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Multidisciplinary
Design, Analysis, and
Optimization Branch
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EDUCATIONAL ACTIVITIES: THE NASA AEROQUIZ
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Week of 6/4/01:
Q:
As of this writing, on how many celestial objects have spacecraft landed?
A:
Venus (Soviet Venera missions)
Earth (I assume this counts!)
Earth's Moon (Soviet Luna)
Mars (Soviet Mars)
Jupiter (the probe from the Galileo spacecraft)
Asteroid Eros (NASA NEAR mission)
Total: Six
Congratulations to Alan R. Nies.
Alan named two I missed: Earth and Jupiter! The Galileo probe
descended into Jupiter's atmosphere on December 7, 1995. Although it
did not "land," it plunged deep into the atmosphere before
contact was lost 61 minutes into the descent at a pressure of 22 atmospheres.
The latest landing was the remarkable Near Earth Asteroid Rendesvous (NEAR)
mission on Feb 12, 2001, on Eros. The (originally unplanned) landing
was a long shot, but the NEAR Shoemaker space probe
managed not only to survive the landing it was not designed to do, it
maintained communications with Earth.
The Eros touchdown speed was 1.5 to 1.8 m/s. This compares to the Martian
Vikings at 2.4 m/s, the lunar Surveyors at 3 m/s,
and a typical aircraft carrier fighter sink rate of 3.5 m/s.
The other first landings were
Luna 9 Feb 3, 1966
Venera 7 Dec 15, 1970
Mars 3, Dec 2, 1971 (all Soviet)
- The Aeroquiz Editor
Week of 6/11/01:
This week's question is from Ann Delleur, formerly of the Jet Propulsion
Laboratory during NASA's Voyager encounters with Jupiter and Saturn!
Q:
In photographs from the Apollo missions (and many others) there
are small crosses at regular intervals on the images. What are
they for?
No one got the correct answer. The question stands another week!
- The Aeroquiz Editor
Week of 6/18/01:
This week's question is from Ann Delleur, formerly of the Jet Propulsion
Laboratory during NASA's Voyager encounters with Jupiter and Saturn!
Q:
In photographs from the Apollo missions (and many others) there
are small crosses at regular intervals on the images. What are
they for?
A:
The Hasselblad Data Cameras used on the Apollo missions were fitted
with a special glass plate mounted very close to the film. The
plate was engraved with a number of calibrated crosses in a grid
pattern. The crosses, which appear on every exposed frame, provide
a means to determine angular distances between objects in the field
of view.
I may be the WEAKEST LINK, but that's my FINAL ANSWER anyway!
Congratulations to Alan R. Nies.
And Ann provides further detail:
"The crosses or marks on images from spacecraft are used to reconstruct the
image on the ground. Basically they are alignment marks to make sure the
picture gets put back together correctly on the ground from the signal sent by
the spacecraft. The markers lined up when the image was taken, so when bits
that make up each pixel are received and the image is reconstructed, the image
processors know to line up the markers.
Viking (Mars lander) took with it to Mars a color pallet. When they turned the
camera on the color pallet, sent the picture back, they were able to match up
the colors to an identical color pallet here on Earth. Once they had the colors
calibrated, then they knew what the colors were of the other images they were
sending back to Earth.
The same is true of the Voyager pictures. Voyager had an alignment card that
the cameras could image. Also, each Voyager image had the initial cross hairs
in it. Since Voyager did not have a color camera, it had to take several
images, one with the red filter, one with a blue filter, etc and have the
images overlayed here on the ground to construct a color image. When the Image
Processing Lab at JPL created the color images, they took out the cross
hair/alignment markers so the pictures looked better."
- The Aeroquiz Editor
Week of 6/25/01:
This week's question was submitted by Brian Kitchen.
It's a seemingly simple question, but it is an analytically complex
problem with potentially far-reaching consequences!
Q:
Why is it that jet airliners, when cruising several miles overhead, sometimes
appear to trail long clouds behind them?
A:
The "clouds" are the condensation of the heated water vapor after coming
out of the hot jet engine. It's like seeing your breath on
a cold day.
Congratulations to Philip Stehno.
They're called condensation trails, or contrails, and they have been a
normal effect of jet aviation since its earliest days. Contrails
evaporate quickly if the ambient humidity is low, or persist and grow if the
humidity is high. One of the byproducts of combustion is water vapor.
If there is sufficient humidity in the exhaust plume, water condenses
on small particulate matter to form liquid droplets. These droplets then
freeze rapidly in the cold air at cruising altitude and form a contrail.
The area of concern among atmospheric scientists is when ambient humidity
is high and the contrails persist and grow in size by taking in existing
water from the surrounding atmosphere. Contrails can increase the cloudiness
of the atmosphere and can therefore have an effect on the Earth's temperature
and climate. How much of an effect contrails have on the Earth's climate
is a point debated by atmospheric scientists.
- The Aeroquiz Editor
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