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1993-08-05
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BID: $SPC0726
=========
SpaceNews
=========
MONDAY JULY 26, 1993
SpaceNews originates at KD2BD in Wall Township, New Jersey, USA. It is
published every week and is made available for unlimited distribution.
* EARTHQUAKES VIA SATELLITE *
=============================
Up to now, earthquakes have been poorly defined because pre-quake and post-
quake studies at a large number of sites was simply not possible. But now
with the advent of the ERS1 satellite, the situation has changed. ERS1
orbits at a height of 750 kms and views the world via a side scan synthetic
aperture radar on a frequency of 5.36 GHz. The satellite was used to study
the 28-Jun-92 earthquake centered in Landers, California.
ERS1 collected images of the Landers area 4 times in 1992. Once before the
quake, and 3 times after it. Each pixel is 4 x 20 meters and the satellite
receiver records both signal range and phase data of the echo returns from
the ground. Despite the fact that no two orbits follow exactly the same
track, it has proved possible to take the data from runs on 24 April pre-
quake and, 7 August post-quake and put them together with a high degree of
coherence.
To do this the operators reconstruct the phase of each pixel by minimizing
the number of fringes at the corners of the picture, assuming that far field
data in the picture corners will be least disturbed by the quake. They then
eliminate the stereo path difference using a differential elevation model,
and then calculate the interferometric fringes of the image at map
coordinates, before resampling to improve overall signal to noise ratio and
finally plotting what is basically a ground map covered in color coded
fringes where the quake has shifted the surface betwee the pre-quake and
post-quake records.
The result is a map of the Landers area overlayed by the "diffraction
pattern" of colored fringes. Each fringe can reveal a shift as little as
28mm, that is the half wavelength of the radar. Naturally with such a
precise record the middle of the pattern over the fault itself is blurred
because even with the small pixel size at the ground of 4 x 20 meters,
there has been a much larger ground shift than 28mm. Nevertheless, the
area near the fault has obvious breaks in the surface so a record at that
point is hardly necessary, and ERS1 provides a beautiful record out to
far beyond the edges of the total affected area.
This ERS1 technique has a precision never seen before. Indeed geologists
are now calling for records to be taken by ERS1 of all the world danger
spots including volcanoes which swell just before erupting, glaciers having
sudden spurts of movement which could foretell large killer landslides as
have occured in South America, and of course other active earthquake
fault lines.
ERS1 scans the same patch of ground every 35 days. It does not require
the positioning of ground stations in remote and often dangerous places.
So we should hear more about its successes in the future. ERS1 was built
and launched by the European Space Agency/ArianeSpace.
[Info via GM4IHJ]
* UOSAT-OSCAR-11 STATUS *
=========================
The following is the On-Board Computer (OBC) status of UoSAT-OSCAR-11 as
transmitted by the spacecraft on a frequency of 145.826 MHz and received
by KD2BD in New Jersey on 24-Jul-93:
** UoSAT-OSCAR-11 OBC **
Diary Operating System V3.2
Date: 24 /7 /93 (Saturday)
Time: 0 :28 :24 UTC
Auto Mode is selected
Spin Period: + 1394
Z Mag firings: 0
+ SPIN firings: 0
- SPIN firings: 11
SEU count 23923
RAM WASH pointer at E56
WOD commenced 24 /7 /93 at 0 :0 :9
with channels 10 ,11 ,19 ,29 ,
Last Command: 109 to 0 , 0
Attitude control initiated, mode 1
Data collection in progress
UoSAT-OSCAR-11 was designed and built by the Spacecraft Engineering Research
Unit of the Electronic and Electrical Engineering Department at the
University of Surrey in England. It was launched on March 1, 1984 from
Vandenburg Air Force Base in California. Its primary on-board computer is
designed around an RCA 1802 microprocessor, and its controlling software is
written in the "Forth" computer programming language.
* MAILBAG *
===========
The following message was received via packet radio from XE1RGL in Mexico,
and took nearly two months to be received in New Jersey:
Hello John, my name is Guillermo/XE1RGL. I live in the city of
Cuernavaca, which is located 50 miles south of Mexico city. I am
sending you this message just to say that SpaceNews is a great
information source for hams interested in ham satellite
commmunications. So keep up with the good work and congratulations.
Best wishes for you and yours de Guillermo/XE1RGL.
73's
Thanks for the kind words, Guillermo!
This week a letter was received from Joe Ellis, VK4AGL in Australia, along
with a beautiful color photograph of Joe's ham station. Joe asks for
help in obtaining slides or photographs of images taken by Voyager and
Pioneer for an upcoming presentation to the Queensland Digital Group.
My suggestion would be to get in contact with the Jet Propulsion Laboratory,
which is operated for NASA by the California Institute of Technology.
The JPL is responsible for the design of the Deep Space Network which
communicates with lunar, planetary, and interplanetary missions including
the Viking-Mars, Mariner, Voyager, Galileo, and the Venus Orbiting Imaging
Radar (VOIR) projects.
Their mailing address is:
JET PROPULSION LABORATORY
Pasadena, California 91103
U.S.A.
Rick, BY1QH, a junior engineering student and the public relations manager
of the Tsinghua University Amateur Radio Club (TUARC) in Beijing, China,
who is a faithful reader of SpaceNews would like to thank Mr. Ward French,
KB1AJF, who kindly offered OSCAR-related books and suggestions in helping
Rick and the TUARC to become active on Amateur satellites. Rick wishes to
extend his deepest gratitude to Ward and others for their help, and looks
forward to working the world through the OSCAR satellites in the near future.
* THANKS! *
===========
Thanks to all those who sent messages of appreciation regarding SpaceNews,
especially:
BY1QH KB1ZK XE1RGL PA3AYK VK4CNQ VK6XY KA9ITZ
* FEEDBACK/INPUT WELCOMED *
===========================
Mail to SpaceNews should be directed to the editor (John, KD2BD) via any
of the following paths:
FAX :1-908-747-7107
UUCP :...catfish.ocpt.ccur.com!ka2qhd!kd2bd
PACKET :KD2BD @ NN2Z.NJ.USA.NA
INTERNET:kd2bd@ka2qhd.ocpt.ccur.com -or- kd2bd@amsat.org
MAIL:
John A. Magliacane, KD2BD
Department of Engineering and Technology
Advanced Technology Center
Brookdale Community College
Lincroft, New Jersey 07738
U.S.A.
<<=- SpaceNews: The first amateur newsletter read in space! -=>>
/EX