Mars Team Online WebChat
Date: March 11, 1998
Featuring: Rich Hogen
Operations, Mars Global Surveyor
Lockheed Martin Astronautics, Denver, Colorado
[ Sandy/NASAChatHost - 30 - 10:22:53
Welcome to today's chat with Rich Hogen! Rich will be here in approximately
40 minutes. In the meantime, if you haven't had a chance to read his very
interesting bio, please do so at: http://quest.arc.nasa.gov/mars/team/hogen.html
Have your questions ready :-)
[ Sandy/NASAChatHost - 32 - 10:53:38
RE: [Kye-Carl/homeschooled] Hi Sandy! I'm really
glad to see the internet behaving better today!!!
Hi Kye and Carl! I'm glad to see you made it to chat room. And I agree with
you about the Internet's behavior-- let's hope it's on its best behavior
today! Rich should be here shortly... Where are you two from and what grade
are you in?
[ MrsTsurunagasClass-Nancy/WoodlandHillsElementaryLAUSD - 34
- 10:58:15 ]
We are a 5th grade class in Woodland Hills, CA.
[ Sandy/NASAChatHost - 35 - 10:58:35
Our whole class is here. We're looking forward to chatting with Rich.
Wow, that's great! Welcome to all of you :-) Where is Woodland Hills Elementary
located? And how many are in your class? Rich will be here in 5 minutes...
[ Sandy/NASAChatHost - 39 - 11:02:56
RE: [Kye-Carl/homeschooled] Carl is my son,
who is in the 11th grade. We are in our 9th year of home schooling.I am
also especially interested in the Mars chats because I have an educational
web page (as a hobby), using astronomy and space exploration to help kids
have fun learning about math and science. I especially look for space
events that are in the news (like water ice found on the Moon and ?Mars?
because I also give them things to do with direct observations from their
yard, being an avid amateur astronomer.
Sounds like you do some pretty interesting and innovative stuff for your
son and other kids as well! You might want to consider joining our project's
discuss mail list to chat with other teachers and parents to share ideas.
[ MrsTsurunagasClass-Nancy/WoodlandHillsElementaryLAUSD - 40
- 11:03:09 ]
There are 40 of us here today for the chat. Woodland Hills is in the West
San Fernando Valley near Los Angeles.
[ Sandy/NASAChatHost - 41 - 11:03:43
RE: [Rich/LMA/Denver] Hello, everyone. I'm here! How can
I help you?
Welcome Rich. thanks so much for taking the time to chat with all of us
today :-) Ok everyone, let your questions fly!
[ Rich/LMA/Denver - 46 - 11:05:31
Hi Rich! How long does it take for one rotation of the MGS around Mars?
Right now the period of MGS's orbit is about thirteen and a half hours.
We're shaving off about 6 minutes with each drag-pass.
[ Sandy/NASAChatHost - 47 - 11:05:36
RE: [Andrew-Elaine/EncinalSchool] Encinal school
is here and is very excited
Welcome Encinal School! Good to see you here :-)
[ Rich/LMA/Denver - 49 - 11:07:26
Also, Rich. If you suspected that there might be water on Mars, why didn't
you include a drilling module with the MGS?
A drilling module is an interesting idea, but it requires actually getting
down to the surface of the planet. MGS, Mars Global Surveyor, is a remote
sensing spacecraft, like weather satellites and others in orbit around
Earth. The Mars Polar Lander mission carries "penetrators", as I recall,
which will do exactly what you suggest.
[ Rich/LMA/Denver - 51 - 11:09:54
RE: [Kye-Carl/homeschooled] Hi Rich - I'm interested
in your work with pointing the High Gain Antenna and Solar Arrays. I am
putting activities together for my web site for children to do to better
understand how we use right triangle in science and engineering. They
use a quadrant (made from my pages) to measure different things, using
tangents to find the unknowns. Do you have suggestions for things to do
along these lines?? (pun intended on the "lines")
Wow, Kye! Right off the top of my head I'm finding it hard to jump from
all the three-dimensional vectors I worked with in my spreadsheet to 2D
triangle exercises. Tell you what, please send me an email (including
the URL for your educational web site) and I'll think about that off-line.
[ Rich/LMA/Denver - 53 - 11:13:40
RE: [Nick-Nicholas/IronHorse] How do you control
the MGS now?
That's a pretty broad question, Nick, and a good one. MGS has a computer
onboard with software running that diagnoses it's health and performs
routine "autonomic" functions, kind of like a heartbeat and breathing.
When we need it to do more, we send "sequences" to it. Sequences are essentially
scripts, like a checklist or a recipe, saying, "do this thing at this
time". Working out the order of events and the timing is actually very
important and care has to be taken, so we have special software on the
ground that performs all the right checks for MGS. There's more to it,
but that's the general idea of how we control the spacecraft.
[ Rich/LMA/Denver - 56 - 11:17:34
Can you explain how "drag pass" works?
A "drag pass" is what happens when the periapsis of MGS (the point in
the orbit closest to Mars) is low enough to subject MGS to atmospheric
drag, the same kind of drag that holds up kites or that you feel when
you ride a bicycle. On the way into a drag pass, the "sequence" tells
the spacecraft to do several things: turn your solar panels this way so
we can pre-charge the batteries, then stop rotating and point the instrument
deck this way, pull the solar panels up and back for stability in the
"wind", then start rotating this way, ..., and then on the way out do
[ Rich/LMA/Denver - 57 - 11:18:10
RE: [Kye-Carl/homeschooled] Rich - Nice web
site! Who's brain is in the vat?
Ah, that's the question, isn't it?
[ Rich/LMA/Denver - 61 - 11:24:17
How does aerobraking work?
Another fine and yet very broad question. Through experiments, scientists
over the years have learned how to use certain mathematical equations
to represent the drag (frictional) forces caused by fluids, like atmospheric
gases. An extension of that is our collective experience with global climate
and weather modelling. Also, with experience building aircraft and rockets,
engineers and scientists use the fluid models to design things that flow
through the air more easily, with less drag. (look at old automobiles
and compare them with newer, more aerodynamically efficient ones) So,
Dr. Bill Willcockson at Lockheed Martin thought, "why not use a weather
model of Mars, the fluid drag equations and an aerodynamically stable
spacecraft to use the atmospheric drag of Mars to slow the spacecraft
down, remove energy from it's orbit, without requiring fuel?" In the past,
atmospheric drag was thought of as a problem to be overcome, but gradually
people like Bill turned it into a useful tool.
[ Rich/LMA/Denver - 64 - 11:28:22
Here's your chance to go out on a limb, Rich. Do you believe we'll find
life on Mars?
Well, you know, every time I think about it I convince myself that it's
possible we'll find life on Mars, or evidence of past life, then I think
further and I realize it's also possible that either we'll never find
it or that it doesn't exist to be found. Unless we have evidence either
way, it's perfectly alright to have a "suspended belief", neither way.
I _do_ believe that the question is extremely interesting and incredibly
important to humanity, and I don't squelch my wonder and awe the question
and the possiblities.
[ Rich/LMA/Denver - 65 - 11:30:14
RE: [Kye-Carl/homeschooled] Rich - I'm a mostly
self-taught programmer (basic, C, C , JAVA). What kind of programming
do you use for communicating with the spacecraft, and what kind of programming
do you do the shareware in?
Our main sequence building tool is an Excel spreadsheet written by my
esteemed colleague Wayne Sidney. At JPL there are other pieces of software
that we use but do not "own", so I have no idea what language their written
in. My shareware was written in Delphi, which is "visual object pascal".
[ Rich/LMA/Denver - 68 - 11:33:15
RE: [Nick-Nicholas/IronHorse] What kinds of
data are you collecting from the MGS?
We receive two kinds of data, engineering data and science data. All the
data is stored on two database servers, and those who need it run queries
to retrieve what they need. The Spacecraft Team works exclusively with
engineering data (monitoring and trending the health of the spacecraft),
except in the case of the Mars Horizon Sensor Assembly (MHSA), which is
a science instrument being used to watch the deflection of the broken
solar panel. The scientists query their respective science data. For details
on that, please visit the MGS home page and step through the great slide
show they have in the images area.
[ Rich/LMA/Denver - 72 - 11:40:19
Jonathan would like to know what the surveyor will be looking for when
it reaches its final orbit around Mars.
MGS will be looking for all kinds of data in the final orbit, the same
kind of data it was collecting earlier in aerobraking before we had to
stop performing science observations. (that was necessary to allow us
to keep the spacecraft alive -- you can't do anything with a dead spacecraft)
The difference is that in the final orbit the geographical resolution
("level of detail") will be highest. The instruments are collecting data
on everything about Mars, which is why it's called "Surveyor", things
like: images of the geology, altitude of geological features, mineral
types and distributions, atmospheric density and composition, gravity
map of the planet, magnetic field and charged particle measurements, etc.
It's pretty amazing what creative scientists can get out of a single data
set. They'll be analyzing MGS data for a long time.
[ Rich/LMA/Denver - 73 - 11:42:25
Spencer would like to know how the solar panel wing broke, and how will
you try to fix it?
The panel broke when a "damper" failed. The damper was supposed to slow
the panel down during deployment, so it wouldn't just "snap" straight
and break itself. The damper broke and "ate into" part of the panel, which
is why the panel couldn't fully deploy for a long time. There's no way
to fix it now that MGS is so far from our reach.
[ Rich/LMA/Denver - 74 - 11:43:06
RE: [SpencerK-Elaine/EncinalSchool] What spacecraft
were you most proud of to work on?
This is my first spacecraft-related job, so MGS is the one! (some expert
I am, eh?)
[ Rich/LMA/Denver - 75 - 11:43:43
RE: [Kye-Carl/homeschooled] Rich - My last
Live From Mars email newsletter (#67) talks about the radio science team
using transmissions from MGS just before it goes behind the planet to
learn more about Mars' atmosphere from the distortions in the radio signals
while they pass through it. Would a decent demonstration of distorted
radio signals be the old AM/FM radio receiver with the aluminum foil lined
umbrella in front of it? Or would more of a visual demonstration like
the way water bends light be appropriate?
Let's talk about such details off-line.
[ Sandy/NASAChatHost - 77 - 11:46:11
Thanks for answering our questions, Rich. The lunch bell is ringing!
Thanks so much for your great questions and for participating in today's
chat! Hope you can join us again for the upcoming chat!
[ Rich/LMA/Denver - 78 - 11:46:40
RE: [Nick-Nicholas/IronHorse] How long will
the MGS remain in orbit around Mars?
The plan, as I understand it, is to reach final mapping orbit in April,
or so, 1999, then do mapping for a Martian year (two Earth years). When
that's done, MGS will fire it's thrusters to push the spacecraft into
a higher orbit that will not decay for at least 50 years. There is an
international agreement to not allow spacecraft debris to get into the
Mars system where it might confuse our measurements while we learn about
[ Rich/LMA/Denver - 79 - 11:47:35
RE: [Sandy/NASAChatHost] Thanks so much for your great
questions and for participating in today's chat! Hope you can join us
again for the upcoming chat!
You're quite welcome.
[ Sandy/NASAChatHost - 80 - 11:47:37
EVERYONE: Just another 10 minutes and then we have to let Rich go and
get back to his REAL work! A few more questions and then we'll call it
[ Rich/LMA/Denver - 84 - 11:52:50
RE: [DarianS-Elaine/EncinalSchool] How did
Space Exploration attract you as a child?
It started with television, then as I started to learn about how the world
works I saw more and more how wonderful and awesome and beautiful it is,
and that happened at the same time we were all starting to realize how
fragile our biosphere is because the Apollo and Skylab photos of Earth
gave us a larger perspective. There isn't any one or two things I can
point to, but I do know that the more science I learned the more wonderful
the universe became, and once you realize that you're on a small planet
living in a very thin, fragile and precious biosphere, you can't go back,
you start thinking in "the big picture".
[ Sandy/NASAChatHost - 85 - 11:52:51
RE: [Nick-Nicholas/IronHorse] Thanks a whole
lot Rich and Sandy for telling us about Mars and the MGS
Nick, you're most welcome :-) Hope you can join us for the next chat!
[ Rich/LMA/Denver - 86 - 11:53:09
RE: [Nick-Nicholas/IronHorse] Thanks a whole
lot Rich and Sandy for telling us about Mars and the MGS
[ Rich/LMA/Denver - 87 - 11:53:35
RE: [Kye-Carl/homeschooled] Rich - Thanks for
your time! You are really good at explaining these things. Also, your
advise in your bios is great. Knowing how to go find out about something
(research and learn) is so much more important than memorizing facts!
Thanks again, and good luck with your mission.
You're welcome! And thanks.
[ Rich/LMA/Denver - 89 - 11:55:46
RE: [Doug/ArapahoeHigh-Doug/ArapahoeHigh] Rich,
does Lockheed-Martin have a webb site that might show some data from MGS,
or is it best to go to a JPL site? Thanks-keep up the great job!
Yes, we have a public telemetry page if you want to see engineering data.
Send me email and I'll get you the URL. As for science data, your best
bet is the JPL pages. (you're welcome and thanks for joining us)
[ Sandy/NASAChatHost - 90 - 11:58:06
Everyone: It looks like today's chat has come to an end. thanks to all
the participants! You did your homework and asked some really good, thoughtful
questions :-) And Rich, a special thank you to you for taking time out
of your day to spend with us today. Your answers were very informative
and I actually learned a few new things today! Thank you :-)
[ Rich/LMA/Denver - 91 - 11:58:50
RE: [Sandy/NASAChatHost] Everyone: It looks like today's
chat has come to an end. thanks to all the participants! You did your
homework and asked some really good, thoughtful questions :-) And Rich,
a special thank you to you for taking time out of your day to spend with
us today. Your answers were very informative and I actually learned a
few new things today! Thank you :-)
My pleasure. Thanks for setting up the MTO program!
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