar in
the payload bay and then we have two antennas; the one in the
payload bay and one that's on a boom 200 feet away. By getting
these two images returned from the radar, we'll be able to infer,
to get a 3D-type image. Sort of like using two eyes to get depth
is this flight important? Is there really more to be learned about
the surface of the Earth?
One of the
things I found fairly fascinating when I was assigned to this
mission is that we've got a better 3D map of Venus and Mars than
we do of the Earth. To the accuracy that we're looking at, which
is about 30 meters, we right now only have about 3 to 5 percent
of the Earth mapped to this kind of accuracy. Of course, we've
been trying to map the Earth for ages and we're just trying to
do it a little bit better on this mission. And in eleven days
we can get a lot more than 3 to 5 percent.
Shuttle Imaging Radar-C, or SIR-C, and the X-band Synthetic Aperture
Radar, or X-SAR, flew in the shuttle in April and October of '94.
What are the innovations for SRTM that separate it from those
is different from the previous Space Radar Lab missions because
we've got this boom out and we've got two antennas. So instead
of just taking the one picture, we're taking two pictures 200
feet apart and that gives us the capability to get the 3D image.
On this one we're using the C-band radar, which is U. S., and
the X-band, which is German.
kind of resolution do you expect, and how does this compare to
other forms of spaceborne imaging?
to get about a 30-meter resolution for the C-band or about 15-meter
resolution on the X-band. That means that every 30 meters we'll
be able to get a height above the ground to a very good accuracy,
and some of the areas will be a little bit better, some will be
a little bit worse. As I said, for what we're doing for covering
the Earth, we only have 3 to 5 percent of the Earth. There are
things that can get more accurate using different techniques but
certainly not the area of coverage that we're looking at.
got a unique piece of hardware flying - the mast. Could you explain
the process of deploying the mast? What exactly happens? How long
does it take?
is 200 feet long. It is about twice the size of any structure
that we've put out in space before. It's a very clever device.
It folds in upon itself in about a 10-foot by 4-foot canister.
And then it has a little screw nut that unwinds these batons.
It's a hollow type cube, and we have 86 of these different sections
to make a very rigid structure. And at the end of this structure
is where we have the second antenna. And it'll take us about 17-20
minutes to go ahead and fully deploy the mast.
happens if the mast doesn't fully deploy? Could you do an EVA
to fix the problem?
If the mast
does not fully deploy or, for that matter, if it doesn't fully
retract, we have contingencies to go ahead and do a spacewalk
and try to fully retract it or fully deploy it. And also, the
design of the mast is redundant in a lot of different ways, so
the likelihood of that happening is very low. But we are trained
and prepared to do that if necessary.
keep harping on the problems here, but does the mast need to be
fully deployed to get acceptable science? Can you get any information
at all if it only partially deploys?
The way our
rules are and the way we've designed everything, we need to have
the mast fully deployed to get a successful mission. And the big
reason is we want to make sure it's certified to fly around with
it fully deployed. Partially deployed it has different strength
properties. So if it's not fully deployed and we can't determine
it's fully deployed, then, more than likely, we'll retract it
and try to figure out what the problem is.
understand the length of the boom creates its own special problems.
What is the gravity gradient force and how does the boom affect
it? What do you do to counteract it?
gradient is just a natural position that any kind of spacecraft
that doesn't have any thrusters would want to go to. We've got
a specific attitude that we want to point the radar at the Earth,
and we want to stay that way all the time. With this big mast
out there, there's a natural tendency for the body to move out
of the position that we want to. So, we'd have to constantly fire
jets using propellant to stay in the proper attitude. The folks
at the Jet Propulsion Lab have designed a very small cold gas
thruster on the tip of the boom which counteracts the gravity
gradient force so that we don't have to use precious onboard propellant.
is the fly cast maneuver and why are you using that?
The fly cast
maneuver is what we are using to maintain a circular orbit. Again,
in order to maintain the accuracy of the radar data, we need to
maintain a fairly circular orbit. And, of course, because of our
boom out there, there is a little bit of drag, and our orbit decays
gradually over time. So, about once a day, we'll want to raise
up the orbit. We've got this antenna on this 200-foot mast out
there, and if we just used our normal thrusters in a normal manner,
the mast would spring and possibly break, which of course we don't
want. So the engineers here, between Johnson Space Center and the Jet Propulsion Lab and the folks at the Draper Labs, have
designed a system where we'll put in an impulse, the mast will
start moving, we'll stop the impulse. Right before the mast starts
coming back and swinging back to its natural position, we'll add
some more impulse, and it will kind of freeze the mast right there.
This way we'll proceed and raise our orbit, and then, we'll stop
the pulse. The mast will go back towards the neutral position,
and as it comes in the neutral position, we'll put one more pulse
in there to kind of freeze it so the mast doesn't ring out and
also doesn't go outside the limits of its structural certification.
is the process of mast retraction? Is it just simply a reverse
of the deploy?
is. We will flip the antenna, and then we will retract the mast.
Obviously, we will be looking at it very carefully, making sure
that it rotates into the canister very nicely and precisely.
if there is trouble with the retraction? What if it gets stuck?
Can the mast be jettisoned?
we would jettison the mast, we'll try everything we can to use
different motors and get it in and see what the real problem is.
We could do a spacewalk if the problem was something mechanical,
but we can if all else fails because we cannot come back with
that mast hanging out there. We can safely jettison the canister
and the mast.
the surface, this has similarities to the Tethered Satellite Systems
flights. You've got this long system coming out of the cargo bay.
Do you anticipate having any concerns similar to the issues associated
with those flights?
like Tether, anytime you have something that we've not done before
(and we haven't done a mission like this before), you have to
have concerns on what may happen. You don't expect them, but you
have to expect the unexpected. One of the things is, if we do
have a failure with the mast and how [will we] safely get away.
We've trained hard, and we've also talked to the engineers, and
we have flight rules in place to keep us safe.
you have any specific mapping targets on the Earth's surface as
they did on the SRL missions?
piece of landmass between 60 degrees north and 60 degrees south
is our targets.
a big target there.
the radar on for the entire flight? Are you collecting data as
you fly over the oceans?
collecting data when we fly over the oceans. The radar is just
for landmass and the radar also uses a lot of energy. We only
have a certain amount that we can carry on this flight. So, whenever
we're not taking data, we'll have the radar on a standby mode
so we're not using up our process energy.
is the data being recorded instead of downlinked live?
of our recorders is four times faster than the rate that we can
downlink. So, we can't downlink the data real time [and] get the
accuracy that we need. We're doing some playbacks. We'll actually
slow down the tapes to a quarter of the natural speed so that
the folks on the ground can get snapshots of what we're seeing
in orbit and making sure that the recorders and the radar [are]
working properly. But all told, we will have nine terabytes worth
of data which, I'm told, is equivalent to 15,000 CDs.
you're gathering a lot of data there. How long will it take to
process all this data?
to process the data, it probably will take a couple of years.
You know, they'll get snapshots out in a year, but it really will
be a tremendous amount of data that will be analyzed by a lot
of different folks around the world. There will be years as this
data comes out and is available to different agencies and to the
the X-band data and the C-band data processed similarly?
processed very similarly. Of course, as I said the X-band data
is going to the Germans. The C-band data is going to NIMA or the
National Imagery and Mapping Agency.
something interesting on this flight. The two ASTRO astronomical
observation flights used the Star Tracker, and SRTM utilizes it
in a new way. Can you tell me about the Star Tracker and how it
is that you're using it?
We use the
Star Tracker to know the exact position of the outboard antenna.
We also have some Global Positioning System receivers on the outboard
antenna because it's very critical to know where that position
is, so when you get the return signal you know that it's a true
signal, and it's not just the fact of the antenna bouncing up
and down. This is another way the Jet Propulsion Lab shows its
innovation. They have these Star Trackers that they have from
previous missions. They were sitting around. They said let's go
will we learn about the Earth from the data you do acquire on
We will learn
the 3-D, three-dimensional, topographic map, which, of course,
can be used for national security. It can also be used to, perhaps,
look at earthquakes. A lot of the areas in Central America and
Africa are covered by clouds. We know very little about their
topographic area. Perhaps it can be used by governments to decide
where not to put folks that are susceptible to landslides. You
can use it for urban planning. You can use it for farmers' fields,
and I'm sure as folks see this data come out, there will be lots
and lots of other uses that I'm not even thinking about and that
folks haven't thought about.
you're up there, if a volcano erupts or there's some other type
of natural disaster, will you be able to pay any special attention
is pretty much set before we launch, and that's because we have
to go over the same area twice in order to get the accuracy that
we want for this data. So [the] only maneuvering that we will
be doing to change our orbit is to get the data and the world
coverage that we want. If it so happens that we have a world event
and we're going over that track, obviously, we'll take pictures
of it, but we won't alter our track in order to take pictures
of hurricanes, or volcanoes, or the like.
once the payload is functioning just fine, the crew kind of slips
into a regular routine. Do you think the work will get boring
or tiring for you?
I can't see
how anyone who's spent any time in space would say it would be
boring. I can spend two weeks easily there just looking out the
window. We're going to be kept pretty busy. We've got to do maneuvers
every 45 minutes to maintain the accuracy that's required. We
have to change out the tapes. We're there to back up when ground
commanding is not available, to go ahead and start taking the
data. Any time we go over land, if we're not taking data, it's
data that we've missed and we cannot recoup on the rest of the
flight. So, it will be the same thing, but I don't think it will
be boring. It will keep us busy the whole time.
mission includes international partners. What exactly are they
partners Gerhard Thiele and Mamoru Mohri are both full-up Mission
Specialists that are doing the same jobs as the Americans onboard.
It's really showing us how far we've come towards the International
Space Station. We don't have the folks doing just experiments
from their own country. They're full-up crewmembers just like
is the National Imagery and Mapping Agency and how are they involved
in the flight? Then, just describe for me the relationship between
NASA and NIMA.
the National Imagery and Mapping Agency, is really a sponsor for
this mission. They are the customer that said that they were willing
to spend the money to get the data to map the majority of the
Earth. The Jet Propulsion Lab are the folks that built the equipment,
and they were looking for a sponsor. NIMA is the agency that said
yes, they would like this data. NIMA was just formed about three
years ago and is combined through several different agencies.
The intelligence community and the military community, they form
maps for our government and also maps for airplanes, when you
go flying around on the airways throughout the United States and
throughout the world.
NIMA get digital topographic data from their own satellites, and,
if they do, why do they need this flight?
several different ways to get data, and a lot of them I'm not
privy to. But our mission is a lot different. They've been trying
specifically for ten years using other resources that they have
to get to this data to this kind of accuracy. In the last ten
years, they got three to five percent. We can get most of the
landmass between 60 degrees north and 60 degrees south in ten
to eleven days. Probably money well spent.
me about EarthKam. Is it comparable in any way at all to the flight's
is comparable to the payload in that [they're] both looking at
the Earth, and EarthKam is a project set up by the folks at [the]
University of California, San Diego to help kids get involved
in space. We've got a camera that is mounted in our overhead window,
and that camera will be commanded by different schools that the
folks in California have selected throughout the United States
and throughout Germany and Japan. In the future, it will be other
countries. So, these students will decide what pictures they want
to take. So, they'll see when the orbiter's flying over different
landmasses, and they'll say, "Okay, we'd like a picture taken
at this time." They'll be able to get feedback (because it will
come down through the downlink) and see how their picture turned
out. So, it's an interactive way of getting kids involved in space.
summing up, how would you characterize the long-term importance
to science of the work you and your crewmates will be doing on
I think the
data that we get from STS-99, mapping the Earth will change a
lot of the way we do things in terms of any kind of geography.
Urban planning, mission planning, looking at earthquakes, looking
at farms. We'll just be the start of it, but we will hopefully,
in ten or eleven days, multiply many times our knowledge of our
Mother Earth. And I think that will be really important. It will
take a while to crank out that data, but I think [it] will keep
a lot of scientists busy for a long, long time.