Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/jplpaper/930701.ZIP/930701.UNI

Text File | 1993-08-09 | 18KB | 342 lines

Jet Propulsion Laboratory UNIVERSE
Pasadena, California - Vol. 23, No. 13 - July 1, 1993
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JPL tests Russian-made thrusters

By Karre Marino
     To help foster technological assistance in the private
sector, members of Section 353 are working with the Innovative
Science and Technology office of the Ballistic Missile Defense
Organization, formerly the Strategic Defense Initiative, and Palo
Alto-based Space Systems/Loral in testing performance and
operating life of a Russian-made thruster.
     The Stationary Plasma Thruster (SPT-100), which is
manufactured by Fakel Enterprise in Kaliningrad, is also being
tested at NASA's Lewis Research Center, which will run
performance evaluation and characterization of the exhaust plume.
     Dr. John Brophy, supervisor, Electrical Propulsion & Plasma
Groups, Section 353, explained that the hardware was supplied by
Space Systems/Loral under a JPL Affiliates Program agreement.
"Loral needed a facility to test the thruster, which it intends
to use as a stabilizing device on its communication satellites,"
he explained.
     The thruster essentially ensures that the satellite is in a
"geosynchronous orbit," Brophy said, which means that it stays in
one place. As forces try to move it, the thruster pushes the
satellite back into its orbit.
     It is more difficult to keep the satellite in its
north-south direction, because it contends with a variety of
forces, including the moon and other disturbances; so such effort
at stabilization requires more propulsion capacity, Brophy added.
     Loral representatives believe that the Russian-made thruster
has superior performance over the more widely used arc jet, which
General Electric will employ for north-south stationkeeping on
the Telstar IV communication satellite. Loral is counting on the
thruster to give it a competitive edge. However, Loral understood
that the SPT-100 had not been as well tested as have the arc
jets.
     Tests will take approximately eight months, by which time
the 5-kilogram thruster will have been tested for 5,000 hours --
the length of time, explained Brophy, that is equal to about
10-15 years of thruster operation in orbit. The engines will run
for 50 minutes, be turned off for 20 minutes, and then turned on
again. The "life" test will begin July 1.
     Brophy also pointed out the importance of the thruster's
exhaust velocity (EV), which indicates how fast propellant is
pushed away from the thrusters. "The faster it is pushed away,
the less propellant the spacecraft uses. That's where financial
benefits can be realized. If we can make the spacecraft lighter,
we save money on the launch and use those savings to add
additional transponders, for example."
     He noted that conventional ion engines have an EV of more
than 30,000m/sec., while the SPT-100 has an EV of 16,000m/sec.,
which seems to be the optimum for communication satellites. "The
SPT-100 offers a unique combination of performance and
efficiency. No other propulsion devices produce this combination
of efficiency and impulse," said Brophy.
     Performance test results have been so impressive that a
second thruster, this one with an Anode Layer, called TAL, which
was developed at the Central Research Institute for Machine
Building near Moscow, has been purchased by JPL.
     Speculation is that thrust density, performance and lifetime
characteristics of the device are superior to those of the SPT,
said Brophy. Yet, the purchase by JPL of this model was a
Herculean test of patience, according to Charles Garner, task
manager for Russian Hall thruster testing at JPL.
     Garner had to deal with a limited number of international
phone lines into Moscow, fax machines without paper, and
pre-sunrise phone calls, but he forged ahead and helped ink the
deal. The TAL will also undergo a series of tests at JPL,
beginning in September. ###
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Space Academy graduates honored

By Karre Marino
     The first graduating class from John Muir High School's
Southern California Space Academy was honored in a ceremony June
17 at von Karman Auditorium.
     JPL Director Dr. Edward Stone was joined by Dr. Yvonne
Freeman, Associate Administrator for the Office of Equal
Opportunity Programs at NASA, astronaut Capt. David Walker,
teachers, family and friends in paying tribute to 18 Pasadena
Unified School District (PUSD) students, each of whom received
medallions, certificates and many words of praise.
     All of the speakers cited the importance of giving American
students increased training and preparation in the sciences as a
means to remaining competitive in research and world markets.
     Stone lauded this new approach to education and said he was
"pleased to see such a successful program in our community.
Indeed, JPL is proud to be a partner in the Space Academy, many
of whose students are familiar to us, having spent their summers
here as interns.
     "I am encouraged to see young people interested in science
and engineering, which will ensure we are competitive in the
world markets. We need the skills and innovations of this new
generation."
     He told the students: "You have a head start to becoming
innovators of the future, and this is just the beginning of your
own journey of exploration and discovery."
     Freeman, the former manager of JPL's Minority Science and
Engineering Initiatives Office whose support and leadership were
instrumental in establishing the Academy, said she believed in
the concept from the start, noting that "this is a testimony to
what people can achieve in a collaborative partnership. This
Academy is a national prototype with tremendous replication
potential."
     Adding that "Education is the passport to opportunity and
economic capability," Freeman thanked "the JPL/Caltech mentors,"
eight of whom attended the graduation: D.J. Byrne, Section 339;
Dale Burger, Section 342; Monica Garcia, Section 615; Jennifer
Peden, Section 514; John Reimer, Section 312; Jeanette Mills,
Section 622; and Caltech grad students Danny Howard and Jean
Andino.
     The keynote speaker, Walker, who commanded the shuttle
mission that launched Magellan, described the Space Academy as
"providing opportunities for motivating youngsters to excel in
math and science. I see among you leaders in your community and
your careers. That is why programs like this are crucial; they
give students the proper tools to keep us first in the world.
Hopefully, space academies will spread across the country."
     John Muir principal Gary Talbert paid his respects to the
group, calling the graduation "an important milestone. These
students have fought the good fight and persevered in a time of
great challenge in our community, state and country. We need
folks like you."
     The Space Academy staff -- Ben Aroyan, Shelly McDonald,
Scott Phelps, Chester Robinson and Karen Favor -- was honored
with a glass, engraved plaque presented by the students.
     Of the 50 space academies statewide, John Muir has one of
seven in the PUSD. In addition to JPL/Caltech, Academy partners
are NASA, Pasadena City College and Cal State Los Angeles. ###
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Posner remembered as DSN pioneer,
trusted technology adviser, friend

     Dr. Edward Posner, chief technologist for JPL's
Telecommunications and Data Acquisition Office, died June 15 when
he was hit by a truck while bicycling to work. He was 59.
     Deputy JPL Director Larry Dumas, who worked closely with
Posner when the former was assistant Lab director for the TDA
Office, noted that Posner will be missed by many for his
"towering intellect."
     Dumas said that Posner, who had joined JPL in 1961 and had
served as the TDA Office's chief technologist since 1982, had the
"ability to seek out and address important issues that weren't
being addressed because they didn't fit into the bureaucratic
framework.
     "He was a creative thinker and a warm and caring man," Dumas
added.
     A researcher and mathematician, Posner's specialty was
information and communication theory. His research in coding
theory and data compression at JPL has enabled the volume of data
returned from spacecraft over the Deep Space Network to be
increased by several orders of magnitude.
     Norman Haynes, the current ALD for the TDA Office, said
Posner will be remembered as "one of the original pioneers of the
DSN.
     "Over the last 30 years, Ed was one of the principal voices
of new technology at JPL and in the DSN and always kept us at the
forefront in that area," Haynes added.
     "Everybody enjoyed working with Ed. He did his job with
great wit and wisdom, and he will be sorely missed."
     Bob Stevens, former chief engineer in the TDA Office, knew
Posner for the better part of 30 years and maintained a close
friendship with him away from work.
     Stevens said he, Posner and other colleagues in the
Pasadena/Altadena area would regularly bike to work, "which was a
good opportunity for us to exchange ideas," but Stevens also
noted that Posner enjoyed family cycling trips on weekends with
his friends.
     Even though he retired a couple of years ago, Stevens often
joined Posner in cycling to JPL.
     The sad irony, Stevens said, is that he was on vacation in
Ireland, and another rider was unavailable on the morning of
Posner's death. Riding alone, Posner chose a different route to
come to work that day.
     "I'll miss his excellent sense of humor," Stevens said,
adding that Posner was often "an excruciatingly entertaining
guy."
     Stevens also noted that Posner -- who had worked as a
visiting professor of electrical engineering at Caltech since
1978 -- was instrumental in bringing a number of his
"intellectually outstanding" former Caltech graduate students to
JPL.
     Posner had also been a member of Caltech's Summer
Undergraduate Research Fellowship (SURF) Administrative Committee
since 1990 and co-founded the SURFSAT program at JPL, where
students build a simulated satellite that communicates with the
DSN. He co-sponsored 20 students for the program from 1988-91.
     "Ed's extensive background in the DSN was instrumental in
finding the right students for the SURF and SURFSAT programs,"
said Robert Clauss, a member of the technical staff in Section
336 and the co-founder of SURFSAT.
     "He was a real delight to work with," Clauss said, adding
that Posner will also be remembered as "a champion for students'
work and their causes."
     Posner was one of the founders of research into neural
networks -- computers loosely modeled after biological brains --
at Caltech and JPL in the early 1980s and was instrumental in the
creation of Caltech's interdisciplinary graduate-study program in
Computation and Neural Systems, the first program of its kind in
the world.
     A co-founder of the JPL Toastmasters Club, Posner was a
charter member of the Planetary Society, a member of the American
Institute of Aeronautics and Astronautics, the World Space
Foundation and many other professional organizations. He also was
on the editorial boards of several scientific and engineering
journals.
     He is survived by his wife, Sylvia, daughter Joyce and son
Steven.
     Services were held June 19 at Mountain View Cemetery in
Pasadena.
     Donations in Posner's name can be made to the SURF program
at JPL, mail stop 291-105, ext. 4-3750. ###
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News briefs

     Esker K. "Ek" Davis, manager of the Institutional Computing
and Missions Operation Division 370, has been promoted to Major
General in the U.S. Air Force Ready Reserve.
     He was awarded the promotion in March and was honored for
the achievement June 18 in Caltech's Athenaeum.
     As an officer in the Air Force from 1958-66, Davis served in
various positions supporting NASA's early space program,
including the Ranger, Surveyor and Lunar Orbiter series.
     Davis, who began his career at JPL in 1967, has held various
engineering and management positions on the Mariner Mars, Mariner
Venus-Mercury and Voyager missions. He was the Voyager project
manager during the Voyager 2 flyby of Saturn in 1981. He has held
his current position since 1985.
     In his Air Force Reserve assignment, Davis serves as
director of the North American Aerospace Defense Command-U.S.
Space Command Joint Aerospace Reserve Program, which is made up
of reservists from all branches of the military.

     The Uncooled Infrared Tunnel Sensor, produced by the Center
for Space Microelectronics Technology in Section 346, has been
recognized as one of the 100 most technologically significant
products of 1992 by R&D magazine.
     The sensor, manufactured entirely by silicon micromachining
techniques, allows the development of state-of-the-art infrared
sensors which may be manufactured at very low cost, and are
compatible with integration of electronics and development of
imaging rays.
     Technical Group Leader Dr. Thomas Kenny said applications
for the sensor, which is available for license from JPL/Caltech,
include NASA missions requiring infrared imaging of planetary
bodies from an orbiting platform. The device could also provide
benefits in the medical, industrial and security fields, he said.
     Kenny, along with team members Dr. William Kaiser, Judi
Podosek and  Erika Vote, will be honored at an awards banquet at
Chicago's Museum of Science and Industry in September.

     Free tuberculosis skin testing will be available to JPL
employees Aug. 23-24, according to Lori James of the Medical
Services Office.
     Kaiser Permanente Worksite Wellness Staff will be on Lab
both days from 10 a.m.-4 p.m. Forty-eight to 72 hours after the
skin test, a return visit to Medical Services will be required to
have the test read. If the skin test is positive, employees will
be referred to their health care provider, who will advise them
of the necessary course of action.
     James said that Medical Services hopes to screen 400-500
people during the two-day period.
     The deadline to sign up for the five-minute test is Aug. 6.
Call Medical Services at ext. 4-5727 for an appointment. ###
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TOPEX/Poseidon data produce most
accurate sea level measurements to date

By Mary Hardin
     During the first six months of their mission, scientists
using the U.S.-French TOPEX/Poseidon oceanographic satellite have
recorded the most accurate measurements to date of global sea
level changes.
     The data will be used by oceanographers to calibrate the
computer models that help forecast future climate changes.
     "The changes in sea level we have observed during the first
six months from October 1992 to March 1993 are a combination of
the effects of seasonal warming and cooling as well as wind,"
said project scientist Lee-Lueng Fu of the Atmospheric and
Oceanographic Sciences Section 322.
     In the Northern Hemisphere, the sea level in the Gulf Stream
off the U.S. East Coast and the sea level in the Kuroshio regions
east of Japan dropped by more than 30 centimeters (12 inches).
Most of this drop was caused by the winter cooling of the ocean
by the cold continental air mass blown off the North American and
Asian continents, Fu said.
     In the Southern Hemisphere, a corresponding sea level rise
occurred at similar latitudes, which resulted from the warming of
the summer atmosphere.
     "It takes an increase or decrease of 1 degree Celsius in the
average temperature of a water column of 50 meters deep to cause
the sea level to rise or fall by 1 centimeter," Fu explained.
     The sea level change in the Northern Hemisphere is larger
than that in the Southern Hemisphere,  because the larger land
mass of the Northern Hemisphere creates a colder continental air
mass that cools the ocean water off the east coasts of North
America and Asia.
     Seasonal changes in the trade winds caused a drop in sea
level at the equator in both the Pacific and Atlantic oceans, Fu
said. The rise in sea level in the eastern tropical Pacific Ocean
off the coast of South America was the remnant of the Kelvin wave
pulses that began in December 1992. A Kelvin wave pulse creates a
surge of warm water that moves eastward along the equator and can
contribute to El Nino conditions.
     In the Indian Ocean, seasonal monsoon winds caused a fall in
sea level in the eastern and southern regions and a rise in sea
level in the northwestern region. ###
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Halley Watch holds final meeting

     The International Halley Watch (IHW), a global observing
program coordinated at JPL and sponsored by NASA since 1980, held
a final meeting at the Lab last month to signal completion of the
IHW archive of Halley's Comet pictures and other data.
     The collection, occupying 24 CD-ROMs (equivalent to many
thousands of pages if printed), contains data from more than
1,000 professional and amateur observers from around the world.
Three more CDs containing spacecraft data, and picking up later
observations, are in preparation.
     The meeting, chaired by IHW Leader Ray Newburn of JPL's
Atmospheric and Oceanographic and Cometary Sciences Section 324,
produced demonstrations of the archive's data and heard accounts
of research already emerging from it.
     Attendees from JPL included Mikael Aronsson, Section 361;
Dr. Paul Chodas, Section 314; Stephen Edberg, 324; Dr. Michael
Keesey, Section 314; Charles Morris, Section 334; Dr. Zdenek
Sekanina, Section 324 and Dr. Donald Yeomans, Section 314.
     Also attending were Cornell University's Dr. Joe Veverka,
who is a member of the Galileo imaging team; Dan Klinglesmith of
NASA's Goddard Space Flight Center and other scientists and
astronomers from universities throughout the United States. ###

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