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3819 - RADIO FREQUENCY
ASTEROIDS - see what's coming? An experiment to bounce a radio signal off an asteroid on
December 27, 2022 will serve as a test
for probing a larger asteroid that in 2029 will pass closer to Earth than the many geostationary
satellites that orbit our planet.
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--------- 3819
- RADIO FREQUENCY
ASTEROIDS - see what's coming?
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- The “High-frequency Active Auroral Research
Program” research site in Gakona will transmit radio signals to asteroid “2010
XC15”, which is about 500 feet across.
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- This will be the first use of “HAARP” to
probe an asteroid. What’s new and what
we are trying to do is probe asteroid interiors with long wavelength radars and
radio telescopes from the ground. Longer
wavelengths can penetrate the interior of an object much better than the radio
wavelengths used for communication.
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- Knowing more about an asteroid’s interior,
especially of an asteroid large enough to cause major damage on Earth, is
important for determining how to defend against it.
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- Many programs exist to quickly detect
asteroids, determine their orbit and shape and image their surface, either with
optical telescopes or the planetary radar of the “Deep Space Network”, NASA’s
network of large and highly senstive radio antennas in California, Spain and
Australia.
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- These radar-imaging programs use signals of
short wavelengths, which bounce off the surface and provide high-quality
external images but don’t penetrate an object.
HAARP will transmit a continually chirping signal to asteroid 2010 XC15
at slightly above and below 9.6 megahertz (9.6 million times per second). The
chirp will repeat at two-second intervals.
The asteroid will be twice as far from Earth as the moon is.
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- The University of Alaska Fairbanks operates
HAARP under an agreement with the Air Force, which developed and owned HAARP
but transferred the research instruments to UAF in August, 2015.
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- The test on “2010 XC15” is yet another step
toward the globally anticipated 2029 encounter with asteroid “Apophis”. It
follows tests in January and October in which the moon was the target of a
HAARP signal bounce.
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- Apophis was discovered in 2004 and will
make its closest approach to Earth on April 13, 2029, when it comes within
20,000 miles. Geostationary satellites orbit Earth at about 23,000 miles. The
asteroid, estimated to be about 1,100 feet across, was initially thought to
pose a risk to Earth in 2068, but its orbit has since been better projected by
researchers.
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- The test on “2010 XC15” and the “2029
Apophis” encounter are of general interest to scientists who study near-Earth
objects. But planetary defense is also a key research driver. The more time there is before a potential
impact, the more options there are to try to deflect it.
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- NASA says an automobile-sized asteroid hits
Earth’s atmosphere about once a year, creating a fireball and burning up before
reaching the surface. About every 2,000
years a meteoroid the size of a football field hits Earth. Those can cause a
lot of damage. And as for wiping out civilization, NASA says an object large
enough to do that strikes the planet once every few million years.
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- NASA first successfully redirected an asteroid
on September 26, 2022 when its “Double Asteroid Redirection Test mission”, or
DART, collided with Dimorphos. That asteroid is an orbiting moonlet of the
larger Didymos asteroid.
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- The DART collision altered the moonlet’s
orbit time by 32 minutes. The December
27, 2022, test could reveal great
potential for the use of asteroid sensing by long wavelength radio signals.
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- Approximately 80 known near-Earth asteroids
passed between the moon and Earth in 2019, most of them small and discovered near
closest approach.
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- Dark Energy Camera at Cerro Tololo
Inter-American Observatory in Chile have enabled astronomers to spot three
near-Earth asteroids (NEA) hiding in the glare of the Sun.
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- These NEAs are part of an elusive
population that lurks inside the orbits of Earth and Venus. One of the
asteroids is the largest object that is potentially hazardous to Earth to be
discovered in the last eight years.
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- An international team using the Dark Energy
Camera (DECam) has discovered three new near-Earth asteroids hiding in the
inner Solar System, the region interior to the orbits of Earth and Venus. This
is a notoriously challenging region for observations because asteroid hunters
have to contend with the glare of the Sun.
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- By taking advantage of the brief yet
favorable observing conditions during twilight, however, the astronomers found
an elusive trio of NEAs. One is a 1.5-kilometer-wide asteroid ,“2022 AP7”,
which has an orbit that may someday place it in Earth’s path. The other
asteroids, “2021 LJ4” and “2021 PH27”,
have orbits that safely remain completely interior to Earth’s orbit.
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- Also of special interest to astronomers and
astrophysicists, 2021 PH27 is the closest known asteroid to the Sun. As such,
it has the largest general-relativity effects of any object in our Solar System
and during its orbit its surface gets hot enough to melt lead.
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- Einstein’s general theory of relativity
explains how massive objects warp the fabric of spacetime and how this
influences the motion of objects in the Universe. In our Solar System, this
influence can be directly measured as the precession of the orbit of planet
Mercury, which cannot be accurately explained using only Newtonian physics.
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- Astronomers have found two large near-Earth
asteroids that are about 1 kilometer across, a size that we call “planet
killers.” There are likely only a few
NEAs with similar sizes left to find, and these large undiscovered asteroids
likely have orbits that keep them interior to the orbits of Earth and Venus
most of the time. Only about 25
asteroids with orbits completely within Earth’s orbit have been discovered to
date because of the difficulty of observing near the glare of the Sun.
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- Finding asteroids in the inner Solar System
is a daunting observational challenge. Astronomers have only two brief
10-minute windows each night to survey this area and have to contend with a
bright background sky resulting from the Sun’s glare. Such observations are very near to the
horizon, meaning that astronomers have to observe through a thick layer of
Earth’s atmosphere, which can blur and distort their observations.
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- Observing toward the inner Solar System is
challenging for ground-based telescopes and impossible for space-based optical
/ infrared telescopes like NASA’s Hubble and JWST telescopes. The intense light
and heat of the Sun would fry the sensitive electronics. For this reason, both
Hubble and JSWT are always pointed away from the Sun.
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- Discovering these three new asteroids
despite these challenges was possible thanks to the unique observing
capabilities of DECam. The state-of-the-art instrument is one of the
highest-performance, wide-field CCD imagers in the world, giving astronomers
the ability to capture large areas of sky with great sensitivity.
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- Astronomers refer to observations as ‘deep’
if they capture faint objects. When hunting for asteroids inside Earth’s orbit,
the capability to capture both deep and wide-field observations is
indispensable.
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- Large
areas of sky are required because the inner asteroids are rare, and deep images
are needed because asteroids are faint and you are fighting the bright twilight
sky near the Sun as well as the distorting effect of Earth’s atmosphere.
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- DECam can cover large areas of sky to
depths not achievable on smaller telescopes, allowing us to go deeper, cover
more sky, and probe the inner Solar System in ways never done before.
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- Asteroids that are further from the Sun
than Earth are easiest to detect. Because of that these more-distant asteroids
tend to dominate current theoretical models of the asteroid population.
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- “Atria asteroids” are the smallest group of
near-Earth asteroids. Their orbits have an aphelion (farthest point from the
Sun) smaller than Earth’s perihelion (nearest point to the Sun).
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- The “DECam survey” is one of the largest
and most sensitive searches ever performed for objects within Earth’s orbit and
near to Venus’s orbit. After ten years
of remarkable service, DECam continues to yield important scientific
discoveries while at the same time contributing to planetary defense.
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January 10, 2022 RADIO
FREQUENCY ASTEROIDS ? 3819
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“Jim Detrick” -----------
--------------------- --- Tuesday, January 10, 2023 ---------------------------
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