Steven J. Ostro
Encyclopedia
Radar astronomy
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the echoes. This research has been conducted for six decades. Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an...
. He worked at NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
. Ostro led radar observations of numerous asteroids, as well as the moons of Jupiter and Saturn, Saturn's rings, and Mars and its satellites. As of May 2008, Ostro and his collaborators had detected 222 near-Earth asteroids (including 130 potentially hazardous objects and 24 binaries
Binary asteroid
A binary asteroid is a system of two asteroids orbiting their common center of mass, in analogy with binary stars. 243 Ida was the first binary asteroid to be identified when the Galileo spacecraft did a flyby in 1993...
) and 118 main belt objects
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...
with radar. He died December 15, 2008 due to complications related to cancer. He has been remembered fondly by his colleagues for both his personal and professional contributions.
Education and Employment
Dr. Ostro received a B.A. in Art History and a B.S. in Ceramic Science from Rutgers UniversityRutgers University
Rutgers, The State University of New Jersey , is the largest institution for higher education in New Jersey, United States. It was originally chartered as Queen's College in 1766. It is the eighth-oldest college in the United States and one of the nine Colonial colleges founded before the American...
in 1969, a Master's Degree in Engineering Physics from Cornell in 1974, and his PhD in Planetary Science
Planetary science
Planetary science is the scientific study of planets , moons, and planetary systems, in particular those of the Solar System and the processes that form them. It studies objects ranging in size from micrometeoroids to gas giants, aiming to determine their composition, dynamics, formation,...
from MIT in 1978. At MIT, Ostro was advised by Gordon Pettengill
Gordon Pettengill
Gordon Pettengill is a noted American radio astronomer and planetary physicist.-Early life and education:Pettengill was born in Providence, Rhode Island. As a young man he was enthralled with radio and electronics, taking apart and building old radios...
and studied the radar scattering properties of Saturn's rings and the Galilean satellites using the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
.
After completing his graduate work and a year as a postdoc at MIT, Ostro served as an assistant professor of Astronomy at Cornell before moving to JPL in 1984. Ostro headed JPL's Asteroid Radar group, and was a member of the Cassini–Huygens RADAR team, studying the moons of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
.
Asteroid Radar Astronomy
Radar astronomy
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the echoes. This research has been conducted for six decades. Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an...
. In early experiments, such as the first radar detection of Ceres, radar observations of asteroids were restricted to measurements of Doppler shifts and radar cross-sections. Beginning in the early 1980s, Ostro led the development of radar imaging and shape-reconstruction techniques, first determining only outer limits of targets' shapes, then deriving three-dimensional shape models. From August 19 to 22 of 1989, Ostro and Scott Hudson
Scott Hudson
Raymond Scott Hudson is a professor of electrical engineering and computer science at Washington State University. Hudson was educated at Caltech, where he received his bachelor's degree in engineering and applied science in 1985, his master's degree in electrical engineering in 1986, and his PhD...
observed the contact binary 4769 Castalia
4769 Castalia
The asteroid 4769 Castalia was the first asteroid to be modeled by radar imaging. It is an Apollo, Mars- and Venus-crosser asteroid. It was discovered on August 9, 1989, by Eleanor F. Helin on photographic plates taken at Palomar Observatory...
from the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
, producing the first resolved radar images of an asteroid, which they later used to construct a model of the object.
Following the further development of imaging and shape reconstruction techniques by Ostro, Hudson, and Christopher Magri and the upgrade of Arecibo
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
in the mid-1990s, the number of radar observations has increased dramatically.
Asteroid impact hazard
Ostro was an early participant in discussion of the asteroid impact hazard, placing particular emphasis on the need to characterize asteroids before any deflection attempt. In a paper with Carl SaganCarl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...
, Ostro noted that while the asteroid impact hazard is a long-term risk to any civilization, the risk associated with maintaining an active deflection program is higher, because it is just as easy to deflect an asteroid to impact Earth as to prevent it from doing so. Ostro advocated for continued funding of the Arecibo Planetary Radar
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
, on both hazard and scientific grounds.
Notable asteroids observed by Ostro include
- 216 Kleopatra216 Kleopatra216 Kleopatra is a trinary main-belt asteroid that was discovered by Johann Palisa on April 10, 1880, in Pola. It is named after Cleopatra, Queen of Ancient Egypt....
- a large main-belt asteroid, the first asteroid confirmed to have a surface composition of nickel-ironIron meteoriteIron meteorites are meteorites that consist overwhelmingly of nickel-iron alloys. The metal taken from these meteorites is known as meteoric iron and was one of the earliest sources of usable iron available to humans.-Occurrence:...
. - 1986 DA - the first near-Earth asteroid confirmed to be metallic. The estimated amount of platinumPlatinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
-group metals in 1986 DA is comparable to that in the Bushveld Igneous ComplexBushveld igneous complexThe Bushveld Igneous Complex is a large layered igneous intrusion within the Earth's crust which has been tilted and eroded and now outcrops around what appears to be the edge of a great geological basin, the Transvaal Basin. Located in South Africa, the BIC contains some of the richest ore...
, the largest source on Earth's surface. - 4769 Castalia4769 CastaliaThe asteroid 4769 Castalia was the first asteroid to be modeled by radar imaging. It is an Apollo, Mars- and Venus-crosser asteroid. It was discovered on August 9, 1989, by Eleanor F. Helin on photographic plates taken at Palomar Observatory...
- the first near-Earth asteroid imaged well enough to determine its shape, which is two distinct 0.9-km lobes in contact (a contact binary). - 4179 Toutatis4179 Toutatis4179 Toutatis/1989 AC is an Apollo, Alinda, and Mars-crosser asteroid with a chaotic orbit produced by a 3:1 resonance with the planet Jupiter, a 1:4 resonance with the planet Earth, and frequent close approaches to the terrestrial planets...
- a contact binary asteroid that is in a non-principal axis rotation state. - 1998 JM8 - a large near-Earth asteroid that rotates very slowly.
- 1998 KY261998 KY26The asteroid ' was discovered on June 2, 1998, by Spacewatch and observed until June 8, when it passed 800,000 kilometers away from Earth . It is roughly spherical and is only about in diameter...
- a very small (30 m wide) asteroid that spins so quickly that it has negative effective gravity. - 1999 KW4 - one of the first binary near-Earth asteroids known. The shape of the primary (alpha) has been determined by the orbital evolution of the secondary (beta), which is in turn coupled to the system's orbit around the Sun by radiation forceYarkovsky effectThe Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum...
s. - 6489 Golevka6489 Golevka6489 Golevka is an Apollo, Mars-crosser and Alinda asteroid, discovered in 1991 by Eleanor F. Helin.Its name has a complicated origin. In 1995, Golevka was studied simultaneously by three radar observatories across the world: Goldstone in California, Yevpatoria RT-70 radio telescope in Ukraine and...
- the first asteroid for which the Yarkovsky effectYarkovsky effectThe Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum...
(radiation force changing the orbit) was measured.
In these dynamical studies, Ostro worked extensively with Daniel J. Scheeres of the University of Colorado and his students.
- 1950 DA - an approximately 1-km wide asteroid with a possible Earth impact in 2880 (initially studied by Ostro, Jon Giorgini, Lance Benner, and Scott HudsonScott HudsonRaymond Scott Hudson is a professor of electrical engineering and computer science at Washington State University. Hudson was educated at Caltech, where he received his bachelor's degree in engineering and applied science in 1985, his master's degree in electrical engineering in 1986, and his PhD...
). - 99942 Apophis99942 Apophis99942 Apophis is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a small probability that it would strike the Earth in 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on...
- a near-Earth asteroid that will pass within geosynchronous orbitGeosynchronous orbitA geosynchronous orbit is an orbit around the Earth with an orbital period that matches the Earth's sidereal rotation period...
in 2029. Radar astrometryAstrometryAstrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...
from observations by Ostro's group have been essential to predicting Apophis' trajectory.
Radar provides extremely accurate measurement of the positions and velocities of target objects, and such astrometry
Astrometry
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...
of near-Earth objects has been recognized as crucial to dealing with the impact hazard. In many cases, radar astrometry has excluded possible Earth impacts from trajectory predictions years before optical astrometry would have been able to do so.
Work on other objects
Ostro worked on radar observations of the icy satellites of Jupiter and Saturn, particularly with the Cassini-HuygensCassini-Huygens
Cassini–Huygens is a joint NASA/ESA/ASI spacecraft mission studying the planet Saturn and its many natural satellites since 2004. Launched in 1997 after nearly two decades of gestation, it includes a Saturn orbiter and an atmospheric probe/lander for the moon Titan, although it has also returned...
RADAR instrument. Radar observations of Mars' moons, Phobos
Phobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...
and Deimos
Deimos (moon)
Deimos is the smaller and outer of Mars's two moons . It is named after Deimos, a figure representing dread in Greek Mythology. Its systematic designation is '.-Discovery:Deimos was discovered by Asaph Hall, Sr...
, have refined knowledge of their orbits and show that their surfaces are coated with very low density (~1 g/cm3) material, most likely fine-grain dust, to a depth of several meters.
Awards and honors
Ostro received the Gerard P. Kuiper PrizeGerard P. Kuiper Prize
The Gerard P. Kuiper Prize is awarded annually by the Division for Planetary Sciences of the American Astronomical Society for outstanding lifetime achievement in the field of planetary science. The prize is named for Gerard P. Kuiper.Kuiper Prize winners:...
from the Division for Planetary Sciences
Division for Planetary Sciences
The Division for Planetary Sciences is a division within the American Astronomical Society devoted to solar system research. It was founded in 1968. The first organizing committee members were: Edward Anders, L. Branscomb, J. W. Chamberlain, R. Goody, J. S. Hall, A. Kliore, M. B. Elroy, Tobias...
of the American Astronomical Society
American Astronomical Society
The American Astronomical Society is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC...
in 2003.
He was awarded NASA Medals for Exceptional Scientific Achievement in 1991 and 2004, in both cases for his leadership of asteroid radar astronomers as well as his scientific accomplishments.
The asteroid 3169 Ostro
3169 Ostro
3169 Ostro is an inner main-belt asteroid discovered on June 4, 1981 by E. Bowell at Flagstaff . It is named in honor of American astronomer Steven J. Ostro.- External links :*...
is named in his honor.
In 2008, Ostro was elected a Fellow of the American Geophysical Union
American Geophysical Union
The American Geophysical Union is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 135 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international field of geophysics...
, awarded for acknowledged eminence in the Earth and Space sciences.
In 2010, Ostro was posthumously awarded NASA's Distinguished Service Medal
External links
- NASA's Asteroid Radar Group
- Division for Planetary Sciences of the American Astronomical Society: Ostro was the recipient of the 2003 DPS Kuiper Prize